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1
Liu, Wei Zheng, Jun Hui Zhang i Hao Zhang. "Analysis on Pile-Soil Stress Ratio of Composite Foundation with Sparse Capped-Piles under Lime-Soil Embankment Load". Applied Mechanics and Materials 501-504 (styczeń 2014): 124–31. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.124.
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The combined effect of the embankment fill, piles and caps, and foundation soils on the load transfer characteristics of sparse capped-piled embankment is very significant. Using the modified cylindrical shear stress transfer model based on Marston soil pressure theory, a new calculation method for pile-soil stress ratio of sparse rigid pile composite foundation incorporating the arching effect in lime-soil and soil-pile interaction was presented. The presented method is verified by comparison between analytical solutions and the observed results from a practical project. In addition, a parametric study was also conducted to evaluate the influence of the embankment height, the cohesion of fill and pile-soil stiffness ratio on the pile-soil stress ratio.
2
Fellenius, Bengt H. "Results from long-term measurement in piles of drag load and downdrag". Canadian Geotechnical Journal 43, nr 4 (1.04.2006): 409–30. http://dx.doi.org/10.1139/t06-009.
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Several full-scale, long-term tests on instrumented piles performed since the 1960s and through the 1990s are presented. The results of the tests show that a large drag load will develop in piles installed in soft and loose soils. The test cases are from Norway, Sweden, Japan, Canada, Australia, United States, and Singapore and involve driven steel piles and precast concrete piles. The test results show that the transfer of load from the soil to the pile through negative skin friction, and from the pile back to the soil through positive shaft resistance, is governed by effective stress and that already a very small movement will result in mobilization of ultimate values of shaft shear. The pile toe resistance, on the other hand, is determined by downdrag of the pile and the resulting pile toe penetration. Reconsolidation after the pile installation with associated dissipation of pore pressures will result in significant drag load. An equilibrium of force in the pile will develop, where the sustained loads on the pile head and the drag load are equal to the positive shaft resistance plus the pile toe resistance. The location of the force equilibrium, the neutral plane, is also where the pile and the soil move equally. The drag load is of importance mostly for very long piles (longer than 100 pile diameters) for which the pile structural strength could be exceeded. Downdrag, i.e., settlement of the piled foundation, is a very important issue, however, particularly for low-capacity short piles. Soil settlement at the neutral plane will result in a downdrag of the pile. The magnitude of the downdrag will determine the magnitude of the pile toe penetration into the soil, which will determine the pile toe resistance and affect the location of the neutral plane. Nature's iteration of force and soil settlement will decide the final location of the neutral plane.Key words: piles, negative skin friction, drag load, downdrag, neutral plane, pile settlement.
3
Zhang, Hao, Ming Lei Shi, Rui Kun Zhang i Yu Zhao. "Load Transfer Mechanism of Embankment Supported by Sparse Piles". Applied Mechanics and Materials 178-181 (maj 2012): 1396–401. http://dx.doi.org/10.4028/www.scientific.net/amm.178-181.1396.
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The load transfer property of embankment fills, cushion, pile (or with cap) and foundation soils are complicated in a piled embankment. In this paper, the vertical load effects of pile and foundation soils at the bottom of embankment were analyzed with consideration of the interaction of each component. The arching effect of embankment fills and the pile-soil interaction were respectively formulated, and then, with continuous displacements and stresses at the bottom of embankment, a calculation method of pile-soil stress ratio was presented. In addition, the influence of the setting of cushion and geosynthetic was analyzed. The present method could definite the load sharing between pile and soil, and may be applied in the engineering design of embankment supported by spares piles.
4
Zhao, Min, i Wei Ping Cao. "A Numerical Analysis of Soil Arching in Piled Embankments". Advanced Materials Research 468-471 (luty 2012): 638–42. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.638.
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Soil arching has important influence on the behavior of piled embankments. How to calculate stress concentration ratio is of great concern when designing embankment over soft soils reinforced by rigid concrete piles. A numerical analysis by using a commercial FEM program was conducted to reveal the mechanism of soil arching in piled embankments. And also, the influence of embankment height, pile-soil relative displacement, cohesion and internal friction angle on the equal settlement plane was evaluated. The results indicate that the stress concentration ratio varies with the pile-subsoil relative displacement and has upper and lower bound value. The effect of pile-soil displacement and the strength parameters of embankment material on the equal settlement plane can be neglected. It was also found that the equal settlement plane height is equal to 1.6 times the pile-cap clear spacing. When the ratio of embankment height to the pile-cap clear spacing is greater than 1.6, no apparent differential settlement will occur on the embankment surface.
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Wang, Kangyu, Jun Cao, Xinquan Wang i Yingjie Ning. "Soil Arching of Piled Embankment in Equal Settlement Pattern: A Discrete Element Analysis". Symmetry 13, nr 9 (3.09.2021): 1627. http://dx.doi.org/10.3390/sym13091627.
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Soil arching, which occurs in the piled embankments, plays an important role in stress redistribution between the relatively soft subsoil and the stiffer piles. The formation of the soil arching depends on the differential settlement of the embankment fill above the pile and the subsoil. The soil arching effect is barely investigated in the literature from the perspective of differential settlement of piles and soils. Based on the discrete element method (DEM), this paper develops a classic trapdoor test model to investigate the differential settlement in piled embankment during the downward movement of the trapdoor, and to explore the formation mechanism of soil arching in equal settlement pattern by changing the width of the pile cap and the height of the embankment. Due to symmetry, only one section of the laboratory test model is simulated herein. It was found that the soil arching formed under the equal settlement pattern remained unchanged after a certain degree of development, and the height of the equal settlement did not change at 0.7(s-a), where s is the pile spacing, and a is the width of the pile cap. The height of the embankment (H) and the width of the pile cap (a) have a significant influence on the formation of the equal settlement pattern when the width of the trapdoor is kept constant. Both the decrease in “H” and the increase in “a” facilitate the differential settlement of the soil between the piles and the pile-soil, enabling the slip surface to develop upward gradually, thereby hindering the formation of the equal settlement pattern.
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Hartono, Edi. "Analisis Lendutan Model Pelat Fleksibel dengan Tiang Perbesaran Ujung dan Pelat Tidak Rapat Tanah Pada Tanah Pasir". Semesta Teknika 17, nr 1 (25.11.2015): 10–16. http://dx.doi.org/10.18196/st.v17i1.410.
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Problems in sandy soil may occur when sand has low density, uniform gradation and thick deposit. Flexible plate foundation may used in this condition but plate deflection still high. To reduce deflection and to improve soil density, piles were used to support the plate. Installing piles made foundation system stiffer. The objectives of this study are to studies about behavior of plates and plate with pile on sandy soil. Plate deflection was observed with variation of plate thickness, bottom pile enlargement, and soil-plate-pile interaction (free standing pile and piled foundation). 1,2 x 1,2 x 1,2 m box container filled with sandy soil was used as soil media. Square and rectangular plexiglass plate were used to modelled plate. Steel pipe with 2,5 cm in diameter were used as pile model. The behavior of the plates were observed under loading (point load). The results shows that plate deflections were affected on plate thickness, bottom pile enlargement and soil-plate-pile interaction. For a ticker plate, contact surface between plate and soil was wider. For the 40 cm x 10 cm plates with base pile enlargement, deflections were found to reduced up to 21,26%. The ‘piled foundation’ on 40 cm x 10 cm plates, (installing with 20 cm pile length, and 10 cm spacing between pile), deflections were reduced 83,63% compared with free standing foundation.
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Jamil, Irfan, Irshad Ahmad, Wali Ullah, Mahmood Ahmad, Mohanad Muayad Sabri Sabri i Ali Majdi. "Experimental Study on Lateral and Vertical Capacity of Piled Raft and Pile Group System in Sandy Soil". Applied Sciences 12, nr 17 (2.09.2022): 8853. http://dx.doi.org/10.3390/app12178853.
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In deep foundations, the pile group and the pile raft are generally used. To date, the contribution of the raft is not taken into account in the design, even when the raft is in contact with the soil and the whole system is therefore considered to work as a pile group foundation. In a combined pile raft system, the raft takes a considerable portion of the applied load, depending upon the number of piles, the spacing to diameter ratio of the piles, and the length to diameter ratio. In this paper, an experimental investigation is carried out to study the response of small-scale pile group and piled raft models with a varying number of piles subjected to both vertical and lateral loads. Additionally, the response mechanism of these models to both types of loads is also studied. A comparison was made between these models. It was found that, unlike the pile group, the piled raft provides considerably high stiffness to both types of loads, and the difference between the stiffness of both systems decreases as the number of piles increases. By comparing the response of the piled raft and the pile group with the same number of piles under the same vertical and lateral load, it was concluded that the piled raft response to the lateral and vertical loads was much stiffer than the pile group response. The lateral deflection and the vertical settlement of the piled raft were less than those of the pile group with the same pile configuration. This effective response of the piled raft to the vertical and lateral loads was due to the raft contribution in resisting the vertical and lateral loads. Moreover, with the increase in the number of piles, the vertical and lateral contribution of the raft decreases.
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Wu, Lijun. "Performance of Geosynthetic-Reinforced and Cement-Fly Ash-Gravel Pile-Supported Embankments over Completely Decomposed Granite Soil: A Case Study". Advances in Materials Science and Engineering 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/2659628.
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This paper presents a full-scale test of the high-speed railway embankment to investigate the performance of cement-fly ash-gravel (CFG) pile-supported embankments over completely decomposed granite (CDG) soils. The authors compared the embankments built on CDG soils reinforced by geogrid only and geogrid and CFG piles in terms of ground settlement, layer settlement, and pile efficacy. Experimental results show that the CFG pile-supported embankment built on CDG soils performs well. The soil arching of CFG piled reinforcement is effective and significantly increases with surrounding soil consolidation. Furthermore, the increase in the soil arching effect is heavily dependent on differential settlements between surrounding soils and piles. Five methods widely adopted in current designing were used to calculate the pile efficacy. The prediction for pile efficacy by the Nordic method, BS8006, and its modified version is significantly higher than measured values. By contrast, the calculation by the EBGEO and CA model method is more approximate to the measured results in both the pattern and the value at the end of construction. Therefore, the adaptability of the EBGEO and CA model method outperformed that of the Nordic method, BS8006, and its modified version. Finally, in this case, the CA model method was recommended to estimate the pile efficacy of CFG pile-supported embankments built on CDG soils.
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Liu, Qiu Sheng, i Dong Feng Liu. "Study on Embedded Pile Length in Slope Reinforced". Applied Mechanics and Materials 105-107 (wrzesień 2011): 1497–504. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1497.
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The embedded length of anti-slide piles reinforcing slopes is analyzed by three-dimensional elasto-plastic shear strength reduction finite difference method. The effect of embedded pile length on safety factor and pile behavior, and the effects of the pile spacing, pile head conditions, bending stiffness and soil style on pile length and pile behavior are analyzed. The results show that the pile spacing and the pile head conditions have significant influence on the critical pile length. The critical pile length is seen to increase with decreasing pile spacing, and smaller pile spacing tends to increase the integrity of the piled slopes. A theoretical analysis of the slip surface is also described, and the slip surface determined by the pressure on piles considering the influences of both soil and the piles of slopes is in agreement with previous researches.
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Cao, Wei Ping, Min Zhao i Qi Chao Shi. "A Numerical Analysis on the Behavior of End-Bearing Pile for Supporting Embankment over Soft Soils". Advanced Materials Research 378-379 (październik 2011): 502–6. http://dx.doi.org/10.4028/www.scientific.net/amr.378-379.502.
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Piled embankments are increasingly used to construct highways on soft soils. End-bearing piles for supporting embankment exhibit different characteristics for the soil arch developed within the embankments. A numerical analysis was conducted to evaluate the soil stress concentration ratio, pile and soil settlements, pile axial force, negative skin friction (NSF) and location of the neutral plane (NP) during embankment filling and consolidation of soft soils. The results indicate that the stress concentration ratio varies with time and most of the embankment load is born by the pile. The soil pressure on the soft soils increase and reach a maximum value during the filling, then decrease gradually and maintain nearly a constant value at the end of the consolidation. The settlement of shallow soft soils differs significantly from that of the deep soft soils. The location of the NP shows a complicated variation.
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Xie, Yunfei, i Shichun Chi. "Optimization Method for Irregular Piled Raft Foundation on Layered Soil Media". Advances in Civil Engineering 2019 (20.05.2019): 1–15. http://dx.doi.org/10.1155/2019/5713492.
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Important buildings such as nuclear power plants always require stricter control of differential settlement than ordinary buildings. Therefore, it is necessary to provide an optimized design for the piled raft foundations of important buildings. In this paper, a new optimization method (using different pile diameters and different pile spacing) was proposed for the design of piled raft foundations. This method adjusts the pile diameters and pile spacing according to the stress distribution at the pile top of the initial design to achieve a more uniform settlement of the raft and stress distribution on top of piles, which can solve the differential settlement problems caused by uneven loads of the superstructure. After optimized design, the differential settlement and integral bending moment of the raft decreased more than 64% and 52%, respectively, and the differential stress on top of piles decreased by at least 63%. The new method proposed in this paper could be applied to large-scale piled raft foundations with complex superstructure loads.
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Alhassani, Athraa Mohammed Jawad, i Ala Nasir Aljorany. "Parametric Study on Unconnected Piled Raft Foundation Using Numerical Modelling". Journal of Engineering 26, nr 5 (1.05.2020): 156–71. http://dx.doi.org/10.31026/j.eng.2020.05.11.
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Piled raft is commonly used as foundation for high rise buildings. The design concept of piled raft foundation is to minimize the number of piles, and to utilize the entire bearing capacity. High axial stresses are therefore, concentrated at the region of connection between the piles and raft. Recently, an alternative technique is proposed to disconnect the piles from the raft in a so called unconnected piled raft (UCPR) foundation, in which a compacted soil layer (cushion) beneath the raft, is usually introduced. The piles of the new system are considered as reinforcement members for the subsoil rather than as structural members. In the current study, the behavior of unconnected piled rafts systems has been studied numerically by means of 3D Finite Element analysis via ABAQUS software. The numerical analysis was carried out to investigate the effect of thickness and stiffness of the cushion, pile length, stiffness of foundation soil, and stiffness of bearing soil on the performance of the unconnected piled raft. The results indicate that when unconnected piles are used, the axial stress along the pile is significantly reduced e.g. the axial stress at head of unconnected pile is decreased by 37.8% compared with that related to connected pile. It is also found that the stiffness and thickness of the cushion, and stiffness of foundation soil have considerable role on reduction the settlement.
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Qiao, Shifan, Changrui Dong, Guyang Li, Hao Zhou i Gang Wang. "Modified Interaction Method for Response of Group Piles Considering Pile–Soil Slip". Mathematics 10, nr 15 (26.07.2022): 2616. http://dx.doi.org/10.3390/math10152616.
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The existing model for calculating the settlements of group piles is based on the principle of superposition, which fails to calculate the interaction between piles more comprehensively and to take into consideration the influence of slip between pile and soil. In this paper, the interaction between group piles is analyzed from a novel perspective. It is assumed that the interaction between piles is a dynamic equilibrium process, i.e., additional shear forces and additional displacements are continuously transferred between piles until a state of equilibrium is reached. On this basis, we propose a new model for calculating the settlements of group piles considering pile–soil slip. First, a calculation method for pile–side resistance is developed considering the influence of slip. Based on experience with the pile–soil interface, pile–side soils can be categorized as near–pile soil and far–pile soil, and different load–transfer models are applied to describe their mechanical states. By equating pile–side soils into a nonlinear spring and connecting them in series to determine the overall equivalent stiffness considering the effect of pile–soil slip, the pile–side resistance under different loading conditions can be accurately determined. Secondly, equilibrium analysis of the pile unit is carried out when the equilibrium condition is reached, and the stiffness matrix for load transfer is derived. Therefore, in this paper, the interaction between piles is concentrated in this matrix, which makes the proposed model for pile settlement calculation clearer and more concise. Compared with measured data, the proposed method can capture the main features of the load–settlement behavior of group piles.
14
Yu, Yiliang, Xiaohua Bao, Zhipeng Liu i Xiangsheng Chen. "Dynamic Response of a Four-Pile Group Foundation in Liquefiable Soil Considering Nonlinear Soil-Pile Interaction". Journal of Marine Science and Engineering 10, nr 8 (26.07.2022): 1026. http://dx.doi.org/10.3390/jmse10081026.
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Piles, which are always exposed to dynamic loads, are widely used in offshore structures. The dynamic response of the pile-soil-superstructure system in liquefiable soils is complicated, and the interaction between the pile and soil and the pile volume effect are the key influencing factors. In this study, a water-soil fully coupled dynamic finite element-finite difference (FE-FD) method was used to numerically simulate the centrifuge shaking table (CST) test of a four-pile group in saturated sand soil. An interface contact model was proposed to simulate the pile-soil interaction, and a solid element was used to consider the volume effect of the pile. The acceleration responses of the soil and pile, settlement deformation, excess pore water pressure, and bending moment were examined. The results show that the bending moment response of the two piles parallel to the shaking direction show minor differences, while the two piles perpendicular to the shaking direction show almost the same distribution. The values of excess pore water pressure at the same depth but different azimuth angles around the pile are also different. The numerical simulation can accurately reproduce soil deformation and pile internal force during and after dynamic loading.
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Chen, R. P., Y. M. Chen, J. Han i Z. Z. Xu. "A theoretical solution for pile-supported embankments on soft soils under one-dimensional compression". Canadian Geotechnical Journal 45, nr 5 (maj 2008): 611–23. http://dx.doi.org/10.1139/t08-003.
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Pile-supported embankments are increasingly being used for highways, railways, storage tanks, etc. over soft soil because of their effectiveness in accelerating construction and minimizing deformation. The stress transfer mechanisms among all of the components in a piled embankment, including the embankment fill, the piles and (or) caps, and the foundation soils, are complicated. In this study, a closed-form solution for one-dimensional loading was obtained taking into consideration the soil arching in the embankment fill, the negative skin friction along the pile shaft, and the settlement of the foundation soil. In the derivations, the piles, the embankment fill, and the foundation soil were assumed to deform one-dimensionally. This study investigated the stress concentration on top of the pile, the axial load and skin friction distributions along the pile, and the settlement of the embankment. Comparisons demonstrate that the results from this solution are in good agreement with those obtained using a finite element method. It is worth pointing out that this solution should be applied to the piles close to the centerline of the embankment and not to those near the toe of the embankment because of the two-dimensional loading condition near the toe.
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Yang, Qingnian, Jianli Shao, Zhijun Xu i Yu Miao. "Experimental Investigation of the Impact of Necking Position on Pile Capacity Assisted with Transparent Soil Technology". Advances in Civil Engineering 2022 (7.02.2022): 1–10. http://dx.doi.org/10.1155/2022/9965974.
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Necking in different positions of a pile body has a significant influence on the bearing performance of a single pile. The transparent soil model experiment was adopted to investigate the impacts of necking positions on the vertical bearing capacity of a single pile and the soil deformation around the pile, and subsequently, the causes of the variation of bearing capacity were analyzed. The results show that the existence of necking does not change the bearing behavior of single pile as pile friction resistance. The bearing capacity of piles decreased by 8.21% and increased by 7.30% when the necking is located in the shallow and middle pile body, respectively, while it did not change significantly when the defects were in the deep part of the pile. The necking position has a significant effect on the deformation and deformation range of soil. The soils at the top, side, and near the end of a pile were mainly influenced by shallow necking, middle necking, and deep necking, respectively. The soils at the location of necking had apparent settlement phenomenon as the piles subsided. The soils at shallow necking’s locations were relatively loose, which reduced the side friction force of piles and finally resulted in a reduction of bearing capacity of a single pile. With the increase of the load, the soil around piles gradually developed penetration phenomenon (large deformation), while the soil at the end of pile moved up against pile settlement, which made the necking soil in the middle denser. The loss of side friction resistance was less than the resistance from the necking, which gave birth to an increase in the bearing capacity of a single pile. It was finally found that the side friction resistance and the resistance caused by necking were the main factors governing the bearing capacity of necking single piles.
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Ahmed, Danish, Siti Noor Linda Bt Taib, Tahar Ayadat i Alsidqi Hasan. "Numerical Analysis of the Carrying Capacity of a Piled Raft Foundation in Soft Clayey Soils". Civil Engineering Journal 8, nr 4 (1.04.2022): 622–36. http://dx.doi.org/10.28991/cej-2022-08-04-01.
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Piled raft foundations are a common type of foundation for high-rise buildings. Unlike shallow foundations, deep foundations (piles) pass through weak or soft soil deposits and can reach stiff soil or bedrock to support the weight of the structure. In this paper, the performance of a medium embedment depth piled raft foundation in soft soil is presented. A numerical model was developed and a parametric study was conducted in order to simulate the case of such a foundation system and to investigate its performance in soft clay. This parametric study investigated the effect of the geometry of a piled raft foundation and the stiffness ratio between the pile material and clay on the performance of the foundation system in soft soil. Additionally, the failure mechanism of such a foundation system under load was examined. An analytical model was developed to predict the ultimate carrying capacity based on the observed failure mechanism. A semi-empirical model is proposed for determining the Improvement Factor (IF) of a given soil, pile, and geometric condition. Findings of the study indicate that the performance of piled raft foundations on soft soils is significantly affected by the piles’ spacing. As the ratio S/D increases, the ultimate carrying capacity of a piled raft foundation decreases. However, when this ratio exceeds 10 (S/D> 10), piles have little or no effect on the ultimate carrying capacity of this foundation system. A piled raft foundation system fails by bearing at the base of the piles and also by shear at the side of the pile group on hyperbolic plans. Doi: 10.28991/CEJ-2022-08-04-01 Full Text: PDF
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Utkin, Vladimir S. "Reliability analysis of an end-bearing pile with account for friction forces on the pile surface". Stroitel stvo nauka i obrazovanie [Construction Science and Education], nr 1 (31.03.2020): 2. http://dx.doi.org/10.22227/2305-5502.2020.1.2.
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Introduction. The behavior of end-bearing piles in the foundation soil and the methodology for their reliability analysis, treated as operational safety measures applicable to a separate bearing element of a pile foundation, need clarification and further development. The weakness of the established reliability analysis methodology, focused on the bearing capacity of the foundation soil, is its failure to take account of each case of the soil behavior above rock or low compressibility soils pursuant to Construction rules and regulations 24.13330.2011. Taking account of the bearing capacity of this soil layer in respect of the load accommodation by an end-bearing pile (taking account of the pile weight) may improve its reliability by the criterion of the bearing capacity in combination with the soil behavior below the bottom tip of a pile. Nizhne-Suyanskiy Waterworks Facility had the mission to solve water household, energy and socio-economic problems. Materials and methods. The author analyzed piles made of any applicable materials; their reliability analysis methods are based on the possibility theory due to the limited amount of statistical information on controllable parameters to be entered into the limit state design model to verify the bearing capacity of the foundation soil. Results. The author presents the design formula to identify the parameters ensuring reliable failure-free behavior of an end-bearing pile in the foundation soil and in respect of the soil bearing capacity. The pile reliability analysis performed in respect of its bearing capacity (and focused on the strength of the pile material) is provided in the references section. The author uses two performance criteria to analyze the reliability of an end-bearing pile, given that an end-bearing pile is analyzed as a consistent mechanical system in terms of the reliability theory. Conclusions. The author has developed a methodology used to analyze the reliability of end-bearing piles. It is focused on the bearing capacity of the foundation soil below the bottom tip of a pile and along its length with a view to the quantitative assessment of its safe performance at the stage of design of a facility that has a piled footing; the groundwork has been laid for further research into the behavior of end-bearing piles and for the development of design regulations applicable to various types of piles that may differ in material, behavior, sinking techniques, etc.
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Lin, Chengyuan, Ruyi Wang, Mengshuang Huang, Lebin Huang i Qinwen Tan. "Study on Disturbance Mechanism of Squeezed and Non-Squeezed Soil Piles on Soft Soil Foundation". Applied Sciences 13, nr 13 (30.06.2023): 7757. http://dx.doi.org/10.3390/app13137757.
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The construction process of pile foundations can significantly disrupt the soil. Therefore, it is necessary to limit the degree of soil disturbance caused by pile foundation construction to an acceptable level. This paper examines the disturbance effects of pile driving on soft soil foundations, specifically analyzing the squeezing effect of squeezed soil piles and the unloading effect of non-squeezed soil piles. To investigate these effects, two typical squeezed soil piles, a hydrostatic pile, and a bag grouting pile, as well as a typical non-squeezed soil pile (a bored pile) are selected. Specifically, a novel construction method for numerical models, which simulates the mechanical processes of different pile types under standard grids, is proposed. Three crucial indicators—soil displacement field, stress field, and disturbance influence range—are chosen to compare the disturbance effects of three types of piles on the soil. Results indicate that the two types of squeezed soil piles cause significant disturbance to the soil displacement field, especially in the horizontal direction, while causing a relatively slight disturbance to the soil stress field. Among the two of them, the disturbance magnitude and range of the hydrostatic pile are greater than those of the bag grouting pile. For the non-squeezed soil pile, the soil displacement field changes minimally and the stress field remains basically unchanged during the pile driving process of the bored pile. To compare and quantify the disturbance effects of three types of piles on soil, the soil disturbance range in the horizontal direction of each pile is normalized by its radius. Results indicate that the horizontal disturbance values of maximum horizontal stress for all three types of piles are approximately 1/5 of the pile length above the pile tip, with normalized values of 7.6, 5.5, and 3.5, respectively. The maximum horizontal deformation disturbance range in the horizontal direction occurs near the ground surface and has normalized values of 15.2, 7.5, and 1.1 for the three types of piles, respectively. Therefore, the hydrostatic pile has the greatest disturbance effect, followed by the bag grouting pile and the bored pile. However, within the allowable range of disturbance in practical engineering, the optimal piling method can be selected by comprehensively considering factors such as the construction difficulty and economic costs.
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Ahmed, Danish, Siti Noor Linda Bt Taib, Tahar Ayadat i Alsidqi Hasan. "A Review on the Behaviour of Combined Stone Columns and Pile Foundations in Soft Soils when Placed under Rigid Raft Foundation". ASM Science Journal 16 (15.07.2021): 1–8. http://dx.doi.org/10.32802/asmscj.2021.709.
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In the last few decades, it has been observed that raft foundations are very commonly used as a foundation solution for moderate to high rise structures either by resting on stone columns or on piles in soft soils. It is believed that, combining stone columns and piles in one foundation system is the more suitable foundation for medium rise structures. The combined foundation system provides a superior and more economical alternative to pile, and a more attractive alternative to stone columns in respect to ground improvement. This paper presents the review of existing studies reported in the literature in the last two decades about the behaviour of stone columns under raft foundations and piled raft foundation in soft soil, notably the failure mechanism and the bearing capacity. Also, a limited work from the literature concerning the performance of combined (pile/stone columns) foundation system in soft soil is comprised. Furthermore, very extensive ongoing research work regarding the investigation and study on the performance of combined (pile/stone columns) foundation system in soft soils is discussed. The main goals and methodology to study the performance of the combined (pile/stone columns) foundation systems in soft soil are also addressed.
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Shakirov, Ildus. "Bearing capacity of piles in a reinforced by pressure cementation soil massif". E3S Web of Conferences 274 (2021): 03023. http://dx.doi.org/10.1051/e3sconf/202127403023.
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Studies of the piles bearing capacity after strengthening soil by cement mortar pressure injection were carried out to determine pile foundations bearing capacity increasing patterns in a result of soils cementation. Depending from the volume and cement mortar technological injection parameters, the soil stress state around the pile changes, additional pile-soil compression occurs and the friction along the lateral surface increase, as well as the soil resistance under the pile bottom end. Cementation effect on the pile bearing capacity for different injectors location and the number of piles in the foundation were determined by tests. The research results can be used in the pile foundations reinforcement design in conditions of reconstruction with increasing loads on the foundations.
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Elsawwaf, Mostafa, Marwan Shahien, Ahmed Nasr i Alaaeldin Magdy. "The behavior of piled rafts in soft clay: Numerical investigation". Journal of the Mechanical Behavior of Materials 31, nr 1 (1.01.2022): 426–34. http://dx.doi.org/10.1515/jmbm-2022-0050.
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Abstract This research aims to investigate the applicability and performance of piled rafts in soft clay. This aim has been achieved by studying how the pile length, pile number, raft-soil relative stiffness, and presence of a sand cushion beneath the raft would affect piled raft settlement, differential settlement, and load sharing. Piled rafts have been numerically simulated using PLAXIS 3D software. Experimental testing results were used to verify the numerical simulation. The portion of the load carried by the piles to the total applied load was represented by the load sharing ratio (GPR). The results indicated that with increasing pile length and number, settlement and differential settlement decreased. It was also noticed that with increasing raft-soil relative stiffness, the differential settlement decreased. The GPR decreased with increasing thickness and relative density of the sand cushion, whereas it increased with increasing pile length and number. This increase in GPR was 13.7, 36, and 58% with an increase in pile length to diameter ratio from 10 to 30 for the number of piles 4, 9, and 16, respectively. Additionally, the raft-soil relative stiffness was observed to have a marginal effect on the GPR.
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Cao, Wei Ping, i Min Zhao. "Performance of Floating Piles for Supporting Embankments in Soft Soils". Applied Mechanics and Materials 105-107 (wrzesień 2011): 1433–37. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1433.
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Reinforced concrete piles are often used to support highway embankments in soft soils. The performance of floating piles differs significantly from that of end-bearing piles. A numerical analysis was conducted to investigate the soil stress concentration ratio, pile and soil settlements, pile axial force, negative skin friction (NSF) and the location of the neutral plane (NP) during embankment filling and consolidation of soft soils when the soft soils is treated by using reinforced concrete floating piles. The results indicate that the pile axial force as well as negative skin friction is closely time dependent and increase much more quickly during the embankment filling than during the consolidation. The location of the NP exhibits a complicated variation as the pile head loads and the surcharge applied on the soft soils are varying with time. Most of the embankment load is born by pile for the existence of soil arch within the embankment.
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Stringer, M. E., i S. P. G. Madabhushi. "Re-mobilization of pile shaft friction after an earthquake". Canadian Geotechnical Journal 50, nr 9 (wrzesień 2013): 979–88. http://dx.doi.org/10.1139/cgj-2012-0261.
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During strong earthquakes, significant excess pore pressures can develop in saturated soils. After shaking ceases, the dissipation of these pressures can cause significant soil settlement, creating downward-acting frictional loads on piled foundations. Additionally, if the piles do not support the full axial load at the end of shaking, then the proportion of the superstructure’s vertical loading carried by the piles may change as a result of the soil settlement, further altering the axial load distribution on piles as the soil consolidates. In this paper, the effect of hydraulic conductivity and initial post-shaking pile head loading is investigated in terms of the changing axial load distribution and settlement responses. The investigation is carried out by considering the results from four dynamic centrifuge experiments in which a 2 × 2 pile group was embedded in a two-layer profile and subjected to strong shaking. It is found that large contrasts in hydraulic conductivity between the two layers of the soil model affected both the pile group settlements and axial load distribution. Both these results stem from the differences in excess pore pressure dissipation, part of which took place very rapidly when the underlying soil layer had a large hydraulic conductivity.
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Tsuha, Cristina de Hollanda Cavalcanti, João Manoel Sampaio Mathias dos Santos Filho i Thiago da Costa Santos. "Helical piles in unsaturated structured soil: a case study". Canadian Geotechnical Journal 53, nr 1 (styczeń 2016): 103–17. http://dx.doi.org/10.1139/cgj-2015-0017.
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The use of helical piles as tower foundations in Brazil has increased considerably during the last 5 years. A number of these piles are installed in unsaturated structured soils that cover a significant part of the Brazilian territory. However, the installation of helical piles in such soils produces a breakdown of the natural soil structure, which affects the pile performance for tension applications. This scenario motivates the present work, in which a comprehensive pile load-test program was carried out on helical piles composed of a single helix or multi-helices, installed in an unsaturated tropical residual soil. Eleven full-scale pile axial load tests were carried out, including two compression and nine tension tests. In addition, cone penetration tests were performed close to the piles after installation, and undisturbed soil samples were collected at the depth of the helices. The aim of these additional tests was to contribute to the understanding of the effect of helical pile installation on soil structure. The results of the tension load tests showed that the changes in the structure of the porous tested soil result in particularly low pile uplift capacities. In contrast, the load–settlement curves of the pile compression tests indicate a peculiar failure mechanism due to the sensitive soil structure associated with the high void ratio of the intact soil beneath the bottom plate.
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Zhao, Min, i Wei Ping Cao. "An Analysis of Pile-Soil Interaction under Embankment Load". Applied Mechanics and Materials 488-489 (styczeń 2014): 458–61. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.458.
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The complex interaction between the pile and surrounding soil significantly affects the behavior of the piled reinforced embankment. In this paper, a 3D numerical model of piled reinforced embankment was set up to explore the development of the settlement of the pile and the surrounding soft soils during the embankment filling as well as the subsequent consolidation of the soil. The evolution of the pile axial force, the skin friction and the neutral plane depth was also studied. The results show that the settlement of the pile and surrounding soil, the pile axial force, the skin friction along the pile shaft and the neutral plane depth during the embankment filling and the consolidation process experienced a complicated evolution.
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Janda, Tomás, Renato P. Cunha, Pavel Kuklík i Gérson M. Anjos. "Three Dimensional Finite Element Analysis and Back-analysis of CFA Standard Pile Groups and Piled Rafts Founded on Tropical Soil". Soils and Rocks 32, nr 1 (1.01.2009): 3–18. http://dx.doi.org/10.28927/sr.321003.
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This paper deals with Plaxis 3D finite element simulations of the mechanical response of deep foundations founded in a collapsible tropical soil. Main attention is initially paid to differences between single continuous flight auger (CFA) pile behavior and the behavior of CFA piles in standard groups. The numerically computed load-settlement curves are compared to field load test data obtained at the experimental research site of the University of Brasília (UnB), leading to conclusions about the appropriateness of adopting laboratory, in situ or back calculated parameters as input of numerical programs that simulate 3D foundation systems. Further, the contribution of the contact surficial soil/top raft is numerically examined by simulating the behavior of identical “piled raft” systems founded in the same site. The numerical simulated results of “piled raft” and standard pile group systems are then compared in terms of load capacity, system stiffness, load share between pile tip, shaft and raft, and mean developed lateral pile shaft friction. Having the results at distinct loading stages, as at working and failure levels, the analyses show the differential behavior, and design obtained responses, one may expect from conventional pile groups and “piled rafts” of CFA floating piles when founded in tropical soils. It is a mixed theoretical/experimental paper with practical interest for foundation designers and constructors.
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Huang, Yuan, Xin Jian Feng, Jian Lin Zhang i Shu Zhi Lin. "Working Mechanism of Two-Phase Varying Stiffness Piled Raft Foundation". Applied Mechanics and Materials 590 (czerwiec 2014): 326–30. http://dx.doi.org/10.4028/www.scientific.net/amm.590.326.
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In this paper, the FEM software ABAQUS is used to analysis the pile-soil load share ratios, load share value of pile side friction and tip resistance for three bases, including natural raft foundation, conventional piled raft foundation and two-phase varying stiffness piled raft foundation. Furthermore, the deformation and settlement of deformation-coordinating device are studied as well. Based on the research of the working characteristic of piles and soil, it highlights the good working mechanism of two-phase varying stiffness piled raft foundation. The analysis results show that two-phase varying stiffness piled raft foundation, with obvious two phase stress characteristics, has a working principle between natural raft foundation and conventional piled raft foundation, fully making use of the bearing capacity of foundation soil, effectively improving the joint bearing capacity of piles and soil.
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Lee, Su-Hyung, i Choong-Ki Chung. "An experimental study of the interaction of vertically loaded pile groups in sand". Canadian Geotechnical Journal 42, nr 5 (1.10.2005): 1485–93. http://dx.doi.org/10.1139/t05-068.
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The interactions among closely located piles and a cap in a pile group are complex. The current design practice for vertically loaded pile groups roughly estimates their overall behavior and generally yields conservative estimations of the group capacity. For a proper pile group design, factors such as the interaction among piles, the interaction between cap and piles, and the influence of pile installation method all need to be considered. This paper presents the results of the model test, which can be used to better understand the interactions of vertically loaded pile groups in granular soil. Load tests were carried out on the following: an isolated single pile, single-loaded center piles in groups, a footing without any piling, free standing pile groups, and piled footings. The influences of pile driving and the interactions among bearing components on loadsettlement and load transfer characteristics of piles and on the bearing behavior of a cap in a group are investigated separately by comparing their respective test results. The favorable interaction effects that increase pile capacities are identified.Key words: pile group, pile installation, interaction, model test, free standing, piled footing.
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Busse, Matt D., Carol J. Shestak i Ken R. Hubbert. "Soil heating during burning of forest slash piles and wood piles". International Journal of Wildland Fire 22, nr 6 (2013): 786. http://dx.doi.org/10.1071/wf12179.
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Pile burning of conifer slash is a common fuel reduction practice in forests of the western United States that has a direct, yet poorly quantified effect on soil heating. To address this knowledge gap, we measured the heat pulse beneath hand-built piles ranging widely in fuel composition and pile size in sandy-textured soils of the Lake Tahoe Basin. The soil heat pulse depended primarily on fuel composition, not on pile size. Burn piles dominated by large wood produced extreme temperatures in soil profile, with lethal heating lasting up to 3 days. In contrast, the heat pulse was moderate beneath piles containing a mixture of fuel sizes. Considerable spatial variability was noted, as soil temperatures were generally greatest near pile centres and decline sharply toward the pile edges. Also, saturating pile burns with water 8 h after ignition (‘mopping up’) effectively quenched the soil heat pulse while allowing near-complete fuel consumption. The findings suggest that burning of hand piles will not result in extreme or extensive soil heating except for uncommon conditions when piles are dominated by large wood and occupy a high percentage of the ground surface.
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Mahmood, Mahmood R., Nahla M. Salim i Ammar A. Al-Gezzy. "Effect of Different Soil Saturation Conditions on The Ultimate Uplift Resistance of Helical Pile Model". E3S Web of Conferences 318 (2021): 01012. http://dx.doi.org/10.1051/e3sconf/202131801012.
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Helical piles have many properties over the other types of piles systems include high tensile capabilities, the possibility of fast installation, applying load immediately after installation, and suitability for most soil's condition. In addition to that, helical piles have relatively less noise during installation; they represent a cost-effective alternative to conventional pile types. The use of helical piles grows in the world in the last fifty years. Many studies concentrate on the performance of this type of piles in fully saturated and dry soils. The achievement of the helical pile in unsaturated soils is rarely studied. So, to cover this small-scale demand model of the helical pile with double helices has been tested. Twenty tests were performed on three different models (pile with single helix, pile with double helices, and pile with triple helices) and pile shaft only, embedded in different conditions of soil saturation (fully saturated, partially saturated, and dry soils) under uplift loading. Three different matric suction of partial saturation were used of 6.5, 7.4, and 9.6 kPa. The results obtained from the tests showed that the highest value in the unsaturated soil was at suction 6.5 kPa compared to other soil saturation conditions. The results mention that model piles embedded in dry soil have lower values of ultimate uplift capacities. The increment in uplift resistance of additional helices of single double and triple helices than that of shaft pipe embedded within dry soil shows an increment by approximately about 170, 240, and 282% respectively, for fully saturation soil, the increment about 342, 463, and 585% respectively, and by about 400, 429, and 475% respectively for matric suction of 6.5 kPa.
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Chen, Jun, Yong Hong Chang i Yin Sheng Zou. "Nonlinear Analysis of Interaction of Superstructure-Pile-Raft-Soil System in Layered Soil — Part II: Characteristics of Reaction Force on Pile Head and Displacement of Raft". Key Engineering Materials 400-402 (październik 2008): 659–66. http://dx.doi.org/10.4028/www.scientific.net/kem.400-402.659.
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Using the nonlinear analysis method and program of the interaction of superstructure- pile-raft-soil system in layered soil in the state of the previous literature, the reaction force on the pile head and the displacement characteristics of raft of the piled-raft foundation are analysed when the thickness of the raft, the spacing of the piles, the length and the diameter of the pile are changed. Some quantitative data and qualitative conclusions are obtained in this paper.
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Zhu, Rui, Feng Zhou, Zhihui Wan, Shengjun Deng, Xin Dong, Zekun Zhou i Wei Xing. "Improving the Performance of Piled Raft Foundations Using Deformation Adjustors: A Case Study". Buildings 12, nr 11 (6.11.2022): 1903. http://dx.doi.org/10.3390/buildings12111903.
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Complicated soil conditions are direct difficulties for high-rise building projects. A new device called a deformation adjustor, which is used to optimize the stiffness distribution in the piled raft system, has achieved good results for this challenge. This paper presents a case study on the application of deformation adjustors to improve the performance of a piled raft foundation. This case study describes the preliminary design of pile-raft foundations with deformation adjustors, followed by numerical analysis. Based on the numerical study, the potential savings are demonstrated due to the good performance of soil bearing capacity. Comparing the numerical results with the monitoring results in raft settlements, earth pressures, deformation amount of deformation adjustors, pile top reactions, and load-sharing ratios between soils and piles, the accuracy of the design schemes with an aided numerical analysis is verified. Through a long-term monitoring, soils below the raft carried 63% of the total applied loads, while the piles bear 37% of the loads. This case study proved that a piled raft foundation with deformation adjustors was an effective and economical design scheme, which can make full use of the soil bearing capacity. It is of great significance to facilitate the design and construction of piled raft foundations in complicated soil conditions.
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Xie, Yunfei, Shichun Chi i Maohua Wang. "Influence of Variable Rigidity Design of Piled Raft Foundation on Seismic Performance of Buildings". Mathematical Problems in Engineering 2020 (14.03.2020): 1–13. http://dx.doi.org/10.1155/2020/1780197.
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In order to reduce the costs and improve the overall performance of building systems, the static optimized design with variable rigidity of piled raft foundations has been widely used in recent years. Variable rigidity design of piled raft foundations that support midrise buildings in high-risk seismic zones can alter the dynamic characteristics of the soil-pile-structure system during an earthquake due to soil-pile-structure interaction. To investigate these aspects, a nuclear power plant sitting on multilayered soil is simulated numerically. The paper describes a numerical modeling technique for the simulation of complex seismic soil-pile-structure interaction phenomena. It was observed that the total shear force on top of the piles and the rocking of the raft are reduced after optimization, whereas the displacement of the superstructure is nearly unaffected. The findings of this study can help engineers select a correct pile arrangement when considering the seismic performance of a building sitting on soft soil.
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Al-Damluji, Omar al-Farouk Salem, i Nadher Hassan Al-Baghdadi. "ANALYSIS OF PILED-RAFT FOUNDATION BY THE FINITE ELEMENT METHOD". Kufa Journal of Engineering 3, nr 2 (26.05.2014): 115–32. http://dx.doi.org/10.30572/2018/kje/321264.
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The piled raft is a geotechnical composite construction consisting of three elements: piles,raft and soil. It is suitable as a foundation for large buildings. This paper presents an analysis of piled raft foundation, included material nonlinearity and soil structure interaction. An efficient computer program in FORTRAN 9Ois developed for this analysis. A 20 node disoparametric brick element has been used to model pile, raft, soil and interface materials. Thin layer interface element has been used to model the contact zone between the pile and soil, and between raft and soil. The behavior of the piled raft material is simulated by using a linear elastic model. However, the behavior of soil and interface materials is simulated by an elasto-plastic model by the use of Mohr Coulomb failure criterion. Some of the variables of piled-raft system, related to settlement and differential settlement in sandy soil, have been studied, where the length of piles and distance between piles an effective role in reducing both settlement and differential settlement of foundation system. Also increasing the thickness of raft foundation reduces the effectiveness of additional piles for the purpose of reducing differential settlement.
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Mohamad Ali, Anis Abdul Khuder, Jaffar Ahemd Kadim i Ali Hashim Mohamad. "Design Charts for Axially Loaded Single Pile Action". Civil Engineering Journal 5, nr 4 (27.04.2019): 922–39. http://dx.doi.org/10.28991/cej-2019-03091300.
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The objective of this article is to generating the design charts deals with the axially ultimate capacity of single pile action by relating the soil and pile engineering properties with the pile capacity components. The soil and are connected together by the interface finite element along pile side an on its remote end. The analysis was carried out using ABAQUS software to find the nonlinear solution of the problem. Both pile and soil were modeled with three-dimensional brick elements. The software program is verified against field load-test measurements to verify its efficiency accuracy. The concrete bored piles are used with different lengths and pile diameter is taken equals to 0.6 m. The piles were installed into a single layer of sand soil with angles of internal friction (20° t0 40°) and into a single layer of clay soil with Cohesion (24 to 96) kPa. The getting results showed that for all cases study the total compression resistance is increased as pile length increased for the same property of soil, also illustrious that the total resistance of same pile length and diameter increased as the soil strength increasing. In addition, the same results were obtained for the end bearing resistance, skin resistance and tension capacity. Design charts were constructed between different types of soil resistance ratio and the pile length/diameter ratio (L/D) for all cases of study. One of improvement found from these curves that it is cheaply using piles of larger diameter than increasing their lengths for dense sand and to increasing piles lengths for loose sand. Moreover, it is inexpensively using piles of larger length in soft clay soil than increasing their diameter and piles of larger diameter in firm and stiff clay soils than increasing their length.
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Fellenius, Bengt H. "Observations and analysis of wide piled foundations". Canadian Geotechnical Journal 56, nr 3 (marzec 2019): 378–97. http://dx.doi.org/10.1139/cgj-2018-0031.
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Available case histories on observations on full-scale piled rafts show that the settlement response to applied load can be modeled as that for an Equivalent Pier due to compression of the piles and the soil matrix plus that of an Equivalent Raft for compression of soil layers below the pile toe level. Interior piles engage the soil from the pile toe level upward in contrast to a single pile, which engages it from the ground downward. Piles and soil, combined as a pier, have strain compatibility, which determines the distribution of load between the piles, the contact stress, and the load-transfer movement of the piles. The responses between the interior and perimeter piles differ. Particularly so in non-subsiding and subsiding environment, because perimeter piles can be subjected to downdrag and drag forces, while neither downdrag nor drag force will affect the interior piles. In non-subsiding environment, it is advantageous to make perimeter piles shorter, while in subsiding environment perimeter piles best be longer. The load distribution across the raft is also governed by the degree of rigidity of the raft and by the difference in dishing at the pile toe level and in the dishing of the actual raft.
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Chen, S. L., C. Y. Song i L. Z. Chen. "Two-pile interaction factor revisited". Canadian Geotechnical Journal 48, nr 5 (maj 2011): 754–66. http://dx.doi.org/10.1139/t10-095.
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A rigorous analytical method is developed for calculating the interaction factor between two identical piles subjected to vertical loads. Following the scheme proposed by Muki and Sternberg, the problem is formulated by decomposing the pile soil system into an extended soil mass and two fictitious piles. With the consideration of the compatibility condition that the axial strain of the fictitious pile be equal to the corresponding strain average over the extended soil, a Fredholm integral equation of the second kind governing the unknown axial forces along fictitious piles is established and then solved using numerical procedures. The real pile head settlement is subsequently calculated based on the determined fictitious pile forces and finally, the desired pile interaction factor is derived. Comparison with existing solutions confirms that the conventional interaction factor approach does tend to overestimate the interaction and may cause considerable errors for long compressible piles. Numerical results for the interaction factor between two piles in both semi-infinite and finite layered soils are presented over a wide range of pile and soil parameters, and also the settlement behaviour of a 3 × 3 pile group embedded in a semi-infinite soil is studied by virtue of the newly established interaction factor.
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Yushchube, S. V., i I. I. Podshivalov. "MODELING OF STRESS-STRAIN STATE OF HIGH-RISE BUILDING PILE RAFT FOUNDATION WITH INCOMPLETE PILE INSTALLATION". Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 22, nr 2 (30.04.2020): 145–61. http://dx.doi.org/10.31675/1607-1859-2020-22-2-145-161.
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The object of the study is a pile-raft foundation or mat foundation 180 cm thick of a 25-storey building made of a reinforced concrete frame. When constructing a pile foundation, some of piles are not completely sank down to the reference points. In this connection, it is necessary to identify the reasons and load-bearing capacity of piles, given the soil compaction between piles and under their tips and the possibility of using such piles for further building construction.After studying the materials of soil investigation, the analysis of occurrence, composition, physical-mechanical properties of soils, and the pile field, the stress-strain state model is developed for the pile-raft foundation using the MicroFe software application with the development of design model for the foundation-base-building system.In the compacted soil state between the piles and under the pile tips, the conditions of the ultimate and service limit states are met at the actual depth of pile sinking for the raft foundation.
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Tan, Feng Yi, i Xin Zhi Wang. "Numerical Analysis for Bearing Performance of Flexible Piles Composite Foundation Influenced by Modulus’ Changes". Advanced Materials Research 261-263 (maj 2011): 1694–98. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.1694.
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The bearing performance of composite foundation improved by flexible piles was influenced by changes of cushion’s modulus, the modulus ratio between soil on bottom of pile and soil surrounded pile, which was analyzed by the finite element method. Results showed that: 1.For single pile, by increasing of cushion’s modulus, the bearing performance nearby the top of flexible pile increased apparently, and the common tendency of settlement of pile and soil surrounded piles was affected negatively. For multi-piles, the increasing of cushion’s modulus resulted in the increasing of bearing performance and the common tendency of settlement of piles and soil surrounded piles was affected positively. 2.The change of modulus ratio between soil surrounded piles and soil on bottom of piles resulted positively in the change of frictional resistance and end-bearing performance nearby the bottom of single pile and reduced the settlement of composite foundation. But the multi-pile borne absolutely all loading due to the increasing of modulus ratio, and both of piles and soil surrounded piles had the same tendency of settlement.
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Doubrovsky, M. P., i V. O. Dubravina. "MODEL TESTING OF THE "PILE-SOIL" INTERACTION UNDER AXIAL FORCE". Bulletin of Odessa State Academy of Civil Engineering and Architecture, nr 83 (4.06.2021): 102–11. http://dx.doi.org/10.31650/2415-377x-2021-83-102-111.
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Modern marine structures (berths, breakwaters, offshore platforms, etc.) often include steel tubular piles of essential length (80-100 m and more) that should provide high bearing capacity in case of external axial loads application. Interaction between elements of the system “piled structure – soil media” is not studied sufficiently yet. It relates also to the bearing capacity of the long steel tubular piles of large diameter. One of the interesting peculiarities of long tubular piles behavior is the formation of soil plug at the piles tip. There are a lot of suggestion and methods aimed to increase piles bearing capacity under static pressing load. One of them relates to use of the additional structural element, i.e., the internal diaphragm welded to the internal surface of the pile shaft. Such approach has been applied in some practical cases of marine construction and demonstrated its effectiveness. At the moment there are no researches focused on study of the peculiarities of internal diaphragm application. So proposed research aimed to study two connected processes during steel tubular pile driving: soil plug formation at the tip of the open-end pile and soil behavior under the internal diaphragm fixed inside the tubular pile shaft. To study mentioned processes we provided several series of laboratory experiments fulfilled at the Geotechnical laboratory of the Department “Sea, River Ports and Waterways” in Odessa National Maritime University. In these experiments the model of steel tubular pile has been driven (pressed) into fine sand by mechanical jack. The first series was devoted to determination of the conditions related to the soil plug formation at the pile tip. The next series were aimed to study the influence of the flat rigid diaphragm inside the pile shaft. Obtained experimental results allow to conclude that (a) in the fine sand the plug is formatted at the comparatively early stage of pile installation (in case of our modeling – at the penetration depth of some 4-5 pile diameter); (b) our empirical assessment of the conditions of soil plug formation corresponds to the approaches based on PLR and IFR characteristics; (c) formation of soil plug at the pile tip is followed by decreasing of soil level in the pile shaft relatively its initial value (on completing the plug formation the soil level in the shaft become stable); (d) regarding above mentioned, we may note that in case of use of internal diaphragm on the recommended depth (5-7 pile diameters) there may be no contact between diaphragm and the soil inside the pile (e) application of the diaphragm may lead to increasing of the pile’s bearing capacity. It was proposed (and checked by our tests) the technological improvement based on sand filling into space under the internal diaphragm to provide constant diaphragm-soil contact and related soil resistance.
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Chiou, Jiunn-Shyang, i Jia-Qi You. "Theoretical solutions of laterally loaded fixed-head piles in elastoplastic soil considering pile-head flexural yielding". Canadian Geotechnical Journal 57, nr 5 (maj 2020): 650–60. http://dx.doi.org/10.1139/cgj-2018-0593.
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Group piles with a cap under lateral loading behave like fixed-head piles because of the rotational restraint of the pile cap. They are susceptible to flexural yielding at the pile head due to high bending strains. In addition to soil nonlinearity, the pile-head flexural nonlinearity also significantly contributes to nonlinear responses of the piles, which is not covered in most existing analytical solutions. For a fixed-head pile buried in uniform elastoplastic soils, this study derives analytical solutions for the lateral responses to account for soil yielding, and flexural yielding and failure of the pile section at the pile head. The model assumes elastoplastic Winkler-type soil with constant subgrade stiffness and yield strength and a nonlinear moment–curvature curve for the pile section. Examples are provided to apply the solutions to determine the complete capacity curves (moment and horizontal load) of a fixed-head pile and the derived analytical capacity curves are in good agreement with those from numerical analyses that use nonlinear beam elements to reflect the nonlinear flexural behavior of the pile section. The solutions are also applied to evaluate the influences of the yield displacement of the soil and different forms of simplified nonlinear moment–curvature curves of the pile section on the lateral load–displacement curves.
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Романов, С. В., i М. М. Козаченко. "EFFICIENCY OF PILE DRIVE TECHNOLOGY IN DIFFERENT SOIL CONDITIONS". Building production, nr 72 (22.05.2023): 55. http://dx.doi.org/10.36750/2524-2555.72.55-60.
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Based on the experience of SE NDIBV and TEHKOMP LLC in the development and application of pile and sheet piling technology in the construction of new and reconstruction of existing buildings, the article examines the effectiveness of pile piling technology in various soil conditions. The purpose of this article is to establish an effective field of application of the method of driving piles during installation or strengthening of building foundations.In order to achieve the specified goal, the following were processed and summarized the results of pile driving works performed in the past years; the analytical dependencies (1) and (2) between the main parameters of the pile driving process, the violation of which makes pile driving impossible or impractical, were analyzed; on the basis of the statistical processing of the test results of the experimental depressed piles, the values of the coefficient of change in the bearing capacity of the soil around the depressed piles in Kgr time, the values of which vary in different soil conditions from 0.6 to 1.5, were specified and given.It follows from dependence (2) that the greater the value of the coefficient of change in the load-bearing capacity of the soil around the pressed piles in the time Kgr, the less pressing force is required to ensure the same load-bearing capacity of the piles Fd. For example, to ensure the bearing capacity of a pile of 1000 kN, the following values of the compression force Nvd are required: at Kgr=1.5 Nvd=800 kN; at Kgr=1.0 Nvd=1200 kN; at Kgr=0.6 Nvd=2000 kN.This means that in order to achieve the same effect when driving a pile in soil conditions where Kgr=0.6, the pressing force is 2.5 times more than in soil conditions where Kgr=1.5. Based on the above, all soil conditions, represented by several soils, are proposed to be classified (divided) into the following three groups according to the effectiveness of the pile driving technology application: Group I - "highly effective" - soil conditions that have Kgr≥1.1; II group - "effective" - soil conditions with 0.9≤Kgr≤1.1; III group - "not effective" - soil conditions with Kgr≤0.9.The following conclusions are given in the article.The field of application of the method of driving piles according to soil conditions is characterized by the presence of three groups of conditions: group I – highly effective conditions; group II – effective conditions; group III - not effective conditions.Soil conditions of group I, in which the method of driving in piles is highly effective, are represented from above to the roof of the bearing layer by dusty clayey soils with a consistency index IL > 0.25 and have a value of the coefficient of change of the bearing capacity of the soil around the driven pile in Kgr time of at least 1, 10 (see items 1, 2, 3, 4 of table 1).The soil conditions of group II, in which the pile driving method is effective enough, differ from the conditions of group I in that in dusty-clay soils with IL >0.25 cut by piles, there may be dense layers of sandy or dusty-clay soils and have the value of the coefficient of change in bearing capacity of soil around the driven pile 0.9 ≤ Kgr <1.1 (see items 5, 6, 7 of table 1). In such conditions, the piles are driven in, as a rule, through pilot wells, or using the effect of soil thixotropy by drilling wells without extracting the soil. Compared to soil conditions of the I group, this worsens such indicators as cost, productivity and terms of performance of works.Soil conditions of the III group, represented by sands of medium density or dense with the value of the coefficient of change of the bearing capacity of the soil around the driven pile Kgr<0.9 must be excluded from the field of application of the technology of driving piles.
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Fenu, Luigi, Eleonora Congiu, Mariangela Deligia, Gian Felice Giaccu, Alireza Hosseini i Mauro Serra. "Buckling Analysis of Piles in Multi-Layered Soils". Applied Sciences 11, nr 22 (11.11.2021): 10624. http://dx.doi.org/10.3390/app112210624.
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Pile buckling is infrequent, but sometimes it can occur in slender piles (i.e., micropiles) driven into soils with soft layers and/or voids. Buckling analysis of piles becomes more complex if the pile is surrounded by multi-layered soil. In this case, the well-known Timoshenko’s solution for pile buckling is of no use because it refers to single-layered soils. A variational approach for buckling analysis of piles in multi-layered soils is herein proposed. The proposed method allows for the estimation of the critical buckling load of piles in any multi-layered soil and for any boundary condition, provided that the distribution of the soil coefficient of the subgrade reaction is available. An eigenvalue-eigenvector problem is defined, where each eigenvector is the set of coefficients of a Fourier series describing the second-order displaced shape of the pile, and the related buckling load is the eigenvalue, thus obtaining the effective buckling load as the minimum eigenvalue. Besides the pile deformed shape, the stiffness distribution in the multi-layered soil is also described through a Fourier series. The Rayleigh–Ritz direct method is used to identify the Fourier development coefficients describing the pile deformation. For validation, buckling analysis results were compared with those obtained from an experimental test and a finite element analysis available in the literature, which confirmed this method’s reliability.
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Saha, Rajib, Sekhar Chandra Dutta i Sumanta Haldar. "SEISMIC RESPONSE OF SOIL-PILE RAFT-STRUCTURE SYSTEM". Journal of Civil Engineering and Management 21, nr 2 (30.01.2015): 144–64. http://dx.doi.org/10.3846/13923730.2013.802716.
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This paper presents an initial effort to investigate seismic response of soil-pile raft-structure system considering soil-structure interaction effect. In general, structure and piled raft under seismic load are designed considering fixed base condition. However, soil flexibility may result significant changes in the response of soil-pile raft-structure system. The study considers one storey system consisting of a mass in the form of a rigid floor slab supported by four columns. The piles are modelled by beam-column element supported by laterally distributed springs and dampers. This simple model used in present study is adequately tuned to exhibit reasonably accurate dynamic characteristics while compared to the existing well accepted methodologies. The study shows that soil-structure interaction leads to considerable lengthening of period though the lateral shear in columns are not significantly changed. However, the shear in piles is significantly increased due to SSI effect as inertia of the considerable foundation mass contributes to this increase in shear of pile. Thus, neglecting SSI may lead to unsafe seismic design of piles. A parametric study encompassing feasible variations of parameters is made under spectrum consistent ground motion. Effect of uncertainty in the soil subgrade modulus on the pile and column response variability is also studied.
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Kahyaoglu, Mehmet Rifat, Okan Onal, Gökhan Imançlı, Gürkan Ozden i Arif S. Kayalar. "SOIL ARCHING AND LOAD TRANSFER MECHANISM FOR SLOPE STABILIZED WITH PILES". Journal of Civil Engineering and Management 18, nr 5 (28.09.2012): 701–8. http://dx.doi.org/10.3846/13923730.2012.723353.
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In this study, the effects of pile spacing and pile head fixity on the moment and lateral soil pressure distribution along slope stabilizing piles are investigated. A slice from an infinitely long row of piles with fixed pile tip in an inclined sand bed was simulated with an experimental test setup. Surficial soil displacements were monitored and relative displacements between soil particles were determined by recording time-lapse images during the test in order to observe the soil arching mechanism on the soil surface. The load transfer process from moving soil to piles and behavior of soil around piles were observed and evaluated by the different test setups. It was observed that decrease in pile spacing causes an increase of load carried per pile. This behavior, which was significantly influenced by the pile head boundary conditions, can only be explained by soil arching that existed between the piles along their lengths.
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Doubrovsky, Michael, i Vladyslava Dubravina. "Physical modeling of steel tubular piles installation into sandy soil". Bases and Foundations, nr 41 (17.12.2020): 14–21. http://dx.doi.org/10.32347/0475-1132.41.2020.14-21.
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Modern marine structures (berths, breakwaters, offshore platforms, etc.) often include steel tubular piles of essential length (80-100 m and more) that should provide high bearing capacity in case of external axial loads application. Interaction between elements of the system “piled structure – soil media” is not yet studied sufficiently. It relates also to the bearing capacity of the long steel tubular piles of large diameter. One of the interesting peculiarities of long tubular piles’ behavior is the formation of soil plug at the piles’ tip. There are a lot of suggestion and methods aimed to increase piles bearing capacity under static pressing load. One of them relates to use of the additional structural element, i.e., the internal diaphragm welded to the internal surface of the pile’s shaft. Such approach has been applied in some practical cases of marine construction and demonstrated its effectiveness. At the moment there are no researches focused on study of the peculiarities of internal diaphragm application. So proposed research aimed to study two connected processes during steel tubular pile driving: soil plug formation at the tip of the open-end pile and soil behavior under the internal diaphragm fixed inside the tubular pile’s shaft. To study mentioned processes we provided several series of laboratory experiments fulfilled at the Geotechnical laboratory of the Department “Sea, River Ports and Waterways” in Odessa National Maritime University. In these experiments the model of steel tubular pile has been driven (pressed) into fine sand by mechanical jack. The first series was devoted to determination of the conditions related to the soil plug formation at the pile’s tip (results are presented in this paper). The next series were aimed to study the influence of the rigid diaphragm inside the pile’s shaft (to be presented in the further publications). Obtained experimental results allow to conclude that (a) in the fine sand the plug is formatted at the comparatively early stage of pile installation (in case of our modeling - at the penetration depth of some 4-5 pile’s diameter); (b) our empirical assessment of the conditions of soil plug formation corresponds to the approaches based on PLR and IFR characteristics; (c) formation of soil plug at the pile’s tip is followed by decreasing of soil level in the pile’s shaft relatively its initial value (on completing the plug formation the soil level in the shaft become stable); (d) regarding above mentioned, we may note that in case of use of internal diaphragm on the recommended depth (5-7 pile’s diameters) there may be no contact between diaphragm and the soil inside the pile and the diaphragm does not come up with the soil. So, for the next series of our experiments, it should be foreseen assured contact of the diaphragm’s surface with soil underneath.
As proved by previous studies, one of the interesting features of the behavior of long tubular piles is the formation of a soil plug at the lower end of the pile. From this point of view, it is important to study the effect of soil plug not only on the bearing capacity at the lower end of the pile, but also on the behavior of the soil inside the pile. It is shown that in fine-sandy soils a plug is formed at a relatively early stage of pile immersion (in this case - at a depth of immersion of about 4-5 pile diameters). The process of forming a soil plug at the lower end of the tubular pile during its immersion is accompanied by a decrease in soil surface level in the pile trunk relative to its initial value (upon completion of plug formation the soil surface level in the pile trunk stabilizes).
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Chen, Heng, i Ke Sheng Ma. "The Mechanical Properties Comparative Analysis for Socked and Non-Socketed Composite Pile". Advanced Materials Research 1061-1062 (grudzień 2014): 748–50. http://dx.doi.org/10.4028/www.scientific.net/amr.1061-1062.748.
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For socked and non-socketed piles in the different mechanical behavior under static and dynamic loads, the paper use ABAQUS to model, simulate the pile , the soil interlayer thickness between the bottom of the pile and bedrock are 2m, 4m under vertical load and Earthquake, cushion cap, pile and pile soil stress situation found non-socketed piles when the soil interlayer thickness within a certain range, the composite pile small subside under dynamic, static loads, the non-socketed piles can better take advantage of the pile soil has a good seismic performance in the earthquake.
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Suleiman, Muhannad T., Lusu Ni, Anne Raich, Jeffery Helm i Ehsan Ghazanfari. "Measured soil–structure interaction for concrete piles subjected to lateral loading". Canadian Geotechnical Journal 52, nr 8 (sierpień 2015): 1168–79. http://dx.doi.org/10.1139/cgj-2014-0197.
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Lateral loads often control the design of deep foundations. This paper focuses on improving the understanding of soil–structure interaction (SSI) of laterally loaded piles and developing p–y curves based on simultaneous direct measurements of the soil–pile interaction pressure (p) and lateral pile displacement (y) along the length of the pile. This paper summarizes the methodology, instrumentation, soil–pile interaction measurements, and procedure used to investigate the soil–pile interaction and to develop the directly measured p–y curves. A 102 mm diameter, 1.42 m long precast concrete pile was fully instrumented with advanced sensors and installed in well-graded sand. The digital image correlation (DIC) data indicated that the soil movement in front of the pile extended up to 6.3 pile diameters (6.3D) from the pile center. The normalized measured maximum soil–pile interaction pressures closely matched the normalized pressures provided in the literature for short, stiff laterally loaded piles installed in cohesionless soils. In addition, the direct measurement-based p–y curves at different depths showed nonlinear behavior, in which the initial stiffness and ultimate soil reaction increased as the depth increased. When compared to p–y curves calculated from measured strain along the pile length, the directly measured p–y curves showed differences of ultimate soil reaction ranging from 8% to 33%. When compared to p–y curves calculated using the procedures available in the literature, the measurement-based p–y curve ultimate soil reactions have differences ranging from 5% to 189%. The differences in ultimate soil reaction could be mainly attributed to the installation method.
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Shojaeian, Ali, Sumangali Sivakumaran i Kanthasamy K. Muraleetharan. "Seismic behavior of pile foundations in unsaturated soils". E3S Web of Conferences 382 (2023): 03009. http://dx.doi.org/10.1051/e3sconf/202338203009.
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Earthquakes have caused significant damage to civil engineering structures worldwide due to inadequate lateral load capacity and excessive deformation of pile foundations supporting these structures. The seismic performance of pile foundations interacting with unsaturated soils could be affected by changes in matric suction due to the moisture content variation induced by seasonal weather changes or water table fluctuations. Hence, the main objective of this study is to investigate the effects of unsaturated soil conditions on the seismic response of a pile-soil system in silty clay soils. This study utilized a stand-alone finite element computer code called DYPAC (Dynamic Piles Analysis Code) developed using the Beams on Nonlinear Winkler Foundation (BNWF) approach. Free field soil displacements and p-y curve parameters, inputs needed for DYPAC analyses, were updated based on the soil suction variations. This study found that soil suction can significantly influence the seismic performance of piles interacting with unsaturated silty clay soils, especially as the soil becomes drier in the transition zone. The best seismic performance of the pile, which is the minimum lateral pile displacement, happened in the transition zone between fully saturated and nearly dry conditions.