Journal articles on the topic 'Subgrade soils'
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1
Li, Cong, and Wei Lan. "Study on Moisture Modification for Resilient Modulus of Subgrade." Applied Mechanics and Materials 361-363 (August 2013): 1460–66. http://dx.doi.org/10.4028/www.scientific.net/amm.361-363.1460.
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Subgrade resilient modulus of 3 typical soils, namely sand, silt and clay, have been measured under different conditions of 2 target dry density and 3 target water content by triaxial repeated-loading test. Analysis has been focused on the effect law of subgrade moisture and compaction for resilient modulus based on test results. Subgrade moisture has some impact on resilient modulus of test soils, especially on that of fine-grained soils. The influence degree of subgrde compaction depends on soil group. Coefficient of moisture modification has been introduced to characterize relationship between subgrade moisture and resilient modulus. Two-parameter Logistic model with inflexion control has been proposed according to the following basic rule. Coefficient of moisture modification usually increases or decreases along with the decrement or increment of subgrade moisture. And then variety rate of coefficient becomes small in state of high or low water content.
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Sawangsuriya, Auckpath, Tuncer B. Edil, and Peter J. Bosscher. "Modulus−suction−moisture relationship for compacted soils." Canadian Geotechnical Journal 45, no. 7 (July 2008): 973–83. http://dx.doi.org/10.1139/t08-033.
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The ultimate parameter of interest in engineering design of compacted subgrades and support fills for highways, railroads, airfields, parking lots, and mat foundations is often the soil modulus. Modulus of compacted soils depends not only on dry unit weight and moisture but also on matric suction and soil structure (or fabric) resulting from the compaction process. However, these relationships in the as-compacted state (i.e., immediately after compaction) have not yet been extensively explored. This paper presents an experimental laboratory study of the shear modulus – matric suction – moisture content-dry unit weight relationship using three compacted subgrade soils. Compacted subgrade specimens were prepared over a range of molding water contents from dry to wet of optimum using enhanced, standard, and reduced Proctor efforts. A nondestructive elastic wave propagation technique, known as bender elements, was used to assess the shear wave velocity and corresponding small-strain shear modulus (Go) of the compacted subgrade specimens. The matric suctions were measured with the filter paper method. An empirical relation that takes into account the effect of compaction conditions is proposed for the Go – matric suction – molding water content relationship of compacted subgrade soils.
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Antonovskaya, Galina N., Nikita Y. Afonin, Irina M. Basakina, Natalia K. Kapustian, Boris G. Basakin, and Aleksey V. Danilov. "Possibilities of seismic methods for the estimation of a railway roadbed state under the conditions of the far north." Transportation systems and technology 3, no. 3 (September 15, 2017): 133–61. http://dx.doi.org/10.17816/transsyst201733133-161.
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The article presents results of monitoring state of railway subgrade using seismic methods in the Far North area. Purpose: The purpose of the studies is to find out reasons of subgrade subsidence in turfed soils of Onezhsky District of Arkhangelsk Oblast. Methodology: Studying soils in foundations of subgrade, a complex of active and passive methods was used, including: seismic exploration of refracted waves, multi-channel analysis of ground waves, and engineering seismic analysis based upon spectrum analysis of seismic noises. This complex enabled considering and estimating the system “subgrade-soils of foundations”. Results: A relative high capacity of weak soils, probably containing turf, lying under subgrade. Sections of increased water saturation in subgrade soils were found out. Loads from passing trains and resonant effect in weak soils cause its compression resulting in emergence of subsidence. Resonant effects whereby are not that strong, whereas passing trains have a more significant impact on the state of subgrades. Practical significance: Elaboration of technology of quick estimation of state of railway subgrade for immediate detection of a dangerous defect at an early stage of its development is a topical and acute challenge.
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Yang, Shu-Rong, Wei-Hsing Huang, and Yu-Tsung Tai. "Variation of Resilient Modulus with Soil Suction for Compacted Subgrade Soils." Transportation Research Record: Journal of the Transportation Research Board 1913, no. 1 (January 2005): 99–106. http://dx.doi.org/10.1177/0361198105191300110.
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The variations of resilient modulus with the postconstruction moisture content and soil suction for cohesive subgrade soils were evaluated. In particular, the effects of relative compaction of the subgrade on the suction and resilient modulus were investigated. To simulate subgrade soils at in-service conditions, soil specimens were compacted at various relative compactions and optimum moisture content and then saturated to equilibrium moisture content to test for resilient modulus and soil suction. The filter paper method was used to measure the total and matric suctions of two cohesive soils. Test findings demonstrated that resilient modulus correlated better with the matric suction than with total suction. Matric suction was found to be a key parameter for predicting the resilient modulus of cohesive subgrade soils. A prediction model incorporating deviator stress and matric suction for subgrade soil resilient modulus was established.
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Zhang, Yu, Xuerui Chen, Meisi Zou, Runze Tian, Yunlong Hou, and Bingbing Han. "Impact of Isothermal Layering on the Stability of Saline Soil Subgrade in Cold Regions." Geofluids 2022 (April 4, 2022): 1–13. http://dx.doi.org/10.1155/2022/3141964.
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In order to determine the influence of heat on the stability of the saline soil subgrade slope in cold regions. Firstly, four typical representative saline soils were selected as subgrade fillers, and geotextiles were added at the bottom of the subgrade as a study subject. A two-dimensional numerical model for the temperature field of subgrade soil was established based on COMSOL Multiphysics. Secondly, combined with the main strength parameters of subgrade soil at different temperatures, an isothermal stratification-strength parameter function calculation model was proposed. Then, the SLOPE/W module in GeoStudio is used to stratify the established subgrade model according to isotherms and calculate the stability safety factor of saline soil subgrades in cold regions under different months, slopes, and subgrade heights, respectively. Finally, the influence of submergence at the foot of the slope on the stability of the subgrade slope is discussed. The results show: After the cold season coming, with the decreasing of temperature, the stability of HC-1 and HC-2 saline soil subgrade slope increased to different extents when the ground temperature dropped to -10°C. When the local temperature dropped below -10°C, the stability has slight decline; CS-1 and CS-2 saline soil subgrade in the ground temperature dropped to 10°C (HC-1 and HC-2 denote two groups of saline soil with high chloride-salt content (≥15%) and low sulfate salt content (≤0.5%), whereas CS-1 and CS-2 denote two groups of saline soil with low chloride-salt (≤5%)), the slope stability was significantly improved, and the stability of CS-1 increases slightly with further decrease in temperature.
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Lee, Woojin, N. C. Bohra, A. G. Altschaeffl, and T. D. White. "Resilient modulus of cohesive soils and the effect of freeze–thaw." Canadian Geotechnical Journal 32, no. 4 (August 1, 1995): 559–68. http://dx.doi.org/10.1139/t95-059.
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Resilient modulus tests were performed on five cohesive soils sampled from the subgrades of in-service pavements. The stress at 1% strain in the unconfined compression test (Su1.0%) was found to be a good indicator of the resilient modulus (MR), and an empirical relationship between MR and Su1.0% was obtained. The proposed relationship itself is not affected by the changes in subgrade after construction and, therefore, is applicable to as-compacted and in-service subgrade conditions. Closed-system freeze–thaw tests were also performed and the effect of freeze–thaw on the resilient modulus was studied. There is a negligible effect of freeze–thaw, without ice lens formation, for soils having values of Su1.0% less than 8 psi (55 kPa), while the effect of freeze–thaw increases as the value of Su1.0% increases. For example, a soil with a value of Su1.0% greater than 15 psi (103 kPa) would exhibit more than 50% reduction in resilient modulus due to the effect of freeze–thaw. The resilient modulus of frozen cohesive soil is independent of the repeated deviator stress. Key words : resilient modulus, subgrade, pavement, freeze–thaw.
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Zheng, Xiaomeng, Zhushan Shao, Nannan Zhao, Chenglong Li, and Kui Wu. "Performance Evaluation of Tunnel-Slag-Improved High Liquid Limit Soil in Subgrade: A Case Study." Materials 15, no. 5 (March 7, 2022): 1976. http://dx.doi.org/10.3390/ma15051976.
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The application of tunnel-slag-improved high liquid limit soil as filling materials in subgrade is a green environmental technology. This study explored the influence of tunnel slag mixing on the physical and mechanical properties of improved soils, based on the engineering background of Liyu highway, Guangxi Province, China. Firstly, the optimal moisture content, maximum dry density, shear strength parameters, California bearing ratio (CBR) and resilience modulus of plain and tunnel-slag-improved high liquid limit soils were experimentally determined. Results showed that the direct utilization of untreated soil was unacceptable in subgrade practice. A significant enhancement of integrity of high liquid limit soils could be obtained by tunnel slag mixing, and the value of 15% was determined as the optimal tunnel slag content in soils, leading to improved soil performance meeting the specification requirements. Then, numerical simulation on the stability of subgrade slope of tunnel-slag-improved soils at the content of 15% was conducted. It also reported the long-term subgrade settlements. The feasibility of utilization of tunnel slag in improving properties of high liquid limit soils was further validated. Finally, a good application of tunnel-slag-improved high liquid limit soil as subgrade filling materials in Liyu highway was achieved. The findings in this study could provide useful guidance for similar engineering.
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Li, Chi, and Yu Gao. "Experimental Studies on Wind Erosion Mechanism of Aeolian Soils Subgrade Slope for Desert Highway." Advanced Materials Research 243-249 (May 2011): 2401–8. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2401.
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Wind erosion mechanism is studied through interior wind erosion wind tunnel experiment for desert highway. The anti-wind erosion ability of Aeolian soil subgrade slope is equivalent to the variation of microstructure characteristics and shearing strength of Aeolian soil. Microstructure characteristics will be quantified analysis through scanning electron microscope and image analysis software for subgrade slope, and microstructure parameters are picked-up for wind erosion fore-and-aft. Aeolian soil’s Shearing strength and wind erosion depth are investigated at different position of windward slope during a long-time wind-blown. Then, wind erosion mechanism of Aeolian soils subgrade slope is clarified from two aspects of micro and macro, wind erosion influence depth is determined for certain environmental condition. Taking desert highway subgrade as an example, the results indicate that: the disturbance to the flow field enhances with the increase of slope ratio and subgrade height, wind erosion of the windward slope is severe. The anti-wind erosion ability on windward slope is weak obvious with the decreasing of soil’s water containing, the increasing of wind velocity and the blow time prolong. Shearing strength of Aeorian soil is gradually decreased from slope surface to its interior, from bottom to top of windward slope. According to environmental condition local, when average wind velocity is 11m/s and natural water containing is 2%, wind erosion depth is about 15mm on the top of slope which is 1/11 of subgrade height, relative to 10mm on the mid of slope. The conclusions drawn from micro and macro are proved the wind erosion mechanism of Aeolian soils subgrade slope perfectly.
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Li, Jue, Jianlong Zheng, Yongsheng Yao, Junhui Zhang, and Junhui Peng. "Numerical Method of Flexible Pavement considering Moisture and Stress Sensitivity of Subgrade Soils." Advances in Civil Engineering 2019 (May 30, 2019): 1–10. http://dx.doi.org/10.1155/2019/7091210.
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Weaknesses of the subgrade structure induce the asphalt surface diseases and shorten the service life of flexible pavement. However, the resilient modulus (Mr) of subgrade soils is difficult to be evaluated directly since the subgrade is hidden and covered by the granular or asphalt layer. This study aimed to establish a numerical approach to predict the dynamic behavior of flexible pavements considering the stress sensitivity and moisture variation of subgrade soils. Firstly, 2D FEM simulations of flexible pavements were performed with half-sine loadings. A constitutive model of subgrade soils was proposed to incorporate soil suction and octahedral shear stress. It was validated using the laboratory triaxial test data of 3 selected soils. Then, the developed model was programmed by the user-defined material subroutine (UMAT) in the software ABAQUS. Subsequently, the validity of FEM model was verified by the laboratory tank model. Finally, the effect of moisture contents on the dynamic response of pavement structures was studied by tensile stress and vertical compressive strain. Results show that the surface deflection of the FEM model is similar to that of the actual pavement structure with the R2 of 98.44%. The developed UMAT program is reliable since the distribution of Mr in the FEM model is influenced by the stress and moisture condition of subgrade soils. When the moisture content is increased by 63%, the average Mr of subgrade soils is decreased by 18.7%. Meanwhile, the stiffness softening of subgrade soils increases vertical compressive strain at the top of the subgrade and the tensile stress at the bottom of the surface layer. It is interesting that the developed model can be applied to analyze the fatigue cracking of both subgrade and surface layers in the future.
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Omowumi, Ademila. "GEOTECHNICAL INFLUENCE OF UNDERLYING SOILS TO PAVEMENT FAILURE IN SOUTHWESTERN PART OF NIGERIA." Malaysian Journal of Sustainable Environment 4, no. 1 (September 30, 2018): 19. http://dx.doi.org/10.24191/myse.v4i1.5604.
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Roads in Nigeria are usually constructed without in-depth knowledge of the subsoil that serves as the foundation for the road elements. Road failures are often associated to poor construction materials or inadequate design without cognisance of the underlying soils. Engineering properties of ten bulk soil samples collected from the subgrade of Arigidi/Oke-Agbe highway were investigated to determine their suitability for highway pavement. Results show that all the subgrade soils below the failed locations have higher plasticity indices, which is an indication of their high swelling potential, and they are classified as A-7-6 clayey soils with high-water adsorption capability (16.1 – 22.4%) compared to subgrade soils from the stable locations. Low compacted density (1325 – 1928 Kg/m3), extremely poor CBR values; 8 – 31% (unsoaked) and 3 – 8% (soaked) which indicate percentage reduction in strength of the soils up to 77% on exposure to excessive moisture and the predominance of fines (> 59%) in the soils are responsible for the degree of instability. Furthermore, soft to low stiffness (49 – 131 kN/m2) and poor permeability of the subgrade materials underlying the pavement result to the failure characteristics witnessed. This study shows that the suitability and behaviour of subgrade soil is dependent on its engineering properties.
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Mahmoud Shallal, Dr Mohammed. "Sudan Subgrade Soils Characteristics." IOSR Journal of Engineering 4, no. 6 (June 2014): 48–56. http://dx.doi.org/10.9790/3021-04624856.
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Liu, Hong Xi, and Liang Zhou. "Regression Model for Resilient Modulus of Subgrade Soils in Shanghai." Advanced Materials Research 374-377 (October 2011): 1796–99. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.1796.
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Subgrade resilient modulus (MR) is very important for effective design of pavements. Several methods to estimate the resilient modulus were suggested in the past years. The main objective of this paper was to validate the correlation of MR with other physical properties of the subgrade soils. Cohesive soils representing major soil types in Shanghai were selected. The resilient modulus tests were conducted with UTM. Additional analysis was then performed to develop correlations between the model parameters and other soil properties. To verify the prediction models independently, laboratory MR tests were conducted on new subgrade soils. It was observed that the predicted MR values compared well with the laboratory measured values for the soil samples.
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Vynnykov, Yu L., and T. V. Lvovska. "MOISTURE CONDITIONS PATTERNS IN ROAD EMBANKMENT CLAY SOILS DEPTH." ACADEMIC JOURNAL Series: Industrial Machine Building, Civil Engineering 2, no. 49 (October 17, 2017): 227–33. http://dx.doi.org/10.26906/znp.2017.49.847.
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The article deals with optimal compaction criteria of road embankment soils improving, which provide their long-term strength. Physical experiment methodology for patterns establishment of water migration in subgrade embankment depth, in the capacity factors of what it is accepted: clay soil type (its number plasticity); moisture, at what the soil was compacted; soil skeleton density; embankment height; «rest» time after subgrade erection and before it’s operation are developed and realized. By laboratory and field tests water migration patterns in compacted subgrade soils depth are established. As a result of statistical processing of laboratory and field research results, the empirical dependence of compacted clay soil stabilized moisture for their multilayer consolidation in relation to soil skeleton density and plasticity number values is obtained.
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Sokolov, M. V., S. M. Prostov, and O. V. Gerasimov. "Numerical simulation of subgrade soil deformation properties for prediction of earthquake resistance of structures." Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 23, no. 3 (June 28, 2021): 167–78. http://dx.doi.org/10.31675/1607-1859-2021-23-3-167-178.
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Purpose: The aim of this paper is to predict the earthquake resistance in strengthening the subgrade soils of structures. Numerical simulation of the total increment of seismic intensity during the artificial transformation and strengthening of subgrade soils based on geomechanical modeling.Research methods: Classical mathematical methods for modeling subgrade soils in a plane nonlinear problem.Originality: A new approach is developed to determine the total increment of seismic intensity using the ratio between the subsidence values of building foundations and structures before and after soil strengthening. The paper presents the prediction results of changes in seismic resistance of real objects, based on engineering and geologi cal surveys and numerical computer models. It is shown that due to the transformation of subgrade soils, the earthquake resistance can be reduced by more than 0.5 points.Practical implication: This technique can be used to adjust the score for individual objects and map the boundaries of seismic zones.
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De Souza, Wana Maria, Antonio Júnior Alves Ribeiro, and Suelly Helena De Araújo Barroso. "Estimating the resilient modulus of subgrade materials using visual inspection." TRANSPORTES 30, no. 3 (December 14, 2022): 2738. http://dx.doi.org/10.14295/transportes.v30i3.2738.
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The definition of the Resilient Modulus (MR) of subgrade soils is essential for the reliable implementation of mechanistic-empirical pavement design. The MR of the soil is measured through repeated triaxial load tests which require expensive equipment and complex analyses. This reinforces the need to develop accurate statistical models for the prediction of the MR of the subgrade soil to be used for paving highways, especially in developing countries, such as Brazil, where financial resources are limited. The present study used artificial neural networks (ANNs) to create a model for the prediction of the MR of subgrade soils based on a visual-manual classification. For this, the results of MR tests conducted on samples of different soils from northeastern Brazil were used to develop an ANNs model for the prediction of the MR. The results demonstrate that ANNs can predict reliably the MR of soils, with a good degree of correlation in comparison with the laboratory test data. These findings support the use of the ANN model as a cost-effective approach for the preliminary evaluation of subgrade soils for highway pavement design in northeastern Brazil.
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Abdelmawla, Ahmad, and S. Sonny Kim. "Application of Ground Penetrating Radar to Estimate Subgrade Soil Density." Infrastructures 5, no. 2 (January 27, 2020): 12. http://dx.doi.org/10.3390/infrastructures5020012.
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Ground penetrating radar (GPR) technology has been widely used in pavement assessment over the last decade. Assessing the subgrade condition and monitoring its temporal variation provide valuable information regarding changes associated with pavement deterioration, allowing for the beneficial prediction of future road maintenance. This paper presents a method to estimate the density and water content of prepared subgrade soils of highly plastic silt using a 2 GHz GPR scan system and a simple exponential model. A bulk density prediction model was developed based on electromagnetic mixing theory to back calculate subgrade soils density. The model developed determines the soil’s dielectric constant, considering dielectric and volumetric properties of the three major components of soil: air, water, and solid particles. A series of laboratory tests was conducted on six (6) soil samples at various density levels to validate the newly developed model. For validation purposes, sand cone and dynamic cone penetration (DCP) tests were performed and compared with the estimated soils strength from GPR data. The results show that the prediction of soils density and stiffness using nondestructive technology helps efficiently forecast not only pavement deterioration, but potential risks to the subsurface pavement structure with all the advances of time saving using air coupled GPR antenna mounted on a moving vehicle.
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Degtyar, A. A., and A. M. Burgonutdinov. "REINFORCEMENT OF SUBGRADE DOUBLE-CONE PILES." Russian Journal of Building Construction and Architecture, no. 2(50) (May 21, 2021): 62–73. http://dx.doi.org/10.36622/vstu.2021.50.2.005.
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Statement of the problem. The problem of designing the reinforcement method of weak seasonally freezing soils in subgrade base by using double-cone hollow piles and geotechnical materials for roads in the northern regions of the Russian Federation is investigated. Results. As a result of the study, the construction of the subgrade in the form of pile strip foundation of double-cone piles reinforced by geotechnical materials on weak heaving soils taking into account traffic loads and weight of subgrade is considered. A method has been developed of calculating the road base in the form of pile strip foundation of double-cone piles reinforced by geotechnical materials on weak heaving soils taking into account traffic loads and weight of subgrade is considered. The developed method of calculation is based on the formation of soil compaction zones in the near-pile space as a result of pile driving into the ground, which leads to an increase in the structural strength of the weak soil, and also takes the arch effect that occurs in the soil between adjacent pile heads. Conclusions. The obtained research results allow us to conclude that the developed subgrade design and its calculation method are of great interest both to scientists and design engineers, and can be used in construction practice.
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Liu, Song-Yu, Guang-Hua Cai, Guang-Yin Du, Liang Wang, Jiang-Shan Li, and Xing-Chen Qian. "Field investigation of shallow soft-soil highway subgrade treated by mass carbonation technology." Canadian Geotechnical Journal 58, no. 1 (January 2021): 97–113. http://dx.doi.org/10.1139/cgj-2020-0008.
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The innovative carbonation technique based on reactive MgO and CO2 has been identified as an environmentally friendly and efficient method in the improvement of weak soils. Previous laboratory studies have indicated that carbonated MgO-admixed soils had significant improvement in mechanical properties. However, there are to date limited investigations on the soft-soil field application of this technique. In this study, a field trial was conducted to ascertain the feasibility of the MgO mass carbonation technique in improving shallow soft-soil subgrades. A series of field tests, including temperature, dynamic cone penetrometer, and light-weight deflectometer tests, were undertaken. The results indicated that compared with uncarbonated soil layers, there was two to three times increase in dynamic resilient moduli and soil resistances of carbonated MgO-admixed soils. The outcomes of this field investigation will contribute to the utilization of the combined stabilizer of MgO and CO2 and the mass carbonation technology in subgrade improvement.
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Do, Jinung. "Frost Heaving and Induced Pressure of Unsaturated Interfacial Zone between Gravel Ballast and Subgrade." Applied Sciences 12, no. 6 (March 9, 2022): 2811. http://dx.doi.org/10.3390/app12062811.
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Most existing railroads are composed of gravel ballast. One of the major issues with gravel ballast is frost damage in cold regions. Gravelly soils are known to be not prone to frost action due to their low water retention capacity and high hydraulic conductivity. However, reports indicated continued frost damages resulting from the mixed zone between gravel ballast and subgrade. This study evaluated the frost heaving and induced pressure of gravel ballast–subgrade soil mixtures via 1D soil column testing in a cold chamber. Gravel ballast and subgrade soil were collected from the railroad in situ. Various mixing ratios and degrees of saturation were used as factors affecting the frost experiments. The mixtures were placed in the cold chamber, and vertical displacements and pressures were measured. Overall evaluations showed that gravelly soils are not a geomaterial prone to frost damage; however, the frost potential of gravel ballast increases as the degree of saturation and the mixing portion of the subgrade soil increase. Therefore, the interfacial zone between gravel ballast and subgrade soil, especially where possible mixing with low drainage exists, needs cautions of potential frost damage.
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Vaiana, Rosolino, Cesare Oliviero Rossi, and Giusi Perri. "An Eco-Sustainable Stabilization of Clayey Road Subgrades by Lignin Treatment: An Overview and a Comparative Experimental Investigation." Applied Sciences 11, no. 24 (December 9, 2021): 11720. http://dx.doi.org/10.3390/app112411720.
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Subgrade conditions significantly affect functionality of the road pavement during its service life. Among the different stabilization techniques for upgrading poorly performing in-situ soil subgrades, an economically attractive example involves the use of waste materials, such as lignin. A deep bibliographic analysis of previous studies is carried out in the first section of this paper. The literature review suggests that use of lignin as a stabilizing agent of road subgrade soils is not completely consolidated. In addition, this study reports an investigation on the strength and performance characteristics of a lignin-treated clayey soil. Several experimental tests were carried out on both the untreated and lignin-treated soils in order to shed some light on different aspects with limited knowledge available, such as the behaviour of the stabilised soil in specific conditions (e.g., the presence of water). Finally, the test results are discussed and compared with those obtained when the same soil is treated with lime, which is more widely used. The most relevant finding is the poor ability of lignin to upgrade the bearing capacity of the soil in wet conditions compared to lime; on the contrary, the presence of lignin helped in controlling the swelling potential of this type of soil.
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Zhang, Jun Hui, Yu Zhou, and Jian Long Zheng. "Laboratory Test Method for Dynamic Rebound Modulus of Subgrade Red Clay in Moist-Heat Area." Applied Mechanics and Materials 477-478 (December 2013): 466–71. http://dx.doi.org/10.4028/www.scientific.net/amm.477-478.466.
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Ten representative expressway pavement structures in the southern humid area were investigated, and then the stress state of subgrade soil under the pavement structure was calculated and analyzed by multi-layer elastic system theory. Based on the latest research results at home and abroad, combined with the stress and physical properties of subgrade soils in south moist and heat area, the laboratory test method for dynamic rebound modulus of subgrade soil in this area was determined.
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Al-Samahiji, Despina, Sandra L. Houston, and William N. Houston. "Degree and Extent of Wetting Due to Capillary Rise in Soils." Transportation Research Record: Journal of the Transportation Research Board 1709, no. 1 (January 2000): 114–20. http://dx.doi.org/10.3141/1709-14.
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Increased water content of subgrade soils can lead to degradation of their quality and result in pavement distress. Pavement performance depends on the modulus of the compacted unsaturated subgrade soil as well as that of the underlying natural soil deposits. The soil modulus is a strong function of water content; therefore, changes in water content over the life of the pavement must be understood. In this study, it has been found that for a relatively near-surface groundwater table, significant potential exists for capillary rise into subgrade soils. For fine-grained soils in particular, the height of this capillary rise can be quite substantial. Results from capillary rise column experiments have shown that soils wetted above the groundwater table through capillary rise remain at a degree of saturation averaging about 60 percent. It has also been found that soil suction within this capillary zone must be determined through the use of soil water characteristic curves or direct measurement. The conventional assumption that negative pore water pressures can be estimated by backward extrapolation above the groundwater table of a line of slope γ w is only appropriate in a very thin region above the groundwater table, where soils are wetted to a degree of saturation of 85 percent or more.
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Efimenko, Vladimir N., Sergey V. Efimenko, and Alexey V. Sukhorukov. "Technology for Assignment of Predicted Behavior of Subgrade Soils in the Design of Road Pavements." Key Engineering Materials 683 (February 2016): 250–55. http://dx.doi.org/10.4028/www.scientific.net/kem.683.250.
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The paper discloses a technology for assignment of calculated values of moisture, strength, and deformability characteristics of clay subgrade soils. Main features of the geographical complex that determine the variability of characteristics of the water-and-thermal regime of subgrade soils are presented. Recommendations on assignment of calculated values of characteristics of the most common clay subgrade soils in the studied area are given.
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Kanciber, Yuriy, Valeriy Shtykov, Andrey Ponomarev, and Marina Vasil'eva. "Ways to Improve Hydrological Efficiency of Railway Subgrade Drainage." Proceedings of Petersburg Transport University 19, no. 3 (September 25, 2022): 411–20. http://dx.doi.org/10.20295/1815-588x-2022-3-411-420.
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Purpose: Hydrological rationale for drainage system buildings that effectively drain poorly permeable subgrade soils. As a result of watering of soils by rainfalls and groundwaters, track upper structure undergoes deformation and loses its strength. To exclude adverse processes, various drainage devices and drainage systems are used. In the modern world, traffic speed and freight transportation quantity have risen and the load on track superstructure has significantly increased. To reduce risk for drainage system buildings it is necessary to apply hydrological requirements to ensure moisturizing regime of subgrade soils. Methods: For new structures, traditional water-balance method for drainage efficiency assessment is used. The method takes into account two main types of moisturizing: atmospheric and mixed ones. For atmospheric watering, we used the data on water estimated inflow to a drainage in Russia North-West zone. Atmospheric nutrition may be absent in the case of geomembrane usage on subgrade major platform. The distance between collectors is determined by the author’s methodology obtained by an analytical method. Results: The new structure of gravel drain is proposed. It has been proven that the proposed structure in poorly permeable soils drains a subgrade more efficiently than a subditch drainage does. An example of a hydraulic calculation of such a drain is given, the distance between outlet collectors in the set conditions is determined. Practical significance: Due to the use of gravel drainage, subgrade soil moisture will decrease that will lead to the subgrade bearing capacity increase. The results can be used in poorly permeable soils which prevalence is quite high. Structures, including gravel drainage, can be applied in combination with traditional ones.
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Wang, Lin, Lixin Zhang, Tianliang Wang, and Shengjie Zhang. "Investigation of Water and Soil Migration and Mud Pumping of Subgrades under Traffic Load." Atmosphere 14, no. 1 (January 7, 2023): 133. http://dx.doi.org/10.3390/atmos14010133.
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Atmospheric precipitation leads to the increase of moisture in the subgrade. The moisture and soil migration in subgrade is a key scientific problem in evaluating the service performance of the subgrade and resolving or preventing mud pumping. Using a self-developed testing system as well as a numerical simulation model, a detailed study of the dynamic hydraulic characteristics, water migration mechanism, fine soil migration mechanism, and mud pumping properties of the subgrade was conducted. The results showed that water migrated into the upper layer of the subgrade under traffic load. Meanwhile, a pressure gradient for the pore water was generated in the subgrade. This kind of pressure gradient is beneficial for the moisture and fine soil migration. With rising groundwater level and increasing traffic load, the porosity of the subgrade soil differs at different depths. The fine soil migration is caused by water migration, which causes new migration channel for water in the subgrade. Then, a circulating system of moisture and fine soil is formed in the subgrade under a traffic load. After that, the upper layer subgrade soil is nearly saturated under the action of traffic load. Then, the nearly saturated soil liquefies instantaneously, becoming mud, under the action of traffic load. However, as the loading time progresses, the moisture and fine soil in the subgrade continue to migrate upward, resulting in the mud being pumped into the ballast and the gradual disappearance of liquefied soils at different depths.
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Lvovska, Tetyana, Tetyana Lytvynenko, and Alla Kariuk. "Soil Compaction Methods Development." International Journal of Engineering & Technology 7, no. 3.2 (June 20, 2018): 636. http://dx.doi.org/10.14419/ijet.v7i3.2.14605.
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A process of soil compaction methods development including new authors’ methodology is described. The importance of soil compaction for engineering purposes is substantiated. Preconditions for Proctor compaction test appearance are highlighted. Proctor’s approach and suggestions for the degree of soil compaction assessing are analyzed. Soviet version of Proctor’s equipment and Modified Proctor compaction test are given. Principal differences between Proctor test, Standard compaction test and Modified Proctor test are presented. The problems and disadvantages of existent soil compaction tests are revealed. New authors’ physical experiment methodology for patterns establishment of water migration in subgrade embankment depth, in the capacity factors of what it is accepted: clay soil type (its number plasticity); moisture, at what the soil was compacted; soil skeleton density; embankment height; «rest» time after subgrade erection and before it’s operation is developed and realized. By laboratory and field tests water migration patterns in compacted subgrade soils depth are established. As a result of statistical processing of research results, the empirical dependence of compacted clay soil stabilized moisture is obtained. Empirical dependence parameter corresponds to maximum molecular moisture capacity at what it is advisable to do the subgrade clay soils multilayer consolidation for their long-term strength ensuring.
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Sorsa, Alemineh, Sanjaya Senadheera, and Yoseph Birru. "Engineering Characterization of Subgrade Soils of Jimma Town, Ethiopia, for Roadway Design." Geosciences 10, no. 3 (March 1, 2020): 94. http://dx.doi.org/10.3390/geosciences10030094.
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Soils are naturally occurring materials that carry loads of civil engineering structures including roads and buildings. However, not all natural soils are suitable for such uses due to limited strength and instability under varying environmental conditions. A lack of adequate geotechnical investigations and soil characterization can result in the over-design of foundations, unexpected excavations to remove unsuitable soils, cost overruns, construction delays; and, contract disputes. In this research, an experimental plan was executed to determine the engineering properties of subgrade soil in Jimma Town in southwestern Ethiopia by using both disturbed and undisturbed soil samples. The plan included tests to determine the moisture content, specific gravity, grain-size analysis, Atterberg limits, compaction-density relationship, California Bearing Ratio (CBR), unconfined compression strength, and triaxial shear strength. X-ray diffraction (XRD) analysis was also conducted to determine the chemical composition of the soil. The soil characterization indicated that soft clay is the predominant subgrade soil type and that it has a very low load-bearing capacity, high plasticity, low strength and, high compressibility, which makes the soil unsuitable to serve as a highway subgrade without the help of soil improvement techniques.
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Puppala, Anand J., Louay N. Mohammad, and Aaron Allen. "Engineering Behavior of Lime-Treated Louisiana Subgrade Soil." Transportation Research Record: Journal of the Transportation Research Board 1546, no. 1 (January 1996): 24–31. http://dx.doi.org/10.1177/0361198196154600103.
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Lime stabilization is often used to treat subgrade soils when they are soft and cohesive in nature. A study was conducted to investigate the engineering behavior, including the resilient and strength behaviors, of a lime-treated subgrade soil. The lime treatment procedure was adapted from the specifications of the Louisiana Department of Transportation and Development. Silty clay, a soil often found in Louisiana subgrades, is used as a base soil. A summary of various engineering properties of a lime-treated soil from resilient modulus, unconfined compression strength, and California bearing ratio (CBR) tests conducted at five moisture content and dry density levels is provided. Tests were also performed on the raw soil without lime treatment, and these results were compared with those of tests with the lime-treated soil. The comparisons indicate that the present lime treatment method results in an increase in strength and resilient modulus properties and a decrease in plasticity characteristics and plastic strains. A regression model with three constants was used to analyze the resilient modulus test results. The model constants are presented as functions of soil properties. Resilient modulus correlations that use either CBR or unconfined compression strength, moisture content, dry density, degree of compaction, and stresses as dependent attributes are developed.
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Kamenchukov, Aleksey, Ilya Ukrainskiy, and Gamilia Nikolaeva. "Improving the stability of high embankment slopes on weak foundations." E3S Web of Conferences 244 (2021): 05018. http://dx.doi.org/10.1051/e3sconf/202124405018.
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The article considers the issues of assessing the stability of non-standard soil-geological systems in difficult conditions. An analytical review of modern methods and tools for assessing the stability of embankment slopes is carried out. The features of the work of the embankment in the areas of the spread of permafrost are considered. The features of the design of embankments on permafrost soils with the preservation or partial thawing of frozen soils have been studied. Two versions of the calculated static schemes of sliding surfaces are presented: base - subgrade and base - subgrade - pavement. Based on the results of field studies, the physical and mechanical characteristics of the soils of the embankment and the base of the subgrade were determined, which became the basis for mathematical modeling and assessment of the stability of the embankment slopes. In software packages GeoStab and Geo5, based on the finite element method and the results of field studies, digital models of embankments were built on a weak foundation. The calculation of the stability of the system “base - subgrade” under the action of a standard uniformly distributed load has been performed. Two models of the system and the base - subgrade - road surface are considered: without cracks on the rolling strip and with cracks. It was found that coating defects affect the stability of the system only in the presence of an earthquake of medium strength and more. Recommendations for strengthening the slopes of embankments operating in difficult soil-geological conditions are given.
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Tadesse Borku, Wondimagegn. "Stabilization Of Expansive Soil By Using A-1-B Soil In Subgrade Materials A Study In Boditi Town, Wolaita Zone, Southern Ethiopia." Journal of University of Shanghai for Science and Technology 24, no. 1 (January 23, 2022): 346–57. http://dx.doi.org/10.51201/jusst/22/0146.
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In road subgrade construction, all the naturally available material cannot be utilized as sub grade material as there exists some problematic soils such as expansive soils. The problematic nature of such soils can be improved by application of stabilizing agents. [11].A sub grade soil should fulfill the minimum requirement and soils with less bearing capacity and high swelling characteristics should be treated in order to use as a sub grade material [6]. Mechanical stabilization of problematic soils with local materialsis one of the cheapest methods of improving the soils in order to use as a subgrade material [9]. Thus, in this study stabilization of Expansive soil by taking the four samples test pits, because this soil is unsuitable to use as subgrade material. To achieve these objectives four soils sample pits were selected from different representative parts of the existing sub grade. To understand the basic characteristics of this soil and stabilization there were different field and laboratory tests such as field dry density, natural moisture content, particle size distribution, specific gravity, Atterberg limits (Liquid Limit and Plastic Limit), compaction (Optimum Moisture Content and Maximum Dry Density), CBR and CBR swelling potential tests were concerned. The test results showed that the Natural Moisture Content ranges from 15.40% to 20.50%, the field dry density ranges from 1.53 g/cc to 1.61 g/cc, percentage finer ranges from 87.23 % to 91.23 %, Specific Gravity ranges from 2.57 to 2.65, Liquid Limit ranges from 62.81% to 71.87%, Plasticity Index ranges from 37.97 % to 44.75%, Group Index ranges from 27 to 30, Optimum Moisture Content ranges from 20.38 % to 22.60 %, Maximum Dry Density ranges from 1.65 g/cc to 1. 68g/cc, CBR ranges from 2.20% to 2.75% and CBR swell ranges from 3.51 % to 3.94%. Based on these results the study area was soil classification under A-7-6and inorganic clays with high plasticity. according to AASHTO M145 and USCS soil classification system respectively.As the result indicates that the soil samples characterized as Expansive clay soil, and those were unsuitable to use as a subgrade material for pavement construction based on [10] manual specification; thus, stabilize by mechanical method of stabilization by local materials (A-1-b soil), with different percentages ratio (15%,20% and 25% of A-1-b soil) by weight, were used to get appropriate mixing ratio, finally it was found that 25% mixing of A-1-b soil were efficient to use those as a subgrade material.
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Bandara, Nishantha, Hiroshan Hettiarachchi, Elin Jensen, and Tarik H. Binoy. "Upcycling Potential of Industrial Waste in Soil Stabilization: Use of Kiln Dust and Fly Ash to Improve Weak Pavement Subgrades Encountered in Michigan, USA." Sustainability 12, no. 17 (September 3, 2020): 7226. http://dx.doi.org/10.3390/su12177226.
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The State of Michigan in the United States often encounters weak soil subgrades during its road construction and maintenance activities. Undercutting has been the usual solution, while a very few attempts of in-situ soil stabilization with cement or lime have been made. Compared to the large volume of weak soils that require improvement and the cost incurred on an annual basis, some locally available industrial byproducts present the potential to become effective soil subgrade stabilizers and a better solution from the sustainability perspective as well. The candidate industrial byproducts are Cement Kiln Dust (CKD), Lime Kiln Dust (LKD), and Fly Ash (FA), out of which only a fraction is currently used for any other secondary purposes while the rest is disposed of in Michigan landfills. This manuscript describes a laboratory investigation conducted on above industrial byproducts and/or their combinations to assess their suitability to be used as soil subgrade stabilizers in three selected weak soil types often found in Michigan. Results reveal that CKD or a combination of FA/LKD can be recommended for the long-term soil subgrade stabilization of all three soil types tested, while FA and LKD can be used in some soil types as a short-term soil stabilizer (for construction facilitation). A brief discussion is also presented at the end on the potential positive impact that can be made by the upcycling of CKD/LKD/FA on sustainability.
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Kim, Dong-Soo, Gi-Chul Kweon, and Kwang-Ho Lee. "Alternative method of determining resilient modulus of subgrade soils using a static triaxial test." Canadian Geotechnical Journal 38, no. 1 (February 1, 2001): 107–16. http://dx.doi.org/10.1139/t00-077.
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The resilient moduli (MR) of subgrade and subbase soils are very important properties in the analysis and design of a flexible pavement system. However, difficulties and complexities in performing cyclic MR testing and the high cost of the testing system have prevented the cyclic MR test from becoming a routine test. Therefore, the development of an alternative simple and reliable MR testing technique is essential to the application of the mechanistic design of a flexible pavement system. In this study, an alternative MR testing technique for subgrade soils was developed using a static triaxial compression (TX) test. For the development of the alternative testing method, the effects of strain amplitude, loading frequency, mean effective stress, and number of loading cycles on the resilient modulus of subgrade soils were fully investigated. Cyclic MR, static TX, and resonant column torsional shear tests were performed to evaluate the deformational characteristics. Synthetic specimens of known stiffnesses ranging from those of soft subgrade soils to those of subbase materials were developed, and all of the testing systems used in this study were calibrated. The alternative MR testing procedures were proposed considering deformational characteristics of subgrade soils. The reliability of the proposed test method was verified by comparing the moduli determined by the proposed alternative MR testing method with those determined by the standard MR tests.Key words: resilient modulus (MR), alternative MR test, subgrade soils, static triaxial test, deformational characteristics.
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Han, Zhong, and Sai K. Vanapalli. "Model for predicting resilient modulus of unsaturated subgrade soil using soil-water characteristic curve." Canadian Geotechnical Journal 52, no. 10 (October 2015): 1605–19. http://dx.doi.org/10.1139/cgj-2014-0339.
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Soil suction (ψ) is one of the key factors that influence the resilient modulus (MR) of pavement subgrade soils. There are several models available in the literature for predicting the MR–ψ correlations. However, the various model parameters required in the existing models are generally determined by performing regression analysis on extensive experimental data of the MR–ψ relationships, which are cumbersome, expensive, and time-consuming to obtain. In this paper, a model is proposed to predict the variation of the MR with respect to the ψ for compacted fine-grained subgrade soils. The information of (i) the MR values at optimum moisture content condition (MROPT) and saturation condition (MRSAT), which are typically determined for use in pavement design practice; (ii) the ψ values at optimum moisture content condition (ψOPT); and (iii) the soil-water characteristic curve (SWCC) is required for using this model. The proposed model is validated by providing comparisons between the measured and predicted MR–ψ relationships for 11 different compacted fine-grained subgrade soils that were tested following various protocols (a total of 16 sets of data, including 210 testing results). The proposed model was found to be suitable for predicting the variation of the MR with respect to the ψ for all the subgrade soils using a single-valued model parameter ξ, which was found to be equal to 2.0. The proposed model is promising for use in practice, as it only requires conventional soil properties and alleviates the need for experimental determination of the MR–ψ relationships.
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Muhanna, A. S., M. S. Rahman, and P. C. Lambe. "Model for Resilient Modulus and Permanent Strain of Subgrade Soils." Transportation Research Record: Journal of the Transportation Research Board 1619, no. 1 (January 1998): 85–93. http://dx.doi.org/10.3141/1619-10.
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The resilient modulus and cumulative permanent strain of subgrade soils under anticipated repeated loading are important considerations for the design of a pavement against fatigue and rutting failures. A simple model was developed to evaluate the resilient modulus and accumulated permanent strain of cohesive subgrade soils under repeated loads. The empirical model was derived from the observed behavior of an A-6 cohesive soil. The model was tested against an A-5 soil. The proposed model was found to predict adequately the resilient modulus and the accumulated plastic strain for all A-6 and A-5 specimens with 90 percent confidence intervals of 0.61 and 1.4, and 0.66 and 1.39, respectively.
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Shan, Wei, Min Ma, Ying Guo, and Chengcheng Zhang. "Numerical Analysis of the Influence of Block-Stone Embankment Filling Height on the Water, Temperature, and Deformation Distributions of Subgrade in Permafrost Regions." Water 14, no. 9 (April 24, 2022): 1382. http://dx.doi.org/10.3390/w14091382.
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The hydrologic and thermal states of foundation soils have an important influence on subgrade stability in degrading permafrost regions. However, thawing settlement remains a problem in the permafrost regions of Northeast China, because there are few relevant research results in this area, and the foundation deformation mechanism caused by the hydrologic and thermal changes of foundation soils is not clear. Therefore, a subgrade structure with large block stones as embankment filler was proposed to improve the foundation thawing settlement, and it has been successfully implemented in the road project (Yiershi–Chaiqiao section of 308 Provincial Highway) in Inner Mongolia Autonomous Region. To study the action mechanism of this structure on the subgrade deformation, a numerical model of the hydro–thermal–mechanical interaction process in unsaturated frozen soil was established, and the calculation of the water content, temperature, and deformation conditions of the subgrade within 20 years of the highway were carried out. The results show that the embankment block-stone layer can reduce the total heat of the deep foundation, and reduce the migration of unfrozen water from the deep foundation to the active layer. It can also increase the hydrologic and thermal convective flux inside and outside the block-stone layer, thus raising the permafrost table and reducing the subgrade deformation. The block-stone layer thickness has an important influence on the subgrade stability. By comparing the hydrologic, thermal change, and deformation of the block-stone structures with different thicknesses (5.0 m, 4.0 m, 3.5 m, 3.0 m, and 2.0 m), we found that when the thickness of the block-stone layer is 4.0 m, the subgrade stability is the best. In this case, the maximum uneven settlement and the maximum transverse deformation difference of the top surface of the subgrade are +0.521 cm and +0.462 cm, respectively. The subgrade stability is less optimal when the block-stone layer thickness is greater or less than 4.0 m. Thus, there exists an optimal embankment filling height related to the hydrologic and thermal conditions of the foundation soils. This study helps to elucidate the effect of unfrozen water content change on subgrade deformation during permafrost degradation and provides an important reference for solving the problem of thawing settlement of subgrade in permafrost regions.
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Shan, Wei, Min Ma, Ying Guo, and Chengcheng Zhang. "Numerical Analysis of the Influence of Block-Stone Embankment Filling Height on the Water, Temperature, and Deformation Distributions of Subgrade in Permafrost Regions." Water 14, no. 9 (April 24, 2022): 1382. http://dx.doi.org/10.3390/w14091382.
Full textAbstract:
The hydrologic and thermal states of foundation soils have an important influence on subgrade stability in degrading permafrost regions. However, thawing settlement remains a problem in the permafrost regions of Northeast China, because there are few relevant research results in this area, and the foundation deformation mechanism caused by the hydrologic and thermal changes of foundation soils is not clear. Therefore, a subgrade structure with large block stones as embankment filler was proposed to improve the foundation thawing settlement, and it has been successfully implemented in the road project (Yiershi–Chaiqiao section of 308 Provincial Highway) in Inner Mongolia Autonomous Region. To study the action mechanism of this structure on the subgrade deformation, a numerical model of the hydro–thermal–mechanical interaction process in unsaturated frozen soil was established, and the calculation of the water content, temperature, and deformation conditions of the subgrade within 20 years of the highway were carried out. The results show that the embankment block-stone layer can reduce the total heat of the deep foundation, and reduce the migration of unfrozen water from the deep foundation to the active layer. It can also increase the hydrologic and thermal convective flux inside and outside the block-stone layer, thus raising the permafrost table and reducing the subgrade deformation. The block-stone layer thickness has an important influence on the subgrade stability. By comparing the hydrologic, thermal change, and deformation of the block-stone structures with different thicknesses (5.0 m, 4.0 m, 3.5 m, 3.0 m, and 2.0 m), we found that when the thickness of the block-stone layer is 4.0 m, the subgrade stability is the best. In this case, the maximum uneven settlement and the maximum transverse deformation difference of the top surface of the subgrade are +0.521 cm and +0.462 cm, respectively. The subgrade stability is less optimal when the block-stone layer thickness is greater or less than 4.0 m. Thus, there exists an optimal embankment filling height related to the hydrologic and thermal conditions of the foundation soils. This study helps to elucidate the effect of unfrozen water content change on subgrade deformation during permafrost degradation and provides an important reference for solving the problem of thawing settlement of subgrade in permafrost regions.
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Gorodnova, Elena, Anastasiya Minchenko, and Ekaterina Suvorova. "The study of sandy soils density in the subgrade of road embankment when compacted by explosions of elongated charges." Proceedings of Petersburg Transport University, no. 3 (September 20, 2018): 371–79. http://dx.doi.org/10.20295/1815-588x-2018-3-371-379.
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Objective: To create a solid subgrade for highways and railways fulfillment. Methods: Drilling and blasting technology with vertical sand drains formation and explosion energy use was applied. The method in question assumes acceleration of weak organic soils consolidation and loose sands ompaction in the subgrade of the road embankment. Results: Research work was carried out to reduce deformations in the road embankment during the high-speed road construction. Based on the research data, the porosity coefficient and the density index of the sand layer, being the subgrade of the road embankment, were obtained. The article presents a comparison between the results calculated before and after the work. Practical importance: When comparing the results of cone penetration test in soil, obtained at different stages of work, the conclusion was made that the sands in the subgrade of the road embankment were compacted. This fact implies that the application of drilling and blasting technology at sand drains formation results both in weak soils stabilization and also in loose sands compaction. The range of conducted works provides durability and stability in the subgrade of the road embankment.
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Ji, Richard, Nayyarzia Siddiki, Tommy Nantung, and Daehyeon Kim. "Evaluation of Resilient Modulus of Subgrade and Base Materials in Indiana and Its Implementation in MEPDG." Scientific World Journal 2014 (2014): 1–14. http://dx.doi.org/10.1155/2014/372838.
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In order to implement MEPDG hierarchical inputs for unbound and subgrade soil, a database containing subgradeMR, index properties, standard proctor, and laboratoryMRfor 140 undisturbed roadbed soil samples from six different districts in Indiana was created. TheMRdata were categorized in accordance with the AASHTO soil classifications and divided into several groups. Based on each group, this study develops statistical analysis and evaluation datasets to validate these models. Stress-based regression models were evaluated using a statistical tool (analysis of variance (ANOVA)) andZ-test, and pertinent material constants (k1,k2andk3) were determined for different soil types. The reasonably good correlations of material constants along withMRwith routine soil properties were established. Furthermore, FWD tests were conducted on several Indiana highways in different seasons, and laboratory resilient modulus tests were performed on the subgrade soils that were collected from the falling weight deflectometer (FWD) test sites. A comparison was made of the resilient moduli obtained from the laboratory resilient modulus tests with those from the FWD tests. Correlations between the laboratory resilient modulus and the FWD modulus were developed and are discussed in this paper.
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Vaillancourt, Michel, and Daniel Perraton. "Impact of subgrade soils on pavement roughness." Canadian Geotechnical Journal 53, no. 4 (April 2016): 687–95. http://dx.doi.org/10.1139/cgj-2015-0131.
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To highlight the impact of subgrade soil variability on the pseudo-profile and roughness at the end of road construction, a research program has been carried out at the Laboratoire sur les chaussées et matériaux bitumineux at École de technologie supérieure (ÉTS). The analysis is intended to highlight the variability of materials’ characteristics according to the longitudinal and vertical axes of the road. The proposed approach aims to calculate potential settlement variations through a global numerical simulation of a road section, in a bid to identify the expected pseudo-profile and to quantify the roughness quality by calculating the international roughness index (IRI). The proposed methodology was tested at a new road construction project in Québec. Here, the results of the simulations are compared to the details of the actual pseudo-profile obtained at the end of road construction for the project under study. It is shown, through the finite difference modeling of the mechanical behavior of the subgrade soil (FLAC calculation code), that the long wavelength pseudo-profile of the road at the end of construction can be determined, and that it is strongly influenced by subgrade soil variability. This article presents a second analysis carried out by Vaillancourt and Perraton in 2015 as part of a study of the impact of subgrade soils on pavement roughness.
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Fang, Rui, Hui Gao, and Xiang Qin Bian. "Three-Stage Permanent Deformation Behavior of Subgrade Soils." Advanced Materials Research 374-377 (October 2011): 1942–46. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.1942.
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The development of the permanent deformation of subgrade soils under repeated load tests may consists of three stages, namely the primary, secondary and tertiary stages, but the existing models can not describe this behavior very well, so a new model is required to be developed. Based on the creep equation of the soil under static load, a mechanistic model is developed to describe the development of the permanent deformation of the soil under repeated load tests. Triaxial repeated load tests are conducted for silty soils and results show that, under some conditions, the development of the permanent deformation of silty clay consists of three stages and the number of load repetitions corresponding to the initiation of the tertiary stage is 330,0000. The new model is used to fit the test results and the comparison of test results and fitting results prove that this model can describe all three stages of permanent deformation.
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Jankowski, Wojciech, and Juliusz Sołkowski. "The modelling of railway subgrade strengthening foundation on weak soils." Open Engineering 12, no. 1 (January 1, 2022): 539–54. http://dx.doi.org/10.1515/eng-2022-0053.
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Abstract As a consequence of increased axle loads and speeds of trains on modernised railway lines, there may occur problems with bearing capacity and stability of the subgrade in some sections of the railway network. This is the situation we are dealing with right now on the Polish State Railways network. Therefore, as a case study, a fragment of an existing railway embankment based on a weak foundation was chosen for the analysis of train–track–subgrade interaction. A two-stage train–track–subgrade model has been developed. The model consists of the upper part (train–track) and the lower part (subgrade-foundation). The first part is modelled as a self-contained system of differential equations which are solved by means of finite difference method and yield the stress levels on the subgrade. These stresses are treated as a load for the lower system modelled using FEM. The model has been validated using experimental data from literature, authors’ measurements, and railway staff measurements of the track geometry. Several cases of strengthening methods were calculated and compared with measurements on the railway section under consideration. Good agreement between the prediction and the measurement was found. The novelty of the model is including the heterogeneity of the subgrade, the strengthening methods, and very deep layers of its foundation as well as adding the influence of vibration on the weakening of soils. It was found that this influence is noticeable and should be included in the prediction of railway subgrade behaviour
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Churilin, V. S., and G. V. Pushkareva. "Soil genetics in its complex stabilization." Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 23, no. 6 (December 26, 2021): 190–200. http://dx.doi.org/10.31675/1607-1859-2021-23-6-190-200.
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The problem of the inter-repair time of automobile roads in Russia can be solved by the reinforcing the subgrade soils with cement. Soil is a multicomponent system affecting the deformation and strength properties of the composition (cement and soil). The cement-soil composition has drawbacks, especially in seasonal freezing regions, which affects its durability.In order to increase the composition efficiency, the Nicoflok polymer-mineral additive is used to strengthen subgrade with cement. However, the influence of the type regional and genetic soil on strength properties of the cement-soil + Nicoflok composition is yet studied.The paper presents the factor analysis of the influence of soil genetics on the composition strength properties. The study of the multicomponent system includes the response surface of the soil genetics on the strength properties of the composition. Additional studies are required to move from the qualitative evaluation of the soil genetics on the composition (cement-soil + Nicoflok) to the quantitative evaluation. These studies must be carried out according to a single scheme, which regards the seasonal freezing of subgrade soils in the northern regions of European Russia and West Siberia.
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Manosuthkij, Thammanoon, Anand J. Puppala, Soheil Nazarian, Sireesh Saride, and Laureano Hoyos. "Comparisons between Field and Laboratory Suction Measurements of Expansive Clays." Transportation Research Record: Journal of the Transportation Research Board 2053, no. 1 (January 2008): 39–46. http://dx.doi.org/10.3141/2053-06.
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Field suction measurements are especially important for pavements constructed on unsaturated expansive soils. Because these subgrade soils can experience high suction during dry seasons, field sensors that can measure high soil suctions are necessary. In this research, thermal conductivity-based soil suction sensors were evaluated for matric suction measurements at several sites. Laboratory suction measurements with the filter paper method were compared with the field suction measurements with the sensors. Soil water characteristic curves derived from the laboratory and field measurements agreed closely. Volume change measurements using swell and shrinkage tests were conducted separately on the subgrade soils retrieved from the instrumented test sites. The laboratory and field suction data need an adjustment or shift of the time factor to obtain comparable values at high suctions. The influence of total suction on the volumetric swell and shrinkage characteristics of the field subsoils were also addressed.
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Karimov, E. M. "IMPACT OF WATER AND TEMPERATURE CONDITIONS ON SUBGRADE IN ROAD-BUILDING CLIMATIC ZONE V IN KYRGYZSTAN." Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 22, no. 1 (February 27, 2020): 193–204. http://dx.doi.org/10.31675/1607-1859-2020-22-1-193-204.
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This paper presents research results of subgrade deformations leading to the loss of road stability on the Osh-Isfana road section in the South of Kyrgyzstan. The soil humidity of the sloping subgrade area occurs due to precipitation, so the paper considers the relationship between the subgrade settlement and atmospheric precipitation in the road-climatic zone V. The influence of the soil humidity on its physical and mechanical properties are determined as well as the critical values of humidity for each investigated area, when deformation can occur. The geological structure and parameters of physical and mechanical properties of soils are determined in the road section at issue. Subgrade settlement is evaluated and predicted in this work. The results can be used in road design and reconstruction with regard to the geological conditions of the Kyrgyz Republic.
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Yoka Khail, Bilal, Mathilde Morvan, and Pierre Breul. "Behavior of unsaturated pelitic soil in a railway context." E3S Web of Conferences 195 (2020): 01010. http://dx.doi.org/10.1051/e3sconf/202019501010.
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As part of the rehabilitation work on the Gabonese railway line, the Trans-Gabon Railway, it was necessary to analyse the behaviour of the materials constituting the subgrade soil. These soils are pelitic soils whose behaviour under unsaturated conditions and cyclic loading has not been studied before and which present differential settlements and lack of bearing capacity. In this article, we focus on the characterization of the subgrade soil. The objective of this work is first to determine the in-situ characteristics of the pelitic soil and be able to link these characteristics with the behaviour studied in laboratory. For that purpose, we propose an in-situ investigation based on the use of light dynamic penetrometric tests in order to assess the variability of the subgrade layer and a drying-wetting test to assess the influence of hydric stress on the drainage path of the studied soil. We present the results of in-situ tests performed on a study area. We also present the results of the tests to determine the soil water characteristic curves (SWCC) and the curves describing the volumetric behaviour of this soil when exposed to drying.
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Wright, Jason, S. Sonny Kim, Mi G. Chorzepa, and Stephan A. Durham. "Utilization of Large-Scale Rolling-Wheel Tester to Investigate the Stress Reduction in Pavement Layers Due to the Use of Geosynthetic Materials." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 2 (February 2019): 445–55. http://dx.doi.org/10.1177/0361198119827909.
Full textAbstract:
In a geosynthetic-reinforced pavement system, the load-bearing capacity of subgrade soil is improved by the lateral distribution of vertical stresses at the reinforcing layer. Under small-scale triaxial testing, the tensile properties of the geosynthetic are difficult to measure. Therefore, it is desirable to conduct large-scale testing to accurately monitor the behavior of geosynthetic-reinforced pavement foundations when subjected to rolling-wheel loadings. This study investigates the behavior of geosynthetic-reinforced pavement foundation systems through large-scale rolling-wheel tests performed with problematic subgrade soils found in north Georgia. Sixteen large-scale specimens were constructed of which twelve were reinforced with geosynthetic. Subgrade soils were compacted either at their optimum moisture content or at a higher than optimum moisture content to produce different California Bearing Ratios during specimen preparation. Both an extruded biaxial geogrid and woven geotextile were placed at various locations to investigate the optimal placement locations for different subgrade conditions. Pressure sensors were installed near the bottom of the aggregate base layer and near the top of the subgrade layer to monitor the variations in vertical stress within the pavement system under rolling-wheel load. Further, light weight deflectometer measurements were collected post-test to determine the effect of the geosynthetic on pavement foundation stiffness. The vertical pressure at the bottom of the aggregate base and top of subgrade decreased on average approximately 15.3% and 18.8%, respectively. The results indicate which type of geosynthetic and placement location provides the greatest reduction of pressure for each of the given subgrade conditions.
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Дегтярь, А. А., and А. М. Бургонутдинов. "REINFORCEMENT OF SUBGRADE DOUBLE-CONE PILES." НАУЧНЫЙ ЖУРНАЛ СТРОИТЕЛЬСТВА И АРХИТЕКТУРЫ, no. 1(61) (March 25, 2021): 75–85. http://dx.doi.org/10.36622/vstu.2021.61.1.007.
Full textAbstract:
Постановка задачи. Рассматривается разработка способа усиления конструкции земляного полотна двухконусными сваями и геотехническими материалами для дорог северных регионов Российской Федерации. Результаты. Создана конструкция земляного полотна на усиленном двухконусными сваями грунтовом основании с армированием геотехническими материалами. Разработан метод расчета конструкции земляного полотна на усиленном двухконусными сваями грунтовом основании с армированием геотехническими материалами, а также на слабых сезоннопромерзающих грунтах с учетом нагрузок при движении транспорта и веса земляного полотна. Данный метод расчета основан на образовании зон уплотнения грунта в околосвайном пространстве в результате внедрения свай в грунт, что приводит к увеличению структурной прочности слабого грунта, а также учитывает арочный эффект, возникающий в грунтах между соседними головами свай. Выводы. Разработанная конструкция земляного полотна и ее метод расчета представляют большой интерес как для научных работников, так и для инженеров-проектировщиков, и могут быть использованы в строительной практике. Statement of the problem. The problem of designing the reinforcement method of weak seasonally freezing soils in subgrade base by using double-cone hollow piles and geotechnical materials for roads in the northern regions of the Russian Federation is investigated. Results. As a result of the study, the construction of the subgrade in the form of pile strip foundation of double-cone piles reinforced by geotechnical materials on weak heaving soils taking into account traffic loads and weight of subgrade is considered. A method has been developed of calculating the road base in the form of pile strip foundation of double-cone piles reinforced by geotechnical materials on weak heaving soils taking into account traffic loads and weight of subgrade is considered. The developed method of calculation is based on the formation of soil compaction zones in the near-pile space as a result of pile driving into the ground, which leads to an increase in the structural strength of the weak soil, and also takes the arch effect that occurs in the soil between adjacent pile heads. Conclusions. The obtained research results allow us to conclude that the developed subgrade design and its calculation method are of great interest both to scientists and design engineers, and can be used in construction practice.
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Tan, Feng, and Tai Quan Zhou. "Finite Element Analysis for Subgrade Consolidation Settlement in Soft Soil." Applied Mechanics and Materials 448-453 (October 2013): 1256–59. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.1256.
Full textAbstract:
The two-dimensional finite element model for subgrade consolidation settlement analysis within soft soil pile is developed using ABAQUS. The numerical simulation on a highway subgrade deformation is performed to study the variation of consolidation settlement and the excess pore water pressure distribution in the central location and the part under centerline of the embankment. The results show that settlement develops gradually with the increasing period of soil consolidation. The excess pore water pressure of deep subgrade soils under embankment centerline rise due to the increased load. After each soil layer was filled, the excess pore water pressure increased in the first and was stable later along with the increase of soil depth. After the embankment soil was filled completely, excess pore pressure dissipated with time developing until the completion of consolidation.
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Ahmed, Asif, Md Jobair Bin Alam, Md Azijul Islam, and MD Sahadat Hossain. "Comparison of numerical modeling results from laboratory and field obtained unsaturated flow parameters." MATEC Web of Conferences 337 (2021): 02008. http://dx.doi.org/10.1051/matecconf/202133702008.
Full textAbstract:
Moisture and suction variation beneath pavement contribute significantly to the volumetric deformation of expansive subgrade in response to climatic loading. In order to quantify the damage due to climatic loading, estimation of moisture, and suction variation in pavement subgrade is of paramount importance. The objective of the current study is to investigate the moisture and suction variation in response to precipitation events with the aid of numerical modeling in the unsaturated pavement subgrade. In unsaturated soils where the voids are filled with both water and air, the SWCC describes the volume of the voids that remain filled with water as the soil drains pore water. The SWCC has been identified as the vital soil information required to analyze seepage, stability, and volume change problems involved in unsaturated soils. However, the selection of unsaturated flow parameters is typically laboratory-based which represents specific conditions rather than a dynamic scenario of the field. In this study, an attempt was undertaken to conduct numerical modeling using field generated unsaturated flow parameters along with five other predictive models. Results indicated the distinct variation of moisture and suction distribution in subgrade from the same rainfall event while using laboratory versus field generated SWCC unsaturated flow parameters. In addition, predicted model yielded output was also varying with the field generated parameters’ output. Instead of using laboratory-generated static parameters, it was found that field generated dynamic unsaturated flow parameters were able to capture better suction variation at the pavement subgrade.
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Ou, Ou, Xin Gui Zhang, and Nian Ping Yi. "The Experimental Study on Strength of Subgrade Soil Treated with Liquid Stabilizer." Advanced Materials Research 194-196 (February 2011): 985–88. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.985.
Full textAbstract:
The liquid soil stabilizer technology is a chemically modified method that can stabilize or reinforce those soils with weak engineering properties. In this paper, two typical high liquid limit soils ，which can not be directly used as subgrade materials，were treated with a new soil stabilizer and it were processed that serials of comparison test on the main engineer properties of soil that pre-and post-treated with soil stabilizer. Then the results show that the soil liquid stabilizer is effective to improve strength and moisture susceptibility for two selected soils. The liquid soil stabilizer technology opened up a new approach for soil improvement and ground treatment.