Gotowa bibliografia na temat „STRATIFIED SOFT SOIL”
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Zobacz listy aktualnych artykułów, książek, rozpraw, streszczeń i innych źródeł naukowych na temat „STRATIFIED SOFT SOIL”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Artykuły w czasopismach na temat "STRATIFIED SOFT SOIL"
1
Yang, Pingyuan, Jiasheng Zhang, Huihua Hu, Xiaoen Wu, Xianfa Cao, Yi Chang, Yufei Liu i Jin Xu. "Coefficient Analysis of Soft Soil Consolidation Based on Measurement of Stratified Settlement". Geotechnical and Geological Engineering 34, nr 1 (21.11.2015): 383–90. http://dx.doi.org/10.1007/s10706-015-9952-y.
Pełny tekst źródła
2
Fan, Ling, Zhize Xun i Shuquan Peng. "A Comparative Case Study on Drainage Consolidation Improvement of Soft Soil under Vacuum Preloading and Surcharge Preloading". Applied Sciences 13, nr 9 (8.05.2023): 5782. http://dx.doi.org/10.3390/app13095782.
Pełny tekst źródłaStreszczenie:
Based on an improvement project of soft soil ground in Zhuhai City on the Pearl River Delta, a comparative study on vacuum preloading and surcharge preloading was performed. The ground and stratified settlements, excess pore water pressure, and the degrees of consolidation of soft soil are analyzed, along with the horizontal displacement and soil strength. The results show that surcharge preloading results in smaller secondary consolidation settlements than vacuum preloading. Primary consolidation settlement quickly increases with increasing excess pore water pressure of less than −40 kPa in vacuum preloading, while also increasing between 20 kPa and 25 kPa in surcharge preloading. The sharp increase in the strata permeability coefficient will induce the increase in strata consolidation degree and has little effect on the ground consolidation degree. The surcharge preloading can be given priority to reduce the settlement foundation in the service stage.
3
Leite, Lorena, Paulo Maia i Aldo Farfán. "Three-dimensional numerical analysis of the generalized group effect in monitored continuous flight auger pile groups". Soils and Rocks 46, nr 2 (27.04.2023): e2023013722. http://dx.doi.org/10.28927/sr.2023.013722.
Pełny tekst źródłaStreszczenie:
The interaction mechanisms related to the group effect between piles and between pile groups significantly influence the soil-structure interaction process. This interaction causes the superposition of stresses and, in general, makes the pile group settlement different from the settlement of an isolated pile. The objective of the present paper is to evaluate the soilstructure interaction mechanisms of buildings with foundations of monitored continuous flight auger piles (CFA) in a stratified soil mass, with the presence of an intermediate soft soil layer. Hence, it is particularly analyzed the group effect between piles of a group and the group effect between all pile groups from a foundation of a study case instrumented by means of numerical modeling, considering the effect of the soft soil layer. The results show the significant group effect on displacements, showing the increase in settlement due to the overlapping of the tension bulbs of the piles and neighboring pile groups.
4
Wang, Jianxiu, Tianrong Huang i Dongchang Sui. "A Case Study on Stratified Settlement and Rebound Characteristics due to Dewatering in Shanghai Subway Station". Scientific World Journal 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/213070.
Pełny tekst źródłaStreszczenie:
Based on the Yishan Metro Station Project of Shanghai Metro Line number 9, a centrifugal model test was conducted to investigate the behavior of stratified settlement and rebound (SSR) of Shanghai soft clay caused by dewatering in deep subway station pit. The soil model was composed of three layers, and the dewatering process was simulated by self-invention of decompressing devise. The results indicate that SSR occurs when the decompression was carried out, and only negative rebound was found in sandy clay, but both positive and negative rebound occurred in the silty clay, and the absolute value of rebound in sandy clay was larger than in silty clay, and the mechanism of SSR was discussed with mechanical sandwich model, and it was found that the load and cohesive force of different soils was the main source of different responses when decompressed.
5
Petersen, S. O., C. C. Hoffmann, C. M. Schäfer, G. Blicher-Mathiesen, L. Elsgaard, K. Kristensen, S. E. Larsen, S. B. Torp i M. H. Greve. "Annual emissions of CH<sub>4</sub> and N<sub>2</sub>O, and ecosystem respiration, from eight organic soils in Western Denmark managed by agriculture". Biogeosciences 9, nr 1 (23.01.2012): 403–22. http://dx.doi.org/10.5194/bg-9-403-2012.
Pełny tekst źródłaStreszczenie:
Abstract. The use of organic soils by agriculture involves drainage and tillage, and the resulting increase in C and N turnover can significantly affect their greenhouse gas balance. This study estimated annual fluxes of CH4 and N2O, and ecosystem respiration (Reco), from eight organic soils managed by agriculture. The sites were located in three regions representing different landscape types and climatic conditions, and three land use categories were covered (arable crops, AR, grass in rotation, RG, and permanent grass, PG). The normal management at each site was followed, except that no N inputs occurred during the monitoring period from August 2008 to October 2009. The stratified sampling strategy further included six sampling points in three blocks at each site. Environmental variables (precipitation, PAR, air and soil temperature, soil moisture, groundwater level) were monitored continuously and during sampling campaigns, where also groundwater samples were taken for analysis. Gaseous fluxes were monitored on a three-weekly basis, giving 51, 49 and 38 field campaigns for land use categories AR, PG and RG, respectively. Climatic conditions in each region during monitoring were representative as compared to 20-yr averages. Peat layers were shallow, typically 0.5 to 1 m, and with a pH of 4 to 5. At six sites annual emissions of N2O were in the range 3 to 24 kg N2O-N ha−1, but at two arable sites (spring barley, potato) net emissions of 38 and 61 kg N2O-N ha−1 were recorded. The two high-emitting sites were characterized by fluctuating groundwater, low soil pH and elevated groundwater SO42− concentrations. Annual fluxes of CH4 were generally small, as expected, ranging from 2 to 4 kg CH4 ha−1. However, two permanent grasslands had tussocks of Juncus effusus L. (soft rush) in sampling points that were consistent sources of CH4 throughout the year. Emission factors for organic soils in rotation and with permanent grass, respectively, were estimated to be 0.011 and 0.47 g m−2 for CH4, and 2.5 and 0.5 g m−2 for N2O. This first documentation of CH4 and N2O emissions from managed organic soils in Denmark confirms the levels and wide ranges of emissions previously reported for the Nordic countries. However, the stratified experimental design also identified links between gaseous emissions and site-specific conditions with respect to soil, groundwater and vegetation which point to areas of future research that may account for part of the variability and hence lead to improved emission factors or models.
6
Tempa, Karma, Komal Raj Aryal, Nimesh Chettri, Giovanni Forte i Dipendra Gautam. "Sensitivity analysis of input ground motion on surface motion parameters in high seismic regions: a case of Bhutan Himalaya". Natural Hazards and Earth System Sciences 22, nr 6 (7.06.2022): 1893–909. http://dx.doi.org/10.5194/nhess-22-1893-2022.
Pełny tekst źródłaStreszczenie:
Abstract. Historical earthquakes demonstrate that strong motion characteristics and local soil condition, when coupled, significantly influence seismic site response. Interestingly, most of the Himalayan earthquakes depicted anomalous behavior per the site conditions historically. Being one of the most active seismic regions on earth, the eastern fringe of the Himalaya has observed many devastating earthquakes together with non-uniform damage scenarios. To quantify such anomalies, we evaluate surface motion parameters for a soft soil deposit located in the city of Phuentsholing in western Bhutan. Using one-dimensional site response analysis, the sensitivity of ground motion variation is estimated. This study accounts for the earthquakes of moment magnitudes 6.6 to 7.5 with a wide variation in peak ground acceleration (PGA). To dissect the characteristics of six inputted ground motions on eight local ground conditions, a sensitivity analysis is performed statistically. The statistical correlation of the response datasets and the linear regression model of the bedrock outcrop and the surface motion spectral acceleration along the stratified depth are examined to quantify the variation in surface motion parameters. The results highlight that the strong motions with PGA greater than 0.34 g demonstrate greater sensitivity, leading to some anomalies in response parameters, especially amplification. Similar results were obtained for the low PGA range (<0.1 g).
7
Liu, Shaodong, Shuxian Liu, Shasha Lu, Fenghai Ma i Ge Pei. "Seismic Behaviour of Shallow Tunnelling Method Tunnels Accounting for Primary Lining Effects". Buildings 13, nr 1 (22.12.2022): 20. http://dx.doi.org/10.3390/buildings13010020.
Pełny tekst źródłaStreszczenie:
The shallow tunnelling method (STM) is usually used to construct shallow tunnels buried in soft ground. It consists of primary lining and secondary lining (tunnel). In the seismic design of STM tunnels, it is usually assumed that the secondary lining (tunnel) is resistant to all seismic effects. However, the soil–primary–secondary lining system may generate complex interaction phenomena during ground shaking. Compared with the case where the primary lining is not considered, the existence of the primary lining alters the seismic response of the secondary lining (tunnel). The paper attempts to investigate this complex interaction, focusing on the response of the secondary lining (tunnel). The full dynamic time history analysis is adopted to investigate the interaction in the transversal direction. A case history of the Hohhot (China) arched STM tunnel buried in a stratified soil deposit has been analyzed. Two tunnel configurations for a two-dimensional plane strain model of STM tunnels in Hohhot are studied and compared, including a model with primary lining and one without primary lining. A numerical parametric analysis was conducted to elucidate critical response characteristics of STM tunnels. Salient parameters that may affect the dynamic response of the tunnel were studied, including the characteristics of ground motion, the characteristics of contact interface, the characteristics of the soil, and the characteristics of the tunnel lining. The response characteristics of the tunnel are compared and discussed, including horizontal acceleration, deformation mode, lining internal force, and lining damage. The results show that the primary lining has a significant influence on the magnitude and distribution of the seismic response, especially considering the nonlinearity of the soil and the nonlinear characteristics of the tunnel lining. The effect of primary lining on the seismic response is about 5%–35 %.
8
Petersen, S. O., C. C. Hoffmann, C. M. Schäfer, G. Blicher-Mathiesen, L. Elsgaard, K. Kristensen, S. E. Larsen, S. B. Torp i M. H. Greve. "Annual emissions of CH<sub>4</sub> and N<sub>2</sub>O, and ecosystem respiration, from eight organic soils in Western Denmark managed by agriculture". Biogeosciences Discussions 8, nr 5 (11.10.2011): 10017–67. http://dx.doi.org/10.5194/bgd-8-10017-2011.
Pełny tekst źródłaStreszczenie:
Abstract. The use of organic soils by agriculture involves drainage and tillage, and the resulting increase in C and N turnover can significantly affect their greenhouse gas balance. This study estimated annual fluxes of CH4 and N2O, and ecosystem respiration (Reco), from eight organic soils managed by agriculture. The sites were located in three regions representing different landscape types and climatic conditions, and three land use categories (arable crops, AR, grass in rotation, RG, and permanent grass, PG) were covered. The normal management at each site was followed, except that no N inputs occurred during the monitoring period from August 2008 to October 2009. The stratified sampling strategy further included six sampling points in three blocks at each site. Environmental variables (precipitation, PAR, air and soil temperature, soil moisture, groundwater level) were monitored continuously and during sampling campaigns, where also groundwater samples were taken for analysis. Gaseous fluxes were monitored on a three-weekly basis, giving 51, 49 and 38 field campaigns for land use categories AR, PG and RG, respectively. Climatic conditions in each region during monitoring were representative based on 20-yr averages. Peat layers were shallow, typically 0.5 to 1 m, and with a pH of 4–5. At six sites annual emissions of N2O were in the range 3 to 24 kg N2O-N ha−1, but at two arable sites (spring barley, potato) net emissions of 38 and 61 kg N2O-N ha−1 were recorded. Both were characterized by fluctuating groundwater with elevated SO42− concentrations. Annual fluxes of CH4 were generally small, as expected, ranging from –2 to 4 kg CH4 ha−1. However, two permanent grasslands had tussocks of Juncus effusus (soft rush) in sampling points that were consistent sources of CH4 throughout the year. Emission factors for organic soils in rotation and permanent grass, respectively, were estimated to be 0.011 and 0.47 g m−2 for CH4, and 2.5 and 0.5 g m−2 for N2O. This first documentation of CH4 and N2O emissions from managed organic soils in Denmark confirms the levels and wide ranges of emissions previously reported for this region. However, the factorial approach also identified links between gaseous emissions and site-specific conditions with respect to soil, groundwater and vegetation which point to areas of future research that may account for part of the variability and hence lead to improved emission factors or models.
9
Quintero-Chamorro, Jairo Alejandro, Brayan Julián Martínez-Ortega i Lucio Gerardo Cruz-Velasco. "Evaluation of Load Capacity of Stratified Soils (2 Layers) by Means of Numerical Analytical Comparison". Revista Facultad de Ingeniería 30, nr 55 (24.02.2021): e12080. http://dx.doi.org/10.19053/01211129.v30.n55.2021.12080.
Pełny tekst źródłaStreszczenie:
The methods for determining load capacity in stratified soils are numerous and differ in their methods and results. These differences in analysis lead to uncertainty in engineering practices or over-dimensioning of the foundation solution. This study seeks to determine three analytical methods of load capacity in stratified soils (2 layers) for shallow foundations: 1) Imaginary foundation, 2) Average parameter method (APM), and 3) Terzaghi's method to compare their results with those obtained from numerical modeling by means of the finite element method using a widely applied software (Abaqus academic version). Within the methodology developed in the finite element modeling, variables were parameterized (modulus of elasticity, depth of deflection, and displacement-load) and two behavioral laws were evaluated (Elastic and Drucker-Prager). The results that were obtained from the analysis show that when performing numerical modeling using the law of elastic behavior in soils of two layers, exaggerated results are generated with respect to analytical methods. Another important result is that when hard soils are on top of soft soils the results of numerical and analytical methods tend to be similar to each other. Most importantly, the variables that have the greatest influence on the load capacity in soils of one and two layers are the angle of friction, yield stress, and in the case of numerical analysis the constraint displacement (load). In addition, it was observed that for numerical modeling better results are obtained when considering an elastoplastic model, such as Drucker Prager.
10
Abd Razak, Muhammad Fikri. "Tahap Penguasaan Kemahiran Insaniah Pelajar Sekolah Menengah di Klang". ATTARBAWIY: Malaysian Online Journal of Education 3, nr 1 (30.06.2019): 69–80. http://dx.doi.org/10.53840/attarbawiy.v3i1.68.
Pełny tekst źródłaStreszczenie:
Malaysian Ministry of Education hopes that the curriculum and co-curricular activities will enhance the student's soft skills. The objective of the study was to determine the level of mastery of the student's soft skills and the difference in the mastery of the soft skills according to gender and race. The methodology used is a quantitative approach to answer three research questions. Data for this survey study was collected through a validated questionnaire. The sample of the study selected through stratified random sampling consists of 310 form four students from five selected schools around Klang. The data was analyzed using SPSS version 22.0. The findings indicate that the students’ level of soft skills mastery is at high level for the four subdimensions. The t-test of independent samples showed no difference between male and female students in the mastery of soft skills. However, one-way Anova Test shows that there is a significant difference in the mastery of soft skills according to students’ race. In conclusion, this study shows that the Malaysian education system succeeds in the development of student's soft skills. The implication of the study shows that the soft skills modules need to be built immediately so that the application of soft skills to the students becomes more systematic and effective.
Abstrak
Kementerian Pendidikan Malaysia mengharapkan kurikulum dan kegiatan kokurikulum dapat meningkatkan kemahiran insaniah pelajar. Objektif kajian adalah untuk menentukan tahap penguasaan kemahiran insaniah pelajar dan perbezaan penguasaan kemahiran insaniah mengikut jantina dan bangsa. Metodologi yang digunakan adalah pendekatan kuantitatif untuk menjawab tiga persoalan kajian. Data untuk kajian berbentuk tinjauan ini dikumpulkan melalui instrumen soal selidik yang telah divalidasi. Sampel kajian yang dipilih melalui persampelan rawak berstrata terdiri daripada 310 orang pelajar tingkatan Empat daripada lima buah sekolah terpilih di sekitar Klang. Data dianalisis menggunakan SPSS versi 22.0. Dapatan menunjukkan tahap penguasaan kemahiran insaniah pelajar berada pada tahap tinggi untuk keempat-empat subdimensi. Analisis ujian-t sampel tak bersandar menunjukkan tidak terdapat perbezaan antara pelajar lelaki dan perempuan dalam penguasaan kemahiran insaniah. Walau bagaimanapun, Ujian Anova Satu Hala pula menunjukkan terdapat perbezaan penguasaan kemahiran insaniah yang signifikan mengikut bangsa. Kesimpulannya, kajian ini menunjukkan bahawa sistem pendidikan Malaysia berjaya dalam pembentukan kemahiran insaniah pelajar. Implikasi kajian menunjukkan modul kemahiran insaniah perlu dibina dengan segera supaya penerapan kemahiran insaniah kepada pelajar menjadi lebih sistematik dan berkesan.
Rozprawy doktorskie na temat "STRATIFIED SOFT SOIL"
1
MIR, SADAF. "STUDY OF THE BEHAVIOUR OF STONE COLUMN IN LAYERED SOFT SOIL USING PLAXIS 2D". Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/20085.
Pełny tekst źródłaStreszczenie:
The study presents the results of numerical analysis conducted in unit cell configuration
to investigate the behavior of stone columns in stratified soils. Specifically, the study
focuses on the behavior of stone columns when the upper layer consists of weak soil,
while the underlying layer is a relatively stronger firm clay. The thickness of the top weak
layer is varied to understand its impact on the performance of the stone columns. Two
types of loading conditions were employed in the simulations. In the first condition, the
entire area of the unit cell area was loaded to estimate the stiffness of the improved
ground. In the second condition, only the stone column was loaded to determine the
limiting axial capacity. The simulations were run using a column with a diameter of 88
mm surrounded by layered soil, maintaining an area ratio of 22% (ratio of the area
occupied by stone columns to the total area). The study included the influence of the depth
of the top weak layer thickness on various aspects, including stiffness, load bearing
capacity, and bulging behavior of the stone columns. The findings indicate that the
thickness of the top weak layer has a significant influence on the behavior of stone
columns. The stiffness, load bearing capacity, and bulging behavior are all affected by
the depth of the top weak layer thickness. These results have practical significance in
understanding and optimizing the performance of stone columns as an effective and
economical ground improvement technique, particularly in soft grounds with layered soil
profiles.
Streszczenia konferencji na temat "STRATIFIED SOFT SOIL"
1
Ma, Hongliang, Mi Zhou, Yuxia Hu i Muhammad Shazzad Hossain. "Large Deformation FE Analyses of Cone Penetration in Single Layer Non-Homogeneous and Three-Layer Soft-Stiff-Soft Clays". W ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23709.
Pełny tekst źródłaStreszczenie:
Continuous profiles from in-situ penetrometer tests are now identified as essential for site specific soil investigation as part of designing offshore structures in deep and ultradeep waters and in highly layered seabed conditions. This paper describes the results from large deformation FE (LDFE) analysis undertaken to provide insight into the behavior of cone penetrometer penetrating through single layer non-homogeneous clays and three-layer uniform soft-stiff-soft clays. For the smooth cone penetration in non-homogeneous clays, the soil strength non-homogeneity factor was shown to have insignificant effect on the cone bearing capacity factor. However, for the rough cone, the bearing capacity factor in non-homogeneous clay was about 10∼12% lower than that in uniform clay. Bearing capacity factors for smooth and rough cones were also similar for non-homogeneous clay. For cone penetration in stratified soft-stiff-soft clays, a minimum layer thickness of 20 diameters was required to mobilise the full resistance of the stiff layer. The corresponding soil flow mechanisms are also discussed linking directly to the profile of penetration resistance.
2
Gao, Wen, Tom Harrup, Yuxia Hu i David White. "Effect of a Strong Middle Layer on Spudcan Penetration". W ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23925.
Pełny tekst źródłaStreszczenie:
The rapid penetration of one or more of the foundations of a mobile jack-up rig into the seabed is an ongoing major problem in the offshore industry, with the potential to cause major damage to the structure and endangering any personnel on board. A recent example is the jack-up drilling rig Perro Negro 6 incident happened near the mouth of the Congo river in July 2013 with one of the rig’s crew of 103 reported missing and six others injured. This uncontrollable displacement is due to a form of failure known as punch through failure and commonly occurs on stratified seabed profiles. It has been reported that unexpected punch-through accidents have resulted in both rig damage and lost drilling time at a rate of 1 incident per annum with consequential costs estimated at between US$1 and US$10 million [1]. This paper presents the bearing capacity profiles and associated soil flow mechanisms of a common spudcan foundation penetrating into a three layer soft-stiff-soft clay soil through the use of large deformation finite element (LDFE) analysis. The Remeshing and Interpolation with Small Strain (RITSS) [2, 3] technique was implemented in the software package AFENA [4] to conduct the LDFE analysis. Both soil layer thickness and soil layer strength ratios were varied to study their effect on the spudcan penetration responses. The LDFE results of spudcan penetration into the soft-stiff-soft clay soils were calibrated by existing centrifuge test data. A parametric study was then conducted to study the bearing capacity responses and soil flow mechanisms during spudcan large penetrations by varying the soil layer strength ratio and relative layer thickness to the diameter of spudcan. It was found that there were three types of bearing responses during continuous penetration of spudcan: (a) when the top soft layer is relatively thin, the spudcan bearing response was similar to that of two layer soils with stiff over soft clays; (b) when the top soil layer thickness is medium, a peak resistance is observed when spudcan penetrates into the middle stiff layer followed by reduction; (c) when the soil layer is thick, the peak resistance occurs when spudcan gets into the bottom soft soil layer. The critical thickness of top soil layer is a function of soil strength ratio and middle stiff soil layer thickness. The bearing response types were also corresponding to the soil cavity formations during spudcan initial penetration.
3
Mehryar, Zarnaz, i Yuxia Hu. "Numerical Study of Spudcan Foundation Penetrating Into Layered Soils". W ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67447.
Pełny tekst źródłaStreszczenie:
Spudcan foundation, penetrating into stratified soils is studied using H-adaptive finite element method (FE) together with Remeshing and Interpolation Technique with Small Strain model (RITSS). This is to investigate the potential hazard of punch-through failure in layered soil profiles. There are two series of analysis conducted. Firstly, for a pre-embedded spudcan foundation, a series of parametric studies has been undertaken in order to find the critical distance between the spudcan and the layer boundary, within which a punch-through failure is likely to occur. Soil profile is a uniform stiff clay layer overlaying a uniform soft clay layer with soil strength ratio (upper layer soil strength to lower layer strength) varying from 1 to 10. Secondly, continuous analysis has been undertaken for 2 cases with shear strength ratio of 2 and 3 and thickness of the upper stiff layer of one spudcan diameter. It is found that, in small strain analysis, the critical distance to the layer boundary is increasing with increasing the strength ratio. It reaches at a limit of 1.0 ∼ 1.25 D (D is the spudcan diameter) when the strength ratio is 5 or larger. In large deformation analysis, the critical distance is much lower than the one from small strain analysis. This is due to the trapped top layer soil underneath the spudcan, which cannot be simulated in small strain analysis.
4
Alves, João, Teresa Santana i Ildi Cismasiu. "Seismic performance of a RC building founded on soft stratified soils". W 1st Croatian Conference on Earthquake Engineering. University of Zagreb Faculty of Civil Engineering, 2021. http://dx.doi.org/10.5592/co/1crocee.2021.153.
Pełny tekst źródła
5
Gebregziabher, Henok F., i Rolf Katzenbach. "Parametric Studies on Application of CPRF on Semi Soft Stratified Soils". W GeoCongress 2012. Reston, VA: American Society of Civil Engineers, 2012. http://dx.doi.org/10.1061/9780784412121.014.
Pełny tekst źródła
6
Chin, King H., George Sheng, Manfred Zinserling i V. K. Kumar. "Seismic Design of Bulkhead and Foundation in Stratified Soft Clay and Liquefiable Soils". W Proceedings of Ports '13: 13th Triennial International Conference. Reston, VA: American Society of Civil Engineers, 2013. http://dx.doi.org/10.1061/9780784413067.124.
Pełny tekst źródła
7
Kavuri, Chaitanya, i Sage L. Kokjohn. "Computational Study to Identify Feasible Operating Space for a Mixed Mode Combustion Strategy: A Pathway for PCI High Load Operation". W ASME 2017 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icef2017-3668.
Pełny tekst źródłaStreszczenie:
Mixed mode combustion strategies have shown great potential to achieve high load operation but soot emissions were found to be problematic. A recent study investigating soot emissions in such strategies showed that delaying the load extension injection sufficiently late after the primary heat release makes the soot production dependent solely on the temperature field inside the combustion chamber and eliminates any dependence on mixing time and oxygen availability. The current study focuses on furthering this research to identify a feasible operating space to operate in and enable high load operation with this mixed mode combustion strategy. A PCI combustion event was achieved using a premixed charge of gasoline (early cycle injection) and a load extension injection of gasoline was added near top dead center. CFD modeling considering polycyclic aromatic hydrocarbon (PAH) chemistry up to pyrene was used to perform a full factorial design of experiments (DOE) to study the effects of premixed fuel fraction (fraction of total fuel that is premixed), load extension injection timing and exhaust gas recirculation (EGR). The early injection timings for EGR rates less than 40% showed a soot-NOx tradeoff which constrained operating with SOI timings before TDC. The late injection timings showed reductions in soot and NOx at the expense of gross indicated efficiency (GIE). GIE increased with increasing premixed fuel until the premixed fuel quantity reached 80% of the total fuel mass. Premixed fuel quantities higher than 80% resulted in an efficiency penalty due to increased wall heat transfer losses resulting from early combustion phasing. However, at premixed fuel quantities close to 80%, the peak pressure rise rate became the dominating constraint. This confined the feasible operating space to a premix fuel mass range of 70% to 80%. For this premix fuel mass range, the feasible operating space had two regions; one in the early SOI regime before TDC at EGR rates higher than 38% and the other in the late SOI regime (SOI > 15° ATDC) across the entire EGR space. The study was repeated by splitting the premixed fuel into an early cycle injection and a stratified injection with SOI timing of −70° ATDC. The ratio of fuel in the two injections was varied in the DOE. The results showed that adding a stratified injection increases the ignition delay due to in-cylinder equivalence ratio stratification and relaxes the pressure rise rate effect on the operating space. This allows operation at high premix fuel quantities of 70% and higher with EGR rates less than 40% which yields significant increase in GIE. It was also identified that by targeting the fuel from the stratified injection into the squish region, there is improved oxygen availability in the bowl for the load extension injection, which results in the reduction of soot emissions. This allows the load extension injection to be brought closer to TDC while meeting the soot constraint, which further improves the GIE. Finally, the results from the study were used to demonstrate high load operation at 20 bar and 1300 rpm.