A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a...A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100-200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.展开更多
The modulus of soil reaction,representing the stiffness of a soil surrounding pipes,is a critical parameter in the design of buried flexible pipes.This study conducted plate loading tests on corrugated polyvinyl chlor...The modulus of soil reaction,representing the stiffness of a soil surrounding pipes,is a critical parameter in the design of buried flexible pipes.This study conducted plate loading tests on corrugated polyvinyl chloride,smooth polyvinyl chloride,and high-density polyethylene pipes buried in lightweight cellular concrete(LCC)backfills at densities of 400,475,550,and 650 kg/m^(3)to investigate the pipe deformation behavior and moduli of soil reaction.In addition,this study examined the effects of the narrow trench condition on the pipe deformation and modulus of soil reaction.In these tests,the vertical and horizontal diameter changes of pipes under the vertical pressures applied through a hydraulic jack were measured.Test results reveal that the average moduli of soil reaction of plastic pipes within a wide trench backfilled by the LCCs at densities of 400,475,550,and 650 kg/m^(3)were back-calculated as 66,99,133,and 205 MPa,respectively,using the modified Iowa formula.Furthermore,the back-calculated moduli of soil reaction for LCCs exhibited linear relationships with their densities and unconfined compressive strengths and were higher than the recommended values for the commonly used soil backfills.Based on the vertical deformation criterion of 5%pipe diameter,the ultimate bearing capacities of flexible pipes buried in wide LCCs at densities of 475,550,and 650 kg/m^(3)exceeded 500 kPa.The LCC with a narrow trench exhibited a lower modulus of soil reaction and ultimate bearing capacity but a larger pipe diameter change.展开更多
Site conditions,including geotechnical properties and the geological setting,influence the near-surface response of strata subjected to seismic excitation.The geotechnical parameters required for the design of foundat...Site conditions,including geotechnical properties and the geological setting,influence the near-surface response of strata subjected to seismic excitation.The geotechnical parameters required for the design of foundations include mass density(ρ),damping ratio(β_(s)),shear wave velocity(V_(s)),and soil shear modulus(G_(s)).The values of the last three parameters are sensitive to the level of nonlinear strain induced in the strata due to seismic ground motion.In this study,the effect of variations in soil properties,such as plasticity index(PI),effective stress(σ′),over consolidation ratio(OCR),impedance contrast ratio(ICR)between the bedrock and the overlying strata,and depth of soil strata over bedrock(H),on seismic design parameters(β_(s),V_(s),and G_(s))was investigated for National Earthquake Hazards Reduction Program(NEHRP)site classes C and D,through 1D nonlinear seismic site response analysis.The Morris one-at-a-time(OAT)sensitivity analysis indicated thatβ_(s),V_(s),and G_(s)were significantly influenced by variations in PI,while ICR affectedβ_(s)more than it affected V_(s)and G_(s).However,the influence of H on these parameters was less significant.It was also found that variations in soil properties influenced seismic design parameters in soil type D more significantly than in soil type C.Predictive relationships forβ_(s),V_(s),and G_(s)were derived based on the 1D seismic site response analysis and sensitivity analysis results.Theβ_(s),V_(s),and G_(s)values obtained from the analysis were compared with the corresponding values in NEHRP to determine the similarities and differences between the two sets of values.The need to incorporate PI and ICR in the metrics for determiningβ_(s),V_(s),and G_(s)for the seismic design of foundations was highlighted.展开更多
基金Project(SWJT11ZT04)supported by the Central College Foundation of ChinaProject(2008g032-A)supported by the Major Projects S&T Foundation of China’s Ministry of Railways,China
文摘A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100-200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.
基金supported by the CEMATRIX Corp.The authors would like to thank technicians David Woody,Kent Dye,and Meyer Carey in the Civil,Environmental,&Architectural Engineering Department at the University of Kansas,for their great assistance in modifying and calibrating the test devices used in this studyThe authors also would like to appreciate Ph.D.student Alsharari Turki from the University of Kansas and formerly visiting student Hsin-Ming Wu at the University of Kansas,and Albert Fang from CEMATRIX for their great help on the model tests.Josh Beakley at the American Concrete Pipe Association provided valuable comments and suggestions for the data analysis of soil reaction modulus.
文摘The modulus of soil reaction,representing the stiffness of a soil surrounding pipes,is a critical parameter in the design of buried flexible pipes.This study conducted plate loading tests on corrugated polyvinyl chloride,smooth polyvinyl chloride,and high-density polyethylene pipes buried in lightweight cellular concrete(LCC)backfills at densities of 400,475,550,and 650 kg/m^(3)to investigate the pipe deformation behavior and moduli of soil reaction.In addition,this study examined the effects of the narrow trench condition on the pipe deformation and modulus of soil reaction.In these tests,the vertical and horizontal diameter changes of pipes under the vertical pressures applied through a hydraulic jack were measured.Test results reveal that the average moduli of soil reaction of plastic pipes within a wide trench backfilled by the LCCs at densities of 400,475,550,and 650 kg/m^(3)were back-calculated as 66,99,133,and 205 MPa,respectively,using the modified Iowa formula.Furthermore,the back-calculated moduli of soil reaction for LCCs exhibited linear relationships with their densities and unconfined compressive strengths and were higher than the recommended values for the commonly used soil backfills.Based on the vertical deformation criterion of 5%pipe diameter,the ultimate bearing capacities of flexible pipes buried in wide LCCs at densities of 475,550,and 650 kg/m^(3)exceeded 500 kPa.The LCC with a narrow trench exhibited a lower modulus of soil reaction and ultimate bearing capacity but a larger pipe diameter change.
基金This work was supported by Kuwait University,Research Grant No.EV01/15.
文摘Site conditions,including geotechnical properties and the geological setting,influence the near-surface response of strata subjected to seismic excitation.The geotechnical parameters required for the design of foundations include mass density(ρ),damping ratio(β_(s)),shear wave velocity(V_(s)),and soil shear modulus(G_(s)).The values of the last three parameters are sensitive to the level of nonlinear strain induced in the strata due to seismic ground motion.In this study,the effect of variations in soil properties,such as plasticity index(PI),effective stress(σ′),over consolidation ratio(OCR),impedance contrast ratio(ICR)between the bedrock and the overlying strata,and depth of soil strata over bedrock(H),on seismic design parameters(β_(s),V_(s),and G_(s))was investigated for National Earthquake Hazards Reduction Program(NEHRP)site classes C and D,through 1D nonlinear seismic site response analysis.The Morris one-at-a-time(OAT)sensitivity analysis indicated thatβ_(s),V_(s),and G_(s)were significantly influenced by variations in PI,while ICR affectedβ_(s)more than it affected V_(s)and G_(s).However,the influence of H on these parameters was less significant.It was also found that variations in soil properties influenced seismic design parameters in soil type D more significantly than in soil type C.Predictive relationships forβ_(s),V_(s),and G_(s)were derived based on the 1D seismic site response analysis and sensitivity analysis results.Theβ_(s),V_(s),and G_(s)values obtained from the analysis were compared with the corresponding values in NEHRP to determine the similarities and differences between the two sets of values.The need to incorporate PI and ICR in the metrics for determiningβ_(s),V_(s),and G_(s)for the seismic design of foundations was highlighted.
