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.
