Evaluation of strength and deformation characteristics of sandy gravels based on in situ freezing method

点击翻译按钮获取中文摘要

High-quality undisturbed samples of sandy gravel were obtained by in situ freezing methods from an alluvium deposit. The standard penetration test, the large diameter penetration test, and the seismic downhole test were made at the same site. The purpose of the investigation is to study the static and dynamic properties of undisturbed gravely soils in the laboratory, and to investigate their correlations with the index properties obtained from the in situ tests.Drained static tests and undrained cyclic tests were conducted on the samples to determine the static strength, the liquefaction resistance and the correlation of shear modulus and damping factors with shear strain. The test results together with those of previous studies have shown that the penetration resistances become less correlated with dynamic strength as the grain size increases, and that such trend is more significant for the SPT than for the LPT. The tendency indicated that correction should be made to measured penetration resistances to allow for the effect of the presence of large particles. Based on the finding, tentative correction factors are presented in terms of the mean grain size, and the correlation of dynamic strength was reevaluated with these values.. The corrected penetration resistances show good agreement with the dynamic properties, indicating the effectiveness of the proposed method of correction.The test results also indicated that there is a well-defined correlation between liquefaction resistance and shear modulus normalized with respect to minimum void ratio and confining pressure. Based on the finding, a simplified method is presented for estimating liquefaction resistance from shear wave velocity.