Prediction of dynamic pore water pressure for calcareous sand mixed with fine-grained soil under cyclic loading

Abstract

To evaluate the effect of fine-grained soil (FS) on liquefaction resistance of calcareous sand (CS), a set of undrained cyclic triaxial experiments with stress-controlled method were conducted. The cyclic triaxial tests were performed with 1 Hz frequency at three effective confining pressure levels (100, 200, 300 kPa) and three cyclic stress ratio (CSR) levels (0.1, 0.2, 0.5). Test results demonstrated that pore water pressure (PWP) developing process of pure calcareous sand (PCS) and CS-FS mixtures present three stages along with the rate of PWP ratio (PWP to effective confining pressure). The PWP ratio ru of PCS first increased rapidly then grew slowly and finally kept constant. However, the ru of mixture increased slowly first, then grew sharply and finally became unchangeable. In addition, the terminal PWP ratio ruter of all specimens were less than 1.0 which suggests that PCS and CS-FS mixtures were liquefied partly in this study. Along with the PWP behavior, the modified logarithmic model and modified Seed model were proposed to predict PWP ratio development for PCS and CS-FS mixtures respectively. Test outcomes showed that terminal PWP ratio ruter has a positive relation with effective confining pressure and CSR, and the liquefaction degree was aggravated at high stress. Nevertheless, the cycle number to cause liquefaction has a negative relation with FS content or stress level. Besides, the ruter values decreased as increasing FS percentage from 0 to 50% which indicates that FS can improve the liquefaction resistance of CS-FS mixtures.