Triaxial Experimental Study on Strength Characteristics of Saturated Soft Soil Under Different Shear Strain Rates

Abstract

AbstractThe China Nansha District of Guangzhou City is located at the geographical center of the Pearl River estuary and the Greater Bay Area of Guangdong, Hong Kong, and Macau, is characterized by widely distributed saturated soft soil layers with poor engineering properties. Although many scholars have explored the influence of loading rate on the mechanical properties of soft soil, research on the variation of undrained shear strength of saturated soft soil under different shear strain rates is still limited. This article conducts an in-depth analysis of the mechanical behavior of saturated soft soil under different strain rates through true triaxial consolidated undrained shear tests. Under load, these layers exhibit a significant rate-dependent mechanical behavior. In order to reveal the influence of shear strain rate on the mechanical properties of highly saturated soft soils based on SPAX-2000 test system, a series of true triaxial consolidation undrained shear tests were carried out under different confining pressures and different strain rates, variation rules of undrained shear strength of saturated soft and the pore water pressure with strain rate were analyzed. The experimental results indicate that the strain-rate softening exists in saturated soft soil. Under the same consolidation conditions, the relative growth rate of shear strength is a monotonic increasing function of the logarithm of shear strain rate, and the smaller the intermediate principle stress, the more significant the effect of shear strain rate on shear strength. During the shearing process (The strain-rate range from 10–6/s to 10–2/s), the undrained shear strength of saturated soft soil increases with the growth of shear strain rate, following an exponential variation pattern. In the early stages of loading, the increase in pore water pressure and the maximum pore water pressure are significantly affected by the strain rate. Throughout the testing process, the variation of pore water pressure exhibits some fluctuation and hysteresis. Different from strongly structured clay, the strength of saturated soft soil undergoes a progressive change with the shear strain rate, without showing a distinct critical rate of transition.