Dynamic Mechanical Properties of Unsaturated Red Clay Subjected to Impact Loading

Red clay, a typical special soil, is frequently utilized as a filling material for engineering operations in southwest and south regions of China. Thus, it is of great importance to study the dynamic properties of red clay for use in engineering applications. However, a detailed characterization of such behaviour for red clay subjected to impact loading has not been reported in the existing literature. In this paper, a Φ50mm Split Hopkinson Pressure Bar (SHPB) apparatus is used to conduct a series of uniaxial impact tests on remolded red clay under passive confining pressure condition. The influence of strain rate and moisture content on the dynamic mechanical properties of red clay are investigated. The experimental results show that the dynamic elastic modulus, ultimate strength and maximum strain of red clay increase with the increase of strain rate. The dynamic elastic modulus and ultimate strength appear as a linear function of strain rate in the range of strain rates from 255 to 564 s−1. Besides, the moisture content has a negligible effect on the strain rate sensitivity of unsaturated red clay dynamic elastic modulus. In contrast, it has a significant effect on the ultimate strength strain rate sensitivity. Eventually, the exponential function relationship between normalized dynamic elastic modulus, strength and strain rate considering the change of moisture content was established, which can be the experimental basis for developing the dynamic constitutive model of unsaturated red clay.