Mechanical behavior of a fissured clay subjected to impact loading under the plane strain condition

This study conducts several triaxial cyclic and plane strain cyclic impact tests on fissured soil under varying effective consolidation pressures, impact peak loads, and frequencies through the true triaxial test system to investigate the mechanical response characteristics. The results indicated that, under plane strain conditions, the specimens' shear resistance increases compared to that under triaxial loading. Moreover, the influence of fissures is challenging to quantify under triaxial loading compare to the mechanical response to fissure failure under the plane strain condition. As a result of the lateral confinement under plane strain conditions, the excess pore pressure, stress path, and lateral stress coefficient exhibit changes in sensitivity due to fissure damage, facilitating the analysis of the fissures' influence. Lower consolidation stress tends to increase the likelihood of fissure failure. As the peak impact stress escalates, the specimen deformation and excess pore pressure rise. When the impact peak stress reaches a critical value, the sample undergoes substantial deformation and fails rapidly. The impact of the frequency on specimen deformation correlates with the peak impact stress. Under low-impact peak stress, higher frequencies result in smaller deformations. However, under high-impact peak stress, a critical frequency exists. As the frequency increases, the difference between the maximum and minimum pore water pressure expands, with the change in this difference relating to fissure damage. Inherently, fissures in the soil significantly affect the mechanical properties under the impact load in the plane strain condition. The findings from this study can provide technical support for determining and evaluating the mechanical parameters of the fissured soil layer in light of the impact load.