Effect of Initial Stress State on Dynamic Compression Process and Mechanical Properties of Clay Under Lateral Restriction Conditions

With the gradual transfer of energy resources mining from shallow to deep in China, the current situation of using shallow parameters to solve deep problems and static parameters to solve dynamic problems results in the lack of scientific basis in engineering design. The initial stress state of clay has a significant influence on its dynamic properties. The long-term, graded, high-pressure consolidation method was utilized to simulate the original stress environment of clay, and the SHPB experimental device was employed to perform impact compression on the high-pressure consolidated clay under lateral restriction conditions with a strain rate ranging from 200 to 800 s–1. The stress memory effect, strain rate effect, and dynamic compression process of clay were studied. The experimental results show that the stress history of clay affects its dynamic compression process. The sample goes through the compaction section-linear elastic loading section-linear unloading section in turn. The average stress of switching point between the compaction section and linear elastic loading section under dynamic load is 3.8 MPa, which is correlated with the pre-consolidation stress of 4.2 MPa; the strain of compaction section is about 33% of the soil failure strain as well. The soil exhibits an elastic loading and linear unloading section without being a stable plastic section under the experimental strain rate, as the bullet is 200 mm or 300 mm long. It is found from the stress–strain rate relationship that the compaction section absorbs lots of the compaction energy, resulting in an unstable plastic deformation or even sudden unloading in the soil sample. The modulus of the loading and unloading section increases simultaneously with the strain rate, but the ratio of the two remains stable, which means higher impact velocity does not lead to far more damage. It can also be seen from the phenomenon of damage after impaction as well as the plastic flow analysis. At last, the high-pressure consolidation method provides an approach to studying the dynamic properties of weak and loose granular materials. © 2023 Editorial Department of Journal of Sichuan University. All rights reserved.