Numerical study of the performance of compaction grouting in structured clay using a hypoplastic model

Abstract Previous studies on compaction grouting mainly focused on reconstituted clay but did not consider the widespread structure of natural clay. Unlike reconstituted clay, the stress state and void ratio are independent in structured clay due to weathering. Thus S, the state parameter of structured clay, was proposed in this paper to more accurately describe the state of structured clay. Rs, the relative state parameter of structured clay was also proposed to normalize S. Then the numerical hypoplastic constitutive model of structured clay was implemented to evaluate the performance of compaction grouting in structured clay. It shows that the grout efficiency increases with sensitivity when Rs=0 but decreases when Rs=1. Besides, the grout efficiency and grout pressure decrease with increasing Rs. For structured clay with different values of S, there exists a certain value of Rs where the grout efficiency and grout pressure are equivalent to those of the corresponding reconstituted clay. Furthermore, the results were compared with those of heavily overconsolidated clay. It is determined that although negative pore pressure appears in both the horizontal direction and vertical direction in the structured clay when Rs=0, it only appears in the horizontal direction in heavily overconsolidated clay during grouting.