Dynamic characteristics and microstructure of clay reinforced by the splitting grouting method under subway dynamic loading

Abstract The splitting grouting reinforcement method is typically used to improve the stability of surrounding rock when constructing subways in water-rich and weak strata. However, in contrast to normal soil, the dynamic characteristics and microstructure of reinforced soil under cyclic loading of a subway necessitates further clarification to obtain a technical basis for controlling the deformation and settlement of the reinforced soil during later stages. Based on field-reinforced soft clay samples, this study analyzed the dynamic characteristics and microstructure of reinforced soft clay under cyclic loading through stress-controlled undrained cyclic triaxial and scanning electron microscope tests. The results showed that the lower the frequency or the larger the cyclic dynamic stress amplitude, the faster the residual strain development of the reinforced soft clay. There were three cyclic creep characteristic curves of reinforced soft clay: peak, base, and valley creep curves, and the development of base creep represented the overall trend of cyclic creep in reinforced soft clay. In addition, calcium silicate hydrate and ettringite were produced in the reinforced soft clay, which improved the connectivity between the soil particles.