Analysis of the factors affecting the deformation of silty soil around Shanghai metro tunnel

The soil surrounding subway tunnels undergoes cumulative plastic strain due to the prolonged influence of subway loads, potentially leading to uneven settlement of the infrastructure and compromising the safety of subway operations. This study aims to thoroughly investigate the strain characteristics of the soil around these tunnels during metro operation and identify the primary factors contributing to soil deformation. Dynamic triaxial tests were conducted on pulverized soil from the vicinity of Shanghai Metro Line 10. Initially, the control variable method was utilized to examine the effects of loading frequency, dynamic stress amplitude, and consolidation ratio on cumulative plastic strain individually. Subsequently, a 23-factor experimental design was employed to explore the interactions among these factors. The influence of each factor on cumulative plastic strain was quantified using analysis of variance (ANOVA). A nonlinear regression equation was derived based on the statistical significance of each factor. The findings reveal that increases in consolidation ratio, stress amplitude, and loading frequency from low to high levels result in variations in accumulated plastic strain by factors of 5.5, 2.4, and 16, respectively, highlighting significant interactions among these variables. The effects of consolidation ratio, dynamic stress amplitude, and frequency on cumulative plastic strain were found to be substantial, with significance values of 118.5, 2127.25, and 449.25, respectively. Special attention should be given to the dynamic stress amplitude in relevant research. The developed regression equation demonstrates robust predictive capability and can serve as a reliable tool for analyzing soil deformation under subway loads.