In Situ Experimental Study on SDC Grouting in Shanghai Saturated Soft Clay

Shanghai saturated soft clay is featured with high water content, high sensitivity and thixotropy. Improper parameters for any form of ground reinforcing process can easily cause significant disturbance to the soil, thus the desired effect can't be achieved. In protection of operating subway tunnel which is highly sensitive to deformation, the ground reinforcement should not only satisfy the requirements on final effect of tunnel deformation after reinforcement, but also guarantee the safety and deformation limits in the whole process of reinforcing. Therefore, an in-situ experiment is carried out on the technological parameters of sleeve pipe grouting method, which is often used in the deformation control of Shanghai subway tunnel. The multi-parameters testing and experimental analysis focus on the influence of grouting pressure, grouting rate of flow, grouting divisions and total grouting volume of a hole based on the monitoring data excess pore water pressure and ground deformation. The results show that the ground deformation and its steadiness are highly correlated to these four parameters. Therefore, in order to minimize the disturbance to soft soil in grouting process(Small Disturbance Control, SDC), the above grouting parameters must be optimized and carefully chosen according to their effects and the operation conditions of subway as well as the geological formation of ground strata.