Research On Laws Of Surface Lift And Subsidence During Grouting At The Back Of Tunnel Wall In The Shanghai Subway

The surface subsidence resulted from excavation of subway tunnel routeway is potentially hazardous, which requires monitoring in terms of the projects safety. Grouting at the back of tunnel wall is an effective solution to resolve such a problem if the level of the surface subsidence is too heavy. In this paper, we are going to analyze the monitoring data of surface subsidence during grouting in tunnel with statistic methods, subsequently to generalize the rules of subsidence and to evaluate the effects of grouting on such phenomena.We begin this paper with introduction of the actuality of forecast of the surface subsidence, followed by discussion of the techniques of both grouting and monitoring. Some monitoring methods of surface subsidence will be investigated in details afterward.There are many methods to study the surface subsidence. We choose the monitoring data method to evaluate the grouting effects because the purpose of this paper is how to get the useful information from these monitoring data. We will use regression method, one of the best among four to analyze the monitoring data, together with Matlab6.5 as the software. We found that there were three periods after surface distortion, from which the final level of surface subsidence can be calculated after the completion of the grouting, therefore we were able to evaluate the effects of grouting on surface subsidence. We also built the subsidence model to calculate subsidence values by using regression method, thus the subsidence level can be estimated between two grouting periods. Based on such model, we deduced the multi-element linear regression formula between the slurry quantities with subsidence level. As one of the results of this paper, we drew a conclusion that the grouting holes should be distributed evenly, which provides some new ideas for both the same projects and correlative examination in the future.