Analysis Of Second Grouting For Controlling Subsidence In Shield Tail Void

In the modern construction of metro, shield tunneling has been widely used.But during the process of construction, ground subsidence occur because of various influence factors, which will lead to the collapse of the surficial buildings、roads and buried pipelines and so on. The settlement process can be divided to five stages: advanced settlement, the settlement before excavation surface, sinking as the shield going through the section, the subsidence caused by shield tail, later subsidence. The fourth stage usually causes an outstanding subsidence, which need the grouting solution to control the settlement. In fact, it is difficult to padding shield tail fully by the slurry filling, thus causing the soil around the tunnel moving. Therefore, the research about the grouting to fill the shield tail requires further study, which is significant meaningful.Many works about the subsidence rules have been done by researchers, and the methods of which can be divided into three:theoretical method analysis、 numerical method analysis and model experiment. Besides, the point of grouting they focus on was mainly about synchronous grouting. However, the filling effect of tail void was still not satisfied in the construction process. In order to solve this problem, the second-grouting technology was presented and used in practical engineering, which was processed as a remedial measure for engineering accident. In this paper, more research work about second-grouting are conducted,which is mainly about the properties of materials and grouting interval during the second-grouting process.In this article, by analyzing the mechanism of grouting to reduce the ground subsidence and the relevant model test, we got the conclusion that it is meaningful to conduct second-grouting in shield tunneling. In addition, we stimulated the ground settlement situation with the finite element software FLAC/FLAC/FLAC3D.The result is consistent with the monitoring data, which verified the reasonability of the stimulated model and the second-grouting. Furthermore, we analyzed the change rule of ground settlement with different second-grouting materials and location. All the work was developed for providing some theoretical guidances for construction.