Research On Safety Analysis And Deformation Preview Of Deep Excavation By Data Mining

With the amelioration of urban rail transit network in Shanghai, projects of the metro construction have showed six trends. That is the foundation pits become deeper, the scale of constructions is getting larger, the distance between buildings and subway is getting closer, the time limit for constructions is more urgent, the geologic feature is more complex, the hidden troubles are more and more. How to accomplish the node target of completing 400km basic network in both 'quick and satisfactory' way under the situation of large scale, leaping over style, high integration of risk becomes a question for the subway constructors in Shanghai. This paper concentrates on the evaluation of safety and deformation prediction of the foundation pits of subway stations in Shanghai soft soil from the needs of real projects. The paper collected millions groups of field measure data from more than 100 both constructing an constructed subway stations and innovatively introduced data mining technology into the research. The main ideas of the paper are listed as follows:1, Based on relative studies at home and abroad the paper comprehensively summarized data mining technology and analyzed the origin and development of the technology, dealing process and algorithm principle of relative calculation models. According to the features of subway foundation pits in Shanghai soft soil, the paper studied the prospect of data mining technology in this area.2, The paper selected 31 representative deformation data of retaining structure of subway foundation pits in Shanghai soft soil and studied time-space distribution rule of the maximum deformation ratio and deformation velocity by data mining technology. On the basis of research mentioned above and practical cases in the Shanghai, a reasonable and effective series of deformation alarm value in the pits constructing was put forward.3, By compiling and mining the data of retaining wall deformation and ground settlement which comes from 233 foundation pits in Shanghai soft soil, the conclusion of distribution rule and feature between horizontal distance of maximum ground settlement point far away from the foundation pit and the maximum horizontal retain wall deformation was drawn. Changshu subway station was chosen as an example. The paper adopted FEM programmer which considered the coupling of 3D seepage field and stress field to calculate the ground settlement when the foundation pit was dewatered. It also made use of stratum compensation theory to calculate the ground settlement resulting from excavation of the foundation pit. Add the two kinds of ground settlement together, and then made a comparison with the field measure data.4, By analyzing and mining the feature of numerous deformation time-history curves of retaining wall and referring to other relative deformation prediction methods as well, the paper proposed a set of deformation prediction method based on field measure data. The method divided deformation of foundation pit into two phases, 'excavation deformation' and 'bracing deformation'. Different calculation methods are proposed according to each phase. The method was proved by the data of Gubei subway station.