Safety Analysis And Countermeasure Research On Ground Settlement Of Shield Construction In Tianjin Metro Line 5

In recent years, with the increasing pressure on urban ground transportation, major cities strive to develop underground transportation. In the underground traffic engineering construction, the shield method has little impact on the environment, good stability, so as to get the favour of the most people. But shield construction can not avoid soil disturbance, so we have to solve an inevitable problem-- surface subsidence. Therefore, based on the experience of the shield tunneling experiment in Line 5 Tianjin Subways and the study of the ground settlement under the special geological condition in Tianjin area,the research content is as follows:1. This paper introduces the development status of shield method in our country, and describes various methods of surface subsidence calculation and prediction which have been widely used, as well as the advantages and disadvantages of each method and applicable conditions.2. Fully understanding each working procedure of shield construction, this paper analyzed each step which can lead to soil disturbance.Having a strong understanding of the engineering of five line, this paper focused on its geological environment.3. According to the research of the predecessors, as well as other shield construction data in Tianjin,from two aspects: construction factors and environmental factors, this paper summarized the factors of the ground subsidence caused by shield construction, the ground settlement caused by shield construction is not only of the separate effects of a certain result,or the simple sum of the effect of each factor results, but the result of the combined action of multiple factors. A complex function relation exists between various factors, and between the results.4. With the construction data collected from test section of tianjin metro line 5, including the construction monitoring data and geological data, and with the BP neural network in MATLAB neural network toolbox, the forecast model of the ground subsidence caused by shield construction is set up on the basis of the multi-factor comprehensive function.By comparing the predicted results and the actual monitoring data, the effectiveness of the prediction model is proved.5. By using the model to predict the subsidence of the actual shield construction, the abnormal points are picked out and analysed, then picking out the subsidence of the larger point, finding the causes, and the highly individualized measures are put forward.