Model Test Study On Ground Settlement Of Beijing Subway Running Tunnel

With the rapid development of the construction of the subway in our country, it is predicted that our country will have a large scale construction of subway from 2000 to 2050.So there will be a lot of geotechnical engineering problems need to be solved. The main problem of urban underground construction by Shallow Mining Method at the present time is that Formation disturbance in excavation led to displacement and stress redistribution of the surrounding formation surface subsidence and destruction and influence of around road,construction and underground pipelines. Therefore, how to prevent formation collapse during the construction process of the urban underground engineering and how to protect the buildings and underground pipelines along the construction by the means of ensure the safety of the supporting structure and predict and control the surface subsidence efficiently have become a important subject which should be solved during urban subway construction.This article takes Beijing subway line 5 as s sample and using model experiment to study on discipline of ground surface settlement during tunnel excavated by Shallow Mining Method, we also coMPare the results of model experiment with the dates from construction and numerical simulation. So we can find the ground surface settlement discipline during nonsupport tunnel excavation and verify the reliability of model experiment.Correct selection of similar material is the key to correct simulate original. This article analyzes the principle of selection and combination which base on the study of present research of similar materials. We develop a similar material that is suit for Beijing geological conditions by means of experience of precious and vast proportioning test. This material is composed of barite powder and quartz sand as aggregate and Vaseline as cementing agent. We summarize some factors which influence mechanical parameters of this material through large numbers of mechanical experiment and analysis of experiment data. We got the elastic modules by test and analyze the effect factors on the physical and mechanical properties of material. After that, we fit experimental data by MATLAB, obtain the relationship between content of each material composition in certain range and the measurement of elastic modulus. Finally, we have a conclusion that this new material has advantage of high bulk density, low strength and elasticity module, steady performance, low price, easy busying, easy processing and it can be used repeatedly. It can simulate rock mass materials in a large range. It is an ideal geological mechanics model similar materials.On the basis of grasping the effect factors and laws of similar material, we carry out a plane model experiment of typical geologic strata and tunnel scale of Beijing. And we found that the settlement curve can be described by Peck formula after fitting. Then we made a comparison among the dates form construction, model experiment and computational calculation. The results shows that there is only a small difference between the dates of model experiment and numerical simulation, so we can believe that the simplified model can be used to simulate typical tunnel of Beijing subway, and the similar material we choose is suitable to simulate geologic strata in Beijing. The ground surface settlement of nonsupport tunnel is much larger than supported ones, it reminds us that support must be done in time during tunnel construction.