Research Of Influences On Shield Construction For Surface And Buildings In Dananmen Section Of Taiyuan Metro Line#2

With the rapid development of social economy, seven subway lines arebeing planned to construct in Taiyuan City for the first time, among whichMetro Line2will be the first line. At present, metros have been built in manylarge and medium-sized cities in the world and they are mainly constructed bycut and cover method and underground tunneling method. As a kind of advancedmethod in the underground construction method, the shield method has beenstudied and applied in many cities of our country, and has gradually movedtowards maturity. There are two main factors of ground subsidence in theprocess of shield tunnel construction; they are the decline in groundwater leveland the construction disturbance during the excavation. In spite of quite a lotresearch and experience on ground deformation in the process of shield tunnelconstruction in China, it has never been researched in Taiyuan and fewexperiences references can be used. It will be some project valuable to do someresearch on the impact on ground and buildings in the process of tunnelconstruction in the conditions of engineering geology, hydrologic geology andstratigraphic structural characteristics in Taiyuan City.This paper takes the Dananmen Section of Taiyuan Metro2#line as theresearch object and makes a comprehensive understanding of the engineeringgeological conditions and hydrogeological conditions of the Taiyuan basinthrough investigation and mapping. Then detailed geotechnical investigation ofthe Metro Line2in Taiyuan City has been carried out to learn the strata structure.And it has carried on the sampling and the indoor experiment to study physical and mechanical properties and penetration properties of each district level andeventually the formation structural spatial model is established. A geologicalconceptual model is established according to the engineering geological andhydrogeological conditions and aquifer and water-resisting layer of generalizedand boundary conditions. Meanwhile, theoretical research on groundwaterseepage theory, soil consolidation and sedimentation principle and fluid-solidcoupling mechanism is carried out. Using fish language programming, thesolution computation of the model is carried on by FLAC3D software in fourdifferent working conditions. Simulation results show that the groundsubsidence is0.35~20millimeters when tunnel diameter is6meters and burieddepth is24meters and avoiding the construction of buildings on the surface; theground settlement is0.8~35millimeters when tunnel’s diameter and burieddepth don’t change and the subway is built underneath the surface buildings; thesettlement of the surface is0.72~33millimeters when the tunnel diameter is6meters, the buried depth is18meters as well as the tunnel isn’t underneath passthe surface building; moreover when the tunnel’s diameter is8meters, burieddepth is24meters and it avoids the buildings, the settlement of the ground is0.7~31millimeters. By analyzing the simulating results, the shallower tunnelburied depth and the bigger its diameter, the greater the surface settlement and italso happens when the tunnel passes across the bottom of the surface building.In addition, the smaller the surfaces load and the farther the tunnel from thebuildings, the smaller the settlement according to the curve of settlementsection.The maximum settlement of the surface is30millimeters on the basis ofthe control standards of surface subsidence given by the expert opinion orexperience in the domestic engineering. In conclusion, the settlement of theground caused by the construction meets the standard when the DananmenSection of Taiyuan Metro2#line is24meters deep with the diameter of6meters, and it is built without passing through the surface buildings.