Study On Dark Pier Reinforcement Mechanism And Calculation Methods In The Excavation Pit

With the development of our country’s economy, more and more people pay attentionto the development of urban underground space.with the depth and scale of foundation pitexcavation increasing, supporting scheme of foundation pit should not only guarantee thestability of foundation pit their own safety,but also require to take effective measures toreduce the environment deformation caused by the excavation. Dark pier reinforcement isone of the effective measures to reduce supporting structure deformation in the soft soilfoundation,but the research of its theory is far behind the engineering practice.In this paper,through theoretical derivation and finite element simulation method,on the basis of existingresearch, this article carry out further research on the reinforcement mechanism and designmethod, the main work is as follows.(1) First of all, from the angle of mechanics, it will use the generalized hooke’s law anddeformation and internal force calculation formula inside material mechanics to deducedeformation formula in passive area soil. The formula shows that soil reinforcementincreases the soil shear strength parameters c, φ values, modulus of elasticity and thecoefficient of friction with the surrounding environment, which make the amount ofdeformation of the part reduced, thus effectively control deformation of foundation pit.（2）Then it uses finite element software Midas/gts to establish engineering model toanalyze influence factors, for different width and elastic modulus of reinforcement solid,and research and the relationship between the solid depth and the excavation depth. theresults show that foundation pit reinforcement can effectively control deformation offoundation pit, and found out the reasonable and effective reinforcement scope0.55H~0.625H and best elastic modulus at about300Mpa.(3) It research on how to get the m values, which is critical to calculate the deformationof retaining structure in m value method. According to the result of finite element simulation,it fit out the calculation formula of m values, which is suitable for the local, the resultsshow that m value and different reinforcement width meet the power series, it takes into thedifferent influence factors, such as soil elastic modulus and reinforcement wide, whichmake m value closer to the actual values and change its arbitrariness.And it provides for thebasis of m value in the calculation of deformation of supporting structure.（4）Finally, it introduces the basic principles of the supporting structure calculations,resenally thinking over the effect of m value, a project example in Zhenjiang was calculated. compared with the results of finite element model, it instructions the reasonableness of thesimulation results and that internal reinforcement can control the deformation of theexcavation.