Beijing Subway Mining Method Due To Construction Of Ground Settlement

Large-scale of subway construction to provide people with convenient also leads to manyproblems. For example, the Shanghai Metro Line4construction in July2003lead to the grounda substantial settlement, Dalian Metro three collapse during March to August2011. Thesesubway construction disasters occurred in recent years to a local cause significant economiclosses and serious social impact. Therefore, how to prevent uneven settlement of metroconstruction on the building foundation in the subway construction, cracking of the groundconstruction, sink and subway construction process of the collapse phenomenon, look for groundsettlement caused by construction. The protection of works carried out smoothly became thestarting and ending points of the construction of subway security. This paper intends to rely onthe Beijing subway construction project examples. Use of theory, on-site monitoring of dataanalysis, and ANSYS numerical analysis of three methods, analysis due to precipitation, caverndepth, step method of construction on the surface settlement. Construction of surface settlementrange. Using regression analysis to verify the relationship between surface settlement with thecorresponding vault settlement. And through theoretical analysis and experimental data, verifythe accuracy of the formula of Peck. Identified the Beijing mining method in tunnelingapplications Peck formula parameter value calculation formula.(1) Construction dewatering of surface subsidence of about25.5%of the total settlement.Within the boundaries of the settlement trough, the closer away from the tunnel axis,due to excavation-induced settlement of the total settlement greater. Outside thesettlement trough boundary, surface subsidence due to precipitation.(2) In Beijing, the settlement trough width factor i the formula should be adoptedi=R(h)n2R[n=0.81.0]. Settlement trough width should be β≈6ito estimate. Andfield data show the greater the tunnel depth, width coefficient of the settlement trough igreater the smaller the maximum settlement value Smax.(3) Measured vault settlement accounting for maximum ground subsidence of about60.8%.Regression for fitting analysis that began when the distance from the tunnel face about1.5times the hole diameter, the vault location of layer deposition.(4) Surface longitudinal settlement curve trend of change over time in line with the doubleexponential curve form. The main settlement in the growth phase of the curve. And when the measuring point to the tunnel face distance of about1.2times the holediameter, the settlement began to rapidly increase. Settlement of about70%of the totalsettlement.(5) Obtained by excavation of the two step method, the three-step method and full-facemethod simulation analysis: Step method subsidence caused by the excavation ofapproximately80%of the full-face method of construction caused by subsidence. Stepmethod step a few more ground settlement affects the smaller. When the cross section islarger, the large cross section to differentiate into the small cross section can be everylittle section to form a complete system of force, reducing the exposure time of thesurrounding rock.