Law Of The Effect Of Disturbance For Cross Tunnel In Weak Rock Near The Construction

With urban development, the number of underground rail line becomes morevarious inevitably produces tunnel crossing. This article adopts the method of finiteelement simulation combined with field monitoring Beijing metro line7through boththe tunnel line10station engineering, study the stress and deformation law of mutualinfluence of new tunnel and existing tunnel. On the basis of existing tunnel deformationfactors of cross tunnel risk analysis and evaluation standard is established. The mainresearch contents list as follows:(1) Through the analysis of the influence factors of new tunnel on existing tunneland based on the fuzzy mathematics comprehensive evaluation method establish crosstunnel system of risk assessment. By quantifying the risk grading factors concluds thelevel of risk for construction of Beijing metro line7to line10is3, namely, general risk.(2) Through the numerical simulation of the newly built tunnel construction usingthe method of CRD and steps method, it is concluded that the CRD method is adoptedon both the tunnel deformation and surface subsidence is more small. After thecompletion of the step method is used the tunnel deformation is1.714mm, CRDmethod is only0.4mm. Using the step method surface subsidence is12.59mm, CRDmethod is only5.16mm. Contrasting digging two parallel tunnel at the same time andonly digging a tunnel, it is conclude that digging two parallel tunnel at the same timemake greater turbulence: surface subsidence is13.01mm after excavation is completedby using the method of digging two parallel tunnel at the same time; by using themethod of digging one parallel tunnel it is only11.2mm. (3) Through the numerical simulation of tunnel using step method, it can beobtained that the new tunnel lining the maximum stress is located through theexisting tunnel axis9m, the maximum stress is0.9MPa, stress value at3~9m changedobviously. Through the process oftunnel liningdeformation was obvious during6minterval to the tunnel axis, the deformation of existing tunnel lining deformation is90%.The new tunnel stress dangerous section locate after the existing tunnel axis3~9ma,the dangerous section for crossing locates before crossing the existing constructionsection of tunnel axis.(4) By comparing the measured deformation value to existing tunnel in differentstages of GJ7and GJ5, it is found that when using the step method, the excavation halfsteps make large deformation, the second half is small.It can be concluded that the firstdisturbance makes more effect, so construction should be reduced as far as possiblewhen digging first excavation section. In combination with field monitoring data,analysising field monitoring of deformation value of existing tunnel, it is found thatbasic consistent with numerical simulation value and the measured values shows thatthe numerical simulation results and can reflect the tunnel deformation law in theprocess of construction.