Study On The Key Technology Of Shallow Mining In Beijing Metro Line.7DaGuan Ying Station And WanDa Section

Aiming at solving the major technical problems, which exist in the construction of Beijing MetroLine.7No.1bidding section-Da Guanying PBA mining station and Wan Da large section running tunnel.Through field tests, numerical analysis, process improvement, theoretical analysis and other methods,researches have been done on dewatering of water-rich sand gravel layer, bidirectional excavation ofsmall pilot tunnels in PBA station, advanced support methods of PBA station, process improvement ofsuper long pipe roof, large section tunnel construction close to river bottom and construction of doubleunite arch tunnel with large section. The findings show that technique on once-through fast Well Drillingusing pneumatic down hole hammer combined with steel tube, can effectively solve the dewateringproblem in gravel layer; Study the deformation laws, which caused by bidirectional excavation of smallpilot tunnels in PBA station, by numerical simulation and monitoring data analysis. Results show thatexcavation sequence and staggered distance play an important role in deformation laws, the bestexcavation sequence is2.4-5.7-1.3-6.8and the best staggered distance is15m; Analyze three kinds ofadvanced support schemes (small pipes, deep hole grouting and pipe sheds) by numerical simulation, andput forward that pipe sheds are the best scheme using multi-factor comparison and selection. Put forwardthe scheme that combine “rigid-flexible combining lining” in river with WSS deep hole grouting, whichsolve the problem of large section tunnel construction close to river bottom; First put forward the newmethod “CRD+CD” to solve the problem in the construction of double unite arch tunnel with largesection.