Research on Construction Technology of Large Section Tunnel Excavation in Ultra-Shallow Buried Silt Water-Rich Stratum
Aiming at the problems of easy collapse and high difficulty of support in excavation of large section tunnel in ultra-shallow buried silt water-rich stratum,this paper takes the construction of section RSK1+337.861～RSK1+406.306 of Lujiao Car Depot of Chongqing Rail Transit Line 24 Phase I project as the engineering background,and proposes the construction technology of"circular CD+step method for reserving core soil method".Midas GTS NX numerical simulation software is used to establish a three-dimensional model.By analyzing the total displacement of the surrounding rock and the stress of the supporting structure of the tunnel,the rationality of the proposed construction technology is determined,and the weak parts of the tunnel excavation are predicted.According to the simulation results,the tunnel arch is the weak link in the construction process.The maximum settlement value of the tunnel arch is 6.69 mm,and the maximum convergence value of the arch waist is 2.48 mm,both of which meet the construction requirements.Finally,the monitoring results show that the arch roof settlement and headroom convergence of typical section are basically consistent with the simulation results,and both can meet the standard design control values.The construction technology provides valuable reference for subsequent excavation of large-section tunnels in ultra-shallow buried silt water-rich stratum.
subway tunnelsilt water-rich stratumnumerical simulationcircular CD methodstep method for reserving core soil
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