Key Technologies and Innovations for the Construction of'Four Extreme and Three High'Geological Tunnel
At present,there is little research on the construction technology of'four extreme and three high'geological tunnels,which integrate the crossing of active fault zones,high geostress,high geological disaster risks,soft and fragmented lithology,and abundant groundwater.Combining the Hongqiaoguan Tunnel project of the Chengdu-Lanzhou Railway,which crosses the active fault zone of the Minjiang River,the tunnel is a 'four extreme and three high' tunnel,which is prone to deformation,steel arch distortion,fracture,and serious damage to the initial support structure during construction.We have developed a combination system of long and short anchor rods together with longitudinal and circumferential equal stiffness arches,as well as a tunnel excavation method with a large core soil reserved at the upper part of the micro three-bench.This has accelerated the tunnel construction progress and the closure of the primary support structure into a ring,effectively controlling the occurrence of large deformation in the tunnel.In view of the characteristics of large dislocation and large structural damage after earthquakes in active fault zones,a circular lining structure system with unequal length and multiple segments has been developed for tunnels crossing active fault zones,effectively enhancing the anti-dislocation capacity of tunnel structures.A waterproof and drainage system for tunnel structures with wide deformation joints in active fault zones has been developed,solving the problem of water leakage in tunnels in active fault zones.The application of these innovative technologies has achieved safe and rapid tunnel excavation,which can be used as a reference for similar projects.
four extreme and three hightunnel engineeringmicro three-benchlong and short combination anchor boltactive fault zonewaterproof and drainage systemwide deformation joint
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