Abstract:

During the construction of Zhongtiaoshan Tunnel on Menghua Railway, a series of problems, i.e. soft and weak and weathered surrounding rock, inadequate bearing capacity of inverted arch base, rich water of sandycobble load bearing strata of inclined shaft and large volume of water inrush of tunnel, were encountered. Key technologies, i.e. rapid closed ring by microbench of soft and weak surrounding rock with onetime inverted arch excavation, largesection filling of inverted arch of secondary lining and inverted arch of singleline railway tunnel, spall filling and reinforcement of inverted arch base and drainage pipe set in inverted arch base (including sectioned water stop and reverseslope drainage technology), are introduced. Some conclusions are drawn as follows: 1) The secondary disturbance of surrounding rock can be reduced and the surrounding convergence and crown top settlement can be effectively controlled by onetime blasting and shaped of inverted arch and lower bench. 2) The connecting time of construction joints between inverted arches can be reduced and the integrity of inverted arch can be improved by 24 mlong hydraulic crawlertype trestle. 3) The water stop effect of watercontained soft rock section can be improved by spall filling and grouting reinforcement. 4) The water drainage volume of reserve slopeface excavation can be reduced and the construction schedule of excavation face can be shortened by sectioned water stopping technology.

Key words: onetime excavation with inverted arch, rapid closed ring, largesection construction of inverted arch, base filling reinforcement, sectioned water stop