Abstract:

Waterrich immature fine silty sand stratum is a special stratum of the extremely soft rock strata with the characteristics of nonuniform diagenesis, complex hydrodynamic environment, diverse, complex and changeable strata mechanical properties, and the rock formation as a whole lacking selfstability, which are prone to the problems of sliding down, slippage, sand and water grushing, base softening and bearing capacity decreasing, etc. In this way, it brings about many disadvantages for construction and even threats for construction safety. In order to solve construction difficulties in the stratum, threelevel dewatering method, i.e. vertical deep well dewatering + advanced vacuum deep hole dewatering + light well point dewatering, used in construction of the exit of Taoshuping Tunnel in LanzhouChongqing Railway is set as an example to be studied. And then the equipment, craft, method and technique parameters for dewatering in this stratum are summarized, and thus the problem of dewatering in waterrich immature fine silty sand stratum are solved, which can provide references for tunnel dewatering in the similar stratum.

Key words: waterrich immature fine silty sand stratum, tunnel, dewatering technology