Design And Construction Research Of Tunnel Dewatering Under Karst Geological Conditions In The Subway Line 2 Of DaLian

This paper studied the groundwater control problem of the karst area(local limestone caves area).Metro line two—— Nan Guan Ling Railway Station to Nanguanling town station is a representative case.For the construction weathering fissure water and structural fissure water and karst fissure water in the the tunnel,there is not a perfect internal system for the construction design(the design and construction of this project is the first model in the karst area of the subway line and it is the first time to use the the pit dewatering scheme for groundwater control in the domestic).The primary task of this research is to sort out the control system of the karst fissure water in the mine tunnel, and optimize the project(down, stop and discharge),as a precondition for the construction of the tunnel structure. The core of this paper is to form a complete set of design and construction system, not only to promote the theoretical research, but also to facilitate the operation of the builder.In the karst geological conditions, the technology of the traditional dewatering well construction has the main disadvantages of low efficiency and poor well washed(water) effect. It seriously restricts the construction of the subway construction.Pneumatic DTH hammer drilling wells after formation with a high efficiency.It's main disadvantage is that before this study the well vertical design is not appropriate.The research mainly focuses on the improvement of the dewatering well structure,andthe test of the feasibility of DTH hammer technology in the construction of the subway precipitation wells.The main innovation of this study: one is using the high density electrical prospecting design as auxiliary means, design the partition according to the karst development situation and karst water enrichment location and degree of enrichment; two is the combination of water balance model calculation method and Oshima Yoshi formula to calculate the interval total yield by using water balance method and tunnel initial maximum inflow(diffusion flow)using Oshima Yoshi formula,get the difference between the two calculation as the part of pipeline flow;three is the improvement of the layout of the traditional precipitation wells and the structure of dewatering well,to the uneven development situation of the area of fissure water in the bedrock limestone,densen locally well arrangement and deepen the control of the detail, according to the situarion of the karst development and the filling of the karst cave in the precipitation the vertical design of wells were clear; four is the construction of the dewatering well with DTH hammer drill in construction process and the successful groundwater control to ensure the safety of the tunnel construction.