Study On The Construction Technology Of The Jin-yun-shan Tunnel Through The Harmful Geology

Jin-yun-shan tunnel is the control engineering in A-Contract of Chengyu-highway. the tunnel inlets of left and right line pass through karst depressions, sinkholes and caves, underground rivers, goaf and gas stratum. The geological conditions of the tunnel engineering are complex, and there are some risks with the sudden water-mud outburst, gas outburst and collapse in the tunnel construction. It is important to tunnel construction how to to prevent the tunnel from the sudden water and gas explosion by scientific and reliable technical measures in tunnel construction. In the paper, The study is carried out to decide the construction scheme and construction parameters n the Jin-yun-shan tunnel construction to avoid the above risks. Specific research contents are shown as follows:(1) Construction schemes and supporting parameters are decided for the Tunnel portal construction. And the construction programs and support parameters of the tunnel excavation for the three kind of rock, and the blasting parameters and tunnel ventilation parameters are determined through calculation. Furthermore the construction technology of pre-support, secondary lining, water-proof and water-drainage, reservation hole and embedment parts is introduced in the paper.(2) The dynamic construction scheme of the Jin-yun-shan tunnel through karst cave is proposed. According to the field situation, combined with engineering design, the karst caves are divided into 6 typies based on the development degree of karst caves and their relative space position to the tunnel. And then the 6 construction scheme are designed verso 6 types of karst caves, and the backfill and supporting parameters also are offered.(3)According to construction difficulties of Jin-yun-shan tunnel through karst water and underground, “advanced detection of water-analysis of the water-selection of construction scheme and technical parameters- pre-grouting and post-grouting” the whole dynamic construction is proposed. According to the geological conditions of the underground water, the scheme of advanced detection water is designed. According to the different water conditions, the whole section pre grouting, local pre grouting and small pipe grouting are proposed to prevent the water inrush, which the water inrush problem is solved.(4)According to the possible gas outburst In view of the tunnel through the strata of coal, the discharge- blocking methods are used. If gas gushing quantity exceeds the warning value, the gas discharge is used and the construction scheme and parameters of gas drainage are designed. The lining before and after 20 m is covered with fully enclosed waterproof board and non-woven fabrics, and settlement joints and construction joints are blocked, and sealing agent is added in the secondary lining. By the above methods, the gas seeping into the tunnel is effectively cut off, which the gas outburst problem is solved.(5)According to tunnel excavation through the empty zone, mined out area around the both sides of the wall and arch of the tunnel are backfilled, and mined out area under the inverted arch is filled by the liquid cement through the drilled holes. Furthermore construction parameters of the layout of drill holes and grouting pressure are presented. Using the above construction scheme, the problem of the Jin-yun-shan tunnel through the collapse of mining area is solved.