Feasibility Analysis Of Shield Driving Method Used In Interzone Tunnel In Chengdu Metro

Subway tunnels have been constructed always are located in the alluvium clays,sandy clays or soft rocks in china. The subway tunnels are built with shield driving method in these strata has much mature experience at home and abroad.But the strata with high ground water level are composed of alluvium clays, silty clay, gravels and crushed stone soils in Chengdu;And the shield will drive in the interzone with complicated geologic environment, especially in the strata contained more than 50 percent of gravels which diameter is greater than 5cm, also contained big grain size gravels(the maximum diameter is about 1m), cement gravels and silty sand with lentoid mass;And on the ground there have many serried buildings in the prosperous zone. The subway tunnels are built by using shield driving method in these strata has no precedent at home and has not mature experience at abroad.Therefore it is necessary to analyze how to use shield driving method in Chengdu metro.The contents in this paper enumerated as follows:(1)Which type of the shield adapt to the strata in Chengdu. The open shield,the earth pressure balanced shield and the hydro shield are mainly analyzed.(2)The structure' s mechanics characteristic and the waterproofing measures of the shield tunnel are studied. The structure' s mechanics characteristic under the different earth pressures and the water pressures is analyzed. The structural of the shield tunnel will be designed to adapt to the strata in Chengdu and is analyzed on a basis of the mutual action between the structural and the surrounding rock. And the waterproofing measures are studied to take to favor the effect on the structural.(3)The effect on the surroundings by using shield driving method to excavate is forecasted and controlled.' At first the causes of the strata' s settlement are analyzed, secondly the several controlprojects are simulated by using FEM analysis, finally the control measures are gained on a basis of the analysis of the effect on the structural and the settlement of the strata.(4)The NATM which is used in Chengdu metro is studied. At first the excavation method, the support type and the disposal of the underground water are studied. On a basis of it the structure' s mechanics characteristic and the effect on the surroundings are analyzed. Finally the mining method is contrasted with the shield driving method.