土压平衡盾构土仓压力的计算方法研究

Study on Pressure of Soil Compartment in EPB Shield Tunneling

在土压平衡盾构施工时,如何确定土仓压力的合理保持范围是减小地层扰动的关键。使用太沙基理论计算土仓压力时,存在深浅埋界限不明确、透水地层与不透水地层界限模糊等问题。根据成都地铁18号线所处地层、隧道尺寸以及埋深情况,基于土力学理论和DIN模型,提出适用于盾构隧道穿越弱透水地层的土仓压力计算模型,分析水压力在弱透水层中对土体有效应力的影响,得出弱透水层中横向土压力的表达式,并针对成都地区砂卵石+下伏泥岩的地层状况,通过数据统计拟合给出水头折减系数推荐取值。

It is the key to reduce the stratum disturbance by finding the reasonable range of the pressure of soil compartment in EPB shield tunneling. In the process of calculating the pressure with the Terzaghi theory, there are some problems, such as the ambiguity of the boundary between deep and shallow tunnels, and the ambiguity of the boundary between permeable and impermeable stratum. According to soil mechanics and DIN calculation model, a calculation model of pressure of soil compartment suitable for shield tunneling through impermeable stratum is proposed based on the tunnel size, depth and the stratum of the line No 18 of Chengdu metro. By analyzing the influence of water pressure on the effective stress of soil in impermeable strata, the expression of horizontal earth pressure in impermeable layer is presented. This paper provides the empirical value of reduction factor of water pressure by statistical fitting of data based on the stratum conditions containing upper pebble layer and lower mudstone layer in Chengdu area.