富水砂卵石地层地铁联络横通道人工冻结数值分析

Numerical simulation of artificial ground freezing for cross passage of subway in water-rich sandy cobble stratum

人工地层冻结法作为一种常用的土层加固方法,被广泛应用于煤矿、地铁等地下结构工程中。成都地区的砂卵石地层含水量丰富,渗透系数大,实施冻结法难度更大。以成都地铁10号线某隧道区间为工程依托,研究采用人工冻结法在砂卵石地层中修建联络横通道的问题。对冻结工程进行现场监测,根据冻结管实际布置形式建立考虑冰水相变的非线性三维弹塑性热—力耦合数值模型,通过现场监测和数值模拟两种手段对积极冻结期温度场和位移场的发展及分布规律进行研究。结果表明:数值模拟结果与现场监测数据吻合较好,建立的数值模型比较可靠;冻结壁交圈时间是冻胀变形快速增长的临界时间点,交圈时间约为25 d;冻结43.7 d时冻结壁厚度达到2 m,在37.8 d时冻结壁内平均温度达到-10℃,满足后续开挖施工要求。

As a common soil reinforcement method,artificial ground freezing method is widely used in underground structure engineering such as coal mine and subway.The sandy cobble stratum in Chengdu has rich water content and high permeability coefficient,where is difficult for freezing method.In this paper,the construction of cross passage by artificial freezing method in sandy cobble stratum was examined based on a tunnel section of Chengdu Metro Line 10.Firstly,the field monitoring of freezing engineering is carried out.Secondly,a nonlinear three-dimensional elastic-plastic thermal-stress coupled numerical model considering ice water phase transformation was established according to the actual layout of freezing pipes.The development and distribution of temperature field and displacement field in active freezing period were studied by field monitoring and numerical simulation.The research result shows that the numerical simulation results were in good agreement with the field monitoring data,and the established numerical model was reliable;the time of closure of freezing wall is critical for rapid growth of frost heave deformation,and the time is about 25 days;the thickness of frozen wall reached 2 m for freezing of 43.7 days,and the average temperature in the frozen wall reaches-10℃in 37.8 days,which meets the requirements of subsequent excavation construction.