古土壤地层盾构施工引起的地表沉降分析

针对西安地铁上覆含有古土壤的黄土地层中盾构施工引起的地表沉降,在分析其产生机理、盾构施工数值模拟过程、基于经验公式的Peck地表沉降计算方法的基础上,探讨了基于注浆效果、支护压力以及偏心超挖的等代层厚度计算方法;具体分析了盾构施工数值模拟过程中的等代层弹性模量和掌子面支护压力比与Peck地表沉降计算公式中最大沉降量和沉降槽宽度之间的关系。研究结果表明,在含有古土壤的黄土地层中进行盾构施工数值模拟时,等代层模量的取值在5～10MPa范围之内,当等代层模量小于5 MPa时,隧道围岩将产生较大的塑性变形;掌子面支护压力比取值在0.5～1.0范围之内,当掌子面支护压力比小于0.5时,掌子面附近土体将产生较大的塑性变形,当掌子面支护压力比大于1时,地表将产生隆起变形。

Research on Ground Settlement of Shield Tunnelling in Paleosol Strata

According to the tunnel in paleosol strata of Xi′an subway,it is analyzed that the mechanism of the shield tunnelling-induced ground settlement,the numerical simulation process of shield tunnelling,and the Peck empirical equation the grouting filling ratio,the shield pitch ratio and the support pressure ratio are introduced into the calculation method of equivalent circal zone thickness.The relationship between the moduli of equivalent circle zone and the support pressure ratio,and the maximal settlement and the settlement troug width of the Peck empirical equation are researched.The following conclusions are drawn: when shield tunnelling in paleosol strata is simulated,the values range of equivalent circle zone moduli are from 5 MPa to 10 MPa.When the equivalent circle zone moduli are less than 5 MPa,the tunnel rock will cause plastic deformation.The values range of support pressure ratio is from 0.5 to 1.When the support pressure ratio is less than 0.5,the tunnel rock will cause plastic deformation.When the support pressure ratio is greater than 1,the ground will rises gradually.