超长倾斜联络通道冻结施工全过程有限元分析

FEM Analysis of the Whole Construction Process of Super-Long Inclined Connecting Passage by Freezing Method

在滨海软土地区开挖地铁联络通道时常采用地层冻结技术来提高土体的强度和稳定性,冻胀、管片及衬砌的应力集中、融沉等问题是冻结法施工过程中面临的巨大挑战。本文以天津地铁7号线某超长倾斜联络通道的冻结法施工为背景,使用ABAQUS软件建立三维热力耦合有限元模型,依照施工顺序对积极冻结期、维护冻结期和自然解冻期进行全过程数值模拟。结果表明:对于倾斜联络通道,地表的冻胀、融沉竖向位移均存在单向对称性,且隧道管片、倾斜联络通道衬砌应力分布非对称,在开挖支护过程中管片开口侧边中部及倾斜联络通道衬砌的尖角部分存在较大的应力集中,土体解冻后,倾斜联络通道的尖角部分和直墙拐角处应力集中值因冻胀压力释放而减小。

The ground freezing technology is usually used to improve the strength and stability of soil when excavating the subway connecting passage in coastal soft soil areas.Frost heave,stress concentration of segments and liners,thawing settlement etc.problems are great challenges in the construction process of freezing method.Based on the freezing construction method of a super long inclined connecting passage of Tianjin Metro Line 7,this paper uses ABAQUS software to establish a 3D sequential thermo-mechanical coupled finite element model to carry out numerical analysis of the whole process including active freezing period,maintenance freezing period and natural thawing period according to the construction sequence.The results show that for inclined connecting passage,the frost heaving and thawing vertical displacements of the ground surface are unidirectionally symmetric,and the stress distributions of the tunnel segment and the inclined connecting passage liner are asymmetric.During the excavation and support process,there are large stress concentrations in the middle of the opening side of the segment and the sharp corner of the inclined connecting passage liner.After the soil thaws,the concentrated stresses at the sharp corners of the inclined connecting passage decrease due to the release of frost heave pressure,as well as those at the corners of the connecting passage straight wall.