既有线下邻近大断面地铁双隧道暗挖施工对地表形变的影响

ISSUES AFECTING GROUND SUBSIDENCE INDUCED BY COVERED EXCAVATION FOR LARGE CROSS-SECTIONAL TWIN TUNNEL UNDER EXISTING STRUCTURES

以角门西站北京地铁十号线下穿地铁四号线的邻近双隧道暗挖施工为例,对既有线下大断面地铁双隧道暗挖设计施工因素对地表形变的影响进行数值模拟研究。提出并确定对大断面隧道开挖加固形成水泥土的参数选取方法,并利用监测资料进行校核和验证。建立二维有限元模型,对不同加固设计和暗挖施工方法等影响因素进行研究,对这些影响因素引起的地表沉降进行模拟分析,并和监测资料进行对比。研究成果可指导设计和施工,对实现设计最优化,降低工程对地面环境影响的风险具有较大意义,为今后的同类工程实践提供借鉴。

Based on a real project Jiaomen West Station in Beijing,details of two-dimensional finite element model for numerical analyses of surface ground subsidence are presented. Interpretation methods for parameters of soil-cement mixtures used to reinforce and pre-support excavation are proposed. Further numerical studies on the design and construction issues which significantly affect the ground subsidence caused by covered undercutting are then conducted. The study concludes that the proposed methodology to interpret the parameters of soil-cement mixtures is valid by comparing the simulation results and observed data. Moreover,the settlement trough under existing station structures is still in line with overseas research for Greenfield single tunnel,unconfined compressive strength of soil-cement mixture 1.5 MPa to 2.0 MPa is capable of making the excavation stable. The study also indicates that the surface ground subsidence has a correlation with pillar width.