合肥地区复合地层盾构掘进参数控制研究

Study on Parameters Control of Shield Tunneling in Composite Strata in Hefei Area

为保证合肥地铁盾构隧道的施工安全,基于合肥地层情况,通过PLAXIS 3D岩土有限元软件模拟穿越软土、硬岩及复合地层3种不同地层条件的盾构掘进过程,研究开挖面支护力N、盾构钢壳锥度引起的收缩率C和壁后注浆压力p对地表沉降和围岩变形响应的影响规律。研究结果表明:1)支护力N和注浆压力p对地表沉降的影响受地层和埋深的限制较大,收缩率C则相对较小;2)从地表沉降上看,盾构掘进参数(N、C、p)对软土层的影响最大,复合地层次之;3)p对管片上浮和管片内力的影响显著,不宜设置过高,软土层对p最为敏感,硬岩和软硬复合地层次之。最后,将这些影响规律应用于合肥地铁4号线某区间的盾构掘进参数控制中,结合现场数据分析,结果表明盾构掘进姿态正确,地表沉降稳定,掘进参数合理可靠。

In this paper,the shield tunneling process of Hefei Metro under 3 different strata conditions,i.e.soft soil,hard rock and composite strata,is simulated by geotechnical finite element software PLAXIS 3D.And then the influences of support force N of tunneling surface,shrinkage rate C caused by the taper of shield steel shell and grouting pressure p behind lining on surface settlement and deformation of surrounding rock are studied.The study results show that:(1)For the surface settlement,the stratum condition and burial depth have a greater limitation on N and p than that on C.(2)The impact of shield tunneling parameters(N,C and p)on surface settlement of soft soil layer is larger than that on surface settlement of composite strata.(3)The p has a significant influence on segment floating and internal force,which should not be overlarge;the soft soil layer is most sensitive to p,followed by hard rock and soft-hard composite formation.The study results are applied to the control of shield tunneling parameters in a section of Hefei Metro Line 4,and according to the fiel data analytical results,the shield tunneling attitude is correct,the surface settlement is stable,and the tunneling parameters are rational and feasible.