【作者】 郑万坤；

【导师】 邵生俊；

【作者基本信息】 西安理工大学 ， 岩土工程， 2009， 硕士

【摘要】 西安地铁建造在黄土地裂区,如何保证地裂缝区间隧道运行期衬砌结构的整体稳定性是建设者们亟待解决的问题。以西安地铁隧道2号线工程为背景,结合地裂缝地层的地质条件和隧道施工方法,应用大型有限元软件FLAC,模拟施加开挖、地裂缝接触面、衬砌结构及上下盘地层相对竖向错动位移,对变形缝间距分别为5m、10m、15m的衬砌结构骑缝、跨缝方案,进行了三维有限元数值计算并进行比较分析；重点分析了变形缝间距10m衬砌结构骑缝时围岩与衬砌的力学响应变化特征；同时,考虑黄土流变特性,分析了地铁运行100年内流变对地裂缝区间隧道衬砌围岩力学性状的影响。地裂缝地层上下盘错动位移由下向上发展过程中,地裂缝接触面传递剪应力作用使得上部错动位移随埋深减小而减小,分析确定了计算模型地裂缝活动的位移边界条件。隧道开挖施工时,随着地裂缝接触面剪应力释放,地裂缝两侧围岩错动位移增长,从而削弱了衬砌结构运行期地裂缝活动引起围岩错动位移的发展。地裂缝错动位移作用下,衬砌结构骑缝穿越地裂缝时衬砌结构内力较小,上盘内衬砌结构腰部出现拉应力集中区域；上盘内拱顶、仰拱底围岩压力较下盘明显减小；下盘内衬砌结构变形缝间隙基本保持不变,上盘内衬砌结构变形缝间隙均增大,地裂缝处变形缝间隙增长最大；地裂缝两侧衬砌结构的相对沉降差较大,不利于变形缝防渗。衬砌结构跨越地裂缝时能有效地控制各变形缝沉降差的发展,有利变形缝防渗,但衬砌结构内力增大；地裂缝两侧变形缝间隙增长较大。变形缝间距10m衬砌结构骑缝穿越地裂缝时,随着地裂缝错动位移增大,围岩应力、衬砌结构内力及变形缝两端相对位移逐渐增大,变形缝处围岩和衬砌结构出现应力集中；下盘拱底围岩压力显著增大,上盘拱底围岩压力显著减小；衬砌结构最大拉主应力和最大压主应力分别为2.238MPa和5.510MPa;下盘内衬砌结构沉降明显,地裂缝两侧衬砌结构相对沉降差较大,但只有无衬砌结构时地裂缝错动位移的一半。建立了衬砌结构内力与地裂缝两侧沉降差的相关关系,给出了上盘仰拱底围岩加固处理的沉降差控制条件。初步分析了黄土的流变效应对隧道衬砌结构的影响。更多还原

【Abstract】 Xi’an Subway is built in the ground crack site. How to guarantee the whole stability of the lining structure under the impact of the ground crack is an extremely urgent problem for builders to be solved. For the background of Xi’an metro tunnel engineering and the geological conditions and tunnel construction method, the mechnics response of linning structure and surrounding soil was analyzed by the three-dimensions finite element software FLAC simulating the original stress field, excavation of tunnel, different structure measures with different length of lining structure of 5m,10m and 15m, and ground cracks interface with the relative displacement between upper and lower soil mass. It is important to emphatically analyze the mechanical responses of lining structure with 10m length under ground crack action. At the same time, considering the loess rheological effect in 100 years, the stress and displacement of lining structure was also calculated under the ground crack on subway.In the process of relatively vertical displacement development of strata at two sides of ground crack, the relatively vertical displacement of trata reduce gradually from lower to upper stratum due to the shear stress tranfered by the interface of ground crack..The displacement boundary condition on the bottom of finite model was determined by the relationbetween vertical displacement of strata and depth. When the tunnel excavated by new Austria menthod, the relative displacement between strata at two sides of ground crack increase further with the shear stress on the interface decreasing. So the relatively vertical diaplacement among lining structure at deformation sew reduce due to the ground crack movmation.Comparing with two kinds of scheme of lining structure with deformation sew, the internal force of lining structure is smaller for the scheme of lining strucrue with deformation sew at ground carack, and the zone of pulling stress lies at middle on lateral wall. The top and bottom earth pressures of lining structure in upper tratum are smaller than the earth pressure of ling structure under the lower stratum. The clearance of sew in upper stratum increases, and the clearance at ground crack increase significantly. The relatively vertical displacement between lining structure at ground crack is large. For the another scheme of lining structure through the ground crack, The relative settlement of all sew change small, it is good to ensure prevent seepage. But the internal force of lining structure is large. The clearance of sew at two sides of ground crack change large.For the scheme of setting deformation sew at ground crack and the length 10m lining structure between deformation sew, it is important that the pressure of wall rock and stress of lining structure, the the relative settlement at twe sides of deformation sew are analyzed respectively. With the relatively vertical displacement of ground crack increasing, the pressure of wall rock, internal force of lining structure and settlement at deformation sews change. When the relatively vertical displacement of ground crack equals 50cm, the stress centralization of wall rock and lining structure at ground crack appears. At the inverted arch of tunnel, the stress of wall rock on the lower stratum significantly increased, but the stress of wall rock on upper stratum significantly reduced. Maximum pull main stress and pressive main stress equals respectively to 2.238MPa and 5.510MPa.The settlement difference of lining structure ta deformation sews in the upper stratum distributes unevenly, and the relative settlement between lining structures at ground crack develop remarkably. In course of the operation of Xi’an subway, if the relative displacement between twe sides of deformation sew at ground crack reachs 15.54cm, or the difference of wall rock stress at the inverted arch of tunnel between twe sides of deformation joint at ground crack reaches 0.17 MPa, the lining structure and wall rock should be reinforced.When the relative displacement between upper and lower soil is small, the rheological effects of loess can be able to weaken the ground cracks on the impact of subway tunnels. With the relative displacement increasing, the ground cracks on the impact of subway tunnels have played an increasingly important role.更多还原