地铁盾构隧道施工对邻近管线的影响分析

为了获得地铁隧道盾构法施工对临近地下管线的变形和应力的影响规律,以大连地铁二号线某区间隧道工程为背景,利用FLAC3D软件对隧道盾构施工引发的地层变形所导致的管线变形、应力进行了精细模拟,得到双线隧道施工完成后横向地表沉降槽不符合叠加理论,存在少量差值,双线隧道贯通时最大沉降值为11.26 mm,盾构隧道地层体积损失率为1.46%,地表沉降槽宽度系数为0.81.按两条隧道互不影响沉降叠加,最大沉降值为11.93 mm;右线隧道贯通时,燃气管最大沉降值为10.1 mm,左线隧道贯通时,燃气管最大沉降值为11.4 mm,最大沉降位置向左有少量偏移.随着右线盾构掘进施工,污水管道沉降逐渐增大,最大沉降变形为5.45 mm,线隧道贯通后,污水管线最大沉降值为9.79 mm.整个过程两管均处于安全状态.     

Study on toughening on crack prevention of jointed rock masses with different pre-stress anchor cables

The major reason of the failure of jointed rock-mass is the formation of the plastic zone near the crack tip of I-II mixed crack which leads to the growth, propagation of the branched crack under load condition. In the paper, the failure judgment of mini-plastic zone??s displacement is derived by the Mises yielding rule. The anchor cable is simulated by the different link elements and inflicting pre-strains according to the difference of mechanism of the consolidated segment and free segment. The stress and strain fields near crack tip of twain collinear cracks of different angles and consolidated conditions are simulated by iso-parametric element with eight nodes. The iso-parametric element with eight nodes is degenerated to singular element at crick tip to simulate crack. It is shown that the mini plastic zone??s displacement near the crack tip begins to increase, then decreases with the increase of the angle of the crack. The better consolidated condition is, the smaller the angle of crack tip is when the mini plastic zone??s displacement near the crack tip arrives at the biggest value. The mini plastic zone??s displacement near the crack Tip 2 is bigger than that near the crack Tip 3. The crack is easier to failure with the increase of load.     

Analysis of localization of Mohr-Coulomb strength law with damage effect

The damage critical curved surface is derived by considering the related effect of isotropic damage and degradation of cohesion and internal friction angle of Mohr-Coulomb strength law. The characteristics of stress-displacement curve and networks of shear bands with the change of degree of damage, confining pressure and Poisson??s ratio are investigated numerically by monitoring the stress-displacement values in the process of deformation of samples under plane strain and different initial conditions. The dependence of elastic-plastic response of localization is discussed. The non-uniqueness of the solution of equation is given. The orientation angle of shear band is derived by considering the related effect of isotropic damage and degradation of cohesion and internal friction angle. The orientation angle of shear band obtained by numerical simulation is contrasted to the orientation angle by measuring Mohr circle. It is shown that peak strength and residual strength depend on confining pressure. The networks of shear bands begin to appear in phase II of elasticity and develop in soften phase, and the shear band is formed in the phase of residual strength. As the degree of damage increases, axial displacement at the points of bifurcation and shear band decreases. The orientation angle of shear band increases with the increase of the damage degree. The orientation angle of shear band obtained by numerical simulation and measuring Mohr circle is not much difference when the damage degree is equivalent. The Mohr-Coulomb theory may predict the localized instability of sample by considering the degradation of cohesion and internal friction angle.     

大连地铁109标段施工监测研究

针对大连地铁109标段施工过程进行监控量测,分析施工过程中边坡稳定性问题.主要采用电子水准仪二等水准测量方法对边坡沉降进行观测,并采用全站仪对边坡水平位移进行施工过程中的监控量测,全面分析了施工过程中的沉降及水平位移数值变化规律.结果表明:明挖基坑坡顶监测点累计最大沉降值为9.2mm,最大水平位移为17.8 mm,均符合规范要求,施工过程中边坡基本稳定,能够保证安全施工,可为同类工程施工监测提供参考.     

地铁盾构双隧道施工诱发的地层变形规律分析

以大连地铁202标段双隧道盾构施工工程为背景,考虑土体的分层以及隧道施工过程中盾构推进、注浆和衬砌拼装等工序,运用FLAC3D软件对盾构双隧道同向先后施工过程进行三维精细数值模拟,并与现场测量数据进行对比分析.结果表明:先施工的右线隧道掘进完成后,隧道上方各层土体越靠近地表,盾构施工引起的地层竖向变形越小,而地层的沉降槽宽度越大,地表沉降槽宽度系数为0.56;近距离双隧道同向先后开挖时,土体相互扰动,地层距离隧道轴线的高度越小,地层竖向变形非对称“双峰”特征越明显,岩层的成层性使得双峰特征消失时岩层距离隧道轴线的高度有差别;两隧道中心线和轴线附近地表有不同方向水平变形,此区域的桩基、剪力墙在隧道掘进时将受到附加剪切作用,易出现裂缝,故在施工中应做好切实的防护措施;监测结果验证了数值模拟方法的正确性,在盾构掌子面距离监测点12 m范围内,地表沉降发展得较快.     

细砂增强偏高岭土基地质聚合物力学性能细观研究

为提高偏高岭土基地质聚合物力学性能,制备了掺有标准砂及细砂的地聚物复合物.设置对比组,通过无侧限抗压测试及PFC3D颗粒流模型研究了细砂粒径及掺入量对偏高岭土基地聚物力学性能的影响.结果表明:15％最大质量分数的标准砂可以小幅提高地聚物的抗压强度,在室温环境下养护28 d后试件强度达到25.40 MPa.细砂可以大幅提...     

地铁盾构隧道施工对地层变形影响的三维数值模拟

以南京地铁玄武门—新模范马路区间隧道盾构施工工程为背景,使用FLAC3D软件在考虑盾构隧道施工中的开挖、排土、衬砌等步序的前提下,进行盾构隧道掘进施工对地层变形影响的三维数值模拟.结果表明,在盾构掘进施工过程中,地层沉降具有明显的时间效应;地表沉降量随之逐渐增大;地层横向沉降变形随着地层埋深的增加,最大沉降值逐渐增大,沉降槽宽度逐渐减小;地层沉降历时曲线呈现出反"S"形.