The subway tunnels built in some coastal cities often cross the soft and hard alternating strata, which makes the shield construction more difficult. The single shield mode cannot meet the needs of efficient construction and environmental protection, while the dual mode (TBM-EPB) shield can better adapt to the complex geological conditions of soft and hard alternating, effectively improve the tunneling efficiency of the shield machine, and ensure the safety and timeliness of project construction. Based on the construction practice of the tunnel between Liuxiandong Station and Bai mang Station of Shenzhen Metro Line 13 passing through long distance soft and hard alternating strata, this paper studies the shield machine mode used in the construction of this section, establishes the use of dual mode (TBM-EPB) shield, and conducts the development of a series of key technologies in the construction process such as dual mode conversion, pressure replacement screw conveyor, etc, The adaptability of double mode (TBM-EPB) shield to the long-distance soft and hard alternating strata between Liuxiandong Station and Baimang Station of Shenzhen Metro Line 13 is evaluated. At present, the project has been successfully completed, and its practical experience provides a reference for the promotion and application of TBM-EPB shield in tunnel construction under similar geological conditions.

在以淤泥或淤泥质土为主的珠三角地区开挖深基坑常采用钢板桩进行基坑支护,为保证支护结构的稳定性,对基坑底部被动区进行加固,合理的加固设计能在保证稳定的基础上减少支护成本.文中针对广东省佛山市地铁 2 号线林岳车辆段某基坑工程,建立被动区水泥土搅拌桩加固的基坑开挖支护三维数值模型,通过实测值与计算值对比,分析数值模型与计算参数取值的合理性;对基坑底部被动区无加固、水泥土搅拌桩加固和钻孔灌注桩加固时桩顶水平位移、桩身整体侧向位移、地表沉降、土体深层水平位移进行对比分析.结果表明,基坑底部被动区采用水泥土搅拌桩或钻孔灌注桩加固可减小钢板桩围护结构 60%的侧向位移,水泥土搅拌桩对开挖深度小于6m的基坑的加固效果最佳;采用钻孔灌注桩加固,开挖深度为 10m 时,桩身整体侧向位移比被动区无加固时减小 69.2%,比水泥土搅拌桩加固时减小 65.1%,对围护结构整体侧向位移的控制效果比水泥土搅拌桩好.

Abstract With the rapid increase in the number of urban subway construction in China, the geological distribution encountered in the tunnel construction process is gradually diversified, especially when the excavation is carried out in the upper soft and lower hard formations, there are certain differences in the physical and mechanical properties of the tunnel palm surface, the surrounding rock and the distribution position of the soft and hard rock junction surface, which can easily lead to the occurrence of large deformation or even collapse of the surrounding rock of the tunnel. In order to study the deformation of surrounding rock and the change of surface settlement when the shield tunnel crosses the upper soft and lower hard strata, relying on the actual project of the shield tunnel crossing the upper soft and lower hard strata of Shenzhen metro line 13. Firstly, based on the molar stress circle theory and the theory of elastic mechanics, the influence of internal friction angle and cohesion on the surrounding rock stress is analyzed, and the first yield location and distribution characteristics of the surrounding rock stress of the upper soft and lower hard strata are divided based on the calculation formula of the surrounding rock stress; Secondly, the inclination angle of the soft and hard rock junction surface of the above soft and hard formations is α variable, and the MIDAS GTS NX numerical simulation software is used to set seven working conditions of 0°, 15°, 30°, 45°, 60°, 75°, 90°, and analyze the influence of inclination on the surrounding rock stress of the tunnel, the plastic yield position of the surrounding rock, and the deformation of the surrounding rock. Finally, the surrounding rock deformation and surface settlement monitoring data after the completion of the construction of the soft and lower hard strata in the Liu ~ Bai section of Shenzhen Metro Line 13 are summarized, and the numerical simulation is compared and analyzed to verify the accuracy of the numerical simulation results, and the final research results can provide a certain reference for similar projects in the later stage.

盾构隧道穿越复合地层时,由于掌子面上下岩体软硬不均,极易导致盾构机掘进参数出现大幅波动.目前,针对复合地层盾构掘进参数的预测并未考虑地层物理力学参数变化和复合地层岩土占比.依托深圳地铁13号线复合地层段现场掘进数据,首先,根据掘进数据规律提取运行段数据,对运行段数据进行离群检测,去噪与标准化预处理;而后,利用BP神经网络,以刀盘转速、推进速度、螺旋机转速和上下两层岩土占比、岩土体的岩石单轴极限抗压强度标准值、岩土施工工程等级作为输入参数,预测总推力、刀盘扭矩这两个控制盾构机运行主要参数.计算结果表明:(1)对于不同占比的训练集和测试集,预测结果与实测结果吻合度较高,且随着训练集占比增大,预测平均误差逐渐降低,在80％训练集时,刀盘扭矩与总推力的平均相对误差分别为9.2％和7.1％;(2)预测模型对不同复合地层条件下的平均误差在15％以内.

隧道采用盾构法施工时,不同盾构模式的适用地层往往不同,因此在保证隧道安全施工的同时,研究不同盾构开挖模式在同一类地层中的掘进效率,进而选择合适的盾构掘进模式来保证隧道高效掘进具有重要意义.依据深圳地铁13号线留仙洞站—中间风井区间双模盾构(TBM-EPB)工程,通过分析TBM(tunnel boring machine)模式、EPB(earth press balance)模式在硬岩段的掘进参数,得出TBM模式相较于EPB模式于硬岩段掘进效率的提升程度.当隧道掘进地层为长距离软硬相间地层时,在硬岩段掘进时TBM模式的掘进性能要优于EPB模式,说明了硬岩段采用TBM模式掘进的必要性.该研究成果可为今后双模盾构类似工程的掘进效率分析提供参考.

通过对TBM-EPB双模盾构的理论研究分析,同时结合深圳地铁某项目TBM-EPB双模盾构掘进的工程实例,对TBM-EPB双模盾构的优缺点进行详细叙述,可供相关工程盾构选型参考.

为了研究基坑围护结构水平位移影响因素的敏感性程度,以深圳市城市轨道交通13号线13101标段留仙洞站为依托,首先,采用有限元软件ABAQUS建立三维数值模型,对基坑开挖与支护的全过程进行数值模拟计算;其次,选取围护结构厚度、围护结构入土深度和砼支撑轴力3个影响因素,采用正交试验法实现了9种不同情况的数值模拟试验,并对试验结果进行极差分析.研究结果表明:当基坑开挖完毕时,围护结构产生的最大水平位移为25.59 mm,发生在基坑东侧13轴桩身标高11 m深度处,该位移值没有超过其监测控制值30 mm,满足基坑开挖安全性的要求;各影响因素对围护结构水平位移的敏感性程度由大到小依次为砼支撑轴力、围护结构入土深度、围护结构厚度.

针对基坑开挖施工安全问题,以深圳市城市轨道交通13号线13101标段三工区留仙洞站基坑工程为依托,对基坑不同施工阶段桩体深层水平位移、地表沉降、锚索拉力、地下水位等监测数据进行分析,总结了地铁车站施工期间基坑变形规律.结果表明:各测点变化速率处于相对稳定状态,无异常值,变形稳定,且周边环境巡视无异常.

岩体力学参数的选取,对岩体工程稳定性分析至关重要,基于Hoek-Brown强度准则的岩体力学参数取值,受岩体工程地质特性主观判断的影响.本研究采用节理特征系数与岩块体积数等参数,对地质强度指标进行取值量化.利用Hoek-Brown强度准则,获得等效岩体抗剪强度参数的计算方法,并基于边坡分析,探讨了不同岩性时,节理起伏系数、蚀变系数及粗糙系数等因素对岩体抗剪强度参数的影响规律.以某工程案例分析了各因素对岩质边坡安全系数的影响规律.研究结果表明:当节理蚀变系数为4～8、节理组间夹角为60°～80°、节理起伏系数为2～3 m、节理粗糙系数为2～3 cm和节理平均间距为900～1000 mm时,节理参数的变化对黏聚力及内摩擦角的影响较小.当地质强度指标>70或扰动系数为0.6～1时,其对岩体力学参数取值及岩质边坡稳定性分析结果影响较大.应增加各因素的测试范围,获取更多测试数据,减少分析误差.

In this paper, based on Chongqing New Songjiagou No. 1 Tunnel reconstruction project, detailed research aimed at Ⅴ grade section of tunnel surrounding rock expansion construction technique problem is carried out. Based on the investigation and analysis of existing similar projects and the actual project, the original design of the CD method is optimized as the tri-bench excavation method under the advanced small pipe support. The feasibility of the method is analyzed through numerical simulation, and the key process control points of the optimized construction scheme are pointed out. Practice shows that the tri-bench excavation method with advanced small pipe support in Ⅴ grade surrounding rock in-situ expansion tunnel is feasible, the monitoring indicators are within a reasonable range, compared to other related methods, which has more obvious technical and economic advantages.

Based on the basic of Shenzhen Urban Rail Transit Line 9 Ludan village station with rich water,shallow buried large section soil,under the soft hard standing after crossing the line tunnel construction experience,the authors change the traditional idea method step excavation sequence and support,for the first time,the application of shallow tunnel cross braces underground cut construction method is taken in this paper.While cross braces will straighten hold the original temporary support by arc which prior to the temporary support recycling reuse,and the environment will be saved.To prevent tunnel subsidence and peripheral convergence,in arch shoulder additional temporary braces,rich water conditions,elaborated in the small pull slot drainage construction in the middle.At the same time,early in order to speed up the speed loop,the inverted arch will be completed in one time.In weak rock underground subway construction,the construction progress will be speed up,cost will be saved,at the same time,the convergence problem is effectively controlled.