【作者】 吴梦军；

【导师】 张永兴； 刘新荣；

【作者基本信息】 重庆大学 ， 岩土工程， 2011， 博士

【摘要】 随着公路交通量的日益增大,六车道连拱隧道开始大量修建,而六车道连拱隧道一方面在设计上具有开挖跨度大和断面扁平的特点,为大跨扁平连拱隧道;另一方面,在施工过程中,由于其施工工序较多和左右洞施工的相互影响,围岩将受到多次扰动,衬砌结构也将受施工的多次影响,因此,其受力和变形极为复杂,施工时空效应和二次衬砌支护时机与四车道连拱隧道或分离式隧道存在较大的差异,这导致隧道在施工过程中容易发生围岩坍塌、衬砌开裂等质量安全事故。论文结合广东省交通科技计划资助项目“大断面连拱隧道设计施工关键技术研究”(200700021),以广(州)贺(州)高速公路六车道连拱隧道为依托,通过现场监控测试、相似模型试验、三维数值模拟、室内试验、理论分析等多种手段,对大跨扁平连拱隧道施工时空效应与二次衬砌最佳支护时机进行了系统深入的研究,主要研究内容包括:1、对依托工程施工过程中的位移-时间关系、位移-空间关系、支护结构应力-时空关系等进行了现场测试和统计、回归分析,并进行了基于APDL参数的优化反分析,得到了依托工程围岩变形、支护结构应力时空效应的实际发展规律,指导了依托工程的设计与施工,同时得到了围岩主要力学参数,为模型试验和数值模拟提供了依据。2、利用“公路隧道结构与围岩综合实验系统”,对大跨扁平连拱隧道在不同围岩级别与不同开挖方案条件下的施工全过程进行了相似模拟试验,成功地模拟了隧道开挖前掌子面围岩体内部发生的先期位移和开挖瞬间围岩体释放的弹塑性位移以及开挖后围岩体的蠕变变形,揭示了隧道围岩三阶段变形的全过程,并对施工全过程中的位移、应力随开挖步、空间的发生、发展规律进行了分析。对于开挖前的先期位移释放率和开挖前的应力释放率,两者基本相当,其中Ⅳ级围岩约为15～20%,Ⅴ级围岩约为20～25%。3、对大跨扁平连拱隧道IV级、V级围岩开挖时空效应以及IV级围岩复合式曲中墙动态施工过程进行了三维有限元数值模拟,分析了围岩位移、围岩与支护结构应力、屈服接近度等随时间和空间的变化规律,以及复合式曲中墙的动态施工力学行为,得到了各级围岩条件下开挖当前步位移与开挖前掌子面先期位移释放率。4、在最佳支护时机理论分析的基础上,提出了以“支护抗力最小”为原则,基于支护抗力现场测试的二次衬砌支护时机确定方法。同时,根据依托工程实测研究,对于大跨扁平连拱隧道Ⅴ级围岩,得出了“位移释放比87%,变形速率0.11mm/d”的支护时机确定准则。5、对于大跨扁平连拱隧道Ⅴ级围岩,分别利用支护抗力、变形速率、极限位移、粘弹塑性有限元等四种方法进行了最佳支护时机的计算分析,综合各方法计算结果,对于依托工程Ⅴ级围岩段,二次衬砌最佳支护时机建议取20~25d,距掌子面距离建议取35~45m。更多还原

【Abstract】 With the increasing road traffic, six-lane multi-arch tunnel are builded in large quantities. for the six-lane multi-arch tunnel, on the one hand, it has the characteristics of excavation large span and section flat, it is large span and flat multi-arch tunnel, on the other hand, due to the interaction of its more construction process and left-right hole construction during the construction process, surrounding rock will be repeatedly disturbed and lining structure will also impact many times by the construction. Therefore, its stress and deformation is extremely complex, there is difference form the four-lane multi-arch tunnel or separated tunnel on construction space-time effect and secondary lining supporting time and, at the same time, it will bring on surrounding rock collapse or lining cracking and other quality and safety incidents during the tunnel construction process. The paper combine the transportation science & technology GuangDong province project“Research on Design and Construction Key Technique of Large Section Multi-arch Tunnel”(200700021), rely on the six traffic lanes multi-arch tunnel of Guanghe freeway, through theoretical analysis, indoor experiments, three-dimensional numerical simulation, similar model test, field monitoring test and other means, has systematic in-depth study on construction space-time effect and optimal supporting time for the large span and flat multi-arch tunnel, include the following study content:1. Rely on the support engineering, through the site monitoring, statistics and the regression analysis, the displacement-time effect and supporting structure stress-time effect be studied, and carry through the optimization anti-analysis based on APDL parameters, get the actual development rule of the support engineering surrounding rock deformation and supporting structure stress space-time effect, supervise the design and construction of the support engineering, and get surrounding rock main mechanical parameters for the model test and numerical simulation.2.Through the“CTSSSRH”, large-scale Model testing for simulate the whole construction process of different surrounding rock and different excavation condition of large span and flat multi-arch tunnel is experimented, the testing successfully simulate preexisting displacement of internal tunnel face surrounding rock before tunnel excavation and elastic-plastic displacement of excavation instantaneous and creeping deformation after the excavation, reveal the whole process of surrounding rock three stages deformation, and analysis the development rule of displacement and stress. For the preexisting displacement before excavation and the stress release ratio is approximate equality,Ⅳclass surrounding rock is about 15～20%,Ⅴclass surrounding rock is about 20～25%.3.The three-dimensional finite element numerical simulation be performed, simulateⅤclass andⅣclass excavation space-time effect, and the middle wall dynamics construction mechanics ofⅣclass surrounding rock, analysis the space-time variation rule of surrounding rock displacement, surrounding rock and support structure stress, yield level coefficient and other, and dynamics mechanical behavior of composite curved middle wall, find the displacement release ratio of excavation current step and before excavation step under all class surrounding rock conditions.4. Base on the theory analysis of optimal supporting time, put forward the secondary lining supporting time determination method that according to“the support resistance minimum”principle, and found on the site monitoring of supporting resistance. And base on measurement of relying engineering, put forward the supporting time determination criteria of“displacement release ratio 87%, deformation rate 0.11mm/d”for large span and flat multi-arch tunnelⅤclass surrounding rock.5. For large span and flat multi-arch tunnelⅤclass surrounding rock, respectively calculation and analysis the supporting time through the follow four methods: resistance of support, deformation ratio, ultimate displacement, visco elastic plastic FEM, and comprehensive calculate the results of various methods, secondary lining optimal supporting time suggest take 20~25d, distance from the tunnel face suggest to take 35~45m.更多还原