【作者】 刘小军；

【导师】 张永兴；

【作者基本信息】 重庆大学 ， 岩土工程， 2011， 博士

【摘要】 隧道洞口围岩稳定性是整条隧道建设的重中之重,隧道洞口大多具有浅埋和偏压的特征,洞口围岩易于风化,围岩性质极差,且易受到降雨的影响。由于隧道洞口围岩软弱,为了保证稳定性,需考虑其在开挖过程中所具有的蠕变特性,同时由于极易受到降雨的影响,还要考虑不同含水状态下洞口围岩的蠕变特性,目前此方面的研究还很有限,而对于浅变质碎裂围岩不同含水状态下的蠕变研究更为少见。本文结合贵州省科技厅重大专项《厦蓉线水都高速公路建设关键技术研究》之子课题四《厦蓉线水都高速公路隧道洞口段设计与施工关键技术研究》,以厦蓉高速公路贵州境内水都线的典型隧道洞口为依托工程,在充分利用已有研究的基础上,采用试验研究、数值模拟、现场监测和理论分析相结合的研究方法,对隧道洞口浅变质碎裂围岩的蠕变特性及其在隧道洞口工程中的应用等进行了较为系统和深入的研究。论文的主要研究工作包括:①工区碎裂浅变质板岩基本力学特性及不同含水状态下压缩蠕变特性试验研究。通过常规单轴及三轴试验,得到自然风干及饱和状态下碎裂浅变质岩各项基本力学特性参数;通过泡水试验,得到碎裂浅变质岩饱和度与泡水时间的关系;基于不同含水状态下碎裂浅变质岩压缩蠕变试验,获得不同含水状态下的应变-时间曲线,分析得到不同应力及不同含水状态下碎裂浅变质岩的蠕变变化规律。②考虑含水损伤的碎裂浅变质板岩蠕变本构模型开发及验证。根据试验结果进行模型辨识,引入岩石含水损伤概念并定义含水损伤因子,通过试验结果等到含水损伤变量演化方程;然后建立考虑含水损伤的碎裂浅变质岩蠕变方程,并进行了三维应力状态下的推广;随后基于有限差分理论,推导得到其有限差分格式,利用FLAC3D进行本构模型二次开发,并通过实例进行验证。③工区浅埋偏压隧道洞口开挖围岩力学行为及施工工序优化研究。建立大型三维仿真地质模型,利用开发的本构模型通过数值分析对工区隧道洞口采用的较为繁杂的环形导坑预留核心土法以及CRD法的合理开挖工序进行优化研究,得到了基本原则。通过对施工全过程中围岩的力学行为研究,得到了分部开挖过程中考虑施工期蠕变特性的围岩受力变形特征,得出的结论可为合理施工提供参考。④浅埋偏压隧道稳定性与地形因素间关系。由于目前已有研究只是针对具体工程展开,不够系统全面。故综合考虑对浅埋偏压隧道围岩稳定性有直接影响的地形因素,包括侧覆土厚,横坡坡度、最大埋深等,通过正交试验法进行数值模拟试验方案的设计,经计算得到各影响因素与浅埋偏压隧道稳定性的关系。⑤浅埋偏压隧道洞口段预加固技术研究。在获知地形因素对浅埋偏压隧道影响规律的基础上,针对不同类型的洞口段,采用FLAC3D软件对采取各种预加固措施后的隧道洞口进行了模拟计算分析,通过与未进行预加固和进行不同的预加固时隧道应力、变形特征的对比,得到了与隧道类型相适应的预加固措施的选取原则,并在此基础上提出碎裂浅变质岩地区不同类型隧道洞口段的预加固技术要点。⑥碎裂围岩浅埋偏压隧道衬砌荷载算方法研究。目前,围岩压力计算理论较多,而针对浅埋偏压隧道围岩压力的计算方法极少。公路隧道规范分别给出了浅埋和偏压隧道的计算方法,对于偏压隧道的计算方法,计算思路直接来源于浅埋隧道的计算理论,其假设与实际情况有较大出入。针对此种情况,根据现场实测资料及数值分析结果确定碎裂围岩浅埋偏压隧道的破坏模式,然后利用极限平衡分析法推导得到了支护荷载的计算公式。更多还原

【Abstract】 Stability of surrounding rock around tunnel portal is very important to the entire tunnel construction. Tunnel portals are shallow and unsymmetrical loading in most cases, and the surrounding rock likely in poor performance, easily weathered and affected by rainfall. In order to ensure the stability of the excavation process, rheological properties and creep under different water content should be considered. At present, research in this area is still very limited,especially creep of cataclastic low-grade metamorphic rock fragments under different water status.In view of this, based on the support projects of typical tunnel entrances of Xiamen-Chengdu expressway in Guizhou province, combined with the existing research, more systematic and in-depth study on creep of low-grade metamorphic rock fragments around tunnel portal and application in the tunnel entrance engineering were conducted. The main contents of this paper as following:①Study on the basic mechanical properties and compression creep of low-grade metamorphic slate from project region. Several basic mechanical parameters under natural air-dry and saturation were determined by conventional uniaxial tests and triaxial tests. The relationship between saturation and soaking time were obtained by water immersion tests. Strain-time curves under different moisture content were gained by creep tests, and the creep law of low-grade metamorphic slate under different stress and moisture content were analyzed.②Development and verification of creep constitutive model of low-grade metamorphic slate considering water damage. Identifying the model by test results, introducing concept of water damage of rock and defining the factors, and the damage evolution equation is derived from the test results. Creep equation of low-grade metamorphic slate considering water damage was established, and extended to three-dimensional stress state. Then the derivation of finite difference equations was played in the basis of finite difference theory, and combined with the environment of FLAC3D to complete model of the secondary development, which is verified by examples.③Research on the mechanical behaviors of dynamic construction and excavation process optimization of the shallow tunnel under unsymmetrical loadings. Large-scale three-dimensional simulation geological model were built to study the optimization of excavation process comparing the annular pilot heading conservation core soil method and CRD method using developed model, and some basic laws obtained. The analysis results of stress characteristics of surrounding rock and supporting structures can provide technical guidance for the design and construction of tunnel which has the similar topographical and geologic conditions.④The relations between stability of the shallow and unsymmetrical loadings tunnel and topographic factors. Most of the existing research focuses on practical engineering, lacking of general applicability. So, topographic factors such as thickness of side covering soil, transversal gradient, maximum burial depth and so on were considered to design orthogonal tests to study the relationship of factors affecting the stability of the shallow and unsymmetrical loading tunnel.⑤Research on the pre-reinforcement technology of portal section of shallow tunnel with unsymmetrical loadings. For different types of portal section, calculation and analysis were performed using FLAC3D software to comparing the stress and deformation characteristics of tunnel under different pre-reinforcement technologies. Principles of selecting compatible pre-reinforcement technology for different types of portal section were obtained. On this basis, several pre-reinforcement technical points were proposed.⑥Research on the calculation method of lining loads of shallow tunnel with unsymmetrical loadings. There are many theoretical calculations of rock pressure, while few for shallow tunnel with unsymmetrical loadings. The highway tunnel specification gives the calculation method of shallow tunnel and unsymmetrical loaded tunnel respectively. The calculation theory of unsymmetrical loaded tunnel is similar with the shallow tunnel, and the assumptions are different from the actual situation. Therefore, a series of corresponding formulas are deduced based on limit equilibrium theory for calculation lining loads of shallow tunnel under unsymmetrical loadings through engineering case analysis and the three-dimensional numerical analysis results of the tunnel更多还原