【作者】 陈志敏；

【导师】 赵德安；

【作者基本信息】 兰州交通大学 ， 岩土工程， 2012， 博士

【摘要】 隧道支护结构受力的大小是隧道结构设计、施工的一个基本依据。岩体开挖后受扰动而产生应力重分布过程极其复杂,尤其是在不良地质环境下更甚。国内外工程中,很多隧道遇到了挤压大变形问题,如奥地利的陶恩隧道(Tanern)、阿尔贝格隧道(Arlberg)和日本的惠那山隧道(Enason),国内的家竹箐隧道、乌鞘岭隧道、新关角隧道及木寨岭隧道等,都具有围岩软弱、地应力较高、变形大且持续时间长等特点。在高地应力软弱围岩条件下修建隧道,由于软岩本身自稳能力差、塑性变形大,且具有明显的流变性,如对围岩变形、应力变化规律不了解或支护结构不合理,往往会发生过量变形而使隧道坍塌。因此,对于地质条件差、地应力为高和极高的软弱围岩,其结构受力大小与受力特征对隧道结构安全尤为重要。国内外许多专家学者已对高地应力和软弱围岩等问题做了大量研究工作,但在地下工程围岩压力研究中仍然存在不少问题。比如,现有本构关系对高地应力软岩尚不具有广泛代表性,开挖应力释放率很难在高地应力软岩隧道中应用等。针对目前研究中存在的问题,结合工程中出现的问题和实际需求,本文以高地应力软弱围岩条件下的关角隧道、木寨岭隧道等工程为背景,通过地应力现场实测、理论研究与数值分析,对高地应力软岩隧道围岩压力和围岩与支护结构相互作用机理进行了研究与应用。主要进行了以下几方面的研究工作：(1)地应力是隧道围岩压力产生的根本来源。为获得高地应力分布规律,本文在中国地应力场分布规律统计分析基础上,统计得到我国青藏地区平均水平地应力与垂直地应力的比值随深度变化的分布曲线。从而,总结出了青藏地区地应力分布规律与特点,为判别该区域地应力测试结果的合理性提供了依据。该规律在兰渝线天池坪隧道和两水隧道地应力现场实测中得到了应用。(2)在构造应力复杂的地区,只能通过实地量测获得原始地应力。本文采用水压致裂法进行了兰渝线天池坪隧道和两水隧道地应力现场实测。在此基础上,分析了隧道所处的原始高地应力水平及隧道开挖后的地应力分布规律；采用改进的BP神经网络进行了木寨岭、天池坪等隧道的宏观地应力场拓展分析,获得了地应力的宏观分布形态与特点。(3)针对现有本构关系对高地应力软岩尚不具有广泛代表性和卡斯特耐尔公式无法直接计算出在塑性区范围不同发展过程对应的塑性形变压力的问题,以原岩应力和隧道容许位移(或支护后实际量测位移)为出发点,采用岩体软化“直-曲-直”模型,推导了隧道形变压力计算公式。本文称为“卡斯特耐尔扩展公式”。通过经典实例分析和在木寨岭隧道高地应力V级软岩段成功应用,验证了该公式的正确性和实用性。(4)由于高地应力软岩隧道中存在的开挖面通过之前的监测位移很难获得和实测位移存在缺失等问题,基于原岩应力和实测位移曲线的开挖应力释放率模型无法应用于高地应力软岩隧道。本文利用台阶法开挖中存在的空间效应和改进的BP人工神经网络模型预测位移以及多项式拟合预测方法,提出了两类在高地应力软弱围岩条件下使用开挖应力释放率模型的方法。通过在关角隧道和木寨岭隧道大战沟斜井高地应力软岩地段的应用,探讨了其结构荷载与应力释放规律,其结果得到三维数值分析的验证。(5)为验证卡斯特耐尔扩展公式合理性,基于参数全过程变化的应变软化FLAC3D三维数值模型,模拟了木寨岭隧道正洞高地应力软岩地段隧道开挖支护过程。三维数值结果与卡斯特耐尔扩展公式计算结果吻合,进一步证明了该公式在高地应力软弱围岩条件下应用的可靠性、适用性。本文在统计青藏地区地应力分布规律基础上,结合现场实测和拓展分析,准确获得高地应力软岩隧道位置原始地应力,为研究围岩压力和围岩与支护结构相互作用机理提供依据。在原始地应力基础上,结合理论分析和数值仿真,获得了高地应力软岩隧道的围岩压力计算方法和围岩与支护结构相互作用机理。本文主要创新点体现以下四个方面。(1)首次统计分析得到了我国青藏地区平均水平地应力与垂直地应力的比值随深度变化的分布曲线,总结了青藏地区地应力分布规律与特点,为判别该区域地应力测试结果的合理性提供了依据,也可为该地区的深埋地下工程勘察、设计和施工提供参考。(2)针对高地应力条件下软岩隧道大变形问题,引入岩体软化“直-曲-直”模型,推导出适用于高地应力软岩隧道基于原岩应力和隧道位移的隧道形变压力计算公式。(3)针对高地应力软岩隧道中存在的开挖面通过之前的监测位移很难获得和实测位移存在缺失等问题,提出了两类在高地应力软弱围岩条件下使用开挖应力释放率模型的方法。(4)在三维数值分析中,为反映软弱围岩参数随坑道变形而不断变化的特点,引入参数全过程变化的应变软化模型,利用FLAC3D软件验证了卡斯特耐尔扩展公式应用于高地应力软岩隧道的可靠性和适用性。本文在高地应力软岩隧道围岩压力和围岩与支护结构相互作用机理方面获得的这些新的认识与规律,可为高地应力软岩隧道的设计与施工提供重要的理论依据,更期望能够为高地应力软岩隧道的研究起到一定的推动作用。更多还原

【Abstract】 The supporting structure load is a very important basis for the design and construction of tunnels. The stress redistribution process is very complicated due to the rock mass excavation, and it would be more complicated in bad geological environment. The large extrusional deformation problems were met in many domestic and overseas tunnels, such as Tanern tunnel, Arlberg tunnel in Austria, Enason tunnel in Japan, Jiazhujing tunnel, Wushaoling tunnel, new Guanjiao tunnel and Muzhailing tunnel in China. There are many common characters existed in these tunnels such as weaknesses, higher geostress, large deformation and long duration, etc. If the rules of surrounding rock deformation and stress redistribution are not understood or the supporting structure is unreasonable, excessive deformation and even collapse would be happened in the weak rock tunnels with high geostress because of poor self-stability, large plastic deformation and the obvious rheological properties for the tunnels in weak rock. Therefore, the structural loads and characteristics are especially important for the tunnels in the weak rock tunnels with high geostress.There are still problems existed in underground engineering calculation theory, even though much worch has been done for the weak rock tunnels with high geostress. For example, the existing constitutive relationships can’t be applied in all conditions, especially for the weak rock with high geostress. Kastner formula can’t calculate the plastic deformation pressures corresponding to the different deformation process. The study of this paper was done based on the problems existed in the current research, the practical engineering problems and the actual demand. Based on the weak rock tunnels with high geostress such as Guanjiao tunnel and Muzhailing tunnel, the surrounding rock pressure and interaction mechanism between surrounding rock and supporting structure in the weak rock tunnels with high geostress were researched and applied through the geostress in-situ measurement, theoretical research and numerical analysis. The main works of this paper can be described as the following items.(1) The surrounding rock pressure is based on the geostress. The geostress rules of qinghai-tibet areas were summarized through the statistical analysis of in-situ measurement results. These rules can be applied to judge the rationality of the in-situ geostress field measurement of qinghai-tibet areas. The geostress in-situ measurement results of Tianchiping tunnel and Liangshui tunnel were judged by the geostress distribution rules of qinghai-tibet areas.(2) If the tectonic geostress is very complex, the only method to get original geostress is the in-situ measurement. In this paper, the geostress data of Tianchiping tunnel and Liangshui tunnel in LanYu railway line were in-situ measured using the hydraulic fracturing method. Based on the in-situ measurement data, the high geostress level and stress distribution rules around tunnel after excavation were analyzed. The macro distributions of Muzhailing tunnel and Tianchiping tunnel were analyzed by the improved BP network.(3) Based on the problems existed in the current research, the tunnel deformation pressure formula were derived adopting the rock mass softening "straight-curve-straight" model and considering the original geostress and tunnel allow displacement (or the actual measurement displacement) as a starting point. In this paper, this formula is called "Kastner extension formula". The correctness and practicability of the formula were validated by a classic example analysis and the successfully applicaion in Muzhailing tunnel.(4) The algorithmic model of the excavation stress release ratio is based on the original geostress and the measured deformantion curve, but it can’t be used in the weak rock tunnels with high geostress because of the two existing problems in the excavation. Based on the space effect existing in the excavation of tunnel and forecast methods of improved BP artificial neural network and polynomials, two kinds of methods were put forward for the model to be applied in the weak rock tunnels with high geostress. The two kinds of methods were used in actual tunnels. The rules of structure load and stress release in the weak rock section of GuanJiao tunnel and Muzhailing tunnel were discussed, and their results were also validated by3D numerical analysis.(5) In order to validate the rationality of "Kastner extension formula", the construction process in the weak rock section of Muzhailing tunnel was simulated by3D numerical analysis based on the strain soften model, in which the parameters of surrounding rock changes with strain. The3D numerical results were consistent with the results of "Kastner extension formula". The reliability and applicability of "Kastner extension formula" were proved that it can be used to calculate the deformation pressure of weak rock tunnels with high geostress.Based on the geostress statistical rule of the qinghai-tibet areas, the geostress distribution in the weak rock tunnels with high geostress can be got by the geostress in-situ measurement and continuation analysis. The original geostress is the basis of the study of surrounding rock pressure and interaction mechanism between surrounding rock and supporting structure. Based on the original geostress, the calculation methods and interaction mechanism between surrounding rock and supporting structure in the weak rock tunnels with high geostress were put forward combined with the theory analysis and numerical simulation. In this paper, four main research results were achieved as followings.(1) The geostress rules of qinghai-tibet areas were summarized for the first time. These rules can be applied to judge the rationality of the in-situ geostress field measurement of qinghai-tibet areas. These rules can also be refereced by the reconnaissance, the design and the construction of deep buried underground engineerings in qinghai-tibet areas.(2) According to the large deformation problems of the weak rock with high geostress, the tunnel deformation pressure formula, which can be used in weak rock tunnels with high geostress, were derived adopting the rock mass softening "straight-curve-straight" model.(3) Based on the two existing problems in the excavation, two kinds of methods were put forward for the algorithmic model of the excavation stress release ratio to be applied in the weak rock tunnels with high geostress.(3) To show the characteristic that the weak rock parameters would be changed during the rock deformation process, the strain soften model, in which the parameters of surrounding rock changes with strain, was adopted in the3D numerical analysis. The reliability and applicability of "Kastner extension formula" were proved that it can be used to calculate the deformation pressure for the weak rock tunnels with high geostress.Some new understanding and rules of the surrounding rock pressure and interaction mechanism between surrounding rock and supporting structure in the weak rock tunnels with high geostress were obtained in this paper. These results would become important theory basis for the design and construction of the weak rock tunnels with high geostress. These fruits can also be hoped to play a promotion role for the research of this area.更多还原