软岩大变形隧道随机力学特征研究
发布时间：2018-08-13 19:09
【摘要】：由于隧道工程特有的工程性质,导致隧道结构的受力、变形和破坏往往形式复杂、变化多样,且影响因素众多。而这些影响因素来自于荷载、材料、结构几何形状等诸多方面,且大多都为随机变化量,包含众多的不确定性。随着工程技术、理论研究的发展,基于确定性研究所得的理论成果表现出一定的不合理性。专家学者对这些影响隧道结构的随机变量开展了大量的基础研究工作,形成以可靠度理论为基础的概率极限设计方法。随着我国隧道工程建设的大力发展,危害程度大、治理费用高、施工风险大的软弱围岩大变形灾害已成为困扰地下工程界的一个重大问题,而软岩大变形隧道稳定性的研究是工程科研人员亟需深入研究解决的一大课题。本文介绍了结构可靠度以及软弱围岩大变形理论的国内外研究现状与发展,在相关文献及研究成果的基础上对结构可靠度及软岩大变形理论进行整理总结。再以兰渝线天池坪隧道为工程背景,利用有限元软件ANSYS采用DP屈服准则对天池坪隧道进行二维数值模拟,对隧道台阶法连续开挖施工过程进行模拟,在考虑围岩、支护结构材料等影响隧道结构随机特性的参数外,尝试将时间随机场转化为围岩扰动影响系数,构造包含时间随机场的极限位移功能函数及极限状态方程,利用蒙特卡洛法对隧道开挖过程中隧道结构的可靠度进行计算,研究各台阶开挖过程中隧道结构的随机特性。在各台阶开挖过程中,围岩弹性模量对隧道拱顶沉降的影响最大,随着围岩弹性模量的增大隧道拱顶沉降量(负数)增大;支护结构厚度和支护结构弹性模量对拱顶沉降的影响次之,影响规律均为随着支护厚度和支护弹模的增大隧道拱顶沉降量(负数)增大;围岩密度的随机特性对拱顶沉降的影响较小,随着围岩密度的增大隧道拱顶沉降量(负数)减小;以上规律在隧道开挖过程中均保持不变;但隧道开挖完成后,支护结构厚度、支护结构弹性模量对拱顶沉降的影响反而小于围岩密度对拱顶沉降影响,这与隧道开挖过程中的规律相反,即说明支护结构在隧道开挖过程中对隧道稳定性的影响要大于对隧道开挖完成后的影响,也就验证了支护结构随机特性在隧道开挖过程中对隧道的稳定作用较大。所以在软岩大变形隧道的开挖过程中初期支护结构的施做对隧道结构及围岩的稳定性意义重大;但不论在隧道开挖过程中还是隧道开挖完成后,围岩弹性模量对隧道拱顶沉降的影响均为最大,所以围岩的不确定性仍是隧道开挖过程中影响隧道结构可靠的主要原因。
[Abstract]:Due to the special engineering properties of tunnel engineering, the stress, deformation and failure of tunnel structure are often complicated, varied and have many influencing factors. These factors come from loads, materials, structural geometry and many other aspects, and most of them are random variables, including a lot of uncertainties. With the development of engineering technology and theoretical research, the theoretical results based on deterministic research show some irrationality. Experts and scholars have carried out a lot of basic research on these random variables which affect the tunnel structure and formed a probability limit design method based on reliability theory. With the great development of tunnel engineering construction in China, the disaster of large deformation of soft surrounding rock, which is of great harm degree, high treatment cost and high construction risk, has become a major problem puzzling the underground engineering circle. The research on the stability of soft rock tunnel with large deformation is an urgent task for engineering researchers. This paper introduces the present situation and development of the theory of structural reliability and large deformation of soft rock at home and abroad, and summarizes the theory of structural reliability and large deformation of soft rock on the basis of relevant literature and research results. Then taking Tianchiping tunnel of Lanyu line as the engineering background, using the finite element software ANSYS to carry on the two-dimensional numerical simulation of Tianchiping tunnel by using DP yield criterion, and to simulate the construction process of the continuous excavation of the tunnel by step method, considering the surrounding rock. Besides the parameters which affect the random characteristics of tunnel structure, the time random field is transformed into the disturbance coefficient of surrounding rock, and the function of limit displacement and the limit state equation including time random field are constructed. The reliability of tunnel structure during tunnel excavation is calculated by Monte Carlo method, and the stochastic characteristics of tunnel structure during step excavation are studied. In the process of every step excavation, the elastic modulus of surrounding rock has the greatest influence on the settlement of the tunnel arch roof, and with the increase of the elastic modulus of the surrounding rock, the settlement amount of the tunnel arch roof (negative number) increases. The thickness of supporting structure and elastic modulus of supporting structure have the second influence on the settlement of arch roof, the law of influence is that with the increase of supporting thickness and elastic modulus of support, the settlement (negative number) of tunnel arch roof increases. The random characteristics of surrounding rock density have little influence on the settlement of arch roof. With the increase of surrounding rock density, the settlement (negative number) of tunnel arch roof decreases, and the above laws remain unchanged in the course of tunnel excavation, but the thickness of supporting structure after tunnel excavation is completed. The influence of elastic modulus of supporting structure on the settlement of arch roof is smaller than that of surrounding rock density on the settlement of arch roof, which is contrary to the law in the course of tunnel excavation. That is to say, the influence of supporting structure on tunnel stability in the course of tunnel excavation is greater than that on tunnel stability after tunnel excavation, and it is verified that the stochastic characteristics of supporting structure play a greater role in the stability of tunnel in the course of tunnel excavation. Therefore, it is of great significance for the stability of tunnel structure and surrounding rock to make the initial supporting structure in the excavation process of large deformation tunnel in soft rock, but no matter in the course of tunnel excavation or after the tunnel excavation is completed, the construction of supporting structure is of great significance to the stability of tunnel structure and surrounding rock. The influence of elastic modulus of surrounding rock on the settlement of tunnel arch is the biggest, so the uncertainty of surrounding rock is still the main reason that affects the reliability of tunnel structure in the course of tunnel excavation.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U451
本文编号：2181911
[Abstract]:Due to the special engineering properties of tunnel engineering, the stress, deformation and failure of tunnel structure are often complicated, varied and have many influencing factors. These factors come from loads, materials, structural geometry and many other aspects, and most of them are random variables, including a lot of uncertainties. With the development of engineering technology and theoretical research, the theoretical results based on deterministic research show some irrationality. Experts and scholars have carried out a lot of basic research on these random variables which affect the tunnel structure and formed a probability limit design method based on reliability theory. With the great development of tunnel engineering construction in China, the disaster of large deformation of soft surrounding rock, which is of great harm degree, high treatment cost and high construction risk, has become a major problem puzzling the underground engineering circle. The research on the stability of soft rock tunnel with large deformation is an urgent task for engineering researchers. This paper introduces the present situation and development of the theory of structural reliability and large deformation of soft rock at home and abroad, and summarizes the theory of structural reliability and large deformation of soft rock on the basis of relevant literature and research results. Then taking Tianchiping tunnel of Lanyu line as the engineering background, using the finite element software ANSYS to carry on the two-dimensional numerical simulation of Tianchiping tunnel by using DP yield criterion, and to simulate the construction process of the continuous excavation of the tunnel by step method, considering the surrounding rock. Besides the parameters which affect the random characteristics of tunnel structure, the time random field is transformed into the disturbance coefficient of surrounding rock, and the function of limit displacement and the limit state equation including time random field are constructed. The reliability of tunnel structure during tunnel excavation is calculated by Monte Carlo method, and the stochastic characteristics of tunnel structure during step excavation are studied. In the process of every step excavation, the elastic modulus of surrounding rock has the greatest influence on the settlement of the tunnel arch roof, and with the increase of the elastic modulus of the surrounding rock, the settlement amount of the tunnel arch roof (negative number) increases. The thickness of supporting structure and elastic modulus of supporting structure have the second influence on the settlement of arch roof, the law of influence is that with the increase of supporting thickness and elastic modulus of support, the settlement (negative number) of tunnel arch roof increases. The random characteristics of surrounding rock density have little influence on the settlement of arch roof. With the increase of surrounding rock density, the settlement (negative number) of tunnel arch roof decreases, and the above laws remain unchanged in the course of tunnel excavation, but the thickness of supporting structure after tunnel excavation is completed. The influence of elastic modulus of supporting structure on the settlement of arch roof is smaller than that of surrounding rock density on the settlement of arch roof, which is contrary to the law in the course of tunnel excavation. That is to say, the influence of supporting structure on tunnel stability in the course of tunnel excavation is greater than that on tunnel stability after tunnel excavation, and it is verified that the stochastic characteristics of supporting structure play a greater role in the stability of tunnel in the course of tunnel excavation. Therefore, it is of great significance for the stability of tunnel structure and surrounding rock to make the initial supporting structure in the excavation process of large deformation tunnel in soft rock, but no matter in the course of tunnel excavation or after the tunnel excavation is completed, the construction of supporting structure is of great significance to the stability of tunnel structure and surrounding rock. The influence of elastic modulus of surrounding rock on the settlement of tunnel arch is the biggest, so the uncertainty of surrounding rock is still the main reason that affects the reliability of tunnel structure in the course of tunnel excavation.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U451
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