基于上限分析的建筑含洞地基承载力分析

发布时间：2018-11-08 13:28

【摘要】：城市地铁等地下空间的开发建设,在地下岩土体中挖出了大量洞室,这就造成许多建筑物都必须在含洞的地基上开工建设。不含洞的地基与含洞的地基特别是浅埋含洞地基,有着明显的承载能力和稳定性差异。在地基基础的设计施工过程中,最重要的就是要先确定地基的承载力设计值,只有确定了地基的承载力设计值,才可以为之后建筑的设计施工提供依据。传统的地基承载力理论计算方法,如极限平衡法和滑移线法,在求解含洞地基承载力的问题上有诸多困难,而极限分析上限法是解决此问题的有效途径。本文采用刚性滑块极限分析上限法和有限差分数值模拟方法,对洞顶中心条形基础荷载作用下的建筑含洞岩基的承载力进行了研究。主要工作如下:(1)首先阐述极限分析上限法的基本原理,探讨极限分析上限法的特性和适用性问题。总结分析均质地基的破坏模式,及多孔岩基的破坏模式,得出浅埋含洞岩基的破坏模式为冲压破坏。依据实际的地基破坏实例,理论研究结果和数值模拟成果,简化出建筑含洞地基的破坏模式,划分刚性滑块、设定虚位移向量,最终构建出含圆形隧道的含洞地基破坏模式。(2)依据构建出来的含洞地基破坏模式,推导各刚性滑块的虚位移向量、位移分量、刚性滑块面积。依据极限分析上限法原理,建立外力虚功和内部耗散功的平衡方程,求解不同条件下建筑含洞地基的承载力上限解。(3)依据上限法计算得到的不同含洞地基极限承载力计算公式,探讨了不同的基础宽度、洞室埋深、洞室大小对建筑含洞地基极限承载力的影响,并与有限差分数值模拟结果进行了对比。(4)采用有限差分数值模拟方法,对比圆形洞室开挖前后地基的各方向应力场和塑性区分布差异;分析圆形洞室开挖后地基的应力情况和塑性区分布情况。模拟分析在不同洞室埋深、不同荷载作用位置下,含洞地基的应力场、位移场和塑性区分布情况。
[Abstract]:With the development and construction of underground space such as urban subway, a large number of caverns have been dug out in the underground rock and soil mass, which makes it necessary for many buildings to be constructed on the foundation with holes. There are obvious differences in bearing capacity and stability between the foundation without hole and the foundation with hole, especially the foundation with shallow hole. In the process of foundation design and construction, the most important thing is to determine the design value of bearing capacity of foundation first. Only when the design value of bearing capacity of foundation is determined, can we provide the basis for the design and construction of later building. The traditional theoretical calculation methods of foundation bearing capacity, such as limit equilibrium method and slip line method, have many difficulties in solving the bearing capacity of foundation with holes, and the upper limit method of limit analysis is an effective way to solve this problem. In this paper, the upper limit analysis method of rigid slider and the finite difference numerical simulation method are used to study the bearing capacity of the rock foundation with holes under the load of the central strip foundation at the top of the tunnel. The main work is as follows: (1) the basic principle of the upper limit method of limit analysis is expounded, and the characteristics and applicability of the upper limit method of limit analysis are discussed. The failure modes of homogeneous foundation and porous rock foundation are summarized and analyzed. It is concluded that the failure mode of shallow buried cavernous rock foundation is punching failure. According to the actual foundation failure example, theoretical research results and numerical simulation results, the failure mode of the foundation with holes is simplified, the rigid slide block is divided, and the virtual displacement vector is set up. Finally, the failure mode of the tunnel with holes is constructed. (2) the virtual displacement vector, displacement component and area of rigid slider are deduced according to the failure mode. According to the principle of upper limit method of limit analysis, the equilibrium equations of external virtual work and internal dissipative work are established. The upper limit solution of the bearing capacity of the foundation with holes is solved under different conditions. (3) according to the calculation formula of the ultimate bearing capacity of the foundation with different holes obtained by the upper limit method, the different foundation width and the depth of the cavern are discussed. The influence of the size of the cavity on the ultimate bearing capacity of the foundation with holes is compared with the results of the finite difference numerical simulation. (4) the finite difference numerical simulation method is used. The stress field and plastic zone distribution of the foundation before and after the excavation of circular cavern are compared. The stress and plastic zone distribution of the foundation after excavation of circular cavern are analyzed. The stress field, displacement field and plastic zone distribution of the foundation with holes are simulated and analyzed under different cavity depth and different load position.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU43

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