基于有限元计算的悬臂式挡土墙主动土压力研究

发布时间：2018-04-23 21:38

本文选题：悬臂式挡土墙 + 极限状态　；参考：《太原理工大学》2017年硕士论文

【摘要】：悬臂式挡土墙是挡土墙的一种,其结构简单,自重较轻,施工方便,且便于工厂化生产,经济性较好,被广泛用于河道治理、道路建设、园林改造等众多工程中,是近年来国内常见的轻型挡土建筑物。合理地确定土压力是悬臂式挡土墙设计的关键内容,通常是将墙踵与墙顶的连线或者将过墙踵的垂直面作为假想墙背,再根据朗肯理论或库伦理论计算作用在假想墙背上的土压力。该方法忽略了悬臂式挡土墙墙后填土中产生的破裂面,因此导致其与实际情况相差较大。本文运用ANSYS有限元分析软件建立悬臂式挡土墙、墙后土体及地基的弹塑性有限元模型,采用分段位移约束和接触分析,通过寻找主动极限状态下第一、二破裂面的位置,研究悬臂式挡土墙在极限状态下主动土压力的分布规律及影响因素。主要结论如下:(1)悬臂式挡土墙达到主动极限状态,填土中产生第一破裂面和第二破裂面。第一、二破裂面由墙踵附近出现,分别向远离墙体和靠近墙立板的方向,经填土内部穿过,呈“V”型贯通。第二破裂面是悬臂式挡土墙固有的特征,并使墙踵板上方的部分填土因墙板保护而免受剪切破坏,在悬臂式挡土墙位移时随墙体一起移动。根据悬臂式挡土墙几何尺寸的不同,第二破裂面分为不与墙立板相交的直线形第二破裂面和与墙立板相交的折线形第二破裂面两种。出现折线形第二破裂面且填土内摩擦角和粘聚力较小时,填土中出现平行于第一破裂面且与第二破裂面相交的第三破裂面。(2)填土内摩擦角和粘聚力是土体的抗剪强度指标,内摩擦角、粘聚力越大,土体抗剪切破坏能力越强,达到主动极限状态所需的墙体位移量也越大。墙体位移一定时,土体发生塑性变形区域随内摩擦角和粘聚力的增大而减小。填土表面倾角对第二破裂面影响较小,对第一破裂面影响明显。填土表面倾角越大,达到极限状态所需的墙体位移量越大,第一破裂面塑性贯通区域越大,即参与破坏的土体量越多。(3)出现折线形第二破裂面,破裂面与墙体间的土体受到“保护”不发生剪切破坏。当墙体移动时,这些土体会与墙体一起移动,可视为墙体的一部分,故作用于折线形第二破裂面上的应力即为悬臂式挡土墙土压力,作用于第二破裂面上的水平土压力随填土内摩擦角、粘聚力、弹性模量的增大而减小。靠近墙踵处,地基摩擦力影响明显,水平土压力有逐渐减小的趋势。折线形破裂面上的垂直土压力随破裂面上方土体体积的增大而增大,填土内摩擦角、粘聚力、弹性模量对其影响较小;出现直线形第二破裂面(第二破裂面在墙踵和墙顶连线的外侧)时,第二破裂面与墙体之间的土体并不是全部随着墙体运动,因此不能简单以直线形第二破裂面上的力近似为挡土墙水平土压力。(4)无论填土中产生折线形还是直线形第二破裂面,随着内摩擦角、粘聚力、弹性模量的逐渐增大,水平合力逐渐减小,而合力作用点高度有增大的趋势。填土中出现直线形破裂面且内摩擦角不同,合力作用点小于折线形第二破裂面的情况。(5)由实际算例表明,有限元法对一般规模的悬臂式挡土墙结构,在常用计算机上试算一次所需时间为6~15min,因此,采用有限元法模拟工程中的悬臂式挡土墙以验算其土压力及稳定性有良好的应用前景,在设计人员中推广有限元原理、方法及软件的应用,用有限元软件建模进而验算其土压力及稳定性有重要意义。
[Abstract]:Cantilever retaining wall is a kind of retaining wall. It is simple in structure, light in weight, convenient in construction, easy to be produced in the factory and good in economy. It is widely used in many projects such as river management, road construction and garden reconstruction. It is a common lightweight retaining wall in China in recent years. It is reasonable to determine the earth pressure as a cantilever retaining wall. The key content is to connect the heel to the top of the wall or the vertical surface of the heel as the back of the imaginary wall, and then calculate the earth pressure on the back of the imaginary wall according to the Rankine theory or the Kulun theory. This method ignores the fracture surface in the backfill of the cantilever retaining wall, so it is quite different from the actual situation. The finite element analysis software ANSYS is used to set up the cantilever retaining wall and the elastoplastic finite element model of the soil and the foundation after the wall. By subsection displacement constraint and contact analysis, the distribution law of the active earth pressure and the influencing factors of the cantilever retaining wall under the limit state are studied by finding the position of the first, second fracture surface under the active limit state. The conclusions are as follows: (1) the cantilever retaining wall reaches the active limit state, the first fracture surface and the second fracture surface are produced in the fill. First, second the rupture surface appears near the wall heel, respectively, to the direction of the wall and the wall near the wall, passing through the fill, and the "V" type through. Second fracture surface is the inherent characteristic of the cantilever retaining wall, and makes the fracture surface a characteristic of the cantilever retaining wall. The partial fill above the wall heel is protected by the wall plate from shear failure and moves along with the wall when the cantilever retaining wall is displaced. According to the different geometric dimensions of the cantilever retaining wall, the second fracture surface is divided into two kinds of fracture surfaces that are not intersected with the wall of the wall and two of the broken line second fracture surfaces intersecting with the wall stand plate. The linear second fracture surface and the inner friction angle and cohesion of the fill are small, and the third fracture surface which is parallel to the first fracture surface and intersected with the second fracture surface. (2) the friction angle and cohesion of the fill are the shear strength index of the soil, the greater the internal friction angle, the greater the cohesive force, the stronger the shear failure ability of the soil, to the active limit shape. When the wall displacement is certain, the plastic deformation area of the soil decreases with the increase of internal friction angle and cohesive force. The inclination of the fill surface has little influence on the second fracture surface, and it has obvious influence on the first fracture surface. The greater the surface angle of the fill surface is, the greater the displacement of the wall is needed to reach the limit state, the first break. The larger the fractured surface plastic penetration area is, the more soil mass is involved. (3) there is a broken line second fracture surface, and the soil between the wall and the wall is protected from shear failure. When the wall moves, the soil will move with the wall, which can be seen as a part of the wall, so it should be used on the fractured surface of the second fracture surface. The force is the earth pressure of the cantilever retaining wall. The horizontal earth pressure on the second fracture surface decreases with the increase of the friction angle, cohesion and modulus of elasticity in the fill. The friction force of the foundation is obviously influenced by the wall near the wall, and the horizontal earth pressure gradually decreases. The vertical earth pressure above the fracture surface is with the volume of soil above the fracture surface. The friction angle, cohesive force and elastic modulus of the fill are less affected by the increase, and the soil between the second fracture surface and the wall is not all along with the wall when the linear second fracture surface (second fracture surface is on the side of the wall and the top of the wall) is not as simple as the force on the straight line second fracture surface. Horizontal earth pressure of retaining wall. (4) no matter the folding or linear second fracture surface in the fill, with the internal friction angle, cohesive force and modulus of elasticity gradually increasing, the horizontal resultant force gradually decreases, and the point of the resultant force is increased. There is a straight fracture surface in the fill and the internal friction angle is different, and the point of action is less than the fold line. Second the case of fracture surface. (5) the actual calculation shows that the time required for the finite element method to test the cantilever retaining wall structure of the general scale is 6~15min. Therefore, the finite element method is used to simulate the cantilever retaining wall in the project to check the earth pressure and stability. It is of great significance to popularize the principles, methods and software applications of finite element method, and use finite element software modeling to check its earth pressure and stability.

【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU476.4

【参考文献】