基于统一强度理论有限填土土压力计算及挡墙优化设计

发布时间：2018-01-26 01:25

本文关键词： 重力式挡土墙主动土压力统一强度理论有限填土遗传算法优化设计　出处：《湖南大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着城市的不断发展,土地资源愈发紧张,经常发生拟建建筑基坑挡墙与既有建筑地下室外墙相隔很近的情况。对于山区挡土墙,常因靠近岩石边坡,从而形成有限填土空间。若运用库伦和朗金理论来计算土压力,则需要墙后填土有足够的宽度,以使滑裂面充分发展。因此,有限填土情况下的挡土墙土压力计算和挡土墙截面优化设计均亟待解决,且具有广阔的前景。本文对挡土墙后有限填土土压力以及挡土墙截面优化设计进行了较为深入的探讨,主要内容如下:首先,假定挡土墙后填土滑动面为通过墙踵的多楔体平面,基于极限平衡理论,推导得到了墙后填土区狭窄,墙面倾斜、粗糙,填土面向上倾斜,并考虑地面超载和地震影响的无黏性土主动土压力解。随着墙后填土宽度的改变,破坏模式实现从单楔体到双楔体甚至三楔体的转换,使得计算更加灵活。计算结果表明:随着填土宽度的减小,土压力随之减少,且恒小于库伦值。而当墙面倾角较大时,该方法与库伦法差别较小。这是由于随着墙面倾角的增加,填土顶面的宽度也随之增加,使得其破坏模式倾向于与库伦法相近的情况。然后,假定挡土墙后填土滑动面为通过墙踵的平面双滑块模式,基于MorhCoulomb强度理论和极限分析原理,推导出适用于无黏性土的主动土压力解。结果表明:本方法得到的土压力呈非线性分布,且土压力强度随深度增大而增大,在靠近墙底处其增幅逐渐减小。其次,假定挡土墙后填土滑动面为通过墙踵的对数螺旋面和平面组合模式,基于统一强度理论和极限分析原理,推导出适用于黏性土的主动土压力解。当材料切应力系数B=2,统一强度理论回归为Morh-Coulomb强度理论。结果表明:该方法所得土压力系数大于本文以极限平衡理论为基础提出的方法所得的解。这是由于基于极限分析方法所得解为土压力的上限解,且土压力合力作用点一直在变化,不总在距离墙踵1/3墙高处。最后,以挡土墙截面面积为目标函数,以截面几何参数为设计标量,将抗滑抗倾覆稳定性、基底应力和结构构造要求作为约束条件,建立了有限填土重力式挡土墙优化模型,提出了基于遗传算法有限填土重力式挡土墙智能优化计算方法,并基于MATLAB编制了优化计算程序。将本方法应用于贵州某电厂挡墙设计,分析发现:在满足抗滑和抗倾覆的条件下,优化后节约面积38%,符合经济效益。
[Abstract]:With the continuous development of the city, the land resources become more and more tight. It often happens that the retaining wall of foundation pit of the proposed building is very close to the exterior wall of the basement of the existing building. For the retaining wall of the mountain area, it is often due to being close to the rock slope. If Coulomb and Rankine theory are used to calculate the earth pressure, it is necessary to have enough width of the backfill to make the slip surface develop fully. The calculation of the earth pressure of the retaining wall and the optimum design of the section of the retaining wall under the condition of limited fill are urgent to be solved. In this paper, the finite fill pressure behind the retaining wall and the optimization design of the retaining wall section are discussed in depth. The main contents are as follows: first. Assuming that the sliding surface of the backfill of retaining wall is a multi-wedge plane passing through the heel of the wall, based on the limit equilibrium theory, the narrow backfill area, the slope of the wall surface, the roughness of the backfill surface and the upward inclination of the fill are derived. The active earth pressure solution of non-clay soil affected by ground overload and earthquake is taken into account. With the change of backfill width, the failure mode can be transformed from single wedge to double wedge or even three-wedge. The calculation results show that the earth pressure decreases with the decrease of the fill width and is always less than the Coulomb value. The difference between the method and the Coulomb method is small. This is because the width of the top surface increases with the increase of the inclination of the wall, which makes the failure mode tend to be similar to that of the Coulomb method. Then. It is assumed that the sliding surface of the backfill of retaining wall is a plane double-slide model passing through the heel of the wall, based on the MorhCoulomb strength theory and the limit analysis principle. The results show that the soil pressure obtained by this method is nonlinear, and the soil pressure intensity increases with the increase of depth. The increment decreases gradually near the bottom of the wall. Secondly, it is assumed that the sliding surface behind the retaining wall is a logarithmic spiral plane and a plane combination model passing through the heel of the wall, based on the unified strength theory and the limit analysis principle. The active earth pressure solution suitable for clay is derived. The unified strength theory is regressed to the Morh-Coulomb strength theory. The results show that:. The soil pressure coefficient obtained by this method is larger than that obtained by the method based on the limit equilibrium theory, which is due to the fact that the solution based on the limit analysis method is the upper limit solution of the earth pressure. And the earth pressure acting point has been changing, not always at the height of 1/3 wall from the heel of the wall. Finally, taking the cross-section area of retaining wall as the objective function and the geometric parameters of the section as the design scalar, the stability of anti-slide and anti-capsizing will be achieved. The optimization model of gravity retaining wall with finite fill is established and the intelligent optimization method of gravity retaining wall with limited fill based on genetic algorithm is proposed. This method is applied to the design of retaining wall of a power plant in Guizhou province. It is found that under the conditions of anti-skid and anti-overturning, the optimized area is saved by 38%. Accord with economic benefit.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU476.4;TU432

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