斜坡地基极限承载力研究

发布时间：2018-04-27 07:25

本文选题：斜坡地基 + 地基极限承载力　；参考：《长安大学》2015年博士论文

【摘要】：论文通过离心模型试验、理论计算和数值分析,研究了斜坡地基的变形规律和破坏特征,分析了地基土参数、坡面条件、荷载条件以及摩擦条件等对斜坡地基的极限坡面曲线和坡顶极限荷载的影响,并从斜坡地基中塑性区开展范围的角度分析其内在原因。主要研究成果如下:1、斜坡地基破坏形式呈非对称性,较之平地地基,斜坡地基上的基础更易发生倾斜,从而导致应力向倾斜的一侧集中,临坡一侧的地基因应力集中而先达到极限平衡状态,破裂面相交于坡面中下部。基础的位置对斜坡地基的变形规律和破坏形式有显著影响,当坡顶距大于4倍基础宽度时,其变形破坏规律接近平地地基的情况;基础的摩擦条件会影响到地基承载力的大小以及破裂面开展的形式。2、利用坡顶荷载条件,编写斜坡地基滑移线方程的差分计算程序,可求出斜坡地基中塑性区各点的x、y、?和?值,并最终确定其极限坡面曲线。计算结果表明,极限坡面曲线的斜率随着y的增加而变小。基底摩擦的存在,造成主动区开角?AOB降低,塑性区向土体内部移动,极限坡面曲线明显降低。坡顶荷载的增大,引起极限坡面坡率变缓,坡脚向外延伸。土体重度的增加引起极限坡面曲线向外移动、坡脚向下发展。土体强度参数的增大引起过渡区开角?BOC的降低,坡面曲线降低、坡率增大;黏聚力的增大还会引起过渡区、被动区范围的缩小。3、建立了考虑基底摩擦条件的斜坡地基极限承载力计算方法,研究了基底摩擦系数对斜坡地基极限承载力的影响。基底摩擦条件影响到斜坡地基内部的塑性区分布,摩擦系数tan?越大,土体中的过渡区面积增大,主动区范围缩小;坡顶极限荷载增长率随着tan?的增加而增加。4、坡顶极限荷载值及其增长率随着坡率的增加而增加。土体重度的增加引起土体中塑性区的范围增大,从而引起坡顶极限荷载的增大。但坡顶O点的极限荷载没有变化。黏聚力的增加使得土体中的塑性区范围向土体内部延伸,引起坡顶荷载的增加,对坡顶极限荷载的增长率影响不大。内摩擦角的增加使得土体中的塑性区呈缩小趋势,但是对坡顶荷载的增长率影响较大。5、基于统一强度强度理论,建立了考虑中主应力的斜坡地基统一滑移线方程,研究了中主应力对斜坡地基承载力的影响。计算表明,由于中主应力的存在,斜坡地基中塑性区的范围减小,随着b值的增加,斜坡地基的极限坡面曲线斜率增大,坡顶极限荷载增长。在坡顶O点,b=0.4和b=1时,极限承载力比不计中主应力时提高了25.58%和61.18%。
[Abstract]:Through centrifugal model test, theoretical calculation and numerical analysis, the deformation law and failure characteristics of slope foundation are studied, and the soil parameters and slope conditions are analyzed. The influence of load condition and friction condition on the limit slope curve and the limit load of slope top are analyzed from the angle of the development range of plastic zone in slope foundation. The main research results are as follows: 1. The failure form of the slope foundation is asymmetrical, and the foundation on the slope foundation is more inclined than the flat foundation, which leads to the stress concentration on the inclined side. The stress concentration on the side of the slope leads to the ultimate equilibrium state, and the fracture surface intersects in the middle and lower part of the slope. The position of foundation has a significant influence on the deformation law and failure form of slope foundation. When the slope top distance is more than 4 times the width of foundation, the deformation and failure law of slope foundation is close to that of flat foundation. The friction condition of the foundation will affect the bearing capacity of the foundation and the form of the fracture surface. By using the load condition of the slope top, the difference calculation program of slip line equation of the slope foundation can be compiled, and the XY of each point in the plastic zone of the slope foundation can be obtained. And? Value and finally determine its ultimate slope curve. The results show that the slope of the limit slope curve decreases with the increase of y. The existence of base friction results in the decrease of AOB in the active zone, the movement of the plastic zone to the soil, and the decrease of the limit slope curve. With the increase of the load on the top, the slope rate of the limit slope becomes slower and the foot of the slope extends outwards. The increase of soil weight causes the limit slope curve to move outward and the slope foot to develop downwards. The increase of soil strength parameter leads to the decrease of BOC, the decrease of slope curve and the increase of slope ratio, and the increase of cohesion will cause the transition zone. In this paper, the calculation method of ultimate bearing capacity of slope foundation considering the condition of base friction is established, and the influence of the coefficient of foundation friction on ultimate bearing capacity of slope foundation is studied. The friction condition of the base affects the distribution of the plastic zone in the slope foundation, and the friction coefficient tann? The larger the soil is, the larger the area of transition zone is and the smaller the active zone is. The limit load value and its growth rate increase with the increase of slope ratio. The increase of soil weight increases the range of the plastic zone in the soil, which leads to the increase of the limit load on the top of the slope. However, the limit load at O point at the top of the slope does not change. The increase of cohesion makes the range of plastic zone in soil extend to the inside of soil, which causes the increase of slope top load, and has little effect on the growth rate of limit load on slope top. With the increase of internal friction angle, the plastic zone in soil tends to shrink, but it has a great influence on the growth rate of slope top load. Based on the unified strength strength theory, the unified slip line equation of slope foundation considering medium principal stress is established. The effect of medium principal stress on the bearing capacity of slope foundation is studied. The calculation shows that due to the existence of middle principal stress, the range of plastic zone in the slope foundation decreases. With the increase of b value, the slope of the limit slope curve of the slope foundation increases and the limit load of the slope top increases. The ultimate bearing capacity of the slope is increased by 25.58% and 61.18% than that at O point (0.4 and b = 1).
【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU470

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