十字交叉条形荷载作用下地基承载力数值分析

发布时间：2018-08-12 21:02

【摘要】：实际工程中,浅基础形式中应用比较广泛的是条形基础。对于条形基础作用下的地基承载力,可以比较方便地把其当作平面应变问题来解决。本文主要研究十字交叉条形荷载作用下的地基承载力。由于十字交叉条形荷载作用下的地基承载力是一个三维问题,平面应变分析已不能反映其破坏特性。目前对于十字交叉条形基础的研究相对较少,导致在承载力设计上偏于保守,造成了材料和承载力的浪费,所以有必要对其承载力规律做一定研究,以便更好的指导实际工程。对于十字交叉条形基础表面的荷载分布,本文假定用均布荷载代替作用在基础交叉点处的集中荷载。本文运用FLAC3D对不同形式荷载作用下地基的承载力、地基应力分布规律、地基的破坏模式和变形机理等进行了全面的研究,可得到以下主要结论:(1)“口”字形荷载、“田”字形荷载和“九宫格”形荷载作用下的地基承载力均随着内摩擦角的增大呈现递增的趋势。当内摩擦角不变时,“口”字形荷载、“田”字形荷载和“九宫格”形荷载作用下的地基承载力呈现增大的趋势。对于“口”字形荷载,地基破坏时,地基隆起量在荷载内外侧基本相等;对于“田”字形荷载和“九宫格”形荷载,地基发生破坏时,地基隆起量荷载外侧大于内侧。(2)对于“口”字形荷载,长宽比对承载力有一定影响。在一定长宽比范围内,地基承载力随着长宽比的增加呈现先增大后减小的趋势。通过数值模拟,不同长宽比下,地基承载力最多提高了11.4%。(3)“口”字形荷载长宽比为1时,在一定范围内,地基承载力随着荷载边长的减小呈现递增的趋势。通过数值模拟,长宽比为1时,地基承载力最多提高了15.7%。(4)在不同的长宽比作用下,剪应变率云图在长边下方开展深度大于短边下方开展深度,长宽比越大,其开展深度相差越大。由于“口”字形荷载间的相互影响,荷载外侧剪应变率包络线全部延伸至地基表面,在荷载内侧剪应变率包络线未全部延伸至地基表面。此时地基破坏模式类似于整体剪切破坏,只是破坏曲线不再关于荷载中心对称。“口”字形荷载长宽比为1,边长小于2m时,地基承载力受边长影响较大;边长大于3m时,地基承载力受边长影响较小。
[Abstract]:In practical engineering, strip foundation is widely used in shallow foundation form. The bearing capacity of the foundation under the action of strip foundation can be easily solved as a plane strain problem. This paper mainly studies the bearing capacity of foundation under cross-cross strip load. Because the bearing capacity of foundation under cross strip load is a three dimensional problem, the plane strain analysis can no longer reflect its failure characteristics. At present, the research of cross strip foundation is relatively few, which leads to conservative design of bearing capacity and waste of materials and bearing capacity. So it is necessary to do some research on the bearing capacity of cross strip foundation in order to better guide the practical engineering. For the load distribution on the cross strip foundation surface, it is assumed that uniform load is used instead of the concentrated load acting at the intersection of the foundation. In this paper, FLAC3D is used to study the bearing capacity, stress distribution, failure mode and deformation mechanism of foundation under different forms of load. The main conclusions are as follows: (1) "mouth" zigzag load, The bearing capacity of foundation under the action of "Tian" zigzag load and "Jiugong lattice" load is increasing with the increase of internal friction angle. When the angle of internal friction is constant, the bearing capacity of foundation under the action of "mouth", "Tian" and "Jiugong" is increasing. For the "mouth" zigzag load, when the foundation is damaged, the uplift of the foundation is basically equal to the inside and outside of the load; for the "Tian" zigzag load and the "Jiugong lattice" load, the foundation is destroyed, The lateral load of foundation uplift is larger than that of inner side. (2) for "mouth" zigzag load, the ratio of length to width has a certain influence on the bearing capacity. In a certain range of aspect ratio, the bearing capacity of foundation increases first and then decreases with the increase of aspect ratio. Through numerical simulation, the bearing capacity of foundation is increased by 11.44.The maximum value of bearing capacity is increased by 11.4under different aspect ratio. (3) when the ratio of length to width of the zigzag load is 1, the bearing capacity of the foundation increases with the decrease of load side length in a certain range. Through numerical simulation, when the aspect ratio is 1, the bearing capacity of the foundation increases by 15.7. (4) under the action of different aspect ratio, the depth of shear strain rate cloud map is greater than that of the bottom of the short edge, and the ratio of length to width increases. The greater the depth of its development. Due to the interaction between the "mouth" and zigzag loads, the lateral shear strain rate envelope of the load extends to the surface of the foundation, while the envelope of the shear strain rate on the inner side of the load does not extend to the surface of the foundation. The failure mode of the foundation is similar to that of the whole shear failure, except that the failure curve is no longer symmetrical to the center of the load. When the ratio of length to width is 1 and the side length is less than 2m, the bearing capacity of the foundation is greatly affected by the side length, and the bearing capacity of the foundation is less affected by the side length when the side length is more than 3m.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU470

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