土拱效应敏感度实验及数值模拟研究

发布时间：2018-08-15 15:41

【摘要】：土拱效应是通过调整土体内部的应力分布把土压力传递到桩上的现象,其实质是土体充分调动自身抗剪性能以抵抗土压力的现象。1943年Terzaghi通过著名的"活动门"试验验证了土拱效应的存在,之后国内外学者通过理论分析及各种模型试验,并借助数值计算软件对土拱效应的发生机理、存在模式、影响因素等进行了深入的研究。有关土拱效应的实测数据越来越多、理论研究逐渐深入,工程中开始考虑土拱效应,实际应用中取得很好的经济效益。目前,有关土拱效应的理论研究还不够系统,数值计算中值得探讨的问题较多,尤其时土拱模式和合理桩宽比的确定,这直接影响了土拱效应在工程中能否进一步应用。因此有必要从基础研究方面继续开展工作。本文主要依据竖向活动门试验和水平活动门试验,并借助数学仿真计算软件深入分析活动门宽度、粘聚力、内摩擦角等因素对土拱效应的影响,初步建立了土拱效应模型并提出了合理桩宽比,这对于指导工程设计具有较大的理论意义。本文的主要结论如下:(1)通过竖向活动门实验,研究了不同土体和不同活动门宽度下土拱的发生机理和存在条件,以及对桩荷载分担比的影响。重点分析了砂土拱轴线形状与活动门宽度和内摩擦角的关系。初步建立了桩荷载分担比和活动门宽度、内摩擦角的关系。(2)竖向土拱效时合理桩宽比的确定。不同填土高度、土体粘聚力、土体内摩擦角等因素下,随着桩宽比的增加,桩荷载分担比先减小后增大,呈抛物线形,存在合理桩宽比。填土高度较小时,合理桩宽比较小,当填土高度增大到一定高度时,继续增加填土高度,合理桩宽比不变,趋于稳定。(3)通过正交试验,分析了填土高度、桩宽比、内摩擦角、粘聚力等因素对土拱效应影响的敏感性。(4)通过水平活动门实验验证了土拱效应的存在。分析了内摩擦角、粘聚力、桩宽比、深度等因素对桩荷载分担比的影响。
[Abstract]:The soil arch effect is a phenomenon that the earth pressure is transferred to the pile by adjusting the stress distribution inside the soil. The essence of this phenomenon is that the soil can fully mobilize its shear resistance to resist earth pressure. In 1943, Terzaghi verified the existence of soil arch effect through the famous "movable door" test, and then the scholars at home and abroad proved the existence of soil arch effect through theoretical analysis and various model tests. With the help of numerical calculation software, the occurrence mechanism, existing mode and influencing factors of soil arch effect are deeply studied. There are more and more measured data about the soil arch effect, and the theoretical research is getting deeper and deeper. The soil arch effect has been considered in the engineering, and good economic benefit has been obtained in the practical application. At present, the theoretical research on soil arch effect is not systematic enough, and there are many problems worth discussing in numerical calculation, especially the determination of soil arch mode and reasonable pile width ratio, which directly affects whether the soil arch effect can be further applied in engineering. Therefore, it is necessary to continue the work from the basic research. In this paper, based on the vertical and horizontal movable door tests, and with the aid of mathematical simulation software, the effects of the width, cohesion and angle of internal friction of the moving door on the soil arch effect are deeply analyzed. The soil arch effect model is established and the reasonable pile width ratio is put forward, which is of great theoretical significance for guiding the engineering design. The main conclusions of this paper are as follows: (1) through the vertical movable door experiment, the occurrence mechanism and existing conditions of soil arch under different soil mass and different active door width are studied, as well as the influence on the load-sharing ratio of pile. The relationship between the shape of sand arch axis and the width of movable door and the angle of internal friction is analyzed. The relationship between the load sharing ratio of pile and the width of movable door and the angle of internal friction is established. (2) the reasonable ratio of pile width to pile width is determined when the vertical soil arch is effective. With the increase of pile width ratio, the pile load sharing ratio decreases first and then increases with the increase of pile width ratio, showing parabola shape and reasonable pile width ratio. When the filling height is increased to a certain height, the reasonable ratio of pile width to pile width is constant and tends to be stable. (3) through orthogonal test, the height of fill, the ratio of pile width to pile width, and the angle of internal friction are analyzed. (4) the existence of soil arch effect is verified by horizontal gate experiment. The effects of internal friction angle, cohesion force, pile width ratio and depth on load sharing ratio of pile are analyzed.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU41

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