岩质边坡倾斜桩基横向承载性能的模型试验研究

发布时间：2019-01-12 07:04

【摘要】：西南地区地貌多变、地质条件复杂,需建设大量铁路网、公路网,当线路跨越河流、沟谷或者山区时,往往需要修筑桥梁以连接线路,需要布设桥梁桩基础。现阶段对桩横向承载性能的研究主要还是针对在水平地基中的桩,对于岩质边坡上的斜桩基础横向受力机理,研究文献非常少,没有系统的理论和方法对其进行分析,本文主要以模型试验为研究手段,通过数值模拟对模型试验结果进行对比分析,得到一些结论,希望对实际工程实际和理论研究能起一定参考价值。主要得到以下几点结论(1)岩质边坡上倾斜桩基础在横向受荷的情况下,弯矩整体分布趋势呈由地面沿桩身先增大后减小再最后衰减为零的非线性分布,当桩埋深在14D～17D时,最大弯矩分布在坡面到(6D～9D)之间,且随横向荷载增加,弯矩值不断变大,但不改变其分布规律,桩身坡面处横向位移随横向加载量级增大而增加,部分位移曲线随荷载增加曲线斜率增加。(2)轴力对岩质边坡上倾斜桩基础横向受荷性能影响:先有轴力作用的斜桩横向承载能力提高,桩承受的轴向压力相当于预先给桩施加了预应力,使得其横向抗弯刚度提高,横向承性能加强。(3)滑带对岩质边坡上倾斜桩基础横向受荷性能影响:滑带的存在使得同级荷载下的桩弯矩更大,滑带造成桩周岩土介质不连续,降低了边坡的稳定性,使得边坡上的斜桩横向承载能力变弱,所以在进行基桩设计时,要充分考虑岩体性质。(4)抗弯刚度对岩质边坡上倾斜桩基础横向受荷性能影响:桩身抗弯刚度越大,弯矩值越大,地表横向位移越小;桩身抗弯刚度越小,弯矩值越小,地表横向位移越大,横向力由桩身刚度大的桩分担的比率大于刚度小的桩分担的比率。提高抗弯刚度,可以有效提高桩基的横向承载能力。(5)坡体推力对岩质边坡上倾斜桩基础横向受荷性能影响:岩质边坡桩滑面以上坡体推力沿桩身整体分布呈抛物线型,滑面以上桩前土压力分布呈增大的三角形分布;滑面以下土抗力呈倒三角形分布。a、桩地面位置弯矩接近零,其弯矩分布形式和单独横向荷载作用、有轴压作用时的横向加载作用下的内力分布规律不一样。坡体推力作用时桩身嵌固越深,桩抵御坡体推力能力提高愈明显,合理地增加倾斜桩基嵌固深度,对于提高其抗坡体推力承载性能有较大的改善。b、坡体推力和横向力共同作用时,桩横向位移发展较快,对于坡体推力作用下横向受荷下岩质边坡斜桩受力性能并不是将坡体推力单独作用与横力单独作用进行简单的叠加,要考虑二者耦合的影响,二者的耦合使得弯矩更大,将对斜桩的横向承载性能不利。因此在设计相类似的桥梁桩基时,对可能存在的坡体推力要引起重视。
[Abstract]:The geomorphology of southwest area is changeable and the geological conditions are complicated. A large number of railway and highway networks are needed. When the lines cross rivers, valleys or mountain areas, it is often necessary to build bridges to connect the lines, and to set up bridge pile foundations. At present, the research on the lateral bearing capacity of pile is mainly aimed at the pile in the horizontal foundation. The research literature on the lateral force mechanism of the inclined pile foundation on the rock slope is very few, and there is no systematic theory and method to analyze it. This paper mainly takes the model test as the research means, through the numerical simulation carries on the contrast analysis to the model test result, obtains some conclusions, hopes to have certain reference value to the actual engineering practice and the theory research. The main conclusions are as follows: (1) when the slope pile foundation on the rock slope is subjected to transverse load, the overall distribution trend of bending moment is a nonlinear distribution, which increases first along the pile body and then decreases to zero at last. When the pile buried depth is 14D~17D, the maximum bending moment is distributed between slope surface and (6D~9D), and with the increase of transverse load, the bending moment value increases continuously, but does not change its distribution law, and the lateral displacement of pile slope increases with the increase of transverse loading order. The slope of partial displacement curve increases with the increase of load. (2) the influence of axial force on lateral load performance of inclined pile foundation on rock slope: the lateral bearing capacity of inclined pile with axial force is increased. The axial pressure on the pile is equivalent to prestressing the pile in advance, so that the lateral bending stiffness of the pile is increased. (3) the influence of slip zone on lateral load performance of inclined pile foundation on rock slope: the existence of slip zone makes the bending moment of pile under the same load greater, and the slip zone causes discontinuity of rock and soil media around pile, which reduces the stability of slope. The lateral bearing capacity of inclined pile on slope becomes weaker, so when designing foundation pile, the rock mass property should be fully taken into account. (4) the flexural stiffness of inclined pile foundation on rock slope is affected by transverse load performance: the greater the bending stiffness of pile is, The larger the bending moment is, the smaller the lateral displacement is. The smaller the bending stiffness of pile is, the smaller the bending moment is and the greater the lateral displacement is. The ratio of lateral force shared by pile with large stiffness is larger than that of pile with small stiffness. The lateral bearing capacity of pile foundation can be improved effectively by increasing flexural stiffness. (5) the lateral load behavior of inclined pile foundation on rock slope is affected by slope thrust. The distribution of earth pressure in front of piles above the sliding surface is triangular. The resistance of the soil below the sliding surface is distributed in an inverted triangle. A, the bending moment of the pile is close to zero, and the distribution of the bending moment is different from that of the single lateral load, and the distribution law of the internal force under the lateral loading under axial compression is different. The deeper the pile body is embedded in the slope body, the more obvious the resistance of the pile to the slope body thrust is, and the more reasonable increase in the embedded depth of the inclined pile foundation is, the greater the bearing capacity of the slope body thrust can be improved. The pile lateral displacement develops rapidly when the slope body thrust and transverse force act together, so the slope pile under lateral loading is not simply superposed by the slope thrust and the transverse force. The influence of coupling between them should be considered, which makes the bending moment bigger, which will be unfavorable to the lateral bearing capacity of inclined pile. Therefore, in the design of similar bridge pile foundation, attention should be paid to the possible slope thrust.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U443.15

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