基坑土层m值反演分析研究

发布时间：2018-03-07 08:29

本文选题：基坑　切入点：等效m值　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：在基坑工程中,由于平面竖向弹性地基梁法计算模式明确、计算过程简单,在实际工程中得到广泛的应用。其中,土的水平反力系数的比例系数—m值的取值尤为关键,不仅影响到支护结构的变形和内力,甚至决定了支护结构的设计和围护方案的选择。限于试验条件的限制,目前的工程勘察报告中尚不能正确提供各类土层的水平基床系数,现有的规程和指南虽给出了 m值的参考值,但选择的范围较大,取值存在不确定性和随意性。准确、合理的m值不仅能够真实反映结构实际的工作状态,也可为类似工程设计提供参考,具有重要的工程意义。本文依据实测水平位移监测数据,采用了基于样条函数反分析和基于弹性支点法的正分析相结合的方法对基坑土层等效m值进行反演,具体开展了以下几个方面的研究工作:(1)本文在假定和简化的基础上,对平面杆系结构弹性支点法中土的水平反力系数进行了分析,得到了与其有关的系数△1、△2且提出了一个综合考虑土体重度γ,基坑开挖深度h,侧压力系数k0和抗剪强度指标的等效m值计算公式。(2)采用光顺样条函数,按一定的光顺准则和逼近准则对水平位移监测数据进行平滑处理;然后,利用B样条函数对平滑后的数据进行插值,得到基坑支护桩的位移样条函数,对位移样条函数求导,反算出基坑支护桩的内力值。(3)按平面杆系结构弹性支点法,建立基坑力学计算模型,采用矩阵位移法正算基坑支护桩的变形和内力值。(4)将△1、△2作为待反演参数,在其取值范围内枚举出大量的参数组合,逐一代入正算模型中计算,得到每种组合所对应的支护桩的变形和内力值。利用实际变形和反算内力值筛选出其允许容差范围内的正算值所对应的参数样本,以确定系数△1、△2,从而间接反演得到基坑土层等效m值。(5)选取某一实际工程,依照上述反分析方法反演确定系数△1、△2,并由此计算出下一工况的基坑土层等效m值,将其代入基坑力学计算模型,正算出基坑支护桩后续工况的变形和内力值,并与位移实际值和内力反算值作比较,验证反分析结果的可靠性与反分析算法的可行性。
[Abstract]:In foundation pit engineering, the calculation model of beam method for plane vertical elastic foundation is clear, and the calculation process is simple, so it is widely used in practical engineering, among which, the ratio coefficient -m of horizontal reaction coefficient of soil is particularly important. It not only affects the deformation and internal force of the supporting structure, but also determines the design of the supporting structure and the selection of the enclosure scheme. Limited to the limit of the test conditions, the horizontal bed coefficient of all kinds of soil can not be correctly provided in the present engineering survey report. Although the existing regulations and guidelines give the reference value of m value, but the selection range is large, the value is uncertain and arbitrary, the accurate and reasonable m value can not only truly reflect the actual working state of the structure. It can also be used as a reference for similar engineering design and has important engineering significance. In this paper, the equivalent m value of foundation pit soil layer is inversed by the combination of spline function back analysis and forward analysis based on elastic fulcrum method. The following research work is carried out in detail: 1) on the basis of supposition and simplification, this paper is based on the assumption and simplification. The horizontal reaction coefficient of soil in the elastic fulcrum method of plane bar structure is analyzed. The relative coefficient of 1, 2 is obtained and a formula of equivalent m value of considering soil weight 纬, excavation depth of foundation pit, lateral pressure coefficient k _ 0 and shear strength index is proposed, which adopts fairing spline function. The horizontal displacement monitoring data are smoothed according to certain fairing criterion and approximation criterion, and then the displacement spline function of foundation pit supporting pile is obtained by interpolating the smooth data with B-spline function, and the displacement spline function is derived. The mechanical calculation model of foundation pit is established according to the elastic fulcrum method of plane bar structure, and the deformation and internal force of supporting pile of foundation pit are calculated by matrix displacement method. A large number of parameter combinations are enumerated in the range of their values, and are substituted one by one into the positive calculation model. The deformation and internal force of the supporting pile corresponding to each combination are obtained. By using the actual deformation and the inverse internal force, the parameter samples corresponding to the positive values within the allowable tolerance range are selected. In this paper, the equivalent m value of foundation pit soil layer is obtained by indirect inversion, and then a practical project is selected, and the coefficient 1, 2 is obtained according to the above inverse analysis method, and the equivalent m value of foundation pit soil layer under the next working condition is calculated. The deformation and internal force of the foundation pit supporting pile are calculated by the mechanical calculation model of foundation pit, and compared with the actual displacement value and the back calculation value of the internal force, the reliability of the back analysis result and the feasibility of the back analysis algorithm are verified.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753

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