深圳地区典型地质基坑开挖引起坑底回弹变形研究

发布时间：2018-07-05 05:45

本文选题：深圳典型地质 + 基坑开挖　；参考：《北京交通大学》2017年硕士论文

【摘要】：近年来,深圳地区地铁车站、地下建筑等基坑工程不断朝着多、大、深、密等方向发展。为确保基坑工程的顺利完成,坑底回弹变形作为评价基坑稳定性的重要指标,应在基坑开挖之前做好准确的分析与计算。然而,深圳地区有其独特的地质和工程条件,现有的坑底回弹变形研究相对较少,其他地区的研究成果并不完全适用。因此,需要针对深圳地区典型地质进行坑底回弹变形规律分析和计算方法等方面研究。本文结合深圳地铁车公庙站物业大厦基坑工程,研究了深圳地区典型地质基坑开挖引起的坑底回弹变形问题。通过土的固结试验,分析了深圳地区6种典型土层的卸荷回弹变形规律,得出了上述土层的回弹模量计算公式。应用三维有限元分析软件,考察并采用修正剑桥模型作为深圳典型土层的本构关系模型,模拟计算了 3种深度基坑开挖引起的坑底回弹变形。基于试验数据并将数值模拟结果与现有坑底回弹变形计算方法结果相对比,分析了各方法在深圳地区的适用性。针对深圳地铁车公庙站基坑工程实例建立了三维有限元分析模型,通过对现场监测数据与数值模拟结果的对比分析,验证了数值模拟方法合理性与结果的准确性。通过数值模拟计算,研究了基坑开挖时间与空间效应以及复杂条件对坑底回弹变形的影响,提出了一种适用于深圳地区的坑底回弹变形的计算方法。主要得出以下结论:(1)通过固结试验对深圳地区6种典型土层(杂填土、粉质黏土、粗砂、砾质粘性土、全风化花岗岩和强风化花岗岩)进行了研究,结果表明:深圳地区典型土层的回弹变形与卸荷比、土层类别和最大固结应力等因素有关;应用回弹指数求回弹模量的方法,能准确地考虑到上述因素对回弹模量的影响,适用于深圳地区典型土层回弹模量的计算。(2)通过比较现有的坑底回弹变形计算方法在深圳地区的适用性,研究发现:自重应力抵消法机理明确,所需参数较少,回弹模量计算公式与本文试验验证的公式一致;并且,自重应力抵消法与规范方法和残余应力法相比,计算结果与数值模拟计算结果吻合程度较高,若对此方法加以修正则更适用于深圳地区。(3)通过对深圳地铁车公庙站基坑工程实例的数值模拟分析,研究发现:基坑开挖的时空效应以及复杂条件(邻近既有建筑、工程桩、逆作法工序)等因素对坑底回弹变形均有影响,并基于数值模拟结果对自重应力抵消法的回弹量计算公式进行了修正。(4)基于本文对坑底回弹变形机理、影响因素等各方面的研究以及对现有坑底回弹变形计算方法的对比与修正,得出一整套修正的坑底回弹变形计算方法。并且,采用修正的方法计算深圳地铁车公庙站物业大厦基坑工程实例,对比发现其计算结果与数值模拟结果基本一致,具有较高的工程参考意义。
[Abstract]:In recent years, subway stations, underground buildings and other excavation projects in Shenzhen area have been developing in many, large, deep and dense directions. In order to ensure the smooth completion of foundation pit engineering, the rebound deformation of the pit bottom is an important index to evaluate the stability of foundation pit. The accurate analysis and calculation should be done before the foundation pit is excavated. However, Shenzhen has its unique geological and engineering conditions, and the existing research on rebound deformation of the pit bottom is relatively few, and the research results in other areas are not fully applicable. Therefore, it is necessary to analyze and calculate the springback deformation law of the pit bottom in the typical geology of Shenzhen area. In this paper, the problem of rebound deformation of pit bottom caused by excavation of typical geological foundation pit in Shenzhen area is studied with the foundation pit of Cegongmiao Station property Building of Shenzhen Metro. Based on the consolidation test of soil, the unloading and springback deformation of six typical soil layers in Shenzhen area is analyzed, and the formula for calculating the elastic modulus of the above soil layers is obtained. By using the three-dimensional finite element analysis software, the modified Cambridge model is used as the constitutive relation model of the typical soil layer in Shenzhen, and the springback deformation of the pit bottom caused by the excavation of three kinds of deep foundation pit is simulated and calculated. Based on the experimental data and comparing the numerical simulation results with the results of the existing methods for calculating the springback deformation of the pit bottom, the applicability of each method in Shenzhen area is analyzed. A three-dimensional finite element analysis model is established for the excavation engineering of Cegongmiao Station in Shenzhen Metro. The rationality and accuracy of the numerical simulation method are verified by comparing the monitoring data with the numerical simulation results. Through numerical simulation, the effects of excavation time and space and complex conditions on the springback deformation of the pit bottom are studied. A method for calculating the springback deformation of the pit bottom in Shenzhen area is proposed. The main conclusions are as follows: (1) six typical soil layers (mixed fill, silty clay, coarse sand, gravel clayey soil, fully weathered granite and strongly weathered granite) in Shenzhen area were studied by consolidation tests. The results show that the springback deformation of typical soil layer in Shenzhen area is related to the factors such as unloading ratio, soil layer category and maximum consolidation stress, and the effect of the above factors on the springback modulus can be accurately considered by using the springback index to calculate the springback modulus. It is suitable for the calculation of springback modulus of typical soil layer in Shenzhen area. (2) by comparing the applicability of the existing calculation methods of springback deformation in Shenzhen area, it is found that the deadweight stress canceling method has a clear mechanism and requires less parameters. The calculation formula of springback modulus is consistent with the formula verified by the experiment in this paper, and the calculation results of deadweight stress canceling method are in good agreement with the numerical simulation results compared with the standard method and the residual stress method. If this method is modified, it will be more suitable for Shenzhen area. (3) through the numerical simulation analysis of the excavation engineering example of Cegongmiao Station in Shenzhen Metro, it is found that the space-time effect and complex conditions of excavation (adjacent to existing buildings, engineering piles, etc.) Based on the numerical simulation results, the springback calculation formula of deadweight stress cancellation method is modified. (4) based on this paper, the springback deformation mechanism of the pit bottom is studied. Based on the study of the influencing factors and the comparison and correction of the existing methods for calculating the springback deformation of the pit bottom, a whole set of modified calculation methods for the springback deformation of the pit bottom are obtained. In addition, the modified method is used to calculate the foundation pit project of Cegongmiao Station property Building in Shenzhen Metro. The comparison shows that the calculated results are in good agreement with the numerical simulation results, which is of high engineering reference significance.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753;TU433

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