剪切波速和含水率双指标评价黄土震陷方法研究

发布时间：2018-05-22 12:44

本文选题：黄土 + 震陷　；参考：《中国地震局兰州地震研究所》2017年硕士论文

【摘要】：黄土震陷是地震作用下黄土的大孔隙结构产生崩溃性破坏而引发的地震灾害,具体表现为地面塌陷和黄土滑坡等。历史上因强烈地震引发的黄土震陷灾害带来了生命和财产的极大损失。黄土震陷问题已经引起了人们的重视,目前评价黄土震陷的方法主要是室内实验测试不同深度的震陷系数,利用分层总和法计算震陷量。本文在前人研究的基础上,通过对兰州新区及周边地区大量剪切波速、含水率和震陷实验资料的统计分析,给出了利用剪切波速和含水率双指标评价黄土震陷的方法。通过研究,本论文取得了以下几方面结论:1.选取了剪切波速和含水率两个独立的参数组成评价震陷的参数体系,分析了剪切波速和含水率与震陷系数的关系。在一定含水率条件下,随着剪切波速的增大震陷系数减小。在一定剪切波速情况下,随着含水率的增大震陷系数增大;并且剪切波速越大,随着含水率的增大震陷系数增长的越缓慢。2.分析了剪切波速和含水率在震陷过程中的相互关系,提出天然震陷能力的概念。通过分析二者与震陷系数的关系,得出剪切波速反映着非饱和土体的强度特征和绝对变形量及含水率影响非饱和土体的强度特征和绝对变形量的释放的观点。在此基础上,提出表征黄土潜在震陷能力的概念—天然震陷系数,其与剪切波速呈正相关,含水率对天然震陷系数影响较小,但含水率对震陷过程的完成有着明显的影响。3.在预测黄土震陷方面,通过剪切波速拟合公式和含水率拟合公式得到两个震陷系数,通过对两个系数进行比较后,得出场地的实际震陷系数,再进行黄土场地震陷量的预测。在这种方法的指导下,可能存在两种工况:第一种工况,当由含水率拟合公式计算得到的震陷系数小于天然震陷系数,此时黄土的潜在震陷能力没有得到完全释放,实际震陷系数由含水量拟合公式计算。第二种工况,当依据含水率拟合公式计算得到的震陷系数大于天然震陷系数,此时黄土的潜在震陷能力得到完全释放,实际震陷系数由剪切波速拟合公式计算,即天然震陷系数。4.利用剪切波速和含水率双指标对兰州新区黄土震陷特性进行了评价,并与室内震陷试验结果对比验证。结果表明,预测结果与室内震陷试验预测结果基本相符。本论文的研究成果为黄土震陷评价提供了较好的思路,具有较大的工程意义。
[Abstract]:Loess earthquake subsidence is a kind of earthquake disaster caused by the collapse of the pore structure of loess caused by earthquake, which is manifested as ground collapse and loess landslide. In history, great losses of life and property were caused by the earthquake subsidence disaster of loess caused by strong earthquake. People have paid more attention to the problem of loess seismic subsidence. At present, the evaluation method of loess seismic subsidence is mainly to test the seismic subsidence coefficient of different depth through laboratory experiments, and to calculate the seismic subsidence by using the method of stratified summation. On the basis of previous studies, this paper presents a method for evaluating loess seismic subsidence by means of statistical analysis of a large number of shear wave velocity, water content and seismic subsidence experimental data in Lanzhou New area and its surrounding area. Through the research, this paper has obtained the following several aspects of conclusion: 1. Two independent parameters of shear wave velocity and water content are selected to evaluate seismic subsidence. The relationship between shear wave velocity and water content and seismic subsidence coefficient is analyzed. Under certain water content, the seismic trapping coefficient decreases with the increase of shear wave velocity. In the case of certain shear wave velocity, the seismic trapping coefficient increases with the increase of water content, and the larger the shear wave velocity, the slower the seismic trapping coefficient increases with the increase of water content. The relationship between shear wave velocity and water content in the process of seismic subsidence is analyzed, and the concept of natural seismic trapping ability is put forward. By analyzing the relationship between the shear wave velocity and the seismic subsidence coefficient, it is concluded that the shear wave velocity reflects the strength characteristics of unsaturated soil and the effect of absolute deformation and moisture content on the strength characteristics and release of absolute deformation of unsaturated soil. On this basis, the concept of natural seismic subsidence coefficient, which represents the potential seismic subsidence ability of loess, is put forward, which is positively related to shear wave velocity, and water content has little effect on natural seismic subsidence coefficient, but water content has obvious influence on the completion of seismic subsidence process. In the aspect of predicting loess seismic subsidence, two seismic subsidence coefficients are obtained by shear wave velocity fitting formula and water content fitting formula. After comparing the two coefficients, the actual seismic subsidence coefficient of the site is obtained, and then the earthquake subsidence of loess field is predicted. Under the guidance of this method, there may be two conditions: first, when the seismic subsidence coefficient calculated by the water content fitting formula is less than that of the natural seismic subsidence coefficient, the potential seismic subsidence capacity of loess is not completely released. The actual seismic subsidence coefficient is calculated by the fitting formula of water content. In the second case, when the seismic subsidence coefficient calculated by water content fitting formula is larger than that of natural seismic subsidence coefficient, the potential seismic subsidence capacity of loess is completely released, and the actual seismic subsidence coefficient is calculated by shear wave velocity fitting formula. That is, natural seismic subsidence coefficient. The seismic subsidence characteristics of loess in Lanzhou New area were evaluated by using the double indexes of shear wave velocity and water content, and the results were compared with the results of indoor seismic subsidence test. The results show that the predicted results are in good agreement with the results of indoor seismic subsidence test. The research results of this paper provide a good idea for evaluation of loess seismic subsidence and have great engineering significance.
【学位授予单位】：中国地震局兰州地震研究所
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU444;TU435

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