浙江舟山Ⅱ类场地剪切波速不确定性研究

发布时间：2018-11-03 19:22

【摘要】：土层的剪切波速是土体动力特性的重要参数。对剪切波速以及其相关方面的研究是当前岩土工程抗震领域的重要研究内容之一,剪切波速的大小不仅可以反映介质对波的传播能力,而且还可以反映土体的“软硬”程度,它可以评价场地土类别,土层覆盖层厚度、判别砂土或粉土地基的地震液化、计算土体的动剪切模量以及建筑抗震设计等,因此,它有着非常重要的理论价值和工程实际意义,被广泛的应用在各种重大工程、一级建筑以及有特殊技术要求的建筑中。然而,岩土材料最重要的特征之一就是岩土参数的不确定性和变异性。岩土是一种相当复杂的地质体,由于土层特性、地质成因以及土体结构的不同,使得同一土层在不同的条件下剪切波速值都具有明显的差异性。而且在实际工程应用中,钻孔埋深、地下埋藏情况、测试方法、测试人员等因数都对剪切波速的测试结果产生较大的影响,使得同一测试点,多次测试的情况下所得的剪切波速值也会具有明显的差异性,因此如果能对剪切波速的这种不确定性进行科学的估计,就越能反映土层的真实剪切波速值或者给出合理的剪切波速范围,这样就越能准确的反映土层的真实状况,因此,根据现有的波速资料,结合实测的剪切波速值,研究分析其不确定性,这是一项很有意义的研究工作。本文通过现场实测,以舟山定海区某创业园作为剪切波速测试场地,在同一钻孔内进行多次测试,获取波速数据,围绕剪切波速不确定性进行统计分析,过程中主要开展了以下工作:(1)试验前,查阅了大量国内外的剪切波速相关文献以及科研资料,系统地分析总结了到目前国内外剪切波速的研究情况,以及在剪切波速研究过程中还存在的主要问题和今后的主要研究方向;(2)本文系统介绍了场地剪切波速测试技术,包括剪切波速的测试原理、测试方法以及技术参数;还介绍了目前使用较为广泛的几种测试仪器,包括仪器的适用范围、测试方法以及优缺点;(3)本文以舟山定海区某创业园作为剪切波速测试场地,对同一钻孔进行多次测试,测试方法采用单孔法,从下到上以1m为间隔布置测试点,共测试了35组样本,对测试结果不确定性进行统计分析;(4)主要从以下三个方面研究了剪切波速的不确定性:同一埋深剪切波速的不确定性、主要土层剪切波速的不确定性以及等效剪切波速的不确定性,统计分析过程中,采用2c检验方法分析剪切波速的频率分布曲线,统计三种情况下剪切波速的特征值,并通过百分位数法的直接计算法给出相应的95%、85%、75%参考值上限和下限以及相对平均值的波动幅度,试验获得的结果可用于检验场地剪切波速测试结果的可靠性。
[Abstract]:The shear wave velocity of soil is an important parameter of soil dynamic characteristics. The research on shear wave velocity and its related aspects is one of the important research contents in the field of earthquake resistance in geotechnical engineering. The magnitude of shear wave velocity can not only reflect the propagation ability of medium to wave, but also reflect the "soft and hard" degree of soil mass. It can evaluate site soil type, soil cover thickness, distinguish seismic liquefaction of sand or silt foundation, calculate dynamic shear modulus of soil and aseismic design of building, etc. Therefore, it has very important theoretical value and engineering practical significance. It is widely used in major projects, primary buildings and buildings with special technical requirements. However, one of the most important characteristics of geotechnical materials is the uncertainty and variability of geotechnical parameters. Rock and soil is a very complex geological body. Because of the difference of soil layer characteristics, geological origin and soil structure, the shear wave velocities of the same soil layer are obviously different under different conditions. Moreover, in practical engineering application, factors such as drilling depth, underground burial situation, testing method, testing personnel and other factors all have a great influence on the test results of shear wave velocity, which makes the same test point. In the case of multiple tests, the shear wave velocities will also have obvious differences, so if the uncertainty of shear wave velocity can be estimated scientifically, The more it can reflect the true shear wave velocities of the soil layer or the reasonable range of the shear wave velocities, the more accurately it can reflect the true state of the soil layers. Therefore, according to the existing wave velocity data, combined with the measured shear wave velocities, Research and analysis of its uncertainty, this is a very meaningful research work. In this paper, a pioneering park in Dinghai District of Zhoushan is used as the testing site of shear wave velocity through field measurement, and several tests are carried out in the same borehole to obtain wave velocity data, and statistical analysis is carried out around the uncertainty of shear wave velocity. The main works are as follows: (1) before the experiment, a large number of domestic and foreign literature on shear wave velocity and scientific research data were consulted, and the current research situation of shear wave velocity at home and abroad was systematically analyzed and summarized. The main problems existing in the study of shear wave velocity and the main research directions in the future are also discussed. (2) this paper systematically introduces the testing technology of site shear wave velocity, including the measuring principle, testing method and technical parameters of shear wave velocity; It also introduces several kinds of testing instruments which are widely used at present, including the scope of application, test methods, advantages and disadvantages of the instruments. (3) in this paper, a start-up park in Dinghai District of Zhoushan is used as the testing site of shear wave velocity, and the same borehole is tested many times. The testing method is single hole method, and the test points are arranged at a interval of 1 m from bottom to top. A total of 35 groups of samples have been tested. The uncertainty of test results is analyzed statistically. (4) the uncertainty of shear wave velocity is studied from the following three aspects: the uncertainty of the shear wave velocity in the same buried depth, the uncertainty of the shear wave velocity in the main soil layer and the uncertainty of the equivalent shear wave velocity. The frequency distribution curve of shear wave velocity is analyzed by using 2c test method, and the eigenvalues of shear wave velocity in three cases are statistically analyzed, and the corresponding 95 ~ 85th part is given by the direct calculation method of percentile method. The upper and lower bound of 75% reference value and the fluctuation range of relative average value can be used to test the reliability of the measured results of shear wave velocity.
【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU435

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