全风化花岗岩试验及本构模型研究

发布时间：2017-12-28 20:38

本文关键词：全风化花岗岩试验及本构模型研究　出处：《华南理工大学》2016年博士论文　论文类型：学位论文

【摘要】：全风化花岗岩在我国华南地区分布十分广泛,是工程建设中常见的岩土材料与工程载体。然而,由于对全风化花岗岩没有全面的了解以及深入、系统的研究,导致在工程建设中频繁发生事故,对工程安全以及人民生命财产安全造成威胁。可见,开展对全风化花岗岩全面、系统的研究工作意义重大且迫在眉睫。本文以深圳地区全风化花岗岩为研究对象,对其展开了全面的基本物理性质试验研究以及三轴试验研究,并提出了适用于原状全风化花岗岩的修正结构性剑桥模型以及适用于重塑全风化花岗岩的双边界面模型,为相关的工程应用提供参考和依据。基本物理性质试验包括比重试验、含水率试验、界限含水率试验、击实试验、颗粒分析试验、矿物成分分析试验以及化学成分分析试验。根据试验结果可知,土样的矿物成分以石英和高岭石为主,其他矿物含量较少,土体为级配不良的不均匀土,可分类为粉粘土质砂土,风化程度为全风化,即土样为全风化花岗岩。三轴试验包括原状土的各向等压加载试验、固结排水试验以及固结不排水试验;重塑土的各向等压加卸载试验、固结排水试验、固结不排水试验、等p’剪切试验、不同固结状态下(偏压固结)的不排水试验以及不同超固结比下的不排水试验;掺水泥重塑土的各向等压加载试验以及固结排水试验。重塑土三轴试验结果表明其应力应变关系特征符合临界状态土力学理论,故首先采用修正剑桥模型对重塑土固结不排水以及固结排水试验进行模型计算。模型计算结果与试验曲线的对比表明,修正剑桥模型在模拟本文所研究的全风化花岗岩重塑土力学行为时主要存在以下几点不足:1)不能计算各向等压加卸载试验中再加载过程土体产生的塑性变形;2)不能准确地计算固结不排水试验中的孔压,且不能模拟土样在剪切过程中发生的相变现象;3)不能准确地计算较高围压下固结排水试验中的体变。为此,本文基于临界状态理论与边界面弹塑性土力学理论,同时考虑了状态参数?对剪胀系数的影响,在偏应力q-平均有效主应力p’坐标平面中建立了一个双边界面模型,并在matlab软件中编写了模型代码。模型计算结果与试验的对比表明,相对于修正剑桥模型而言,本文双边界面模型能够准确地计算各向等压加卸载试验中再加载过程土体产生的塑性变形;能够更准确地计算固结不排水试验孔压曲线,且能够模拟剪切过程中发生的相变现象;能够在一定程度上计算不同超固结比下不排水剪切试验应力应变关系曲线,比修正剑桥模型计算曲线更接近试验曲线。可见,对于所研究的重塑全风化花岗岩而言,相比于修正剑桥模型,本文提出的双边界面模型能更好地模拟其力学特性。原状土与掺水泥重塑土都有着土体初始结构,为结构性土,首先采用应用较为广泛的结构性剑桥模型对其固结排水试验进行模型计算。模型计算结果与试验曲线的对比表明,结构性剑桥模型在模拟所研究的结构性全风化花岗岩力学行为时主要存在以下几点不足:1)模型不能准确地计算低围压下的峰值偏应力,且不能较好地模拟土体在低围压下剪切过程中产生的剪胀;2)当围压较高时,模型计算得出的体应变偏大,导致通过流动法则计算得出的剪应变也会偏大,以致土体在塑性阶段偏应力增量变化不大的情况下,计算得到的剪应变增量偏大,模型偏应力曲线与试验曲线差别较大。为此,本文在结构性剑桥模型的基础上,对其屈服函数以及塑性体应变的计算两个方面做了适当的修正,将修正后的模型称为“修正结构性剑桥模型”,并在matlab软件中编写了模型代码。模型计算结果与试验曲线的对比表明,相对于结构性剑桥模型而言,本文模型能更准确地计算土体在低围压下的峰值偏应力,也能更好地模拟低围压下产生的剪胀;高围压下的计算偏应力曲线与体变曲线也更接近试验曲线。可见,对于所研究的结构性全风化花岗岩而言,相比于结构性剑桥模型,本文提出的模型能更好地模拟其力学特性。
[Abstract]:All weathered granite is widely distributed in the Southern China area of China. It is a common geotechnical material and engineering carrier in the construction of engineering. However, due to the lack of a comprehensive understanding of deep weathered granite and thorough and systematic research, accidents happen frequently in engineering construction, which pose a threat to engineering safety and people's life and property safety. Therefore, it is of great significance and imminent to carry out the comprehensive and systematic research on the fully weathered granite. This article takes the Shenzhen area of whole weathered granite as the object of study, carried out experimental study on basic physical properties and comprehensive experimental research on the three axis, and puts forward suitable undisturbed weathered granite modified structural model and interface model for bilateral Cambridge to reshape the whole weathered granite, and provide reference for the related engineering applications. The basic physical properties tests include specific gravity test, moisture content test, limiting moisture content test, compaction test, particle analysis, mineral composition analysis and chemical composition analysis. According to the test results, the mineral composition of the soil samples is mainly composed of quartz and kaolinite, and the other minerals are few. The soil is uneven soil with poor gradation. It can be classified as silty clay sand. The weathering degree is totally weathered, namely the soil sample is completely weathered granite. Three axis test including undisturbed soil under isotropic loading test, consolidation test and consolidated undrained test; isotropic loading test, consolidation test, consolidation of remolded soil undrained tests, P shear test, different consolidation conditions (consolidated undrained test) and different overconsolidation ratios under undrained test; cement remolded the isotropic loading test and consolidation test. The results of three axis test of remolded soil show that the relationship between stress and strain is in accordance with the theory of critical state soil mechanics. First, the modified Cambridge model is applied to calculate the consolidation and drainage of remolded soil and consolidation drainage test. Compared the calculation results of the model and experimental curve, the whole weathered granite of remolded soil mechanical behavior research in the simulation of the modified Cambridge model mainly exist the following problems: 1) could not calculate the isotropic loading and unloading tests in the loading process of soil produced by plastic deformation; 2) cannot accurately calculate the consolidated undrained test the pore pressure, phase transition and cannot simulate the soil in the cutting process; 3) cannot be accurately calculated under high confining pressure consolidation test in volume change. Therefore, the theory and the boundary surface elasto-plastic critical state soil mechanics based on the theory, considering the state parameters? Of dilatancy coefficient, the deviatoric stress q- effective mean principal stress of P 'coordinate plane to establish a bilateral interface model, and compile the code model in MATLAB software. Compared with the calculation results of the model test, compared with the modified Cambridge model, the bilateral interface model can accurately calculate isotropic loading and unloading tests in the loading process of soil produced by plastic deformation; able to accurately calculate the consolidated undrained test pore pressure curve, and can simulate the phase transition phenomenon occurs in the shearing process; to a certain extent, calculating different overconsolidation ratios under undrained shear test stress-strain curve, than the modified Cambridge model is more close to the calculated curve test curve. It can be seen that for the studied remolded fully weathered granite, compared with the modified Cambridge model, the bilateral interface model proposed in this paper can better simulate its mechanical properties. The original structure of undisturbed soil and cement mixed remolded soil has the initial structure of soil. For the structured soil, the model of the consolidation and drainage test is firstly calculated by the widely used structural Cambridge model. Compared the calculation results of the model and experimental curve, the structural model of Cambridge in the simulation of structural mechanical behavior of weathered granite mainly exist the following problems: 1) model can not accurately calculate the peak under low confining pressure and deviatoric stress, can better simulate soil dilatancy under low confining pressure generated under the shearing process; 2) when the confining pressure is higher, the volume strain model calculation is too large, resulting in the shear strain calculated by flow rule will be too large, so that the soil in the plastic stage of deviatoric stress increment is not the case, the calculated shear strain increment is too large, the model should be partial the force curve and test curve difference. For this reason, based on the structural Cambridge model, this paper corrections the yield function and the calculation of plastic strain in two aspects. The modified model is called the modified structural Cambridge model, and the model code is compiled in MATLAB software. Compared the calculation results of the model and experimental curve, relative to the Cambridge structural model, this model can accurately calculate the soil under low confining pressure under peak deviatoric stress, also can better simulate the low confining pressure under the dilatancy; partial stress curve and the volume change curve is closer to the test curve of high confining calculation of pressure. It can be seen that, for the structural fully weathered granite, compared with the structural Cambridge model, the model proposed in this paper can better simulate its mechanical properties.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TU45

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