林芝地区冰水堆积体本构模型及物理力学性能研究

发布时间：2018-05-10 22:23

本文选题：冰水堆积体 + 林芝地区　；参考：《成都理工大学》2017年硕士论文

【摘要】：林芝地区位于青藏高原的东南部,是我国典型的现代海洋性冰川活动区,受青藏高原冰期—间冰期气候的交替影响,冰川活动范围变化较大,充足的降雨及冰雪融水为冰水堆积体的发育提供了有利的水动力条件;此地区出露的地层主要有寒武系、泥盆系、石炭系、三叠—白垩系和第四系,岩性种类多,且多出现了不同程度的变质,受区域构造及构造运动的影响,为当时冰水堆积体的形成提供了丰富的固体物源条件。林芝地区典型的冰水堆积体多堆积在人烟稀少的高海拔地区,交通和工程建设都不方便。20世纪以前人们对冰水堆积体的研究极少,尤其是关于冰水堆积体工程力学性质尚缺乏系统性的全面研究,国内外选择在冰水堆积体上修建建筑物极为慎重。我国西部大开发的全面开展,又不可避免的要接触冰水堆积体,工程不能一味的采取绕避措施。本文以西藏林芝地区典型冰水堆积体为研究对象,在前人研究成果的基础上,通过野外地质调查和遥感解译等手段,对冰水堆积体的沉积特征、颗粒组成、地貌及分布特征、胶结程度等特性进行了野外详细的地调查和分析;进而在大量的室内试验和相关研究成果的基础上探究了冰水堆积体的击实试验、渗透特性、力学特性、温度及尺寸效应等;通过工程类比、参数反演等手段,求得一套冰水堆积体的宏观及微观参数,在参数确定的基础上,利用极限平衡法和数值模拟的思想,对冰水堆积体边坡的稳定性做了综合性评价。本文的研究成果在一定程度上补充了工程界和学术界在林芝地区冰水堆积体物理及力学性质研究上存在的不足,为工程的进展和学术的探讨提供了理论参数的取值及其变化规律的分析。本文的技术路线主要分为三个阶段:第一阶段是在查阅文献及收集相关资料的基础上,结合野外现场调查,主要研究林芝地区冰水堆积体的基本特征,采用的方法主要有现场测绘、颗分试验、原位渗透试验及一些辅助性的试验方法;第二阶段是利用野外采取的试样进行相应的室内试验,主要研究冰水堆积体的物理力学性质,本次用到的试验仪器主要有液塑限联合测定仪、多功能电动击实仪及脱模器、常水头渗透试验仪、大型三轴剪切试验仪、小型三轴剪切试验仪、中型直剪试验仪等。第三阶段是在前两个阶段成果研究的基础上,建立冰水堆积体本构模型和进行冰水堆积体边坡工程稳定性分析。通过以上研究思路及方法,主要取得了以下研究成果:(1)通过对林芝地区冰水堆积体的野外调查、现场颗分、渗透、容重等试验,结合不同含石量条件下的室内中型剪切试验成果,在传统分类方法的基础上,提出以冰水堆积体颗粒组成、胶结程度、渗透性能和力学性能为分类指标的综合分类方法,将冰水堆积体分为3级5个亚类。(2)冰水堆积体的渗透系数一般在i×10~(-3) cm/s,属于中等渗透介质;野外渗透试验的稳定时间多在2小时后达到;结合颗分试验,认为当细粒含量大于10%时对堆积体渗透性的影响较大。室内渗透试验表明随着水力梯度的增大,试样渗透速度呈近似线性~非线性增长,出口水流为清水时近似满足达西定律,浑浊水时明显不满足达西定律,但均能用相应的渗透本构关系描述。(3)击实试验表明:相同含石量条件下,试样干密度随着含水率的增加先增大后降低,有明显的峰值,即存在最优含水率和最大干密度;相同含水率的试样,试样干密度随着含石量的增大而增大;最优含水率整体均随着含石量的降低而增大;含石量40%可以作为冰水堆积体击实试验的一个分界点。(4)室内大型三轴压缩试验表明:冰水堆积体的黏聚力随着含水率的增加呈现先增加后减小的趋势,且具有明显的峰值点,并能用相应的多项式来拟合;内摩擦角随着含水率的增加整体呈降低的趋势,在含水率为5.07%~7.84%时,内摩擦角降低的幅度较少,曲线上基本趋于平缓。(5)室内小型三轴压缩试验表明:冰水堆积体的温度从-10℃~50℃的变化过程中,随着温度的增加黏聚力先增加后降低且趋于稳定,并在0℃时出现最大值。内擦角随着温度的增加,变化不大,是在很小的一个范围内波动变化。(6)低围压条件下,冰水堆积体的本构关系不符合邓肯-张模型。在邓肯-张本构模型的基础上,考虑应变软化和体胀的情况,对切线模量和切线泊松比进行修正,并验证了修正模型的正确性。(7)利用各种试验测得的物理力学参数,对评价区内一处冰水堆积体边坡进行了综合稳定性评价。利用数值模拟软件分析了边坡破坏后的堆积形态,同时也验证了颗粒流程序PFC~(3D)对散粒体介质堆积形态数值模拟的适用性。本文对林芝地区冰水堆积体的物理及力学性质的研究成果,与前人研究的一般成果相符。同时在前人研究成果的基础上,补充了有关冰水堆积体在野外识别及遥感解译、工程分类、工程特性、温度及尺寸效应等方面研究的不足。本次研究主要针对林芝地区,对其他地区冰水堆积体的研究仅提供相应的研究方法及相似物质的物理力学参数取值的比选;针对冰水堆积体本构模型的研究,本文仅作了应变软化条件下的模型修正分析,与现实情况可能还存在许多不足之处,为后期对冰水堆积体研究感兴趣的学者提供了一个研究方向。
[Abstract]:Linzhi area is located in the southeastern part of the Qinghai Tibet Plateau. It is a typical modern marine glacial area in China. It is influenced by the alternately climate of the glacial interglacial period of the Qinghai Tibet Plateau, and the range of glacial activity varies greatly. Sufficient rainfall and ice and snow melt provide favorable hydrodynamic conditions for the development of ice water accumulation. There are Cambrian, Devonian, Carboniferous, three fold Cretaceous and Quaternary, with many types of lithology and many metamorphism, which are influenced by regional tectonics and tectonic movements, which provide rich solid source conditions for the formation of ice water deposits at that time. The typical ice water deposits in Linzhi area are accumulated in the sparsely populated Gao Haiba. Regional, transportation and engineering construction are not convenient for people to study ice water accumulation before.20 century, especially about the lack of systematic and comprehensive research on the mechanical properties of ice water accumulation. It is very prudent to choose building buildings on ice water deposits at home and abroad. This paper takes the typical ice water accumulation in Linzhi area of Tibet as the research object. On the basis of the previous research results, the sedimentary characteristics, particle composition, geomorphic and distribution characteristics and the cementation degree of the ice water accumulation body are carried out on the basis of the previous research results. The detailed field investigation and analysis are carried out in the field, and on the basis of a large number of laboratory tests and related research results, the compaction test, permeability, mechanical properties, temperature and size effect of the ice water accumulation body are explored, and the macroscopic and microscopic parameters of a set of ice water accumulation body are obtained by means of engineering analogy and parameter inversion, and the parameters are obtained. On the basis of the determination, the stability of the slope of ice water accumulation body is evaluated comprehensively by using the limit equilibrium method and the thought of numerical simulation. The research results of this paper supplement the shortage of the physical and mechanical properties of the ice water accumulation in the engineering and academic circles in Linzhi to a certain extent, for the progress of the engineering and the academic. The technical route of this paper is divided into three stages: the first phase is divided into three stages: the first stage is the basic characteristics of the ice water accumulation in the Linzhi area based on the literature and the collection of relevant data, and the field investigation. The test, in situ permeability test and some auxiliary test methods; the second stage is to make the corresponding indoor test with the sample taken in the field, mainly to study the physical and mechanical properties of the ice water accumulation body. The test instruments used this time mainly include the liquid plastic limit joint tester, the multi power dynamoelectric compaction instrument and the demoulding device, and the constant water head permeability test. An instrument, a large three axis shear tester, a small three axis shear tester, and a medium direct shear tester. The third stage is based on the research of the first two stages, and the ice water accumulation constitutive model and the stability analysis of the slope engineering of the ice water accumulation body are analyzed. The following research ideas and methods are used to obtain the following research results: (1) On the basis of the traditional classification method, the comprehensive classification method of the particles composition, cementation degree, permeability and mechanical properties of ice water accumulation body is put forward on the basis of the traditional classification method, based on the field investigation of the ice water accumulation in Linzhi area, the site separation, infiltration and bulk density. The ice water accumulation body is divided into 3 classes and 5 subclasses. (2) the permeability coefficient of the ice water accumulation body is generally I * 10~ (-3) cm/s, which belongs to medium permeability medium; the stability time of the field penetration test is reached after 2 hours. With the increase of hydraulic gradient, the permeability velocity of the sample is approximately linear to nonlinear growth. When the outlet flow is water, the Darcy law is almost satisfied, and the Darcy law is not satisfied when the turbidity water is water. (3) the compaction test shows that the dry density of the sample increases first with the increase of the water content. The maximum water cut and maximum dry density have the obvious peak value, that is, the dry density of the sample with the same water content increases with the increase of the stone content; the optimal water content increases with the decrease of the stone content; the stone content 40% can be used as a demarcation point for the compaction test of the ice water accumulation body. (4) the indoor large three axis The compression test shows that the cohesion of the ice water accumulation increases first and then decreases with the increase of water content, and has a obvious peak point, and can be fitted with the corresponding polynomial. The internal friction angle decreases with the increase of water content. When the water content is 5.07%~7.84%, the amplitude of the internal friction angle is less, and the curve is less. The line basically tends to be slow basically. (5) the indoor small three axis compression test shows that the temperature of the ice water accumulation body is in the process of -10 C ~50 C, with the increase of temperature, the cohesive force increases first and then tends to decrease and tends to be stable, and the maximum value appears at 0. (6) under the condition of low confining pressure, the constitutive relation of the ice water accumulation body does not conform to the Duncan tensioned model. On the basis of the Duncan Zhang Bengou model, the shear modulus and the tangent Poisson's ratio are corrected with consideration of strain softening and expansion, and the correctness of the modified model is verified. (7) the evaluation of the physical and mechanical parameters obtained by various tests is used. The comprehensive stability evaluation of an ice water accumulation body slope is carried out in the area. The numerical simulation software is used to analyze the accumulation form of the slope after the failure of the slope. At the same time, the applicability of the particle flow program PFC~ (3D) to the numerical simulation of the accumulation form of the granular media is verified. The results of the study on the physical and mechanical properties of the ice water accumulation in Linzhi area are studied in this paper. It is consistent with the general results of previous studies, and on the basis of previous research results, the deficiency of ice water accumulation in field identification and remote sensing interpretation, engineering classification, engineering characteristics, temperature and size effects is supplemented. This study is mainly aimed at Linzhi area and only provides a phase for the study of ice water accumulation in other areas. According to the study of the constitutive model of the ice water accumulation body, this paper only makes the model correction analysis under the strain softening condition, and there may be many shortcomings in the present situation, which provides a research direction for the scholars interested in the research of the ice water accumulation body in the later period.

【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642

【参考文献】