冻融环境下红砂岩物理力学特性试验研究

发布时间：2018-03-19 15:06

本文选题：岩石　切入点：冻融循环　出处：《西安科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：我国是世界上寒区面积分布最多的国家之一,永久性和季节性冻土面积约占全国陆地总面积的3/4。随着我国寒区工程建设的日益增多,出现了一系列冻融岩石问题,因此研究岩石在冻融环境下的物理力学特性显得尤为重要。论文针对寒区日益增长的工程需要,以试验研究为基础,系统地研究岩石在冻融循环和围压作用下的物理力学特性;以寒区大型岩体工程为背景,采用有限元方法对隧道围岩进行温度应力耦合数值模拟及分析,并提出相应的冻害防治措施,为寒区岩体工程建设提供一定的理论基础。从现场取回红砂岩岩块,加工成?50mm?100mm的国际标准试件,进行开放饱水状态下的冻融循环试验,观察并记录岩石冻融损伤劣化过程及冻融破坏方式,探讨岩石质量、体积、密度、纵波波速随冻融循环次数的变化规律,分析冻融损伤劣化机理及其影响因素。结果表明:红砂岩的损伤劣化模式可分为颗粒剥落、龟裂、片落及断裂4种模式;随着冻融循环次数的增加,岩石的质量、体积、密度呈先增加后减小的趋势,纵波波速呈现出持续减小的趋势。对经历不同冻融循环次数(0,5,10,20,40次)后的红砂岩试件进行4种围压(0MPa,2MPa,4MPa,6MPa)下的力学特性试验。分析不同冻融条件及不同围压下岩石三轴压缩的应力-应变曲线、抗压强度、极值应变、弹性模量、泊松比、残余强度、内摩擦角、粘聚力等随冻融条件和围压的变化关系。研究表明:红砂岩的抗压强度和极值应变随围压的增大而增大,但随着冻融循环次数的增加,抗压强度逐渐减小,极值应变则逐渐增大;岩石的弹性模量、残余强度随着围压的增大而增大,随着冻融循环次数的增加而减小;泊松比随着围压的增大逐渐减小,随着冻融循环次数的增加而逐渐增大;内摩擦角、粘聚力、抗冻性随冻融循环次数的增加而逐渐减小。以大阪山隧道工程为研究对象,运用有限元方法,对隧道围岩进行温度场与应力场耦合作用下的数值模拟分析。结果表明:随着冻融时间的增加,隧道的最大拉应力逐渐增大,最大压应力逐渐减小;隧道顶部逐渐下沉,隧道底部向上的位移量逐渐增加;冻结圈的厚度逐渐增大,但增大速度随时间的增加逐渐趋缓。
[Abstract]:China is one of the countries with the largest area distribution in cold regions in the world. The area of permanent and seasonal frozen soil accounts for about 3 / 4 of the total land area of China. With the increasing construction of cold region projects in China, a series of frozen and thawed rock problems have appeared. Therefore, it is very important to study the physical and mechanical properties of rock in freeze-thaw environment. According to the increasing engineering needs in cold region, this paper systematically studies the physical and mechanical properties of rock under freeze-thaw cycle and confining pressure. On the background of large rock mass engineering in cold region, finite element method is used to simulate and analyze the temperature and stress coupling of surrounding rock mass of tunnel, and the corresponding measures to prevent and cure freezing damage are put forward. To provide a certain theoretical basis for rock mass engineering construction in cold region. 50mm? A 100mm international standard specimen was tested by freeze-thaw cycle under the condition of open saturated water. The damage and deterioration process of rock freezing and thawing were observed and recorded, and the quality, volume and density of rock were discussed. The variation of longitudinal wave velocity with the number of freeze-thaw cycles is analyzed. The mechanism of damage deterioration and its influencing factors are analyzed. The results show that the damage deterioration modes of red sandstone can be divided into four modes: grain spalling, crack, sheet falling and fracture. With the increase of freeze-thaw cycles, the quality, volume and density of rock increased first and then decreased. The longitudinal wave velocities show a decreasing trend. The mechanical properties of red sandstone specimens with different freezing and thawing cycles were tested under 4 different confining pressures (0 MPa ~ 2 MPa ~ (2) MPa ~ (2) MPa ~ (2) MPa ~ (2)) ~ (6) MPa). The analysis of different freezing and thawing conditions and rock triaxial under different confining pressures was carried out. Compressive stress-strain curves, The relation of compressive strength, extreme strain, elastic modulus, Poisson's ratio, residual strength, angle of internal friction and cohesion with freeze-thaw condition and confining pressure is studied. The results show that the compressive strength and extreme strain of red sandstone increase with the increase of confining pressure. However, with the increase of freeze-thaw cycles, the compressive strength decreases and the extreme strain increases, while the elastic modulus and residual strength increase with the increase of confining pressure, and decrease with the increase of freeze-thaw cycles. Poisson's ratio decreases with the increase of confining pressure and increases with the increase of freeze-thaw cycle times, and the angle of internal friction, cohesion and frost resistance decrease with the increase of freeze-thaw cycle times. The finite element method is used to simulate the tunnel surrounding rock under the coupling of temperature field and stress field. The results show that with the increase of freeze-thaw time, the maximum tensile stress increases and the maximum compressive stress decreases. The top of the tunnel gradually sinks, the displacement of the bottom of the tunnel increases gradually, and the thickness of the freezing circle increases gradually, but the increasing speed gradually slows down with the increase of time.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU45

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