【作者】 徐光苗；

【导师】 刘泉声；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土工程， 2006， 博士

【摘要】 我国是寒区面积分布最多的国家之一,永久性冻土和季节性冻土面积约占全国陆地总面积的75%。随着我国在寒区建设工程日益增多,出现了大量的冻岩问题,而至今人们对冻岩问题研究非常不足。本论文针对寒区日益增长的工程需要,将寒区冻岩问题作为一门新的研究方向单独提出来。围绕冻岩问题,论文以实验研究为基础,采用理论分析和数值计算相结合的方法,系统地研究岩石在低温、冻融循环条件下的力学、热学特性,并根据实验结果建立岩石的宏观冻融损伤本构关系,最终以寒区实际大型岩体工程——青藏铁路昆仑山隧道为背景,建立相应的温度-渗流、温度-渗流-应力多场耦合数学模型,采用有限元方法,进行寒区冻岩工程实例计算分析。概况来讲,本论文的主要研究内容如下:从工程现场取两种典型岩石(红砂岩和页岩),加工成标准试件(φ50mm×100mm),进行常温(20℃)及不同冻结温度和不同含水状态(完全饱和和干燥)下单轴压缩实验和三轴压缩试验。单轴压缩试验的冻结温度分别为0℃,-5℃,-10℃,-20℃,三轴压缩试验的冻结温度为-5℃和-10℃。分析了单轴压缩和三轴压缩试验的试件变形破坏规律,应力-应变关系,以及饱和和干燥条件下单轴抗压强度、弹性模量,三轴抗压强度、三轴剪切强度参数c,?值随温度的变化关系,并给出了相应的拟合关系表达式。最后还进行了两种岩石在不同低温、以及饱和和干燥两种状态下的超声波波速测试和热参数测试,并给出了波速、导热系数与温度的关系。对红砂岩和页岩进行了开放饱水状态下冻融循环试验,一次冻融循环试验包括在-20℃低温冷柜中冻结12h和在常温20℃纯水中融化12h。分析了两种岩石的冻融损伤劣化及冻融破坏行为,提出了红砂岩和页岩分别代表的两种冻融损伤劣化模式:片落模式和裂纹模式;并对经历不同冻融次数(0,5,10,20,30次)后的岩样进行单轴压缩试验,记录了岩石冻融循环后变形、强度变化规律,分析了这两种岩石的冻融耐久性,并对试验结果进行了数据拟合,得出了两种岩石在饱水状态下单轴抗压强度、弹性模量与冻融次数的拟合关系表达式。在此基础上,并结合已有的研究资料,对岩石的冻融损伤劣化机理及其影响因素进行了深入的分析,指出了各种因素的影响范围。以岩石冻融循环后的单轴压缩试验结果为依据,从宏观损伤力学理论出发,将岩石的损伤分为两个阶段,第一阶段为冻融引起的损伤,第二阶段为冻融和单轴压缩引起的更多还原

【Abstract】 China is one of the biggest countries which have large area of cold regions, the area of permafrost and seasonally cold regions account approximately 75% of the total land area. With the increase of projects constructing in cold regions, many engineering problems involving frozen rock occur. However, the research work on frozen rock is very scarce since now. To deal with the engineering demands for solving problems occurred in cold regions, this paper bring forward a new research direction as to study the problems on frozen rock in cold regions. Based on experiment research, and combining theory with numerical simulation, this paper studies systematically the behaviors of mechanics and thermodynamics under conditions of low temperature and freeze-thaw firstly. Then the macro constitutive equation for damage rock due to freeze-thaw cycling is established according to the testing results. Lastly, on the background of large scale rock engineering in cold regions, e.g. the Kunlun mountain tunnel of Qinghai-Tibetan railway, the mathematical models of temperature-fluid coupling and temperature-fluid-mechanics fully coupling are set up by taking into account the macro constitutive equation for damage rock due to freeze-thaw cycling, and a number numerical simulations are proceeded on frozen rock engineering by adopting finite element method. Synoptically, the main research works are introduced in the dissertation as following:Two typical rocks that are red sandstone and shale were obtained from engineering sites, and they were prepared as standard specimens of 50mm in diameter and 100mm in length. The uniaxial compression tests and triaxial compression tests were conducted on the two types of rock at different frozen temperature and different moisture state(absolute saturated and dry). The test temperature of uniaxial compression test is +20℃,0℃,-5℃,-10℃,-20℃,respectively, and that of triaxial compression test is +20℃,-5℃,-10℃. The deformation and failure of rock, the relationship between stress and strain, and the depending on temperature of the uniaxial compression strength, Young’s modulus, triaxial compression strength, and the shear strength parameters(cohesion c and inner friction angle ?) under uniaxial and triaxial compressive test are analyzed, the relatively fitting expressions are formulated. Furthermore, the ultrasonic tests and thermal tests were performed at different low temperatures and different moisture states on the two types of rock as to study the P-wave velocity and thermal parameters changing with different temperatures.The freezing and thawing tests were conducted at opening saturating conditions on red sandstone and shale, one cycle of freeze-thaw test including 12 hours freezing at -20℃in freezer chamber and 12 hours thawing at 20℃in distilled water. Based on the freeze-thaw tests, the damage and failure due freezing and thawing are analyzed, and two deterioration modes, i.e. scaling mode for red sandstone and fracturing mode for shale, are found. The uniaxial compression tests are also conducted on the two types of rock subjected to different freeze-thaw cycles (0, 5, 10, 20, 30 cycles) at room temperature(20℃). The deformation and compression strength of rocks varied with different cycles of freeze-thaw are recorded, and the resistance to freeze-thaw of the two types of rock are analyzed. The relations of uniaxial compression strength and elastic modulus and numbers of freeze-thaw cycle are formulated according to the test results, respectively. On the basis of the test results and pre-existed research works, the mechanism and influence factors of rock deterioration due to freeze-thaw更多还原