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Strength and deformation of rocks under freezing condition and their fracture mechanism

岩石冻结条件下的强度、变形及其断裂机制

基本信息

批准号：
17560720
负责人：
KODAMA Jun-Ichi
金额：
$ 2.27万
依托单位：
Hokkaido University (2006-2007)Muroran Institute of Technology (2005)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

Uniaxial compression tests and Brazilian tests were carried out to clarify mechanical behaviors and fracture mechanism of rocks under freezing condition. Effect of water content on strength and deformation was investigated and fracture process of the frozen rock was elucidated based on deformation behaviors and AE activities. Effects of temperature and loading rate on strength and deformation were also examined. Experimental results were discussed on the basis of an inclusion model considering mechanical role of ice within the rock. Main results are as follows.(1) At dry condition, micro-fracturing increased exponentially just before strength failure and brittle rupture was observed. At water saturated condition, specimen deformed elastically up to high stress level and occurrence of micro-fracture increased at a constant rate prior to strength failure.(2) Strength, critical strain and Poisson's ratio increased with increase in water content at -20 degrees C. Strength increased, but critical strain, Young's modulus and Poisson's ratio were not changed with rise in temperature between -5 degree C and -20 degree C. Strength increased with loading rate, at -20 degree C, but critical strain, Young's modulus and Poisson's ratio were not affected by loading rate.(3) Based on the inclusion mode], it was found that stress concentration near the tip of crack is reduced if Young's modulus of ice increases Young's modulus of ice was cleared to increase with drop in temperature or increase in loading rate through previous studies. Strength of frozen rock can be estimated to increases with drop in temperature or increase in loading rate because stress at fracture initiation increase with them.

通过单轴压缩试验和巴西试验研究了冻结条件下岩石的力学行为和断裂机理。研究了含水量对冻结岩石强度和变形的影响，并根据冻结岩石的变形行为和声发射活动，阐明了冻结岩石的破裂过程。温度和加载速率对强度和变形的影响也进行了研究。根据考虑冰在岩石中的力学作用的夹杂物模型对实验结果进行了讨论。主要结果如下。(1)在干燥条件下，微破裂指数增加之前，强度破坏和脆性断裂观察。在水饱和条件下，试样的弹性变形达到高应力水平，微破裂的发生以恒定的速率增加之前的强度破坏。(2)在-20 ℃时，强度、临界应变和泊松比随含水量的增加而增加。在-5 ℃ ~-20 ℃的温度范围内，随着温度的升高，强度增加，但临界应变、杨氏模量和泊松比没有变化。在-20 ℃时，强度随加载速率的增加而增加，但临界应变、杨氏模量和泊松比不受加载速率的影响。(3)根据夹杂模型，发现随着冰的杨氏模量的增加，裂纹尖端附近的应力集中减小。通过以往的研究，发现冰的杨氏模量随着温度的降低或加载速率的增加而增加。冻结岩石的强度可以估计为随着温度的降低或加载速率的增加而增加，因为断裂起始时的应力随着温度的降低或加载速率的增加而增加。