【摘要】 由于原状冻土处于自然状态下,其本构关系及水分、温度的分布符合实际状态,而且其实际破坏形式往往是非线性的剪切破坏,所以论文采用了非线性冻土断裂实验模型,对自然状态下的原状冻土进行了断裂破坏实验,着重对Ⅱ型断裂(剪切)破坏的四点弯曲直裂纹试样进行了实验研究.实验过程中改造了四点弯曲实验台,采用着色法测量预制裂纹尺寸.实验原理采用基于能量平衡的方法,利用数据采集系统分别测出了原状冻土四点弯曲试样加力点处位移与力的关系曲线以及相应的非线性参数,推导出裂纹扩展非线性能量释放率计算公式,当试样达到承载极限状况时测试出Ⅱ型断裂试样非线性断裂韧度.同时,提出了修正因子计算非线性断裂韧度的方法,将能量方法测试结果与修正因子方法结果进行了对比,二者基本是一致的.以上提出的冻土Ⅱ型断裂非线性断裂韧度测试方法,及获得的非线性断裂韧度测试结果,为非线性理论研究和工程应用提供了依据.更多还原

【Abstract】 Since the original state frozen soil is under a natural condition,it’s constitutive relation、water and temperature distribution are near the reality,and it’s failure is always the nonlinear shear failure,so the nonlinear fracture experimental model to research the original state frozen soil fracture failure experiment was presented in this paper,the four-point banding experiment were researched especially for the type Ⅱ fracture(shear) failure.In the process of experiment,the four-point banding experiment stand is improved,and a new way to prepare initial cracks and measure cracks by the dye penetrant technique is also provided.Base on the theory of energy balance and the data of selecting form the experimental equipment using the relation curve of loading vs.displacement(at the load point) and parameters of nonlinear fracture,the formula of nonlinear fracture energy release rate is given.When the loading get to the maximum value and the specimen is near to failure,the nonlinear fracture toughness can be work out.And then,another method of correction factor for calculation of nonlinear fracture toughness was presented.Through the comparison,the result of two methods is accord well.Both the experiment method of testing the nonlinear fracture toughness of the type Ⅱmodel and the experimental data of the nonlinear fracture toughness for the original state frozen soil in this paper can offer the basis for the frozen soil nonlinear fracture theory research and engineering application.更多还原