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Fracture Mechanisms of rock specimen under tensile stress and heat condition by micromechanics test

岩石试件在拉应力和热条件下的断裂机制的微观力学试验

基本信息

批准号：
17560721
负责人：
ITAKURA Ken-ichi
金额：
$ 2.18万
依托单位：
Muroran Institute of Technology
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 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17560721/
关键词：
Micromechanics Test Thermal Stress Rock Fracture Mechanism Acoustic Emission AE Fracture Simulation Discrete Element Method Finite Element Method DEM FEM

项目摘要

Micromechanical tests, loading tests for 114 small granite specimens (about 5×7×1 mm), were carried out using a microscope under tensile stress and heat conditions. In this study, tensile loading tests were conducted at room temperature and at 50, 100 and 200°C. Factors influencing strength were considered. Furthermore, acoustic emissions (Aes) were monitored during loading. Finite element method(FEM) simulations, including those of thermal stress, were conducted.The following results were obtained :1. For the temperature at 50, 100 and 200°C, the tensile strength became lower than that at room temperature because of the influence of thermal stress. However, for specimens including pre-existing cracks vertical to the loading axis, results showed that the number of pre-existing cracks dominated the deterioration of strength more than the thermal stress condition.2. Results of FEM simulation with thermal conditions demonstrated that the stress concentration occurred at the complex area of the black mica boundary. This result confirms the laboratory tests.3. Many AE events were detected in specimens during the loading process. These AE events were generated not only from tensile cracking but also from shear sliding of cracks.The results obtained in this study demonstrate that the tensile fracture mechanism of granite specimen under heat condition must be considered separately for specimens with and without dominant pre-existing cracks vertical to the loading axis.In the former specimen, a pre-existing crack leads to rupture of the specimen with less influence of thermal stress. In the latter specimen, shear sliding might have developed along the cracks parallel to the loading axis before rupture. At that moment, an AE was generated with shear sliding of cracks. Moreover, this shear sliding can occur at a structurally complex area.

微观力学测试是在拉应力和热条件下使用显微镜对114个小型花岗岩样本（约5×7×1毫米）进行加载测试。在这项研究中，拉伸载荷测试在室温以及50、100和200°C下进行。考虑了影响强度的因素。此外，在装载过程中还监测了声发射（Aes）。进行了有限元法（FEM）模拟，包括热应力模拟。得到了以下结果： 1．对于50、100和200℃的温度，由于热应力的影响，拉伸强度变得低于室温下的拉伸强度。然而，对于包含垂直于加载轴的预存裂纹的试件，结果表明，预存裂纹的数量比热应力条件对强度劣化的影响更大。 2．热条件下的有限元模拟结果表明，应力集中发生在黑云母边界的复杂区域。该结果证实了实验室测试。3．在加载过程中在样本中检测到许多AE事件。这些AE事件不仅是由拉伸开裂产生的，而且也是由裂纹的剪切滑动产生的。本研究获得的结果表明，对于具有和不具有垂直于加载轴的主导预存裂纹的试件，必须分别考虑花岗岩试件在热条件下的拉伸断裂机制。在前一种试件中，预存裂纹导致试件破裂，而热应力的影响较小。在后一个样本中，剪切滑动可能在破裂前沿着平行于加载轴的裂纹发展。此时，伴随着裂纹的剪切滑动，产生了AE。此外，这种剪切滑动可能发生在结构复杂的区域。