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首页> 外文期刊>Rock Mechanics and Rock Engineering >Experimental Calibration of ISRM Suggested Fracture Toughness Measurement Techniques in Selected Brittle Rocks
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Experimental Calibration of ISRM Suggested Fracture Toughness Measurement Techniques in Selected Brittle Rocks

机译：ISRM建议的脆性岩石断裂韧性测量技术的实验校准

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A wide variety of specimen types and methods are employed in fracture toughness measurement of rocks, which result in scattered values for the same rock type. In order to provide some consistency to the values, the International Society for Rock Mechanics (ISRM) recommended three suggested methods using core based specimens, the Chevron Bend (CB) test, the Short Rod (SR) test and the Cracked Chevron Notch Brazilian Disc (CCNBD) test. This standardization helped obtain more consistent values but still a variation of 20-30 percent was observed in the values of fracture toughness obtained with the CB and SR methods. The values obtained with the CCNBD method were found to be consistently lower (30-50 percent) than those of the other two methods (CB and SR). Many reasons have been offered to explain this deviation. These include size of the specimen, anisotropy of rock, a dimensionless parameter in the fracture toughness calculation equation for the CCNBD test, etc. A comprehensive test program was initiated to identify the cause of these discrepancies between the CB and CCNBD methods. Three brittle rock types were selected for the study and more than 200 tests were conducted to measure the values of fracture toughness. A rigorous statistical analysis was carried out to determine the confidence level and find the significance of the test results. It was found that the CB and CCNBD methods were very comparable provided the correct equation for fracture toughness calculation was used for the CCNBD method and the size of the specimens was selected carefully. The error in the ISRM 1995 formula of fracture toughness for the CCNBD method could be the major factor responsible for the consistently lower values obtained with the method.
机译：在岩石的断裂韧性测量中采用了多种试样类型和方法，这导致了相同岩石类型的离散值。为了提供与值的一致性，国际岩石力学学会（ISRM）建议了三种建议的方法，使用基于岩心的标本，雪佛龙弯曲（CB）测试，短杆（SR）测试和裂纹雪佛龙缺口巴西圆盘（CCNBD）测试。该标准化有助于获得更一致的值，但使用CB和SR方法获得的断裂韧性值仍观察到20％至30％的变化。发现使用CCNBD方法获得的值始终低于其他两种方法（CB和SR）的值（30-50％）。提供了许多原因来解释这种偏离。这些因素包括标本的大小，岩石的各向异性，CCNBD试验的断裂韧性计算方程中的无量纲参数等。启动了一个全面的试验程序来确定CB和CCNBD方法之间这些差异的原因。研究选择了三种脆性岩石类型，并进行了200多次测试以测量断裂韧性值。进行了严格的统计分析，以确定置信度并找到测试结果的重要性。如果CCNBD方法使用正确的断裂韧性计算公式，并且仔细选择了试样的尺寸，则发现CB和CCNBD方法具有可比性。 CCNBD方法的ISRM 1995断裂韧性公式中的错误可能是导致该方法获得的值始终较低的主要原因。

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