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采用国际岩石力学学会岩石断裂韧度建议测试方法(ISRM)[1]提出的V形切槽巴西圆盘试样(CCNBD),测试了一种泥质砂岩的I型断裂韧度值,给出了一套试样切割制备方案,从试验现象角度分析了该泥质砂岩的断裂力学特性,讨论了该试样类型的有效尺寸和断裂机制,并指出了该方法的特点和优劣性,得出如下结论:(1)该类岩石试样测得的I型断裂韧度值对CCNBD试样直径尺寸变化具有较大的敏感性,并且直径大于ISRM建议方法中最小有效直径(75mm)的试样测试结果更为稳定;(2)CCNBD试样断裂机制表现为以拉张应力(间接拉伸)作用为主,兼有一定的韧带面内剪切作用的应力状态下I型裂纹扩展模式;(3)V形切槽巴西圆盘方法具有试样加工工艺简单、能承受较大临界载荷、测试的I型断裂韧度值较稳定等优点,但其没有考虑断裂过程区(FPZ)的非线性问题,建议对该方法进行非线性修正图解方案研究,以达到更准确测定岩石断裂韧度的目的。
The I-type fracture toughness values of a shaly sandstone were tested using the V-notch notched Brazilian disk specimen (CCNBD) proposed by the International Society for Rock Mechanics Society’s Rock Failure Toughness Test Method (ISRM) [1] A set of sample cutting preparation scheme is presented. The fracture mechanics characteristics of the shaly sands are analyzed from the experimental point of view. The effective size and fracture mechanism of the sample are discussed. The characteristics and advantages and disadvantages of the method are also pointed out. The conclusions are as follows: (1) The type I fracture toughness values of these rock samples are sensitive to the change of diameter of CCNBD samples, and the diameter is larger than the minimum effective diameter (75mm) of the proposed method of ISRM (2) The fracture mechanism of CCNBD specimen is mainly tensile stress (indirect tensile), and it also has some mode I crack growth mode under the stress state of ligament in-plane shear stress; (3) The V-notch grooved Brazilian disc method has the advantages of simple sample processing technology, large critical load capacity and relatively stable Type I fracture toughness value, but it does not consider the FPZ Linear problems, it is recommended that the method of non-linear correction diagram Research to achieve the object of more accurate determination of the fracture toughness of rock.