用短棒试件测试无烟煤准静态断裂韧度试验研究

根据国际岩石力学学会建议采用的岩石断裂韧度测定方法,用短棒试件在Instron 1342型电液伺服控制材料试验机上测定了无烟煤准静态I型断裂韧度,其断裂韧度值在位移速率较低时提高较大,但随位移速率的提高有逐渐趋于稳定的趋势。从载荷-COD曲线图中分析了无烟煤断裂时,载荷出现跳动的原因,根据载荷跳动情况可以确定三角形韧带开始起裂时间。根据计算结果得出:试件加工几何上的误差对无烟煤断裂韧度值影响不大,造成的误差最大只有2.4%;但对弹性模量值的影响较大,造成最大的误差达到13.3%,同时用图解法得到了无烟煤的非线性度大于0.4。

DETERMINING QUASI-STATIC FRACTURE TOUGHNESS OF ANTHRACITE USING SHORT ROD SPECIMEN

With reference to the method suggested by ISRM for determining the fracture toughness of rock,quasi-static fracture toughness of anthracite has been measured on the Instron 1342 electro-hydraulic servo controlling material testing machine for the first time using short rod specimens.The fracture toughness value increases fast when displacement rate is lower,but trends to be steady when the rate is higher.The reason for load jump when specimen is fractured has been analyzed on the basis of P-COD curves,and the time when the triangular ligament starts fracturing can be known according to load jump.The result indicates that the influence of geometrical error on the fracture toughness values of anthracite is small and the error is less than 2.4%;but the influence of geometrical error on the elastic modulus is large and the error reaches to 13.3%.Meanwhile,the degree of non-linearity of anthracite has been evaluated according to the graphical construction method,and it is larger than 0.4.