软煤样断裂韧性加载速率效应实验研究

Experimental study on loading rate effect for fracture toughness of soft coal sample

为探究加载速率对软煤样Ⅰ型断裂韧性的影响,对取自云南老厂的煤样开展压入硬度实验及不同加载速率条件下的断裂韧性实验,分析加载速率及割理角度对软煤样断裂特性的影响。结果表明:实验老厂煤岩压入硬度分布在51.84~125.03 MPa之间,按压入硬度划分属于软岩类别;实验岩样Ⅰ型断裂韧性分布在0.0099~0.2082 MPa·mm^(0.5)之间,平均值为0.0965 MPa·mm^(0.5);在0.2~1.1 mm/min的位移加载速率范围内,实验软煤岩Ⅰ型断裂韧性值随加载速率的增大呈现先增大后降低的规律,割理角度对软煤岩Ⅰ型断裂韧性有较大影响,Ⅰ型断裂韧性与割理角度的关系呈现为负线性相关性。低加载速率条件下,软煤岩表现为韧性断裂,高加载速率条件下,软煤岩表现为脆性断裂,加载速率的变化导致软煤岩断裂类型的变化。

In order to explore the influence of loading rate on the mode I fracture toughness of soft coal sample,the coal samples were collected from LC area in Yunnan,and the indentation hardness tests and fracture toughness tests under different loading rates were carried out.The influence of loading rate and cleat angle on the fracture characteristics of soft coal samples were analyzed.The results showed that the indentation hardness of tested coal rock in LC area was distributed from 51.84 MPa to 125.03 MPa,which belonged to the category of soft rock according to the classification of indentation hardness.The mode I fracture toughness of tests coal samples was distributed from 0.0099 MPa·mm^(0.5)to 0.2082 MPa·mm 0.5,with an average value of 0.0965 MPa·mm^(0.5).In the displacement loading rate range of 0.2 mm·min^(-1)~1.1 mm·min^(-1),with the increase of loading rate,the mode I fracture toughness of tested soft coal rock increased firstly and then decreased.The cleat angle had a great influence on the mode I fracture toughness of tested soft coal rock,and the relationship between mode I fracture toughness and cleat angle presented a negative linear correlation.Under the condition of low loading rate,the fracture type of soft coal rock was ductile fracture,while under the condition of high loading rate,the fracture type of soft coal rock was brittle fracture,and the change of loading rate led to the change of the fracture type of soft coal rock.