煤矿砂岩双向加载下力学特性及破坏特征实验研究

随着开采深度的不断加深,开采活动在地下开挖体周边引起的压缩应力可能足以引起岩爆甚至作业人员伤害等灾害.地下开挖体周边岩石处于平面应力或平面压缩状态.为了研究地质材料的双轴强度.对从煤矿井下采出的100 mm立方体灰砂岩试件的双轴力学性能和强度进行了实验研究.双轴压缩的加载速度为1 MPa/s.对砂岩立方体试件和标准试件的单轴强度进行了测试并与双轴试验结果进行比较.实验采用了2种加载路径:一种是保持双向受力相等直至破坏;另一种是保持双向受力相等直至单轴抗压强度的1/2,然后保持约束荷载恒定,增加另一荷载直至破坏.给出了试验结果和所观察到的现象,探讨了砂岩双轴加载的破坏机理.试验结果表明,随着约束荷载的增加,岩石双轴强度显著增加,试件的破坏通常由加载初期开始,并持续地沿自由面片落,最终产生加载平面外的剪切破坏,同时伴随轻微的断裂声响.

Experimental investigation on mechanical behaviour and failure characteristics of biaxially loaded coalmine sandstone

As mines continue to reach deeper deposits,mining-induced stresses at mine opening boundaries can be significant enough to cause concern for strainburst occurrence and personnel safety.The state of stress at the boundary of mine openings is plane stress.For investigating the biaxial strength of geomaterials,a series of tests on 100 mm cube gray sandstone samples,which obtained from an underground coal mining operation in China has been carried out for the purpose of determining the biaxial strength characteristics of the sandstone rock.Tests were preformed under biaxial loading condition and the samples were subjected to a loading rate of 1 MPa/s.Uniaxial tests were also performed on cubic and traditional cylindrical samples, and the results were compared.Two loading paths were adopted.First,equal loading in both directions until failure.Second,equal loading in both directions until 50% of the uniaxial compressive strength is attained, followed by loading in one direction to failure while holding the other constant.Test results and observed phenomena are repIorted, and failure mechanisms due to biaxial loading are discussed.It is observed that the biaxial strength is significantly increased with lateral confinement.The failure mechanism is generally initiated by rock spalling at the free faces of the rock sample in an early stage of loading and progresses with loading.The ultimate failure occurs in the form of all out-of-plane shear failure mechanism with slight violent nature.