School of Civil Engineering and Architecture,Anhui University of Science & Technology
Beijing Zhongkeli Explosion Technology Engineering Co Ltd

为研究饱水状态和应变率对凝灰岩拉伸力学特性的影响,采用电液伺服压力机及直径50 mm 分离式霍普金森压杆(SHPB)对凝灰岩开展静态和动态巴西圆盘劈裂拉伸试验,利用高速摄像系统获取试件在高应变率下裂纹扩展过程及破碎形态,并结合放大 1 000 倍的电子数码显微镜观测岩石表面及断口处的细观结构。 研究结果表明:试件拉伸强度存在明显的应变率效应,且应变率越大,试件到达峰值应力的时间越短;静载作用下饱水试件抗拉强度均值是干燥试件的88.12% ,0.2,0.3,0.4 MPa 气压作用下,饱水试件拉伸强度分别为干燥试件的 99.89% ,95.25% 和90.52% ,饱水作用对岩体造成劣化,降低其抗拉强度;0.2,0.3,0.4 MPa 气压作用下,饱水试件动态增强因子 (DIF) 均值分别是干燥试件的 1.14,1.08,1.05 倍,由于黏聚力与“stefen” 效应的存在,饱水试件 DIF 高于干燥试件;随着应变率的增大,试件裂纹扩展速度加快,且饱水试件裂纹扩展宽度和速度均高于干燥试件;静载作用下试件呈典型劈裂拉伸破坏形式,动载作用下试件拉伸与剪切破坏共存;凝灰岩自身存在大量原生节理、孔隙等结构薄弱面,在应力波作用下,试件薄弱面处的裂纹发生扩展贯通并最终发生破坏,水的侵蚀作用使饱水试件裂纹扩展程度明显高于干燥试件。

Using an electro-hydraulic servo press and a split Hopkinson pressure bar (SHPB) with a 50mm diameter, static and dynamic Brazilian disc splitting tensile tests were performed on tuff in order tostudy the impact of water saturation and strain rate on the tensile mechanical properties of tuff. The crackpropagation process and fracture morphology of the specimen under high strain rate were obtain by ahigh-speed camera system, and the microstructure of the rock surface and fracture was observed with anelectronic digital microscope with 1 000 times. The results show that there is an obvious strain rate effecton the tensile strength of the specimen; the higher the strain rate, the faster for the specimen to reach thepeak stress. The average tensile strength of the saturated test piece under static load is 88.12% of the drytest piece, and the tensile strength of the saturated test piece under 0.2 MPa,0.3 MPa and 0.4 MPa airpressure is 99.89% , 95.25% and 90.52% of the dry test piece.The saturated action degrades the rockmass and reduces its tensile strength. The average value of the dynamic enhancement factor (DIF) of thesaturated specimen under the pressure of 0.2 MPa, 0.3 MPa and 0.4 MPa is 1.14, 1.08 and 1.05 timesthan that of the dry specimen. Due to the existence of cohesion and “stefen” effect,the DIF of saturatedspecimens is higher than that of dry ones. With the increase of strain rate, the crack propagation speed ofthe specimen increases, and the crack propagation is wider and speed of the saturated specimen is higherthan that of the dry specimen. Under static load, the specimen is in the form of typical split tensile fail-ure, while the specimen is in the form of tensile and shear failure under dynamic load. The tuff itself hasa large number of primary joints, pores and other structural weak surfaces. Under the action of stresswaves, the cracks at the weak surface of the specimen expand and penetrate and eventually cause dam-age. The erosion effect of water makes the crack propagation degree of the saturated specimen signifi-cantly higher than that of the dry specimen.

国家自然科学基金项目(52074009);爆破工程湖北省重点实验室开放基金项目(BL2021-20)

1 试验方案
1.1 试件制备
1.2 试验方案
2 试验结果与分析
2.1 不同应变率下试件应力时程曲线
2.2 不同应变率下试件应力及DIF变化特性
2.3 不同应变率下试件裂纹扩展过程
2.4 不同应变率下试件破碎形态及细观机理分析
3 结 论