SHPB压缩试验中红砂岩的力学与能量耗散特性研究

为了定量描述岩石在动态压缩过程中的耗能能力,采用SHPB装置对圆柱形红砂岩试样进行了单轴动态压缩试验,并采用高速摄像仪记录了试样的破坏过程。试验结果表明:随着入射能的增加,承受冲击加载后的试样呈现出完整、破裂和破碎3种不同状态,试样峰值应力呈现明显的应变率效应。在能耗特性方面,以临界入射能为间隔点,试样耗散能呈现出2个阶段的线性增长规律。当施加的入射能小于临界入射能时,试样在冲击后保持完整状态;当施加的入射能大于临界入射能时,试样在冲击后发生破碎,试样碎片飞出。基于线性耗能规律,分别定义了2个阶段的动态压缩耗能系数。当试样呈现完整阶段时,理想的动态压缩耗能系数为定值。在试样承受冲击后发生破碎阶段,动态压缩耗能系数随着入射能的增加而增加。

Research on Mechanical and Energy Dissipation Characteristics of Red Sandstone in SHPB Compression Test

In underground engineering,rock(body)is damaged or destroyed by impact drilling,blasting,crushing and other dynamic disturbance.In this process,external energy conversion and internal energy consumption are inevitable.Energy dissipation is an important factor that causes rock damage and failure state,so it is of great significance to study the dynamic mechanical properties and failure behavior of rock from the perspective of energy.At present,in the research of rock dynamic characteristics,the commonly used equipment are drop hammer,split Hopkinson pressure bar(SHPB)and light gas gun,among which the SHPB test system is generally used to study the dynamic characteristics of rock under medium and high strain rate(10~10^3 s^-1).In order to quantitatively describe the energy dissipation capacity of rock in the process of dynamic compression,the uniaxial dynamic compression tests of cylindrical red sandstone specimens were carried out with SHPB device,and the failure process of the specimen was recorded by a high-speed camera.The test results show that with the increase of incident energy,the specimen shows three different states:intact,ruptured and broken after the dynamic impact loads,and the peak stress of specimen shows obvious strain rate effect.In addition,the failure mode of specimens is mainly tensile failure.In the aspect of energy consumption,the dissipative energy of the specimen shows a two-stage linear growth rule with the critical incident energy as the interval point.When the incident energy is less than the critical incident energy,the specimen remains intact after impact.When the incident energy is greater than the critical incident energy,the specimen will be broken after impact and the fragments will fly out.Based on the obtained linear energy consumption rule,two stages of dynamic compression energy dissipation coefficient(DCEDC)are defined respectively.When the specimen is in intact state,the ideal DCEDC is a fixed value,for the red sandstone specimen in this paper,this value is 0.19.When the specimen is in the broken state the DCEDC increases with the increasing incident energy and gradually approaches 0.68.