高温作用后2种层理砂岩的动态力学试验及细观分析

为研究层理岩石的动态力学和细观结构方面的各向异性特征,利用大直径(?100 mm)分离式霍普金森压杆(SHPB)系统,进行高温作用后层理砂岩的动态压缩试验,而后对试件破坏断口进行SEM电镜扫描试验,分析其断口形貌特征与能耗规律,并对提取出的微裂缝网络进行数值分析。试验结果表明:高温作用后各向异性砂岩的动态力学性能受冲击弹速、温度效应、层理各向异性的共同影响,随着冲击弹速的增加,砂岩的峰值强度逐渐增加,峰值应变逐渐增大,变形模量也逐渐增加;随着温度的升高,砂岩的峰值强度逐渐减小,峰值应变逐渐增大,而变形模量逐渐减小;平行层理砂岩的峰值强度、峰值应变和变形模量普遍高于垂直层理岩样,整体性更好。层理砂岩在高应变率下破坏的断口表面比在低应变率下整体度差,形貌更加粗糙。经历温度不大于400℃时,断面以沿晶破坏和穿晶破坏为主,表现为脆性断裂;经历温度为800℃时,除前2种断裂模式外,断面局部还出现塑性破坏和韧性破坏特征。砂岩在高应变率下破坏时能耗普遍高于低应变率破坏。断口裂隙的数量、裂隙的面积、裂隙的形状三者均存在明显的各向异性差异,水平层理的裂隙数量普遍高于垂直层理;水平层理岩样的微观裂隙率曲线低于垂直层理岩样;垂直层理的裂隙形状普遍比水平层理规则。高温处理后岩样动态破坏断口的裂隙形态趋于规则。

Dynamic mechanical behavior and mesoscopic analysis of two layered sandstone after high temperature

In order to study the anisotropic characteristics of layered sandstone in dynamic and meso-structure,dynamic compression of layered sandstone after high-temperature heating was tested by large-diameter (?100 mm) SHPB. Then the fracture surfaces were tested by the scanning electron micro-scope (SEM) so as to analyze the features of fracture morphology as well as the law of energy consumption and to conduct the numerical analysis of the extracted micro-crack network. According to the test results,the dynamic mechanical properties of anisotropic sandstone after high temperature are affected by the velocity of impact bullet,temperature effects and bedding anisotropy. As the velocity of impact bullet rises,the peak intensity of sandstone increases,peak strain increases,and variable model increases. As temperature rises,the peak intensity of sandstone decreases,peak strain increases,while variable model decreases.Parallel layered sandstone shows a better integration than vertical samples in terms of peak intensity,peak strainand variable model. Fractures under high strain rates show a worse integration than the ones under low strain rates,with a rougher morphology. With a temperature under 400 ℃,the fractures mainly consist of inter-granular fracture and trans-granular fracture,presenting brittle fracture. With a temperature of 800 ℃,fractures partially present plastic fracture and ductile fracture,apart from the two former modes. The energy consumption of broken sandstone is higher under high strain rates than that under low strain rates. There is obvious anisotropy among numbers,areas and shapes of fractures. In general,the fracture number in horizontal bedding samples is more than that in vertical bedding samples. The micro-fracture rate curve of horizontal bedding samples is lower than that in vertical bedding samples. Fracture shapes in vertical bedding samples are generally more regular than those in horizontal bedding samples. Fracture shapes of dynamic broken samples after high temperature tend to be regular.