摘要
以寒区隧道为工程背景研究在冻融循环作用下围岩内Ⅰ型裂纹的动态起裂特性演化规律,采用隧道模型试件作为研究对象,开展冻融循环试验与大尺度落锤冲击试验,得到岩石试件经历不同冻融循环次数后的相关力学参数,并在裂纹尖端粘贴裂纹扩展计(crack propagation gauge,CPG)测量预制裂纹的动态起裂时间。采用有限元软件建立相应的数值模型计算裂纹尖端的动态应力强度因子,采用试验-数值法计算动态起裂韧度,随后采用电镜对冻融循环后的试样进行扫描,研究冻融循环对岩石材料的细观损伤机制。研究结果表明:随着冻融循环次数的增加,岩石材料的纵波、横波波速与弹性模量逐渐减小,而泊松比逐渐增大;砂岩材料的动态起裂韧度随着冻融循环次数的增加逐渐减小,表征线性反比例的特性;材料内部的胶结物质会由于冻融循环的影响而流失,材料的孔隙和裂纹也随着冻融循环次数的增加而变多变大。
In order to investigate the dynamic initiation and evolution of modeⅠcrack in surrounding rock under the action of freeze-thaw cycle,taking a cold area tunnel as the engineering background,the freeze-thaw cycle test and large-scale drop weight test were carried out by using tunnel model specimens that were made of green sandstone in Sichuan province.The dynamic mechanical characteristics of specimens after different freeze-thaw cycles were measured and discussed.The elastic modulus and Poisson’s ratio of the specimens were calculated by longitudinal wave velocity,shear wave velocity.The dynamic strain gauges were glued at the incident plate and transmitted plate to collect voltage signals.The voltage signal was applied to calculate the curves of dynamic loading versus time recorded from the incident plate and transmission plate.Crack initiation time was determined by using a crack propagation gauge(CPG)measuring system.A traditional finite element method code was applied to establish some numerical models to calculate the curves of dynamic stress intensity factor under impact loads.The experimental-numerical method was used to determine dynamic fracture initiation toughness according to crack initiation time.A scanning electron microscope(SEM)was applied to analyze the micro-structure of sandstone material after different freeze-thaw cycles,and the mesoscopic damage mechanism of rock materials was obtained.The test results show that the longitudinal wave velocity,shear wave velocity and elastic modulus of sandstone gradually decrease with the number of freeze-thaw cycles,while Poisson’s ratio increases with the number of freeze-thaw cycles.The crack initiation time and dynamic initiation toughness of rock material decrease with the number of the freeze-thaw cycles.The cement material inside the rock will loss due to the effect of freeze-thaw cycles,and the pores and micro-cracks of the sandstone also increase with the number of freeze-thaw cycles.
作者
姜亚成
周磊
朱哲明
李剑飞
牛草原
应鹏
JIANG Yacheng;ZHOU Lei;ZHU Zheming;LI Jianfei;NIU Caoyuan;YING Peng(College of Architecture and Environment,Sichuan University,Chengdu 610065,Sichuan,China;MOE Key Laboratory of Deep Underground Science and Engineering,Sichuan University,Chengdu 610065,Sichuan,China)
出处
《爆炸与冲击》
EI
CAS
CSCD
北大核心
2021年第4期76-86,共11页
Explosion and Shock Waves
基金
国家自然科学基金(U19A2098,11672194,11702181)
深地科学与工程教育部重点实验室(四川大学)开放基金(DESE202005)。
关键词
冻融循环
隧道模型
动态起裂韧度
细观损伤机制
freeze-thaw cycles
tunnel model
dynamic initiation toughness
mesoscopic damage mechanism
