高温作用后的北山花岗岩时效变形特征研究  

Time-dependent deformation characteristics of thermally-damaged Beishan granite

作　　者：罗星 杨兴国[1,2] 鲁功达 Luo Xing;Yang Xingguo;Lu Gongda(State Key Laboratory of Hydraulics and Mountain River Engineering,Sichuan University,Chengdu 610065,China;College of Water Resource and Hydropower,Sichuan University,Chengdu 610065,China;State Key Laboratory of Geohazard Prevention and Geoenvironment Protection,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]四川大学水力学与山区河流开发保护国家重点实验室,四川成都610065 [2]四川大学水利水电学院,四川成都610065 [3]成都理工大学地质灾害防治与地质环境保护国家重点实验室,四川成都610059

出　　处：《吉林水利》2024年第3期1-7,共7页Jilin Water Resources

基　　金：国家自然科学基金青年科学基金项目(11902210);地质灾害防治与环境保护国家重点实验室开放基金项目(SKLGP2023K012)。

摘　　要：以甘肃高放废物重点预选场址的北山花岗岩为研究对象,开展不同热损伤和围压条件下的三轴分级蠕变试验,分析热力耦合作用下的北山花岗岩蠕变变形机理。试验结果表明,在单轴条件下,北山花岗岩的微裂纹密度随热处理温度升高而逐渐增加,进而导致轴向峰值应变持续增大。150℃和300℃温度荷载造成的轻微热开裂引发了裂纹尖端钝化,从而增强了热损伤花岗岩的长期强度;当热处理温度达到600℃后,石英相变产生的差异性热膨胀导致北山花岗岩的热裂纹密度显著增加,进而造成长期强度急剧降低。相比之下,在5 MPa和25 MPa围压的三轴蠕变试验中,静水压力能够愈合较低温度荷载造成的热开裂,使150℃和300℃热损伤花岗岩的轴向峰值变形和长期强度恢复至无损岩石水平。然而,上述静水压力未能完全愈合600℃热处理温度造成的热开裂,热损伤花岗岩的残余微裂纹导致轴向峰值应变增大,并造成了裂纹尖端的钝化效应,最终导致北山花岗岩的长期强度增大。A series of triaxial creep tests have been carried out at different confining pressures over thermallystressed Beishan granite which is sourced from the high-level radioactive waste pre-selected site in Gansu.These experiments aim to investigate the creep deformation mechanism while considering the interplay between thermal loading and hydrostatic pressure.The experimental results indicate that the density of micro-cracks in Beishan granite gradually increases at higher treatment temperatures under unconfined conditions,leading to a continuous rise in axial peak strain.However,thermal cracking of thermally damaged granite at 150℃and 300°C facilitate effective blunting of subcritical crack propagation,mildly enhancing the unconfined long-term strength.Nevertheless,when the treatment temperature is elevated further to 600°C,quartz phase transition significantly increases the density of thermal cracks in Beishan granite,resulting in a sharp decrease in unconfined long-term strength.In contrast,upon confinement application at 5 and 25 MPa,the thermal cracking caused by temperatures of 150℃and 300°C has been eradicated almost completely by the hydrostatic pressure,such that the resulting axial peak deformation and triaxial long-term strength have restored nominally to undamaged granite.However,lower hydrostatic pressure is insufficient for closing the pervasive micro-cracks at 600°C,such that the residual thermal cracks not only lead to an increase in axial peak strain but also trigger a redistribution of geometric morphology and distribution characteristics of grains,inducing crack tip blunting effects.that eventually resulted in enhancement of the triaxial long-term strength of Beishan granite.

关 键 词：北山花岗岩 热损伤 围压 蠕变试验 长期强度 

分 类 号：P642.3[天文地球—工程地质学]