摘要
为研究地应力条件下岩石受季节性冻融的影响效应,以三峡库区岸坡砂岩为研究对象,设计研制出可对标准试样进行预应力加载的装置,开展了不同预应力水平与冻融循环次数下的砂岩物理特性及力学特性试验,分析了预应力与冻融循环作用下砂岩质量、孔隙率、波速及抗压强度的变化规律,并从孔隙周围应力分布的角度探讨了预应力与冻胀力对岩石力学特性的影响机制。结果表明:砂岩的质量损失率、孔隙增长率及纵波波速衰减率与冻融循环次数呈正比,预应力的施加会显著改善由于冻融循环引起的损伤;冻融作用下砂岩的单轴及三轴抗压强度随预应力的增加先陡增后趋于稳定,施加预应力的砂岩抗冻系数可达到75%以上,0~3 MPa范围的预应力能更为有效地提高砂岩的抗冻性能,围压的存在也可减弱冻融循环对砂岩强度的劣化影响;预应力改变了砂岩内部孔隙的应力分布,使孔隙两侧形成压应力区,可有效抵抗冻胀形成的切向拉应力,抑制了冻融循环对砂岩的损伤。研究成果可深化对冻融循环作用下砂岩损伤劣化规律与机制的认识。
In order to study the effect of seasonal freezing and thawing on rocks under in-situ stress,taking the sandstone on the bank slope of the Three Gorges Reservoir Area as the research object,a device which can carry out prestressed loading on standard samples is designed.The physical and mechanical properties of sandstone under different prestress levels and freeze-thaw cycles are tested.The variation rules of sandstone mass,porosity,wave velocity and compressive strength under prestress and freeze-thaw cycles are analyzed,and the influence mechanism of prestress and frost heaving force on rock mechanical properties is discussed from the perspective of stress distribution around pores.The results show that the mass loss rate,pore growth rate and longitudinal wave velocity attenuation rate of sandstone are directly proportional to the number of freeze-thaw cycles,and the application of prestress will significantly improve the above damage caused by freeze-thaw cycles;The uniaxial and triaxial compressive strength of sandstone under freezing-thawing increases sharply first and then tends to be stable with the increase of prestress.The frost resistance coefficient of sandstone with prestress can reach more than 75%.The prestress in the range of 0~3MPa can improve the frost resistance of sandstone more effectively,and the existence of Confining pressure can also weaken the deterioration effect of the freeze-thaw cycle on sandstone strength;Prestress changes the stress distribution of the pores in the sandstone and forms a compressive stress zone on both sides of the pores,which can effectively resist the tangential tensile stress formed by frost heave and inhibit the damage of freeze-thaw cycle to the sandstone.The research results can deepen the understanding of the law and mechanism of sandstone damage and deterioration under freeze-thaw cycles,and provide basis for rock mass engineering construction in cold regions.
作者
史为政
段志
许晓亮
黄天柱
龚家伟
Shi Weizheng;Duan zhi;Xu Xiaoliang;Huang Tianzhu;Gong Jiawei(Key Laboratory of Geological Hazards on Three Gorges Reservoir Area,Yichang,Hubei 443002,P.R.China;College of Civil Engineering&Architecture,China Three Gorges University,Yichang,Hubei 443002,P.R.China;China Highway Engineering Consulting Corporation,Beijing 100089,P.R.China;Guosen Securities Co.,Ltd.,Shenzhen Hongling Branch,Shenzhen,Guangdong 518000,P.R.China)
出处
《地下空间与工程学报》
CSCD
北大核心
2023年第3期815-823,832,共10页
Chinese Journal of Underground Space and Engineering
基金
国家自然科学基金(51809151)
水利部水库大坝安全重点实验室开放基金(YK321012)
湖北省自然科学基金创新群体项目(2020CFA049)。
关键词
砂岩
冻融循环
预应力
力学特性
物理特性
损伤机制
sandstone
freeze-thaw cycle
prestress
mechanical properties
physical characteristics
damage mechanism
