高地温隧道注浆节理剪切损伤本构模型研究

Study on Constitutive Model of Shear Damage of Grouting Joint in High Geothermal Tunnels

高地温环境对水泥浆在硬化过程中造成的损伤,直接影响隧道围岩注浆节理的剪切性能和注浆加固的效果。主要考虑高温和法向应力2个影响因素,并采用能反映高地温隧道施工期间温度场真实变化过程的高温变温养护方法,进行浆-岩复合体试件的养护,并开展室内注浆节理直剪试验,由此获得不同初始养护温度和法向应力条件下的注浆节理剪切破坏特征、剪切应力位移曲线等;利用浆-岩界面扫描电镜(SEM)试验,分析高温变温养护对水泥浆微观结构的影响规律;在此基础上,引进统计损伤理论,建立考虑温度损伤的注浆节理剪切本构模型。结果表明:注浆节理剪切破坏模式在初始养护温度40℃时表现为胶结面破坏,60和80℃时表现为混合剪切破坏,且温度越高,水泥浆在破坏面中的占比越高;高温导致水泥浆微观上水化产物搭接不紧密,微孔隙、微裂缝发育,且温度越高,水泥浆微观损伤越严重;初始养护温度与注浆节理峰值剪切强度、剪切刚度呈负相关,与峰值剪切位移呈正相关,初始养护温度与法向应力的叠加效应对注浆节理剪切性能的影响较为明显;考虑温度损伤效应的注浆节理剪切本构模型,与试验结果有较好的吻合度,可为高地温隧道注浆节理剪切问题的相关研究和注浆加固设计提供借鉴和参考。

The damage to cement slurry caused by high ground temperature in the hardening process directly affects the shear performance of grouting joints in tunnel surrounding rock and the effect of grouting reinforcement.The direct shear test of grouting joints was carried out,mainly considering the two influencing factors-high temperature and normal stress.The high-temperature and variable-temperature curing method was used to maintain the grouting-rock composite specimens and to conduct indoor shear test on grouting joints.The shear failure characteristics and shear stress-displacement curves of grouting joints under different initial curing temperatures and normal stress conditions were obtained from the test.The influence of high-temperature and variable-temperature curing on the microstructure of cement slurry was analyzed by the scanning electron microscope(SEM)tests of slurry-rock interface.On this basis,the shear constitutive model of grouting joints considering temperature damage is established by introducing statistical damage theory.The results show that the shear failure mode of grouting joints is the failure of cementation surface at the initial curing temperature of 40°C,and the mixed shear failure at 60°C and 80°C.The higher the temperature,the higher the proportion of cement slurry in the failure surface.High temperature causes loose interconnection of the hydration products of cement slurry and the development of micropores and microcracks.The higher the temperature,the more serious the microscopic damage of cement slurry.The initial curing temperature is negatively correlated with the peak shear strength and shear stiffness of grouting joints,and is positively correlated with the peak shear displacement.The superposition effect of initial curing temperature and normal stress has obvious influence on the shear performance of grouting joints.The shear constitutive model of grouting joints considering the effect of temperature damage is in good agreement with the experimental results,which can provide a reference for relevant research on the shear problem of grouting joints in high geothermal tunnels and the design of grouting reinforcement.