不同应力条件下裂隙岩体广义流变特性及稳定性研究

Generalized rheological behaviors and stability of fractured rock mass under different stress conditions

裂隙岩体开挖后形成扰动区,随着时间的延长,应力和应变同时变化的这种流变现象确实存在,在刚性支护后,随着时间的延长,强度会恢复,且在强度恢复过程中应力和应变又同时变化,这种流变现象用一般的蠕变和应力松弛很难解释清楚,通过广义流变来研究不良地质裂隙岩体的稳定性和长期强度非常重要。首先,对广义流变特征、力学机制进行了总结分析,将隧道开挖扰动区分为开挖破碎区(Excavation Fracture Zone,EFZ)、开挖损伤区(Excavation Damaged Zone,EDZ)和原岩弹性区(Inner Elastic Zone,IEZ),将峰后卸荷损伤区(Unloading Damage Zone,UDZ)和塑性流变区(Plastic Disturbed Zone,PDZ)合并为广义流变损伤区(Generalized Relaxation Disturbed Zone,GRDZ),重点探讨了不同裂隙岩体开挖扰动区岩石广义流变的工程物理意义;然后,开展了不同条件下的广义流变试验,得到裂隙岩体开挖扰动区岩石的广义流变特性;对比分析了单轴压缩、单轴拉伸和三轴压缩条件下广义流变特征的相似性和差异性,得到广义流变等时线近似于全应力应变曲线向内的收缩线;最后,建立了可变模量本构方程,得到蠕变破坏寿命公式,根据广义流变曲线和开挖扰动区围岩应力、应变曲线的关系可知,流变破坏主要发生在广义流变区域的I区和II区的上半部分。此成果对分析裂隙岩体围岩稳定性、预测不良地质公路隧道工程寿命等具有应用价值。

After the excavation of the fractured rock mass,the disturbed area is formed,with the lapse of time.The fractured rock mass is subjected to accompany both stress and strain change,the strength recovers with the increase of time after the rigid support,and there accompany both stress and strain change in the process of strength recovery.It is very hard that this phenomenon is thoroughly explained by pure creep and relaxation,which has an important impact on the study of longterm stability.We use the generalized rheological theory to investigate the stability and long-strength of fractured rock mass and it is very potential for unfavorable geology.The study summarizes the rheology properties and mechanics mechanism of generalized rheology.The excavation disturbance in tunnels can be divided into Excavation Fracture Zone(EFZ),Excavation Damage Zone(EDZ),and Inner Elastic Zone(IEZ).In this paper,Unloading Damage Zone(UDZ)and Plastic Disturbed Zone(PDZ)are combined into a Generalized Rheological Damage Zone(GRDZ).This research focuses on the engineering significance of generalized rheology.Generalized relaxation tests under different loading conditions are carried out.Experiment results indicate that generalized rheological properties of fractured rock mass disturbed area are obtained.And then,the similarity and diversity of generalized relaxation under uniaxial compression,uniaxial tension,and triaxial compression are investigated,and the results indicate that the isochronous curves of generalized relaxation seem to shrink in front of all stress-strain curves.Finally,the variable-compliance constitutive equation is established and the formula of creep failure life is obtained to predict the failure life of surrounding rock in the disturbed zone for fractured rock mass excavation.According to the relationship between the generalized rheological curve and the stress-strain curve of surrounding rock,rheological failure can occur in region-I and the upper part of region-II.In a word,these results have important application value to analyze the stability of fractured rock mass and predict the failure life of unfavorable geology road tunnels.