【作者】 张龙；

【导师】 张茹；

【作者基本信息】 四川大学 ， 土木工程， 2022， 博士

【摘要】 我国水电资源主要集中在西部高山峡谷地区,将水电站建筑物布置在极深洞室群常常是经济的、较优的选择。受典型河谷地貌特征和区域强烈“高地应力”、“高渗透压”环境影响,极深洞室围岩力学特性演化规律和长期稳定性是亟需解决的关键科学问题。传统浅部岩石力学难以真实反演不同赋存深度应力环境下水岩耦合作用对岩石力学性质的影响,导致深部岩体工程面临一定的风险性和低效性。本文依托国家自然科学基金委重点基金项目“不同深度岩体工程力学特性与渗流长期稳定性研究（No.U1965203）”,紧密结合工程实践,通过工程踏勘、设备研制、室内试验和程序开发等研究方法,进行了锦屏大理岩原位应力环境不同饱水时间力学特性及水软化机理探索,并开展了基于水软化效应的锦屏地下工程围岩稳定性研究,提出了锦屏地下工程围岩长期稳定性评价方法,丰富了岩石力学的理论和成果。主要研究内容和成果如下:（1）通过现场踏勘获取了锦屏地下工程运营期地质环境多源信息,结合工程踏勘与模糊数学理论进行了地下工程围岩稳定性初判。为全面探明锦屏交通洞及中国锦屏地下实验室D厅在运营期的围岩稳定性状况,开展了两次工程现场全方位勘察。分析并总结了A、B交通洞不同深度岩体工程整体渗流状况及分布特点。以地下水状态、支护方式、断面岩体掉落状况及断面埋深为一级指标,建立了基于模糊数学理论的锦屏交通洞围岩稳定性评价模型。通过层次分析法获取了各评价指标权重,采用最大隶属度原则确定了模糊评判最终结果。对比评价等级,B洞围岩整体稳定性优于A洞,围岩稳定性最差的区段为A34、A36、A39和B45,为研究局部区域围岩长期稳定性奠定了基础。（2）参与了“深部高围压高渗压水岩耦合实验系统”的自主研制,对比研究了锦屏大理岩在原位应力环境和无压环境下水软化效应的差异,推导并验证了锦屏大理岩考虑水软化效应的统计损伤本构模型。参与了“深部高围压高渗压水岩耦合实验系统”的自主研制,开展了锦屏大理岩原位应力环境与无压环境下饱水时长为1 d、23 d、60 d、100 d的水软化试验。研究发现,深部原位应力环境下大理岩峰值强度劣化程度约为无压饱水条件下的3倍,且锦屏大理岩劣化度随应力环境深度（100 m、1000 m、1400m、1800 m和2400 m）呈现非线性变化特征,通过探索锦屏大理岩水软化机理,发现摩擦弱化效应与孔隙水压力作用共同造就了这种非线性变化规律。基于岩石微元强度服从Weibull分布的假定,推导并验证了锦屏大理岩考虑水软化效应的统计损伤本构模型。（3）探索了考虑水软化效应的岩石破坏评价指标,提出了协同考虑岩石破坏与块体滑移的围岩稳定性评价方法。锦屏地下工程围岩稳定性分析单方面考虑岩石破坏或块体滑移均存在不足。在高地应力与孔隙水压力长期作用下岩石强度会发生劣化,导致围岩产生破坏区,继而发生岩块滑移失稳。基于Mohr-Coulomb破坏准则进行了受力分析,得出了考虑水软化效应的岩石破坏评价指标。基于离散元软件3DEC内置FISH语言,开发了考虑水软化效应的岩石破坏评价指标计算程序,并利用DFN-DEM（Discrete Fracture Network-Discrete Element Method）耦合等效岩体模型实现了围岩破坏区从连续到非连续的转变。推导了考虑孔隙水压力的块体滑移安全系数,开发了关键块体识别及安全系数计算程序,并提出了协同考虑岩石破坏与块体滑移的围岩稳定性评价方法。（4）基于多元线性回归理论进行了锦屏交通洞区域的初始地应力反演,计算了局部区域岩石破坏范围随时间的演化规律以及水软化效应长期影响下失稳块体位置及范围。运用BIGEMAP-Rhino-FLAC^3D软件耦合建立了交通洞以下3000m到锦屏山地表的精细化三维模型,基于多元线性回归原理对锦屏交通洞区域进行了地应力反演分析,得到了不同深度区域地应力分布规律。根据围岩稳定性模糊评判结果,选取A34区段（1800 m埋深）、B45区段（1000 m埋深）及地下实验室（2400 m埋深）作为围岩长期稳定性计算的局部区域。基于连续介质理论进行了岩石破坏安全系数计算,得到了考虑水软化效应下岩石破坏范围及安全系数随时间的变化特征。在破坏区域建立了局部DFN-DEM等效岩体模型,基于非连续介质理论进行了块体滑移稳定性分析,得到了水软化效应长期影响下局部区域发生块体滑移的位置和范围。更多还原

【Abstract】 Hydropower resources in China are mainly concentrated in the western mountains and valleys.It is often economical and preferable to arrange hydropower station buildings in extremely deep caverns.Due to the geomorphic characteristics of typical valley and the environment of strong"high in-situ stress"and"high seepage pressure"in the region,the evolution law of surrounding rock mechanics and surrounding rock long-term stability of extremely deep cavern are the key scientific problems that need to be solved.It is difficult for traditional shallow rock mechanics to accurately invert the influence of the coupling effect on rock mechanical properties under different stress conditions at different depths.As a result,deep rock engineering is faced with certain risks and low efficiency.Based on the key project of National Natural Science Foundation of China"Research on Engineering Mechanical Properties and Long-term Seepage Stability of Rock mass at Different depths（No.U1965203）",and closely combined with engineering practice,this paper adopted,engineering survey,equipment development,laboratory test and numerical development and other research methods.The mechanical properties and water softening mechanism of Jinping marble under in-situ stress environment saturated with water at different times were explored.The stability based on water softening effect was studied of surrounding rock of Jinping underground engineering.The evaluation method of surrounding rock long-term stability of Jinping underground engineering was put forward,which enriched the theory and achievements of in-situ rock mechanics.The main research contents and achievements are as follows:（1）The multi-source information of geological environment during the operation period of Jinping underground project is obtained through field survey.Combined with engineering survey and fuzzy mathematics theory,the stability of surrounding rock of underground engineering is preliminarily judged.In order to fully explore the surrounding rock stability of Jinping Traffic Tunnel and D Tunnel of China Jinping Underground Laboratory during operation period,two on-site all-dimensional investigations were carried out.This paper analyzed and summarized the overall seepage condition and distribution characteristics of rock mass engineering with different depths in traffic tunnel A and tunnel B.The surrounding rock stability evaluation model of Jinping traffic tunnel based on fuzzy mathematics theory was established,which took groundwater state,support mode,rock mass drop condition and buried depth of section as first-level indexes.The weight of each evaluation index was obtained by Analytic Hierarchy Process and the final result of fuzzy evaluation was determined by the principle of maximum membership degree.Compared by the evaluation grade,the overall surrounding rock stability of tunnel B is better than that of tunnel A.The sections with the worst surrounding rock stability were A34,A36,A39 and B45,which provided a foundation for analyzing the long-term surrounding rock stability of local areas.（2）Based on the"Deep High Confining Pressure and High Permeability Water-rock Coupling Experimental System"independently developed by the research group,the water softening effect differences of Jinping marble under in-situ stress environment and non-pressure environment were studied comparatively.The statistical damage constitutive model of Jinping marble considering water softening effect was deduced and verified.Based on the self-developed"Deep High Confining Pressure and High Permeability Water-rock Coupling Experimental System",the water softening experiments of Jinping marble under in-situ stress environment and non-pressure environment were carried out for 1 d,23 d,60 d and 100 d.It is found that the peak strength deterioration degree of marble in the deep in-situ environment is about 3times of that in the non-saturated condition.In addition,the deterioration degree of Jinping marble shows nonlinear variation with water saturation time and buried depth（100 m,1000 m,1400 m,1800 m and 2400 m）.Through exploring the water softening mechanism of Jinping marble,it is found that the friction weakening effect and pore water pressure jointly create this nonlinear law.Based on the assumption that rock microelement strength follows Weibull distribution,a statistical damage constitutive model for Jinping marble considering water softening effect is deduced and verified.（3）The rock failure safety factor considering water softening effect is explored.The evaluation method of surrounding rock stability considering both rock failure and block slip is proposed.There are deficiencies in considering rock failure or block slip unilaterally in the study of seepage stability of Jinping underground project.Under the long-term action of high in-situ stress and pore water pressure,rock strength parameters will deteriorate,block may slip and lose stability.The stress analysis is carried out based on Mohr-Coulomb criterion,and the rock failure evaluation index considering water softening effect is obtained.Based on the built-in FISH language of the discrete element software 3DEC,a calculation program of rock failure evaluation index considering water softening effect is developed,and the transformation of surrounding rock failure zone from continuous to discontinuous is realized by means of DFN-DEM coupled equivalent rock mass model.The safety factor of block slip considering pore water pressure is derived,the program of block identification and safety factor calculation is developed,and the evaluation method of surrounding rock stability considering rock failure and block slip is proposed.（4）Based on the multiple linear regression theory,the initial in-situ stress inversion is carried out.The evolution law of rock failure range with time in local area and the unstable block under the long-term influence of water softening effect are calculated.Using BIGEMAP-Rhino-FLAC^3D coupled software,the refined 3D model was established from 3000m below the traffic tunnel to the surface of Jinping Mountain.Based on the principle of multiple linear regression,the inversion analysis of in-situ stress in Jinping traffic tunnel area is carried out,and the distribution law of in-situ stress in different depth areas is obtained.According to the results of fuzzy mathematics comprehensive evaluation of surrounding rock stability in Jinping traffic tunnel,section A34（buried depth 1800 m）,section B45（buried depth 1000 m）and underground laboratory（buried depth 2400 m）are selected as local areas for key calculation of long-term surrounding rock stability.Based on the calculation of rock failure safety factor of continuum theory,the variation trend of failure area and safety factor with time is obtained.The local DFN-DEM equivalent rock mass model is established in the failure zone under long-term seepage.Based on the discontinuous media theory,block slip stability is analyzed,and the location and range of block slippage under the long-term influence of water softening effect are obtained.更多还原