【作者】 陈东辉；

【导师】 陈慧娥；

【作者基本信息】 吉林大学 ， 地质工程， 2021， 博士

【摘要】 随着我国基建事业的快速完善与发展,各类工程的建设范围与规模也日益扩大。岩体是水利、交通、核电等国家大型战略工程建设的重要载体,其稳定性对工程的安全运营至关重要。受到内外动力地质营力的影响,岩体内部往往会发育有性质、规模迥异的结构面系统,比如裂隙、软弱夹层、层理等,这些结构面系统的切割作用极大程度上劣化了岩体的质量,增加了岩体变形与失稳破坏的可能性。因此,充分考虑岩体结构特征对其力学性质的影响,是岩体工程设计的必备任务,同时也是保证岩体工程长期稳定性的重要技术支撑。迄今为止,在岩体力学分析领域,特别是针对岩体工程的整体稳定性分析问题,鲜有可靠有效的技术手段将数目庞杂的结构面系统全部直接建立在分析模型中。针对目前存在的难点,岩体的等效力学参数能够将结构面系统对岩体质量的弱化效应隐式地包含在内,并建立相应的等效结构地质力学模型,进而实现复杂结构面控制的岩体工程分析,这是符合现阶段理论与实际工程需求的。其中,岩体结构特征和等效力学参数的获取是建立等效结构地质力学模型的前提和关键所在。本文以广西大藤峡水利枢纽泄水闸28#坝段为例,旨在研究坝基岩体的结构特征以及结构面系统对岩体等效力学参数的影响,并建立综合考虑确定性结构面与随机结构面系统的多尺度等效结构地质力学模型。通过数值模拟手段和物理仿真试验构建了等效模型,并对等效模型的变形特征与变形破坏模式进行了分析与探讨,为工程的施工建设与支护方案提供一定的科学依据。通过对上述内容综合的分析研究,本文取得的主要成果和结论如下:（1）基于详实的现场工程地质勘察,重点查明了泄水闸28#坝段各地层内结构面展布的几何特征。岩体内发育有断层、层理、软弱夹层以及构造裂隙多种结构面。其中,各地层内层理极其发育,均表现为平行层理构造。那高岭组D₁n和郁江阶D₁y¹-1地层中软弱夹层同样发育,其产状同岩层一致,间距为2～5m。构造裂隙在D₁n和D₁y¹-1地层的相邻软弱夹层间是贯通的,而在郁江阶D₁y¹-2和D₁y¹-3地层是呈断续状态。通过优势分组可知岩体内的裂隙大致呈现两个优势组。对于二维稳定性分析,走向与剖面方向近垂直的裂隙组在分析模型中发挥重要作用,该组裂隙整体倾向上游,倾角约79°,平均间距约为2m。（2）针对D₁y¹-2与D₁y¹-3地层岩体中发育的断续构造裂隙,可基于概率统计学的原理,采用三维网络模拟手段再现其在岩体三维空间中的展布特征及交切状态。进而,用分析剖面截取生成的三维网络模型,可获得具有相似统计特征的结构面二维迹线分布情况。基于Dijkstra最短路径搜索算法可得到潜在破坏方向上的最大连通率及其对应的裂隙几何形态,为后续断续裂隙等效抗剪强度的合理评估提供重要的数据支撑。（3）基于等效应变原理,全面考虑了岩体等压和非等压的赋存应力环境,从力学的角度首次推导出一种考虑围压效应的岩体等效弹性模量的解析表达式,不仅可以便捷、可靠地获取岩体的等效弹性模量,而且可以定量的表征岩体等效弹性模量的应力依赖性。同时,系统地阐述了广义Hoek-Brown准则中关键参数的定量取值,进而可依据广义Hoek-Brown准则评估岩体的等效抗剪强度指标。力学试验和岩土测试手段可减少人为取值的主观影响,可有效改善基于Hoek-Brown准则获取裂隙岩体等效抗剪强度指标的可靠度。（4）通过对室内类岩石材料的直剪试验研究,明确断续裂隙潜在破坏路径上裂隙的连通率、起伏角以及路径经过的裂隙数量对断续裂隙等效抗剪强度的影响,探究岩体剪切破坏过程中存在的岩桥弱化机制。基于试验结果,首次提出一种综合考虑多因素裂隙几何特征和岩桥力学性能损伤的修正Jennings强度准则。与传统的Jennings准则相比,修正的Jennings强度准则更符合岩体的真实破坏情况,可以有效地提高评估断续裂隙等效抗剪强度的精度,具有显著的工程实践意义。（5）基于岩体结构特征以及等效力学参数的研究,构建了综合考虑了多尺度结构面影响下的泄水闸28#坝段坝基岩体的等效结构地质力学模型。为探明等效模型的变形破坏模式,等效模型在构建中涉及到双重等效:第一重等效是岩体中发育密集的层理对岩体性质的影响被隐式地表达在等效力学参数中,通过给岩块单元赋予等效力学参数,可将复杂层理控制的不连续岩体分析问题转换为连续介质模型分析问题;第二重等效是将断续裂隙和岩桥组成的最危险路径等效为贯通的裂隙,由此既能考虑断续裂隙的影响,又能最大限度反映岩体工程在荷载作用下的潜在失稳模式。（6）数值模拟是分析岩体工程变形与破坏方式的重要手段。通过数值手段构建泄水闸28#坝段的等效模型,采用完全流-固耦合机制分析坝基等效模型的稳定性及变形破坏模式。同时,基于相似性理论,采用物理仿真试验重现泄水闸28#坝段等效模型的地质构造与水工构筑物,研究了坝基岩体的综合稳定性及其变形破坏模式,可与数值手段起到互相验证、补充的作用。两者的结果综合表明,在外荷载作用下等效结构控制的坝基岩体并未形成整体的滑移破坏面,其变形破坏模式主要为上下游近闸段浅层结构面的开裂破坏,以及下游坝基岩体中贯通的压性塑性区所导致的其上部近地表岩体的溃曲破坏。更多还原

【Abstract】 With the rapid improvement and development of infrastructure,the scales of various projects are also gradually increasing.The rock masses are the essential carrier of the crucial strategic projects,for example,hydropower,transportation,and nuclear power,whose stability is significant to the safety of the engineering.Influenced by the geologic process,rock masses often developed structural surfaces with different nature and scale,such as fracures,weak interlayers,faults,beddings,etc.The cutting action of these structural surfaces greatly degrades the quality of the rock masses,and increasing the possibility of deformation and instability failure of rock masses.Therefore,fully considering the impact of structural characteristics on its mechanical properties is the necessary task of rock engineering design,and it is also an important technical support to ensure the long-term stability of rock engineering.At present,in the field of rock masses mechanical analysis,especially for the overall stability analysis of rock masses project,there are few effective technical means to directly establish a large number of structural plane systems in the analysis model.As for the existing difficulties,the equivalent mechanical parameters of rock masses can implicitly include the weakening effect of structural planes on rock masses quality,and then establish the corresponding equivalent structural geomechanical model,so as to realize the analysis of rock masses engineering controlled by complex structural planes,which is in line with the current theoretical and actual engineering needs.It can be seen that the acquisition of structural characteristics and equivalent mechanical parameters of rock masses is key to establish equivalent structural geomechanical model.This thesis takes the No.28 sluice of the Datengxia Hydropower Station in Guangxi as the engineering background.The purpose is to analyze the structural characteristics of dam foundation rock masses and the influence of structural planes on equivalent mechanical parameters of rock masses,and then establish a multi-scale equivalent structural geomechanical models considering the deterministic structural planes and random structural planes.Meanwhile,the equivalent model is constructed using numerical and physical model test,and the deformation process and instability mode of the equivalent model are analyzed and discussed,which offers the scientific guidance for the building and support scheme of the project.Based on the synthetical analysis of the above contents,the conclusions of the thesis are drawn:（1）Based on the detailed field investigation,the geometric characteristics of the structural planes developed in the dam foundation the No.28 sluice are identified.Faults,beddings,weak interlayers and structural fractures are developed in the rock masses.Among them,the beddings of each stratum are extremely developed,showing parallel bedding structure.Weak interlayers in Nagaoling（D₁n）and Yujiangian D₁y¹-1formations are also developed,and their occurrence is basically the same as that of the rock stratum,with a spacing of 2～5m.The structural fractures are connected between the adjacent weak interlayer in D₁n and D₁y¹-1 formations,while it is intermittent in D₁y¹-2 and D₁y¹-3 formations.The fractures are roughly divided into two groups.For the two-dimensional stability study,the fracture group whose strike is nearly perpendicular to the section direction plays an important role in the analysis model.This fracture group inclines upstream,with dip angle of about 79°and an average spacing of about 2 m.（2）For the complex intermittent structural fractures developed in the rock masses of D₁y¹-2 and D₁y¹-3 formations,their distribution characteristics and intersecting state in three-dimensional space of rock masses can be reproduced by means of three-dimensional network simulation based on the principle of probability statistics.Furthermore,the generated network model is cut to obtain the two-dimensional trace distribution of structural planes with similar statistical characteristics.Based on the Dijkstra shortest path search algorithm,the maximum connectivity in the potential failure direction and its corresponding fracture geometry features can be obtained,which provides important data support for the subsequent reasonable evaluation of the equivalent shear strength of intermittent fractures.（3）Based on the principle of equivalent strain,an analytical solution of the equivalent elastic modulus of rock masses considering confining pressure effect is derived for the first time from the perspective of mechanics,which can not only obtain the equivalent elastic modulus of rock mass conveniently and reliably,but also quantitatively characterize the stress-dependency of equivalent elastic modulus.At the same time,the quantitative values of key parameters in the generalized Hoek-Brown criterion are systematically expounded,and then the equivalent shear strength could be estimated according to the generalized Hoek-Brown criterion.Mechanical test and geotechnical test can reduce the subjective influence of artificial value,and can effectively improve the reliability of obtaining the equivalent shear strength of rock masses using H-B criterion.（4）Through the direct shear test of indoor rock-like materials,the effects of the connectivity,fluctuation angle and the number of fractures on the potential failure path of intermittent fractures on the equivalent shear strength of intermittent fractures are clarified,and the weakening mechanism of rock bridges in the process of rock masses shear failure is explored.Based on the test results,a modified Jennings strength criterion considering multi factor fractures geometric characteristics and mechanical property damage of rock bridges is proposed for the first time.Compared with the traditional Jennings criterion,the modified Jennings criterion is more in line with the real failure of rock masses,can effectively improve the accuracy of evaluating the equivalent shear strength of intermittent fractures,which has remarkable significance for engineering practical.（5）Based on the study of rock mass structural characteristics and equivalent mechanical parameters,an equivalent structural geomechanical model of dam foundation rock masses of sluice 28#dam section considering the influence of multi-scale structural planes is constructed.In order to explore the deformation and failure mode of the equivalent model,the equivalent model involves double equivalence in the construction:the first equivalence is that the influence of dense beddings on the properties of rock masses is implicitly expressed in the equivalent mechanical parameters.By giving the equivalent mechanical parameters to the rock block elements,the analysis problem of discontinuous rock masses controlled by complex beddings can be transformed into the analysis problem of continuous medium model;The second equivalence is that the most dangerous path composed of intermittent fractures and rock bridges is equivalent to through-out fractures,which can not only consider the influence of intermittent fractures,but also reflect the potential instability mode of rock masses engineering under load.（6）Numerical simulation is an important means to analyze the deformation and failure modes of rock masses engineering.The equivalent model of No.28 sluice is constructed by the numerical simulation,and the stability and failure mode of the dam foundation equivalent structure are analyzed by using the complete fluid-solid coupling mechanism.Meanwhile,the physical model test is used to reproduce the geological structure and hydraulic structure of the equivalent model based on the similarity theory,and the comprehensive stability and failure mode of the dam foundation rock masses are studied,which can verify and supplement each other with numerical simulation.The results show that the overall through-out sliding failure surface is not formed under the action of external load,and the deformation failure modes are mainly the cracking failure of the structural planes near the dam heel and toe key trench,and the buckling failure of near surface rock masses in downstream caused by the through compressive plastic zone in the downstream rock masses.更多还原