【作者】 李斌；

【导师】 黄达； 杨忠平；

【作者基本信息】 重庆大学 ， 土木工程， 2019， 博士

【摘要】 陡倾顺层软岩边坡失稳破坏是层状岩体滑移、弯曲变形不断发展直至岩层折断或发生倾倒或碎裂溃层破坏的过程。本文从这类失稳边坡的岩体结构特征入手,基于边坡层状岩体的三点弯试验、平推弯曲试验及数值模拟,探讨了层状岩体的断裂力学特性以及在弯曲荷载条件下的变形-断裂演化机制及影响因素,进而开展了陡倾顺层软岩边坡的破坏演化机制及关键影响因素研究,建立了其稳定性计算理论,并给出了防治措施建议。主要研究工作及成果如下:(1)为了明确陡倾顺层软岩边坡的岩体结构特征及变形失稳机制,开展了该类边坡工程实例的地质调查及文献搜集工作,获得了该类边坡具有滑移-压碎-剪断型、滑移-弯曲折断型及滑移-弯曲倾倒型三种主要破坏模式。(2)鉴于层状岩体弯曲折断力学性能是其稳定性的核心控制因素,为揭示边坡岩体的断裂力学特性,开展了边坡岩体三点弯试验及数值模拟工作,研究了层理面方向、层理面强度及间距对层理发育岩体的断裂韧度、断裂模式及强度的影响规律,形成了层状岩体断裂力学行为的岩层结构控制机制。(3)为了揭示陡倾顺层软岩边坡“滑移-弯曲折断”破坏的地质力学机制,设计了可真实反映岩层滑移弯曲断裂受力机制的岩板平推试验及数值模拟,探讨了层状岩体层厚、层间粘结强度、层间裂隙等关键参数对边坡岩体滑移弯曲断裂强度、变形及破坏演化的影响机制,明确了岩层产生滑移-弯曲断裂的力学和地质条件,并基于能量原理,建立了单层和多层岩层的滑移弯曲断裂失稳力学模型。(4)开展了陡倾顺层软岩边坡的变形演化机制的数值模拟研究,从坡体地质结构等内因和开挖及降雨等外因两方面,探讨了陡倾顺层软岩边坡变形破坏的控制因素及变形破坏演化的过程机制,提出了三类主要破坏模式发生的坡体结构条件,为此类边坡稳定性评价和防灾减灾设计优化提供了理论依据。(5)针对陡倾顺层软岩边坡滑移-压碎-剪断和滑移-弯曲两类主要破坏模式,分别基于等K法和弹性板梁理论,推导了边坡发生破坏时极限坡高与临界坡长的计算公式,提出了该类边坡的稳定性计算理论。基于边坡的失稳机制的认识,提出了合理的防治措施建议。更多还原

【Abstract】 The failure of under-dip soft rock slopes is the consequence of intensifying bending deformation of rock layers which may include the fracture or toppling deformation.The thesis starts with the study on the structural characteristics of rock mass,based on the three-point-bending tests on semi-circular specimens and bending tests on the layered rock beams subject to thrust force on the two ends,with numerical method the fracture behavior and the evolution of bending deformation are explored,then on the basis of the analysis,failure mechanism of the under-dip soft rock slope is discussed by conducting numerical simulation.Finally,the stability assessment method and some controlling measures are proposed.The critical research works are described as follows:(1)To clarify the structural characteristics of rock mass and the failure mechanism,the onsite surveys and data collections are conducted on the actural failed rock slopes,by the method of geological analysis based on the findings,three types of failure are summarized,which include sliding-crushing-shearing,fracture induced by sliding and sliding –buckling-toppling failure(2)Considering the common fracture of rock mass the failed slope,to reveal the fracture characteristics of the rock mass,three-point-bending tests are conducted to study the effects of layer direction,bedding strength and spacing on the fracture toughness,fracture pattern of the specimens.(3)Taking the deformation characteristics of sliding-buckling on under-dip slopes into consideration,the bending tests on the layered rock beams subject to thrust force on the two ends are conducted,then the fracture strength,evolution of deformation and shear behavior between layers are revealed,combined with the finite element method,the effects of specimen dimensions,layer thickness,cohesive strength and the distribution of cross-joints between layers are discussed,which clarifies the mechanical and geological conditions for bending-induced fracture of rock layers,Finally,the mechanical models of bending deformation on single layer and multilayers are built on basis of energy theory.(4)The numerical study on the evolution of deformation on under-dip soft rock slopes is conducted and both inner and external controlling factors are discussed.The results indicate that sliding deformation on upper layers,buckling deformation on lower layers and toppling deformation at the slope toe occur in turn in the deformation process of under-dip slopes,then the influence of bedding structure,slope structure on the slope deformation are discussed and the failure types are summarized,which clarifies the conditions for occurring of each failure mode.In addition,the unloading effects caused by excavation and raining effects are studied,which reveals the influencing mechanism and is helpful for stability assessment and engineering design.(5)Taking the different failure modes of the under-dip soft rock slopes into account,stability analysis is conducted based on the “K” Method and elastic beam theory,respectively,then the formula of critical slope height and slope length for failure are derived,which contribute to the establishing of analytical solutions for stability assessment.Finally,based on the failure mechanism discovered above,several strengthening structures are proposed to controlling the deformation of the under-dip slopes and the strengthening effects are evaluated by using UDEC models.更多还原