反倾边坡块状倾倒-滑移复合型大变形机理研究

The generalization of the engineering geomechanics model of the block toppling-sliding composite deformation mechanism, progressive failure crack propagation and strength parameters are the key scientific issues to understand the disaster mechanism of this type of deformed rock mass. In this study, taking the Guobu rock slope as the mainly research object. The variation of strength parameters and crack evolution process in the progressive failure process of prefabricated multi-joint granite are researched by using mechanical tests and real-time observation of crack propagation. The relationship between crack structure parameter C and plastic strainεp is obtained, and the progressive failure strength model based on plastic strain accumulation is established. The centrifuge model test of block toppling -sliding large deformation was made in order to study the influence of spacing, trace length, connection rate of structural plane to the large deformation. It reveals the cracks expanding regulation of block toppling-sliding and potential failure. We proposed the geo-mechanical model of block toppling-sliding large deformation of rock slope. The established progressive damage strength model is embedded in the Mohr–Coulomb model with pull-cutting to realize the deterioration process of rock mass mechanical parameters during the progressive failure deformation process. In other words, realizing the simulation of the crack expanding and toppling failure in complete blocky rock mass. The research results can provide a theoretical basis for revealing the mechanism of block toppling-sliding composite deformation slope disasters, and controlling disasters.

块状倾倒-滑移复合型变形机理的地质力学模型概化及渐进破坏细观裂纹演化与强度参数定量刻画是认识该类岩体变形致灾机理的关键科学问题。本项目以果卜大变形岸坡为研究对象，采用室内力学试验及裂纹扩展实时观测，研究预制多节理花岗岩渐进破坏过程中的强度参数变化规律及裂纹演化过程，获取裂纹结构参数C与塑性应变εp的关系，建立基于塑性应变累积的多节理花岗岩渐进破坏强度模型。采用离心机模型试验测定结构面间距、迹长、连通率对块状倾倒-滑移复合型变形的影响效应，揭示此类边坡岩体裂隙扩展规律及贯通机理，概化块状倾倒-滑移复合型大变形机理的地质力学模型。将建立的渐进破坏强度模型嵌入到带拉截断的Mohr–Coulomb模型实现岩体在渐进破坏变形过程中岩体力学参数的劣化，搭建可实现模拟裂纹扩展及完整块体倾倒折断破坏的UDEC-DM模型。研究成果为揭示块状倾倒-滑移复合型变形边坡成灾机理及防灾减灾提供理论支撑。

本项目以果卜大变形岸坡为研究对象，开展块状倾倒-滑移复合型大变形岩质边坡地质调查与测试，分析河谷岸坡形成演化过程、伴随河谷演化的边坡应力场及其分带特征；调查结构面类型、发育特征，概化出控制块状岩体边坡变形破坏的优势结构面特征，建立块状结构岩体边坡变形破坏的岩体结构模型。开展边坡块状倾倒-滑移复合型大变形的模型试验，制作含三组非贯通结构面边坡模型，分析结构面间距、迹长、连通率对块状倾倒-滑移复合型大变形的影响效应，研究块状倾倒-滑移作用下边坡裂隙扩展规律及贯通机理，提出边坡块状倾倒-滑移复合型大变形机理及其地质力学模型。搭建可实现模拟裂纹扩展及完整块体倾倒折断破坏的UDEC-DM模型数值平台，揭示边坡发生块状倾倒-滑移复合型大变形的形成条件及成因机理。研究结果表明复合型变形破坏模式表现为“下沉-楔入”破坏、塌滑破坏、倾倒拉裂、深部岩体“张裂”。地质力学模式概括为：块状倾倒-滑移复合型变形破坏模式。模型试验及数值计算揭示岸坡岩体在自重作用下的变形受多组结构面控制，表现为受陡倾坡内组结构面控制的弯曲倾倒变形,折断面发育有追踪第③组中缓倾角结构面的趋势，岸坡前缘的小块体有逐渐脱离母岩而发生小规模塌滑破坏的趋势，随着变形的加剧，后期浅表部岩体变形表现为松动、破碎而演化为现场调查的坡体塌滑变形，岩体结构逐渐劣化至散体结构。总体上边坡变形表现为花岗岩板裂岩体的倾倒、根部折断、折断面追踪坡体内中缓倾角结构面，后缘坡面表现为拉裂，深部潜在贯通面具有典型的阶梯状形态。岸坡大变形的实质为倾倒变形为主，伴有拉张、下沉的蠕变而非滑动性质的破坏。现今岸坡大变形的机制为上部楔入-倾倒产生的推挤性变形与下部鼓张、倾倒性牵引变形的复合变形机制。研究成果为揭示块状倾倒-滑移复合型变形边坡成灾机理及防灾减灾提供理论支撑。