含软弱夹层顺层滑坡演化机理及稳定性评价研究

Consequent bedding landslides usually occur along weak interlayer, and have been drawn lots of attention due to catastrophic consequence related to their enormous volumes. Therefore, it is emergent to carry out the study on the evolution mechanism of this type of landslide. Dominated by the surface water, the degradation area of weak interlayer expands gradually, and the physical-mechanical properties show obvious characteristics of the timeliness and the spatial variability. The degradation model of the weak interlayer will be established based on the research of its spatio-temporal rule of degradation. The shearing strain-softening test and shear rheological test on weak interlayer will be carried out under different saturation time conditions, to study the shear characteristics of saturated weak interlayer, then to construct an evolution equation of the shearing mechanics constitutive. Based on the degradation model and the evolution equation of the shearing mechanics constitutive, the geological-mechanical evolution model and the numerical model of typical consequent bedding landslides within weak interlayer will be built. The spatio-temporal evolution rule of the stress and deformation will be studied to reveal the evolution mechanism of the landslide with weak interlayer, by numerical simulation and on-site monitoring. A stability evaluation system will be established, combining the qualitative assessment method based on evolutionary stage, semi-quantitative assessment method based on the determination of critical length of the slide block and quantitative evaluation of the stability by the equilibrium calculation considering the deformation coordination. This study can provide significant scientific theory basis and technical support for the assessment of the stability of the landslide and the management of the landslide in the western China during the construction.

顺层滑坡通常沿着软弱夹层发生滑动，往往因其规模巨大，致灾后果严重而备受关注，亟需开展含软弱夹层顺层滑坡演化机理研究。受地表水流主导作用，软弱夹层劣化区不断扩展，其物理力学性质表现出明显的时效性与空间变异性特点。研究软弱夹层劣化时空规律，建立软弱夹层劣化模式；开展不同饱水时间条件下的软弱夹层剪切应变软化与剪切流变试验，研究软弱夹层饱水劣化剪切力学特性，建立软弱夹层剪切力学本构演化方程；基于软弱夹层劣化模式与剪切本构演化方程，建立典型含软弱夹层顺层滑坡演化地质力学模型与数值计算模型，结合现场监测，分析其应力、变形时空变化规律，揭示含软弱夹层顺层滑坡演化机理；构建一套集基于演化阶段判识的定性评价、基于失稳临界长度确定的半定量评价及考虑软弱夹层劣化特性稳定性计算的定量评价方法于一体的含软弱夹层顺层滑坡稳定性评价体系。为我国西部地区工程建设中的顺层斜坡安全性评价与治理提供重要的理论依据与技术支持。

综合顺层滑坡野外调查、滑带样品采集、滑坡现场监测数据采集、室内试验、数值模拟等手段，具体开展了顺层滑坡软弱滑带原位或原状力学参数研究，库岸顺层滑坡渗透系数及变形机理研究，顺层滑坡稳定性评价方法研究等，得到了如下研究成果：.（1）在黄土坡滑坡临江Ⅰ号滑坡滑带上开展了6组不同法向压力条件下的原位大剪试验。试验结果表明：随着剪切位移的增加，各试验点剪应力逐渐增大，并趋于稳定。试样变形破坏总体经历弹性变形、弹塑性变形和塑性变形三个阶段。原位试验获取得到滑带土土体抗剪强度参数φ=19.9°，c=29.40kPa。.（2）利用试验场大型隧洞群所揭示的黄土坡顺层滑坡滑带，开展三轴非扰动滑带土流变特性试验研究。基于蠕变试验获得了滑带土的长期剪切强度，相对于初始强度，滑带的长期强度的粘聚力和内摩擦角分别降低了32.25%和27.3%。CT扫描技术揭示，在滑带土剪切过程中，粗颗粒发生了旋转，并且在试样的底部最为明显。.（3）提出了基于大数据驱动的顺层库岸滑坡渗透性系数反演方法。该方法包含三个步骤：1）基于现场水文地质调查，建立滑坡渗流数值模型；2）采用GRNN（Generalized Regression Neural Networks）建立滑坡渗透性系数与地下水位之间的非线性关系；3）采用GA（Genetic Algorithm）求解观测地下水位与数值模拟水位拟合最佳条件下的滑坡渗透系数。采用该方法反演得到黄土坡滑坡滑体、滑带与滑床的渗透性系数分比为55.52 m/day、 0.0093 m/day和0.42 m/day。.（4）基于顺层岩质滑坡软弱滑带滑坡软化基本规律，根据滑带材料强度参数表达的形式不同，提出了顺层岩质滑坡两种稳定性求解方法：1）基于滑带本构的滑坡稳定性求解；2）另一种是基于摩尔库伦强度准则的滑坡稳定性求解。.（5）研究了现有分条面为铅直的条分法关于分条面上作用力合力倾角假定所存在的问题。基于Morh-Coulomb准则，推导并建立了分条间作用力合力倾角与滑动面倾角、滑动面内摩擦角和地表倾角的函数关系，由此建立了基于严格考虑条块间作用力关系的滑坡稳定性评价方法。