岷江上游大型深层蠕滑型滑坡渐进变形破坏机制与动态稳定性研究

The upstream of Minjiang River is located in the eastern margin of the Tibetan Plateau, the topography and geologic structure in this area are very complex, and there are numerous large and deep-seated creeping landslides distributed in this area, which are characterized by large scale, deep-buried sliding belt, and with obvious progressive deformation characteristics. At present, it is still insufficient about the recognition of sliding belt soil mechanical strength characteristics and dynamic stability of large deep-buried creeping landslides, which has seriously restricted large landslides early prevention. Based on the investigation of these large deep-buried creeping landslides formation background and development characteristics, Zhouchangping landslide and Xiangyangping landslide will be selected as typical cases to carry out detailed field investigation, in-situ direct shear tests and laboratory tests, in order to reveal the landslide spatial developmental characteristics and hydrogeological structure; the effective rainfall infiltration mechanism under different rainfall intensity and duration will be studied, in order to reveal the macroscopic and microscopic mechanical strength properties of the sliding belt soil under the cyclical coupling effect of seepage - consolidation - creeping. The landslide physical simulation and numerical simulation will be used to study the creeping landslide evolution mechanism of deformation and instability lag of large landslides progressive deformation mechanism under the multi-field coupling conditions, such as rainfall - groundwater seepage - long-term gravitational deformation, and this study plans to propose the early instability criterion of acceleration creeping sliding. The research findings of project would provide important theoretical foundation for early instability identification and comprehensive prevention of large deep-seated creeping landslides.

位于青藏高原东缘的岷江上游地形地貌和地质构造复杂，大型深层蠕滑型滑坡极为发育，具有规模大、滑带深、渐进变形破坏显著等特点。目前国内外对大型深层蠕滑型滑坡滑带土的力学强度特性和滑坡动态稳定性认识仍存在不足，严重制约着滑坡灾害的早期防范。本项目拟在该类滑坡形成背景和发育特征研究的基础上，选取周场坪滑坡、向阳坪滑坡等典型案例，采用野外精细调查、原位测试和室内试验等手段，剖析大型深层蠕滑型滑坡的空间结构特征和水文地质条件，研究不同雨强和历时条件下降雨有效入渗机理，揭示深层滑带土在渗流－固结－蠕滑多场耦合周期性作用下的宏观和微观力学性质及演变规律；采用物理模拟和数值模拟等方法，研究降雨－地下水渗流－重力时效变形等多场耦合条件下的大型滑坡渐进变形破坏机制和失稳滞后性，提出基于渐进变形破坏的滑坡稳定性评价方法和失稳早期判识体系。本项目将为大型深层蠕滑型滑坡失稳的早期判识和综合防范提供重要理论依据。

本项目采用遥感、InSAR形变分析、多工况室内试验和物理模拟试验等技术方法，结合钻探、物探等资料分析，研究了青藏高原岷江上游等深切峡谷区大型深层蠕滑型滑坡发育特征、渐进变形破坏机制与动态稳定性，取得如下主要成果： .（1）揭示了岷江上游、大渡河上游、金沙江中段等深切峡谷区大型深层蠕滑型滑坡特征，认为青藏高原东部大型深层蠕滑型滑坡多发育2-3层深层滑带，按照空间结构将深层滑坡划分为后缘洼地蠕滑型、顺层基岩蠕滑型和堆积层深层蠕滑型等3种类型。.（2）建立基于面向对象分类法的古滑坡与新生滑坡判识模型，揭示岷江周场坪大型深层滑坡空间结构，新发现金沙江雄巴滑坡、格聂山隧道入口滑坡等大型深层蠕滑型滑坡，提出其具有高位启滑和深层蠕滑两种地质力学模式。.（3）基于离心机物理模拟等试验，揭示了2018年江顶崖大型深层蠕滑型滑坡启滑特征，提出了降雨和河流侵蚀诱发江顶崖大型深层滑坡的启滑机制。.（4）揭示了金沙江上游滑坡堵江-溃坝-灾害链对下游大型深层蠕滑型滑坡的远程促滑与加速蠕滑效应。.（5）创新建立了基于加压固结-渗流耦合作用下三轴反压试验测试方法，揭示滑带土在围压增大含水率降低条件下出现应变硬化现象，提出大型深层滑坡间歇性蠕滑、持续性蠕滑与渐变性蠕滑的阶段判别标志。.（6）进一步查明大渡河上游甲居古滑坡空间结构，结合InSAR形变结果，将甲居古滑坡划分为5个次级滑体，提出了甲居滑坡在强降雨和河流侵蚀作用下的蠕滑机制。.（7）建立了基于LiDAR精细地形刻画、浅层地震地球物理探测和钻孔联合解译的大型深层蠕滑型滑坡结构构建技术与体积计算方法。.（8）建立了基于遥感-InSAR-GNSS位移监测的深层蠕滑型滑坡变形研究方法，揭示了周场坪滑坡的牵引式蠕滑机制，提出了滑坡渐进变形的4个典型阶段和破坏机制。.（9）基于本项目研究成果，提出的川藏铁路大型深层蠕滑型滑坡潜在风险及线路优化和防灾建议，得到采纳应用。