亚高山草甸土浅层溜滑侵蚀机理及危险性预测方法研究

Subalpine meadow soil is widely distributed in the deep-cut valley area of western Sichuan plateau. Due to the specific structure of meadow soil and climatic conditions, rainfall effect can cause a large area of subalpine meadow soil erosion behaved with disintegration and slide step by step. This can cause terribly soil erosion and meadow degeneration, and is regarded as the typical ecologically vulnerable phenomena in western Sichuan plateau. This project intends to combine field survey, laboratory experiment, in situ monitoring to study the rainfall induced mechanism of shallow slide erosion on alpine meadow soil as well as the corresponding risk prediction method. Firstly, based on the field survey and test of original samples, gaining the structure and physical-mechanical properties of subalpine meadow soil, and generalizing the geological prototype and analyzing the development rules. Then analyzing the rainfall infiltration laws by in situ monitoring of groundwater and numerical analysis, revealing the dynamic groundwater pressure driven mechanism of shallow slide erosion on subalpine meadow soil. Lastly, based on the limitations of existing hydrological deterministic model, combining with the infinite slope model, transient hydrological model, non-deterministic model and GIS system all together, to form a rainfall-induced risk prediction integrated system of shallow slide erosion of subalpine meadow soil. This study has certain theoretical and practical significance on accurate evaluating the risk of erosion on subalpine meadow soil, effectively predicting erosion amount, establishing corresponding control measures of erosion on meadow soil and reasonable ecological management system on plateau area.

亚高山草甸土广泛分布于川西高原的深切河谷斜坡地带，受特殊的土体结构及气候条件影响，浅层草甸土在雨季常发生解体并逐级溜滑，造成大面积的土体侵蚀和草甸退化，是川西高原生态脆弱的典型表现之一。本项目拟在野外调查、室内试验和原位监测相结合的基础上，深入研究草甸土降雨型的溜滑侵蚀机理和危险性预测方法。首先，通过野外调查和室内试验，概化地质原型并分析侵蚀的发育规律，充分掌握亚高山草甸土的结构特征、物理力学性质；进而根据现场原位监测试验和数值分析研究草甸土降雨入渗规律，揭示其动水压力驱动型的侵蚀机理；最后，根据致滑机理对现有物理确定性模型进行改进，将无限边坡模型、瞬态降雨入渗模型、不确定性分析模型和GIS进行耦合，建立降雨型亚高山草甸土浅层溜滑侵蚀的危险性预测集成系统。本研究对准确评价亚高山草甸土浅层溜滑侵蚀的危险性，制定相应的草甸土侵蚀防治措施，以及合理的高原生态保持管理制度，具有一定理论和现实意义。

亚高山草甸土广泛分布于川西高原的深切河谷斜坡地带，受特殊的土体结构及气候条件影响，浅层草甸土在雨季常发生解体并逐级溜滑，造成大面积的土体侵蚀和草甸退化，是川西高原生态脆弱的典型表现之一。本项目在野外原型调查的基础上，通过建立室内物理模型，模拟亚高山草甸土在降雨条件下的浅层溜滑破坏过程，揭示了不断增加的动水压力是导致亚高山草甸土溜滑破坏的主因，并提出了亚高山草甸土溜滑的动水压力驱动作用机理；接着根据致滑机理提出了降雨型亚高山草甸土浅层溜滑侵蚀的空间分布预测模型（Ad-TSMS模型）。Ad-TSMS模型结合TOPMODEL模型来有效考虑集水区内地形与地下水流的侧向辅助，并考虑渗透压力的影响改进了TRIGRS的无限斜坡的地质力学模型。通过比对验证，Ad-TSMS模型的预测结果与野外调查的溜滑侵蚀点编录数据吻合度更高，说明对TRIGRS模型的改进有效提高了预测精度。最后，项目基于Rosenblueth点估计法建立了适宜于亚高山草甸土浅层溜滑侵蚀的空间预测集成系统，并开展以新都桥镇为典型对象区的亚高山草甸土的浅层溜滑侵蚀的空间预测评价。项目对准确预测亚高山草甸土浅层溜滑侵蚀的空间分布，制定相应的草甸土侵蚀防治措施，以及合理的高原生态保持管理制度，具有一定理论和现实意义。