强震作用下山区小流域水动力条件下沟坡系统可移动固体物质研究

Shenxi gully which located at WenChuan Earthquake areas. The flood and debris flow occurred frequently after the earthquake and even becoming increasingly intense, which has posed a serious threat to the Baisha River basin, the Du Jiangyan Irrigation Project and the Chengdu drinking water safety, urgently need to take scientific and effective prevention countermeasures. The research and prevention practice at home and abroad indicate whether the forecasting or early warning of flood and debris flow success or not and whether the prevention project science or not, the key is an effective grasp of the removable solid materials quantity and its spatial and temporal distribution characteristics under the hydrodynamic conditions. Therefore, this study is focused on the drastic changes on the conditions of soil mechanics environment of gully-slop system of Shenxi vally watershed after the strong earthquake, through field tests and mechanical analysis, researching the removable characters and critical discrimination mechanical model of channel and slope solid materials under hydrodynamic effect respectively; with this model to calculate the thickness of the removable solid material of each watershed element under different hydrodynamic conditions; based on GIS, establishing the map of removable solid materials space distribution; for the similarities and differences of geotechnical parameters and the spatial distribution of the hydrodynamic parameters, setting up the continuous/non-continuous model of the removable thickness of the solid material along the slope or channel respectively, then calculating the removable solid material reserves along slop (vertical direction against channel or slop runoff direction) and channel.The.results will provide a theoretical basis for the engineering prevention, forecasting and early warning system.

汶川地震遗址深溪沟，震后山洪泥石流频繁发生，且愈演愈烈，对白沙河流域、都江堰水利工程和成都市饮用水安全构成严重威胁，亟待采取科学有效的防治对策。国内外研究与防灾实践表明：山洪泥石流预警报成功与否、防治工程是否科学，关键在于对水动力作用下可移动固体物质数量及其时空分布特征的有效把握。为此， 本研究针对强震后深溪沟沟坡系统岩土力学环境剧变条件，通过现场试验和力学分析，分别研究沟道、坡体固体物质在水动力作用下可移动特性及其临界判别力学模型；利用该模型，计算流域各微元在不同水动力条件下可移动固体物质的厚度，基于 GIS 建立可移动固体物质空间分布图；针对岩土力学参数与水动力参数空间分布的异同性，分别建立可移动固体物质厚度沿坡面或沟道的连续性/非连续性数学模型，从而计算沿坡面（与沟道垂直方向或坡面径流方向）及沟道沿程可移动固体物质储量。研究结果将为工程防治和预警报系统提供理论依据。

泥石流防治工程规划布局、设计技术指标是否科学合理，关键在于把握松散固体物质可移动的数量及其移动过程，对设计频率条件下泥石流规模及其流量过程的合理分析。可移动固体物质广泛分布于震后灾区山地表层，但一直以来，国内外相关学者大都只是对组成灾体的松散固体物质做了定性的描述，而未定量化地探讨可移动固体物质在水动力条件下的岩土力学特性变化及其机理。本项目通过详细对地震重灾区虹口深溪沟流域的野外调查、室内外试验和理论分析，探讨了在不同水动力作用下流域沟坡系统松散固体物质的可移动临界控制条件，并由此建立了不同水动力作用下可移动固体物质临界判别力学模型，从而计算了流域可移动固体物质的储量。经过团队的努力，主要取得以下方面成果： （1）通过对沟坡的固体物质进行受力分析，建立了不同水动力作用下固体物质可移动临界深度判别模型；（2）通过分析坡型（凹型、凸型）对固体物质起动的影响，建立了凹型、凸型斜坡固体物质起动临界深度与平直型坡可移动临界深度间的关系；（3）通过室内系列模拟实验，对不同水动力条件下固体物质起动进行了模拟，分析了不同固体物质失稳起动模式、恒定渗流条件下坡体内水力学参数变化规律、恒定径流条件下固体物质冲刷速率变化规律以及坡型对固体物质起动的影响等；（4）针对深溪沟流域锅圈岩沟源区固体物源分布特征及性质参数和水动力条件，选取对应的可移动临界深度判别模型，计算了研究区域水动力条件下可能起动的最大物源量。本项目建立的可移动固体物质的临界判别力学模型可为泥石流防治工程和预警报提供理论依据，为保障震后灾区基础设施、人民生命财产安全以及泥石流学科的发展起到积极的推动作用。