滑坡抢险充气截排水方法研究

Rainfall induced landslide groundwater level rise, including the surface rainfall infiltration and the trailing edge groundwater infiltration. The changes of water table in many landslides depend on the magnitude of the groundwater supply from the back scarp of the landslide. In order to guarantee the safety of a landslide and get enough time of dealing with the landslide, it is very important to prevent the groundwater flowing from outside the landslide boundary into the sliding area as well as discharge of groundwater in the slope part before a heavy rainfall process. At present all the measures of interception and drainage of water in a slope are utilized the principle that water flows from the high geopotential position to the low geopotential position, these methods cannot be used to quickly drainage groundwater of a slope. None active drainage method which can pressurize groundwater out of a slope has been reported so far. In this project the research is carried out based on the theory of the high pressure air inflation drainage method and an active drainage method will be build. By taking the controllability advantage of the inflated pressure in a borehole, the seepage direction of groundwater in a slope can be changed and a higher hydraulic gradient in this condition can be developed than that in a natural seepage environment. Then the groundwater can quickly flow out of the sensitive region of a landslide. The research work is based on the tests of air permeability of different types of rocks and soils. The way and influencing factor of the high pressure air spreading in a slope is as the key point of the research; the changes of the permeability and the seepage field in the rocks and soils due to the high pressure air is as the main studies. The basic theoretical problems of the high pressure air inflation technique will be discussed. The applied feasibility of the high pressure inflation technique in the control project of emergency landslide will be verified.

降雨引起坡体地下水位上升，包括表面降雨入渗和后缘地下水入渗。多数滑坡地下水位变化取决于后缘入渗补给量大小。防止滑坡外围地下水入渗，以及在强降雨前排出坡体部分地下水，对确保滑坡安全和赢得滑坡抢险时间十分重要。目前斜坡截排水都是利用水往低处流的重力势特性，属于被动排水方法，无法实现快速截排水。至今没有一种主动可加压的排水技术措施。本项目围绕充气截排水技术方法的基础理论开展研究，构建滑坡主动截排水技术方法。利用钻孔充气压力大小的可控性，改变斜坡地下水渗流方向，形成比自然渗流环境更高的水力梯度，使地下水流出滑坡敏感区域。研究工作以不同类型岩土体的透气性测试为基础，以高压气体在坡体环境中的扩散方式及其影响因素研究为重点，以压入气体对岩土体渗透性和渗流场的改变作用研究为核心，探讨充气截排水技术的基础理论问题，着眼于开拓滑坡充气截排水新方法，解决充气截排水技术在滑坡应急治理工程中应用的可行性问题。

防止滑坡外围地下水入渗，以及在强降雨前排出坡体部分地下水，对确保滑坡安全和赢得滑坡抢险时间十分重要。项目研究以岩土体的透气性测试研究为基础，以高压气体在坡体环境中的扩散方式和影响气水置换因素研究为重点，以压入气体对岩土体渗透性和渗流场的改变作用研究为核心，探讨了充气截排水技术的基础理论问题和应用条件，开拓了滑坡截排水新方法，提出了滑坡充气截排水技术实施的初步方案。.通过大型模型试验论证了充气截排水技术的可行性，试验模型在充气压力15kPa的条件下，模型后缘入渗水位分别为0.4m、0.6m和0.8m时，潜在滑坡区地下水位平均降幅分别12.1%、9.6%和4.5%。建立了堆积层边坡常见的粉质粘土渗透性及导气率的关系，获得了干土状态下的导气率比饱和渗透性大2~3个数量级的研究结论。揭示了坡体充气过程中非饱和区孔隙气压力、孔隙气流速度、孔隙水渗流速度和体积含水量会随时间发生波动性变化，当孔隙气压力随时间增大时，孔隙气体流速也随时间增大，孔隙水渗流速度和体积含水量则随时间减小。揭示了充气点放置在距离潜在滑坡区较近的位置时，截排水效果更好，充气压力越大，潜在滑坡区的地下水位下降越多。渗透系数增大则充气截排水达到稳定所需的时间越少，孔隙率越大则形成稳定截排水效果所需的时间也越长，但渗透系和孔隙率对最终的截排水效果影响微弱。揭示了边坡充气形成非饱和阻水区的过程，依次为：气相不断向水相中溶解扩散出现封闭气泡形态存在的游离气相、气相开始在小部分孔径较大的连通孔隙的流动、优势渗流通道内大量气体突破坡体进入大气、原有孔隙渗流通道扩张且气相渗流通道数量增加。.多数滑坡的抢险过程中，常常接近于极限平衡状态，期间如果出现新的强降雨引起地下水位上升，就可能导致滑坡再次启动，使治理工程毁于一旦，面临滑坡启动的威胁，制约救灾工作的开展，项目研究探索建立的滑坡充气截排水技术具有快速有效的特点，将对滑坡灾害防治起积极作用。