非饱和土层厚度与充气压力对截排水效果的影响

Influence of unsaturated soil layer thickness and inflation pressure on water drainage efficiency

气驱水理论以及非饱和渗流理论已经在许多领域中得到广泛的应用,而将其应用于边坡防治领域则较少。通过向坡体后缘充入有压气体,可排除坡体中的部分地下水,形成非饱和土层,从而阻断或减小地下水流向下游潜在滑坡区,降低潜在滑坡区地下水位,提高边坡稳定性。多孔介质中气驱水理论属于多相流问题,采用有限元方法模拟研究了不同非饱和土层厚度边坡在允许充气压力下对截排水效果及地下水渗流场的影响。结果表明:地下水水层厚度和水头一定时,非饱和土层厚度越大,临界压力值越大,充气压力上限值越大,允许充气压力范围越大;坡体非饱和土层厚度一定,充气压力在允许范围内越大,截排水效果越好;截排水技术更适用于地下水埋深较浅的坡体;充气稳定后,充气区上游流速分布不均匀,充气区水流流速大幅下降,且相同充气压下非饱和土层厚度越小的坡体稳定后流速越小,充气区下游水位下降,水位线以下流速几乎不受充气和非饱和土层厚度的影响。

Gas flooding theory and unsaturated seepage theory are widely used in many fields,but it is less applied in the field of slope control. By filling the back edge of the slope with compressed gas,some groundwater in the slope is excluded to form unsaturated zone,which can block or reduce the groundwater flow to the potential landslide area and lower the water table in the potential landslide area. Then the slope stability is improved. The theory of gas flooding in porous medium belongs to the multiphase flow problem. The finite element method is used to simulate the effects of different unsaturated zone thickness on the drainage effect and the groundwater seepage field under the allowable pressure. The results show that when the thickness of groundwater layer and head are certain,the larger the thickness of unsaturated zone is,then the larger the critical pressure value is,the bigger the inflatable pressure limit is,the greater the inflatable pressure range is; when the thickness of unsaturated zone is constant,the bigger the inflated pressure is in the allowable range,the better the drainage effect is. This technology is more suit-able for the slope with shallowdepth of groundwater. After the inflation is stable,the velocity distribution in the upstream of the inflatable area is not uniform,and the flow velocity in the inflatable area is greatly reduced. The smaller the unsaturated zone thickness is,the smaller the flow velocity is when the seepage is stable; the water table inthe downstream of the inflatable zone drops,and the flow velocity below the water table is almost unaffected by the thickness of the inflation and unsaturated zones.