周期性渗透压作用下红砂岩渗透特性试验研究

水库运行期水位的周期性变化使软岩岸坡防洪限制水位以下的岩体长期处在周期性变化渗透压作用的环境中,这种周期性变化的渗透作用对软岩的渗透特性将产生很大的影响。以三峡库区红砂岩为研究对象,利用自主研发的"具有模拟库水位周期性变化环境下水压变化条件的渗透仪"对红砂岩进行周期性渗透试验,探讨防洪限制水位以下的红砂岩在周期性渗透压作用下的渗透特性变化规律。试验结果表明,随着周期性渗透压的变化,红砂岩的渗水量在第一个渗透周期增长最快,而后逐渐减小;随着周期性渗透压的变化,红砂岩的渗透速度和渗透系数也呈周期性变化;不同岩样的累计渗水量、渗透速度和渗透系数的变化存在一定的差异,但经过4个渗透周期之后,红砂岩的累积渗水量、渗透速度和渗透系数随压力的变化范围稳定,且变化趋势一致。研究结果说明,三峡水库岸坡防洪限制水位以下的红砂岩在水库运行期经历4次周期性水位变化之后,渗透特性逐渐趋于稳定。

Experimental study on permeability characteristics of red sandstone under cyclic seepage pressures

The cyclic fluctuations of reservoir water level make the soft rock in bank slope below the flood control level (FCL) under cyclic seepage pressures and will bring great effects on its permeability characteristics. In order to obtain the variable characteristics of the soft rock under cyclic seepage pressures, permeability tests on red sandstone specimens from Three Gorges Reservoir area, China under cyclic seepage pressures are conducted to simulate cyclic fluctuation of reservoir water level by using the self-developed equipment. The test results show that the cumulative volume of water infiltration has a fastest growth under the first periodic seepage pressures and then decreases under the following cyclic seepage pressures, while the penetration rate and permeability coefficient of the sandstone specimens periodically change with the cyclic variation of seepage pressures. There are some differences in the change of the cumulative volume of water infiltration, penetration rate and permeability coefficient for different specimens. But after four infiltration cycles, the cumulative volume of water infiltration, penetration rate and permeability coefficient of red sandstone vary in the same trend and within a stable range. The study indicates that the permeability characteristics of the red sandstone in bank slope below FCL in Three Gorges Reservoir Area gradually begin to be stabilized after a few number of cyclic fluctuations of reservoir water level.