自由振荡法试验在地层渗透性评价中的应用与探讨

自由振荡法试验就是通过一定激发手段使得钻孔内水位发生瞬时变化,获得水位-时间响应数据来确定含水层的渗透系数。该方法在地层渗透性评价中得到广泛的应用,多采用的是气压法激发水头的方式。考虑到与气压式激发水头的方式相比,注水式则只需往孔内注入一定量的水就可以实现孔内的水头差,且需要设备少,操作简单,因此,尝试将注水式激发水头的自由振荡法试验应用于某工程,并进行研究对比。通过注水式振荡试验、气压式振荡试验、标准抽水试验优缺点的比较,认为注水式振荡试验最为简便快捷,但部分实验数据出现偏差。分析试验数据出现偏差的原因,提出改进的方法,并论证该试验方法的可行性,以期在今后的工作中对改进的方法进行验证,达到此方法能推广的目的。

Discussion on the Application of Free Oscillation Test in Stratum Permeability Evaluation

Free oscillation test is a hydro-geological test which adopts excitation method to make an instantaneous change in borehole water level.Through the test process the water level-time response data will be measured and thus to determine the permeability coefficient of the aquifer stratum.This test has been applied in many engineering projects for stratum permeability evaluation and has an efficient result.Air pressure is usually adopted to excite the water head,while water injection is convenient to excite water head only by injecting a certain amount of water.It needs less equipment and operates easily.In this research we conducted a free oscillation test with water injection method to evaluate the stratum permeability coefficient and compared the advantages and shortcomings of various test methods (gas pressure and standard water pumping and injection).We found that free oscillation test with wa-ter injection method is the most convenient,however,some part of the test data revealed deviations rather than the results derived from the standard water pumping test.We analyzed the causes of the deviation and put forward im-provements to demonstrate the feasibility of this test method with the expectation to verify the improved method and achieve popularization of this test method in hydropower station projects.