用重锤试验求承压含水层的水文地质参数

Obtaining Hydrogeological Parameters of Press-Bearing Aquifer by Slug Test

井孔响应试验通常指重锤试验,即测量井中水位突然变化时引起的井孔—含水层系统的强迫—自由振动响应。在许多情况下,它能可靠地确定含水层导水系数和其它特性。根据理论计算,该试验法影响范围一般可达100m。井孔—含水层系统的响应特性可分为三类:过阻尼振荡,临介阻尼振荡和欠阻尼振荡。 我们使用数值拉普拉斯变换方法,应用Cooper有关瞬时取水过阻尼响应的理论,计算出给定井孔—含水层系统模型对瞬间取水响应的理论曲线,然后将实际观测曲线与理论曲线对比,就能求出含水层的导水系数和弹性贮水系数。文中列出的三口测井用重锤试验求出的导水系数与抽水试验结果对比发现,数值相差较大,可能是由于实际含水层并非理想模型,或是给出的含水层厚度误差较大,致使计算结果误差较大。据Van der kamp有关欠阻尼响应的理论,计算出井孔—含水层系统的振动特性和响应能力,如角频率、阻尼系数和导水系数等。 井孔响应试验的显著特点是经济,简便,很多井的试验在数分钟之内即可完成。

Well response tests, often referred to as 'slug test', measure the force-free response of a well-aquifer system to an abruptly induced change of the water level in the well. A reliable determination transmissivity and other characters of an aquifer by means of well response tests has become possible for many cases. According to the theoretical caculation, the effect radius of the test is about 100 meters. There are three types of response of well-aquifer system, that is an overdamped, a critically damped and underdamped.Cooper' s theory of response to instantaneous charge of water have been used to interpretate the overdamped oscillation of water level. The method of numerical inversion of Laplace Transforms was used to caculated the theoretical water level response for given well-aquifer system model and the theoretical cxirves was plotted. Then matched the observational curve with the theoretical curves,we could obtain the coefficient of elastic storage and transmissivity of the well-aquifer system.The theory of underdamped case had been developed by Van der kamp. The vibratory character and the response capacity of well aquifer system such as angular frequency, damping constant and transmissivity could be caculated. The difference of transmissivity between slug test and pomp test are listed. The error come from the actual well-aquifer systems are not ideal and the thickness of the aquifer may be larger.The obvious advantage of well response tests is simple and inexpensive, of ten requiring only a few minutes to complete.