水位变化条件下粘性土渗流特征试验研究

开采孔隙承压含水系统,引起含水层水头下降。通常认为相邻含水层一经出现水头差,便会有通过粘性土层的越流渗透。但在粘性土两侧含水层出现水头差初期,粘性土内部水头降低缓慢,并伴随有释水压密过程。笔者采用多用途饱水粘性土固结和渗透试验装置,对不同岩性的粘性土原状样进行了释水、吸水与越流发展过程之间关系的试验。试验表明,含水层水位升、降变化,首先引起相邻粘性土吸水回弹或释水压密,而后出现粘性土吸水或与释水越流并存阶段,越流的出现,明显滞后于含水层水头变化,当吸水或释水过程结束后,越流渗透达到稳定。越流滞后时间与土的固结程度有关,笔者采用一维固结理论提出了计算越流滞后时间的方法。

Experimental research on saturation characteristics of clay under variation in water levels

The water level in a confined aquifer will fall as the confined aquifer is being exploited. Generally, leaking processes will occur in the claypan, while there is a hydraulic gradient between two adjacent aquifers. However, at the beginning of the appearance of a hydraulic gradient, the water level in clay falls slowly, and is accompanied by discharging and pressing. We have carried out a series of experiments with various original states of clay by employing multi-function saturated clay tester and analyzed the relationships between the development processes of leaking, and discharging or sopping. These experiments show that the changes in water level promoted sopping or discharging in clay, and then, discharging or sopping coexisted with leaking processes. Their appearance is distinctly hysteretic to the changes of water level; and after discharging or sopping process is terminated, the leaking process reached stabilization. The hysteretic time of leaking is related to the concretion degree of clay. We have put forward a method of calculating the hysteretic time of leaking by adopting one-dimensional concretion theory.