| The extensive exploitation of groundwater caused a series of environmental problems such as seawater intrusion, land subsidence, wetland shrinkage, surface vegetation destruction. In order to alleviate this issue, many countries adopt the method of artificial recharge to replenish groundwater. The methods of artificial recharge of groundwater mainly can be divided into two types- surface ground irrigation and well irrigation. However, various clogging would happen in the aquifer recharge process with the extension of recharge time. Therefore, the aquifer recharge efficiency had a dramatic decrease and sometimes would even lead the whole load of work into vain. It is very common in the process of aquifer recharge.Usually the clogging can be divided into suspended particles clogging, pressure clogging, gas clogging, biological clogging and chemical clogging. The research in suspended solids blocking mechanism has been more mature at present, but little research has been done into gas clogging. This paper chosen the sandbox as experimental material and investigated the gas clogging in the aquifer recharge process.In order to reduce the affect of other factors, the experiments use high purity quartz sand and good quality water as aqueous medium and recharge water, respectively. Firstly, after degassing treatment, recharge water were used to aquifer recharge for 16 h. In this process, the water flow of aquifer increases gradually and tending to be stable state finally. After that, micro-air bubble water were used to aquifer recharge for 160 h. The hydraulic conductivity of aquifer was increasing over time. After recharge using micro-air bubble water, the aquifer was processing it in back yang. Then recharge 16 h using degassed water and recharge 130 h using aeration water when the water flow of aquifer reaches the maximum value. The experimental sandboxes were scheduled to seven infiltration stages. The patterns of the gas clogging in the aquifer recharge process were studied by comparing the change of hydraulic conductivity(K,). While the mechanism of gas phase clogging were studied by comparing the change of hydraulic conductivity of the whole structure.The result showed that the K,of infiltration area was gradually decreased with the direction of the flow. But there are very few K, higher than the adjacent value in the former period. This may be because the bubbles into the aquifer with the injection of water and piled up in the passage. But fusion happens when small bubbles gather in a certain degree and form larger bubbles. Those big bubble is not prone to float, and is constantly hit by recharge water flow. So some of them are burst into small bubbles. Part of the small bubbles can smoothly through the aquifer permeability channel, making some K, is higher than the adjacent value. The final hydraulic conductivity of the aquifer decreased by 19.60 % at the end of the micro-air bubble water recharge. While the value of hydraulic conductivity of the aquifer decreased by 28.63 % at the end of the aeration water recharge. It is means that the more gas in the recharging water, the lower hydraulic conductivity of the aquifer would decreased, also the gas clogging would be more than serious in this case.As a matter of fact, this experiment was time-consuming and had strict requirements with the long-lasting measure of aquifer outgoing amount and the water level. Therefore, a set of full-automotive recharging equipment was designed to reduce the work load. Finally, according to the analyzing of the research data and realities of situation, practical recommendations were put forward to prevent gas clogging. |
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