Abstract:

Artificial recharge is an important engineering measure to improve the level of water resource utilization. However, the clogging in the process of injection will affect the efficiency and service life of the infiltration. In order to study the theory of the clogging and to control it, experimental sand columns were used to simulate the clogging process during groundwater artifical recharge, and the saturatedunsaturated change induced by clogging was analyzed. In the test, the outflow rate increased quickly to a peak value followed by a rapid decrease, and then decreased slowly, i.e., only after 72 h of injection, the flow rate of sand column reduced to 2.18 m/d; the outflow rate of the sample decreased slowly after 72 h; the sample outflow rate was 0.81 m/d after 192 h, about 1/10 of the maximum outflow rate. The results showed that the basic reason of clogging was the permeability reduction caused by suspended matter filling the void volume of the sand and the silt layer formatted by suspended matter deposition. The formation of the silt layer was the key reason leading to the sharp decrease of the outflow rate. After the silt layer formatted, the weak permeability of it caused the water content change of the sand from upper to lower, which lead to the decrease of both hydraulic conductivity and hydraulic gradient, as a result, the outflow rate decreased rapidly. The 10 groups contrast showed that, considering the rain flood infiltration system blocking of various factors, the experience model to calculate the infiltration rate in non-gravel filter material rain flooding injection process was constructed and the fitting results decisive coefficient is 0.932.

Key words: artificial recharge, stormwater infiltration, clogging, saturated-unsaturated seepage, outflow rate, non-linear generalized least squares