Laboratory Research On The Influence Factors Of Suspended Clay Solids Clogging During Artificial Recharge

In China, due to the spatial and temporal uneven distribution of water resource, less per capita resources and surface water pollution et al, groundwater becomes the main available resources. With the mining strength increasing, water resources shortage is becoming more and more serious, groundwater recharge becomes an effective method in dealing water resources shortage issue. However, this technique cannot be widely adopted because of uncertainty clogging behaviors which are caused by suspended materials. Therefore, sound understandings of clogging mechanism both in theory and practice are urgently needed.This paper used high purity quartz sand as media and clay as suspended material, analyzed of recharging water quality,and the law transportation and deposition of suspended particles and the permeability of porous media was studied in different factors through the artificial recharge simulation experiments and a series of sample analysis and test technology under constant flow condition, such as porous media size,suspended particle size, suspended particle concentration and seepage velocity et al. Then it summarized methods of suspended clogging prevention and control. The main conclusions of this study could be described as follow:(1) Porous media size determines the trafficability characteristic and deposition attachment space of suspended particle. Porous media size is bigger, media porosity is larger, the trafficability characteristic is better, the deposition attachment space of suspended particles is bigger, then the time is longer reaching the same degree of clogging.(2) The deposition structure of porous media is the main factor affecting the deposition position of suspended particles. When the upper is coarse particles and the lower is fine particles, there is an obvious depositional inflection point at media interface, here the rangeability of permeability coefficient is the largest and the clogging produced easily; When the upper is fine particles and the lower is coarse particles, the suspended particles is mainly deposited on the surface of the porous media, and the degree of clogging decreases with increasing depth.(3) Suspended particles size is the main factor affecting the transportation ability of suspended particles in the recharging water. The larger the suspended particle size, the shorter suspended particles transport and the more surface filtration action takes place, lead to surface relative permeability coefficient has dropped dramatically; The smaller the suspended particle size, the father suspended particles transport and The permeability of deep porous media can also change significantly.(4) Suspended particles concentration has a critical phenomenon affecting clogging. The bigger Suspended particles concentration is, the greater the peak value of the suspended matter concentration is and there is an increasing trend in the total amount of suspended solids in the unit time; But with the increase of the concentration, the difference of the amount of suspended solids in the unit time is decreased. In the distance to the porous media surface of about 6cm below, the suspended solids concentration of 500mg/l and suspended solids concentration of 1000mg/l of the total deposition and deposition rate is similar. In the condition of constant flow and the characteristics of the suspended particles, the influence of the concentration of suspended solids on clogging has the threshold limit.(5) Seepage velocity affects the attachment ability of suspended particles. With seepage velocity increasing, hydrodynamic force increases and depositional suspended particles transport easily from the column, so the peak of effluent suspended particles concentration becomes big and the time becomes short. With the seepage velocity increasing, the peak difference became smaller, so seepage velocity has a critical value.(6) The influence factors of clogging types and clogging rate have been analyzed synthetically. The distinguishing criteria of clogging types were established through analyzing the clogging experiments of suspended solids under different factors. The clogging types were determined mainly by particle diameter ratio and seepage velocity, and the clogging rate was affected by many factors including particle diameter ratio, suspended particles concentration and seepage velocity.