Research On Optimizing The Efficiency Of The Vacuum Dewatering Wells Pumping

Vacuum pumping as a precipitation technique,because of its high efficiency,low cost iswidely used in the foundations and underground engineering construction.Vacuum pumping,a method use the vacuum generated by the vacuum pump to drawgroundwater,which rapid discharge of free water between soil particles and to achieve thepurpose of rapid consolidation.This paper through soil column tube experiments and orthogonal experiments to studythe efficiency of several factors that influence vacuum pumping（mesh，the degree ofvacuum，particles），find the best combination of the factors，use the Visual MODFLOWsoftware numerical simulations to find the variation of water in the vacuum pumpingprocess.By Subway Line14Jiangtai station vacuum pumping monitoring to detect the effectof the best combination. Experiments results are as follows:1. Different volumes of air through the soil while brought out in the free water which inthe soil. The soil column tube experiments was divided into two parts，the first part isunconfined（both ends are opening），the second part is confined that one end in the soilcolumn take different lengths of air tube，one end of the sealed and the other end pumpingair. Experimental results show that with the increase of the length of the air tube the amountof water increases，and increasing the amount of water loss is also expanded substantiallyexponential growth，this result Description soil better connectivity with the outside world, thegreater the amount of water loss.2. orthogonal experiments is the study of a number of factors multiple levels of a designmethod can greatly reduce the number of experiments. By the amount of water and the watercontent of the soil particles two indicators to determine the best combination of three factorsthree levels of each factor. The experimental results show that the precipitation effect is muchbetter in coarse sand，the nonwoven fabric is suitable to select50projects，the degree ofvacuum in the reality production is preferably0.04~0.06MPa， if the vacuum is too high，the rate of drainage sand significantly increased，there may be buried in the pump.3. Visual MODFLOW software simulation ordinary wells precipitation and Vacuum pumping precipitation，and compare precipitation effect. And give the water line variation ofthe vacuum pumping.4.Application by the conclusions obtained from experiments to Subway Line14Jiangtai station vacuum pumping monitoring， describes test site conditions, the testequipment and test methods，Monitoring results showed that the out water of one singlevacuum pumping well reach about1.7times the ordinary wells，the influence radius is about9m，variation of the soil pore water pressure and changes of the vacuum is similar，Thehorizontal cross section is formed a concentric circles the center is the vacuum pumpingwell，In the vertical cross section also formed a precipitation funnel and the he vacuumpumping well as the center.