Loess The Diving Layer Sham Tseng Precipitation Computation Model And The Precipitation Of The The Heihe Shaoling Highland Tunnel

With the development of the economy, constructions for large buildings with deepbasements,subways, tunnels,and many other structures often require the excavation ofsoil and rock to substantial depth below the natural water table. The problems aboutdewatering become more and more important. Now, the feasibility of dewatering planis tested by experiential formulas or TaiSi's two dimensional law, thus big errors maybe resulted. This paper studied systematically the problems about dewatering throughdeep well pumping in thick phreatic water of loess. Some preliminary results arefollowing.I arranged data with well pumping tests in Shao Ling Yuan and sum up the laws offlows under the condition of deep well pumping in thick phreatic formations loess,which showed that, under a certain condition of pumping, the product of water table ina dot and the thickness of aquifer in this dot vary with pmping time by logarithm. Ianalyzed the law of well loss, if the rate of pumping is very large, water spring mountsto maximum in a short time,then with pumping extending well loss becoms smallslowly, if the rate of pumping is small, well loss becomes big gradually in a long time.The reserves of water in pumping well influence the change of well loss considerably.On the basis of experimental data, I set up corrective TaiSi's model and studied themethod of parameters settlement in the model. The comparison with the calculatedresults and experimental data showed that the model is feasible and the method ofparameters settlement is correct. The experiential formula can be used into similardewatering projects in the other loess region.Pumping with group wells in loess, flows in formations surrounding group wells arethree dimensional obviously. With time of pumping, the thickness of phreaticformations become smaller and smaller. But when we calculate water table usingTaiSi's formula, we consider flows as two dimensional flows, the thickness as constant.Considering above facts, I set up three dimensional flows model through deep wellpumping in thick phreatic formations of loess in this paper.I made three dimensional program with computer language C++, in which thehandle of pumping wells were very difficult. In previous two dimensional programs,wells were simplified a dot. The rate of pumping was considered that it was pumped outof this dot. According to my practice, water table calculated with this method is oftenextraordinary. Now in three dimensional programs, this problem has not been answeredyet because of wells cutting across many elements. In this paper, I attempt to considerthe group wells as many empty elemats. Using this program, we can calculate watertable every place in computing region, study the law of fiows, answer the problemsunder group wells pumping in every boundary condition, predict water table, gulde theprocedure of eation, evaluate the feasibility of dewatering plan, and revise thedesigned dewatering program. I calculatd the problems of Shao Ling Yuan with thisprogram and compare the calculated results with the experiential results. from whichshowed that the model accord with the law of flows under the condition of deep wellpamping in phreatic formations of loess and the program are correct.