Key Technology Research On Groudwater Control Of A Deep Foundation Pit Engineering In Spring Enrichment Area

Spring is the soul of the culture as for Jinan city, and the spring rich region that is around Baotu, Heihu, Wulongtan, zhenzhu Four Springs is the cultural and economic center of Jinan city. With the sharp development of economy, construction accompanying with excavation of foundation pit is developing at unbelievably fast rates. As a result of it, it leads to a huge loss of underground water resources and poses threat to spewing of the springs. Therefore, it requires us to develop the technology on the regional groundwater control and find a balance between the construction of modern city and the protection of underground water resources.Firstly, this paper analyzes and summaries the typical geological conditions in the water abundant region. According to the typical geological conditions, it analyzes the interaction between the groundwater and the construction of foundation. Following, it summaries the groundwater control measures often used in underground water rich region. Then, it uses the finite element methods to simulate the reasonable and economic waterproof curtain depth, the rational precipitation well space, the rational layout and measures of recharge well respectively. Finally, combining a certain deep foundation pit engineering in this area, it optimizes the measures of underground water control from dewatering, water stopping, recharging aspects and shows the final results:(1) In the case of uneven distribution of gravel soil in the region, it is able to get the rational and economic dewatering well space through simulating in the cases of thick gravel soil and thin gravel soil, and setting the change of water level in dewatering well. For example, the excavation depth is 8 meters and the dewatering duration is 3 months; it is almost able to make sure the economic and reasonable well space: as: D≤6.5m, then S≤20m 6.5m≤D≤8.0m, then 20m≤S≤25m D≥8.0m, then S≥25mNote:D-the thickness of gravel soil S-the space dewatering well(2) By using of seep/w professional seepage analysis software to simulate the situation of seepage field under the three cases:without sealing curtain, curtain sealing the bottom of gravel soil, and water proof curtain locating at the tips of residual soil; it is able to get the typical stratum structure in the underground water rich region:gravel soil buried shallow and thin. Also, extending the sealing curtain into the residual soil layer can not only ensure the safety of the surrounding environment but protect groundwater resources as well. Therefore, it is an extremely economic and security depth.(3) As for the case of the heavy thick of fill soil in local spring water rich region of the old town and the serious impact on the surrounding environment during dewatering. It uses seep/w flow module and sigma/w stress and strain modules to simulate this situation. It shows the results:the settlement amount declines with the increasing distance away from the curtain; the surface largest settlement appears near the row of piles and decreases with the increasing distance away from the curtain; through simulating the process of dewatering, it comes a result that 80% consolidation settlement completes in two months after dewatering and the settlement amount becomes small, consolidation rate goes down later period. Therefore, it requires us to do much more monitor at the beginning two months.(4) According to the environment surrounding surface subsidence changes by simulating that recharge wells are at different distances away from sealing curtain spring water rich region, it comes:it is more effective to control the change when recharge wells are near the object to be protected and away from the curtain.(5) Compare to the method of recharging wells after the pit outside the drawdown over perennial level, the method of recharging wells and dewatering at the same time is more effective to control the changes of surrounding area. Even though it is limited to control the changes of surrounding area, it is useful to control the uneven settlement.(6) Combine with one certain deep excavation in spring water rich region, compare and verify the numerical simulation to determine reasonable and economic feasibility of the depth of the water sealing curtain; optimize the dewatering well space for the problems of dewatering and drying in the engineering; base on control settlement, propose the recharge wells layout.This paper analyzes the data and researches the key technology of controlling underground water in underground water rich region, gives the reference measures and recommendations to regional groundwater control and guides the construction.