Apllied Research On Technique And Method Of Well-completion In Special Section Of Beijing Subway Dewatering Engineering

Along with the rapid development of Beijing rail transit, the metro construction sites are blooming everywhere throughout the city while the problems of metro dewatering engineering have gradually become a heated issue. The course of metro constructed recently covers extensive range in Beijing. Thus, we've met problems such as complex geology, house removal, digging difficulties, excessive red tape,noise disturbance, citizen's interference which led to well completion difficulties and passable penetration quality. Besides, traditional dewatering machinery failed to meet the need in these metro lines, gave rise to higher cost and prolonged construction time.Concerning the above-mentioned issues, this paper refers to the dewatering engineering projects of 8th section of line 6 and 12 th section of line 14 in Beijing based on the specific geological conditions and external affecting factors. The condition in 8th section of line 6 is rich in gravels and aquifer. Reverse circulation drilling give rise to slurry leakage and hole collapse. After applying down-the-hole hammer, good at cutting rock stratum, we succeeded in drilling and pore forming with?110 casing, dropping ?100PVC tube, which were able to pump at the speed of5m3/hour. At the same time, it was used to measure water level. But the quantity of water output could not meet the need of requirement because the aperture is not big enough. Then we enlarged the casing, drilled and formed pore with ? 183 casing,dropping ?140PVC tube, finally reached the basic line of design requirement at the speed of 20-32m3/hour. For further application research, we customized ? 273 casing and suitable drill, formed pore, dropped ? 200 PVC tube, and the water flow of a single well was over 50 m3/hour.The region from stop Shilihe to Balidian South in 12 th section of line 14 was planned to be dewatered by subsurface tunnel. But it failed to implement in's induced by excessive compensation. It was solved by the vacuum well dewatering in the tunnel, well points are set evenly, aperture is 100 mm, ?80 tubes were adopted, waterwas pump at the speed of 7.5m3/hour, which dewater groundwater under basal layer.This paper introduced new technology and application of dewatering according to two typical metro dewatering engineering and also analyzed the pros and cons of traditional dewatering engineering. Meanwhile, as a referral to help colleagues broaden their thoughts while in similar troubles, improve the efficiency of construction and save costs of the project.