Pressure and water reduction construction method of ultra-deep foundation pit confined water

Abstract

The invention relates to a pressure and water reduction construction method of ultra-deep foundation pit confined water, which is characterized in that field survey and test are performed to obtain the osmotic coefficient of a water-bearing stratum in the field, the quality of a formed hole is ensured by adopting a gas-lift reverse circulation guide pipe, a well casing structure is optimized, the geological conditions of the field can be adapted with a short filter, a tap is ensured to be deeply descended, and the water discharging amount is ensured at the same time. The invention has optimal water reduction effect, reduces influence on peripheral environments without high-power pumping equipment in the water reduction process, reduces energy consumption reduction, is convenient for construction and is especially suitable for the field with a thicker pebble layer, higher permeability and abundant water amounts.

Description

technical field [0001] The invention relates to a decompression and dewatering construction method of ultra-deep foundation pit pressurized water, especially a decompression and dewatering construction method for the pressurized water of the round gravel layer with strong permeability and rich water volume, and reduces the total displacement and lift The decompression precipitation construction method of precipitation effect. Background technique [0002] In the construction of the first shield tunnel crossing the Qiantang River in Hangzhou, the excavation depth of the foundation pit is nearly 30 meters. In order to solve the problem of decompression and precipitation in the pebble layer with strong permeability and abundant water in the Qiantang River area, a pumping test for confined water treatment was carried out on site, and dewatering wells were drilled at appropriate positions. Crushed boulders and pebbles, reamed with a large drill bit, added a small amount of lime ...

AI Technical Summary

Problems solved by technology

[0003] Finally, the suspended water-stop curtain is used in conjunction with the decompression construction method of the dewatering well. The construction of the dewatering well is to use the positive circulation method of crushing round gravel and adding bentonite and wood chips to discharge the sediment at the bottom of the hole, which will easily cause the water permeability of the hole wall to suffer. If the damage occurs, the water output of the filter pipe will decrease. The general silk-wrapped filtration method has a small porosity and causes a large loss of water head near the well pipe, thereby affecting the precipitation effect. At the same time, a longer filter is installed on the precipitation well, resulting in precipitation The impact depth of the well is deep, the scope is large, the total water inflow of the foundation pit is large, and the suspended water-stop curtain needs to be inserted deeper into the aquifer to produce an obvious flow-around effect, but the deeper water-stop curtain is constructed in the boulder layer It is difficult and costly. In addition, the pressure head required to be reduced in the construction of deep foundation pits is relatively large. Long filter pipes are used, and the drainage volume is large. It needs to rely on high-power pumping equipment, which requires high power supply and drainage. , the actual operation on site is very difficult, and the general short filter tube has the problems of small cross-sectional area and fast flow rate, which will cause a large head loss in the dewatering well and fail to meet the requirements of decompression and dewatering

Images