Foundation pit dewatering is an important step to ensure foundation quality. There are many commonly used methods for foundation pit dewatering, so what about the conventional construction methods for foundation pit dewatering? Bian Xiao collates relevant information, and the basic introduction is as follows:
The construction methods of foundation pit dewatering mainly include: open ditch plus collecting well dewatering, light well point dewatering, jet well point dewatering, electro-osmosis well point dewatering, tube well point dewatering and so on. The details are as follows:
Dewatering in open ditches and collecting wells
Dewatering of open ditch water collecting well is a kind of artificial drainage method. It mainly excludes underground diving, construction water and rainwater. In areas with abundant groundwater, if only this method is used for dewatering, it is more difficult to construct the anchor-shotcrete net support because of more water seepage in the slope of foundation pit. Therefore, this dewatering method is generally not used for foundation pit slope support in high water level areas alone.
Light well point dewatering
Light well point dewatering is suitable for occasions with small foundation pit area and low dewatering level. Generally speaking, the depth of lowering the water level in this way is between 3 and 6 meters. If the depth of precipitation is required to be greater than 6m, a multi-level well point system can be used in theory, but there should be enough space around the foundation pit to facilitate sloping or trench excavation.
Jet well point dewatering
The injection well point system can generate a vacuum of 250 mm Hg at the bottom of the well point, which reduces the water level to a greater depth, generally within the range of 8 ~ 20 meters. Its applicable soil permeability coefficient is the same as that of light well point, which is generally 0. 1 ~ 50m/ day. However, its pumping system and injection well pipe are very complicated, with high operation failure rate and large energy loss, and the required cost is higher than other well point methods.
Electro-osmotic well point precipitation
Electroosmosis well point is suitable for fine-grained soil with small permeability coefficient, such as clay, loam, silt and muddy clay. The permeability coefficient of these soils is less than 0. 1m/ day, which needs to be combined with light well points or jet well points, and the depth of lowering water level depends on light well points or jet well points.
The main functions of base tank sedimentation are:
When excavating a foundation pit, if the groundwater level is too high, if it is not lowered in time, it will not only worsen the construction conditions, cause the soil wall to collapse, but also affect the bearing capacity of the foundation. In severe cases, it may even cause quicksand. Therefore, in earthwork construction, it is very important to do well the construction dewatering work and keep the soil dry, which also improves the working conditions.
However, before precipitation, it should be considered that the existing buildings and structures within the influence range of precipitation may produce additional settlement and displacement, which may cause cracking, inclination and collapse, or cause ground collapse, and effective protective measures should be taken in advance when necessary.
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