The need for a basement in big cities is increasing. The problem is how to dig for the purposes basement floor can be done safely, both for the benefit of the project and the surrounding environment. Because some digging basement floor typically involves dewatering work that if not properly handled can cause impacts are not expected. There is the impression that the use of dewatering pumps just suck ground water, so that it can be implemented just like that ?
To perform excavation groundwater knowledge of the responses required for the following matters:
a). To estimate the flow will occur in a quarry (capacity suction pump and so on)
b). Assessing the impact of seepage (seepage) groundwater on the stability of the excavation
c). Determine what the effect of changes in ground water level caused by excavation of the surrounding environment, especially against the settlement. Other things, such as the drying up of wells in the vicinity, and so forth.
Excavation below groundwater level on many types of fine soil does not pose any difficulties and excavation can be done without the need for special measures. The edge can be made stable slopes and seepage can be allowed to flow freely from the slope to the bottom of the excavation. Seepage will only affect excavation slope stability but does not affect the basic stability of the excavation.
For the excavation site that constraints can not be done “an open excavation”, could use a sheet-pile or as a soldier pile retaining structure. If the structure of the retaining walls are not watertight, then seepage water can pass through the crevices of retaining wall. However, if the wall is impermeable or nearly impermeable, then the problem of the basic stability of the excavation is a problem that needs to be considered in estimating the style of seepage / uplift.
Wellpoint system is widely used for excavation below the groundwater table in the sandy soil. Wellpoint connected to each other with a pipe at the top, then connected with a suction pump (suction pump). The water is then sucked through the pipes and lowering the groundwater level.
Deep well can be used on deep excavation, the reduction in the water level is done in bulk. The well has a large diameter. A large diameter allows installation of submersible-pump at the bottom of the well. Because the pumping is done at the bottom of the well, the depth of the well is not limited by atmospheric pressure, but only determined by the capacity of the pump. Distance deep well generally range of from 8 m to over 50 m.
In addition to the considerable investigation, a thorough understanding of the mechanics of seepage and good judgment is needed to determine excavation technique and dewatering suitable. In some situations, dewatering work may require changes when construction is taking place, especially on complex soil conditions and accurate measurements of the permeability in the field is not possible prior to excavation.