What is Groundwater?
Groundwater is the water in the zone of saturation. The upper limit of this zone is referred to as the water table. The depth to the water table may vary considerably depending on site conditions. The groundwater may be found either in continuous bodies or in several separate strata, and the thickness may vary considerably. Local saturated zones that may occur above the main water table are termed perched water.
Since groundwater conditions have an important effect on design and construction, the regional and local conditions must be studied during the investigation stages so that potential problems may be evaluated. The grouting program should be designed for the existing groundwater conditions as well as for postconstruction conditions. Different methods and procedures may be employed, depending on the formation permeability, the depth to water table, and the type of aquifer present (confined and unconfined). These conditions affect the type of grout, the grouting procedure, the depth and extent of treatment, the spacing of holes, the need for a multiple- or single-line grout curtain, and the pressures that should be used.
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Aquifer conditions also have a direct bearing on the need for and type of drainage required. The chemistry of the groundwater should be considered with respect to the materials to be used in the proposed structure and to the grout to be used. Samples should be tested for pH and the chemistry analyzed. Springs in the construction area may require special treatment, including special grouting methods.