Gravity water in the first surface level of the earth, located in a permanently existing aquifer - is groundwater. They are distinguished by the fact that their surface is free, there is no continuous roof made of waterproof rocks above it. They are located in weakly cemented and loose rocks. They can fill cracks in sedimentary cemented, metamorphic or igneous rocks, and also occur in Quaternary sediments. Groundwater, according to its occurrence, is classified into several types: stratal, fractured, and pore. Their formation occurs due to the infiltration of surface water and precipitation. The area of their location most often coincides with the distribution of the aquifer, the thickness of which is not constant, but depends on the intensity of nutrition, the distance to the discharge area of water-bearing rocks, etc.
Groundwater has the main characteristic feature that distinguishes them from artesian, deeper waters - the lack of pressure. They are affected by meteorological conditions: temperature, precipitation and pressure, evaporation, etc. Human economic activity also has an important effect : pumping oil and water from the bowels, building irrigation and drainage facilities and hydraulic structures, fertilizing agricultural land, mining, etc. In addition, hydraulic conditions are important: changing the regime of draining, supplying and surface water bodies.
In construction, groundwater causes damage, destructive effect on concrete and other building materials. Before starting the design of structures, it is necessary to conduct a study of the territory, with particular attention to the presence, nature, chemical composition (aggressiveness) of groundwater, as well as to the expected water inflows. Aggressiveness is determined by the solubility of calcium carbonate and evaluated by the following degrees: total acid, leaching, magnesia, sulfate and carbon dioxide.
For the national economy, these waters are of great importance, being a source of water supply for settlements, industrial facilities, etc. They are produced by drilling wells and wells with gravel dumping, combining with nets of galunny weaving. Why are they dangerous? The presence of groundwater limits the implementation of individual construction processes, for example: the choice of foundation, the presence of a basement, basement, cellar or septic tank.
Groundwater in the basement slows down the process of excavation, as they erode the soil and make it impossible to conduct construction. The walls lose their bearing capacity due to the fact that the caissons of basements and cellars are affected by hydrostatic pressure, and leak tightness is lost. Ground water in the basement significantly affects the strength of the foundation, and in addition, additional protective measures are required: isolation from damp capillary moisture at the floor level, wall protection with double plastering with plaster, hot bitumen or mixed cement mortar with the addition of hydrosite. From pressure water, buildings are protected by drainage and water intake, as well as by creating a waterproof shell of the walls and basement floor.
Groundwater level determination begins with the location of an aquifer. On a flat surface or area, it is the same everywhere, and with irregularities, the level goes higher in elevated places and lower in lowlands. Usually they are located at a distance of up to 20 m, in wetlands - up to 1 m. If the water in the territory fills small depressions, then its level is above the surface of the earth. In rainy weather, their level rises, and with drought - decreases.
Groundwater level determination is of utmost importance for the construction and foundation laying. The bearing capacity of the soil will depend on this. If the level is too high, pouring the foundation is strictly prohibited.