The forecast of an emergency condition of buildings and research of influence on their condition of a nearby building site
Frequently it happens, that as a result of construction works (trenching, driving-in or pipejacking of piles, driving of sheet piles) in walls of the nearby houses arise the cracks, in cellars arise depressions and earth water. Sometimes even there is a destruction of the next houses.
Physics of this influence is next. If under a building there is a zone of the lowered bearing capacity of a soil, and also quicksand (that is characteristic, for example, for St. Petersburg and Northwest of Russia), the influence of the construction works will if the building site will appear within this zone. If as a result of construction works will be issued quicksand, earth water will go out on all its length. Therefore hydro-geological conditions under the house will change, a head by earth waters will be decreased, and the house will begin to subside.
In figure is given the SSP-section of a ground near a southern wall of a house 10 on the Manchester street (St.-Petersburg). On SSP-section is seen funnel-shaped (or V-shaped) object (is shown by red colour). This zone of tectonic failure lies under the house in a submeridium direction. By the similar method was discovered second tectonic failure parallel by first, takes place under neighbour house 12. Both these zones pass under a construction site of a new house. Besides under both houses (10 and 12) the floating earth are located.
SSP-section of a ground near a southern wall of a house 10 on the Manchester street (St.-Petersburg)
During of measurements (January, 2002) the construction of a new house did not begin yet. We made the forecast, according to which digging of foundation pit on continuation of tectonic zones that take place under both houses, will promote an leaving of earth water, that can result in development of an emergency condition down to destruction of both apartment houses.
To middle summer 2002 construction works were begun, and foundation pit was dug. Despite of droughty summer,earth water has appeared in foundation pit , that testifies that the quicksand was disturbed, and its contents began to leak to foundation pit. The formation of cracks was begun in walls of houses 10 and 12 after that.
The similar situation has taken place at conducting works on embankment of the Obvodny channel (see. An example 14).