METHOD OF ELIMINATING SUBSIDENCE AND REDUCING SEISMIC LOAD ON FOUNDATION OF STRUCTURE ERECTED ON SUBSIDENCE SOILS IN SEISMIC AREA Russian patent published in 2024 - IPC E02D27/34 

FIELD: construction.

SUBSTANCE: invention relates to construction, in particular, is intended to eliminate subsidence of a building base and reduce seismic load on the base of the building foundation. Method for elimination of subsidence and reduction of seismic load on the base of the foundation of a structure erected on subsidence soils in a seismic region involves arrangement of a compacted cushion of sand-gravel mixtures (SGM) in its base. Method for elimination of subsidence and reduction of seismic load on the base of the structure is implemented in 4 stages. At the first stage, prior to the construction of the foundation of the building, the pit in the subsidence soil, the compacted cushion from the SGM, the works are performed on the initial microseismic zoning of the construction site with the determination of the design seismicity, velocities, lengths of longitudinal and transverse waves Lw, as well as mathematical modelling; then performing initial geodetic high-altitude survey of pit sides, planned breakdown of pit top and excavation of pit with dimensions of contours at pit bottom level not less than vertical projection on it of building foundations outlines, increased in each side by length of segments L_k, beyond which the calculated deformations do not exceed the building foundations allowable deformations at subsidence of the surrounding subsidence soils of the natural structure from their own weight, and the size of the pit on the top is not less than the wavelength during the earthquake L≥Lw; during excavation, slopes of pit of loess clay soils of natural moisture and structure are formed in the form of steps with ratio of height of vertical ledge to horizontal laying within 1:0.75-1:1. At the second stage, the first layer of SGM is backfilled into the pit and compacted; before the beginning of compaction, the moisture content of soils of vertical benches is monitored: when soil moisture content is lower than moisture content at the rolling limit, their graduated moistening is performed from pits made in the SGM layer until soil moisture content is achieved at the rolling boundary within the soaking zones; coefficient of compaction of SGM over the entire area of the layer, including edge zones, is set not less than 0.95, with formation of a compacted outer contour of waterproofing in the form of a water-resistant screen. At the third stage, when the level of the embankment from the SGM of the marks of the top of the first from below is reached, compaction of the filled SGM layer is performed, leaving an uncompacted step, then, soil moisture content of the step is controlled; if necessary, it is moistened from the deepening until it reaches soil moisture content at the rolling boundary, and compacted if necessary, by adding and compacting the SGM to a specified compaction coefficient of at least 0.95. At the fourth stage, alternating actions of the first two stages are performed until the pit is filled with a compacted cushion from SGM on the design mark, thus creating a cushion from a layer-by-layer compacted SGM at the base of the building foundation, having dimensions L comparable to the wavelength during an earthquake L≥Lw, contoured in depth by water-proof screen; then on top of the cushion a horizontal waterproof membrane is laid, a foundation is arranged, performing repeated microseismic zoning and repeated mathematical modelling in order to establish the effect of reducing seismicity of the construction site due to transfer of soils from III seismic category to II; after which a waterproof membrane is laid on the top of the entire cushion, which acts as a water protection of the top of the cushion for the entire period of operation; then performing the foundation; injection compensation tubes for injection compensation with hardening solutions of possible deformations of bases during subsidence of surrounding soils and earthquakes are laid in the edge zone of the foundation for the design width and depth.

EFFECT: improving reliability, safety and reducing material consumption of a building erected on subsidence soils in a seismic area with score of 9 points.

5 cl, 1 dwg