Abstract
<jats:p>The calculation of bases and foundations of reconstructed buildings on sandy and clayey soils requires taking into account the value of the design resistance of the soil R. It is known that in the process of long-term operation of buildings, soil under the footings becomes compacted due to pressure from the foundations, and their properties usually improve. Over this period, the value of R also increases, and in the following we will call it the calculated resistance of the compacted foundation soil Rcomp. The authors have analyzed known methods of determining Rcomp, published by Russian scientists over the past 50 years. The purpose of this work was to refine the method for determining the value of the design resistance of the compacted soil Rcomp for the design of foundations for reconstructed buildings. Among the considered ones, the most effective is the engineering method of determining Rcomp based on the recommendations for calculating the value of R according to the formula (5.7) of SP 22.13330.2016, which is supplemented by coefficients that take into account changes in the physical and strength characteristics of soils. The greatest increase in the value of R to Rcomp (by 45-60%) is observed for shallow foundations on clayey low-plastic soils, while the smallest increase occurs in cases of ground water saturation during the operation of the building (by 20-25%). However, if the additional loading p from the foundation is insignificant (p/R ≤ 0.6-0.7), then the value of R (for uncompacted soil) decreases by 10-15% and more. The greatest compaction effect for clay soils during the building’s operational life occurs when the pressure at the footings p is 80% or more of the calculated soil resistance R (p ≥ 0.8 R). All these factors must be considered when determining the reserve strength of the foundations of reconstructed buildings.</jats:p>