Specifics of Seismic Intensity Changes When Applying the DSM Method to Strengthen Construction Site Foundations

Abstract This paper presents the results of engineering–geological and geophysical investigations aimed at improving the seismic resistance of construction sites on collapsible loess-like soils. These soils, common in arid and semi-arid regions, are highly porous, structurally unstable, and prone to subsidence, especially under seismic loading. The study evaluates the effectiveness of Deep Soil Mixing (DSM), which strengthens soil by forming in-situ soil–cement columns. The research was conducted at a construction site in the Almazar district of Tashkent, where weak loess-like loams dominate. A total of 218 columns (1 m diameter, 21 m depth) were installed, forming a reinforced ground mass with improved stiffness and bearing capacity. As a result, soil density increased from 1.75 to 2.10 g/cm3, porosity decreased from 43% to 36%, and the deformation modulus rose from 5.5 to 35 MPa. Seismometric analysis using the H/V (Nakamura) method showed that the initial seismic intensity increment (+0.5) was reduced to zero after treatment. The site was classified as seismic category II with a design intensity of 8. The results confirm that DSM is an efficient, reliable, and cost-effective method for improving weak soils under seismic conditions.

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