Experience in strengthening foundations and foundations on technogenic soils

The article discusses modern methods of strengthening foundations on artificial bases that have received excessive precipitation and rolls. In the course of studies, it was found that the use of bored piles allows transferring the load to the underlying reliable foundation at any depth, and cementing the foundation soil contributes to improving the physical and mechanical characteristics of the backfill soil

Interaction of drill-injection piles with the surrounding soil

Nowadays, there is an active use of drill-injection technologies for pile foundations creations both in civil and industrial construction. There are many drill-injection piles technologies which application depends on geotechnical conditions, loads, buildings and constructions purpose, technical and resources sufficiency and others points. Drill-injection piles producing occurs stress-strain state modification and physical and mechanical properties modifications in surrounding soil massive. Detection of features of soil properties modifications in drill-injection pile surrounding region allows to improve drill-injection piles bearing capacity calculations methods and to get more exact results. The article contains the analysis of physical and mechanical properties modifications in the South of Tyumen region (Russia) soils which surround drill-injection piles «Normal». The definition of soil properties was done by experimental investigations during the excavation of the piles to the depth about 3.5 m in the site investigation with known engineering and geological conditions. There was detected the 6 – 10 % increase of soil density in 60 mm distance from the piles wellbores which depends on the soil type and increase of soil humidity in the waterless zone due to the high cement mixing-water ratio of the cement mortar. Also it was found the increase of soil deformation characteristics up to 17.4 % and soil strength characteristics up to 27.3 % in relative to the original values. To the results of excavation of the piles it was discovered the wellbores expansion up to 4.4 % and local wellbores expansions in relative to the original values. During the inspection of the drill-injection piles there was discovered some piles defects such as massive soil penetration into the pile shaft near its wellhead and soil and mortar mixing along the perimeter of the piles owing the insufficient mortar density and its high shrinkage. According to the results of the experimental researches further investigations problems were defined