Interaction of drill-injection piles with the surrounding soil

Grounds and foundations, underground structures

Nowadays, drill-injection technologies are actively used to create pile foundations in both 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 other 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 of about 3.5 m in the site investigation with known engineering and geological conditions. There was detected a 6–10 % increase of soil density in 60 mm distance from the pile 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 % with reference to the original values. To the results of the 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 to the insufficient mortar density and its high shrinkage. According to the results of the experimental researches, further investigations problems were defined.