Cementation of soils by wristband-pipe injection technology in conditions of thawing perpetually frozen soils

Abstract

In the conditions of global warming of the climate in the territories of permafrost distribution it takes place the processes of increasing the temperature of perpetually frozen soils and increasing the depth of their thawing. These factors lead to a decrease in the structural safety of the buildings and constructions. Measures to return soils to the frozen state are not always feasible and effective. In such conditions the solution to the problem of decreasing the pile foundation bearing capacity can be the ground strengthening by the cementation using the wristband-pipe injection technology. In the article it is presented the experience of assessing the current technical condition and designing of bases and foundations strengthening of a three-storey residential building in Yamal-Nenets Autonomous District, village Muzhi. The object was given a limited-operational category of the technical condition due to the deficit of the pile foundation bearing capacity. To bring the constructions of the object to the working condition the project of pile foundation strengthening with the cementation by wristband-pipe injection technology was developed. While injecting the soil foundation with the hydraulic fracturing the additional (induced) tension state appears, and it changes the deformation and strength properties of soils, voids ratio, index of liquidity and modulus of deformation. Reinforced joints, soil compaction and stabilization appear due to the injection. While making the hydraulic test and fracturing in the soil body its stress and strain state is changing, foundation piles are stressed with the additional lateral pressure. Besides the soil is strengthening under the pile toe bulb. Analytical calculations are given for increasing the bearing capacity of a pile during cementation of soils due to the increase of horizontal stresses and the work of compacted foundation soil on the lateral surface and under the lower end of the pile.