Shekhorkina N. Strengthening of foundation bases composed of fine-grained unconsolidated sands by high-pressure cementation

The object of study - the interaction of the cement slurry that is pumped under pressure, with loose sand and the changes of bases characteristics by pressure. The aim of the thesis is the development of theoretical foundations and algorithms for calculation the operation factors of fine-grained loose sand injection of cement slurry with high pressure. Methods: similarity theory and dimensional analysis, visual method of soil spatial structure study after cementation, standard laboratory methods for determining soil characteristics, methods of mathematical statistics, numerical modeling techniques, methods of foundations deformation. Theoretical and practical results: first obtained the criterion of approximate physical modeling of soil cementation process for establishment of the convergence model and full-scale dissemination of injection radius, were developed further experimental studies to determine the regularity of solution spread and the changes of fine loose sand humidity and density after cementation depending on the determining factors, namely, water/cement ratio of solution, the type and dosage of plasticizer and the initial humidity of sand, first developed the algorithms for calculation the operation factors of fine-grained loose sand injection of cement slurry with high pressure, such as stresses and displacements in the ground, pressure of injection and radius of injection, soil density, first obtained the empirical coefficients for calculation formulas that take into account the influence of plasticizer type and dosage on radius of injection. Scientific novelty: the criterion of approximate physical modeling of soil cementation process for establishment of the convergence model and full-scale dissemination of injection radius (first obtained), the algorithms for calculation the operation factors of fine-grained loose sand injection of cement slurry with high pressure (further developed), based on experimental investigations of sand cementation obtained empirical coefficients for calculation formulas that take into account the influence of plasticizer type and dosage on radius of injection (first obtained). Degree of implementation: the results were used in the design and implementation of bases strengthening and foundation balancing of vacuum station №1 and №2 cementation with high pressure in the area of steel plant "Dniprostal". Scope of use: in the design organizations in the design and the implementation of fine-grained unconsolidated sand bases strengthening.