Deep strengthening and reinforcement of soils are employed to improve the quality of soils prone to slump-type settlement, fill soils, and other structurally unstable and weak saturated soils. The I. I. Vorovich Scientific-Research Institute of Mechanics and Applied Mathematics at the Southern Federal University has, in conjunction with the OOO NIPP INTROFEK developed a procedure and equipment for deep grouting of soils through directed fissures. Strengthening and reinforcement of the soils is carried out by elements of increased stiffness formed from soil-cement stone [1][2][3][4].The procedure employed for reinforcement consists in pressure injection of an ecologically safe foamed soil-cement grout through directed fissures created when the pressure in the hole is raised with a triangular stress riser. At sites where highly compressible saturated soils of highly plastic and fluid consistency exist, the operations should be carried out under the pressure of a foamed soil-cement grout with a density that eliminates collapse of the wall of the hole and provides stability and shape to the stress riser. Face development is accomplished in a hole filled with the soil-cement grout by a special device with an extensible rotary cutting tool [2,4]. Free recesses exist at the tip of the tool for the passage of grout when the device moves in the hole (see Fig. 1).Geologic-engineering surveys were performed, and strength tests conducted on the reinforced bed to assess the reinforcing effectiveness of the highly compressible saturated soils on the construction site of a Series 90.10-05 ten-story tenement building on Truzhenikov Street in Rostov-na-Donu after the soils had been strengthened.The geologic-engineering section of the site is represented by: − unconsolidated fill soils with a layer thickness of 0.2-5.5 m, which are composed of a mixture of clayey loams and 7-30% of construction debris; − soils prone to slump-type settlement with a layer thickness of 1.0-2.6 m to a depth of 1.2-5.5 m from the ground surface. These soils are exposed in the northern section, and do not spread into the A method is proposed for the strengthening of highly compressible saturated soils by the method of injection through directed fissures. Test results are presented for the reinforced bed of a conventional foundation subjected to static loads. Results of the investigations are being successfully applied to the construction of two ten-story buildings in Rostov-na-Donu.
Methods employed for the artificial improvement of soil properties, so-called "technical reclamation" (stabilization, strengthening, reinforcement), had come into widespread use as early as the 1930s. Sodium silicate, sodium hydroxide, various resins, bitumens, and emulsions based on these materials, which result in heavy long-term pollution of soils and ground water, had been used as soilstrengthening compositions in connection with less stringent ecological requirements.Transformation of weak soils by cement-base compositions, which form alumosilicate compounds similar to those in nature after hardening, is most acceptable from the ecological standpoint. We have developed a method for bed preparation using foamed soil-cement grouts [1].The essence of the method lies in the fact that the bearing capacity of structurally unstable beds is increased by injecting hardening foamed soil-cement grouts into the beds via directed hydrofractures [2,3]. When this grout is delivered, the soil mass is simultaneously moistened, compacted, and reinforced. Grouts of the following composition are used (% of solid phase): 10-70 of cement, 90-30 of soil, and 0.05 of surface active substance. The amount of water Q H 2 O for preparation of the grout is calculated from the following formula, which accounts for the fact that the mass is brought to the optimum moisture content W optwhere V s is the volume of the soil mass in m 3 , 0.5 is the weight ratio of the water and solid phase in the grout in fractional units, P sp is the mass of solid phase in the grout, which is required to consolidate and reinforce a soil mass with a volume V s in kg, ρ H 2 O is the density of the water, which is equal to 1,000 kg/m 3 , γ dry is the density of the dry soil in the mass being consolidated within the limits of the site in kg/m 3 , and W s is the moisture content of the soil in the mass being compacted in fractional units. 2 2 2 sp dry s opt s 0.5 ( ) H O H O H O P V Q = W W , γ ρ ρ − A means of reinforcing beds by the method of grouting through directed fractures, which has been successfully used to stabilize soils in the foundation beds of buildings and structures in the Rostov Oblast, is described. A method of quality control is proposed for the soil cement on the basis of disturbed samples.
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