Use of disturbed samples for quality control of soil cement

Abstract

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.