Basically, according to international standards, the use of sand columns in very soft and soft soils with undrained adhesion strength is limited to less than 15 kPa. On this basis, cement slurry injection in sand columns implemented in soft cohesive soils is one of the solutions to eliminate Fracture of the sand columns and using the maximum compressive bearing capacity, the subsidence decreases and the stiffness modulus of the sand column increases. Despite these advantages, the drainage of the cemented sand column is reduced. In the field, for the implementation of a cemented sand column with uniform conditions, it is important to study the depth of injection process in laboratory and field conditions and to determine the optimal ratio of water to cement slurry.
During this research, in laboratory conditions, 30 cubic samples (15x15 cm) and 30 cylindrical samples (15x30 cm) cemented sand with a ratio of water to cement of 0.45, 0.5, 0.8 ,0.6 and 1.0 respectively. for each water-to-cement ratio, 2 x 3 replicate samples to determine the unconfined compressive strength at the ages of 7 and 28 days, and 6 cube samples and 6 cylindrical samples, 3 x 2 replicate samples with a water-to-cement ratio of 0.6 were made to determine the unconfined compressive strength at the ages of 56 and 90 days. Also, in order to study the behavior of cemented gravel under compressive loading, to determine the stress-strain curve and to determine the modulus of elasticity of cemented gravel, 1 cylindrical sample of 15x30 cm was made and tested at the age of 28 days. In addition, the gravity injection performance of grout with different ratios of water to cement were investigated in laboratory conditions.
The results of the analysis indicate that with the increase of the water-cement ratio from 0.45 to 1, the 28-day compressive strength of the cylindrical sample of cemented sand decreases from 90 to 55 kg/cm2. The ratio of 28-day strength to 7-day strength for water-cement ratios of 0.45,