چكيده به لاتين
Ground improvement is used as a set of methods to improve the efficiency of loose and inappropriate soils in terms of bearing capacity. Jet grouting method (high-pressure injection) as one of the most efficient improvement methods has a special place among all the methods. The basis of jet grouting technology is the injection of one or two high-pressure fluids into the soil. Hydrodynamic action of the jet breaks down the primary structure of the soil and comes out part of the soil along with the slurry portion and mixes the rest of the soil with the injectable fluid. This results in the formation of soil-cement bulk in the soil, which is in most cases cylindrical.hence, they are called jet grouting column.
Physical modeling is a suitable method for clarifying the operation of high-pressure injection in peripheral soil and for obtaining details of this process. In this study, to investigate the behavior of high pressure injected columns, a laboratory micro-jet grouting device at the Geotechnical Research Center of the Iran University of Science and Technology was used. Then, by implementing columns with different parameters, the impact of rotational speed, injection time at per step, injection pressure and flow rate, lifting step, withdrawal speed On resistance and geometric characteristics of the soil-cement columns were investigated.
Based on the results, increasing the rotational speed causes to decrease the diameter and with increasing injection time at per step, the diameter of the columns increases, but the slope of increasing the diameter gradually decreases in order to increasing the injection time, the diameter remains constant and only The injected slurry replaces the remaining soil in the column more . Increasing the pressure and flow rate will increase the diameter of the columns. Also, increasing the distance between the stops reduces the diameters, but by increasing this distance and reducing the effect of successive injections on the next step, the diameter reduction is stopped, and the diameter remains constant. Besides, the speed of passing the distance between the stops does not affect the diameter of the columns.
Regarding the resistance characterization, it can be stated that increasing the injection time slightly increased the resistance, but rotational speed changing did not have much effect on the strength of the columns. Also, compressive strength for cores with a diameter of 4.4 cm and a height of about 8.8 cm is 25 to 30 Mpa.
