چكيده به لاتين
Pressurized injection, also referred to as jet grouting, is a method of soil improvment in which highly pressurized grout is injected at a high speed into the soil from nozzles. This procedure tears down the soil structure and creates a soil-cement column. One of the most prominent challenges in regarding the use of this technique is ensuring that the columns are formed in a predetermined geometrical shape (regarding their form and diameter). In order to ensure that the columns are created following a definite diameter, an innovative procedure in jet grouting may be utilized within a sheath or mold that encloses the soil Which will be similar to two-stage concrete, except that in two-stage concrete, the empty space between the aggregates in the formwork is filled with low-pressure injection of grout, while in the enclosed cement soil column, the method of mixing aggregates with grout Is jet grouting.
The present study investigates the physical and behavioral characteristics of such enclosed columns with diameters of 15, 20, and 25 cm made using 161, 131, D1, D2, D3 Firuzkuh sands. Furthermore, the effect of reinforcement on the formation of columns and its quality, aggregate shadowing, and flexural fractures has been scrutinized.
Based on this study, grain diameter size in the jet grouting technique affects the mechanism during which the column is formed. It is possible to state that the mechanism in coarse-grained soil has been penetration, and the mechanism in fine-grained soil has been erosion. The soil-cement columns created by the erosion mechanism have a smaller diameter, higher cement concentration, and higher strength in comparison with the soil-cement columns which are created using the erosion mechanism. An increase in the diameter of the enclosing mold ultimately reduced the compressive strength.
Soil grain diameter affects porosity, the scant modulus elasticity, and the mechanism during which the column is created. In a fixed mechanism however, no significant effect was identified on the compressive strength of the column And the compressive strength range in the penetration-erosion mechanism is 15 to 18 MPa and in the erosion mechanism is 38 to 40 MPa. The beta coefficient is in the range of 180 to 520 for the main samples and in the range of 80 to 300 for the core samples. Aggregate shadowing behind the rebars was not observed in reinforced samples in soils with coarser grains that apply the penetration mechanism. However, the aggregate shadowing effect behind the rebars has been clearly evident in finer soil that applied the erosion mechanism.
