Experience of carrying out of ground-cement elements on the jet grouting technology in slags of a blast-furnace process

Abstract

The article describes the first experience in Ukraine in the implementation of ground-cement columns in the blast furnace slags. In accordance with the project to reinforce the soil base during the reconstruction of the place with a canopy in the station for the production of air separation products with the installation of VRU-1400 in the city of Enakievo, experimental work was performed on the territory of the plant to confirm the correctness of the selected technological parameters of Jet Grouting in the actual engineering-geological conditions of the construction site and control of the geometric and strength parameters of cement columns. Two test ground-cement columns were completed, visual and instrumental examination of the jet columns was performed (confirmation of the cylindrical shape, continuity of the shaft of the excavated part of the jet column, measurement of the actual diameter), the cores were drilled from the body of the jet column in the horizontal direction and the material was tested for compressive strength, as well as core sampling in the vertical direction for the entire length of the jet column, testing of soil-cement material. Based on the results of the visual examination, the cylindrical shape of the jet grouting elements was confirmed and the actual diameters were measured, which amounted to 610 ... 640 mm that is more than the required for the project - 600 mm. The selected vertical core confirms the design length of the jet column, the continuity of the body of the jet column and the absence of gaps in the treatment processing with a high-pressure jet of cement solution. According to the results of laboratory tests of cement-slag cylinders selected from horizontal cores, the strength of the material ranged from 4.76 to 7.68 MPa for 24 days of age and 7.96 MPa for 28 days. According to the results of testing cylinders made of vertical core, the minimum strength of cement-slag material was 7.3 MPa, the maximum - 11.2 MPa. The obtained results of the compressive strength of soil-cement material exceed the design strength equal to 2.5 MPa. As a result of the test work on the construction site of the VRU-1400, the correctness of the technical solution for the selection of Jet Grouting technology for reinforcement the foundation base in difficult engineering and geological conditions, namely blast furnace slags, was confirmed.