| SMW(Soil Mixing Wall)method is to use a special multi-shaft mixer to cut the soil in situ,and then inject cement slurry and other curing agents to mix with the soil to form an underground continuous pile wall with certain strength and stiffness.Nanchang area is in Ganfu alluvial plain,its surface layer of powdered clay is loose and unstable in structure,the traditional curing agent is used to solidify the powdered clay,forming a low strength of the hydraulic soil pile wall,but with the development of support technology,it is necessary to improve the strength of the hydraulic soil pile wall on the basis of meeting the low permeability,so that it can work together with steel and other metal materials to withstand lateral pressure.Therefore,it is necessary to explore the suitable curing agent to enhance the compressive strength of powdered clay and the change of mechanical properties after reinforcement.In this paper,indoor tests were conducted to determine the optimal combination of improved curing agents for the soil characteristics of powdered clay in Nanchang area,and the mechanical properties were investigated by central pull-out test and bending-shear test of reinforced-hydraulic clay combination beam to provide theoretical basis and test data for the wide application of reinforced hydraulic clay in Nanchang area.The main work and results of this study are as follows.(1)The optimal ratio of DH2 for the curing and improvement of powdered clay was determined by single-mixing test and orthogonal test,which was 24% of cement,8% of water glass,2% of quicklime,2% of junction cold glue and 5% of PAM,and was recommended to be used when the water-cement ratio was 1.2 and the moisture content of powdered clay was 25%.After the improvement of DH2 curing agent,the powdered clay can reach 8.3 MPa at the standard age.from the ANOVA,it can be seen that the water glass dosing has a significant effect on the unconfined compressive strength of the cement soil.From the ANOVA,it can be seen that the water glass admixture has the greatest effect on the compressive strength of the cement soil,followed by the PAM admixture and the junction cold glue admixture,and the quicklime admixture has the least effect.(2)Through the central pull-out test of reinforced-cement soil,it was found that only one damage mode of pull-out damage occurred in the reinforced-cement soil structure,and the influence of anchorage length,protective layer thickness of cement soil and diameter of reinforcement on the bonding performance of reinforced-cement soil interface was analyzed by drawing displacement load curve and bond strength curve based on the test data.The optimum protective layer thickness of 20mm~30mm and the diameter of reinforcement 10 mm were obtained.(3)Through indoor bending-shear tests on reinforced-cement soil combination beams with different heights and loading methods,the force process,damage mode,combination stiffness and reinforced-cement soil co-interaction of the combination beams are analyzed,and it is known that the force process of the combination beams can be divided into two stages: quasilinear co-interaction stage and plastic co-interaction stage.The reinforced cement beam damage has the same characteristics: bond failure and shear damage.The theoretical analysis of the reinforced-hydraulic soil co-interaction is carried out to obtain its calculation method and the law of the co-interaction stage.Finally,the combined stiffness of the test beam is calculated by using the material mechanics calculation formula,and it is found that the combined stiffness shows a decreasing trend with the increase of load. |
