Research On High Performance Polyurethane Used For Sandy Soil Solidification And Its Application

For the past few years, with the accelerated construction of the project, problems of slope instability, soil erosion, desertification, dust are becoming more and more prominent, resulting in more and more losses. Soil erosion and land desertification have become the biggest threat to the ecological security in China. At present, it is an important way to solve this problem that we consolidate the loose sand particles in the same place, so as to prevent particles from further migration under the action of external forces.The core problem of consolidation of sand is to select a consolidated material with excellent comprehensive performance. Commonly used sand consolidation materials are divided into inorganic materials and organic polymer materials. Due to poor permeability, inorganic consolidation materials such as lime, cement, fly ash, slag are often need to mix with consolidation materials and sand. At the same time, the consolidation layer is easy to form shrinkage crack and the consolidation of thick layer is not conducive to the ecological slope protection. Organic polymer solidified material such as polypropylene acid, poly vinyl acetate resin, polyurethane arouse wide attention because with the advantages of low mix, easy to transportation and construction and easy to form soft consolidation layer in slope protection, prevention and control of soil erosion. But at present, organic polymer consolidation materials have some shortages such as poor permeability, low strength, poor water stability, lack of frost resistance and so on which seriously restrict the development of sand control field. As a kind of new organic polymer material, polyurethane has been widely used in many fields of national economy because of its excellent performance.In view of the existing sand consolidation material defects, this thesis prepared a kind of polyurethane sand consolidation material with good water stability, frost resistance and resistance to wind erosion, soil and water conservation and certain osmotic properties through a series of laboratory experiments. And all aspects of the performance parameters of the material was obtained through consolidation strength test, water resistance test, frost resistance test, permeability test, water retention test, resistance to wind erosion test.Through the methods of scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FT-IR) and X-ray diffraction(XRD), the consolidation mechanism of polyurethane solidified material was discussed, so as to provide the theoretical basis for improved materials and the further application.At last, the polyurethane sand consolidation materials was applied in Xinjiang Altay road cutting sand soil slope protection, achieving good curing effect. At the same time, in view of the problems occurred in the application, improved the materials and construction technology.The main research contents and results are as follows:(1)The raw materials and its mixture ratio of polyurethane solidified material were determined from the aspect of type of raw materials, ratio of raw materials, preparation conditions and other aspects. The organic solvents that can greatly reduce the viscosity of the polyurethane and the catalyst composition for accelerating the reaction rate were selected through a series of experiments. Thus a polyurethane sand consolidation material with excellent comprehensive properties was prepared.(2)Through the analysis of SEM, FT-IR and XRD in sand consolidation and combined with the macroscopic mechanical properties of the consolidated body, preliminary discuss the consolidation mechanism of polyurethane polymer material. The result also provided theoretical basis for further research and application of the new materials. The results showed that there was no chemical reaction between the polyurethane material and the sand body. And the interaction of the two elements was the intermolecular forces and hydrogen bonding interactions. The structure and pore characteristics of sand particles were not changed by the introduction of polyurethane materials and polymer in granular surface formed a film which was thin and tough and the film bridging stick to each other.(3)The standard sand was used as the reinforcement sand material, and comprehensive determination of material properties parameters were carried out through the compressive strength test, anti-erosion test, freeze-thaw cycle test, permeability test, water retention test, wind erosion test, etc. The results show that the strength of the solidified body was influenced by the concentration of the polyurethane. The strength is higher than the common polymer sand consolidation material. The anti-erosion performance of the consolidation body is influenced by the concentration of the polyurethane material and the slope angle. The consolidated body had good frost resistance, and the strength loss rate was less than 25 after 20 times of freezing and thawing cycles, the mass loss rate is less than 1.5%. After the consolidation, the permeability of sand and soil could be reduced to 15%. After 7 days, the water content of the consolidated sand body was 2 times of that of the unconsolidated sand and soil, and the excellent water retention property could provide the conditions for plant growth.(4)The new material was used in sand soil of Jimunai in Xinjiang and the results showed that the materials had good suitability in silty sand and fine sand. During the experiment, aiming at the characteristics of loose and no cement, put forward local strengthening, fixed-point pile construction technology and get an obvious results.The prepared polyurethane sand curing material has advantages of low viscosity, high strength, good water stability, weatherability. It provides a new idea for slope lost stability, soil erosion, desertification, dust and other issues of governance.