Study On Mechanical Properties Of Low-exothermic Polyurethane Grouting Material

With the rapid development of China's economy,China has constructed a large number of roads,railways and other basic projects in permafrost areas and seasonally frozen areas,but road diseases in frozen areas are frequent,and some road sections are seriously damaged.The problem of repair and maintenance of roads and railway projects in frozen areas has always been a major worldwide problem.Grouting repair technology is one of the main road and railway engineering disease repair and maintenance technologies,especially the polyurethane polymer grouting technology with high reaction speed,high expansion,high impermeability and high toughness is the current research Popular topics.The polyurethane polymer grouting technology has been maturely applied to the repair and maintenance of roads,railways and basic engineering diseases in ordinary areas,but due to the large amount of heat released during the reaction,the thermodynamic balance is destroyed and the surrounding soil is affected.It is not suitable for the repair of diseases in frozen areas.Therefore,the study of using low exothermic polymer grouting material is the inherent demand for the repair of complex diseases in highway and railway engineering in permafrost and seasonally frozen areas.The main research contents and results are as follows:(1)Three main chemical reactions and three reaction stages of low exothermic polyurethane polymer grouting materials were analyzed.In this paper,the injection molding method is used to obtain the low exothermic polyurethane high polymer injection materials with different density.The water absorption rate,volume change rate and free expansion rate are tested and studied.The influence law of temperature and density on the basic physical properties of the low exothermic polyurethane high polymer injection materials is summarized and the influence mechanism is analyzed.(2)The expansion characteristics of low exothermic polyurethane polymer grouting materials were studied.In different temperature(-30??30?)environment,the swelling pressure curves of different density(0.2g/cm~3?0.5g/cm~3)of low exothermic polyurethane polymer grouting material with time change were measured,the swelling speed of different density under different temperature was calculated,the relationship between the temperature,density,swelling pressure and swelling speed of the material was revealed,the maximum swelling pressure of the material was determined,and the grouting pressure of the material was the same as that of ordinary polyurethane polymer The test results of the maximum expansion pressure of the material are compared and analyzed.(3)The tensile and compressive properties of low exothermic polyurethane polymer grouting materials were studied.In different temperature(-30??30?)environment,the tensile strength and compressive strength of different density(0.2g/cm~3?0.5g/cm~3)materials are measured,and the stress-strain curve is drawn.Poisson's ratio of materials with different densities at room temperature was measured.The failure modes of the grouting materials with different density and temperature were determined.The variation of compressive strength and tensile strength of polymer grouting materials with density at different temperatures was summarized.The mechanism analysis of different deformation characteristics in the process of tension and compression is analyzed.Compared with the test results of tensile strength and compressive strength of common polyurethane high polymer grouting materials,the results are analyzed.(4)based on the constitutive model of Gibson-Ashby foam,the constitutive model of low heat release polyurethane polymer grouting material is derived from the angle of micro cell body force.The relevant parameters in the model are determined.The relationship between material stress and strain is revealed.(5)Based on the ABAQUS finite element software,combined with the relevant meteorological and geological data of permafrost area.The temperature field model of three-dimensional channel in permafrost area is established under the action of multi field coupling.On this basis,the dynamic response analysis of semi-rigid base pavement before and after void repair in different environments in permafrost area is carried out.The vertical displacement and Mises stress before and after void repair were compared and analyzed.The feasibility of application of low exothermic polyurethane high polymer grouting material in the non-destructive repair of roads in permafrost area is determined.The research on the mechanical properties of low exothermic high polymer grouting materials and the mechanical properties of low exothermic high polymer grouting materials with different densities under different temperatures can provide theoretical basis for the repair of road diseases in permafrost and seasonal frozen areas,which has important theoretical significance and engineering application value.