Study On Deformation Stability Characteristics And Treatment Technology Of Expansive Soil Filled Subgrade

Expansive soil is widely distributed in various regions of China.With the rapid development of traffic construction,the problem of expansive soil in highway design and construction is becoming more and more common.As expansive soil has the deformation characteristics of wet expansion and dry shrinkage,it is easy to cause uneven deformation of Subgrade under the action of dry wet cycle,resulting in a variety of subgrade diseases,seriously affecting the traffic capacity and driving safety of expressway.Therefore,based on the project of "Application Research on comprehensive treatment technology of Expansive Soil Subgrade of xinliunan expressway",this paper deeply analyzes the deformation and cracking mechanism of expansive soil subgrade by means of model test,field monitoring,theoretical calculation and numerical simulation,and systematically studies the utilization of expansive soil subgrade filler and subgrade deformation control technology and its engineering application.The main conclusions are as follows:(1)The physical and mechanical properties of representative expansive soil samples along xinliunan expressway are studied.The relationship between shear strength index and saturation of expansive soil,and the relationship between compaction work and expansion,CBR index are explored.Based on the standard moisture content classification method,the CBR expansion is proposed as an evaluation method to judge the strength of filling expansibility.(2)Through the compression test of subgrade model,the deformation development law of Subgrade under different constraints and water transfer conditions is revealed.Poisson ratio is used to describe the time-varying process of lateral plastic deformation of expansive soil,and the deformation development of expansive soil under different working conditions is evaluated,which provides parameters for theoretical calculation and construction practice.(3)By means of automatic monitoring technology,this paper studies the post construction settlement,horizontal displacement and soil temperature and humidity change law of baobian embankment,verifies the treatment effect of composite support structure and anti-seepage and moisture retaining measures,and optimizes the reinforcement design parameters to guide the design and construction of expansive soil subgrade.(4)According to the theory of three-dimensional deformation and settlement,the calculation expression of three-dimensional additional stress increment is derived,and the deformation of expansive soil subgrade is predicted and analyzed.The numerical simulation model of original subgrade and reinforced subgrade structure is established by using ABAQUS finite element analysis method,and the stress and deformation characteristics of Expansive Soil Subgrade under adverse engineering conditions are studied,and the geogrid,footwall and subgrade are analyzed The supporting mechanism of the composite structure formed by the interaction is analyzed and compared with the theoretical results and the measured results.(5)Combined with the test results,this paper puts forward the test evaluation method for the use of expansive soil filler,and expounds the construction points of quality control for the filling of expansive soil subgrade from the aspects of base treatment,foot wall support,edge binding interface reinforcement and compaction,the use of reinforcement materials and geotextile embedding,so as to scientifically guide the design and construction of Expressway Subgrade in expansive soil area.