Study On Instability Mechanism And Control Of Soft Soil Slope Embankment In Chongqing Area

There are a lot of soft soil slope embankments in the construction of mountainous highway in Chongqing.The poor engineering properties of soft soil foundation under the embankment affect the overall stability of highway.The commonly used treatment scheme of soft soil slope foundation is to use CFG pile,pipe pile,plain concrete pile and other measures to strengthen the foundation.These measures have different degrees of foundation treatment failure in the actual project,resulting in embankment collapse,instability and subsidence and other engineering disasters,which seriously affect the safety of highway construction and operation.Therefore,it is necessary to study the treatment of soft soil slope embankment in Chongqing.Based on the national key research and development project "Research on instability mechanism and new prevention and control methods of typical geological disasters in red bed area",this paper takes "a highway high fill treatment project in Chongqing" as an example,and carries out a series of theoretical and numerical studies on the basis of preliminary field investigation work:according to the preliminary investigation results,select typical sections,and use the limit equilibrium method This paper evaluates the stability of landslide,establishes a simulation model by using three-dimensional numerical software,simulates the deformation and instability of anti slide pile and CFG pile composite foundation in the process of subgrade filling,analyzes and summarizes the instability mechanism of soft slope embankment combined with the stress characteristics and failure mode of CFG pile,and puts forward two treatment schemes according to the instability mechanism of embankment,and uses the simulation model to simulate and analyze the two schemes Based on the mathematical fuzzy method,the optimal scheme is selected.In this paper,we have made the following progress(1)Through field investigation and geological investigation,the engineering geological conditions and soil physical and mechanical parameters of the section are obtained.The limit equilibrium method is used to calculate the stability of the instability area.The calculation results show that the safety factor of the instability area is 1.046 under natural conditions,which is in an unstable state;the safety factor is 0.966 under rainstorm conditions,which is in an unstable state.(2)Combined with the field survey data,a three-dimensional simulation model is established by using FLAC3 D software to simulate and analyze the deformation process of anti slide pile in deep silty clay layer under different filling heights.The results show that with the increasing of subgrade filling,the pile will overturn and the anti slide pile will lose stability.(3)The three-dimensional simulation model is used to simulate the filling deformation process of CFG pile composite foundation,and the displacement nephogram,shear stress diagram and safety factor of back pressure slope under different filling heights are analyzed.The results show that with the increase of filling height,the deformation of slope is increasing,the plastic zone is connected after filling,and the slope is unstable as a whole.Combined with the stress of pile in the foundation,the deformation of slope is increasing Based on the analysis of the failure characteristics and failure mode,the CFG pile gradually fails in the filling process.(4)According to the results of theoretical and numerical analysis,two treatment schemes are put forward.Scheme 1: anti slide pile retaining + reinforced soil;scheme 2:Gravel Pile Composite Foundation + soil back pressure + drainage facilities + anti slide pile retaining.Through three-dimensional simulation model,the treatment effect of the two schemes is simulated and analyzed.The results show that the maximum horizontal displacement and vertical settlement are controlled at 30.67 mm and 39.3mm respectively.After treatment,the maximum horizontal displacement and settlement were controlled at20.57 mm and 92.25 mm respectively.Referring to the relevant specifications and engineering experience,both schemes meet the governance requirements.(5)Combined with the results of numerical simulation,based on the fuzzy comprehensive evaluation method,the technical reliability,construction difficulty,construction safety,construction period,project cost and environmental impact of the two treatment schemes are comprehensively evaluated,and the second scheme is more feasible.The results of this paper will provide a new idea for the analysis of the instability mechanism of soft soil slope embankment in Chongqing,provide reference for engineering practice,and have important significance for ensuring the safety construction and operation of highway.