Research On Failure Mechanism And Design Countermeasure Of The Subgrade Of Fold Axis In Mountainous Area

Fold structure is formed through long-term evolution and deformation of layered strata under the action of strong tectonic stress or gravity.Among them,the axis of the fold is the area with the largest deformation in the process of fold formation,and its resistance to mechanical deformation is lower than other parts of the fold,and it is also the part where the stress is concentrated.This thesis mainly focuses on the syncline structure of fold structure,syncline is a kind of special geological structure with old lower strata and new upper strata and "concave" shape.In order to meet the needs of engineering construction,a highway project requires the oblique axis to be built.Based on this engineering background,this thesis discusses and studies the deformation mechanism of roadbed engineering.In this thesis,the deformation and failure of the subgrade body and cut slope on both sides of the subgrade in folded axis are simulated to analyze the deformation and failure of the subgrade body and cut slope under the action of various influencing factors and the change phenomenon caused by the factors are analyzed in depth.Finally,relevant treatment measures are implemented for the subgrade body and cut slope and their treatment effects are evaluated.The main research contents and conclusions of this thesis are as follows:(1)By calculating the model of the folded axial subgrade and considering the different factors that may lead to uplift and deformation of the subgrade body,the steepness of the cutting slope,the excavation depth of the cutting,the width of the road,the extension depth of the axial subgrade influence zone and the extension width of the axial subgrade influence zone are taken as the main influencing factors for in-depth study.(2)Based on the analysis of existing research data and results,a reasonable control standard is set for the uplift and deformation of subgrade body by referring to the provisions of highway arch transverse slope and ultra-high transverse slope,comprehensively considering the driving safety and comfort of the road.The allowable uplift and deformation of subgrade body is set as no more than 0.05 m.(3)The influence degree of each factor on the uplift deformation of the subgrade body is respectively considered by the control variable method,and the change relationship between the influencing factor and the uplift deformation generated on the surface of the subgrade body is obtained.Finally,the uplift deformation is roughly proportional to the height of the cutting slope,the extension depth of the influence area of the axial subgrade,and the width of the road.Is roughly inversely proportional to the extension width of the influence zone of the axial subgrade.(4)According to the relationship between the vertical displacement of each point on the surface of the subgrade body under the influence of various factors,the subgrade position in the range of 0～5m and 20～25m is set as the sensitive region of vertical displacement,and the range of 5～20m is set as the stable region of vertical displacement.(5)By setting cement fly ash crushed stone pile in the influence area of axial subgrade,the uplift deformation on the surface of subgrade body is controlled.By comparing the length,number and position of pile,it is finally concluded that the most reasonable treatment method is that setting pile in the sensitive area of vertical displacement can effectively control the uplift deformation on the surface of subgrade body.(6)The failure mode and characteristics of bedding rock slope are summarized,and the change rule of stability and failure mode and characteristics of bedding rock cut slope under the action of various factors(rock dip Angle,rock thickness,thickness of weak structural plane,slope grade,slope height)are studied,and multistage slowing slope and bolt support are adopted to strengthen and stabilize the slope.