Study On Rapid Restoration Of Mountain Roadbed Slope Via Air-foam Treated Lightweight Soil And Micro-piles

Due to the complex geological structure,rock strata fracture,joint crack development and high weathering degree of mountain roads,landslides and collapses are extremely likely to occur under the action of heavy rainfall,vehicle load,blasting,earthquake and other inducing factors.With the rapid development of road and the increase of road mileage,sudden road break caused by the destruction of subgrade slope in mountainous areas gradually increases,which has a great impact on people’s normal life and social and economic activities.Due to the special environment of mountain roads,the emergency repair work faces are few and space is limited.The traditional emergency repair method is inefficient and takes a long time,so it is difficult to realize the rapid repair of road subgrade slope in mountain areas.Based on the scientific research project named "chongqing local trunk highways breaking off emergency repair technology research" of the Traffic Committee of Chongqing city,the author use the mothods of summarizing the relevant research results,field investigation,indoor test,theoretical analysis and numerical simulation methods to study Air-foam Treated Lightweight Soil(ATLS)with quick fix mountains miniature pile composite system.Through this study,the following results are obtained:(1)Based on research of the characteristics of the subgrade slope of the mountainous road,the paper takes use of the characteristics such as high strength and light weight of Air-foam Treated Lightweight Soil(ATLS)and the characteristics such as perfect mechanical performance and rapid construction of micro-pile to design a composite support system.(2)The results of triaxial compression test of ATLS show that the stress-strain relationship curve presents two different characteristics of strain softening and strain hardening in the plastic deformation stage.The strain softening curve is well fitted with the Prevost softening model,while the strain hardening curve is well fitted with the Duncan-Chang hyperbolic model.(3)Geological factors such as topography,topography,stratigraphic lithology and geological structure are important causes of geological disasters of roadbed slope in mountainous areas.Factors such as rainfall intensity,duration of rainfall and underground water level are important inducing factors for geological disasters of subgrade slope in mountainous areas.(4)Using the relationship between displacement(y)of pile and soil resistance fore(p),p-y curve of the micropile in different depth of ATLS can be derived.Based on miniature pile load segment and the anchoring in the sliding surface to satisfy deformation coordination,can create tiny pile elastic-plastic mechanics analysis model and general control equation and difference method can be used to solve the horizontal load of the micro-piles under the action of ATLS.(5)The mechanical characteristics and deformation characteristics of the composite structure system were studied by numerical analysis method,and the optimal design was carried out.The numerical calculation results show that the micro-pile mainly carries the shear force and the moment,and the maximum value of the shear force and the bending moment are located at the slip surface of the subgrade slope.In the case of the same subgrade slope backfill height,the micro-pile shear and bending moment increases with the angle of the sliding surface.In the case of the horizontal angle of the same slip surface,the pile and moment of the micro-pile increase with the height of the backfill.The maximum displacement of the vertical displacement occurs at the top of the subgrade,with the angle between slope increases the trend is reduced.With the increase of vehicle load,the vertical displacement increases and the vehicle load has a great influence on the vertical displacement of the slope.It is possible to effectively reduce the vertical deformation of the embankment slope,optimize the force characteristics of the composite support system and improve the stability safety factor,and also improve the stability of the composite support system by incorporation of the geogrid,optimizing the construction steps and improving the strength of ATLS.(6)Engineering application and design process is studied for ATLS and micro-pile composite supporting system including strength,resistance to sliding and bearing capacity of ATLS and type selection,pile spacing,pile length,row spacing of micro-pile.