Study Of Geotexil-soil Interface Properties And Stability Of Reinforced Embankment On Soft Foundation

The contradiction between soft foundation treatment and time limit is the mostdifficult problem when building embankment on soft clay foundation. Practice hasproved that geotextile reinforced cushion unites Vertical Drains works for the problem.Geotexil-soil interface properties research is the basic work before thedesign,deformation and stability analysis of reinforced structures in whichgeotexil-soil interface strength parameters are the key technical indices. Reasonablecomputing method and engineering practice depend on the knowledge ofreinforcement mechanism which need more research. Traditional limit equilibriummethod is conservative and unreasonable, the improved model consideringreinforcement mechanism needs to be set up. Large quantities of indoor tests andnumerical simulations were carried out to study the strength properties ofsand,geotexil-soil interface properties and the reinforcement mechanism,an improvedmodel was set up.The main research contents and conclusions is as follows.(1)The study of strength properties of geotexil-soil interface. Direct shear testwas carried out to study effects of density, shear rate on the strength properties of sand.Pull out test focus on the the law and mechanism of drawing rate’s influence ongeotexil-soil interface properties,a comparison about reinforcement effect was madebetween different fillers and different geosynthetics, the selection of internal frictionparameters was discussed. The results show that: the higher the density, the moreremarkable the strain softening phenomenon,while the shear rate has no influence.The stress-strain relationship of geotexil-soil interface presents hardening.Geotexil-soil interface properties is both influenced by normal stress level anddrawing rate, especially the effect of drawing rate, in connection with testmethod,filling properties and geosynthetic type.What the test rate influences areinterlocking occlusion and cohesive action, rubbing action is not on the list. Comparedwith the direct test results of sand,friction angle of geotexil-soil interface is less than thesand’s,however, shear strength of the geotexil-soil interface can be higher than thesoil’s in a certain normal stress when there is a considerable cohesive force. Therefore the choice of friction parameter for design should according to the size of cohesiveforce.(2)Deformation and stability analysis based on geotexil-soil interface propertiesof reinforced embankment on soft foundation.A finite element analysis of elastoplasticconsolidation was adopted to study the development law of deformation andreinforced cushion’s reinforcement mechanism of a typical embankment constructedon soft foundation from perspectives of stress-strain field, reinforcement tension andstability etc. Large deformation effects was compared, the influence of geotexil-soilinterface strength，filling velocity and indirect effect mechanism was studied. Theresults show that: Reinforcement can effectively constrain shear deformation offoundation, constrain the lateral deformation of the embankment and improve therebound ability of horizontal displacement in consolidation stage,can effectivelyreduce the central settlement in filling stage(final settlement is not on the list) andexpand the maximum settlement to the center. Shallow layer soft ground’s excess porepressure of reinforced embankment is obviously higer due to the interfacial shearstress,but tending to unanimity with consolidation. The safety factor of reinforcedembankment is obviously promoted,failure mode is changed which in connection withtensile strength,geotexil-soil interface strength and geological conditions etc. Thecentral settlement and slope toe’s horizontal displacement is obviously reduced whenlarge deformation effects was considered. Geotexil-soil interface strength makes adifference to interfacial shear stress level and stability in the large,but has no effect onthe hole deformation field and reinforcement tension.The construction ofnon-reinforced embankment is distinctly influenced by filling velocity whilereinforced embankment can be constructed quickly. The reinforcement tension andinterfacial shear stress level greatly reduced and the stability of the embankmentimproved when the indirect effect mechanism was considered.(3) Stability analysis based on the limit equilibrium condition of reinforcedcushion embankment on soft foundation. Based on traditional method,an improvedstability calculation model of reinforced embankment was set up in combination withthe indirect effect mechanism, different methods was adopted to analyse the stability of the embankment. The results show that: Based on the indirect effect mechanism，strengthreduction method and simplified Bishop method can reflect the effect of reinforcement. Thestability analysis results of strength reduction method is in accord with simplifiedBishop method, while Sweden slice method is different from the rest whose safetyfactor is on the low side and sliding arc is unlikelihood. Strength reduction methodand simplified Bishop method is more suitable for analysing the reinforcementmechanism on the stability.