Study On The Working Behavior And Stability Of Ultrahigh Geosynthetic-Reinforced Embankment

With the deepening of China’s Western Development Strategy, high-grade highways inlosses region have been developed rapidly. Restricted by the complicated geographic andgeomorphic conditions, the high fill embankment has become a main structural pattern, theheight of which even reaches50m. The deformation characteristics and global stability ofhigh fill embankments have been widely concerned in recent years. Triax geogrid, whichhas unique physical and mechanical properties, can reduce the deformation and improve thestability when it is used as reinforcement for embankments. The deformation characteristicsand overall stability of ultrahigh fill geogrid-reinforced embankment have beensystematically studied in this thesis by FLAC3D numerical analysis.Firstly, the construction procedure of ultrahigh fill geogrid-reinforced embankment iselaborately simulated. The variation data of the settlements and horizontal displacements ofembankment’s key points during construction is well recorded. At the same time, aparametric analysis of the influences of the fill’s and subsoil’s modulus on embankmentdeformation is performed. The results show that the settlements and horizontaldisplacements reduce while increasing the elastic modulus of the fill and subsoil, so doesthe axial force of geogrid. In addition, the reinforcement effect of the geogrid weakens.Secondly, the response of embankment under static and dynamic uniform loadsactiong on the embankment surface is studied. Based on fully nonlinear method, theimpacts of amplitude, frequency and running interval of taffic load on the embankmentresponse is analyzed. According to the results, the deformation of embankment surfaceunder static loads is more vivid. However, the settlements and horizontal displacements ofembankment surface under dynamic traffic loads grow with the cycle index, but theincrease percentage of deformation diminishes gradually to a stable value. The maximumsettlement of embankment surface increases with the increase of the amplitude of trafficload, frequency and the decrement of running interval.Thirdly, the effects of the geogrids on the stability of ultrahigh fill embankment arecontrasted. The performance of shear strength of soils and interface parameters betweenreinforcements and soils is simulated by shear strength reduction (SSR) method. The slopesafety factor and potential sliding surface is also caculated. The results of study cases show that when the fill’s shear strength is low, geogrid reinforcements can improve the safetyfactor by10%~20%. The interaction between geogrids and soils enhance the stability ofembankment. The potential sliding surface moves into deeper layer of embankment whengeogrid reinforcements are spread, and its curvature becomes smaller.Finally, the concepts about rainfall infiltration reduction factors and rainfall reductionpatterns are proposed. The reduction of soil shear strength in various degrees is taken tosimulate the rainfall infiltration of the ultrahigh fill geogrid-reinforced embankment. Thesafety factors under different infiltration reduction factors, infiltration depth and staticuniform loads are caculated. The results show that there exists a critical value forinfiltration reduction factor, below which it would have a remarkable influences on theslope safety factor and sliding surface. With the geogrid reinforcements spread in theembankment, the stability of slope under rainfall infiltration is improved.