Study On Methods For Evaluating The Slope Stability Of Geogrid-reinforced Granular Embankment

Theoretical research and engineering practice show that geogrid reinforced coarse grained soil has the advantages of high strength,high rigidity and good earthquake resistance.Coarse grained soil distributes widely in Xinjiang,so many highway embankment is filled with coarse grained soil.Meanwhile,Xinjiang is in earthquake-prone areas.Therefore,it is very significant to promote geogrid reinforcement technology.For this purpose,it is necessary to study the stability analysis methods of geogrid reinforced coarse-grained soil subgrade slope in order to determine the appropriate design calculation method.The main work of this paper is as follows:?1?Discussing the limit equilibrium method that used widely at present.Comparing the similarities and differences of the methods for evaluating the stability of reinforced soil slopes at home and abroad.?2?Studying the application of strength reduction method,double strength reduction method and dynamic strength reduction method in reinforced coarse grained soil slope.?3?Studying the theory of Reinforcement-Effected Strip?RES?,including physical experiment that observes the thickness of RES by pull-out tests and numerical simulation that analyses the formation mechanism of Reinforcement-effected Strip by using the PFC.Based on the test and numerical simulation results,a method considering RES,RESM for short here,is suggested to analyze the stability of a reinforced soil slope.?4?Finally,the sensitivity analysis of the main influence on the stability of the reinforced soil slope is carried out,which provides guidance for the rational design of a geogrid-reinforced granular slope.The main conclusions are as follows:?1?The limit equilibrium method is the most suitable method to analyze the stability of a geogrid-reinforced granular slope while new method is not mature.However,because it can not reflect the internal mechanism of the interaction between soil and reinforcement,the results are often conservative.?2?The safety factor calculated by the strength reduction method is close to the limit equilibrium method,and the most dangerous slip surface determined by the two methods is basically the same.?3?The experiment results show that RES does exist.The depth of RES and the average diameter of soil particles(d₅₀)is approximately piecewise linear.?4?RESM can not only consider the mechanism of reinforcement,but also simplify the traditional limit equilibrium method.Using this method to calculate the safety factor of a geogrid-reinforced granular slope is about 10%larger than that given by the limit equilibrium method,which may be more in line with the actual situation.However,the method to determine the thickness of RES in RESM depends on further research.?5?The reinforcement density has a direct correlation with the safety factor of the reinforced slope.Reinforcement density can comprehensively reflect how the reinforcement spacing and the tensile strength influence the safety factor of the reinforced slope.?6?Through sensitivity analysis,the order of sensitivity of major factors on the stability of a reinforced slope is:?,H,m,t,c.