Study On Stability Analysis Method Of Geogrid-reinforced Gravel Soil Slope

The existing research shows that the geogrid-reinforced embankment has good performance against earthquakes.When gravel soil is used to construct the embankment,a significant reinforcement benefit will take place.Therefore,the geogrid-reinforced embankment of highway is suitable to be applied in Xinjiang,because earthquakes occur frequently and gravel soil exist widely in the area.For the above purpose,it is necessary to study the stability of the reinforced gravel soil slope to determine a more appropriate design method.At present,the limit equilibrium method is still a practical method to analyze the stability of reinforced soil slope.But in the future,the finite element strength reduction method is expected to be a more reasonable method.Therefore,these two methods will be discussed respectively in this paper.Firstly,the failure criterion of the reinforced soil slope for strength reduction method is studied.Secondly,according to the limit equilibrium method,a simplified method for calculating the safety factor of a geogrid-reinforced gravel soil slope,and the design procedure based on this simplified method are proposed.Finally,the earth pressure and the strain of the geogrid were observed for a long time in a highway embankment constructed with gravel soil and uniaxial geogrid inclusions.Based on the observed data,the applicability of the geogrid-reinforced gravel soil slope was evaluated.The following main conclusions are obtained.?1?It is appropriate to use both the non-convergence of solution and the displacement mutation of the appointed point on the slope as the failure criterion of a reinforced soil slope.Both criteria can obtain the same value of stability safety factor,but the latter is more practical.?2?Fsg,the safety factor of a reinforced gravel soil slope,has a good correlation with Fsj,the safety factor of the equivalent homogeneous soil slope determined by the quasi-cohesion principle.When the reinforcement spacing is from 0.3 m to 0.8 m,and the tensile capacity of the reinforcement layers is arranged approximately according to the recommendations of the specifications,and Fsg=1²,the Fsg-Fsj relationship can be expressed by quadratic polynomial.In addition,the F_sg-F_sj relationship is only related to the average slope rate of the slope and the soil's internal friction angle,and it is not related to the gravity of soil,the layout of the reinforcement layers,and the tensile capacity distribution of the reinforcement layers.Based on this,a simplified calculation method for calculating F_sgg with F_sj is proposed.?3?When Fsg is selected in[1.25,1.45]and nearby areas according to the requirements of current highway specifications,the absolute error of the simplified calculation formula for calculating F_sg by F_sj proposed in this paper is between[-0.016,0.012],which meets the requirements of engineering design.?4?A practical design procedure is proposed for a geogrid-reinforced gravel soil embankment based on the simplified calculation method noted above.?5?The strain level of geogrid measured in the geogrid-reinforced gravel soil embankment is generally litter than 1%,most of which does not exceed 0.5%.This indicates that the tensile load of geogrid inclusions is generally 15%of their tensile strength.?6?The measured horizontal earth pressure is very small behind the slope protection structure of the geogrid-reinforced embankment,and most of them are close to 0.