Study On The Centrifugal Model Test Of Support Scheme For A High Fill Slope In Nujiang Airport

With the large-scale construction of transportation infrastructure in the western development of C hina,the construction of airports in the southwest region has entered a rapid development stage.As most of the southwestern regions are mountainous areas,airport construction generally features high fill,high seismic intensity,and complex geological conditions.Nujiang Airport is located in Yunnan,where regional tectonic activity is strong and the geological conditions are complex.Due to the restriction and impact of site topography and geological conditions,the airport construction is faced with special problems.The terrain at the northern end of the airport is relatively flat,and the slope stability of most of it can be ensured through natura l grading.However,the terrain at the south end of the site is steep,with the gradients generally being 35° to 50° and some being 60° to 70°.Natural slpoe cannot be used in most cases for slope protection.Gravity retaining wall+ natural slope.Concrete Gravity Retaining Wall are adopted as major supporting plans for fill slope.These mean that it is quite difficult to control the stability and deformation of typical ultra-high and super-steep fill slopes at the southern end.Therefore,study on the stab ility and deformation behavior has significance in guiding the project construction.This experiment was done with the ultra-high and super-steep fill slope at the south end of the airport as a model.Reinforced slope(grading at a slope ratio of 1:0.3,and a maximum vertical fill height of 100m)and counterweight retaining wall(retaining wall height up to 78m)were adopted to study the stability and deformation characteristics of the slope,respectively.Through analysis and discussion on the stability,deformation characteristics and earth pressure distribution of high-filled slopes under two different reinforcement schemes,the following conclusions were drawn:1.Model test results show: There is no overall instability damage to the reinforced slope model,but local damage;the slope of the counterweight retaining wall has no overturning,collapse failure and foundation instability failure;the evaluation on overall stability of fill slopes,qualitative analysis based on combined model test results and quantitative analysis of theoretical calculations showed that both schemes are in an overall stable state;2.The settlement deformation and crack distribution characteristics of the model indicate : both the reinforced soil slope and the counterweight retaining wall have settlements and cracks developed.Within one year after construction,the settlements of the reinforced slope and counterweight retaining wall slope are basically stable,and the settlement within one year after the work is 2.0 mm and 2.06 mm,which is equivalent to the settlement of the prototype slope of 220 mm.Meet the relevant regulatory requirements.The reinforced earth slope and counterweight retaining wall surface developed two through cracks and some criss-cross cracks.The widths were5～6mm and 3～4mm respectively,and the depths were 20～30mm and 25～30mm,respectively.Cracks are mainly caused by uneven settlement of the building.3.The characteristics of earth pressure distribution of reinforced earth slope scheme and that of counterweight retaining wall scheme are similar: the distribution of earth pressure behind one wall near the bedrock interface is in the form of a triangular;the earth pressure increases as the increase of buried depth,and its distribution pattern is simila r to that of Rankine’s active earth pressure.The soil pressure on the side of free surface of slope is obviously nonlinear,which is similar to a cast-line.4.Comparison and selection of supporting schemes: Comparison and selection of supporting schemes are done by combining the reliability of test results,feasibility and economy of supporting programs.Both reinforcement programs have their own advantages and disadvantages,the proposed high-filled slope for the N ujiang Airport will adopt a reinforced soil slope scheme,and a further study will be conducted on the local damage of the reinforced soil scheme.