Quantitative Analysis Of The Degree Of Void Beneath Airport Cement Concrete Pavement By Deflection Test

Voids beneath slab is one of the most important reasons of causing airport concrete pavement defect, and how to quantitative evaluation the extent of void beneath slab is a major problem existing in airport pavement management. The following works is done to solve these problems:First, the quantitative assessment is proposed. Use the finite element method to establish the void dimension model of theory analysis based on deflection test, and analysis of the change law of void area following deflection?load transfer ability?relative stiffness to get the quantitative analysis model of void dimension beneath cement concrete pavement. On that basis, proposed the quantitative assessment and process of sheet edge based on the existing airport pavement deflection test. The research results will be important references to airports pavement management and evaluation.Second, evaluate the extent of foundation void. The change law of stresses in the different structure parameter and void radius is studied by finite element method. The analysis found that: Under the condition of void beneath slab corner, when the void radius is less than 0.2 m, stress decreases with increasing the void radius, when the void radius is greater than 0.2 m, stress increases with increasing the void radius, when the void radius is greater than critical radius, the maximum stress transfer to the voids escapes in the edge of the plate. So, the void radius 0.2 m and critical radius can be as boundaries. The radius of pavement less than 0.2 m is as mild escapes; the radius more than 0.2 m and less than critical radius is as medium escapes; the radius more than critical radius is as serious escapes. Analysis results can be used in the airport cement concrete road evaluation and protection of broken slab.Third, evaluate the extent of slab edge void. Under the load on slab edge, the largest stress occurs at the bottom round printing, and the stress is equal, when there is not any void; When the bottom void radius > 0.2 m, the largest stress is focus on one of round printings, and its value increases with the increase of the void radius. So, the void radius 0.2m is the boundary point for the degree of slab edge void, and use the limit radius of slab corner void.The static degree of dividing the level of slab edge void: The radius of pavement less than 0.2 m is as mild escapes; the radius more than 0.2 m and less than critical radius is as medium escapes; the radius more than critical radius is as serious escapes.