Study on Light Dynamic Penetration to Test Coarse Sand Relative Density in Bridge Culvert Back Sand Filling

Abstract

With the rapid development of highway construction in China, vehicle bouncing at bridge approach has become a very important influencing factor and has been paid much attention in domestic and overseas transportation study. Strict quality control in bridge-culvert back sand filling and construction process is of vital importance to prevent the differential settlement of bridge approach. However, the objective and effective test of sand relative density in bridge-culvert backfilling has been a hot yet difficult problem. In this study, based on model and on-site test under a scientific research program of the Guangdong Transportation Group － Sand Relative Density Test on Bridge-Culvert Backfilling (2008-13), the mechanism and the feasibility of light penetration test have been systematically studied. Through model and field test, the feasibility of light penetration to test relative density of coarse sand in bridge-culvert back-wall filling is testified. And through static penetration test contrast, the reliability of this test is further confirmed. Based on the above, the empirical relationship between the light penetration blow-counts N10 and the relative density Dr is established after simple calculation. Thus the light penetration method is proposed to test the relative density of medium and coarse sand in bridge-culvert back-wall filling. This study lays a foundation for the spread-use of the light dynamic penetration to count the technical index—the relative density of sand in bridge-culvert back-wall filling.