This study evaluates the use of 3D laser scanning technology to measure pavement roughness. Three 100 m test sections, ranging from smooth to very rough (with apparent cracks, areas of distress, and manholes) were selected to investigate the capability of the 3D laser scanning technology. Rod and level surveys were conducted to establish the reference profile for each test section. In addition, Multiple Laser Profiler (MLP) was employed to measure the multiple paths of each test section. Results from multiple paths of 3D laser scanning were compared with those from MLP and rod and level surveys. The 100 m reference profiles indicate similar results between the 3D laser scanning and rod and level survey. With 95% confidence, the statistical paired-samples T-test indicates that there is no significant variation between the results from rod and level surveys and 3D laser scanning. The data include IRI from 2.83 to 13.15 m/km such that they represent a wide spectrum of pavement conditions. The coefficient of correlation (R2) between the MLP and 3D laser scanning from 20 longitudinal profiles is 0.99. The 3D laser scanning is a static method and thus the data do not have to be filtered and therefore there is no associated cut-off wavelength problem. Based on the results gathered, the 3D laser scanner is able to collect reliable profile data and has high potential to be used as a QC/QA tool for construction acceptance. Through 3D laser scanning technology, pavement engineers are able to visualize the pavement roughness covering the entire pavement width in unprecedented detail that consists of extremely rich and accurate point-cloud data.
In this research, laboratory pullout tests were conducted on grouted soil nails to study the effect of wetting on the interface shear resistance between nail and soil during pullout. Deformed bars with equal size to the true soil nails were used as model nails. The soil used was silty fine sand collected at the site and prepared to a very dense condition. Rainfall infiltration was simulated using duplicated soil nails inundated by water for different periods. Test results indicated that the peak pullout resistance strongly decreases upon wetting, with a reduction of about 60% after soaking for 28 days. However, the experiments showed that there is a threshold water content (or soaking time) beyond which the effect of infiltration on the pullout resistance is reduced. The laboratory protocols developed in this study offered an easy scheme for the prediction of the pullout capacity of a grouted soil nail upon wetting.
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