Deep Kumar Khatri

Laboratory Study on Geosynthetic Protection of Buried Steel-Reinforced HDPE Pipes from Static Loading

AbstractGeosynthetic layers above a pipe can potentially reduce the deflection and strain in the pipe attributable to static loads. This paper discusses the laboratory results of shallowly buried steel-reinforced high-density polyethylene (HDPE) pipes subjected to static loads with or without geogrid. In the testing, static loads were applied to a steel plate seated on the ground with a 0.61-m-diameter steel-reinforced HDPE pipe buried in a compacted-sand trench. Four static loading tests were run with two different base courses and geogrids inside and above the trench. The test section was instrumented to record pipe deflections, earth pressures, and strains in the pipe wall and geogrid. Installation deflections were monitored and compared with a theoretical model. The measured earth pressures were compared with those estimated by the current AASHTO live-load distribution method. Reduced deflections and strains of the pipe were recorded as a result of the geogrid reinforcement. The type of base course al...

Laboratory Evaluation of Deformations of Steel-Reinforced High-Density Polyethylene Pipes under Static Loads

A new product, steel-reinforced high-density polyethylene (SRHDPE) pipe, with high-strength steel reinforcing ribs wound helically and covered by corrosion-resistant high-density polyethylene (HDPE) resin inside and outside has obvious advantages. To investigate the behavior and performance of such a new pipe, three parallel plate tests were conducted in air. The deflection profiles of the pipes and the strains on both steel and polyethylene plastic were measured. No cracking was observed on the plastic during the experiment. The photogrammetry technology was effective in measuring the deflection profiles of the pipes during loading. The light detection and ranging (LiDAR) technology could obtain three-dimensional images of the pipes but was suitable for stationary targets. Strain gauge data indicated the occurrence of out of plane buckling of the steel ribs at failure and the strain incompatibility between the steel ribs and the plastic cover during loading.

Field Installation Effect on Steel-Reinforced High-Density Polyethylene Pipes

A full-scale field study was conducted in Kansas to investigate the installation effect on steel-reinforced high-density polyethylene (SRHDPE) pipes. Four 2.13 m-long SRHDPE pipes with a diameter of 0.61 m were connected and buried in a trench with dimensions of 1.52 m wide, 9.15 m long, and 1.40 m deep. Two types of backfill material were used in the trench, namely, Aggregate Base Class 3 (AB3) aggregate and crushed stone. Two pipes were buried in the AB3 aggregate section with an average degree of compaction of 90.4% whereas the other two pipes were installed in the crushed stone section with an average degree of compaction of 89.5%. The soil cover thickness in both the AB3 aggregate and the crushed stone sections was 0.65 m. A vibratory plate compactor was used to compact the backfill material inside the trench. Pipe deflections in the vertical, horizontal, and 45° directions from the pipe crown were monitored during backfilling. Earth pressures around the pipes were measured during the construction. Test results indicate that (1) the peaking deflection of the pipe in the AB3 aggregate section was 1.5 times that in the crushed stone section; however, the vertical diameter change of the pipe in the crushed stone section was 3.5 times that in the AB3 aggregate section after backfilling above the top of the pipe. The pipe diameter change in the crushed stone section in the 45° direction from the pipe crown was greater than that in the AB3 aggregate section. The deflections of the SRHDPE pipe in these two types of backfill material with a soil cover thickness of 0.65 m were much less than the 5% deflection limit suggested for steel and high-density polyethylene (HDPE) pipes by the AASHTO; and (2) the soil arching factors at the top of the pipe in both sections are greater than one (i.e., negative soil arching). The measured lateral earth pressure data verified that the lateral pressure induced by compaction was constant with depth within the pipe range. The measurement of the displacements of ribs at the springlines of pipes in both sections demonstrated that the ribs in the crushed stone section deformed more than those in the AB3 section. A visual inspection of the exhumed pipes did not find any obvious damage to the pipe ribs and liner. Overall, the SRHDPE pipe performed well in these two types of backfill material during installation.

Performance of Buried Steel-Reinforced High-Density Polyethylene (SRHDPE) Pipes in a Shallow Cover under a Test Truck Load in a Full-Scale Field Test

Extensive laboratory tests were conducted in the test box at the University of Kansas (KU) to measure the response of Steel-Reinforced High-Density Polyethylene (SRHDPE) pipes. The laboratory tests conducted have some limitations, for examples, on installation conditions. To provide information that can improve the understanding of the short-term and long-term behavior of the pipe, field tests were conducted. Strain gages to measure steel and plastic strains, displacement transducers to measure the changes in diameter of the pipe, pressure cells around the pipe to measure the distribution of the pressure were installed and data were collected both during the installation and loading of the pipe. In this paper, the deflection of the pipe under a test truck loading is presented. Based on the field testing on the SRHDPE pipes, it can be concluded that (1) the deflections measured under the test truck for the SRHDPE pipe were much smaller than the permissible deflection of 7.5 % according to the Kansas Department of Transportation (KDOT) pipe and culvert specification (2007) during installation, (2) modified Iowa formula over predicted the deflection of the pipe under the applied load, and (3) the relation proposed by Masada (2000) can be used to determine ratio of the horizontal to vertical deflection of a buried SRHDPE pipe.

Mechanistic-Empirical Model to Characterize Rutting in Unpaved Road with a Shallowly Buried SRHDPE Pipe

The Mechanistic-Empirical (M-E) road design guide has been more and more used in the road design to consider the long-term performance of the road. In some road sections, there is pipe buried in the road for the sake of drainage. To investigate the effects of the shallowly-buried pipe on the permanent deformation of road surface under cyclic traffic loading, one laboratory test of an unpaved road with buried steel-reinforced high-density polyethylene (SRHDPE) pipe under cyclic loading was conducted. In the tests, a 61-cm diameter SRHDPE pipe was buried in a compacted sand trench covered by AB-3 and sands. A M-E model was calibrated with the laboratory test data and adopted to predict the permanent deformations of the road under cyclic loading. It was found that the M-E model could simulate the road permanent deformation well under cyclic loading before the road failed. Parametric study shows that pipe stiffness had considerable effects on the road deformation under cyclic traffic loading.