Stability analysis of temporary concrete traffic barriers during extreme flood

Date

2010

Authors

Ali, Md Kausar

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Abstract

The primary objective of this research study was to determine the stability of temporary concrete traffic barriers (TCTBs) such as single slope, F-shaped, modified, and low speed barriers used by Texas Department of Transportation (TXDOT) during extreme flood. The stability of TCTB was determined in terms of factor of safety against sliding and overturning at different critical conditions during extreme flood. At first, the coefficients of friction between the TCTB surface (concrete) and five different types of pavement surfaces, such as concrete, asphalt, base, subbase, and subgrade surfaces were determined following ASTM C1028--07 standard. The results of the experiments show that the coefficient of friction between the TCTB surface and concrete, asphalt, base, subbase, and subgrade surfaces varies from 0.78 to 0.98, 0.62 to 0.76, 0.54 to 0.75, 0.50 to 0.69, and 0.61 to 0.88 respectively. The coefficient of friction decreases approximately 18--22% when the bearing stress increases from 1 psi (stress caused by standard weight assembly) to 2.0 psi (higher field stress caused by weight of TCTB) and then remains unchanged for the concrete surface. For the asphalt surface, the coefficient of friction decreases approximately 22--23% when the bearing stress increases from 1 psi to 2 psi and then decreases slowly. Most of the cases, the coefficient of friction was higher in dry surfaces than that in wet surfaces except subbase and subgrade. Perhaps the presence of clay particles in subbase and subgrade increased the coefficient of friction due to cohesion between surfaces at wet condition. The statistical analysis of the coefficient of friction shows that there is no significance difference between the mean coefficient of friction for all of the surface combinations. However, this observation might change with higher number of sample size. The coefficient of friction decreases significantly due to the presence of dirt at the bottom of the TCTB surface and for both concrete and asphalt surfaces.

Stability of the TCTB is analyzed for four different flood Scenarios that might be encountered during extreme flood. The single slope traffic barrier is unstable either against sliding or overturning for all four flood Scenarios. The 33" F-shaped and the modified traffic barriers are stable only for one Scenario, but unstable for all other Scenarios. The stability of the low speed traffic barriers is usually higher compare to other TCTBs for all Scenarios. The factor of safety against sliding and overturning varies significantly with the cross slopes of the roadway. Similarly, the factor of safety against sliding varies significantly with the variation of coefficient of friction.

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Keywords

Barrier Overturning, Barrier Sliding, Barrier stability, Barriers in Flood, Friction Coefficient, Traffic Barriers

Citation

Department

Civil and Environmental Engineering