Experimental Study on the Optimum Installation Depth and Dimensions of Roughening Elements on Abutment as Scour Countermeasures

Abstract

The causes of many bridge failures have been reported to be local scour around abutments. This study examines roughening elements as devices with which to intercept the downflow responsible for the formation of the principal vortex, which is what triggers local scour around abutments. Two vertical wall abutments with different widths were examined under four different hydraulic conditions in a clear-water regime. Elements with different thicknesses (t) and protrusions (P) with the same dimensions, (P = t = 0.05 L, 0.1 L, 0.2 L, and 0.3 L, where L is the length of the abutment) and with varying depths of installation (Z) were considered. Elements were installed in two positions: between the sediment surface and water elevation and buried within the sediment. To determine the optimum depth of installation, one element was first installed on the sediment surface, and the number of elements was increased in each subsequent test. The results show that installing elements between water surface elevation and the sediment’s initial level did not show any defined trend on scour depth reduction. However, the optimum installation depth of the elements is 0.6–0.8 L below the initial bed level. Moreover, the roughening elements with thickness and protrusion of P = t = 0.2 L resulted in the most effective protection of the foundation. The best arrangement, (P = t = 0.2 L and Z = >0.6–0.8 L) reduced the maximum scour depth by up to 30.4% and 32.8% for the abutment with smaller and larger widths, respectively.

Application of Water Quality Index in Assessing water Quality: A Case Study of the Shatt Al Arab River.

“…(5) SIi is the sub index of the I th parameter and I represents the number of the parameter taken into consideration. In Table 1, The ideal values and unit weights for the water quality variables and their standard values are shown [17]. It was noted that the concentration of various parameters in Table 3 was high and had surpassed the acceptable limit for the area under consideration.…”

“…The final weight of each variable is then obtained by dividing each temporary weight by the total of all the temporary weights [15,16]. An artificial neural network approach has recently been used to estimate water quality, saving time and effort [17]. WQI has an advantage over other evaluation techniques since it can ascertain the ultimate state of the water quality without having to interpret each variable [18].…”

Location and Extents of Scour Hole around an Erodible Spill-through Abutment under Clear Water Condition and the Abutment Classification

“…In addition to the interaction among different scour components, Zolghadr et al [22] and Nabaei et al [23] explored the effect of artificial roughening elements and vegetation on the maximum scour depth by conducting laboratory experiments with several different widths of the fixed abutment. Fathi et al [24] also conducted a laboratory experiment Water 2023, 15, 4155 2 of 16 and they pointed out, because of rock riprap sliding over time during the scouring, the point of the maximum scour relocated from the upstream corner to the downstream of the abutment.…”

Environmental Hydraulics, Turbulence, and Sediment Transport, Second Edition

“…Properly scaled riprap aprons also reduced the required riprap volume significantly. Submerged vanes improved the riprap stability and reduced edge failure, particularly with square-shaped riprap layers [11]. The effectiveness of roughened elements for mitigating bridge abutment scour were tested on rectangular abutments, with the optimal installation depth found to be 0.6-0.8 times the abutment length.…”