CONTROL AND REDUCTION OF LOCAL SCOUR AT BRIDGE PIER GROUPS USING SLOT

摘要

The main cause of concern about the stability of bridge foundation is the occurrence of scour around the piers. Therefore, there is an interest in finding reliable ways to reduce and control local scour depth and, thereby, requisite pier embedment depth. The use of slot through a pier is one of the new proposed methods for controlling and reduction of local scour at bridge piers. The scour-reduction efficacy of a slot through a single pier has already been established in earlier studies. When the scour process is due to the presence of pier groups, some mechanisms such as reinforcing, sheltering and shed vortices occur that make the phenomenon more complex. Furthermore, the group effects will alter with changes in pier spacing and flow angle of attack. This study examines the effect of using slots through the pier groups at clear water condition. The models consist of two and three circular-shaped piers in line with diameter of 0.02m and pier spacing of twice and four times the pier diameter. The slots width and length were one-fourth and twice the pier diameter, respectively. The pier groups were tested for four angles of attack (0°, 5°, 10° and 15°). The results of the pier groups were compared with the results of a single pier with no slot. The efficacy of slot at different angles of attack and pier spacing was studied. The results showed that reinforcing and sheltering effect on scour depth change by changing pier spacing and angle of attack. According to the results, slot efficacy increased with increasing pier spacing and decreased with increasing angle of attack.