جستجوی مقالات مرتبط با کلیدواژه « پایه های پل » در نشریات گروه « آب و خاک »

Scour is among the most critical topics in river engineering. A large number of bridges around the world are destructed mainly due to ignoring the hydraulic function in the design of bridges. The use of roughness, collars, submerged plates, and protective piles are among the methods for controlling and reducing local scouring. This study investigated the effect of protective piles in controlling and reducing scouring around spindle-shaped piers. According to the experimental results, by installing 5 piles at an angle of 30˚ with a relative distance (L/D) of 0.5, scouring decreased by 20% relative to the pile-less spindle-shaped pier. This scour reduction can be attributed to the transport of sediments around the pile toward the pier and accumulation of sediments in the middle of piles and in front of the spindle-shaped pier. The other factor reducing local scour is the change in the flow regime and reduced velocity and vortices in front of the spindle-shaped pier. Moreover, as the relative velocity (V/Vc, the ratio of the flow velocity to the critical velocity) increased from 0.54 to 0.95, scouring increased by 165.4% on average. The water flow colliding the spindle-shaped pier and the formation of a downward flow cause scouring. An increase in the flow velocity also increases the vertical velocity and vortices and thereby scouring. The mathematical model simulated by Flow-3D is consistent with the physical model showing an acceptable error rate of 4.3%.

The construction of bridges within the river beds often makes changes to the shape and direction of the rivers. These changes take the natural actions of the river, that one of them is the local scouring around the bridges' piers and can cause annually damage. Therefore, many researches have been carried out to control and reduce the scouring. One of the methods presented by researchers is using slot at piers.  In present study, the effect of Pier Opening Area on local scouring around the pier with rectangular section is experimentally investigated. For this purpose, piers with square shape slots and different dimensions were used. The piers were tested at three levels (near the water level, on the bed and under the bed) and four Froude numbers.  The result showed that the maximum scouring depth and the volume of hole scour had a direct relationship with slot level relative to bed and Froude number and an inverse relationship with Pier Opening Area. The best performance belonged to the slot with greater dimensions which was located under the bed level in the minimum Froude number condition that reduced the depth of scouring about 55.4 percent.

The local scour at pile is the main reason for bridges failure. Although numerous researches have been done on scouring, the appropriate equation to predict scour at bridges foundation has not been presented yet. In this research, an experimental study on clear water scour at pile groups under steady flow at threshold velocity is presented. Uniform bed material with median particles size of 0.8 mm, in a 46 m long, 1.52 m wide and 1.9 m deep flume were used. The objectives of this study are to present changes in scour at multiple piles due to the pile arrangements and present empirical relationship to estimate the scour depth at multiple piles with different arrangements. Wide ranges of pile group arrangements are studied when the diameters of piles were 60 mm and 42 mm. The number of piles in line with flow (m) and normal to flow (n) were regularly increased at each successive experiment. In total, 40 experiments were carried out used possible arrangements of pile group where maximum number of n and m were 4 and 10 respectively. It was observed that the scour at pile group is affected by pile arrangements. The collected data were used to propose a new empirical equation to compute effects of the studied variables (m and n). The outputs of this research can be used to improve the pile group arrangement procedure to