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Information Journal Paper

Title

The experimental investigation of the maximum depth and length of pit holes created by bed material removal under subcritical flow condition

Pages

  111-130

Abstract

 Background and Objectives: The removal of sand and gravel from the bed and the banks of the Rivers causes change in the hydraulic and hydrology conditions, increased erosion of the bedding and the banks of the River, also the destruction of existing structures along the River. The purpose of the present study is to investigate the maximum depth and length of the created pits migration due to the River material removal. Materials and Methods: For this research, a rectangular flume with length, width and height of (5, 0. 3, 0. 45) meters with a constant slope was used. The pit holes with different sizes and under the relative velocities of 0. 83, 0. 89, 0. 94 and 1 have been operated for the state of with or without gate by using two sediments mean dimensions of the 0. 15, 0. 6 mm. In this study, the duration of the experiments, were fixed to 1 and 1. 5 hours respectively for state of with and without gate, that the equilibrium time for both of them was the last 15 minutes. A 3D laser scanner was used to take data from a three-dimensional profile of the bed in both state, after disconnecting water and recording the depth of water in different places. Also, from the side view of the experimental flume, the digital photos were taken to view the conditions of the pits migration at different time intervals. Afterward, using the MATLAB, Tec-Plot 360, Excel and Grapher software tried to rearrange and reconfigured data and drawn graphs were taken. During the experiments, the bedforms at the up and downstream of the Created pits were observed and their temporal variations were recorded. Results: The results of the experiments showed that with decreasing of the Froude number, pits depth and also by creation of the secondary flow inside the holes, the dimensionless ratio of the y H decreases and reversely, the dimensionless parameters of the y L and y B increases. On the other hand, it was concluded that by increasing the shear stress and Froude number, the dimensionless ratio of the V u*cr will increase. The longitudinal profiles and 3D view of the pits migration at the all of the Hydraulic and sediment conditions were observed and depicted. At the end, the experimental equations for the maximum of scouring length and depth for the rectangular pit were presented along with the sensitivity analysis. In general, it was shown that the submerged angle of repose of materials ( ) has the greatest effect on the increase and y H has the greatest effect on reducing the length and depth of the scouring pit. Conclusion: The results of the experiments have been illustrated by presenting the dimensionless relationships for maximum depth and length of the pits for both state of with and without gate in both sediments mean dimensions of the 0. 15, 0. 6 mm under subcritical flow conditions and showing the maximum and minimum effect of parameters and the use of sensitivity analysis for the obtained relationships. It was proved that the lowest error percent for maximum scour depth was observed in the 0. 15 mm mean sediment particles in state of without gate, having the relative error of 2. 98% and RMSE of 0. 23. Also, the lowest error percent of the maximum scour length is related to a 0. 6 mm mean sediment particles with a relative error of 4. 75% and an RMSE of 0. 5.

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    APA: Copy

    DANESHFARAZ, R., CHABOKPOUR, J., & Dasineh, M.. (2019). The experimental investigation of the maximum depth and length of pit holes created by bed material removal under subcritical flow condition. JOURNAL OF WATER AND SOIL CONSERVATION (JOURNAL OF AGRICULTURAL SCIENCES AND NATURAL RESOURCES), 26(1 ), 111-130. SID. https://sid.ir/paper/156512/en

    Vancouver: Copy

    DANESHFARAZ R., CHABOKPOUR J., Dasineh M.. The experimental investigation of the maximum depth and length of pit holes created by bed material removal under subcritical flow condition. JOURNAL OF WATER AND SOIL CONSERVATION (JOURNAL OF AGRICULTURAL SCIENCES AND NATURAL RESOURCES)[Internet]. 2019;26(1 ):111-130. Available from: https://sid.ir/paper/156512/en

    IEEE: Copy

    R. DANESHFARAZ, J. CHABOKPOUR, and M. Dasineh, “The experimental investigation of the maximum depth and length of pit holes created by bed material removal under subcritical flow condition,” JOURNAL OF WATER AND SOIL CONSERVATION (JOURNAL OF AGRICULTURAL SCIENCES AND NATURAL RESOURCES), vol. 26, no. 1 , pp. 111–130, 2019, [Online]. Available: https://sid.ir/paper/156512/en

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