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Abstract

Pipes made of corrugated metal structural elements have a roughness that differs from the roughness of technically smooth concrete pipes. The hydraulic operating conditions of corrugated pipes due to increased roughness of the walls have their own characteristics. The experimental works on determining the roughness coefficients of the inner surface of metal spirally-twisted corrugated pipes with a polymer and zinc coating are described in the paper. Two standard dimensions of corrugated pipes are considered: with a diameter of 500 mm with a corrugation, the corrugation dimensions are 68 × 13 mm; and with a diameter of 1,000 mm with corrugation dimensions of 125 × 26 mm. The non-pressure mode of flow in the pipe with various degrees of filling (02; 0.4; 0.6 and 0.8 for several slopes of the pipe position: 0.03; 0.02 and 0.01) is studied. The experimental setup is located in a tray with 2,000 mm width and 800 mm height. During the experiments, the water flow rate in the pipe, which determines the degree of its filling, is measured, as well as piezometers record the distribution of flow depths along the pipe length and control the flow uniformity. Based on the measured values, the hydraulic characteristics of the flow, namely, area of effective cross-section, wetted perimeter and hydraulic radius, using of which the roughness coefficient value is calculated by Chezy’s formula, are computed. The roughness coefficient values for pipes with 1000 mm diameter at high degrees of filling are obtained using the theory of similarity. The research results have showed that the determined roughness coefficients for pipes of the considered diameter depend practically only on the pipes diameter and the corrugation dimensions, and do not depend on the slope of the pipe location, degree of filling, and lining material. Based on the results of the performed work, the quantitative values of the roughness coefficients for each pipe diameter are recommended.