Study of Guidelines for Designing Irrigation Weirs of the Royal Irrigation Department Luang Chumchon Weir Project Mae Van Subdistrict, Phrao District, Chiang Mai Province

Abstract

The purposes of this study were (1) to study the principles of designing irrigation dams in accordance with academic principles and engineering principles used in the Royal Irrigation Department (2) to be a guideline in the work of the designer in designing the irrigation weir to be correct according to engineering law. This research is a combinatorial research, a research of qualitative data combined with quantitative data. The study tools were studies, research, interviews with 10 engineers who designed weirs in irrigation offices and used the analysis and synthesis results to design a Luang Chumchon weir project according to the variables that have been determined, the results of the study were analyzed and summarized as follows.

The qualitative data analysis revealed that the design engineer had an average of about 8 years of working experience in irrigated weir design, the design of the irrigation weir of the Royal Irrigation Department must be designed according to academic principles and engineering principles according to the USBR, use knowledge in Hydraulics Engineering, Structural Design and requirements and criteria set by the Royal Irrigation Department, including the qualifications and scope of work of the design engineer must be permitted by law, operations are in the same direction. Luang Chumchon weir project design analysis MaeVan subdistrict, Phrao district, Chiang Mai province, it is an Ogee weir with a weir ridge length of 25 m. Type II Energy Decomposition Building, it the length of the basin (Ls) is 20 m., the width (Ws) is 25 m., this has a height of 4.20 m. from the Basin floor level (Hs) and when checking the stability of the weir which checks the floor thickness in the water permeable point that is the risk point multiplied by the safety value according to the specifications, the thickness is 1.0 m. and 0.5 m. and in the skid inspection it was equal to 3.38, the rollover inspection was equal to 6.45, greater than the safety ratio Factor of safety and the soil load inspection, it has a maximum value of 13.766 tons/m.2 which is less than the load capacity of the soil Therefore, the soil under the weir base can safely support the weight of the weir. Design of a dimensional retaining wall with a base width (B) of 4 m., thickness (TT, TH) 0.5 m., inner base width (B1) 1.2 m., outer base width (B2) 2.3 m., mid-wall base thickness (TW1) 0.5 m. And wall top thickness (TW2) 0.3 m., and when it was taken to check the stability of the retaining wall, it was found that Passes the Factor of safety ratio requirements, which are designed in accordance with the specified variables. And this study can be used as a guideline for designing water-resistant weirs.