Study and Analyze of Baanprongtapetch Regulator in Phetchaburi Province, Thailand

Abstract

This study investigates and analyzes the hydraulic characteristics of a regulator structure through the application of Computational Fluid Dynamics (CFD), developing a three-dimensional numerical model of a regulator specifically designed by the researcher. The research further examines and compares seepage beneath the foundation and uplift pressure under the structure, utilizing Lane’s Weighted Creep Theory and flow net analysis, with validation through finite element analysis. The design of the regulator headworks was based on site-specific data, including permeability tests from boring logs and topographic surveys conducted at Ban Prong Ta Phet, Phetchaburi Province, Thailand.

Key findings from the hydraulic analysis reveal that the simulated hydraulic jump characteristics, including the pre-jump (y2) and post-jump (y3) depths, closely correspond to those predicted by the energy equation and hydraulic jump theory. The energy dissipation performance of the USBR Type III stilling basin, employed in the regulator design, is highest at smaller gate openings and decreases as the gate opening increases. Additionally, increasing the distance between the baffle piers and the chute blocks enhances the energy dissipation efficiency, with the optimum spacing identified as three times the standard USBR recommendation.

From the geotechnical perspective, the study indicates that a high soil permeability coefficient results in seepage trajectories that cross the cutoff wall, deviating from the assumptions of Lane’s Weighted Creep Theory, which presumes seepage follows the underside of the foundation structure. Uplift pressures obtained from flow net analysis and finite element simulations are consistent but are generally higher than those estimated by Lane’s theory, impacting the design of the base slab thickness. Although the Royal Irrigation Department (RID) standard design practice assumes a safety factor of 1.30, site-specific soil conditions at Ban Prong Ta Phet, classified as silty sand (SM), support a higher safety factor of 1.50 with a minimum cutoff wall spacing of 9 meters.