Effects of Chiangrai earthquake to Mae Ngat dam from instrument interpretation and finite element simulation

Abstract

This is a study about the stress, displacement and factor of safety of Mae Ngat Dam. According to the field study and the analysis by finite element method in a 2D nonlinear plane strain, using the Elasto-Plastic soil model with Mohr-Coulomb failure criteria to analyze acceleration, pores water pressure, deformation and factor of safety. The analysis was done using dynamic method with the intensity that had happened according to the earthquake in Phan, Chiangrai, in northern part of Thailand, where the earthquake measured 6.3 Richter. The location of Mae Ngat Dam is 150 kilometers away from the epicenter. It was found from the model under seismic force, that the acceleration had even diffusion. The highest acceleration was at the crest of the dam. There was mostly horizontal displacement, analyzing 5.7 centimeters and the most vertical displacement was analyzed at 3.3 centimeters. According to the earth zone dam seismic force, the factor of safety was 1.856, which was higher than the minimum criteria of the safety factor by the Department of Irrigation 1.500. The seismic force had not much effected to the dam. It can be concluded that Mae Ngat Dam is still safe from this earthquake.