Evaluation of Total Stress and Arching Coefficient by Back Analysis with Result of Stepwise Construction (Case Study: Marvak Earth Dam)

Arching in core dam can reduce tension and create scour and clay scrub damage, so it is always a major issue in the earth's dams. In this research, Geostudio software, which is a powerful software for limited components, is used to study the total stress and aridity coefficient of Marvak earth dam. In modeling the dam, a Mohr-Coulomb behavioral model has been used and the effect of the construction has been considered. By analyzing the stress-strain during the construction of the dam and the effect of the construction, the results of total stress and arching coefficient were evaluated and compared with the results of the instrumentation. Multivariate regression and coefficient of determination were used to fit the observed and predicted data and the value of R2= 0.9834 was obtained, which is a very good agreement between the observed and predicted arching data. The results indicate that as the embankment increases, the total stresses also increase, and the highest arching percentage from the beginning to the end of the construction phase is 58 percent and at the third of the core of the foundation. Due to the great effect of consolidation on the arching severity, the speed of construction should be chosen in such a way as to be part of the consolidation of the underlying layers before the upper layers are applied. It is also possible to reduce arching by choosing the appropriate filter between the core and the shell and using materials with a Poisson's ratio.