Evaluation of Low Stress and Cracking Zones in the Core of a High Rockfill Dam in a Relatively Narrow Canyon Using 3D Numerical Modeling

This paper documents the development of low stress and fracture zones in the core of the 177-m-high Masjed-E-Soleyman rockfill dam--which has a clay core and was built in a relatively narrow canyon--using three-dimensional (3D) numerical modeling and analyses during both the construction and impounding of the dam. The analysis was based on effective stress parameters, which enabled the computation of pore water pressures in the core caused by the construction and impounding loadings. The analysis was successfully verified by comparing the results to data measured by dam instruments. Two criteria for assessing the low stress and fracture zones in the core were utilized: (1) zones in which the minimum effective principal stresses were under tension conditions, irrespective of the water-content-related characteristics of the core; and (2) zones in which combinations of the stress ratio and liquidity index--based on the principles of critical-state soil mechanics--caused the soil to fracture. The results of the analyses indicated that the core of the dam in its upper elevations and in the vicinity of the abutments suffered tensile stresses and fracturing, based on both criteria. This finding compares favorably with what happened to the prototype in the field after impounding.