Displacement-based numerical back analysis for estimation of rock mass parameters in Siah Bisheh powerhouse cavern using continuum and discontinuum approach

Abstract

Back analysis as a modern observational method is a helpful technique for evaluation of soil and rock mass parameters and prediction of their mechanical behavior. Most back analysis techniques in geotechnical engineering problems are based on the methods that utilize the monitored data of stresses, strain and displacements. This technique is one of the prominent processes in design and evaluation of the stability of caverns that reveals the shortcoming of supports design and in fact is essential for evaluation of design parameters. Siah Bisheh pumped storage project with complex geometry, changeable geological formations and diverse geotechnical properties of rocks, is under construction on the Chalus River at the north of Iran. The underground complex consists of three main caverns placed near each other. In this study displacement based direct back analysis using continuum and discontinuum numerical modeling were applied and geomechanical properties of rocks, stress ratio and joints parameters were identified and then calculated parameters were compared with the initial design parameters. Both continuum and discontinuum modeling results were in a good agreement with measured displacements which confirm the numerical modelings correctness and back analysis results.