Numerical investigation of extra large flat jack testing of bakhtiyari dam project

Accurate determination of in situ rock mass design parameters such as deformation modulus is an essential element of the design of underground openings. The first objective of this research was to numerically simulate the extra large flat jack (ELFJ) test. In conventional flat jack testing, the large flat jack (LFJ) coefficients proposed by LNEC Corporation are used to calculate the rock modulus. This leads to erroneous results when using other types of flat jacks. A precise 3D numerical model of a real flat jack test condition was constructed and the ELFJ coefficients were computed numerically as a function of important test parameters. The second objective of the work was to apply the 3D numerical findings to the flat jack field tests conducted at the Bakhtiyari Dam site project, Iran. These tests were aimed at determining the in situ rock mass deformation modulus to be used in the design of the dam structure and underground openings associated with the Bakhtiyari Dam. The dam left abutment and associated test gallery were simulated according to valley topography and actual test gallery dimensions. The objective was to model the problem boundary condition as close to reality as possible. The analysis results showed that the rock mass modulus under the expected abutment loading levels is about 13 GPa.