DEVELOPMENT OF NEW EQUATIONS TO DETERMINE IN SITU STRESSES FROM BOREHOLE SLOTTERTEST RESULTS

Abstract

To establish a rock structure model, it is essential to estimate in situ stress magnitude and its orientation at site formations. Borehole slotting is one of the newest methods in estimating state of stress. Bakhtiari dam site in Iran consists of seven various zones with different geological properties of materials. Many laboratory tests and site excavations have been performed to determine rock properties. Additionally, the state of stress must be determined in all the zones. But there are problems with cost and time to be consumed in using in situ stress measurements. To overcome these problems, this paper suggests correlations between principles stresses and application of 3D borehole slotter test in Bakhtiari dam. At first stage, through statistical analysis of the experimental results certain equations have been developed between measured principle stresses. Then, for validation of the proposed equations and investigation of depths limitations of borehole slotter test, these equations have been cross checked with hydraulic fracturing equations presented by other investigators. Results of this research show that there are good relationships between components of principle stresses obtained from borehole slotting with vertical stress of the region. It is, also, shown that stresses calculated by these equations carry a good correlation with hydraulic fracturing results up to depths of 44m.