New developments in the Integrated Stress Determination Method and their application to rock stress data at the Äspö HRL, Sweden |
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Authors: | D Ask |
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Affiliation: | aDivision of Engineering Geology, Royal Institute of Technology, Stockholm, Sweden;bDivision of Rock Mechanics, Luleå University of Technology, Luleå, Sweden;cSwedPower Co., Luleå, Sweden |
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Abstract: | The Integrated Stress Determination Method (ISDM) is a powerful tool for estimating the regional stress tensor from in-situ measurements of local stress tensors using a wide variety of stress measuring techniques. This study presents new developments of the ISDM: The stress field may be described with up to 12 model parameters; and is applicable to data from CSIR- and CSIRO HI-type of overcoring devices, hydraulic fracturing, hydraulic tests of pre-existing fractures (HTPF), as well as to combined data sets. Furthermore, in combined data sets, the hydraulic fracturing and/or HTPF data may be used to constrain the average elastic parameters, Young's modulus and Poisson's ratio.The new ISDM developments were applied to the extensive and recently re-analysed rock stress data at the Äspö Hard Rock Laboratory. The results reveal a good fit of the re-analysed data. Overall, the re-analysis indicates that the stress field at Äspö HRL is relatively well constrained and consistent with depth. The NE-2 Fracture Zone influences the stresses, and dividing the regional stress field into a NW and a SE stress domain. When the hydraulic fracturing data were used to constrain the average elastic parameters, Young's modulus, E, and Poisson's ratio, ν, quite similar results were obtained ( and ν=0.33) compared with results from biaxial tests of overcore samples ( and ν=0.26). |
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Keywords: | ISDM State of stress Hydraulic fracturing Overcoring Ä spö HRL |
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