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Evaluating the potential for sliding failure in boreholes in fractured rock
Published in Hans Peter Rossmanith, Mechanics of Jointed and Faulted Rock, 2020
When a homogeneous, linear, elastic rock mass under stress is penetrated by a cylindrical, smooth borehole, then the Kirsch equations given by Bradley (1979) and by Hsiao (1987) describe the state of stress of rock in the vicinity of the borehole. Input to these equations are the longitudinal normal stress (σZ) acting parallel to the borehole axis, the major and minor normal stresses (σmaj and σmin, respectively) acting in a plane perpendicular to the borehole axis, and the shear stresses acting perpendicular to the three normal stresses.
Continuous cast lining – A solution to downhole problems
Published in W.A. Hustrulid, G.A. Johnson, Rock Mechanics Contributions and Challenges: Proceedings of the 31st U.S. Symposium, 2020
When a hole is being drilled the stresses in the ground close to the borehole are rearranged, and if only elastic deformation occurs, the Kirsch equations give a good solution of the stress field. In most cases however, the deformation is plastic and also time dependent.
Sand production onset using 3D Hoek–Brown criterion and petro-physical logs: a case study
Published in Geomechanics and Geoengineering, 2022
Abbas Khaksar Manshad, Farhad jafari, Sarkar Muheedin Hama, Mohammad Tabaeh Hayavi, Jagar A. Ali, Alireza Keshavarz, Kamal Kolo
Stress concentration around the wellbore can be caused by breakouts, fractures, or failures. Prior to well design it is necessary to good understanding of stress on rock around the well bore (Xiao and Vaziri 2011). In the vertical well which is drilled parallel to the vertical principal stress, around bore-hole stress will concentrate and this can be described by the Kirsch equations. As illustrated in (Figure 1) the development of a round and hollow opening (like a wellbore) leading to the stress trajectories to bend in such a way as to be parallel and perpendicular to the wellbore wall because it is a free surface which cannot sustain shear traction. This is illustrated by the bunching up of stress trajectories at the azimuth of minimum horizontal stress, which shows strongly amplified compressive stress (Papamichos et al. 2010). On the other hand, the expansion out of stress trajectories at the azimuth of maximum horizontal stress shows a decrease in compressive stress.
Understanding present-day stress in the onshore Canning Basin of Western Australia
Published in Australian Journal of Earth Sciences, 2021
A. H. E. Bailey, A. J. M. Jarrett, E. Tenthorey, P. A. Henson
Horizontal stress orientations can commonly be identified from wellbore-failure features within drill holes (Bell, 1996a). Two main wellbore-failure features are commonly used as stress indicators: borehole breakouts (BOs) and drilling induced tensile fractures (DITFs) (Figure 6). As rock is removed during drilling, stress is concentrated around the wellbore; circumferential stress is maximised at the minimum horizontal stress azimuth and minimised at the maximum horizontal stress azimuth (Gough & Bell, 1981; Haimson & Herrick, 1986; Maloney & Kaiser, 1989; Zheng et al., 1989; Zoback et al., 1985) (Figure 6). Borehole failure through the creation of BOs and DITFs is a result of stress perturbations that exist under such conditions (Kirsch, 1898; Plumb & Hickman, 1985; Zheng et al., 1989; Zoback et al., 1985). BOs are zones of compressive failure owing to the redistribution of in situ stresses around a borehole, as defined by the Kirsch equations (Jaeger et al., 1979; Kirsch, 1898), and form through wellbore spalling along the minimum horizontal stress azimuth, whereas DITFs represent zones of tensile failure at the borehole wall in the maximum horizontal stress azimuth (Figure 6).
A data-driven fuzzy model for prediction of rockburst
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2021
Ashkan Rastegarmanesh, Mahdi Moosavi, Ahmad Kalhor
Wang et al introduced the ratio of maximum compressive tangential stress to the uniaxial compressive stress of rock (Ts) as a rockburst indication criterion. Based on a comprehensive study, it was proposed if Ts is smaller than 0.3, no rockburst, if between 0.2 and 0.5, light rockburst, if between 0.5 and 0.7, strong rockburst and if it is more than 0.7 then violent rockburst should be expected (Wang, Li, and Li 1998a). Maximum compressive tangential stress is the highest compressive stress in tangential direction on the circumference of the underground opening which can be calculated via theoretical techniques (Kirsch equations) or numerical modelling. Alternatively, the aforementioned parameter can be acquired from monitoring of the opening with appropriate instrumentation techniques.