Practical criteria for assessment of horizontal borehole instability in saturated clay

Lan, Haitao; Moore, Ian D.

doi:10.1016/j.tust.2018.02.002

Cited by 9 publications

(3 citation statements)

References 50 publications

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“…The failure model caused by pressurised drilling fluids in clays is considered to be either tensile or shear failure. [57][58][59] The limit failure pressure varies with the failure model significantly. In general, the tensile fracture pressure is lower than that with shear failure.…”

Section: Estimation Of Maximum Mud Pressure In Horizontal Directionmentioning

confidence: 99%

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Two‐dimensional elastoplastic analysis of cylindrical cavity problems in Tresca materials

Zhuang

2019

Num Anal Meth Geomechanics

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Summary This paper presents analytical elastic‐plastic solutions for static stress loading analysis and quasi‐static expansion analysis of a cylindrical cavity in Tresca materials, considering biaxial far‐field stresses and shear stresses along the inner cavity wall. The two‐dimensional static stress solution is obtained by assuming that the plastic zone is statically determinate and using the complex variable theory in the elastic analysis. A rigorous conformal mapping function is constructed, which predicts that the elastic‐plastic boundary is in an elliptic shape under biaxial in situ stresses, and the range of the plastic zone extends with increasing internal shear stresses. The major axis of the elliptical elastic‐plastic boundary coincides with the direction of the maximum far‐field compression stress. Furthermore, considering the internal shear stresses, an analytical large‐strain displacement solution is derived for continuous cavity expansion analysis in a hydrostatic initial stress filed. Based on the derived analytical stress and displacement solutions, the influence of the internal shear stresses on the quasi‐static cavity expansion process is studied. It is shown that additional shear stresses could reduce the required normal expansion pressure to a certain degree, which partly explains the great reduction of the axial soil resistance due to rotations in rotating cone penetration tests. In addition, through additionally considering the potential influences of biaxial in situ stresses and shear stresses generated around the borehole during drillings, an improved cavity expansion approach for estimating the maximum allowable mud pressure of horizontal directional drillings (HDDs) in undrained clays is proposed and validated.

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Section: Estimation Of Maximum Mud Pressure In Horizontal Directionmentioning

confidence: 99%

“…The failure model caused by pressurised drilling fluids in clays is considered to be either tensile or shear failure . The limit failure pressure varies with the failure model significantly.…”

Section: Estimation Of Maximum Mud Pressure In Horizontal Directionalmentioning

confidence: 99%

Two‐dimensional elastoplastic analysis of cylindrical cavity problems in Tresca materials

Zhuang

2019

Num Anal Meth Geomechanics

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“…The failure of such shallow cavities is controlled by tensile stresses (developed at the crown of the cavity) in the case of cohesive materials and by shear stresses (which originate 'blow-out') for cohesion-less media Lan & Moore (2017). Regardless of the nature of the soil, the use of cavity expansion theories (such as the Delft equation) results in an overestimation of the maximum pressure that can be safely imposed to the cavity as shown in (Kennedy et al, 2006;Xia & Moore, 2006;Lan & Moore, 2018) for purely cohesive materials and in (Lan & Moore, 2020) for frictional soils. For instance, the Delft equation overestimates the maximum pressure by by 90%-170%.…”

Section: Introductionmentioning

confidence: 99%

Deformation and failure mechanisms of granular soil around pressurised shallow cavities

et al. 2023

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The deformation patterns and failure mechanisms of pressurised cavities at shallow depth are relevant to many geotechnical applications, including tunnelling and horizontal directional drilling. In this paper, an experimental study of a reduced-scale pressurised cavity under geostatic stress is presented, in order to measure the effect of cavity length, vertical stress and soil density on soil deformation and failure. X-ray computed tomography is used to acquire images of the system at key stages of the cavity inflation process. A closed-shaped failure region developed around the cavities, beyond which shear planes of elliptic paraboloid shape formed, extending from the bottom of the cavities all the way to the free surface. The plane-strain assumption did not hold beyond the central portion of the longest cavity tested (L = 6D). The volumetric strain and porosity changes inside the shear bands showed significant dilation in dense specimens, but contraction in loose specimens. The average orientation and the thickness of the shear bands were in agreement with those found in the literature for passive arching mechanisms (anchoring). The orientation of the principal strains around the cavity follows catenary shapes, similar to those displayed in active trapdoor mechanisms.

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Model tests for observing the deformation characteristics of micropile boreholes during drilling in a soil-limestone mixture

Ying

Siddiqua

et al. 2021

Bull Eng Geol Environ

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Practical criteria for assessment of horizontal borehole instability in saturated clay

Cited by 9 publications

References 50 publications

Two‐dimensional elastoplastic analysis of cylindrical cavity problems in Tresca materials

Two‐dimensional elastoplastic analysis of cylindrical cavity problems in Tresca materials

Deformation and failure mechanisms of granular soil around pressurised shallow cavities

Model tests for observing the deformation characteristics of micropile boreholes during drilling in a soil-limestone mixture

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