Deformation and failure mechanisms of granular soil around pressurised shallow cavities

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 pres...

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Bibliographic Details
Published in:Géotechnique 2023-03, Vol.73 (3), p.265-280
Main Authors: Patino-Ramirez, Fernando, Anselmucci, Floriana, Andò, Edward, Viggiani, Gioacchino, Caicedo, Bernardo, Arson, Chloe
Format: Article
Language:English
Subjects:
Catenaries
Catenary
Cavities
Computed tomography
Deformation
Deformation effects
Drilling
Edge dislocations
Failure mechanisms
Free surfaces
Holes
Image acquisition
Parabolic bodies
Plane strain
Porosity
Shear
Shear bands
Shear planes
Soil
Soil density
Soil porosity
Soil stresses
Soils
Strain
Tomography
Volumetric strain
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Summary: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.
ISSN:0016-8505
1751-7656
DOI:10.1680/jgeot.21.00136