Analytical and experimental investigation of pore pressure induced strain softening around boreholes

Lv, Adelina; Ramandi, Hamed Lamei; Masoumi, Hossein; Saadatfar, Mohammad; Regenauer-Lieb, Klaus; Roshan, Hamid

doi:10.1016/j.ijrmms.2018.11.001

Cited by 23 publications

(7 citation statements)

References 39 publications

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“…For elastic zone, the actual radial displacement u e * is solved by substituting Equation ( 12) into left-hand side equation of Equation (6):…”

Section: Analytical Solutions Of Displacement and Stress In Elastic Zonementioning

confidence: 99%

“…Hence, elastic strains in softening zone are assumed to the same as corresponding strains at the plastic-elastic interface [6]. For plastic softening zone, the radial and circumferential strains are expressed by the following [12,18]:…”

Section: Analytical Solutions Of Displacement and Stress In Plastic S...mentioning

confidence: 99%

“…Determination of deformation and plastic zone of roadway is of significance for stability analysis and roadway support. Analytic solution for surrounding rock of roadway, which provides direct understanding of plastic zones and deformation, is a hot issue studied by scholars [2][3][4][5][6]. There are many factors to be considered in deriving analytic expressions for surrounding rock of roadway.…”

Section: Introductionmentioning

confidence: 99%

“…Hence, an accurate theoretical solution for surrounding rock should take the influence of groundwater into account. Besides, when circumferential stress of surrounding rock reaches its compressive strength during stress redistribution process, its stress would be reduced to its residual strength gradually; namely, surrounding rock of roadway would present post-peak strain-softening behavior [3][4][5][6]. Thus, elastoplastic analysis of surrounding rock should consider strainsoftening characteristics.…”

Section: Introductionmentioning

confidence: 99%

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A Unified Solution for Surrounding Rock of Roadway Considering Seepage, Dilatancy, Strain-Softening and Intermediate Principal Stress

et al. 2022

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The analytic solution for surrounding rock of roadway is of significance for stability analysis and roadway support. However, analytical solution for surrounding rock of roadway which took influences of water seepage, strain softening, dilatancy and intermediate principal stress all into account did not receive much reporting. To promote research in this aspect, a mechanical model simultaneously considering water seepage, strain softening, rock dilatancy, and intermediate principal stress was established based on porous elastoplastic mechanics, and then unified analytical solution for surrounding rock of roadway was obtained. Based on an example, influences of water seepage, strain softening, rock dilatancy, residual cohesion and intermediate principal stress on surrounding rock of roadway were thoroughly investigated using single factor analysis. The obtained results are as follows: radii of plastic zones and surface displacement of roadway would increase exponentially with water pressure increasing and their magnitudes are greater than corresponding values without water seepage considered; with softening modulus increasing, peak circumferential stress location would slightly shift to deeper surrounding rock, while broken zone radius and surface displacement of roadway would increase in a decay velocity; rock dilatancy has little effect on peak circumferential stress and plastic softening zone radius, while broken zone radius and surface displacement of roadway increase linearly with dilatancy coefficient α1 increasing indicating their magnitudes are overestimated if associated flow rule is adopted; with weighted coefficient increasing, stress components in plastic zones at the same distance from roadway center would increase, while radii of two plastic zones and surface displacement of roadway are reduced, i.e., self-bearing capacity of rock is enhanced considering intermediate principal stress effect compared to Mohr–Coulomb criterion; with residual cohesion increasing, peak circumferential stress remains unchanged, while stress components in plastic zones at the same distance from roadway center would increase and radii of two plastic zones decrease significantly. The above results implicated that water seepage effect should be carefully considered for roadway stability under groundwater environment; strain-softening and flow rule of rock should be reasonably analyzed and chosen to accurately predict surface displacement and broken zone radius of roadway; rock bolt length should be increased with softening modulus increasing, while it can be decreased with intermediate principal stress effect considered; grouting measure is an effective measure to improve roadway stability. In short, the research provides a theoretical basis and some practical engineering implication for roadway support.

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“…For elastic zone, the actual radial displacement u e * is solved by substituting Equation ( 12) into left-hand side equation of Equation (6):…”

Section: Analytical Solutions Of Displacement and Stress In Elastic Zonementioning

confidence: 99%

Section: Analytical Solutions Of Displacement and Stress In Plastic S...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Unified Solution for Surrounding Rock of Roadway Considering Seepage, Dilatancy, Strain-Softening and Intermediate Principal Stress

et al. 2022

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“…Scanning was performed at 120-kV voltage and ~100-μA current resulting in a resolution of 12.5-μm voxel size. Recent advances in μ-CT image processing have been utilized to investigate the petrophysical and rock mechanical properties (Guo et al, 2015;Lv et al, 2019;Pirzada et al, 2018;Roshan, Siddiqui, et al, 2018;Roshan, Masoumi, et al, 2018;Zhou et al, 2018). To perform a voxel-tovoxel comparison between the images obtained before and after the experiments, the images were registered using a 3-D image registration technique (Katsevich, 2002;Ketcham & Carlson, 2001;Sheppard et al, 2014).…”

Section: X-ray μ-Ct Imagingmentioning

confidence: 99%

A Multiscale Study on Shale Wettability: Spontaneous Imbibition Versus Contact Angle

Siddiqui

Xiao

Iglauer

et al. 2019

Water Resources Research

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Environmental and technical issues associated with hydraulic fracturing fluid leak-off and its low recovery in clay-rich shale reservoirs has challenged the energy sector. One of the main hypothesized mechanisms for the uptake of fracturing fluid is fluid imbibition due to capillary forces that are a strong function of the rock's wettability. However, shale wettability estimated by contact angle and spontaneous imbibition experiments are highly inconsistent throughout the literature. It is therefore critical to shed light on the possible reasons for such discrepancies and identify the superior technique. In order to characterize the physical processes from microscale to macroscale, the contact angles and spontaneous imbibition characteristics of shale samples were measured using aqueous ionic solutions (NaCl, KCl, CaCl 2 , and MgCl 2 ) at different concentrations (0, 0.1, and 0.5 M) and oil (Soltrol-130). The internal structure of the samples exposed to deionized water was imaged by three-dimensional X-ray micro-computed tomography before and after spontaneous imbibition at both unconfined and confined stress states. Additionally, the structure of all samples exposed to each ionic solution was analyzed via environmental scanning electron microscopy. Experimental observations were further substantiated by combining digital image correlation with Poisson-Boltzmann analysis to assess the hydration-induced strains. It was shown that while spontaneous imbibition is a more realistic measurement for liquids, results obtained under unconfined condition can be highly biased due to additional forces acting (e.g., osmotic or hydration forces) and also potential microstructural alterations. Thus, spontaneous imbibition measured under reservoir stress condition is strongly recommended for shale wettability estimation.

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The Effective Stress Coefficient of Coal: A Theoretical and Experimental Investigation

Lv¹,

Aghighi²,

Masoumi

et al. 2021

Rock Mech Rock Eng

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Analytical and experimental investigation of pore pressure induced strain softening around boreholes

Cited by 23 publications

References 39 publications

A Unified Solution for Surrounding Rock of Roadway Considering Seepage, Dilatancy, Strain-Softening and Intermediate Principal Stress

A Unified Solution for Surrounding Rock of Roadway Considering Seepage, Dilatancy, Strain-Softening and Intermediate Principal Stress

A Multiscale Study on Shale Wettability: Spontaneous Imbibition Versus Contact Angle

The Effective Stress Coefficient of Coal: A Theoretical and Experimental Investigation

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