Fracturing Pressure in Clay

Marchi, Michela; Gottardi, Guido; Soga, Kenichi

doi:10.1061/(asce)gt.1943-5606.0001019

Cited by 49 publications

(19 citation statements)

References 15 publications

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“…The peak grouting pressure was approximately four times as high as the vertical effective stress, similar to previous field grouting tests and practical engineering applications (Zhang et al 2013;Marchi et al 2014). …”

Section: Peak Grouting Pressuresupporting

confidence: 73%

Experimental study on grouting in underconsolidated soil to control excessive settlement

et al. 2016

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The underconsolidated soils in reclaimed land have low strength and high compressibility, resulting in susceptibility to excessive settlement and associated negative effects, which can be controlled by grouting. However, there is little research on the mechanism of grouting in underconsolidated soil, compared with the normally consolidated or overconsolidated soil. In this study, we present a series of laboratory grouting tests to investigate the grouting mechanism and the effect of degree of consolidation, soil type, load increment ratio and initial overlying load on the grouting performance. The results showed that the influence of grouting on primary consolidation settlement for underconsolidated soil included the heave effect, the additional settlement due to the dissipation of excess pore water pressure induced by grouting and the reduced settlement due to the increased modulus induced by grouting. However, grouting in underconsolidated soil had no influence on the secondary consolidation settlement. Grouting in underconsolidated soil with low degree of consolidation could obtain a shorter time of primary consolidation and a higher final grouting efficiency in primary consolidation stage. The final grouting efficiency in primary consolidation stage increased linearly with increasing load increment ratio, but decreased with increasing initial overlying load. As the overconsolidation ratio increased, the final grouting efficiency in primary consolidation stage decreased for underconsolidated soil, dropping to the lowest value for normally consolidated soil and then increased for the overconsolidated soil, reaching a limit. Moreover, the peak grouting pressure was proportional to the vertical effective stress at the beginning of grouting.

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Section: Peak Grouting Pressuresupporting

confidence: 73%

Experimental study on grouting in underconsolidated soil to control excessive settlement

et al. 2016

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“…The critical injection pressure at fracture opening affects the analysis of multiple engineering tasks such as drilling (Keulen, 2001), hydraulic conductivity measurements (Bjerrum et al, 1972), in situ remediation for lowpermeability soils (Alfaro & Wong, 2001), and grouting (Marchi et al, 2013). Most analytical solutions consider tensile strength and assume linear elastic fracture mechanics, in contrast to the cohesionless, granular nature of soft sediments.…”

Section: Gas Injection Pressurementioning

confidence: 99%

Grain‐Displacive Gas Migration in Fine‐Grained Sediments

Sun

Santamarina

2019

JGR Solid Earth

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Gas migration mechanisms control the release of gas from seafloor sediments. We study underlying phenomena using transparent sediments subjected to controlled effective stress; this experimental approach allows high‐resolution real‐time monitoring of gas migration through cohesionless granular materials under 3‐D boundary conditions. Observed migration patterns depend on the effective stress at the time of injection and the stress history. Gas migration transitions from pore invasive to grain displacive when the capillary pressure for air entry ΔPAE is greater than the effective stress σ′. This study focuses on grain‐displacive gas migration. The morphology of grain‐displacive gas bodies changes with depth as the sediment stiffness G increases and the effect of surface tension γ vanishes: spheroidal gas bubbles form in the near‐surface, faceted cavities further down, and eventually open‐mode fractures develop at depth. The gas injection pressure is proportional to the effective stress in grain‐displacive migration. Preloading and overconsolidation cause the rotation of principal stresses and gas‐driven openings align with the new minimum principal stress direction. Cyclic loading promotes the upward migration of gas‐filled openings, and there is mechanical memory of previous gas pathways in sediments.

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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%

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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Fracturing Pressure in Clay

Cited by 49 publications

References 15 publications

Experimental study on grouting in underconsolidated soil to control excessive settlement

Experimental study on grouting in underconsolidated soil to control excessive settlement

Grain‐Displacive Gas Migration in Fine‐Grained Sediments

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

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