Laboratory studies on fracturing of low-permeability soils

Alfaro, Marolo C.; Wong, R.C.K.

doi:10.1139/t00-096

Cited by 62 publications

(24 citation statements)

References 17 publications

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“…Moreover, the initial in situ horizontal stress is less than the vertical stress, as K 0 is less than unity, which is a favorable condition for the cavity to propagate in the vertical direction. Similar experimental results were reported by Alfaro and Wong (2001).…”

Section: Distribution Of Principal Stresses and Propagation Of Cavitysupporting

confidence: 91%

Pressure-controlled cavity expansion in clay

Au¹,

Yeung²,

Soga³

2006

Can. Geotech. J.

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Experimental studies and numerical simulation of experiments were conducted on pressure-controlled cavity expansion in clay. The modified Cam-clay model was used to describe the clay behaviour. The experimental data are in good agreement with the simulation results, indicating that the adopted numerical simulation procedure is a plausible and reliable technique to study the fundamental behaviour of pressure-controlled cavity expansion. A new parameter, cavity aspect ratio (CAR), was defined to better describe the cavity shape. Different phenomena during the cavity expansion process are thus studied numerically, and the results are presented in this paper.

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Section: Distribution Of Principal Stresses and Propagation Of Cavitysupporting

confidence: 91%

Pressure-controlled cavity expansion in clay

Au¹,

Yeung²,

Soga³

2006

Can. Geotech. J.

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“…In some cases, excess pore pressure can exceed the effective least principal stress plus the tensile strength of the medium allowing hydrofracturing to occur (Alfaro & Wong, ). When sediments are only submitted to the load of the overlying sedimentary cover, the greatest effective stress is vertical (σ′ v ), whereas the least effective stress is horizontal (σ′ h ; Sibson, ).…”

Section: Methodsmentioning

confidence: 99%

Evolution Model for the Absheron Mud Volcano: From In Situ Observations to Numerical Modeling

et al. 2019

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The morphology of mud volcanoes (MVs) has been extensively studied over the last few decades. Although recent research has begun to focus on deep processes and structures, little is known about mud generation mechanisms. This study aims to investigate the feeder system and formation of an active kilometer‐scale MV by relying on a 3‐D seismic survey and an in situ data set on the Absheron anticline (South Caspian Basin). Seismic data show a depleted area in the Anhydritic Surakhany Formation (ASF), whose mineralogical composition fits with surface mud. Well data show that the ASF is a succession of evaporitic beds and low‐temperature shales near its fracture pressure. Biostratigraphic analysis confirms a Pliocene origin for the mud, suggesting that the ASF may be the source. Numerical modeling of sedimentation coupled with laboratory test results and well sonic logs fairly reproduces the observed in situ overpressure trend. Two‐dimensional methane diffusion coupled with overpressure caused by rapid sedimentation highlights the superposition of critical fracturing conditions with methane‐saturated sediments at the base of the studied MV. The present study demonstrates the predominant role of fluid overpressure due to sedimentation and gas saturation in the formation of the Absheron MV, and this is shown to occur as follows: (1) methane migration through the thrust‐related faults reaching the ASF, accompanied by (2) lateral overpressure, caused by rapid sedimentation, diffusing along the ASF leading to (3) hydro‐fracturing of overpressured and methane‐saturated sediments resulting in an important decrease in overpressure, causing (4) gas exsolution and expansion triggering sediment remobilization.

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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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Laboratory studies on fracturing of low-permeability soils

Cited by 62 publications

References 17 publications

Pressure-controlled cavity expansion in clay

Pressure-controlled cavity expansion in clay

Evolution Model for the Absheron Mud Volcano: From In Situ Observations to Numerical Modeling

Grain‐Displacive Gas Migration in Fine‐Grained Sediments

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