The self-sealing behaviors of compacted Na- and Ca-bentonite–sand mixtures were investigated by conducting swelling–permeability tests with specimens containing three types of technological voids. The technological voids, including an upper gap, a surrounding gap, and a center hole of the specimens at 0.03–17.65% of the total cell volume, were sealed by the swelling of the specimen. The vertical and

This work aims to analyse the fracture behaviour of rocks with U-shaped notches subjected to mode I loading and to different temperature conditions. To this end, an energy-based approach is used called the Strain Energy Density (SED) criterion. This study attempts to extend a previous work of the authors where the SED criterion was successfully applied to U-notched components subjected to mode I loading

Triaxial testing of argillaceous rocks and shales is significantly more challenging than conventional rock mechanical testing. The challenges are mainly related to the very low permeability of these geomaterials, and their sensitivity to exposure of atmosphere and brines, which induces variations of water content, suction and effective stress. There are currently no international standards to guide

During the last few decades, a number of advanced experimental techniques have provided an unprecedented insight into the behaviour of geomaterials. A notable example are the so-called full-field techniques such as x-ray and neutron imaging, which allow the non destructive characterisation of the 4D (3D+time) response of geomaterials undergoing hydro-chemo-thermo-mechanical loading. While x-ray tomography

One-of-a-kind experimental and numerical investigation is provided in this paper about energy sheet pile walls: earth retaining structures that embed heat exchanger probes within piles for the exploitation of shallow geothermal energy. The study resorts to the results of full-scale in situ tests and coupled three-dimensional thermo-mechanical finite element analyses of an energy sheet pile wall constructed

In recent years, operational issues during the exploration of Pre-salt reservoirs have aroused the interest of the Brazilian oil and gas industry in studying karstification and its effect on carbonate reservoirs. Since then, a massive research effort was dedicated to the geology of the Brazilian onshore karstified carbonate formations; however, geomechanical modeling of reservoirs with karstic cavities

With the continuous demand for mineral resources, the construction design and stability of underground rock engineering have been a frontier research topic worldwide. Stability analysis of underground caverns, tunnels, boreholes, and cavities is of critical significance for underground engineering. To investigate the mechanical properties and failure mode of sandstone specimens with prefabricated cavities

This paper introduces a novel soil water retention curve model that considers two different mechanisms of water retention – namely capillarity and adsorption – and their evolution with soil fabric along a generalized stress path. The model is formulated based on a new developed framework, which is justified against experimental evidence and incorporates the following developments: (i) the characteristics

In this note we present a theoretical study on the conditions for the onset of cracks, as well as the corresponding pattern formation, in saturated viscoplastic soils under isotropic loading (extension). The type of stress applied is left unspecified, to cover a variety of loadings including shrinkage due to desiccation, isotropic thermal expansion, mechanical loading and so forth. By treating the

Geotechnical structures are being increasingly employed, in Europe as all around the world, to exchange heat with the ground and supply thermal energy for heating and cooling of buildings and de-icing of infrastructure. Most current practical applications are related to energy piles, but embedded retaining walls are now also being adopted. However, analysis and design methods for these new dual use

Field measurements are an essential part of nearly all construction projects. Field monitoring is the repeated measurement of a particular parameter over a period of time and is used to evaluate designs, assess the effectiveness of construction methods, control construction progress to avoid unwanted damage, provide warnings of unacceptable performance and prevent failures. Field monitoring is also

Internal erosion can be a cause of failure in hydraulic structures such as levees, dikes and embankment dams. Suffusion is a type of internal erosion in which the fine particles migrate through the voids between the coarse particles under seepage flow, leaving behind the coarse skeleton. In this study the impacts of suffusion on the mechanical properties of soil in triaxial compression and torsional

Soils are continuously subjected to thermal loads – and thus to temperature variations – as a consequence of natural or anthropogenic perturbations that involve the transfer of heat. For example, several engineering applications exist in which soils undergo temperature variations over time scales that can vary and last from seconds to centuries. As temperature variations can critically influence the

In deep underground mines, a successful development plan to exploit deeper mining levels is highly dependent on adequate consideration of the magnitude and orientation of situ stress state. However, significant uncertainties are associated with the estimation of these parameters. The in-situ stress values that are used in the evaluation of the stability of underground structures in each mine strongly

Chemical treatment is one of the popular methods dealing with geoenviromental problems related to soil, such as waste dredged materials, soil with heavy metal pollutions, among others. This paper performed a series of laboratory tests to investigate the effect of phosphogypsum on water content, density, pH, unconfined compressive strength and deformation modulus of cement stabilized soil. It is found

Saline solution has considerable influence on the thermo-hydro-mechanical behavior of compacted bentonite. In this study, the effects of NaCl solution on the swelling deformation, oedometric compression, and thermal volume behavior of compacted Gaomiaozi bentonite were investigated. Results show that compressibility of the specimens decreases with increasing NaCl concentration of the presaturation

This experimental study investigates the geomechanical stability of methane hydrate-bearing sediments (MHBS) during hydrate dissociation. Two MHBS specimens were prepared using sand and 5 wt% clay mixtures, and both with a targeted hydrate saturation of ∼40%. The two specimens were initially subjected to two different deviator stresses, i.e., one below the strength of host sediment (stable) and the

The first part of the paper deals with high-cycle loading and presents a parametric study with numerous drained cyclic tests with a large number of cycles (N≥104). The dependence of the strain accumulation rate on initial relative density, amplitude, average stress and cyclic preloading is addressed. These test series form the basis of the calibation of a high-cycle accumulation (HCA) model, which

Pore pressure has a major influence on the effective stress and thus on the mechanical behaviour of rocks. In this study, we focus on the hydro-mechanical behaviour of a low porosity andesitic rock heat-treated to 930 °C to induce thermal cracks and increase the permeability of the samples. First, we show that permeability decreases from 8 × 10−16 m2 to 1.5 × 10−17 m2 with a confining pressure (Pc)

Concurrent production and injection in stacked reservoirs as commonly conducted in unconventional resource exploitation potentially influences reactivation of nearby faults. Using three-dimensional, fully-coupled poroelastic finite-element simulations, we assessed the potential for reactivation of a barrier normal fault in a normal-faulting stress regime for twelve generic injection–production scenarios

Unconventional reservoirs refer to hydrocarbon reservoirs that require special stimulation treatments, such as hydraulic fracturing, to economically produce hydrocarbon. These reservoirs are tight with very low permeability, less than 0.1 milli Darcy (0.1 mD). Shale oil and shale gas reservoirs are prime examples of unconventional reservoirs. Effects of temperature on unconventional reservoirs’ dynamic

Based on long term investigations of the microstructure of various geomaterials as different as sensitive low plastic clays from Eastern Canada, unsaturated compacted silt from the Paris area, highly plastic compressible deep marine clay from the gulf of Guinea, compacted MX80 bentonite and the Callovo–Oxfordian claystone, considered as possible barriers in deep geological radioactive waste disposal

This position paper was developed by members of the task force on “Energy Geostructures” of the International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE) Technical Committee TC308 on ‘Energy Geotechnics’. The article includes a summary and review of some of the most recent analysis approaches, in situ testing, full scale testing and model scale experiments with a focus on energy

The history of reservoir stimulation to extract geothermal energy from low permeability rock (i.e. so-called petrothermal or engineered geothermal systems, EGS) highlights the difficulty of creating fluid pathways between boreholes, while keeping induced seismicity at an acceptable level. The worldwide research community sees great value in addressing many of the unresolved problems in down-scaled

This paper describes the implementation of the Bodner–Partom model for the analysis of copper corrosion barrier in canisters containing spent nuclear fuel. The Bonder–Partom constitutive model implemented in CODE_BRIGHT finite element code is compared with experimental results for validation and with the Stealth finite difference code for verification. Deep geological disposal is the most reliable

As energy operations face the challenge of reservoirs at ever-increasing depths, modelling the response of reservoir rocks at high pressure and high temperature (HPHT) conditions is a crucial step for successfully unlocking new resources. At these conditions, rocks can experience thermal and pressure sensitivity, as well as admit internal phase changes at the pore-solid interfaces that determine their

Fluid-induced seismicity has been observed and recorded for decades. Seismic energy necessarily requires a source, which is frequently related to rock fracture either in compression or tension. In both cases, such fracture may be promoted by crustal fluids. In this paper, we review some of the advances in the field of fluid-induced seismicity, with a particular focus on the use and application of new

Microseismicity is observed during an underground mining development in Saskatchewan, Canada. The events are located near the main working level at 480 m depth and show some temporal correlation with the daily rate of rock removal. We compute the focal mechanisms of six microseismic events using the P-wave first arrival polarities and the S/P amplitude ratios. The focal mechanisms of events classified

On advanced laboratory testing of geomaterials with emphasis on unconventional types of liquefaction tests, it is attempted to report some of the past and recent challenges in developing/improving laboratory stress–strain soil testing apparatuses and relevant control/measurement techniques. They include a) local measurements in triaxial tests on prismatic/cylindrical specimens and torsional shear/triaxial

Episodic earthquake activity associated with pore-fluid pressure diffusion in the crust can frequently be observed in intraplate regions, particularly related with past volcanism. Increased micro-seismicity has been observed during 2012–2014 in such an area, near the CO2-rich Florina basin (North Greece). Using a high-resolution relocated catalog for the area, we use concepts of statistical physics

Two types of hydraulic stimulation may be considered for the development of Enhanced Geothermal Systems (EGS), namely hydraulic fracturing and shear induced dilatancy. Only shear induced dilatancy has been found efficient for the shallow (750 m deep) granite test site at Le Mayet de Montagne. On this site, integration of focal mechanisms of induced seismic activity together with results from Hydraulic

In this paper the problem of redirection of a crack driven by viscous fluid under mixed mode loading is considered. The loading includes the classical Modes I - III and the hydraulically induced tangential traction on the fracture surfaces. The effect of the plastic deformation of the near tip zone is accounted for. Different criteria to determine the fracture deflection angle are examined and compared

The depressurization of natural hydrate deposits to produce methane gas can increase the effective stress in hydrate-bearing sediments, which may induce sand particle crushing. Sand crushing may become detrimental to gas production, because the breakage of sand particles can cause sediment contraction, reduction in permeability, and the generation of finer particles exacerbating solids migration and

Depressurization of hydrate-bearing sediments (HBS) is inevitably accompanied with sediment transport, not only structural host sediment itself but also fine particles, which can be a significant problem in producing gases from HBS, as demonstrated in recent field-scale hydrate production tests. Particularly, the migration of fine sediment particles can alter the hydro-mechanical properties of sediments

The geomechanical behaviour of hydrate-bearing sediments during methane gas production is complex due to the spatial and temporal changes in stress, pore pressure, temperature, and phase change. In order to evaluate the geomechanical risks during methane gas production, it is necessary to understand the thermo-hydro-mechanical (THM) responses in the production region that recovers methane gas from

Production of methane from hydrate-bearing sediments requires hydrate dissociation for releasing mobile methane gas in sediments prior to gas production operations. Fines may migrate through or clog the pore space of sandy sediments depending on the geometry and topology of the pore space. Multiphase flow experiments were conducted on brine saturated uniform silica sand mixed with different percentages

Methane hydrate is being considered as a potential future energy source but may at the same time constitute a considerable geo-hazard. In the present study, methane hydrate bearing sand sediment was created by pressurizing methane gas into previously moistened, then chilled, packed sand specimen (excess gas method). The excess gas was then replaced by water at high pressure. Afterward, a heating/cooling