Velocity stepping experiments have been performed on a simulated calcite gouge using an annular shear apparatus to investigate the effect of dissolution on the frictional properties of a carbonate fault. The tested material was put in contact with hydrochloric acid at different concentration in order to provoke grains dissolution prior to the experiments. Particle size analysis shows that the small

At ten percent of sedimentary rocks, limestones are common geo-energy reservoirs. Being highly soluble, limestones are prone to fluid-assisted deformation and their mechanical behavior likely susceptible to fluid chemistry. In this study, we saturated limestone samples with 0.4 M MgSO4 or 0.4 M Na2SO4 CaCO3-saturated solutions (naturally present in many reservoirs) or a reference CaCO3-saturated solution

The heated fiber-optic method is receiving much attention as a quality control tool for buffer emplacement in the nuclear waste repository. By heating a fiber-optic cable installed in the buffer material, the thermal conductivity profile along the cable is obtained from which physical parameters such as the dry density at the time of the buffer emplacement and water content afterward can be inferred

This paper investigates proppant flow and transport in intersected fractures at angles typical for intersections of pre-existing and new hydraulic fractures. Proppant is small granular material, which is placed into hydraulic fractures during geothermal and hydrocarbon reservoir stimulation and props the fluid paths open during reservoir exploitation. This study uses plexiglas laboratory slot experiments

Raw (unfired) earth represents a sustainable and efficient alternative to traditional construction materials but its dissemination into building practice has been hindered by a relatively high vulnerability to water erosion. Enzyme induced carbonate precipitation (EICP) can improve the durability of earth materials without using traditional chemical binders such as cement and lime. EICP utilises the

Energy tunnels allow the harvesting of untapped heat at shallow depths in the underground to meet the thermal energy requirements of buildings and infrastructures over large areas. Such heat can derive from two sources: the ground surrounding energy tunnels and the air circulating in the environment internal to these tunnels. To date, various investigations have addressed the role of ground characteristics

This paper explores the potential use of a pipe pile as a heat exchanger. The comparison between the thermomechanical characteristics of the solid energy pile and pipe energy pile was analyzed by using the model test method. The potential effects of thermal cycles on the horizontal earth pressure and the pile resistance redistribution were analyzed and discussed. Moreover, this paper also presents

The generation and migration of gas is an unavoidable process that should be considered in the safety evaluation of nuclear waste geological repositories. The first aim of this study is to determine whether the gas will affect the swelling and sealing properties of the bentonite-based barrier. The results show that the gas/water can significantly affect the pore pressure of the material, which can

Coupled theory of poroelasticity is used to develop a generic analytical solution for the time-dependent solid stress and pore fluid pressure of the subsurface rocks. A uniaxial model comprising three layers of rock formations, namely, the reservoir, caprock and burden rock is considered. The model entails different mechanical and flow properties for the considered rock layers. A linear stress–displacement

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

Unsaturated soils exhibit water retention hysteresis, with different water retention behaviour during drying and wetting paths. Water retention hysteresis has often been modelled using expressions for the main drying and main wetting water retention curves that are unsatisfactory at low values of degree of saturation. In addition, the effect of retention hysteresis on the unsaturated hydraulic conductivity

Recent research effort carried out at Delft University of Technology to improve the experimental knowledge and develop a comprehensive modelling approach for fibrous organic soils is summarised. Experimental results and numerical analyses are combined to discuss some contradictory results which have delayed advanced characterisation of peats. Part of the apparent inconsistencies commonly found in the

Geothermal operation of energy piles involves an interplay between the multi-physical phenomena governing the behaviours of soils, geostructures and the interactions between them, which are mainly characterized by the associated temperature variations. This state-of-the-art paper brings together the experimental findings from several field and laboratory investigations to attain a thorough understanding

Energy geostructures (EGs) represent an innovative technology in the sustainable energy agenda and are useful for satisfying the energy needs of the built environment. They are usually involving geostructures such as piles, walls, tunnels, shafts, and sewers. The application of such technology to infrastructure projects may have considerable thermal potential because of the large surfaces that can

The main goal of this study was to capture the variations in pore-network, mechanical and hydrological characteristics of two different sandstone specimens subjected to CO2-enriched brine injection. The first sandstone specimen (S1) was from Allegheny National Forest, Northwestern Pennsylvania and the second one was a Triassic Pecos sandstone (S2) from Barstow (TX) quarry. Core-flooding experiments

Contemporary geotechnical design often requires the use of advanced numerical analysis, if it is to take account of the complex nature of many geotechnical problems. One crucial aspect of such analyses is the realistic representation of the facets of soil behaviour that are dominant in any given problem, which in turn requires a careful selection of an appropriate constitutive model and derivation

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

Acid injection, reactive instabilities and wormholing in carbonate reservoirs is investigated through the analysis of the linear acidizing problem theoretically and experimentally. Theoretically acidizing was analyzed by formulating the problem as a reactive moving boundary Stefan type problem. Wormholing is viewed as a reactive infiltration instability to the trivial solution of uniform dissolution

The study examines the effect of cement bond breakage in the mechanical behavior of porous weak sandstones in Kazakhstan’s oil fields using one-dimensional compression, triaxial shearing apparatuses, and Discrete Element Method (DEM) numerical simulation. Analogue sandstone materials were prepared by cementing a sand material with similar mineralogy to the real reservoir with the sodium silicate solution

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

Over the past two decades, a substantial amount of research has investigated the effects of thermal loads associated with the geothermal operation of energy piles on their mechanical response. Based on this research, consensus about the need for considering the effects of thermal loads on the geotechnical and structural design of energy piles has been achieved. However, the understanding of the influence

The Opalinus Clay shale formation is considered as a potential host geomaterial for the Swiss deep geological repository for radioactive waste. It presents different facies and it is characterised by a multi-scale heterogeneous composition, by a typical fissile structure with well-defined bedding planes and by anisotropic hydro-mechanical behaviour. This peculiar complexity makes it difficult to assign

Four failure criteria, a simplified Mohr–Coulomb, a Mohr–Coulomb, a von Mises and a Drucker–Prager model are considered for borehole failure and sand onset predictions. The von Mises is a special case of the Drucker–Prager. The resulting analytical expressions are suitable for implementation in the analytical software for sand onset and sand mass analyses. The models are calibrated and validated against

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

Using the double torsion method, we investigated the fracture mechanical properties of clay-rich Woodford and Mancos Shales, and carbonate-rich Marcellus Shale under conditions of varying fluid salinity, pH, and temperature. Both fracture toughness and subcritical fracture growth properties for clay-rich Woodford and Mancos Shales are sensitive to fluid salinity but not sensitive to pH. With increasing

Wellbore stability is a key challenge for oil and gas industry since it adds a great deal of additional cost to the industry. Traditional wellbore stability models such as elastic and poroelastic models may not produce reliable stress field around a wellbore since they consider isothermal wellbore condition. During the drilling phase, the drilling fluid temperature is different from the formation temperature

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 effect of numerous thermal cycles on the volumetric behaviour of saturated Bangkok sand was investigated using a double thermal oedometer test that incorporates a temperature control system. The tests were performed at various vertical stresses (2.007, 3.211 and 4.014 MPa) on a reconstituted sand having different initial densities and an undisturbed sand from a block sample collected from a depth

Predictive analysis of the spatial and temporal evolution of the subsidence induced by hydrocarbon exploitation could be affected by a high uncertainty also related to the a priori identification of the most realistic deformation parameter values. In fact, deformation behaviour of the involved formations is not constant but evolves according to the increasing strain caused by fluid pressure drop. Especially