bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Sealing Integrity Mechanism of Salt Cavern Hydrogen Storage Under Alternating Load
Authors: He Aiguo , Ma Qingyuan , Liu Tianen , Li Jingcui , Zhang Hong , Dai Kun , Lu Yunhu
Published: September 2023

The sealing integrity of salt cavern hydrogen storage is an important technology and safety index of hydrogen storage. In the process of injection and production, the surrounding rock of hydrogen storage chamber is in the state of alternating load stress, and there is the risk of fatigue failure and leakage. Analysis of dynamic rock mechanics characteristics of surrounding rock of salt cavern hydrogen storage chamber under alternating load is the key to study the sealing integrity mechanism of salt cavern hydrogen storage chamber. Uniaxial tests, triaxial tests, cyclic loading and unloading tests and creep tests were carried out on rock samples from salt layer, interlayer and cap layer of hydrogen storage reservoir of Jintanmao 17 well by means of rock mechanics experimental machine RTR-1500. The deformation and failure characteristics, permeability, porosity, breakthrough pressure and other parameters of rock samples under alternating loads were discussed. Based on the results of the creep test, the Burgers creep model parameters for this block were fitted. The results show that: (1) in the triaxial cyclic loading and unloading experiment, the cyclic loading and unloading before the yield point decreases the porosity and permeability of the rock sample, while the cyclic loading and unloading after the yield point increases the porosity and permeability of the rock sample.(2) In the process of cyclic loading and unloading, the dissipative energy of cap rock is greater than that of interlayer, and with the increase of cycle times, the dissipative energy first decreases and then becomes stable.(3)Burgers creep model can well reflect the creep law of salt formation in the target block, and can be used to study the long-term stability of hydrogen storage cavity. The research results provide a scientific basis for the design and operation of salt cavern hydrogen storage.

INTRODUCTION

Salt rock has been used in the construction of hydrogen storage because of its low porosity, low permeability and damage recovery. Sealing integrity is very important for a salt cavern hydrogen storage tank. Only by maintaining the sealing integrity of the salt cavern hydrogen storage tank can the salt cavern hydrogen storage tank run stably.
Effect of Dilatancy in Weak Mechanical Discontinuities on Their Interaction with Fluid Driven Fractures
Authors: Smilovich D. , Celleri H. , Serebrinsky S. , Manzanal D.
Published: September 2023

Fluid driven fracturing plays a key role in several industrial applications, such as stimulation of O&G reservoirs, development of enhanced geothermal systems, and geological carbon storage, to name a few.

In previous works we have introduced Y-FRAC®, a fluid driven fracture and rock mechanics simulation platform which makes use of the Discontinuous Galerkin method and a cohesive zone model to describe the deformation and fracture processes that take place in the rock, and standard finite elements to model the corresponding fluid flow inside the fractures during stimulation.

In this work, we expand the previously used constitutive models in order to include the effects of dilatancy during shear deformation. We then evaluate the effect of dilatancy in some cases of practical interest, particularly for the hydraulic fracturing of unconventional reservoirs.

INTRODUCTION

The role of fluid driven fractures and their interaction with weak discontinuities in subsurface phenomena is of significant interest for many industrial applications, such as geothermal energy production, O&G reservoir stimulation and CO2 storage, among several others Kneafsey et al. (2018); Zimmermann and Reinicke (2010).

Shale formations are characterized by having an extremely low permeability, in the order of hundreds of nD.. For this reason, hydraulic stimulation is required in the O&G industry in order to generate conductive channels between the formation and the well, thus making extraction commercially viable. In the context of CO2 geological storage, they are considered as seals.

Weak mechanical discontinuities play an important role in the development of O&G fields in Argentina due to the highly variable presence of sub-vertical and sub-horizontal natural fractures Rodrigues et al. (2009); Ukar et al. (2017, 2019a,b). It is known that these weak interfaces can potentially act as preferential propagation paths, locally altering the fracture propagation direction Gale et al (2018), or even restricting its height Weng et al. (2018); Xu et al. (2019); Celleri and Sánchez (2021).
Effects of Hydrogen on Class H Well Cement's Properties Under Geological Storage Conditions
Authors: Maury Fernandez D. , Emadi H. , Thiyagarajan S. , Hussain A. , Ispas I.
Published: September 2023

Depleted oil and gas reservoirs are one of the most promising alternatives for underground hydrogen storage due to their sealant capacity and presence of residual hydrocarbon, which reduces the requirements for cushion gas and operational costs. Its existent infrastructure is also attractive owing to its lower investment costs. However, wells and facilities have been designed and constructed for operating with hydrocarbons and might be affected by the presence of hydrogen. Failure in well integrity could lead to hydrogen leakage, compromising the storage security for hydrogen projects. Hence, understanding hydrogen's effects on wellbore components such as casing and cement sheath becomes important. Although the effects of hydrogen on steel have been widely studied, effects of hydrogen on cement sheath and its properties are currently unknown. This study aims to evaluate the change in properties of neat Class H cement after being exposed to hydrogen under geological storage conditions (1500 psi and 120°F) for different time periods. Properties such as permeability, porosity and dynamic elastic properties like Young's Modulus and Poisson's ratio, were measured and analyzed before and after hydrogen exposure to investigate its effects on cement sheath. The experimental results revealed an increase in the permeability and porosity of the cement samples after hydrogen exposure. Also, hydrogen affects the dynamic elastic properties of the samples. The results of this study could be used to assess the wellbore integrity risks in depleted oil and gas reservoirs.

INTRODUCTION

Hydrogen is expected to play a fundamental role in the future global energy system. Its outstanding energy capacity (120 MJ/kg) (Abe et al., 2019) combined with its clean combustion, makes it one of the most promising alternatives as an energy carrier (Hosseini & Wahid, 2016). Although, hydrogenis the most abundant element on earth, it is not found freely in a sufficient amount, but it can be produced from non-renewable sources in multiple ways such as hydrocarbon reforming, hydrocarbon pyrolysis and subsurface production (in-situ combustion), or from renewable sources through water electrolysis. Once produced, hydrogen is burned and energy is conveyed as heat (Najjar, 2013; Salahshoor & Afzal, 2022; Veras et al., 2017).
A Data-Driven Intelligent Approach to Predict Shear Wave Velocity in Shale Formations
Authors: Mustafa Ayyaz , Tariq Zeeshan , Iqbal Arfa , Naeem Maryum
Published: September 2023

Shear (S-) waves velocity plays a critical role while deriving rock mechanical characteristics such as Poisson's ratio and Young's modulus. Mostly, the S-wave log is not available for all the wells due to associated high costs. Therefore, precise estimation of S-wave velocity is deemed necessary through prediction models. The study aims to develop reliable machine learning models for predicting S-wave velocity in shale formation using conveniently available wireline logs. Six robust machine learning techniques such as decision tree (DT), artificial neural networks (ANN), K-nearest neighbor (knn), random forest (RF), extreme gradient booster, adaptive gradient boosting were implemented for the model development. Training and testing results revealed high accuracy and robustness of all six proposed intelligent models in terms of high coefficient of determination (R2) and low root mean squared (RMSE) and average absolute percentage (AAPE) errors. However, comparison revealed that ANN model outperformed all other ML models exhibiting highest R2 (0.96) and lowest AAPE (0.91) and RMSE (2.96) errors for testing prediction results. The proposed intelligent models are capable of providing the swift, robust, and cost-efficient solution to obtain the S-wave velocity in shale formation that would be valuable in deriving the other rock mechanical properties.

INTRODUCTION

Shear wave velocity is of vital importance in estimating various geomechanical properties especially for petrophysical and geophysical investigations. Shear waves, in contrast to compressional waves, cannot travel through liquids. As a result, these data aid in identifying the characteristics of rock, such as the fluid content of its pores and its lithology. Also, understanding how pore spaces, lithology, pore fluid, and shear wave velocity relate to one another gives important reservoir information (Khatibi and Aghajanpour, 2020). One of the key objectives of geomechanical investigations is the development of the mechanical earth model, which can be accomplished using this parameter. The rock's mechanical characteristics and stress status are computed using the mechanical earth model (Plumb et al., 2000). Geomechanics, which takes into account the mechanical properties of rock, is crucial for planning activities like drilling, exploration, completions, and reservoir engineering. For safe and efficient drilling, in particular, it is crucial to comprehend the risks posed by ground stress, which necessitates the creation of geomechanical models.
Fluid-Solid Coupled Production Model of Fractured Horizontal Well in Glutenite Tight Oil Reservoirs
Authors: Yang Shuai , Yang Zhanwei , Chen Ang , Zhou Peiyao , Liu Kaixin , Wang Song
Published: September 2023

Clarifying the seepage mechanism and production decline law of fractured horizontal wells in glutenite reservoirs is crucial for guiding fracturing design, optimizing the production system, and realizing efficient reservoir development. In this paper, a production model suitable for fractured horizontal wells in glutenite tight oil reservoirs was established, based on the principle of fluid-solid coupling and comprehensive consideration of the characteristics of reservoir rock deformation and permeability stress sensitivity during production. An example application was used to verify the accuracy of the model, and the factors affecting production were discussed. The research results demonstrate that the model can reflect the dynamic change characteristics of the stress field and permeability during the production process. The production differential pressure must be controlled within the critical production differential pressure to avoid shear compaction in some formations near the wellbore, which could greatly reduce permeability and production. Among the fracturing engineering parameters, fracture spacing mainly affects the early linear seepage of the fractured horizontal well, whereas fracture half-length mainly affects the mid-late radial seepage. Increasing the fracture half-length has a more significant impact on increasing the long-term cumulative production of fractured horizontal wells in glutenite reservoirs.

INTRODUCTION

The Mahu Oilfield is situated in the Mahu Sag of the Junggar Basin, Xinjiang, with geological reserves of 1.24 billion tons and proven reserves of 520 million tons. It is currently the world's largest glutenite tight oil reservoir (Anon, 2018; He and Zhang, 2017). Thanks to the development of large-scale volumetric fracturing technology for horizontal wells, significant breakthroughs have been made in production in this area, making it the primary region for increasing reserves and production in the Xinjiang Oilfield (Li et al., 2020). However, glutenite tight reservoirs typically possess poor physical properties, strong heterogeneity, and weak matrix fluid supply capacity (Gao, 2022; Hao et al., 2021). Consequently, the pressure attenuation speed is often rapid after fracturing in certain blocks, resulting in insufficient continuous production capacity. Therefore, understanding the seepage mechanism and production decline law is critical for guiding fracturing design, optimizing the production system, and achieving efficient development of glutenite tight oil reservoirs.
Legitimacy of the Hertzian Assumptions for Poroelastic Spherical Indentation
Authors: Liu Ming , Huang Haiying
Published: September 2023

Key assumptions in establishing the classical Hertzian solution for contact between two linear elastic spherical bodies are that the contact is non-conforming and the contact radius is assumed to be much smaller than the radii of the two spheres. For the particular case when one rigid sphere is pressed against a linear elastic half space, the contact radius is only related to the radius of the sphere and the depth of penetration. Poroelastic contact has recently become a subject of interest for poroelasticity characterization of fluid-filled porous media. When a rigid sphere gets in contact with a poroelastic half space, the Hertzian assumption on the contact radius is still applicable at both the undrained and drained limits. However, an open question yet to be addressed is whether this assumption is legitimate for the transient phase. In this work, we address this fundamental question for two particular classes of poroelastic spherical indentation by first analyzing the problems theoretically assuming the Hertzian assumptions still hold and then conduct finite element simulations by modeling the indentation action through a frictionless contact algorithm based on the penalty method. The results indicate that though rigorously speaking, poroelasticity could result in deviation from the Hertzian assumption during the transient phase, for the particular cases involving step-displacement or step-force loading, the Hertzian assumption on the contact radius is legitimate if the objective is to determine the integrated force or displacement response of the indenter.

INTRODUCTION

Hertzian solution for frictionless contact between two linear elastic bodies (Hertz, 1881) is the theoretical basis for material characterization using spherical indentation to measure mechanical properties such as hardness, strength and toughness (Johnson, 1982, 1987; Lawn, 1993). Recent experiments with fluid filled porous materials such as polymeric gels and hydrated bones have demonstrated that spherical indentation could also be an effective technique for poroelasticity characterization (Hu et al., 2010; Kalcioglu et al., 2012; Oyen, 2008; Galli and Oyen, 2008; Lai and Hu, 2017, 2018; Islam and Oyen, 2021). In theory, if a rigid sphere is pressed into a linear poroelastic half space consisting of incompressible constituents, elastic constants can be determined from the undrained and drained limits according to the Hertzian contact solution. For the particular cases when the sphere is subjected to either step-displacement or step-force loading, hydraulic diffusivity or the coefficient of consolidation can be obtained from the transient response by matching the measured indentation force or displacement as a function of time against a master curve. Attempts have been made to establish this type of master curves numerically for step displacement loading (Hu et al., 2010; Lai and Hu, 2017) and semi-analytically for step force loading (Agbezuge and Deresiewicz, 1974; Oyen, 2008).
3D Image Analysis of Granular Force Chains
Authors: Li W. , Juanes R.
Published: September 2023

Granular media constitute the most abundant form of solid matter on Earth and beyond, from coffee beans to beach sand to Martian soil. When external forces are applied to granular media, the forces are transmitted in the media through a network of contacts–force chains. Understanding the temporal evolution and spatial structure of these force chains is a fundamental goal of granular mechanics. A new imaging technique, interference optical projectional tomography (IOPT), was introduced by Li and Juanes (2023) to visualize and quantify force chains in 3D granular media, and their evolution under triaxial shear. Here, we present a suite of 3D image analysis functions that were developed to study the morphology of the 3D granular force chains visualized by IOPT. Combined with the built-in functions in MATLAB, our image analysis toolkit allows us to quantitatively describe the morphology of 3D force chains in granular media under triaxial shear. Our study shows that increasing shear stress results in increasing force chain lengths and dip angle, and that the mechanistic origin of shear failure is the buckling of the force chains.

INTRODUCTION

Under the action of external stresses, grains in granular materials form an inhomogeneous contact network, which carries most of the external load by way of force chains. The resultant network pattern of these force chains can, in turn, help us determine the shearing and isotropic compression states in the granular media (Majmudar and Behringer, 2005). Similar filamentary patterns have been observed in other natural systems, such as dissolution wormholes (Daccord and Lenormand, 1987; Li et al., 2019b,c,a, 2022), fracture channels (Detwiler et al., 2003; Deng et al., 2016), viscous fingering (Måløy et al., 1985; Zhao et al., 2019), invasion percolation (Wilkinson and Willemsen, 1983; Zhao et al., 2016), hydraulic fractures (Lemaire et al., 1991), river networks (Rodriguez-Iturbe and Rinaldo, 2001; Abrams et al., 2009) and blood vessels (Szymczak and Cieplak, 2010; Zukowski et al., 2022). The temporal evolution and spatial structure of these patterns are helpful for our understanding of the underlying physics of the processes. Therefore, it is important to have the ability to analyze these network patterns quantitatively.
Replicating S-Shaped Composite Strength Response Using Bonded-Block Modelling: Capturing Dual Nature of Extensional Versus Shear Fracturing of Brittle Rock Mass
Authors: Farahmand Kiarash , Diederichs S. Mark
Published: September 2023

As mining operations pursue deeper and larger excavations, the accurate assessment of the risk of excessive rock deformations caused by brittle fracturing and dilation/bulking near excavation boundaries becomes increasingly important. To address this, the bonded-block modeling (BBM) approach such as UDEC-Voronoi has been widely used to simulate the complex brittle rock fracturing process and predict the shape of the excavation damage zone (EDZ) developed around underground openings. To realistically predict the EDZ shape, the BBM must be calibrated to accurately replicate the progressive failure of the brittle rock mass, characterized by a soften-hardening or composite S-shaped strength response. This can be achieved by specifying a number of input parameters based on fracture mechanics principles and a suitable calibration procedure. This approach allows for simulation of the in-situ brittle fracture processes. However, the available calibration methods are inadequate in capturing the dual nature of extensional versus shear fracturing of brittle rock masses due to their focus on laboratory sample fracturing behavior rather than large-scale rock response under in-situ stress paths. This paper provides practical recommendations for fine-tuning BBM input parameters from laboratory to field scales to reproduce observed failure mechanisms in-situ, advancing BBM as the state of practice for predicting overbreak formation in deep tunnels. The paper uses a hydroelectric tunnel in laminated sedimentary formations as a case study to calibrate the BBM model to the rock's S-shaped brittle strength. The calibrated micro-mechanical approach effectively captures the post-yield response of the rock mass, which is the key controlling mechanism in damage development around deep, lightly jointed grounds. The results demonstrate that for a realistic EDZ development and accurate capture of the mechanistic processes, BBM parameters must be calibrated to the long-term in-situ strength rock mass, rather than its short-term laboratory strength. The well-calibrated BBM model can be a practical and verified numerical tool for understanding and predicting damage formation around underground excavations.
Numerical Study of the Influences of Dynamic Loading and Unloading Rates on Fracturing
Authors: Cao Wen , Younis Rami M.
Published: September 2023

Dynamic loading offers the potential to induce densely connected fractured pore space over large bulk volumes of impermeable rock. An understanding of the impacts of the dynamic loading and unloading rates on the resulting fracturing can guide the design of discharge technologies. This work numerically investigates the dependence of the extent of fracturing on dynamic loading characteristics. We reconcile a high-fidelity model (finite-discrete element method with nonlinear fracture mechanics) with experimental observations. The model is subsequently used to simulate various loading scenarios spanning laboratory to field scale conditions.

INTRODUCTION

In contrast to hydraulic fracturing, high-energy dynamic loads generate radial fractures which are not influenced by formation stress anisotropy. This removes the need for determining the in-situ stress orientation, which is a necessary factor in designing horizontal wells that undergo multiple hydraulic fracturing treatments. This study aims to investigate the effect of different dynamic load functions on seismic fracturing.

One way to create high-energy dynamic loads is to use explosives (e.g., Grady et al. (Grady et al., 1980), Banadaki et al. (Banadaki, 2010), Zhang et al. (Zhang et al., 2017), and Jeong et al. (Jeong et al., 2020)). Explosives generate loading pulses with a maximum peak pressure that can exceed 1 GPa and a rise time of the pressure waveform on the order of 1 to 2 microseconds. Experiences using explosives are well-documented and span applications in various materials like granite, shale, and PMMA. The body of reported experiments shows that the extent of crack propagation depends on the energy released by the explosive charge, although a quantitative understanding of this relationship remains elusive for formations in the deep subsurface which cannot be observed directly or with great resolution. Another type of technology delivers the dynamic load using shock waves created in liquid. Hamelin et al. (Haimson and Fairhurst, 1967), Maurel et al. (Maurel et al., 2010), Chen et al. (Chen et al., 2012), and Xiao et al. (Xiao et al., 2018) for instance, applied Pulsed Arc Electrohydraulic Discharges (PAED) to produce shock waves in water. These loading profiles typically involve a longer time for the load to reach its peak. Moreover, in the case of laboratory experiments, reflections of shock waves from the finite samples may create extra fractures. To study the potential of formation fracturing at the field scale, large sample sizes, a wide variety of high energy loadings, and accurate diagnostics are needed. Given the challenge and costs of such extensive experimentation, numerical simulation can offer a useful alternative to narrow down the range of pulses to be investiated.
Thermal Effects Reducing Minimum in Situ Stress Can Happen Faster Than You Think
Authors: Azevedo C. T. , Schwalbert M. P. , Neumann L. F.
Published: September 2023

It is known that when fluids are injected into an offshore well, the temperature of the injected fluid is typically cooler than the in-situ reservoir temperature. A region of cooled rock forms around the well and this cooled region contracts, leading to a decrease in horizontal in situ stresses near the well. Such effect is always related with waterflooding or other secondary or tertiary recovery processes in long period of time, such as days or months of injection. This article will show field evidence that thermal effects can happen in a few minutes or in a couple of hours, in formations that combine high Young Modulus and high reduction in temperature during injection. This article will also present a few analyses using CFD simulation and an analytical simplified solution of the cooling effect of the reservoir during fluid injection. This will give sensibility of the orders of magnitude of the stress reduction in this condition and the fracture geometry that is being created.

INTRODUCTION

It is known that when fluids are injected into an offshore well, the temperature of the injected fluid is typically cooler than the in situ reservoir temperature. A region of cooled rock forms around the well and this cooled region contracts, leading to a decrease in horizontal in situ stresses near the well. Such effect is usually related with waterflooding or other secondary or tertiary recovery processes in long period of time, such as days or months of injection.

Settari and Walters (2007) note that a hydraulic fracture is induced in a well when the bottomhole injection pressure exceeds the fracture propagation pressure, which is a function of the smallest in situ principal stresses, usually a horizontal stress. In this sense, Perkins and Gonzalez (1984) attest that when cold fluid is injected into a warmer reservoir, there is a tendency for the rock around the well to contract, which leads to the emergence of a region affected by thermoelastic stresses, which can reduce horizontal stresses locally. The authors claim that in cases of water injection in reservoirs, even moderately buried, the thermal effect can reduce the original stresses by hundreds of psi. A consequence of the stress reduction is the reduction of the bottomhole pressure necessary to induce hydraulic fracturing of the formation, which in this case is considered a thermally induced fracturing. Charlez et al (1996) associate the increase of the II (injectivity index) of a water injection well with the occurrence of thermal fracture. The authors state that an indication of the occurrence of thermal fracturing is the sudden increase in the injectivity of the wells after some time of cold fluid injection, even when the bottomhole pressure do not exceed the estimated or measured original fracture propagation pressure for the region.
Effect of Choke Management on Fracture Closure and Well Performance in Shale Reservoirs with Natural Fractures
Authors: Liu Chuxi , Xie Hongbing , Mao Zhenyu , Yu Wei , Li Ning , Gong Yiwen , Leines Joseph , Miao Jijun , Sepehrnoori Kamy
Published: September 2023

Choke management and important aspect of an oil or gas well production life cycle. Effective understanding and modelling of choke management usually revolves around different paths of bottomhole drawdown. Limited numerical study of choke management within fractured reservoirs has been dedicated. In this paper, examinations of effects of choke management on a shale gas well performance is conducted, with the help of embedded discrete fracture model (EDFM). A realistic geological setting is also incorporated by simulation of a corner point structural model with complex 3D natural fractures and geometrically varying hydraulic fractures. This study also proposes a novel method to model conductivity distributions within hydraulic fractures to approximate proppant concentration distributions. Three choke management strategies are invested, each with distinct degrees of fracture closure. The results show that a 7.3% more cumulative production can be achieved for a mild choke strategy than an aggressive one. Although aggressive choke can produce more gas in the early period, it is exceeded by the conservative strategy after less than 1 year. The proposed model is accurate, robust, and consistent enough to help analyze other shale gas play at interest, and also to be extended to three phase shale oil reservoirs.

INTRODUCTION

While choke management numerical simulation is relatively less challenging in conventional oil/gas development, analysis under unconventional reservoir settings can be difficult. In unconventional horizontal wells, hydraulic fractures are man-made using proppants to open the fracture (Ellafi et al., 2020). As bottomhole pressure reduces to allow hydrocarbon flows, proppants are crushed or embedded into the rock matrix (Wijaya and Sheng, 2020). Different paths for bottomhole pressure (BHP) drawdown affects degrees of proppant crushing/embedding differently, thus yielding different production (Almasoodi et al., 2020). Depending on the operators’ project planning and objectives, BHP drawdown rates can range anywhere from 1 atm (conservative) to 6.5 atm (aggressive) per day (Wilson et al., 2016; Rojas and Lerza, 2018). A conservative strategy minimizes proppant conductivity loss throughout production period (Bagci and Stolyarov, 2019); while an aggressive one jeopardizes the proppant integrity leading to quick fracture closure (Tompkin et al., 2016).
Computational-Experimental Approach for Determining Material Parameters of Bentonite Clay in Engineered Barrier Systems for Nuclear Waste Repositories
Authors: Rahmani Mohammad , Azzam Abdullah , Grasley Julia , Kim Yong-Rak , Eun Jongwan , Kim Seunghee
Published: September 2023

Bentonite clay is a common material used in engineered barrier systems (EBS) to isolate the nuclear waste and protect the environment. However, its performance can be affected by changes in environmental conditions, such as high temperatures and water evaporation. The high temperature around the canisters causes the water in the bentonite to evaporate, leading to shrinkage and desiccation cracking, which in turn may compromise its sealing function and increase the risk of contaminating the surrounding soil. This study aims to determine the shrinkage and fracture properties of desiccating bentonite clay. To accurately understand and predict the desiccation behavior of the engineered buffering material, restrained ring tests were conducted and the shrinkage behavior was observed using a digital image correlation system. A finite element model was used to simulate shrinkage and desiccation cracking of bentonite clay. Through an inverse optimization process, the shrinkage coefficients and moisture-dependent cohesive zone fracture parameters of the bentonite were inversely identified. These fracture and geometrical stability parameters are essential for designing effective engineered barrier systems for the safe storage of nuclear waste. The presented experimental-computational method can determine material characteristics subjected to complex multi-physical conditions with damage.

INTRODUCTION

The potential risk associated with desiccation cracking exists in many engineering applications, such as designing engineered barrier systems (EBS) for geological repositories (Narani et al., 2020; Rayhani et al., 2007). When exposed to high temperatures, water evaporation within the buffer material [commonly bentonite clay] adjacent to the nuclear-spent fuel canisters leads to shrinkage of the bentonite body (Peron et al., 2009). Considering the confined configuration of EBS, the induced shrinkage process becomes mechanically restrained, leading to the development of tensile stresses and desiccation cracking (Nahlawi et al., 2004).

As the soil desiccates, its stiffness, tensile strength, and properties of its bonding with other materials can significantly change (Sanchez et al., 2013; Song & Cui, 2020; R. Tollenaar et al., 2017). Understanding the evolution of the buffer material properties throughout the lifetime of a geological repository is imperative, as these systems are designed to provide long-term confinement and isolation of nuclear-spent fuels.
The Use of Digital Image Correlation (DIC) to Investigate the Effect of Layering and Bedding Plane Orientations on Young's Modulus and Poisson's Ratio Measurements of Buckinghorse Shale Samples
Authors: Haile B. F. , Magsipoc E. , Grasselli G.
Published: September 2023

Anisotropy due to heterogeneities in rocks, such as shale, affects the mechanical properties of the rock depending on their orientation and arrangement. For instance, layering and pre-existing cracks can create potential weak planes. Hence, a measurement technique that can capture spatially detailed deformation, such as digital image correlation (DIC), is important for the investigation of the effect of rock heterogeneities. This technique enables a larger field of view than conventional strain gauges measurements. In this study, the effect of bedding planes on the macroscopic failure patterns of shale samples from the Buckinghorse Formation was investigated using unconfined compressive strength (UCS) tests. The DIC analysis showed areas of displacement discontinuity and localized strain caused by bedding plane orientation, and that layering has a significant effect on the Young's modulus computation based on the location of sampling and the length of measurement. With load perpendicular to the bedding, the Young's modulus showed significant variance even when measuring across large portions of the sample. As the virtual extensometer length increased, localized effects were smoothed, and the values approached the strain and Young's moduli from the LVDT instrumentation. While the variance of the calculated Poisson's ratio measured along different loading orientations appeared consistent, the stress-strain plots using horizontal virtual extensometers (lateral strain) presented more details on lateral differences with respect to location. Hence, it was shown that local variability in stiffness could potentially affect the mechanical characterization of rocks with strong heterogeneities. DIC analysis, which captures this variability, should be used to complement conventional laboratory instrumentation.

INTRODUCTION

Rocks have various heterogeneities that may affect their mechanical properties. Shale exhibits a transverse isotropic elastic response due to layering from sedimentation. The Buckinghorse shale formation, which is a dark gray shale formation found as part of the Lower Cretaceous shales in northeastern British Columbia (BC) (Chalmers and Bustin, 2008) was selected to be used in this study.
Pengaruh Online Customer Review ( OCR ) Dan Sistem Pembayaran Cash On Delivery Terhadap Minat Beli Mahasiswa Institut Agama Islam Tafaqquh Fiddin Dumai Di Elektronic Marketplace Indonesia
Authors: Deviana
Published: September 2023

Penelitian ini bertujuan untuk mengetahui pengaruh Online Customer Review dan sistem pembayaran COD (Cash On Delivery) terhadap minat beli produk secara online di e-marketplace Indonesia. Metode penelitian yang digunakan adalah metode penelitian kuantitatif dengan data primer yang diperoleh dari data kuisioner yang diukur menggunakan skala likert. Penelitian ini dilakukan kepada seluruh mahasiswa Institut Agama Islam Tafaqquh Fiddin Dumai dengan populasi sebesar 407 mahasiswa dan jumlah sampel yang didapatkan yaitu sebanyak 107 mahasiswa. Penelitian ini menggunakan teknik simple random sampling. Data dalam penelitian ini dikumpulkan dengan menggunakan kuisioner yang kemudian dianalisis menggunakan analisis regresi berganda dengan bantuan software SPSS 21.0. Hasil penelititan menemukan bahwa Online Customer Review dan Sistem Pembayaran Cash On Delivery secara bersama-sama berpengaruh signifikan dan positif terhadap minat beli mahasiswa IAITF Dumai. Dengan pengaruh sebesar 55,4% dan sisanya 44,6% dipengaruhi oleh faktor lainnya.
Differential Evolution Algorithm Based Very Fast Renewable Energy System Optimisation Tool Design
Authors: Altin Cemil
Published: September 2023

In this study, an optimisation tool that uses the differential evolution algorithm with a special distribution strategy is designed for the first time to be used in the optimisation of hybrid renewable energy systems. The developed tool and the hybrid optimisation model for multiple energy resources (HOMER) optimisation programme were compared. The tool is much faster than the HOMER programme and can produce almost the same results as HOMER. In addition, a heuristic-based optimisation technique was used for the first time to generate extremely comprehensive findings. The capacity shortage parameter, which is not used much in the literature, is used as a reliability parameter. The cost of energy (COE) was used as the cost function. The results are promising for detailed optimisation studies in this area.
Novel Lossless Positive-/Negative-Grounded Capacitance Multipliers Using VCII
Authors: Faseehuddin Mohammad , Shireen Sadia , Md Ali Sawal Hamid , Tangsrirat Worapong
Published: September 2023

In the presented research, the second-generation voltage conveyor (VCII) is used in the design of active capacitance multipliers. In this paper, three positive and one negative lossless grounded capacitance multipliers (GCMs) are designed. All of these GCMs are designed using two VCIIs, one capacitor, and two resistors. There is no need for any passive component matching to implement a GCM. The multiplication factor of GCMs can be set/varied by changing the values of two resistances as per requirement. Considering nonideal constraints, GCMs are analysed mathematically to evaluate the effect of nonideal current and voltage transfer gains on the performance of the proposed GCMs. Also, parasitic analysis is conducted to study the effect of VCII node impedance on the performance of the presented GCMs. The simulation analysis is performed using Cadence Virtuoso in 0.18 µm Silterra Malaysia process design kit (PDK). Additionally, the macro-model of commercially available integrated circuit, AD844, is used to design the proposed GCM-2 to further prove the theoretical findings.
Interaktion zwischen (Straf-) Justiz und Medien. Litigation-PR: Ziele, Herausforde- rungen und Gefahren
Authors: Fricke Ernst
Published: September 2023

Über Kooperations- und Austauschbeziehungen zwischen Medien und Gerichten ist in den Prozessordnungen nichts bekannt. Diese gehören damit zum informellen Verfahren der Entscheidungsbildung. Es ist schwer einzuschätzen, welche Nebenfragen das Handeln um und mit Informationen, die Zusicherung von Exklusivität, die gezielte Indiskretion und der spektakuläre Medienauftritt haben. Es geht auch die Öffentlichkeit an, wie die Verstrickung von Journalist:innen in die Prozessführung auf sein/ihr Rollenverständnis und seine/ihre Informationsaufgabe einwirken. Die informelle Verfahrensbeteiligung der Medien und die Beteiligung der „Organe der Rechtspflege“ bei

der Information und Unterhaltung der Öffentlichkeit sind nicht nur Themen für die Sozialwissenschaft, sondern auch für das prozessuale Verfahrensrecht sowie das Medienrecht.
The Concept of Developing Geoinformatics Skills in Teaching at Primary and Secondary Schools
Authors: Mísařová Darina , Svobodová Hana , Mašterová Vendula , Durna Radek , Hercik Jan , Šimáček Petr , Švedová Hana , Kubíček Petr
Published: September 2023

This conceptual monograph responds to insufficient support for developing geoinformation skills in Czech lower and upper secondary schools. It aims to create an interconnected system for developing geoinformation skills in teaching in lower and upper secondary schools, emphasizing the implementation of GIS tools and proposing principles for the development of geoinformation skills in teaching. For this purpose, a matrix of learning tasks is created, arranged according to individual geoinformation skills – reading, selection, use, creation, and sharing. The monograph is intended mainly for pre-service and in-service geography teachers at lower and upper secondary schools, the leaders of school educational programmes, and teachers in non-formal education. The monograph, including learning tasks and other materials, is available online at https://gitdoskol.ped.muni.cz.
Síntesis y caracterización estructural de nuevas poliamidas con unidades monometilénicas. Aplicaciones potenciales en el campo de la biomedicina
Authors:   , Franco García María Lourdes
Published: September 2023

Se han sintetizado nylons 1,n (n=5,6,7,8,10 y 12); nylons 2/n estadísticos con distintas proporciones de glicina (n=6, 11 y 12) y nylons m,n (m=6,12; n=6) con glicina incorporada secuencialmente y al azar. Los productos se han caracterizado por los métodos fisicoquímicos habituales y se han estudiado estructuralmente por difracción de rayos x, microscopia electrónica y refino mediante la metodología Lals. Se proponen estructuras cristalinas diferentes de las convencionales derivadas de las preferencias conformacionales del grupo metileno aislado entre grupos amida. La introducción de baja proporción de glicina en los nylons n y m,n con elevado numero de metilenos, da lugar a polímeros que pueden procesarse en forma de fibras con aceptables propiedades mecánicas y buenas posibilidades como materiales biomédicos.
Modelización avanzada de columnas de destilación de operación discontinua
Authors:   , Mehlhorn Arndt
Published: September 2023

La tesis doctoral se compone de dos partes fundamentales: El desarrollo teórico de un modelo de simulación para la destilación discontinua y la validación de este mediante experimentos hechos en una planta piloto de destilación discontinua.
La parte teórica se divide en la parte de desarrollo del modelo y en la parte de la implementación del modelo en un programa de simulación. El nuevo modelo desarrollado es un modelo de transferencia de materia que se distingue de los desarrollos anteriores por su capacidad de contemplar la cinética de la transferencia de materia tal como la hidrodinámica. La incorporación de efectos hidrodinámicos se basa principalmente en la observación de diferentes geometrías de contacto en una columna de platos perforados. Estas geometrías de contacto son canales de vapor y burbujas. En caso de las burbujas se distingue entre grandes y pequeñas con diferentes propiedades hidrodinámicas. De esta forma el modelo contempla tres diferentes clases de vapor, dos clases de vapor de desequilibrio y una de equilibrio (burbujas pequeñas). Para las clases de vapor de desequilibrio se calcula explícitamente los caudales de materia que traviesen la interfase basándose en la teoría de Maxwell-Stefan de transferencia de materia multicomponente.
La parte experimental se divide en la parte de diseño de la columna usada en una planta piloto y en la de la realización de los experimentos. El diseño de la columna tiene como objetivo la obtención de un medio de validación del nuevo modelo desarrollado. Por tanto está equipado con un gran número de sensores de temperatura, de presión y de tomas de muestra. También la realización de los experimentos se adapta al fin de la validación del modelo, ya que la frecuencia de toma de muestra y de capturación de señales de temperatura es elevada.
La memoria de la tesis contiene una comparación amplia de los resultados experimentales con los de la simulación. Estas comparaciones demuestran una determinada superioridad del modelo desarrollado sobre desarrollos anteriores.
Estudio de la relajación estructural de poliésters lineales mediante análisis térmico
Authors:   , Cortés Izquierdo María Pilar
Published: September 2023

Se ha estudiado mediante DSC:

 1) el efecto de la estructura química en la cinética de la relajación de entalpía en una serie de poliesteres lineales amorfos:

Poli (Isoftalato de Propileno), PPIP, Pol (Tereftalato de Propileno), PPTP, Pol (Tereftalato de Etileno), PETP Y Poli(Tereftalato de Dipropileno), PDPT. Se ha evaluado la velocidad de la relajación, así como los parámetros cinéticos: energía de activación, AH*, parámetro de no linealidad, X, Y parámetro de no-exponencialidad, B.

Se observa que un aumento de la velocidad de la relajación estructural conlleva una disminución de la energía de activación y un aumento de los parámetros de no-linealidad y no-exponencialidad. El grupo metilo produce un aumento de la velocidad de relajación y el grupo Dipropilen produce una disminución de dicha velocidad de relajación. Se ha relacionado también este comportamiento con la entropía configuracional y el parámetro de solubilidad medidos para los poliesteres.

2) La influencia de la cristalinidad en la relajación de entalpía para el PETP semicristalino con dos grados de cristalinidad: 12 y 32%. Se justifica la aparición de dos picos endotérmicos de relajación en base a la existencia de dos zonas amorfas dentro del polímetro, una zona amorfa interesferulitica y una zona amorfa intraesferulitica.
Simulación de estructuras y propiedades de poliamidas helicoidales
Authors:   , Zanuy Gomara David
Published: September 2023

Los objetivos que se persiguen la memoria presentada puede desglosarse en dos grandes bloques temáticos, los cuales están estrechamente relacionados.

1) El estudio conformacional y estructural de diferentes poliamidas helicoidales con potencial interés industrial. Concretamente se ha abordado el estudio de los siguientes polímeros:
- El ácido poli(-glutámico)
- El ácido poli(-glutámico)
- Complejos polipéptido - tensioactivo.
- El poli(-benzil--glutamato)
- Algunos poli(-alquil--glutamato)s
- Algunos poli(-alquil--L-aspartato)s

2) La predicción de la solubilidad de gases en polímeros cristalinos a partir del conocimiento de su estructura cristalina. Este último objetivo requiere el desarrollo de nuevas metodologías teóricas que permitan abordar el estudio de dicha solubilidad en fases altamente ordenadas

Para llevar a cabo el estudio de la microestructa de los polímeros expuestos se han utilizado un gran número de métodos de simulación computacional, en función del tipo de propiedad física que se quisiera caracterizar.

- Métodos Mecánocuánticos: Este tipo de metodologías ha sido utilizado para caracterizar las interacciones que determinan las preferencias conformacionales del ácido poli(-glutámico) y del ácido poli(-glutámico), así como, las interacciones que determinan la formación de los complejos polipéptido - tensioactivo.

- Métodos basados en la Mecánica Molecular: Dentro de los diferentes métodos basados en este formalismo se han utilizado las metodologías siguientes:

- Cálculo de la energía del empaquetamiento cristalino: Esta estrategia se ha utilizado para determinar las estructuras expuestas en la memoria.

- Dinámica Molecular: Esta metodología se ha usado para la caracterización conformacional del ácido poli(-glutámico) y de los complejos polipéptido - tensioactivo.

- Monte Carlo: Esta estrategia ha servido para estudiar las estructuras bifásicas características de algunos polímeros tipo peine, así como, como punto de partida para la predicción de la solubilidad de gases en polímeros cristalinos.

Los resultados obtenidos en la memoria presentada han permitido caracterizar completamente diferentes familias de polímeros de origen natural potencialmente biodegradables. Este punto es de especial interés puesto que permite seguir avanzado en la obtención de materiales compatibles con el medio ambiente y con un coste razonable.

A su vez, la posibilidad de poder predecir con un alto grado de precisión la solubilidad de gases en polímeros, nos permite presagiar el diseño de polímeros permeoselectivos, lo cual implica poder desarrollar materias primas para el desarrollo de productos industriales de altas prestaciones.