Potential Repository Research Articles

Numerical assessment of the time-dependent behaviour of a tunnel with a yielding support system for a potential repository in claystone

For the disposal of heat-generating radioactive waste and spent fuel in claystone formations, support structures for underground excavations are essential for the operational safety of geological disposal facilities (GDF). Claystone formations of moderate strength, at considerable depths, are characterised by their squeezing, creeping, and, sometimes, swelling behaviour that results in continuous tunnel convergence over time. Under these conditions, a rigid support system can be subjected to very high loads, requiring a considerable thickness and/or high-performance concretes. Therefore, yielding support systems are being currently investigated as a promising alternative for GDF. This work presents a numerical study of the behaviour of a tunnel in a claystone formation with a yielding support system. The use of a compressible mortar between the rock and the lining is assumed, as a means of reducing loads and mitigating the effects of creep deformations. A key aspect of the analyses is that the host rock is characterised by a constitutive model that includes a number of features that are relevant for the satisfactory description of the hydro-mechanical behaviour of stiff clayey materials, such as mechanical anisotropy, creep, strain softening, and its ability to simulate localised deformations through a nonlocal regularisation. An elastoplastic constitutive model was also developed to represent the behaviour of the compressible mortar. Results provide relevant insights into the performance of the adopted yielding support system, particularly regarding the effect of time-dependent deformations and the additional relaxation of the rock on the fractured zone near the excavation.

Efficacy of invasive plant control depends on timing of herbicide application and invader soil seedbank density

Understanding the underlying temporal dynamics influencing invasive plant control outcomes is essential to achieve restoration and land management goals. Within grasslands, herbicides are commonly used as the main method for invasive plant control, but the efficacy of management may be dependent on seasonal dynamics, as well as the number of applications. Additionally, assessments to quantify invasive plant control are often limited to aboveground plant composition, overlooking the potential repository of propagules stored in the soil seedbank, and additional impacts on nontarget species. To ensure that an herbicide method is effectively controlling invader populations, while limiting impacts on the resident plant communities, both above‐ and belowground species responses must be assessed. We established an herbicide field experiment across different sites and years in Riverside, CA, U.S.A., to assess the control of a global annual invasive forb, Oncosiphon pilulifer. We investigated how seasonal herbicide management (early‐season vs. late‐season) and repeated annual herbicide applications (1 vs. 2 years) influenced cover and seedbank density of our focal invader and the resident plant community 1 year after treatment. We found that although late‐ and early‐season‐applied herbicides reduced invader cover, early‐season applications were the only strategy to reduce invader seedbank density, indicating potential longer term management control. Lastly, native cover was limited in post‐treated areas, suggesting that additional management strategies may be needed to overcome native establishment limitations in invaded grasslands.

Effects of synthetic site water on bentonite-concrete system for a potential nuclear waste repository

In high-level nuclear waste (HLW) repositories, concrete and compacted bentonite are designed to be employed as buffer materials, which may raise a problem of interactions between concrete and bentonite. These interactions would lead to mineralogy transformation and buffer performance decay of bentonite under the near field environment conditions in a repository. A small-scale experimental setup was established to simulate the concrete-bentonite-site water interaction system from a potential nuclear waste repository in China. Three types of mortars were prepared to correspond to the concrete at different degradation states. The results permit the determination of the following: (1) The macro-properties of Gaomiaozi (GMZ) bentonite (e.g. swelling pressure, permeability, the final dry density, and water content of reacted samples); (2) The composition evolution of fluids from the synthetic site water-concrete-bentonite interaction systems; (3) The sample characterization including Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). Under the infiltration of the synthesis Beishan site water (BSW), the swelling pressure of bentonite decreases slowly with time after reaching its second swelling peak. The flux decreases with time during the infiltrations, and it tends to be stable after more than 120 d. Due to the cation exchange reactions in the BSW-concrete-bentonite systems, the divalent cations (Ca and Mg) were consumed, and the monovalent cations (Na and K) were released. The dissolution of minerals in the bentonite such as albite causes Si increasing in the pore water. It was concluded that the hydro-mechanical property degradation of bentonite takes place when it comes into contact with concrete mortar, even under low-pH groundwater conditions. The soil dispersion, the uneven water content, and the uneven dry density in bentonite samples may partly contribute to the swelling decay of bentonite. Therefore, the direct contact with concrete has an obvious effect on the performance of bentonite.

Land, indigeneity and archaeological ruins in Ottoman Palestine: the people of Beit Jibrin and the Palestine Exploration Fund

ABSTRACT Palestinian nationalism and visions of Palestine as a nation have, since the loss in 1948 of 78% of Mandate Palestine to the newly founded State of Israel, focused on notions of rootedness and connection to the land. However, as a result of the disruptions to Palestinian culture stemming from the refugee lives of a large proportion of the population, and the loss or fragmentation of many personal and institutional archives, sources for the quotidian details of rural life and how the relationship between land and people played out in different parts of historic Palestine are often scarce. This article experiments with the use of accounts by Western archaeologists as potential repositories of such information. This derives, the author argues, not just from the descriptive features of such writings, which they share with other commonly used sources such as travelogues and the memoirs of missionaries and other temporary residents, but also from the nature of archaeology itself as an activity which intimately, if at times controversially and destructively, engages with land and soil, and in which local people were often hired to carry out excavation on their own lands. While fully acknowledging the many issues raised by the use of imperial documents to consider the lives of indigenous and subaltern peoples, I seek to employ techniques such as reading against the grain to investigate how such archives can contribute granularity and detail to our understandings of rural life in Palestine at the end of the Ottoman period.

A Usable Encryption Solution for File-Based Geospatial Data within a Database File System

Developing a security solution for spatial files within today’s enterprise Geographical Information System (GIS) that is also usable presents a multifaceted challenge. These files exist in “data silos” of different file server types, resulting in limited collaboration and increased vulnerability. While cloud-based data storage offers many benefits, the associated security concerns have limited its uptake in GIS, making it crucial to explore comparable alternative security solutions that can be deployed on-premise and are also usable. This paper introduces a reasonably usable security solution for spatial files within collaborative enterprise GIS. We explore a Database File System (DBFS) as a potential repository to consolidate and manage spatial files based on its enterprise document management capabilities and security features inherited from the underlying legacy DBMS. These files are protected using the Advanced Encryption Standard (AES) algorithm with practical encryption times of 8 MB per second. The final part focuses on an automated encryption solution with schemes for single- and multi-user files that is compatible with various GIS programs and protocol services. Usability testing is carried out to assess the solution’s usability and focuses on effectiveness, efficiency, and user satisfaction, with the results demonstrating its usability based on the minimal changes it makes to how users work in a collaborative enterprise GIS environment. The solution furnishes a viable means for consolidating and protecting spatial files with various formats at the storage layer within enterprise GIS.

Abstract 2436: In-depth analysis of microRNA signature in breast cancer derived extracellular vesicles: A potential biomarker repository for breast cancer diagnosis

Abstract Breast cancer remains one of the leading causes of cancer-related mortality among women worldwide. With the rising incidence of breast cancer, early and accurate diagnosis is pivotal in improving survival rates and patient outcomes. Our study addresses to identify vesicles associated with breast cancer in scope of miRNA signature. We focused on isolating breast cancer-derived extracellular vesicles (BEVs) from the bloodstream with immune affinity capture techniques. Then, we analyzed the miRNA profiles of BEVs in plasma samples from 120 breast cancer patients, 46 individuals with benign tumors, and 45 healthy controls. In this study, we analyzed to discover miRNA candidates for diagnosis of breast cancer with The Gene Expression Omnibus (GEO) database and found 379 down-regulated and 584 up-regulated differentially expressed miRNAs (DEMs) in tissue samples across 5 GEO datasets, and 28 down-regulated and 80 up-regulated DEMS in blood samples. Subsequently, we measured the expression levels of these 10 candidate miRNAs in BEVs from breast cancer cells and compared them with EVs from human mammary cells (MCF10a), using our BEV isolation method. The expression profiles of these miRNAs in BEVs were significantly elevated, supporting their potential as surrogate markers for breast cancer diagnosis. When comparing the AUC values of 10 candidate miRNAs through ROC analysis, 5 EV miRNAs (miR-21, miR-106b, miR-181a, miR-484, and miR-1260b) showed a high AUC values above 0.8. Subsequently, we verified a distinct signature of 5 EV miRNAs that effectively differentiate breast cancer patients from normal controls with 57.14% of sensitivity and 95% of specificity. Overall, our study not only complements existing diagnostic methods with high accuracy but also provides a deeper understanding of the molecular aspects of breast cancer, heralding a significant advancement in precision medicine and personalized cancer care. Citation Format: Jee Ye Kim, Min Woo Kim, Young Kim, Sol Moon, Suji Lee, Hyojung Lee, Joon Ye Kim, Seung Il Kim. In-depth analysis of microRNA signature in breast cancer derived extracellular vesicles: A potential biomarker repository for breast cancer diagnosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2436.

Plutonium mobility and reactivity in a heterogeneous clay rock barrier accented by synchrotron-based microscopic chemical imaging

The long-term safe disposal of radioactive waste corresponds to a challenging responsibility of present societies. Within deep geological waste disposal concepts, host rocks correspond to the ultimate safety barrier towards the environment. To assess the performance of such barriers over extended time scales, mechanistic information on the interaction between the radiotoxic, long-lived radionuclides like plutonium and the host rock is essential. Chemical imaging based on synchrotron microspectroscopic techniques was used to visualize undisturbed reactive transport patterns of Pu within pristine Opalinus Clay rock material. Pu+V is shown to be progressively reduced along its diffusion path to Pu+IV and Pu+III due to interaction with redox-active clay rock constituents. Experimental results and modeling emphasize the dominant role of electron-transfer reactions determining the mobility of Pu in reactive barrier systems. The effective migration velocity of Pu is controlled by the kinetic rates of the reduction to Pu+IV and Pu+III and the redox capacity of the involved electron donor pools. To advance our predictive capabilities further, an improved understanding of the nature and capacity of redox-active components of the reactive barrier material is fundamental. The findings represent an essential contribution to the evaluation of the long-term safety of potential nuclear waste repositories and have implications regarding the development of effective geological disposal strategies.

Novel wild edible mushroom Astraeus hygrometricus (Pers.) Morgan induces robust apoptosis on human acute lymphoblastic leukemia cells through a RONS-subsisted mitochondria-dependent pathway

ObjectiveTo explore the therapeutic effects of the novel wild edible mushroom Astraeus hygrometricus (Pers.) Morgan (A. hygrometricus) on human acute lymphoblastic leukemia cells. MethodsExtensive screening of the antiproliferative and chemopreventive potential of different extracts from 5 wild mushrooms, A. hygrometricus, Phallus sp., Lentinus sp., Tricholoma sp., and Serpula sp. was performed against a panel of 6 cancer cell lines and normal cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis determination, cell cycle profiling, intracellular reactive oxygen species (ROS) and reactive nitrogen species (RNS), and mitochondrial membrane potential were analyzed by flow cytometry. The activity of caspases was measured colorimetrically, and the expression pattern of mitochondrial proteins was analyzed. ResultsThe methanol extract of A. hygrometricus and MOLT-4 cells were identified as the most potent extract exhibiting antiproliferative activity and most sensitive cell line, respectively. The mushroom extract induced robust selective apoptosis in MOLT-4 cells and arrested cell cycle progression at the G0/G1 stage. The extract disrupted the mitochondrial membrane potential and enhanced ROS production in MOLT-4 cells. The methanol extract induced apoptosis by downregulating the expression of Bcl-2, increasing the expression of Bax, and activating the caspase cascade. ConclusionThe novel wild edible mushroom is a potential repository of biomolecules for the development of antileukemic drugs.

Using multiple isotopes to determine groundwater source, age, and renewal rate in the Beishan preselected area for geological disposal of high-level radioactive waste in China

Understanding hydrogeological conditions is crucial for selecting and assessing the long-term safety performance of a high-level radioactive waste (HLW) disposal repository. Utilizing environmental isotopes as effective markers for analysing groundwater movement, this study investigates groundwater recharge sources, age, and renewal rates using multiple isotopes in China's potential HLW repository site, the Beishan area. The results indicated deep bedrock groundwater primarily derives from ancient precipitation infiltration under cold climatic conditions. A noteworthy distinction is that loose sedimentary groundwater exhibits higher tritium content (>10 TU) compared to bedrock groundwater (<3.2 TU). Groundwater within the recharge area, especially within gullies and piedmont slope deposits, is relatively youthful, with an age of less than 30 years and an annual renewal rate exceeding 5 %. In contrast, the shallow groundwater age in the intermountain basins and depressions of the discharge area generally exceeds 50 years, with an annual renewal rate often falling below 0.5 %. At the Beishan underground research laboratory site, deep groundwater at the disposal repository depth displays a corrected 14C age exceeding 8,000 years, indicating an extremely slow movement and alteration rate. As a result, the hydrogeological conditions in the Beishan area are expected to be relatively beneficial for ensuring the safety of HLW repository.

Spatial Characterization of Shallow Structures in the Revell Batholith Integrating Seismic Imaging Techniques

The Revell Site, located in Northwestern Ontario within the Canadian Shield, is being assessed as a potential Deep Geological Repository (DGR) for Canada’s used nuclear fuel. Effective DGR establishment requires comprehensive subsurface assessment, particularly in evaluating structural stability, hydrogeological attributes, geological composition, and geochemical properties. Key among these considerations is understanding the three-dimensional characteristics of structural features to ensure the site’s suitability for long-term containment of radioactive materials. This case study focuses on imaging and characterizing structures within the predominantly intact biotite granodiorite-tonalite host rock at the Revell Site. Borehole data reveals these structures as mostly sub-horizontal mafic intrusions, with thicknesses of up to 3.5 m. They appear either as separate, discrete entities or in stacked configurations. Despite their limited thickness, most of these intrusions exhibit discernible attributes in surface seismic images due to their distinct physical properties. Some, however, exhibit velocity variations that decrease their overall reflectivity properties. An integrative approach employing surface seismic, Vertical Seismic Profiles (VSP), and borehole data facilitates the spatial identification of over 30 of these mafic structures. This comprehensive characterization not only lays the foundational framework for future discrete fracture network models but also provides important support for simulations related to fluid flow dynamics, groundwater behavior, contaminant dispersion, and heat transport mechanisms within the Revell Site. This study underscores the critical role of in-depth subsurface characterization in ensuring the secure, long-term management of radioactive materials in DGRs.

Porewater profiles of Cl and Br in boreholes penetrating the Mesozoic sequence in northern Switzerland

The analysis of tracer profiles of porewaters is a valuable tool to understand transport processes in argillaceous rocks and to unravel the paleo-hydrogeology of a site. In this contribution, anionic tracers (Cl, Br) from eight boreholes located in three study areas (∼20 km apart) penetrating the ∼800 m thick Mesozoic sequence in northern Switzerland, were analysed. A specific focus was on the Opalinus Clay, a ∼100 m thick homogeneous claystone formation, foreseen as host rock for radioactive waste disposal in Switzerland, as well as its mostly clay-rich confining units. Using porewater extraction methods, such as high-pressure squeezing, advective displacement and aqueous extraction, a unique dataset of spatially highly resolved Cl and Br profiles could be obtained. These show systematic and comparable patterns suggesting common paleo-hydrogeological evolution paths for all three study areas. The scatter in the tracer profiles based on the aqueous extraction data are mostly related to the uncertainty in the estimation of the anion-accessible porosity fraction on one hand and in the water content data in the case of low-porosity calcareous rocks on the other. Differences between the study areas are in line with differences in aquifer characteristics. The current shape of the anion profiles is dominated by diffusive exchange with the bounding aquifers over the last several ten thousands to millions of years, as supported by numerical modelling. The Br/Cl signals also suggest the preservation of older signals related to halite dissolution and highly evolved evaporitic porewaters occurring in evaporite-bearing units of the Triassic. Overall, the adopted methodology has enabled to obtain a unique dataset of anionic tracers at regional scale providing a solid basis for understanding the regional paleo-hydrogeology of siting areas for a potential nuclear waste repository.

Continuous Wavelet Transformation to Quantify small-scale Cycles of Petrophysical Properties; a New Approach Applied in a Potential Disposal Repository of Nuclear Waste, SW Hungary

Continuous Wavelet Transformation (CWT) was applied to study the small-scale repetitive oscillations of porosity distribution patterns in a 5 m silty-claystone core sample of the Boda Claystone Formation. We handled the fluctuations in voxel porosity averages over unequal depth distributions as signals over uneven time intervals. The strength of wavelet analysis lies in the ability to study the fluctuation of a signal in detail, i.e., the wavelet transforms permit automatic localization of the cyclic attributes' sequences both in time (the depth domain) and according to their frequency (the frequency domain). Thereupon, three main frequency branches (cycles) were discerned: small scale (5, 6.67, and 11 cm), intermediate scale (20, 30 cm), and large scale (66.67 cm). Depending on the CWT coefficients magnitude plot, we were able to detect the developments of porosity oscillation according to the depth variable. Thus, small-scale cycles were seen throughout the core sample., the intermediate-scale cycles were strong in the upper parts of the core sample and dwindled toward greater depths, and the large cycle was predominant in the lower part of the core sample. The cross-correlation of the wavelet coefficients of porosity and rock-forming components allows a detailed study of the inter-dependence of such parameters as their relationship changes over time. The distinct peaks at zero lag indicates that the measured wavelet coefficient series were contemporaneously correlated; their strong positive correlations suggest that both examined series respond similarly and simultaneously to other exogenous factors. The results emphasize that cyclical porosity fluctuations at all scales would concern three main factors; sediment deposition, diagenetic processes, and structural deformation (i.e., convolute laminations).

Origin of CO2 in Upper Devonian Duperow Formation and the Bakken Petroleum System at Kevin Dome, Northwest Montana

Carbon capture and storage (CCS) is a key mitigation strategy in achieving global net-zero emissions. It is therefore essential to identify and characterize potential subsurface storage repositories. Natural CO2 accumulations provide an opportunity to understand the behavior of CO2 in the subsurface. Here, we investigate the source(s), migration, and storage of CO2 in the Upper Devonian Duperow Formation at Kevin Dome, northwest Montana, USA within the Bakken Petroleum System. We report, major gas, stable and noble gas isotopic compositions in bulk gas samples (n = 19) produced from nearby hydrocarbon-bearing reservoirs at Kevin Dome and compare with CO2 bearing fluid inclusions (n = 24) from the Duperow Formation. Using the same methods, bulk gas samples (n = 9) from the adjacent Ferguson Field, (Exshaw/Bakken Petroleum System) in southern Alberta, Canada, and fluid inclusions from the Sweetgrass Hills igneous complex (n = 2) were analyzed to understand CO2 generation and the subsequent processes affecting CO2 regionally. We find that CO2 in the Upper Devonian Duperow Formation is magmatic in origin, likely related to the nearby Sweetgrass Hills igneous complex intrusion (∼52 Ma), whereas CH4 and N2 gases are generated predominantly by thermogenic processes associated with hydrocarbon generation during burial. Since emplacement, most CO2 in the hydrocarbon-bearing reservoirs of the Bakken petroleum system at Kevin Dome (∼98%) and the Ferguson Field (∼82%) has subsequently been dissolved into the groundwater. We employ a solubility model to calculate minimum gas/water ratios in Kevin Dome and the Ferguson Field, which are consistent with more groundwater interaction and more dissolution at Kevin Dome. Understanding the subsurface processes affecting CO2 is critical for future CO2 storage site selection.

Communicating scientific uncertainties

Abstract. Communicating a message of scientific uncertainty to a general audience is difficult because laypeople usually lack the conceptual tools to understand uncertainty (e.g., quantification methods). In addition, uncertainties can lead to mistrust and can be misused to prevent or delay radioactive waste management. On the proposed poster, we report the results of an experimental study (N=177) that investigated preferences for and trust in different visualizations of simulation results and tested different modes of communication (verbal, numerical, and visual/graphical). The participants processed three different parts, namely (1) the variation in the form of presentation of a scientific result, (2) the variation in the sender/source of a scientific result in numerical format, and (3) a direct comparison of two representations of simulation results (deterministic and probabilistic). Besides socio-demographics, we used items to check for the potential impact of numeracy and verbal skills, the need for a cognition concept, and questions on science in general, as well as the acceptance of a potential deep-ground repository. The dependent variable in each part was the degree of trust in the scientific validity of the information. For an example result, see Fig. 1. Clear influences of the non-dependent variables are only evident to a limited extent. Women rate their numerical abilities less highly than men do. There is no difference in verbal skills. The latter variable is also not explanatory, while numerical ability is relevant for the choice of the probabilistic variant and the corresponding trust rating in Experiment 3. The most striking result is that the attitude towards a deep geological repository for high-level nuclear waste (HLW; degree of acceptance) is the decisive parameter in all experimental conditions. The oral presentation will focus on another challenge of uncertainty communication, namely unquantifiable model uncertainties. In a repository, these may arise from the heterogeneity of the host rock. One of these potential uncertainties may be an undetected fault parallel in the drift axis in clayey host rocks. At the Konrad site, an anchor failure in an infrastructure drift resulted from such a fault. To deal with this kind of uncertainty, a certain kind of flexibility is needed to react to such events. The talk should initiate a discussion on the importance of communicating these potential uncertainties and on the impact of these uncertainties on the repository program.

Exploiting natural products to discover multitarget inhibitors of insect chitinolytic enzymes

Multitarget insecticides are more likely to achieve comprehensive regulation of insects with a low risk of resistance. Insect chitinolytic enzymes, including GH18 chitinases and GH20 β-N-acetyl-d-hexosaminidase, are attractive targets for multitarget insecticide design by virtue of their similar substrate binding mode and catalytic mechanism. On the other hand, natural products with diverse skeletal structures are potential repositories of chitinolytic enzyme inhibitors. This minireview first presents the theoretical basis of developing multitargeted inhibitors against insect chitinolytic enzymes and then focuses on the progress in developing multitarget inhibitors derived from natural products. These may provide ideas for the exploitation of novel pesticide leads from natural products by targeting multiple targets.

Genome characteristics of the optrA-positive Clostridium perfringens strain QHY-2 carrying a novel plasmid type.

Clostridium perfringens is a bacterial species of importance to both public and animal health. The gene optrA is the first gene that confers resistance to the tedizolid, a last-resort antimicrobial agent in human medicine. Herein, we whole-genome sequenced and analyzed one optrA-positive C. perfringens strain QHY-2 from Tibetan sheep in Qinghai province and identified one optrA plasmid pQHY-2. The plasmid shared similar structure with the optrA-positive plasmids p2C45 and p21-D-5b previously identified in C. perfringens, demonstrating the potential horizontal transmission of the optrA plasmids among C. perfringens strains. Annotation of the optrA-positive plasmids showed optrA and erm(A) located on a segment flanked by IS element IS1216E, and fexA, optrA, and erm(A) located on a segment flanked by IS element ISVlu1, which revealed the possible dissemination mechanism. Additionally, a Tn6218-like transposon carrying aac(6')-aph(2″) and erm(B) was also detected on pQHY-2, demonstrating the transposition of Tn6218 and spread of antibiotic resistance among Clostridium bacteria. Molecular analysis indicated the optrA-positive plasmids belonged to a plasmid type distinct from the pCW3-like plasmids, pCP13-like plasmids, or pIP404-like plasmids. Further structure analysis showed they might be formed by inserting segments into plasmid pCPCPI53k-r1_1, which coexist with two pCW3-like plasmids and one pCP13-like plasmid in C. perfringens strain CPI 53k-r1 isolated from a healthy human in Finland. IMPORTANCE Antimicrobial resistance is now a global concern posing threats to food safety and public health. The pCW3-like plasmids can encode several main toxin genes and three antibiotic resistance genes (ARGs), including tetA(P), tetB(P), and erm(B), which used to be considered as the main carrier of ARGs in Clostridium perfringens. In this study, we found the optrA plasmids, which belonged to a novel plasmid type, could also harbor many other ARGs, indicating this type of plasmid might be the potential repository of ARGs in C. perfringens. Additionally, this type of plasmid could coexist with the pCW3-like plasmids and pCP13-like plasmids that encoded toxin genes associated with gastrointestinal diseases, which showed the potential threat to public health.

Mechanical and hydraulic properties of carbonate rock: The critical role of porosity

Carbonate rocks are extensively used in civil infrastructure and play a critical role in geoenergy geoengineering, either as hydrocarbon reservoirs or potential repositories for CO 2 geological storage. Carbonate genesis and diagenetic overprint determine the properties of carbonate rocks. This study combines recent data gathered from Madison Limestone and an extensive dataset compiled from published sources to analyze the hydraulic and mechanical properties of limestone carbonate rocks. Physical models and data analyses recognize the inherently granular genesis of carbonate rocks and explain the strong dependency of physical properties on porosity. The asymptotically-correct power model in terms of (1- ϕ / ϕ ∗) α is a good approximation to global trends of unconfined stiffness E and unconfined compressive strength UCS , cohesive intercept in Mohr-Coulomb failure envelopes, and the brittle-to-ductile transition stress. This power model is the analytical solution for the mechanical properties of percolating granular structures. We adopted a limiting granular porosity ϕ ∗ = 0.5 for all models, which was consistent with the loosest packing of monosize spheres. The fitted power model has exponent ( α = 2) in agreement with percolation theory and highlights the sensitivity of mechanical properties to porosity. Data and models confirm a porosity-independent ratio between unconfined stiffness and strength, and the ratio follows a log-normal distribution with mean ( E/UCS ) ≈ 300. The high angle of internal shear strength measured for carbonate rocks reflects delayed contact failure with increased confinement, and it is not sensitive to porosity. Permeability spans more than six orders of magnitude. Grain size controls pore size and determines the reference permeability k ∗ at the limiting porosity ϕ ∗ = 0.5. For a given grain size from fine to coarse-grained dominant carbonates, permeability is very sensitive to changes in porosity, suggesting preferential changes in the internal pore network during compaction.

Using geophysical log data to predict the fracture density in a claystone host rock for storing high-level nuclear waste

Previously drilled boreholes of a host rock for a potential nuclear waste repository in Hungary revealed a highly fractured claystone rock body. A crucial step for characterizing the hydrodynamic behavior of such a fractured reservoir is fracture identification and accurate calculation of the fracture density. Although acoustic borehole televiewers provide a reliable base for determining the fracture density, older boreholes usually lack such data. However, conventional borehole geophysical measurements are often accessible in such cases. The aim of this study was to identify any correlations between well log data and fracture density. Multiple linear regression analysis was performed on data from two boreholes penetrating the Boda Claystone Formation in southwest Hungary. The upper section of the BAF-4 borehole was used for training, where the fracture density was estimated with a fit of R2 = 0.767. The computed regression function predicted the fracture density with high accuracy in both boreholes for all intervals with typical lithological features. However, in some sections where anomalous well log data indicated changes in the lithology, the prediction accuracy decreased. For example, the function underestimated the fracture density in sandy intervals.

Delineation of Paleochannel and Groundwater Resources in the Khari River Basin, Kachchh using Transient Electromagnetics

Abstract The paleochannels are riverine geomorphic features, which are either buried or shifted due to tectonic, climate, and anthropogenic activities. In general, these channels serve as potential groundwater repositories, and their identification can help in developing potable groundwater sources. Here, the results of transient electromagnetic (TEM) study carried out near and around the Khari river basin of the tectonically active Kachchh intraplate region, western India are presented. The TEM investigations at 22 sites along three traverses have been carried out in the river basin that cut the present-day river channel and its presumed paleochannel. The geoelectric sections of the three profiles decipher information down to 300-350m and suggest a multilayer aquifer system. The sub-surface model infers a deeper confined aquifer at variable depths from 100-150m associated with the river as well as its paleochannel. The paleochannel aquifer is observed to be buried under 15-20m thick unconsolidated sediments that overlie a Mesozoic sandstone layer of the Bhuj Formation. The resistivity sections across the paleochannel suggest a relatively fresh aquifer layer with higher storage capacity. A vertical bedrock offset of 100-120m and the discontinuity of lithostratigraphic layers observed from the study suggest the dominant tectonic control in the formation of the paleochannel that correlated with the location of the reactivated splay of the Katrol Hill Fault.

Tutorial: Systematic development of polynomial machine learning potentials for elemental and alloy systems

Machine learning potentials (MLPs) developed from extensive datasets constructed from density functional theory calculations have become increasingly appealing to many researchers. This paper presents a framework of polynomial-based MLPs, called polynomial MLPs. The systematic development of accurate and computationally efficient polynomial MLPs for many elemental and binary alloy systems and their predictive powers for various properties are also demonstrated. Consequently, many polynomial MLPs are available in a repository website [A. Seko, Polynomial Machine Learning Potential Repository at Kyoto University, https://sekocha.github.io]. The repository will help many scientists perform accurate and efficient large-scale atomistic simulations and crystal structure searches.