bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monitoring Slope Movement Using Unmanned Aerial Vehicles
Authors: Tohm Calvin , Lingwall Bret , Uy Linus 
Published: August 2024

ABSTRACT:
Slope movement post precipitation events are a well-documented and understood phenomenon. The increase in moisture, if able to infiltrate the hill slope, can lead to the buildup of excess pore water pressure resulting in a decrease in shear strength of the soil. This phenomenon results in surficial failures that can slowly degrade the stability of a hill slope and eventually lead to failure. Monitoring this using traditional surveying techniques can prove to be time consuming and difficult due to the sheer number of points required to accurately capture the slope movement. To overcome this, this study sought to use unmanned aerial vehicle (UAV) techniques and equipment to monitor existing slope movement and failures. A study area in Rapid City, South Dakota around the South Dakota School of Mines and Technology (SDSMT) campus, which included multiple existing slope failures, was used. To monitor slope movement, photogrammetric imagery was taken of the study area both prior to and after precipitation event. Drone imagery was used to construct structure from motion (SFM) models to monitor slope movement by comparing previous flights to one another. All areas of interest or failures documented from the flights were individually ground truthed to ensure accuracy of the imagery. From this study it was found that seepage areas were a high indicator of slope failure of exposed ground surfaces and SFM models were able to accurately capture and document slope failures that had occurred after precipitation events.

1. INTRODUCTION
Seasonal weather cycles result in the development of anisotropic stresses within the surface layer of earthen structures, resulting in altered engineering properties and the development of an active layer of soil1. These weathering cycles include iterative shrink-swell with wetting and drying and freeze-thaw as well as times of acidic water, organic acids, and other chemical weathering processes. As the degree and severity of weathering cycles increases, this active layer propagates downward and results in near surface (upper 5-m) failures, weakening the overall integrity of geotechnical earth structures, resulting in increased erosion rates2-5, slope failure5, and compromised hydraulic conductivity in dams and levees2,7-9. These alterations in the engineering properties of earthen structures results in unforeseen or premature failure for slopes sensitive to changes in properties and conditions in the active zone (3 to 5-m), especially materials in the upper 1-m sensitive to seasonal freeze-thaw. Therefore, it is understood that seasonal weathering cycles are a key contributor to obscelense of earthworks.
Chemo-Mechanical Modeling of Anhydritic Claystones
Authors: Antonia Nousiou A. N. , Georgios Anagnostou G. A. 
Published: August 2024

ABSTRACT:
This paper presents a model for the swelling of anhydritic claystones – a severe problem in tunnelling. The model incorporates the effect of the chemical process of anhydrite to gypsum transformation via a strain decomposition in a mechanical (e.g., elastoplastic) part and a reaction-induced part. The latter depends on the mass change of anhydrite and considers that the volumetric chemical strain rate is the sum of the solid and pore volume change. The former is given by the chemical reaction's stoichiometry and the molar volumes of anhydrite and gypsum; while the latter may decrease or increase depending on whether new gypsum crystals precipitate within the available pore space or expand the matrix. Laboratory observations indicate that the higher the stresses and the porosity, the less the pore volume will increase during the chemical reaction. Moreover, the model assumes that the chemical strain rate is coaxial with the stress and that the strain in every principal direction depends on all three principal stresses. The predictions of the proposed model agree well with the results of test on artificial anhydrite-kaolin specimens and a high degree of correlation is achieved (R2 = 0.92).

1. INTRODUCTION
The swelling of anhydritic claystones is attributed to the water uptake by the clay minerals and the chemical process of anhydrite (CaSO4) to gypsum (CaSO4·2H2O) transformation ("AGT"). This phenomenon has caused extensive damages to a number of tunnels (e.g., tunnel floor heave, damage of the invert arch; cf., Amstad and Kovári, 2001; Anagnostou, 2007) and hence it has attracted great attention from the scientific community (e.g., Anagnostou et al., 2010; Ramon, 2014; Serafeimidis, 2014; Butscher et al., 2016; Wanninger, 2019). Nevertheless, a swelling law, capable of capturing these processes, is still missing (Anagnostou et al., 2010; Butscher et al., 2016), thus introducing uncertainties in tunnel design.
Early swelling models for tunneling (e.g., Einstein et al., 1972; Wittke and Rissler, 1976; Fröhlich, 1986) were based on Grob's (1972) "semi-logarithmic swelling law" and described swelling as a purely mechanical process; the developed strains are associated only with the stress changes. However, swelling rocks might also deform under constant stress or experience a stress increase without deformation, phenomena beyond the scope of purely mechanical models.
Kinematic Analysis of Geomechanical Displacement Fields to Assess Lifetime Integrity of Wellbores
Authors: Sathuvalli Udaya B. , Suryanarayana P. V. , Lewis David B. 
Published: August 2024

ABSTRACT:
Displacements in geomechanically perturbed formations induce additional stresses on wellbore tubulars. An appropriate well design basis should consider the mechanical response of the tubulars and the associated architectural implications. Traditionally, assessments of well integrity to geomechanical loading states have been conducted with large scale numerical models of reservoir, rock and the wellbore. In this context, we present a method to assess well integrity from a kinematic analysis of the geomechanical displacement field. The crux of the analysis is to regard the displacement field from the viewpoint of an observer on the wellbore centerline. Since the mechanical stiffness of a moving formation greatly exceeds that of a wellbore, the well practically follows the rock, and its shape accords with the equilibrium positions of the surrounding rock. The kinematic analysis identifies the dominant loading mode(s) on all the casings. We then apply specifically developed mechanical limit states to assess the mechanical response of the casings and cement sheaths (when applicable) to the geomechanical displacements. These limit states are used to determine well integrity, times to failure, and architectural options to prolong or optimize well life in an evolving set of geomechanical perturbations.

1. INTRODUCTION
Geomechanically induced displacements can severely test the integrity of wells. Regardless of the cause, an arbitrary point in the formation moves to a new location as a function of geomechanical displacements. Reservoir compaction, salt creep, tectonic stresses and fault movements are some of the most common sources of geomechanical loads on wellbores. Traditionally, assessments of well integrity to complex geomechanical loading states have been conducted with large scale integrated numerical models of reservoir, rock and the wellbore (Chia and Bradley, 1989; Bruno and Bovberg, 1992; Fredrich et al. (2001); Ibekwe et al. (2003); Li et al. (2003); Abou-Sayed et al. (2004)). Though these models are technically detailed and accurate, they are time consuming and inflexible, especially when parametric sensitivities are needed. During early stages of field development, when bottom hole locations, surface coordinates, trajectories, casing points and well architectures have not yet been finalized, the impact of geomechanical stresses on well integrity and well lifetimes can determine the success or failure of the project. In this light, our paper presents a method to analyze well integrity by examining the kinematic parameters of the geomechanical displacement field. Since the mechanical stiffness of the formation greatly exceeds the stiffness of the wellbore1, the geomechanical displacements are almost entirely transferred to the wellbore. The displacement deforms the wellbore centerline from its initial shape (defined by the drilling trajectory) into a three-dimensional curve characterized by its kinematic parameters.
Development of a Methodology for Predicting the Strength of Intact Bentonitic Shale and Gypsiferous Siltstone Using Fragments and Micro-Indentation Modulus Testing
Authors: Tohm Calvin , Lingwall Bret , Mitra Rudrajit 
Published: August 2024

ABSTRACT:
In many geologic and geotechnical investigations, obtaining sufficient intact rock core samples for uniaxial compression or point load testing can be difficult in weak sedimentary rock that spans into the realm of an Intermediate Geo-Material (IGM). These IGM materials have sufficient strength for infrastructure construction, but are difficult to core, sample, and test with sufficient volume to meet conventional ASTM or other test standards. Samples that are obtained, have often been fractured in the rock coring process. Thus, it is needful to develop alternative laboratory test methods to characterize the strength of these IGM soil/rock formations for engineering design. In the case of IGM bentonitic shales and gypsiferous siltstone materials of the Cretaceous Pierre Shale and Jurassic Spearfish formations of Western South Dakota, micro-indentation equipment was herein proposed as an alternative to uniaxial compression or point load testing. Fractured specimens of these materials were immobilized in polymer resin and tested using a micro-indentation apparatus to obtain the micro-indentation modulus. Complimentary intact and remolded specimens were tested in uniaxial compression to obtain parallel data. Coupling of the data from testing of fractured material and intact material and regression analyses show that a strong correlation exists between micro-indentation modulus and intact or remolded IGM strength. The method proposed in this paper is portable and extractable to other formations and validates the work of others around the world who have proposed this alternative approach for characterizing the strength of rock masses that are difficult to sample and test using conventional methods.

1. INTRODUCTION
Nearly 80% of the near surface geology west of the Missouri River and east of the Rocky Mountains in the Dakotas, Montana, Wyoming, Colorado, Nebraska and into Canada is composed of weathered residual soil, weathered rock, or weak sedimentary rock that spans from mechanically behaving as soil, Intermediate Geomaterial (IGM) and weak rock. IGM may be defined as cohesive or cohesionless geomaterial with unconfined strength ranging from 0.5 to 5-10 MPa or penetration blowcounts at 60% energy for a standard split-spoon sampler of 50-1501. The transition between soil and IGM may be noted by increased compressive strength at the 0.5 MPa threshold, while the transition between IGM and weak rock may be governed by an uncertain strength range of 5 to 10 MPa but also by a Rock Quality Designation (RQD) of 20 or less2. Highly fractured weak sedimentary rock with RQD &lt; 20 may behave similar to IGM3 in foundation engineering.
Stress and Load Path Dependent Static and Dynamic Moduli and Ultrasonic Velocities in Granite
Authors: Knippel E. P. , Wu C. , Xiong Q. , Villaquiran Vargas A. P. , Hampton J. C. 
Published: August 2024

ABSTRACT:
We performed a study of ultrasonic velocity as a function of stress and stress path using axial and radial ultrasonic P and S-waves. Young's modulus and Poisson's ratio are calculated using these velocities along axial and radial directions. Static elastic moduli are also measured along the same stress and stress path protocol. Effects of pre-existing microcracks in the sample are hypothesized via directional observations of velocity changes as a function of differential stress and mean stress. Dynamic Young's modulus is observed to increase primarily as a function of mean stress, whereas static Young's modulus is mainly dependent on differential stress. Since the dynamic moduli are reliant on the accuracy of manually picked arrival times, a comparison is made between the manual picks and automated picked arrival times using AIC, STA/LTA, and CUSUM methods. The agreement between manual and automated picks is highest for P-wave arrivals found through AIC, and more varied for S-wave arrivals overall.

1 INTRODUCTION
Experimental damage mechanics provides an excellent lens for which to view the evolution of rock physical property behavior. The ability to set user-defined testing environments creates a wide variety of stress states rock samples can be subjected to. Ultrasonic velocities and strain recorded in situ can be used to measure the dynamic and static elastic properties of a material under stress (Knippel et al. (2023b)). The state of stress and stress path contribute to the magnitude and behavior of these elastic properties (Tutuncu et al. (1998a); Tutuncu et al. (1998b)). The co-evolution of stress-strain relationships and ultrasonic velocities is well-known to be influenced by the presence and accumulation of microcracks within a sample (Zoback and Byerlee (1975)). The presence of microcracks changes the intrinsic material properties that govern elasticity and compliance at the continuum scale. Cracks experiencing a positive volumetric change under stress increase pore space within the rock, decreasing acoustic wave speed which is used to calculate dynamic elastic moduli. Permeability can also be affected by the presence of microcracks, as tensile microcracks with positive volumetric change could coalesce and provide additional pathways for fluid movement (Hampton et al. (2019); Kluge et al. (2021)).
Measuring Brittle Damage Thresholds of Crystalline Rocks by Acoustic Emissions on Compressive and Tensile Laboratory Tests
Authors: Malicki E. A. , Packulak T. R. M. , Gagnon É. , Diederichs M. S. , Day J. J. 
Published: August 2024

ABSTRACT:
The use of acoustic emission (AE) monitoring in brittle rock laboratory testing is one of the most accurate methods for measuring damage evolution and failure. In this study, AE data was collected from two separate laboratory testing programs. The first program consists of a series of unconfined compressive strength (UCS) tests completed on moderately foliated meta-sedimentary rocks from the Bathurst Mining Camp in New Brunswick, Canada, and high metamorphic grade tonalite gneiss from the Pointe du Bois pluton in Manitoba, Canada. The second program consists of a series of Brazilian tensile strength (BTS) tests completed on polymineralic homogenous and isotropic granites and amphibolite from the Pointe du Bois pluton. Using data collected by a Physical Acoustics Pocket AE system, individual waveforms are analyzed to distinguish tensile fracturing from shear fracturing events. Distinct trends and timing in the occurrences of tensile and shear fractures are observed leading to further insight into the behaviours of the materials throughout the loading process. This study provides enhanced guidelines for the collection of AE data and choice of instrumentation, filtration of measured events, and interpretation of filtered data to develop a greater understanding of the micromechanics occurring within these materials in both UCS and BTS tests.

1. INTRODUCTION
Acoustic emissions (AE) are one of the most accurate measurement tools that can be used to study damage development in rock and concrete materials. Acoustic emissions are elastic vibrations emitted when microcracks form within a brittle material. For structural and tunnel stability, acoustic emissions can be used to assess strength and monitor the development of damage including microcrack formation, growth, and spalling. There are numerous studies examining acoustic emissions and microfracturing for homogenous unconfined compressive strength (UCS) tests such as Scholz (1968), Ohnaka & Mogi (1982), Lockner (1993), and Diederichs et al. (2004). There are few recent studies regarding AE in Brazilian tensile strength (BTS) tests, which presently include Keshavarz et al. (2008), Liu et al. (2015), Wang et al. (2019), and Khadivi et al. (2023). In much of this literature, acoustic emissions are used to quantify damage development. However, as examined in Diederichs et al. (2004), Ohtsu (2008), Shiotani (2008), and Ohno & Ohtsu (2010), AE can also be used to determine the type of damage occurring and how it impacts material strength.
In this study, two (2) testing programs were completed; the first being a series of UCS tests on moderate to high grade metamorphic rocks and one crystalline rock, and the second being a series of BTS tests on low grade metamorphic rocks. Sample details are provided in Section 2, along with testing equipment specifications.
Challenges and Uniqueness of a Dual-Injection Fracture Model
Authors: Kresse O. , Hobbs B. , Pei Y. 
Published: August 2024

ABSTRACT:
Approximately 23% of US land operators have tried simultaneous pumping operations and reported on average more than 30% gain in efficiency. However, surface efficiency without comparable well performance is not useful—all simultaneous fracturing jobs demand compromise in completion strategy or pumping schedule. The simultaneous fracturing model has been developed as an enhancement to the existing complex fracture model describing propagation of a hydraulic fracture in conventional and unconventional formations with the capability to simulate simultaneous pumping operations. The simultaneous or timely delayed pumping could be from the same pad or even offset pads—there is no limitation. This will include proper modeling of fracture initiation, propagation, and interaction between fractures from different wells through stress shadow effects and crossing rules. The simultaneous fracturing model will allow engineers the ability to design, evaluate, and optimize the efficiency of simultaneous fracturing. The enhanced model also allows evaluation of different pumping schedules, well placement schemes, and scenarios to improve cluster efficiency. It will help to achieve the next level of surface efficiency through predictive modeling of simultaneous fracturing from different wells on the same or different pads. The new approach is bringing new challenges to the model to account for the different previously unaccounted for field related scenarios and situations, as well as will open new modeling related issues and problems. This will be the main topic of the paper.

1. INTRODUCTION
As an alternative to the widely used zipper-fracturing technique, the new completion technique of simultaneous fracturing (simul-frac) became more popular among US-shale producers (Jacobs, 2021). In simul-frac operations, one pumping crew can stimulate two horizontal wells at the same time and reduce completion times by more than half compared to the zipper-fracturing approach (Fig. 1). Some examples of successful simul-frac stimulations can be found in the papers by the Matador Completions Team (2023) and Chevron (Kim et al. 2021).
The typical simul-frac operation requires at least 25% more horsepower than the average zipper-frac spread. Simul-fracs require splitting the pumping rates between two wells, and while more pressure pumping units, i.e., an additional four stimulation pumps are required to be on location, they function at lower rates and spend less time on each pad - enhancing pumping efficiency and maximizing resource usage by significantly trimming pad completion time.
The interaction between fractures during simultaneous fracturing is, in a way, similar to the parent-child interaction, with the difference that the interaction is in real-time mode, when both jobs are still active, and both networks are still propagating.
Laboratory Strategies to Evaluate Enhanced Geothermal Systems (EGS) in Scale Model Experiments
Authors: Villaquiran-Vargas A. P. , Opperman N. , Knippel E. , Xiong Q. , Sutton C. , Zahasky C. , Hampton J. C. 
Published: August 2024

ABSTRACT:
Enhanced Geothermal Systems (EGS) is an emerging energy technology with increasing attention due to its potential to be developed in most places on Earth, helping to accomplish net zero carbon emissions. To comprehensively understand EGS complex environments and reach its commercial application, pilot demonstration projects, modeling, and laboratory tests are needed. Laboratory-scale tests can assess critical knowledge gaps by conducting research under controlled conditions, allowing to understand mechanisms and then extrapolate them at the field scale, especially those contributing to, and controlling, flow heterogeneity. Particularly, block samples are useful to study EGS because they enable the evaluation of interactions between wells, networks, and circulation schemes at reservoir conditions, especially heat/flow properties. Different practices can be performed at this scale regarding wells configuration. It is possible to create a fracture and then locate it aided by nondestructive evaluation methods and interpolations, after that, a production well can be drilled intercepting the fracture plane. Likewise, it is possible to drill the injector and producer wells at the beginning if fracture caging is intended. This under-stress experiment uses a large granite specimen of 30x30x45cm that was placed in a polyaxial frame to fracture and monitor fluid flow. To do this a fracture was created through hydraulic fracturing. Different multiphysics such as acoustic emission sensing and fiber optic cable, were used to monitor fracture creation and characterize fracture flow.

1 INTRODUCTION
According to The Office of Energy Efficiency and Renewable Energy of the United States EERE (2022), geothermal resources have the confirmed ability to generate 90 GW of electricity by 2050, becoming a key component to face climate change. The main contributors to achieve this goal are Enhanced Geothermal Systems (EGS), unconventional reservoirs with significant stored thermal energy and low hydraulic connectivity i.e., Hot Dry Rocks, that can be found anywhere in the world. To unlock EGS potential, a certain number of challenges associated with reaching deep rock targets and creating large flow paths (fractures) in tight rocks, need to be solved (Villaquiran Vargas et al., 2023). In addition, a detrimental flow pattern such as flow channeling might occur in EGS, leading to premature cooling of the fractures that carry the fastest and largest volumes of fluid. By increasing the injection-production well spacing, the production life of a geothermal reservoir might be extended (Fu et al., 2015).