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At least 55 records · Page 3

Mechanical properties of lunar regolith and lunar soil simulant

Through the Surveyor 3 and 7, and Apollo 11-17 missions a knowledge of the mechanical properties of Lunar regolith were gained. These properties, including material cohesion, friction, in-situ density, grain-size distribution and shape, and porosity, were determined by indirect means of trenching, penetration, and vane shear testing. Several of these properties were shown to be significantly different from those of terrestrial soils, such as an interlocking cohesion and tensile strength formed in the absence of moisture and particle cementation. To characterize the strength and deformation properties of Lunar regolith experiments have been conducted on a lunar soil simulant at various initial densities, fabric arrangements, and composition. These experiments included conventional triaxial compression and extension, direct tension, and combined tension-shear. Experiments have been conducted at low levels of effective confining stress. External conditions such as membrane induced confining stresses, end platten friction and material self weight have been shown to have a dramatic effect on the strength properties at low levels of confining stress. The solution has been to treat these external conditions and the specimen as a full-fledged boundary value problem rather than the idealized elemental cube of mechanics. Centrifuge modeling allows for the study of Lunar soil-structure interaction problems. In recent years centrifuge modeling has become an important tool for modeling processes that are dominated by gravity and for verifying analysis procedures and studying deformation and failure modes. Centrifuge modeling is well established for terrestrial enginering and applies equally as well to Lunar engineering. A brief review of the experiments is presented in graphic and outline form.

Steven W Perkins↗

Application of Satellite SAR Imagery in Mapping the Active Layer of Arctic Permafrost

A method of mapping the active layer of Arctic permafrost using a combination of conventional synthetic aperture radar (SAR) backscatter and more sophisticated interferometric SAR (INSAR) techniques is proposed. The proposed research is based on the sensitivity of radar backscatter to the freeze and thaw status of the surface soil, and the sensitivity of INSAR techniques to centimeter- to sub-centimeter-level surface differential deformation. The former capability of SAR is investigated for deriving the timing and duration of the thaw period for surface soil of the active layer over permafrost. The latter is investigated for the feasibility of quantitative measurement of frost heaving and thaw settlement of the active layer during the freezing and thawing processes. The resulting knowledge contributes to remote sensing mapping of the active layer dynamics and Arctic land surface hydrology.

Li, Shu-Sun↗

Absorbing boundary conditions in material point method adopting perfectly matched layer theory

This study focuses on solving the numerical challenges of imposing absorbing boundary conditions for dynamic simulations in the material point method (MPM). To attenuate elastic waves leaving the computational domain, the current work integrates the Perfectly Matched Layer (PML) theory into the implicit MPM framework. The proposed approach introduces absorbing particles surrounding the computational domain that efficiently absorb outgoing waves and reduce reflections, allowing for accurate modeling of wave propagation and its further impact on geotechnical slope stability analysis. The study also includes several benchmark tests to validate the effectiveness of the proposed method, such as several types of impulse loading and symmetric and asymmetric base shaking. The conducted numerical tests also demonstrate the ability to handle large deformation problems, including the failure of elasto-plastic soils under gravity and dynamic excitations. The findings extend the capability of MPM in simulating continuous analysis of earthquake-induced landslides, from shaking to failure.

58 GEOSCIENCES↗

A borehole jack for deformability, strength, and stress measurements in a 2-inch borehole

A borehole jack devised for lunar exploration is described and results of its use in simulated lunar solids are presented. A hydraulic cylinder mounted between two stiff plates acts to spread the plates apart against the borehole walls when pressured. The spreading is measured by a displacement transducer and the load is measured hydraulically. The main improvement over previous instruments is the increased stroke, which allows large deformations of the borehole. Twenty-eight pistons are used to obtain a high hydraulic efficiency, and three return pistons are also provided. Pressure-deformation curves were obtained for each test on Lunar Soil Simulant No. 2, a light gray silty basalt powder.

Goodman, R. E.↗

A Probabilistic Mass Estimation Algorithm for a Novel 7- Channel Capacitive Sample Verification Sensor

A document describes an algorithm created to estimate the mass placed on a sample verification sensor (SVS) designed for lunar or planetary robotic sample return missions. A novel SVS measures the capacitance between a rigid bottom plate and an elastic top membrane in seven locations. As additional sample material (soil and/or small rocks) is placed on the top membrane, the deformation of the membrane increases the capacitance. The mass estimation algorithm addresses both the calibration of each SVS channel, and also addresses how to combine the capacitances read from each of the seven channels into a single mass estimate. The probabilistic approach combines the channels according to the variance observed during the training phase, and provides not only the mass estimate, but also a value for the certainty of the estimate. SVS capacitance data is collected for known masses under a wide variety of possible loading scenarios, though in all cases, the distribution of sample within the canister is expected to be approximately uniform. A capacitance-vs-mass curve is fitted to this data, and is subsequently used to determine the mass estimate for the single channel s capacitance reading during the measurement phase. This results in seven different mass estimates, one for each SVS channel. Moreover, the variance of the calibration data is used to place a Gaussian probability distribution function (pdf) around this mass estimate. To blend these seven estimates, the seven pdfs are combined into a single Gaussian distribution function, providing the final mean and variance of the estimate. This blending technique essentially takes the final estimate as an average of the estimates of the seven channels, weighted by the inverse of the channel s variance.

Wolf, Michael↗

Evaluation of Instability Phenomena in Sands: Plane Strain Versus Triaxial Conditions

Extensive research was carried out in the 1950s on theories of plasticity to extend the concepts developed for metals to materials that failed according to the Mohr-Coulomb criterion. The new ideas made it possible to merge the two distinct concepts (strength and deformation techniques) into one that relies on better understanding of plasticity and resulted in a rapid growth in the field of constitutive modeling of soil behavior. At the same time advanced experimental apparatuses and laboratory procedures were developed to calibrate the models. However, most laboratory experiments on granular materials are performed under Conventional Triaxial Conditions (CTC) for the purposes of evaluating constitutive behavior and stability properties, whereas most geotechnical field problems are closer to the Plane Strain (PS) condition. The triaxial tests performed in most laboratories comprise a simplification over in situ states and allow easier and robust experimentation. Most landslide problems, failure of soils beneath shallow and deep foundations, and failure of retaining structures, are cases that can generally be considered as plane strain. Strength and deformation characteristics of granular materials loaded in plane strain may be considerably different from those observed in CTC. Most studies on sands were limited to evaluating the constitutive behavior and in some cases extended to briefly describing the associated instability phenomena. This paper presents the results of a series of PS and CTC experiments performed on fine uniform silica sand known as F-75 Ottawa sand. Advanced analysis techniques were used to study the instability phenomena, which yielded very accurate measurements of shear bands occurrences and patterns. Destructive thin-sectioning technique along with monitoring the specimen surface deformation was used in the PS experiments and Computed Tomography (CT) was used to investigate the progress of primary and secondary shear bands in specimens subjected to CTC. Comparison between the two cases will be presented and discussed.

Alshibli, Khalid A.↗

Shock-metamorphic effects in the Luna-16 soil sample from Mare Fecunditatis

The results of intensive studies indicate that shock-metamorphic effects, characteristic of meteorite impact and virtually identical to those observed in Apollo samples, are common in fragments of the Luna-16 soil sample from Mare Fecunditatis. Two types of shock effects are present: (1) deformation and partial melting features in rock and mineral fragments (1-2 percent of fragments); and (2) heterogeneous glasses and glassy breccias produced by shock melting (70-80 percent of fragments). Shock effects were observed in pyroxene (deformation twin lamellae, multiple planar shock lamellae, extreme mosaicism, partial isotropization); in plagioclase (planar shock lamellae, complete isotropization to form maskelynite); and in basalt fragments (plagioclase isotropization, selective partial melting). The glasses exhibit several characteristics of shock melting, especially: (1) diversity in chemical composition; (2) association with shock mineral fragments and Ni-Fe spherules; and (3) heterogeneous schlieren and incipient fusion of mineral inclusions. Two types of source rocks are present in the Luna-16 sample; basaltic (85-90 percent) and feldspathic (10-15 percent). The basaltic rocks are predominant and generally occur as unshocked fragments, indicating that they form the bedrock underlying Mare Fecunditatis.

French, B. M.↗

Enhanced MPM framework with multipatch isogeometric analysis for geotechnical applications

Achieving stable stress solutions at large strains using the Material Point Method (MPM) is challenging due to the accumulation of errors associated with geometry discretization, cell-crossing noise, and volumetric locking. Several simplified attempts exist in the literature to mitigate these errors, including higher-order frameworks. However, the stability of the MPM solution in such frameworks has been limited to simple geometries and the single-phase formulation (i.e., neglecting pore fluid). Although never explored, multipatch isogeometric analysis offers desirable qualities to simulate complex geometries while mitigating errors in the MPM. The degree of required high-order spatial integration has also never been investigated to infer a minimum limit for the stability of the stress solution in MPM. This paper presents a general-purpose numerical framework for simulating stable stresses in porous media, capturing both near incompressibility and multiphase interactions. First, the numerical framework is presented considering Non-Uniform Rational B-splines (NURBS) to perform isogeometric analysis (IGA) in MPM. Additionally, a volumetric strain smoothing algorithm is used to alleviate errors associated with volumetric locking. Second, the manifestation of cell-crossing errors is assessed via a series of problems with orders ranging from linear to cubic interpolation functions. Third, the use of NURBS is investigated and verified for problems with circular geometries. Finally, multipatch analysis is deployed to simulate plane strain and 3D penetration in soils, considering nearly incompressible elastoplastic (total stress) analysis and fully-coupled hydro-mechanical (effective stress) analysis. The stability of the solution is also analyzed for different constitutive models. From the results, it can be concluded that the framework using cubic interpolation functions with strain smoothing is the most convenient, presenting stable stress solutions for a broad range of multiphase geotechnical applications.

58 GEOSCIENCES↗

Ar-40/Ar-39 chronology and cosmic ray exposure ages of the Apollo 15 samples

The Ar-40*/Ar-39* thermal release patterns of igneous soil fragments, rake basalts, and large crystalline rocks are by and large well defined. Shock deformations of up to moderate intensities have no observable effects on the Ar-40*/Ar-39* release patterns. Neither do the Ar-40* diffusion losses have any relationship with the shock intensities. The peak of the magnetic activity in Palus Putredinis occurred at 3.33 plus or minus 0.02 Gy, lava flows continuing up to 3.13 Gy but at much reduced intensity. No correlation between the crystallization ages and the petrographic rock types was observed. The cosmic ray exposure gas indicate a mature regolith around the Hadley Rille-Apennine Front region. The exposure ages of the Apollo 15 samples cannot reliably be used to obtain the time of prominent cratering events at this site.

Husain, L.↗

Lunar and Planetary Science XXXV: Terrestrial Planets

The session "Terrestrial Planets: included:Lunar Soils May Tell Us When the Geomagnetic Field First Appeared; Metal-Silicate Segregation in Deforming Dunitic Rocks: Applications to Core Formation in Europa and Ganymede; Diamond Formation in Core Segregation Experiments; The Effect of Pressure on Potassium Partitioning Between Metallic Liquid and Silicate Melt; Reduction of W, Mn, and Fe, During High-Temperature Vaporization; Micrometeoritic Neon in the Earth s Mantle ; and New Analyses of Diverse Hadean Zircon Inclusions from Jack Hills.

Source record↗

InSAR Monitoring to Evaluate Surface Changes with CO 2 Storage in a Depleted Oil Field in Northern Michigan

Battelle evaluated the potential use of Interferometric Synthetic Aperture Radar (InSAR) for monitoring the outcome of injected CO 2 at the Dover 33 reef near Gaylord, Michigan. InSAR is a satellite-based technology that provides high-precision information on the movement of ground surface in areas with high radar coherence (e.g., roads, buildings, bare soils). Depending on the setting, this technique may provide a useful tool for characterizing reservoirs by measuring surface deformations from activities such as brine water disposal; production of water, oil, and/or gas; and carbon capture, utilization, and storage (CCUS).

47 OTHER INSTRUMENTATION↗

InSAR Monitoring to Evaluate Surface Changes with CO 2 Storage in a Depleted Oil Field in Northern Michigan (Volume II.E)

The Midwest Regional Carbon Sequestration Partnership (MRCSP) was founded in 2003 as part of the U.S. Department of Energy’s (DOE’s) Regional Carbon Sequestration Partnership initiative. Since its founding, MRCSP has made significant strides toward making CCUS a viable option for states in the region. The public/private consortium, funded through the DOE Regional Carbon Sequestration Initiative, brings together nearly 40 industry partners and 10 states. Battelle, as the project lead, oversees research, development and operations and coordinates activities among the partners. The incremental, phased approach has built a valuable knowledge base for the industry and paved the way for commercial-scale adoption of CCUS technologies. From 2008 to 2020, MRCSP Phase III focused on the development of large-scale injection projects. This report is part of a series of reports prepared under the Midwestern Regional Carbon Sequestration Partnership (MRCSP) Phase III (Development Phase). These reports summarize and detail the findings of the work conducted under the Phase III project. This report describes the effort under MRCP to evaluate the potential use of Interferometric Synthetic Aperture Radar (InSAR) for monitoring the outcome of injected CO 2 at the Dover 33 reef near Gaylord, Michigan. InSAR is a satellite-based technology that provides high-precision information on the movement of ground surface in areas with high radar coherence (e.g., roads, buildings, bare soils). Depending on the setting, this technique may provide a useful tool for characterizing reservoirs by measuring surface deformations from activities such as brine water disposal; production of water, oil, and/or gas; and carbon capture, utilization, and storage (CCUS).

54 ENVIRONMENTAL SCIENCES↗

Evaluation of the Second Transport Rotorcraft Airframe Crash Testbed (TRACT 2) Full Scale Crash Test

Two Transport Rotorcraft Airframe Crash Testbed (TRACT) full-scale tests were performed at NASA Langley Research Center's Landing and Impact Research Facility in 2013 and 2014. Two CH-46E airframes were impacted at 33-ft/s forward and 25-ft/s vertical combined velocities onto soft soil, which represents a severe, but potentially survivable impact scenario. TRACT 1 provided a baseline set of responses, while TRACT 2 included retrofits with composite subfloors and other crash system improvements based on TRACT 1. For TRACT 2, a total of 18 unique experiments were conducted to evaluate ATD responses, seat and restraint performance, cargo restraint effectiveness, patient litter behavior, and activation of emergency locator transmitters and crash sensors. Combinations of Hybrid II, Hybrid III, and ES-2 Anthropomorphic Test Devices (ATDs) were placed in forward and side facing seats and occupant results were compared against injury criteria. The structural response of the airframe was assessed based on accelerometers located throughout the airframe and using three-dimensional photogrammetric techniques. Analysis of the photogrammetric data indicated regions of maximum deflection and permanent deformation. The response of TRACT 2 was noticeably different in the longitudinal direction due to changes in the cabin configuration and soil surface, with higher acceleration and damage occurring in the cabin. Loads from ATDs in energy absorbing seats and restraints were within injury limits. Severe injury was likely for ATDs in forward facing passenger seats.

Annett, Martin↗

Overview of the Transport Rotorcraft Airframe Crash Testbed (TRACT) Full Scale Crash Tests

The Transport Rotorcraft Airframe Crash Testbed (TRACT) full-scale tests were performed at NASA Langley Research Center's Landing and Impact Research Facility in 2013 and 2014. Two CH-46E airframes were impacted at 33-ft/s forward and 25-ft/s vertical combined velocities onto soft soil, which represents a severe, but potentially survivable impact scenario. TRACT 1 provided a baseline set of responses, while TRACT 2 included retrofits with composite subfloors and other crash system improvements based on TRACT 1. For TRACT 2, a total of 18 unique experiments were conducted to evaluate Anthropomorphic Test Devices (ATD) responses, seat and restraint performance, cargo restraint effectiveness, patient litter behavior, and activation of emergency locator transmitters and crash sensors. Combinations of Hybrid II, Hybrid III, and ES-2 ATDs were placed in forward and side facing seats and occupant results were compared against injury criteria. The structural response of the airframe was assessed based on accelerometers located throughout the airframe and using three-dimensional photogrammetric techniques. Analysis of the photogrammetric data indicated regions of maximum deflection and permanent deformation. The response of TRACT 2 was noticeably different in the horizontal direction due to changes in the cabin configuration and soil surface, with higher acceleration and damage occurring in the cabin. Loads from ATDs in energy absorbing seats and restraints were within injury limits. Severe injury was likely for ATDs in forward facing passenger seats.

Annett, Martin↗

Hydrostar Thermal and Structural Deformation Analyses of Antenna Array Concept

The proposed Hydrostar mission used a large orbiting antenna array to demonstrate synthetic aperture technology in space while obtaining global soil moisture data. In order to produce accurate data, the array was required to remain as close as possible to its perfectly aligned placement while undergoing the mechanical and thermal stresses induced by orbital changes. Thermal and structural analyses for a design concept of this antenna array were performed. The thermal analysis included orbital radiation calculations, as well as parametric studies of orbit altitude, material properties and coating types. The thermal results included predicted thermal distributions over the array for several cases. The structural analysis provided thermally-driven deflections based on these cases, as well as based on a 1-g inertial load. In order to minimize the deflections of the array in orbit, the use of XN70, a carbon-reinforced polycyanate composite, was recommended.

Amundsen, Ruth M.↗

PowderSim: Lagrangian Discrete and Mesh-Free Continuum Simulation Code for Cohesive Soils

PowderSim is a calculation tool that combines a discrete-element method (DEM) module, including calibrated interparticle-interaction relationships, with a mesh-free, continuum, SPH (smoothed-particle hydrodynamics) based module that utilizes enhanced, calibrated, constitutive models capable of mimicking both large deformations and the flow behavior of regolith simulants and lunar regolith under conditions anticipated during in situ resource utilization (ISRU) operations. The major innovation introduced in PowderSim is to use a mesh-free method (SPH-based) with a calibrated and slightly modified critical-state soil mechanics constitutive model to extend the ability of the simulation tool to also address full-scale engineering systems in the continuum sense. The PowderSim software maintains the ability to address particle-scale problems, like size segregation, in selected regions with a traditional DEM module, which has improved contact physics and electrostatic interaction models.

Johnson, Scott↗

Ambient field seismology in critical zone hydrological sciences

Passive ambient noise monitoring is an emerging tool in environmental seismology, leveraging the ambient seismic field to assess temporal variations in shallow subsurface properties. This review focuses on the potential and challenges of using scattered coda waves from noise correlation functions to monitor critical zone dynamics. The sensitivity of seismic velocities to various environmental factors, including precipitation, snowmelt, atmospheric pressure, and groundwater fluctuations, underscores the method’s versatility. While coda waves excel in detecting subtle changes due to their scattered nature, ballistic waves provide higher spatial resolution, albeit with challenges in source stability. Advances in seismic sensing, including distributed acoustic sensing and low-cost geophone networks, have enabled high-resolution monitoring of hydrological processes, subsurface deformation, and seismic hazards. Integrating seismic data with hydrological models provides insights into water storage, pore pressure changes, and soil moisture dynamics. However, limitations in spatial resolution, calibration with ground truth data, and coupled effects between environmental factors remain key challenges. This review emphasizes the importance of interdisciplinary approaches in refining methodologies, enhancing sensor deployments, and addressing data gaps. Passive seismic monitoring offers opportunities to understand critical zone processes and their broader impacts on seismic hazards and environmental sustainability.

58 GEOSCIENCES↗