scholarly journals New granular rock-analogue materials for simulation of multi-scale fault and fracture processes

2021 ◽  
pp. 1-24
Author(s):  
L. Massaro ◽  
J. Adam ◽  
E. Jonade ◽  
Y. Yamada
Keyword(s):  
Quartz Sand ◽  
Strain Curve ◽  
Scaling Factor ◽  
Cohesive Strength ◽  
Dynamic Scaling ◽  
Model Resolution ◽  
Early Results ◽  
Geometrical Scaling ◽  
Analogue Experiments ◽  
Fracture Processes

Abstract In this study, we present a new granular rock-analogue material (GRAM) with a dynamic scaling suitable for the simulation of fault and fracture processes in analogue experiments. Dynamically scaled experiments allow the direct comparison of geometrical, kinematical and mechanical processes between model and nature. The geometrical scaling factor defines the model resolution, which depends on the density and cohesive strength ratios of model material and natural rocks. Granular materials such as quartz sands are ideal for the simulation of upper crustal deformation processes as a result of similar nonlinear deformation behaviour of granular flow and brittle rock deformation. We compared the geometrical scaling factor of common analogue materials applied in tectonic models, and identified a gap in model resolution corresponding to the outcrop and structural scale (1–100 m). The proposed GRAM is composed of quartz sand and hemihydrate powder and is suitable to form cohesive aggregates capable of deforming by tensile and shear failure under variable stress conditions. Based on dynamical shear tests, GRAM is characterized by a similar stress–strain curve as dry quartz sand, has a cohesive strength of 7.88 kPa and an average density of 1.36 g cm−3. The derived geometrical scaling factor is 1 cm in model = 10.65 m in nature. For a large-scale test, GRAM material was applied in strike-slip analogue experiments. Early results demonstrate the potential of GRAM to simulate fault and fracture processes, and their interaction in fault zones and damage zones during different stages of fault evolution in dynamically scaled analogue experiments.

Analogue modelling of strike-slip tectonics from basin to structural-scale comparing silica sand and new rock-analogue materials

2021 ◽  
Author(s):  
Luigi Massaro ◽  
Jürgen Adam ◽  
Elham Jonade ◽  
Yasuhiro Yamada
Keyword(s):  
Fault Zones ◽  
Strike Slip ◽  
Model Material ◽  
Scaling Factor ◽  
Silica Sand ◽  
Model Resolution ◽  
Geometrical Scaling ◽  
Deformation Processes ◽  
Structural Scale ◽  
Fracture Processes

<p>Strike-slip fault zones commonly display complex 3D geometries, with high structural variability along strike and with depth and their architecture and evolution are difficult to analyse. In this regard, analogue modelling represents a powerful tool to investigate the structural, kinematic and mechanical processes in strike-slip fault systems with variable scales. In detail, dynamically scaled experiments allow the direct comparison between model and nature. The geometrical scale factor defines the model resolution, in terms of model/prototype length equivalence, and depends on the physical properties of prototype and model material. Therefore, the choice of the analogue material is critical in scaled analogue experiments.<br>Granular materials like dry silica sand are ideal for the simulation of upper crustal deformation processes due to similar non-linear strain-dependent deformation behaviour of granular flow and brittle rock deformation. Comparing the geometrical scaling factor of the common analogue materials applied in tectonic models, we identified a model resolution gap for the simulation of fault-fracture processes corresponding to the structural scale (1 m – 100 m) observed in fault zones and damage zones in outcrops, field studies or subsurface well data. We developed a new Granular Rock-Analogue Material (GRAM) for the simulation of fault-fracture processes at the structural scale. GRAM is an ultra-weak sand aggregate composed of silica sand and hemihydrate powder capable to deform by tensile and shear failure under variable stress conditions. Based on dynamical shear tests, the new GRAM is characterised by a similar stress-strain curve as dry silica sand and has a geometrical scaling factor L<sup>*</sup>= L<sub>model</sub>/L<sub>nature</sub> = 10<sup>-3</sup> (1 cm in model = 20 m in nature).<br>We performed strike-slip experiments at two different length scales, applying as model material dry silica sand and the new GRAM. Digital Image Correlation (DIC) time-series stereo images of the experiments surface allowed the comparison of the developed structures at different stages of dextral displacement above a single planar basement fault. The analysis of fractures localisation and growth in the strike-slip zone with displacement and strain components enabled the comparison of the different structural styles characterising dry silica sand and GRAM models. The application of the developed GRAM in scaled experiments can provide new insights to the multi-scale investigation of complex deformation processes with analogue models. </p>

scholarly journals On the accuracy of gravity fields obtained with Newton integrals on a hollow sphere

2020 ◽  
Author(s):  
Ludovic Jeanniot ◽  
Cedric Thieulot ◽  
Bart Root ◽  
John Naliboff ◽  
Wim Spakman
Keyword(s):  
Plate Tectonics ◽  
Mass Density ◽  
Plate Boundary ◽  
Spherical Geometry ◽  
Gravity Anomalies ◽  
Scaling Factor ◽  
Density Model ◽  
Satellite Gravity ◽  
Early Results ◽  
Gravity Fields

<p>The mass-density distribution of the Earth drives mantle convection and plate tectonics but is poorly known. We aim to predict gravity fields as a constraint for geodynamical modelling. In order to compute synthetic Earth gravity one must define a spherical geometry filled with a density model. Density models for the whole mantle down to the CMB come from tomographic models which therefore require converting speed waves velocities to density using a scaling factor.</p><p>We use a discretised integration method to compute globally gravity acceleration, gravity anomalies, potential and gradients, in the state of the art finite element code ASPECT.</p><p>Three density models are tested separately: a density field obtained from SL2013 and S40RTS tomographic models for the deep mantle, and the density model CRUST1.0 for the thin upper lithosphere layer. We combine these 3 datasets into one to create a composite model which is compared to the global seismic model LLNL-G3D-JPS of Simmons et al. (2015). We test the sensitivity of gravity prediction on the use of various conversion scaling factors of shear wave velocity to density. We find that the scaling factor profile also has a major impact on gravity prediction.</p><p>Finally, we present early results of the gravity field prediction for two local areas, the Indian-Tibet plate boundary and the Mediterranean Sea. Gravity predictions are compared to satellite gravity.</p>

scholarly journals To what degree the geometry and kinematics of accretionary wedges in analogue experiments is dependent on material properties

2018 ◽  
Author(s):  
Ziran Jiang ◽  
Bin Deng ◽  
Caiwei Fan ◽  
Yu He ◽  
Dong Lai ◽  
...  
Keyword(s):  
Grain Size ◽  
Material Properties ◽  
Quartz Sand ◽  
Accretionary Wedge ◽  
Shape Factors ◽  
Analogue Experiments ◽  
Materials Used ◽  
Grain Sorting ◽  
Basal Detachment ◽  
Geometry And Kinematics

Abstract. Cohesion and friction coefficients are fundamental parameters of granular materials used in analogue experiments. Thus, to test the physical characteristics and mechanical behaviour of the materials used in the experiments will help to better understand into what degree the results of experiments of geological processes depend on the material properties. Our test suggests significant differences between quartz sand and glass bead, in particular the shape factors (~ 1.55 of quartz sand to ~ 1.35 glass bead, angular to rounded) and grain sorting (moderately to well sorted). The glass beads show much better grain sorting and smaller shape factors than the quartz sand. Also they have smaller friction coefficient (~ 0.5 to ~ 0.6) and cohesion (20–30 Ma to 70–100 Ma), no matter of the grain size in our tested samples. The quartz sand shows much smaller friction coefficient (~ 0.6 to ~ 0.65), and smaller cohesion (~ 70 Pa to ~ 100 Pa) than that of smaller grain size sand. We have conducted four sets of analogue experiments with three repeats at the minimum. Our models show that material properties have important influence on the geometry and kinematics of the accretionary wedge. Although the difference in geometries are small, models with larger grain size develop wedges with higher wedge height, larger taper, shorter wedge length and less number of faults under the same amount of bulk shortening. In particular, models with basal detachment (even with 1 mm thickness), show significant difference in geometry and kinematics with that of quartz sand. We thus argue that the geometry and kinematics of the wedge appear to be significantly influenced by relative brittle and ductile strengths, and, to a lesser degree by the layering anisotropy. The basal detachment (even of tiny thickness) determines the first-order control on the location and development of accretionary wedge, in a contrast to the physical properties of brittle materials.

A novel miniaturized log-periodic dipole array antenna using dynamic scaling factor for RFID application

2017 ◽  
Vol 10 (3) ◽  
pp. 345-350
Author(s):  
Pourya Rostami Gooran ◽  
Gholamreza Karimi ◽  
Ali Lalbakhsh
Keyword(s):  
Radio Frequency Identification ◽  
Impedance Matching ◽  
Scaling Factor ◽  
Dynamic Scaling ◽  
Antenna Structure ◽  
Uniformly Separated ◽  
Frequency Identification ◽  
Overall Performance ◽  
Length Reduction ◽  
Proximity Coupling

A novel radio frequency identification antenna based on log-periodic dipole array (LPDA) antenna at 5.8 GHz is presented. The antenna design approach consists of two major steps. Firstly, the conventional primitive method is used to design a traditional LPDA antenna. The antenna structure is then miniaturized and its overall performance significantly improved. Dynamic scaling factor along with uniformly separated elements are introduced in this class of antenna, resulting in a 51.5% length reduction. To improve front-to-back (F/B) ratio a symmetrical folding technique is employed, leading to 21.5 dB F/B ratio for the fabricated prototype. An excellent level of input impedance matching (S11 = −28 dB) is achieved using a well-designed feeding system through a proximity coupling technique. The measured gain of the fabricated prototype is 6.2 dBi, and the overall dimension of the antenna substrate is only 30 × 45 mm2 (0.58λ0 × 0.87λ0).

scholarly journals EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF POLYURETHANE POWDER COMPOSITES

2021 ◽  
Vol 30 (4) ◽  
Author(s):  
Kexin Zhang
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Quartz Sand ◽  
Strain Curve ◽  
Test Block ◽  
Control Group ◽  
Flexural Test ◽  
Polyester Polyol ◽  
Polyurethane Composite ◽  
Powder Composites

In this paper, the effects of emery, lime, quartz sand and cement on the mechanical properties of polyurethane powder composites were studied by three-point flexural test, and the stress-strain curve was drawn. In the flexural test, the polyurethane cement composite formed a control group by changing the content of polyester polyol. When polyester polyol: isocyanate: cement =1:1:2, the average flexural strength of polyurethane cement was 37.1 MPa, and the strain was 10854 με.When polyester polyol: isocyanate: cement =1.15:1:2, the average flexural strength is 38.9 MPa and the strain is 23520 με.When polyester polyol: isocyanate: cement =1.3:1:2, the average flexural strength is 42.5 MPa and the strain is 32942 με. The flexural strength and ductility are improved to a certain extent due to the addition of polyester polyol.The average flexural strength of other polyurethane powder composites such as polyurethane emery test block is 45.1 MPa and the strain is 6203 με, the average flexural strength of polyurethane lime test block is 33.4 MPa and the strain is 6470 με, the average flexural strength of polyurethane quartz sand test block is 49.23 MPa and the strain is 7521 με. The results show that the flexural strength of polyurethane emery material and polyurethane quartz sand material is higher than that of polyurethane cement, which can be used to replace cement to a certain extent to reduce the cost of polyurethane composite material.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Clinical Update: Assessing Maximum Medical Improvement in Carpal Tunnel Syndrome

2003 ◽  
Vol 8 (4) ◽  
pp. 4-5
Author(s):  
Christopher R. Brigham ◽  
James B. Talmage
Keyword(s):  
Carpal Tunnel Syndrome ◽  
Carpal Tunnel ◽  
Proper Time ◽  
Carpal Tunnel Release ◽  
Hand Function ◽  
Factors Affecting ◽  
Early Results ◽  
Medical Evaluation ◽  
Nerve Recovery ◽  
Tunnel Syndrome

Abstract Permanent impairment cannot be assessed until the patient is at maximum medical improvement (MMI), but the proper time to test following carpal tunnel release often is not clear. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) states: “Factors affecting nerve recovery in compression lesions include nerve fiber pathology, level of injury, duration of injury, and status of end organs,” but age is not prognostic. The AMA Guides clarifies: “High axonotmesis lesions may take 1 to 2 years for maximum recovery, whereas even lesions at the wrist may take 6 to 9 months for maximal recovery of nerve function.” The authors review 3 studies that followed patients’ long-term recovery of hand function after open carpal tunnel release surgery and found that estimates of MMI ranged from 25 weeks to 24 months (for “significant improvement”) to 18 to 24 months. The authors suggest that if the early results of surgery suggest a patient's improvement in the activities of daily living (ADL) and an examination shows few or no symptoms, the result can be assessed early. If major symptoms and ADL problems persist, the examiner should wait at least 6 to 12 months, until symptoms appear to stop improving. A patient with carpal tunnel syndrome who declines a release can be rated for impairment, and, as appropriate, the physician may wish to make a written note of this in the medical evaluation report.

Early Results From the Primaries: Life Stress and Childhood

1988 ◽  
Vol 33 (9) ◽  
pp. 812-813
Author(s):  
C. R. Snyder
Keyword(s):  
Life Stress ◽  
Early Results
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