scholarly journals The Mechanics of Initiation and Development of Thrust Ramps

2021 ◽  
Author(s):  
Sarah Wigginton ◽  
Elizabeth Petrie ◽  
James Evans
Keyword(s):  
Boundary Condition ◽  
Kinematic Model ◽  
Thrust Fault ◽  
Displacement Boundary ◽  
Mechanical Stratigraphy ◽  
Frictional Strength ◽  
Mechanical Models ◽  
Fold Formation ◽  
Stratified Rock ◽  
Stress Variations

We examine the mechanics of thrust fault initiation and development in sedimentary rocks which accounts for vertical variation in mechanical strength of the rocks. We use numerical mechanical models of mechanically layered rocks to examine thrust ramp nucleation in competent units, and fault propagation upward and downward into weaker units forming folds at both fault tips. We investigate the effects of mechanical stratigraphy on stress heterogeneity, rupture direction, fold formation, and fault geometry motivated by the geometry of the Ketobe Knob thrust fault in central Utah. The study incorporates finite element models to examine how mechanical stratigraphy, loading conditions, and fault configurations determine temporal and spatial variation in stress and strain. We model the predicted deformation and stress distributions in four model domains: (1) an intact, mechanically stratified rock sequence, (2) a mechanically stratified section with a range of interlayer frictional strengths, and two faulted models, (3) one with a stress boundary condition, and (4) one with a displacement boundary condition. The models show that a dramatic increase in stress develops in the competent rock layers whereas the stresses are lower in the weaker rocks. The frictional models reveal that the heterogeneous stress variations increase contact frictional strength. Faulted models contain a 20° dipping fault in the most competent unit. The models show an increase in stress in areas above and below fault tips, with extremely high stresses predicted in a ‘back thrust’ location at the lower fault tip. These findings support the hypothesis that thrust faults and associated folds at the Ketobe Knob developed in accordance with the ramp-first kinematic model and development of structures was significantly influenced by the nature of the mechanical stratigraphy.

Finite Element Analysis’s Discussion of Steel-Concrete

2015 ◽  
Vol 1089 ◽  
pp. 299-302
Author(s):  
Lan Xiang Chen ◽  
De Shen Zhao ◽  
Lei Liu
Keyword(s):  
Mechanical Properties ◽  
Boundary Condition ◽  
Finite Element ◽  
Steel Tube ◽  
Pure Bending ◽  
Steel Reinforced Concrete ◽  
Finite Element Software ◽  
Plastic Damage ◽  
Mechanical Models ◽  
Damage Constitutive Model

To analyze the mechanical properties of steel tube filled with steel-reinforced concrete(STSRC), the mechanical models and some related problems of STSRC under different loading ways are proposed for the analysis on the base of finite element software: the concrete plastic damage constitutive model, the contact between steel and the treatment of boundary condition, etc. There are three types of specimen for analysis: short column, long column and pure bending beam. The results indicate that the mechanical models and the relevant technical analysis of STSRC are reasonable, and are beneficial to convergence. The discussed methods can provide a reference for the scholars to study on other composite steel-concrete structures.

Analysis of a Fixed-Guided Compliant Beam With an Inflection Point Using the Pseudo-Rigid-Body Model (PRBM) Concept

2012 ◽  
Author(s):  
Ashok Midha ◽  
Sushrut G. Bapat ◽  
Adarsh Mavanthoor ◽  
Vivekananda Chinta
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Rigid Body ◽  
Inflection Point ◽  
Equilibrium Equations ◽  
Displacement Boundary ◽  
Body Model ◽  
Rigid Body Model ◽  
Domain Concept ◽  
Selection Of

This paper provides an efficient method of analysis for a fixed-guided compliant beam with an inflection point, subjected to beam end load or displacement boundary conditions, or a combination thereof. To enable this, such a beam is modeled as a pair of well-established pseudo-rigid-body models (PRBMs) for fixed-free compliant beam segments. The analysis procedure relies on the properties of inflection in developing the necessary set of static equilibrium equations for solution. The paper further discusses the multiplicity of possible solutions, including displacement configurations, for any two specified beam end boundary conditions, depending on the locations of the effecting force and/or displacement boundary conditions. A unique solution may exist when a third beam end boundary condition is specified; however, this selection is not unconditional. A deflection domain concept is proposed to assist with the selection of the third boundary condition in a more realistic manner.

Interaction of a mantle plume and a moving plate: insights from numerical modeling

2020 ◽  
Author(s):  
Sascha Brune ◽  
Marzieh Baes ◽  
Taras Gerya ◽  
Stephan Sobolev
Keyword(s):  
Boundary Condition ◽  
Mantle Plume ◽  
Critical Radius ◽  
Oceanic Lithosphere ◽  
Plate Motion ◽  
Moving Plate ◽  
Kinematic Boundary Condition ◽  
Mechanical Models ◽  
Stationary Plate ◽  
Do So

<p>The impingement of a hot buoyant mantle plume onto the lithosphere can result in either breaking of the lithosphere, which might results in subduction initiation or in under-plating of the plume beneath the lithosphere. Key natural examples of the former and latter are formation of subduction along the southern margin of Caribbean and northwestern South America in the late Cretaceous as well as the hotspot chains of Hawaii, respectively. In previous studies the interaction of a buoyant mantle plume with lithosphere was investigated either for the case of stationary lithosphere or for moving lithosphere but ignoring the effect of magmatic weakening of the lithosphere above the plume head. In this study we aim to investigate the response of a moving lithosphere to the arrival of a stationary mantle plume including the effect of magmatic lithospheric weakening. To do so we use 3d thermo-mechanical models employing the finite difference code I3ELVIS. Our setup consists of an oceanic lithosphere, mantle plume and asthenosphere till depth of 400 km. The moving plate is simulated by imposing a kinematic boundary condition on the lithospheric part of the side boundaries. The mantle plume in our models has a mushroom shape. The experiments differ in the age of the lithosphere, rate of the plate motion and size of the mantle plume. For different combinations of these parameters model results show either (1) breaking of the lithosphere and initiation of subduction above the plume head or (2) asymmetric spreading of the plume material below the lithosphere without large deformation of the lithosphere. We find that the critical radius of the plume that breaks the lithosphere and initiates subduction depends on plume buoyancy and the lithospheric age, but not on the plate speed. In general, the modeling results for the moving plate are similar to the results for a stationary plate, but the shapes of the region of the deformed lithosphere differ.</p>

Analysis of a Fixed-Guided Compliant Beam With an Inflection Point Using the Pseudo-Rigid-Body Model Concept

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Ashok Midha ◽  
Sushrut G. Bapat ◽  
Adarsh Mavanthoor ◽  
Vivekananda Chinta
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Rigid Body ◽  
Inflection Point ◽  
Compliant Mechanism ◽  
Analysis Method ◽  
Model Concept ◽  
Displacement Boundary ◽  
Rigid Body Model ◽  
Selection Of

This paper provides an efficient method of analysis for a fixed-guided compliant beam with an inflection point, subjected to beam end load or displacement boundary conditions, or a combination thereof. To enable this, such a beam is modeled as a pair of well-established pseudo-rigid-body models (PRBMs) for fixed-free compliant beam segments. The analysis procedure relies on the properties of inflection in developing the necessary set of parametric, static equilibrium and compatibility equations for solution. The paper further discusses the multiplicity of possible solutions, including displacement configurations, for any two specified beam end displacement boundary conditions, depending on the locations and types of the effecting loads on the beam to meet these boundary conditions. A unique solution may exist when a third beam end displacement boundary condition is specified; however, this selection is not unconditional. A concept of characteristic deflection domain is proposed to assist with the selection of the third boundary condition to yield a realistic solution. The analysis method is also used to synthesize a simple, fully compliant mechanism utilizing the fixed-guided compliant segments.

Similarity Solution for the Synchronous Grouting of Shield Tunnel Under the Vertical Non-Axisymmetric Displacement Boundary Condition

2016 ◽  
Vol 9 (1) ◽  
pp. 205-232 ◽  
Author(s):  
Jinfeng Zou ◽  
Songqing Zuo
Keyword(s):  
Boundary Condition ◽  
Similarity Solution ◽  
Ground Surface ◽  
Vertical Displacement ◽  
Vertical Surface ◽  
Parameter Analysis ◽  
Shield Tunnel ◽  
Displacement Boundary Condition ◽  
Displacement Boundary ◽  
Grouting Pressure

AbstractSimilarity solution is investigated for the synchronous grouting of shield tunnel under the vertical non-axisymmetric displacement boundary condition in the paper. The synchronous grouting process of shield tunnel was simplified as the cylindrical expansion problem, which was based on the mechanism between the slurry and stratum of the synchronous grouting. The stress harmonic function on the horizontal and vertical ground surfaces is improved. Based on the virtual image technique, stress function solutions and Boussinesq's solution, elastic solution under the vertical non-axisymmetric displacement boundary condition on the vertical surface was proposed for synchronous grouting problems of shield tunnel. In addition, the maximum grouting pressure was also obtained to control the vertical displacement of horizontal ground surface. The validity of the proposed approach was proved by the numerical method. It can be known from the parameter analysis that larger vertical displacement of the horizontal ground surface was induced by smaller tunnel depth, smaller tunnel excavation radius, shorter limb distance, larger expansion pressure and smaller elastic modulus of soils.

Mechanical models of fault propagation folds and comparison to the trishear kinematic model

2003 ◽  
Vol 25 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Néstor Cardozo ◽  
Kavi Bhalla ◽  
Alan T Zehnder ◽  
Richard W Allmendinger
Keyword(s):  
Kinematic Model ◽  
Fault Propagation ◽  
Mechanical Models

Modeling Input Motion Boundary Conditions for Simulations of Geotechnical Shaking Table Tests

2010 ◽  
Vol 26 (2) ◽  
pp. 349-369 ◽  
Author(s):  
Mahadevan Ilankatharan ◽  
Bruce Kutter
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Shaking Table ◽  
Experimental Result ◽  
Displacement Boundary Condition ◽  
Displacement Boundary ◽  
Input Motion ◽  
Displacement Approach ◽  
Table Motion ◽  
Motion Boundary

This paper discusses the effects of using different input-motion-boundary-conditions on the sensitivity of numerical simulations results to errors in material properties of a specimen tested on a shaking table. In the flexible-actuator-prescribed-force-boundary-condition, input is specified by a force across an actuator element that connects the shaking table to a reaction mass. In the prescribed-displacement-boundary-condition, the measured shaking table motion in the experiment is prescribed in the simulation. The flexible-actuator-prescribed-force approach yielded smaller, almost constant sensitivity of simulation results to input properties. The prescribed-displacement approach yielded larger and more variable sensitivities. The sensitivity of results depends on the how the boundary conditions are handled has further implications: the assessment of a comparison between a simulation and an experimental result should be performed with due consideration to the effect of the boundary conditions on the comparison, and numerically determined sensitivities may not be physically meaningful if the boundary condition is not accurately modeled.

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