Laboratory Study On Mechanical Response And Failure Mechanism of Red-Bed Soft Rock Under Water-Rock Interaction

2021 ◽  
Author(s):  
Chi Liu ◽  
Xiaoli Liu ◽  
Huan Sun ◽  
Mingyang Wang ◽  
Chunlu Wu ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Soft Rock ◽  
Failure Characteristics ◽  
Mechanical Coupling ◽  
Experimental Platform ◽  
Multi Level ◽  
Fissure Water ◽  
Level Loading ◽  
Red Bed

Abstract Red-bed soft rock is a geomaterial that displays special deformation and failure characteristics. The stability of red-bed slopes can be negatively impacted by water and stepped excavation disturbance; however, there is limited research regarding the mechanical behavior and failure characteristics of red-bed soft rock under the action of water-rock hydro-mechanical coupling. In this study, to explore the mechanical response and failure mechanisms of red-bed soft rock under coupled water-rock hydro-mechanical action, a visual experimental platform based on digital radiography and a multi-level loading device was constructed. Angiography was used to visualize the rock fracture process by replacing fissure water with a contrast medium. Multi-level loading was applied to cubic red-bed mudstone samples, and acoustic emission signals, stress, flow rate, and digital radiography images were collected during the failure process. An original image processing method based on Hough transform and a convolutional neural network was used to segment and extract cracks from the imagery, and fissure water flow characteristics, rock mechanical response, and crack evolution were analyzed in detail (Liu et al., 2015; Lv et al., 2013, 2014). Results showed that when the Felicity ratio FR was lower than 1.2, water could induce secondary "water-damaged cracks" in the red-bed samples. Study findings were used to highlight the importance of improved early-warning methods for rainfall-induced landslides at an engineering scale. The original experimental platform proposed and evaluated in this study provides a new and powerful tool to investigate the mechanical behavior of different rock types under the action of water-rock hydro-mechanical coupling at a laboratory scale. These findings will facilitate improved disaster prevention strategies for red-bed geological bodies.

scholarly journals A Comprehensive Review of the Mechanical Behavior of Suspension Bridge Tunnel-Type Anchorage

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Yafeng Han ◽  
Xinrong Liu ◽  
Ning Wei ◽  
Dongliang Li ◽  
Zhiyun Deng ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
Load Transfer ◽  
Mechanical Response ◽  
Soft Rock ◽  
Suspension Bridge ◽  
Development Trend ◽  
Factors Affecting ◽  
Research Results ◽  
Rock Strata

The recent surge of interest towards the mechanical response of rock mass produced by tunnel-type anchorage (TTA) has generated a handful of theories and an array of empirical explorations on the topic. However, none of these have attempted to arrange the existing achievements in a systematic way. The present work puts forward an integrative framework laid out over three levels of explanation and practical approach, mechanical behavior, and calculation method of the ultimate pullout force to compare and integrate the existing findings in a meaningful way. First, it reviews the application of TTA in China and analyzes its future development trend. Then, it summarizes the research results of TTA in terms of load transfer characteristics, deformation characteristics, failure modes, and calculation of ultimate uplift resistance. Finally, it introduces four field model tests in soft rock (mainly mudstone formations), and some research results are obtained. Furthermore, it compares the mechanical behavior of TTA in hard rock strata and soft rock strata, highlighting the main factors affecting the stability of TTA in soft rock formation. This paper proposes a series of focused topics for future investigation that would allow deconstruction of the drivers and constraints of the development of TTA.

scholarly journals Numerical Implementation of a Hydro-Mechanical Coupling Constitutive Model for Unsaturated Soil Considering the Effect of Micro-Pore Structure

2021 ◽  
Vol 11 (12) ◽  
pp. 5368
Author(s):  
Guoqing Cai ◽  
Bowen Han ◽  
Mengzi Li ◽  
Kenan Di ◽  
Yi Liu ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Mechanical Behavior ◽  
Pore Structure ◽  
Unsaturated Soil ◽  
Fortran Program ◽  
Numerical Implementation ◽  
Numerical Application ◽  
Integration Algorithm ◽  
Mechanical Coupling ◽  
Numerical Program

An unsaturated soil constitutive model considering the influence of microscopic pore structure can more accurately describe the hydraulic–mechanical behavior of unsaturated soil, but its numerical implementation is more complicated. Based on the fully implicit Euler backward integration algorithm, the ABAQUS software is used to develop the established hydro-mechanical coupling constitutive model for unsaturated soil, considering the influence of micro-pore structure, and a new User-defined Material Mechanical Behavior (UMAT) subroutine is established to realize the numerical application of the proposed model. The developed numerical program is used to simulate the drying/wetting cycle process of the standard triaxial specimen. The simulation results are basically consistent with those calculated by the Fortran program, which verifies the rationality of the developed numerical program.

scholarly journals Study on the Mechanical Behavior of Double Primary Support of Soft Rock Tunnel under High Ground Stresses and Large Deformation

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Zhe Liu
Keyword(s):  
Mechanical Behavior ◽  
Large Deformation ◽  
Design Method ◽  
Characteristic Curve ◽  
Soft Rock ◽  
Support Design ◽  
Deformation Amount ◽  
Secondary Lining ◽  
Rock Tunnels ◽  
Primary Support

Double primary support structures could effectively solve the problem of large deformation of surrounding rock for soft rock tunnels. However, the mechanical behavior of this new support structure is still incomplete, and the design method should be revised. Based on the theory of energy conversion, this paper analyzes the support characteristic curve of double primary support and puts forward the dynamic design method of double primary support. Considering that the secondary lining can be set after monitoring the deformation amount and deformation rate of the first primary support, its support parameters can be dynamically adjusted according to the actual situation. By applying the double primary support design method in the Maoxian tunnel of Chenglan Railway, the field monitoring results show that the double primary support has a significant effect on the energy release of surrounding rocks, greatly reducing the load acting on the secondary lining and ensuring the safety and reliability of the tunnel structure.

scholarly journals Experimental Investigation of the Mechanical Behavior of NC Linings in consideration of Voids and Lining Thinning

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Zude Ding ◽  
Jincheng Wen ◽  
Xiafei Ji ◽  
Zhihua Ren ◽  
Sen Zhang
Keyword(s):  
Mechanical Behavior ◽  
Local Deformation ◽  
Scale Model ◽  
Test Results ◽  
Load Bearing Capacity ◽  
Normal Concrete ◽  
Failure Characteristics ◽  
Defect Position ◽  
Deformation Properties ◽  
Combined Defects

The presence of voids or lining thinning directly affects the mechanical behavior of linings, and these defects threaten the safety of tunnel operation. In this study, a series of 1/5-scale model tests was used to investigate the mechanical behavior of normal concrete (NC) linings in consideration of voids and combined defects. Test results showed that the void and combined defects substantially reduced the load-bearing capacity and deformation properties of the linings. The inelastic mechanical behavior of the linings was also significantly affected by the defects. The effects of lining defects located at the spandrel were slightly weaker than those of lining defects located at the crown. As the void size or degree of combined defects increased, the tensile strain at the location of the lining defects also increased. Therefore, the defect position of the linings was easily damaged. The defects considerably reduced the overall deformation of the linings but increased the local deformation. The distribution of lining cracks was concentrated at the defect position. In addition, different failure characteristics of the lining were observed due to the differences in defects.

Dependence of Mechanical Behavior of the Murine Tail Disc on Regional Material Properties: A Parametric Finite Element Study

2005 ◽  
Vol 127 (7) ◽  
pp. 1158-1167 ◽  
Author(s):  
Adam H. Hsieh ◽  
Diane R. Wagner ◽  
Louis Y. Cheng ◽  
Jeffrey C. Lotz
Keyword(s):  
Finite Element ◽  
Mechanical Behavior ◽  
Nucleus Pulposus ◽  
Material Properties ◽  
Mechanical Response ◽  
Swelling Pressure ◽  
Transient Behavior ◽  
Sensitivity Analyses ◽  
Intact Mouse

In vivo rodent tail models are becoming more widely used for exploring the role of mechanical loading on the initiation and progression of intervertebral disc degeneration. Historically, finite element models (FEMs) have been useful for predicting disc mechanics in humans. However, differences in geometry and tissue properties may limit the predictive utility of these models for rodent discs. Clearly, models that are specific for rodent tail discs and accurately simulate the disc’s transient mechanical behavior would serve as important tools for clarifying disc mechanics in these animal models. An FEM was developed based on the structure, geometry, and scale of the mouse tail disc. Importantly, two sources of time-dependent mechanical behavior were incorporated: viscoelasticity of the matrix, and fluid permeation. In addition, a novel strain-dependent swelling pressure was implemented through the introduction of a dilatational stress in nuclear elements. The model was then validated against data from quasi-static tension-compression and compressive creep experiments performed previously using mouse tail discs. Finally, sensitivity analyses were performed in which material parameters of each disc subregion were individually varied. During disc compression, matrix consolidation was observed to occur preferentially at the periphery of the nucleus pulposus. Sensitivity analyses revealed that disc mechanics was greatly influenced by changes in nucleus pulposus material properties, but rather insensitive to variations in any of the endplate properties. Moreover, three key features of the model—nuclear swelling pressure, lamellar collagen viscoelasticity, and interstitial fluid permeation—were found to be critical for accurate simulation of disc mechanics. In particular, collagen viscoelasticity dominated the transient behavior of the disc during the initial 2200s of creep loading, while fluid permeation governed disc deformation thereafter. The FEM developed in this study exhibited excellent agreement with transient creep behavior of intact mouse tail motion segments. Notably, the model was able to produce spatial variations in nucleus pulposus matrix consolidation that are consistent with previous observations in nuclear cell morphology made in mouse discs using confocal microscopy. Results of this study emphasize the need for including nucleus swelling pressure, collagen viscoelasticity, and fluid permeation when simulating transient changes in matrix and fluid stress/strain. Sensitivity analyses suggest that further characterization of nucleus pulposus material properties should be pursued, due to its significance in steady-state and transient disc mechanical response.

A Proof of Concept Study of the Mechanical Behavior of Lattice Structures Used to Design a Shoulder Hemi-Prosthesis

2021 ◽  
Author(s):  
Marinela Peto ◽  
Oscar Aguilar-Rosas ◽  
Erick Erick Ramirez-Cedillo ◽  
Moises Jimenez ◽  
Adriana Hernandez ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Cell Attachment ◽  
Lattice Structure ◽  
Material Model ◽  
Patient Specific ◽  
Hexagonal Prism ◽  
Lattice Structures ◽  
Proof Of Concept

Abstract Lattice structures offer great benefits when employed in medical implants for cell attachment and growth (osseointegration), minimization of stress shielding phenomena, and weight reduction. This study is focused on a proof of concept for developing a generic shoulder hemi-prosthesis, from a patient-specific case of a 46 years old male with a tumor on the upper part of his humerus. A personalized biomodel was designed and a lattice structure was integrated in its middle portion, to lighten weight without affecting humerus’ mechanical response. To select the most appropriate lattice structure, three different configurations were initially tested: Tetrahedral Vertex Centroid (TVC), Hexagonal Prism Vertex Centroid (HPVC), and Cubic Diamond (CD). They were fabricated in resin by digital light processing and its mechanical behavior was studied via compression testing and finite element modeling (FEM). The selected structure according to the results was the HPVC, which was integrated in a digital twin of the biomodel to validate its mechanical performance through FEM but substituting the bone material model with a biocompatible titanium alloy (Ti6Al4V) suitable for prostheses fabrication. Results of the simulation showed acceptable levels of Von Mises stresses (325 MPa max.), below the elastic limit of the titanium alloys, and a better response (52 MPa max.) in a model with equivalent elastic properties, with stress performance in the same order of magnitude than the showed in bone’s material model.

Mechanical response of double-stranded DNA to dynamic excitation

2021 ◽  
pp. 107754632110458
Author(s):  
Hamze Mousavi ◽  
Moein Mirzaei ◽  
Samira Jalilvand
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Actual Condition ◽  
Dimensional System ◽  
One Dimensional ◽  
Linear Elastic ◽  
Dynamic Excitation ◽  
Double Stranded Dna ◽  
Elastic Forces ◽  
Mass Spring

The present work investigates the vibrational properties of a DNA-like structure by means of a harmonic Hamiltonian and the Green’s function formalism. The DNA sequence is considered as a quasi one-dimensional system in which the mass-spring pairs are randomly distributed inside each crystalline unit. The sizes of the units inside the system are increased, in a step-by-step approach, so that the actual condition of the DNA could be modeled more accurately. The linear-elastic forces mimicking the bonds between the pairs are initially considered constant along the entire length of the system. In the next step, these forces are randomly shuffled so as to take into account the inherent randomness of the DNA. The results reveal that increasing the number of mass-spring pairs in the crystalline structure decreases the influence of randomness on the mechanical behavior of the structure. This also holds true for systems with larger crystalline units. The obtained results can be used to investigate the mechanical behavior of similar macro-systems.

scholarly journals Preliminary study on the mechanical behavior of friction spot welds

2009 ◽  
Vol 14 (3) ◽  
pp. 238-247 ◽  
Author(s):  
José Antônio Esmerio Mazzaferro ◽  
Tonilson de Souza Rosendo ◽  
Cíntia Cristiane Petry Mazzaferro ◽  
Fabiano Dornelles Ramos ◽  
Marco Antônio Durlo Tier ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Spot Welding ◽  
Mechanical Response ◽  
Analysis Procedure ◽  
Research Centre ◽  
Friction Stir ◽  
Lap Shear ◽  
State Process ◽  
Welding Processes

The Friction Spot Welding - FSpW is a solid-state process that allows joining two or more metal sheets in lap configuration with no residual keyhole as occurs in the Friction Stir Welding - FSW process. The present work reports part of the efforts made at GKSS Research Centre to better understand the complex phenomena that take place during FSpW of aluminum alloys and establish the mechanical response of the resulting joints. Over the recent years the research on modeling friction based welding processes has increased considerably. Most of the works related to this subject deal with the process mechanics. On the other hand, some investigations have shown how the process variables affect the mechanical properties of the joints, but it is very difficult to find quantitative results that can be readily used for mechanical design purposes. The aim of this work is to develop an analysis procedure based on the process characteristics that allows evaluating how the resulting geometry and microstructure affect the joint mechanical behavior. For this, the results of the mechanical tests obtained on AA2024-T3 aluminum alloy were used to calibrate and validate a numerical model that was used to predict the joint failure mode. The model reproduced the specimen geometry and load conditions adopted in the lap-shear and cross-tensile tests. The joint was considered as formed by three main regions (SZ - stir zone, TMAZ - thermo mechanically affected zone and HAZ - heat affected zone) whose properties and dimensions were based in microhardness evaluation and macrographic analysis of welded specimens. It was observed a good agreement between the simulation results and experimental data. The numerical modeling of the joints allows the prediction of the joint mechanical properties, as well as to understand how a change in geometry and property of each region affects the final mechanical behavior. Based in the obtained results, the analysis procedure can be easily extended to the related friction based spot processes as Friction Stir Spot Welding - FSSW.

Experimental Study on Mechanical Behavior of Cold-Formed Steel Three Limbs Built-up Section Members

2010 ◽  
Vol 163-167 ◽  
pp. 651-654
Author(s):  
Tian Hua Zhou ◽  
Shao Feng Nie ◽  
Xiang Bin Liu ◽  
Guang Yi Li
Keyword(s):  
Experimental Study ◽  
Mechanical Behavior ◽  
Axial Compression ◽  
Local Buckling ◽  
Distortional Buckling ◽  
Torsional Buckling ◽  
Failure Characteristics ◽  
Compression Load ◽  
Cold Formed Steel ◽  
Flexural Torsional Buckling

18 specimens of cold-formed steel three limbs built-up section members are tested under axial compression load in this paper. The section forms are divided into two categories: A and B. Load-displacement (P-Δ) curves and failure characteristics of specimens are obtained. The results show that: As to section A members, the failure characteristics of LC, MC and SC series of specimens are flexural-torsional buckling, torsional buckling and distortional buckling, local buckling and distortional buckling. As to section B members, the failure characteristics of LC, MC series of specimens are flexural buckling, while local buckling and distortional buckling for members of SC series.

Constitutive Modeling of Biaxial Mechanical Response of Arteries Subjected to Gradual Elastin Degradation

2013 ◽  
Author(s):  
Shahrokh Zeinali-Davarani ◽  
Ming-Jay Chow ◽  
Raphaël Turcotte ◽  
Katherine Yanhang Zhang
Keyword(s):  
Tensile Test ◽  
Mechanical Behavior ◽  
Test Data ◽  
Constitutive Modeling ◽  
Mechanical Response ◽  
Collagen Fibers ◽  
Biaxial Tensile Test ◽  
Elastin Degradation ◽  
Adaptive Processes ◽  
Tensile Test Data

The passive mechanical response of arteries is believed to be mainly dominated by elastin and collagen fibers. Many arterial diseases are accompanied by significant changes in quantity and as well as the microstructure of these constituents due to the mechanical and biological adaptive processes. In this study we focus on the biaxial tensile test data of elastase-treated porcine aortic tissues [1]. We study the mechanical behavior of aortic tissues under gradual elastin degradation through constitutive modeling and associate the mechanical response with the microstructure of collagen observed in the microscopic images of fresh and digested tissues.

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