scholarly journals Constitutive Model and Damage Evolution of Mudstone under the Action of Dry-Wet Cycles

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Ming Hu ◽  
Yuanxue Liu ◽  
Linbo Song ◽  
Yu Zhang
Keyword(s):  
Decay Rate ◽  
Damage Evolution ◽  
Mechanical Response ◽  
Test Method ◽  
Natural State ◽  
Rock Masses ◽  
Dissipation Energy ◽  
Energy Principle ◽  
Damage Evolution Equation ◽  
Structure Phase

Mudstone is a natural type of geological material, which has different ways of mechanical response between natural state and dry-wet cycles. According to the complex damage theory of geological materials, rock masses can be considered as a composite material consisting of the structure phase and damage phase. The essence of the damage of rock masses is a damage evolution process, during which the deformation energy of the structure phase converts into dissipation energy of the damage phase, and the energy dissipation from phase transformation promotes the structure phase to change into the damage phase. In this study, a customized model test container and a novel test method are applied to study the decay rate of mudstone under different temperatures and over multiple dry-wet cycles. The decay rate and the damage variable are connected with each other and applied to the damage constitutive equation based on the energy principle to set up the damage evolution equation under the coupled action of dry-wet cycles and loads. Comparison of the proposed model with test results in a literature identifies the rationality of the established model and properly reflects the damage evolution of mudstone.

Application of Damage Model in Stability Analysis of ShuangjiangKou Underground Caverns

2011 ◽  
Vol 462-463 ◽  
pp. 1391-1396
Author(s):  
Lu Xiang ◽  
Wei Shen Zhu ◽  
Qing Song Ma ◽  
Kui Zhou
Keyword(s):  
Constitutive Model ◽  
Evolution Equation ◽  
Damage Evolution ◽  
Jointed Rock ◽  
Rock Masses ◽  
Damage Evolution Equation ◽  
Jointed Rock Masses ◽  
Underground Caverns ◽  
Damage Constitutive Model ◽  
The Stability

A damage constitutive model was established to evaluate the stability of jointed rock masses around the underground caverns of Shuangjiangkou Hydropower Station. In this model, a second-order damage tensor was formulated to describe the initial geometric imperfection of jointed rock masses. A failure criterion for crack coalescence and a damage evolution equation were proposed by considering the secondary cracks induced by excavations according to the fracture mechanics principles. A subprogram under the framework of FLAC-3D was developed for the damage constitutive model and the damage evolution equation. The model and program were then applied in the stability assessment for the Shuangjiangkou underground cavern group.

Study on mechanical properties and damage evolution of carbonaceous shale under triaxial compression with acoustic emission

2021 ◽  
pp. 105678952199119
Author(s):  
Kai Yang ◽  
Qixiang Yan ◽  
Chuan Zhang ◽  
Wang Wu ◽  
Fei Wan
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Damage Evolution ◽  
Damage Assessment ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Damage Variable ◽  
Natural State ◽  
Carbonaceous Shale

To explore the mechanical properties and damage evolution characteristics of carbonaceous shale with different confining pressures and water-bearing conditions, triaxial compression tests accompanied by simultaneous acoustic emission (AE) monitoring were conducted on carbonaceous shale rock specimens. The AE characteristics of carbonaceous shale were investigated, a damage assessment method based on Shannon entropy of AE was further proposed. The results suggest that the mechanical properties of carbonaceous shale intensify with increasing confining pressure and degrade with increasing water content. Moisture in rocks does not only weaken the cohesion but also reduce the internal friction angle of carbonaceous shale. It is observed that AE activities mainly occur in the post-peak stage and the strong AE activities of saturated carbonaceous shale specimens appear at a lower normalized stress level than that of natural-state specimens. The maximum AE counts and AE energy increase with water content while decrease with confining pressure. Both confining pressure and water content induce changes in the proportions of AE dominant frequency bands, but the changes caused by confining pressure are more significant than those caused by water content. The results also indicate that AE entropy can serve as an applicable index for rock damage assessment. The damage evolution process of carbonaceous shale can be divided into two main stages, including the stable damage development stage and the damage acceleration stage. The damage variable increases slowly accompanied by a few AE activities at the first stage, which is followed by a rapid growth along with intense acoustic emission activities at the damage acceleration stage. Moreover, there is a sharp rise in the damage evolution curve for the natural-state specimen at the damage acceleration stage, while the damage variable develops slowly for the saturated-state specimen.

A path for evaluating the mechanical response of rock masses based on deep mining-induced microseismic data: A case study

2021 ◽  
Vol 115 ◽  
pp. 104025
Author(s):  
Yong Zhao ◽  
Tianhong Yang ◽  
Honglei Liu ◽  
Shuhong Wang ◽  
Penghai Zhang ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Rock Masses ◽  
Deep Mining ◽  
Microseismic Data

Numerical modelling of the crack-pore interaction and damage evolution behaviour of rocklike materials with pre-existing cracks and pores

2020 ◽  
pp. 105678952098387
Author(s):  
PLP Wasantha ◽  
D Bing ◽  
SQ Yang ◽  
T Xu
Keyword(s):  
Principal Stress ◽  
Damage Evolution ◽  
Shear Failure ◽  
Mechanical Response ◽  
Distribution Patterns ◽  
Stress Distributions ◽  
Compressive Stresses ◽  
Major Principal Stress ◽  
The Right ◽  
Macroscopic Failure

The combined effect of pre-existing cracks and pores on the damage evolution behaviour and mechanical properties of rocklike materials under uniaxial compression was numerically studied. Simulations of cracks and pores alone showed that increasing crack length and pore diameter decrease uniaxial compressive strength (UCS) and elastic modulus. Subsequent simulations considered two types of combinations of pre-existing cracks and pores – two cracks either side of a centric pore, and two pores either side of a centric crack – and the distance between cracks and pores was changed. In the case of two cracks at either side of the pore, UCS increased only slightly when the distance between the cracks and pore was increased. This was attributed to the more profound effect of the presence of the pore on UCS, and was confirmed by the progressive crack development characteristics and the major principal stress distribution patterns, which showed that the cracks initiated from the tips of the two pre-existing cracks made little or no contribution to the ultimate macroscopic failure. In contrast, models with two pores at either side of a centric crack showed a marked dependency of UCS on the distance between the pores and the crack. Cracks propagating from pre-existing pores made a greater contribution to the ultimate macroscopic failure when the pores were close to the centric crack and the effect gradually diminished with increasing space between pre-existing pores and the centric crack. Major principal stress distributions showed an asymmetric mobilisation of compressive stresses at the right and left sides of the two pores, favouring macroscopic shear failure when they were close to the centric crack which had led to a lower UCS. Overall, this study presents some critical insights into crack-pore interaction behaviour and the resulting mechanical response of rocklike materials to assist with the design of rock structures.

Damage Analysis of Concrete Subjected to Freeze-Thaw Cycles and Chloride Ion Erosion

2011 ◽  
Vol 488-489 ◽  
pp. 464-467
Author(s):  
Ji Ze Mao ◽  
Zhi Yuan Zhang ◽  
Zong Min Liu ◽  
Chao Sun
Keyword(s):  
Constitutive Equation ◽  
Evolution Equation ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Chloride Ion ◽  
Offshore Structures ◽  
Damage Evolution Equation ◽  
Freeze Thaw ◽  
Concrete Materials ◽  
Ion Erosion

With the development of damage mechanics, many researchers have used it to analyze the constitutive equation of concrete. Since the special environment in the cold marine regions, the offshore structures are common to subject to the comprehensive effects of freeze-thaw action and chloride erosion. This might cause concrete materials degradation and reduce the mechanical performance of concrete seriously. In this paper, based on the analysis and mechanical experiments of concrete materials under the comprehensive effects of freeze-thaw action and chloride ion erosion, the damage evolution equation of concrete elastic modulus along with the freeze-thaw cycles and chloride ion contents was established. The effects of chloride ion were investigated during the process of concrete degradation. According to the damage evolution equation, a new constitutive equation of concrete under freeze-thaw action and chloride erosion was established. And then, by means of the element simulation analysis of concrete beams when subjected to the comprehensive actions, the feasibility and applicability of the equation was examined and discussed. In this equation, both the freeze-thaw action and chloride ion erosion were considered together. It will be more suitable for analyzing the durability of concrete structures in the real cold marine regions. It will also provide some references for concrete constitutive theory.

Study On the Damage Evolution Equation of Rockburst

2008 ◽  
Vol 33-37 ◽  
pp. 663-668
Author(s):  
Quan Sheng Liu ◽  
Bin Liu ◽  
Wei Gao
Keyword(s):  
Energy Dissipation ◽  
Evolution Equation ◽  
Damage Evolution ◽  
Minimum Energy ◽  
Strength Criterion ◽  
Internal Variable ◽  
Total Strength ◽  
Damage Evolution Equation ◽  
Traditional Research ◽  
Minimum Energy Dissipation

This paper introduces the principle of minimum energy dissipation and its general procedures to establish development equation of internal variable. With the accepted viewpoint that the damage is only mechanics of energy dissipation during the rockburst and utilizing the total strength criterion based on released strain energy, the general damage evolution equation is deduced. Compared with the traditional research method of damage evolution equation, this method has universal and objective characteristics.

Numerical simulation of ductile fracture in polyethylene pipe with continuum damage mechanics and Gurson-Tvergaard-Needleman damage models

2019 ◽  
Vol 233 (12) ◽  
pp. 2455-2468
Author(s):  
Yi Zhang ◽  
P-Y Ben Jar ◽  
Shifeng Xue ◽  
Lin Li
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Constitutive Equations ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Experimental Testing ◽  
Monotonic Loading ◽  
Test Method ◽  
Strain Level ◽  
Element Simulation

A phenomenon-based hybrid approach of experimental testing and finite element simulations is used to describe the fracture behavior of pipe-grade polyethylene. The experimental testing adopts a modified D-split test method to stretch the pipe ring (notched pipe ring) specimens that have symmetric, double-edged flat notches along the pipe direction. Two series of experimental testing were conducted: (1) monotonic loading till fracture and (2) monotonic loading to a predefined strain level, keeping constant displacement for a period of time, and then unloaded. Crosshead speeds of 0.01, 1, and 100 mm/min were used in both series of tests. Likewise, two series of finite element simulation were conducted to establish the constitutive equations, either with or without considering damage evolution during the deformation process. The constitutive equation without the consideration of damage was established using results from the first series of experimental testing, and that with damage was inspired from the second series which showed the decrease in unloading modulus with the increase of crosshead speed or the predefined strain level. The results show that with the consideration of damage evolution, the constitutive equations enable the finite element simulation to determine the whole stress–strain relationship during both necking and fracture processes.

scholarly journals A finite dissipative theory of temporary interfibrillar bridges in the extracellular matrix of ligaments and tendons

2008 ◽  
Vol 6 (39) ◽  
pp. 909-924 ◽  
Author(s):  
P. Ciarletta ◽  
M. Ben Amar
Keyword(s):  
Extracellular Matrix ◽  
Damage Evolution ◽  
Structural Integrity ◽  
Mechanical Response ◽  
Collagen Type I ◽  
State Theory ◽  
Ground Substance ◽  
Type I ◽  
Dissipative Effects ◽  
Rate Dependent

The structural integrity and the biomechanical characteristics of ligaments and tendons result from the interactions between collagenous and non-collagenous proteins (e.g. proteoglycans, PGs) in the extracellular matrix. In this paper, a dissipative theory of temporary interfibrillar bridges in the anisotropic network of collagen type I, embedded in a ground substance, is derived. The glycosaminoglycan chains of decorin are assumed to mediate interactions between fibrils, behaving as viscous structures that transmit deformations outside the collagen molecules. This approach takes into account the dissipative effects of the unfolding preceding fibrillar elongation, together with the slippage of entire fibrils and the strain-rate-dependent damage evolution of the interfibrillar bridges. Thermodynamic consistency is used to derive the constitutive equations, and the transition state theory is applied to model the rearranging properties of the interfibrillar bridges. The constitutive theory is applied to reproduce the hysteretic spectrum of the tissues, demonstrating how PGs determine damage evolution, softening and non-recoverable strains in their cyclic mechanical response. The theoretical predictions are compared with the experimental response of ligaments and tendons from referenced studies. The relevance of the proposed model in mechanobiology research is discussed, together with several applications from medical practice to bioengineering science.

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