scholarly journals Modified Nishihara Rheological Model considering the Effect of Thermal-Mechanical Coupling and Its Experimental Verification

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Xingang Wang ◽  
Qiangbing Huang ◽  
Baoqin Lian ◽  
Nina Liu ◽  
Jun Zhang
Keyword(s):  
Rheological Model ◽  
Thermal Damage ◽  
Effect Of Temperature ◽  
Creep Process ◽  
Theoretical Formula ◽  
Mechanical Coupling ◽  
Good Ability ◽  
Rock Creep ◽  
Creep Models ◽  
Improved Model

The effect of temperature and pressure, which play important roles in the mechanical properties of rocks during deep energy exploitation, has not been sufficiently studied in the previous rock creep models. In order to investigate thermal effect in creep models, a modified Nishihara rheological model, taking into account the coupled effect of thermal damage and stress, was proposed by combining the theoretical formula for thermal damage of rocks with the modified Nishihara model. The improved model introduces a nonlinear viscous dashpot, which can accurately describe the accelerated rheological phase of rocks. To verify the proposed model, a triaxial rheological experiment was conducted on sandstone subjected to thermal damage (600°C). In addition, the stress-strain curves within whole creep process of the rheological experiment were analyzed. Furthermore, the theoretical curves of the modified Nishihara rheological model were compared with the experimental results. Results showed that the theoretical curves relatively agree well with the experimental data, suggesting that the proposed new model is more preferred to describing the rheological curve of sandstone subjected to thermal damage at different rheological stages, in particular, it is capable of depicting the accelerated rheological stage of the sandstone, providing a good ability to describe the creep behavior of rocks under thermal-mechanical coupling.

scholarly journals Creep Properties and Constitutive Model of Salt Rock

2021 ◽  
Vol 2021 ◽  
pp. 1-29
Author(s):  
Qiang Zhang ◽  
Zhanping Song ◽  
Junbao Wang ◽  
Yuwei Zhang ◽  
Tong Wang
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Effect Of Temperature ◽  
Creep Process ◽  
Underground Storage ◽  
Self Healing ◽  
Salt Rock ◽  
Creep Properties ◽  
Term Operation ◽  
Rock Creep

Due to the advantages of low porosity, low permeability, high ductility, and excellent capacities for creep and damage self-healing, salt rock is internationally considered as the ideal medium for underground storage of energy and disposal of radioactive waste. As one of the most important mechanical properties of salt rock, creep properties are closely related to the long-term operation stability and safety of salt rock underground storage cavern. A comprehensive review on the creep properties and constitutive model of salt rock is put forward in this paper. The opinions and suggestions on the research priority and direction of salt rock's mechanical properties in the future are put forward: (1) permeability variation of salt rock under the coupling effect of temperature and stress; (2) damage mechanism and evolution process under the effect of creep-fatigue interaction and low frequency cyclic loading; (3) microdeformation mechanisms of salt rock and the relationship between microstructure variations and macrocreep behavior during creep process; (4) the establishment of the creep damage constitutive model with simple form, less parameters, easy application, and considering the damage self-healing ability of salt rock simultaneously.

scholarly journals Research on Rock Creep Characteristics Based on the Fractional Calculus Meshless Method

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
Gang Peng ◽  
Zhanqing Chen ◽  
Jiarui Chen
Keyword(s):  
Fractional Calculus ◽  
Meshless Method ◽  
Test System ◽  
Constitutive Relationship ◽  
Creep Process ◽  
Kelvin Model ◽  
Related Data ◽  
Model Based ◽  
Rock Creep ◽  
Generalized Kelvin Model

The application of fractional calculus in the rheological problems has been widely accepted. In this study, the constitutive relationship of the generalized Kelvin model based on fractional calculus was studied, and the meshless method was introduced so as to derive a new meshless algorithm formula based on the fractional calculus of the generalized Kelvin model. By using the MTS815.02 hydraulic servo rock mechanics test system, the creep test of mudstones is carried out, and the related data of the creep process were obtained. Based on the generalized Kelvin model of fractional calculus, the related creep parameters of the argillaceous sandstone under compression were fitted. The results showed that the solution of the generalized Kelvin model based on fractional calculus was greatly consistent with the numerical method solution. Meanwhile, the meshless algorithm based on fractional calculus had a favorable stability and accuracy.

scholarly journals Durability analysis of underground structures based on various creep models of the enclosing salt rock massif

2020 ◽  
Vol 201 ◽  
pp. 01007
Author(s):  
Mikhail Zhuravkov ◽  
Sergey Hvesenya ◽  
Siarhei Lapatsin
Keyword(s):  
Underground Structure ◽  
Primary Creep ◽  
Rock Massif ◽  
Initial Time ◽  
Creep Process ◽  
Secondary Creep ◽  
Salt Rock ◽  
Mine Shaft ◽  
Durability Analysis ◽  
Creep Models

The results of the durability analysis of a complex underground structure and surrounding multilayered rock massif are presented. The research is conducted based on an applied stress-strain state problem for a salt rock massif in the vicinity of an underground cavity of a large cross-section which is in conjunction with a mine shaft. The main aim of the research is to perform a comparative analysis of various mathematical models of the creep process. The problem is solved using finite element method to achieve this goal. Regularity in the development of deformation processes of the enclosing rock massif is established as a result of the study. According to this regularity, both primary creep and primary-secondary creep models show that the main increase of creep deformations occurs during a short initial time period after which creep strain rate decreases sharply.

scholarly journals Nonlinear Viscoelastic–Plastic Creep Model Based on Coal Multistage Creep Tests and Experimental Validation

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3468 ◽  
Author(s):  
Junxiang Zhang ◽  
Bo Li ◽  
Conghui Zhang ◽  
Peng Li
Keyword(s):  
Creep Behavior ◽  
Physical Property ◽  
Creep Model ◽  
Creep Process ◽  
Creep Tests ◽  
Model Based ◽  
Nonlinear Viscoelastic ◽  
Improved Model ◽  
And Control ◽  
Plastic Creep

The development of fractures, which determine the complexity of coal creep characteristics, is the main physical property of coal relative to other rocks. This study conducted a series of multistage creep tests to investigate the creep behavior of coal under different stress levels. A negative elastic modulus and a non-Newtonian component were introduced into the classical Nishihara model based on the theoretical analysis of the experimental results to propose a nonlinear viscoelastic–plastic creep model for describing the non-decay creep behavior of coal. The validity of the model was verified by experimental data. The results show that this improved model can preferably exhibit decelerating, steady state, and accelerating creep behavior during the non-decay creep process. The fitting accuracy of the improved model was significantly higher than that of the classical Nishihara model. Given that acceleration creep is a critical stage in predicting the instability and failure of coal, its successful description using this improved model is crucial for the prevention and control of coal dynamic disasters.

scholarly journals Application of Multiphysics Coupling FEM on Open Wellbore Shrinkage and Casing Remaining Strength in an Incomplete Borehole in Deep Salt Formation

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Hua Tong ◽  
Daqiang Guo ◽  
Xiaohua Zhu
Keyword(s):  
Three Dimensional ◽  
Effect Of Temperature ◽  
Salt Rock ◽  
Salt Formation ◽  
Defect Level ◽  
Rock Creep ◽  
Multiphysics Coupling ◽  
Casing Strength ◽  
New Perspective ◽  
Harsh Condition

Drilling and completing wells in deep salt stratum are technically challenging and costing, as when serving in an incomplete borehole in deep salt formation, well casing runs a high risk of collapse. To quantitatively calculate casing remaining strength under this harsh condition, a three-dimensional mechanical model is developed; then a computational model coupled with interbed salt rock-defective cement-casing and HPHT (high pressure and high temperature) is established and analyzed using multiphysics coupling FEM (finite element method); furthermore, open wellbore shrinkage and casing remaining strength under varying differential conditions in deep salt formation are discussed. The result demonstrates that the most serious shrinkage occurs at the middle of salt rock, and the combination action of salt rock creep, cement defect, and HPHT substantially lessens casing remaining strength; meanwhile, cement defect level should be taken into consideration when designing casing strength in deep salt formation, and apart from the consideration of temperature on casing the effect of temperature on cement properties also cannot be ignored. This study not only provides a theoretical basis for revealing the failure mechanism of well casing in deep complicated salt formation, but also acts as a new perspective of novel engineering applications of the multiphysics coupling FEM.

Experimental Research on the Thermal Damage of Concrete

2013 ◽  
Vol 351-352 ◽  
pp. 460-466
Author(s):  
Chao Chen ◽  
Ying She Luo ◽  
Song Hua Tang ◽  
Xuan Zhang
Keyword(s):  
Damage Evolution ◽  
Thermal Damage ◽  
Damage Model ◽  
Effect Of Temperature ◽  
Compression Tests ◽  
Thermal Compression ◽  
Relevant Reference ◽  
Different Temperatures ◽  
The Relationship ◽  
Fire Design

In order to investigate the effect of temperature (from normal temperature to 850°C) coursed by fire on the strength damage of concrete, thermal compression tests for concrete specimens named C35 have been performed under different temperature conditions. Emphasis is laid on the relationship between temperature and thermal damage strength; and the relevant formula is proposed in this paper. The regularity and mechanism of thermal damage evolution in concrete on strength under high temperature are analyzed. Combined the result of tests with the residual strength thermal damage model, we obtain the specific damage variable value D under different temperatures. Finally, we compare the fitting formula curve to relevant reference; there are some important conclusions which can be partly applied to fire design of concrete structure.

scholarly journals Study on the Damage Evolution Process and Fractal of Quartz-Filled Shale under Thermal-Mechanical Coupling

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zhonghu Wu ◽  
Huailei Song ◽  
Liping Li ◽  
Zongqing Zhou ◽  
Yujun Zuo ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Critical Temperature ◽  
Failure Mode ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Thermal Damage ◽  
Failure Modes ◽  
Factors Affecting ◽  
Mechanical Coupling ◽  
Theory Of Damage

Filling of brittle minerals such as quartz is one of the main factors affecting the initiation and propagation of reservoir fractures in shale fracturing, in order to explore the failure mode and thermal damage characteristics of quartz-filled shale under thermal-mechanical coupling. Combining the theory of damage mechanics and thermoelasticity, RFPA2D-Thermal is used to establish a numerical model that can reflect the damage evolution of shale under thermal-solid coupling, and the compression test under thermal-mechanical coupling is performed. The test results show that during the temperature loading process, there is a temperature critical value between 60°C and 75°C. When the temperature is less than the critical temperature, the test piece unit does not appear obvious damage. When the temperature is greater than the critical temperature, the specimen unit will experience obvious thermal damage, and the higher the temperature, the more serious the cracking. Under the thermal-mechanical coupling of shale, the tensile strength and elastic modulus of shale show a decreasing trend with the increase of temperature. The failure modes of shale under thermal-solid coupling can be roughly divided into three categories: “V”-shaped failure (30°C, 45°C, and 75°C), “M”-shaped failure (60°C), and inverted “λ”-shaped failure (90°C). The larger the fractal dimension, the more complex the failure mode of the specimen. The maximum fractal dimension is 1.262 when the temperature is 60°C, and the corresponding failure mode is the most complex “M” shape. The fractal dimension is between 1.071 and 1.189, and the corresponding failure mode is “V” shape. The fractal dimension is 1.231, and the corresponding failure mode is inverted “λ” shape.

Experimental Investigations of Thermal Damage for Rocks

2006 ◽  
Vol 324-325 ◽  
pp. 1213-1216 ◽  
Author(s):  
Dao Ying Xi ◽  
Song Lin Xu ◽  
Yue Zhan Tao ◽  
Ting Li
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Internal Friction ◽  
Thermal Damage ◽  
Mechanical Damage ◽  
Experimental Techniques ◽  
Effect Of Temperature ◽  
Experimental Investigations ◽  
Kaiser Effect ◽  
Temperature Range

As the rocks were composed of many minerals, high temperature might lead to the non-consistent deformation among these components. That was the mechanism of thermal damage. In the present paper, the thermal damage of rocks was investigated under a much broader temperature range until minerals phase transition. The experimental techniques of AE and the internal friction were proven to be the most useful tools to reveal the thermal damage. The affection of thermal damage to Kaiser Effect of temperature and the coupled effects of thermal and mechanical damage were also discussed.

Study on the Creep Parameters of Salt Rock Constitutive Function

2014 ◽  
Vol 1079-1080 ◽  
pp. 166-169 ◽  
Author(s):  
Hai Peng Zhang ◽  
Yi Jin ◽  
Long Ma
Keyword(s):  
Constitutive Model ◽  
Creep Test ◽  
Constitutive Equations ◽  
Determination Method ◽  
Salt Rock ◽  
Constitutive Function ◽  
Rock Creep ◽  
Creep Models ◽  
Creep Constitutive Model

Salt rock is a kind ofthe most suitablemedium for energy storages, because of its strongcreep behavior. "Burgers" and "Norton" is the two classic creep models. This paper starts from the establishment of creep constitutive model to obtain the determination method of creep constitutive parameters.Finally, it takes Nanjing salt rock creep test (2003) as an example to solve the parameters in Burgers and Norton constitutive equations.

Numerical Analysis for Thermal-Chemical-Stress Coupling in Deep Rock Creep Properties

2013 ◽  
Vol 561 ◽  
pp. 657-662
Author(s):  
Yan Chun Wang ◽  
Yuan Li ◽  
Jian Guang Li
Keyword(s):  
Ph Value ◽  
Coupling Effect ◽  
High Stress ◽  
Soft Rock ◽  
Effect Of Temperature ◽  
Creep Equation ◽  
Creep Properties ◽  
Rock Creep ◽  
Deep Rock ◽  
Rock Tunnel

The control equations for analyzing coupled thermal chemical-mechanical phenomena of deep rocks are established. Using creep equation by experimental data, 3D numerical simulation for creep properties of deep soft tunnel under coupling effect of temperature field, chemical field and stress field are conducted by ANSYS, and different effects of these fields on deep soft rock tunnel creep properties are analyzed, whats more time-creep curves of different temperature, pH value and stress deviation of the mid-point of the top of tunnel are obtained. Effect of these three fields on creep characteristics of deep soft rock cant be ignored. Under deep complex environment, high-stress is main factor of tunnel creep; creep increasing with temperature increasing. From simulation results, we get whether acidic environment or alkaline environment causes significantly stronger corrosive effect on the rock mass than the neutral environment, and increases its creep.

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