Improved nonlinear Burgers shear creep model based on the time-dependent shear strength for rock

2020 ◽  
Vol 79 (6) ◽  
Author(s):  
Hang Lin ◽  
Xing Zhang ◽  
Rihong Cao ◽  
Zhijie Wen
Keyword(s):  
Shear Strength ◽  
Time Dependent ◽  
Creep Model ◽  
Shear Creep ◽  
Model Based

scholarly journals Improved Nonlinear Nishihara Shear Creep Model with Variable Parameters for Rock-Like Materials

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Hang Lin ◽  
Xing Zhang ◽  
Yixian Wang ◽  
Rui Yong ◽  
Xiang Fan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Creep Test ◽  
Creep Property ◽  
Variable Parameter ◽  
Nonlinear Function ◽  
Creep Model ◽  
Creep Process ◽  
Shear Creep

Creep property is an important mechanical property of rocks. Given the complexity of rock masses, mechanical parameters change with time in the creep process. In this work, a nonlinear function for describing the time-dependent change of parameters was introduced and an improved variable-parameter nonlinear Nishihara shear creep model of rocks was established. By creating rock-like materials, the mechanical properties of rocks under the shear creep test condition were studied, and the deformation characteristics and long-term shear strength of rocks during creep were analyzed. The material parameters of the model were identified using the creep test results. Comparison of the model’s calculated values and experimental data indicated that the model can describe the creep characteristics of rocks well, thus proving the correctness and rationality of the improved model. During shear creep, the mechanical properties of rocks have an aging effect and show hardening characteristics under low shear stress. Furthermore, according to the fact that Gk of the nonlinear model can characterize the creep deformation resistance, a method to determine the long-term shear strength is proposed.

Pressuremeter Testing of Normally Consolidated Clays—The Effects of Varying Test Technique

1986 ◽  
Vol 2 (1) ◽  
pp. 125-132
Author(s):  
W. F. Anderson ◽  
I. C. Pyrah ◽  
F. Haji-Ali
Keyword(s):  
Test Methods ◽  
Time Dependent ◽  
Clay Soils ◽  
Shear Creep ◽  
Test Technique ◽  
Pressuremeter Test ◽  
Numerical Predictions ◽  
Cylindrical Cavities ◽  
Undrained Conditions ◽  
Insight Into

AbstractAlthough BS 5930:1981 describes both Menard and self-boring pressuremeter tests, little guidance is given on test methods. A number of techniques, both stress controlled and strain controlled, have been used and it has been shown that for clays the test technique has a significant influence on the derived strength and modulus parameters.When a pressuremeter test is carried out in a clay, it is assumed that shearing occurs under undrained conditions. However, in addition to immediate shear strain, some creep and local consolidation will occur in the soil around the expanding borehole. These two phenomena are time-dependent and variations in test technique will affect the test data and hence the derived strength and modulus values.To obtain a better understanding of these effects, pressuremeter tests have been studied both experimentally and numerically. Experimentally, pressuremeter tests have been simulated by expanding cylindrical cavities in samples of three clays prepared with known stress history and the results compared with numerical predictions where the effects of immediate shear, creep and consolidation can be separated. The experimental results compare well with the numerical predictions.This has given a new insight into the behaviour of clay soils during pressuremeter tests. The results indicate that any simple standardization of pressuremeter test technique should be approached with caution.

scholarly journals Shear Strength Deterioration Effect and Slope Reliability Analysis Under Extreme Ice-snow Melting Conditions 

2021 ◽  
Author(s):  
Tongqiang Xiong ◽  
Jianlin Li ◽  
Lehua Wang ◽  
Huafeng Deng ◽  
Xiaoliang Xu
Keyword(s):  
Shear Strength ◽  
Friction Angle ◽  
Soil Samples ◽  
Creep Model ◽  
Shear Strength Parameters ◽  
Snow Melting ◽  
Strength Deterioration ◽  
Melting Cycle ◽  
Deformation Stability ◽  
Deterioration Effect

Abstract Extreme ice-snow melting in winter affects the infiltration process of snow water on the slope surface significantly, and plays an important role in the deformation stability of landslide. The fluctuation trend of slope stability under ice-snow melting is the same as that of soil volume water content. The deterioration effect of mechanical parameters will directly affect the deformation stability of bank slope. Based on this, the ice-snow melting cycle model test of slope soil was designed and carried out. The results are showed.(1) We were established an ice-snow melting model based on physical process. In the process of ice-snow melting, the soil cohesion and internal friction Angle have obvious deterioration effect .The deterioration of cohesion is obviously larger than that of internal friction Angle. In the early part of the ice-snow melting cycle, the deterioration of shear strength parameters is very obvious. Among them, the deterioration of shear strength parameters caused by the first four ice-snow melting cycles accounted for about 70% of the total deterioration. After the G2/T2 ice-snow melting cycle, the degree of phase deterioration gradually decreases. The deterioration trend of shear parameters of soil samples gradually tends to be gentle. (2) In the ice-snow melting cycle, the inside of the soil samples have micro-cracks, fissures repeatedly opened and closed, gradually developed and converged. The result is that the soil samples change from dense state to loose state where internal cracks develop. The internal damage of soil samples is the fundamental reason for the gradual deterioration of shear strength.（3）We are keep to the relative independence principle of creep model and unsaturated seepage equation. We are studied and improved the parameter solving method of creep model. The modified model is reasonable and effective. The creep trend and main characteristics of the unsaturated soil can be described well. Shear strength deterioration effect and slope reliability analysis under extreme ice-snow melting conditions .It has important reference significance to the protection of extreme snow and ice disaster on the bank slope.

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 New Maxwell Creep Model Based on Fractional and Elastic-Plastic Elements

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Hao Tang ◽  
Dongpo Wang ◽  
Zhao Duan
Keyword(s):  
Rock Salt ◽  
Damage Mechanics ◽  
Rheological Behaviour ◽  
Creep Model ◽  
Creep Data ◽  
Creep Equation ◽  
New Model ◽  
Elastic Plastic ◽  
Simulation Performance ◽  
Model Based

Creep models are mainly used to describe the rheological behaviour of geotechnical materials. An important research focus for studying creep in geotechnical materials is the development of a model with few parameters and good simulation performance. Hence, in this study, by replacing the Newtonian dashpot and spring in the classical Maxwell model with fractional and elastic-plastic elements, a new Maxwell creep model based on fractional derivatives and continuum damage mechanics was developed. One- and three-dimensional (1D/3D) creep equations of the new Maxwell creep model were derived. The 1D creep equation of the new model was used to fit existing creep data of rock salt, and the 3D creep equation was used to fit the creep data of remolded loess. The model curves matched the creep data very well, showing considerably higher accuracy than other models. Furthermore, a sensitivity study was carried out, showing the effects of the fractional derivative order β and exponent α on the creep strain of rock salt. This new model is simple with few parameters and can effectively simulate the complete creep behaviour of geotechnical materials.

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