scholarly journals A Fractional Creep Constitutive Model for Frozen Soil in Consideration of the Strengthening and Weakening Effects

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Feng Hou ◽  
Quanming Li ◽  
Enlong Liu ◽  
Cheng Zhou ◽  
Mengke Liao ◽  
...  
Keyword(s):  
Shear Stress ◽  
Constitutive Model ◽  
Test Specimen ◽  
Confining Pressure ◽  
Frozen Soil ◽  
Strengthening Effect ◽  
Term Strength ◽  
Test Results ◽  
Creep Constitutive Model

The triaxial creep tests of frozen silty clay mixed with sands were performed under different pressures, and the test results demonstrated that, under the low confining pressure, when the shear stress is lower than the long-term strength, the test specimen exhibits an attenuation creep because the strengthening effect is greater than the weakening effect. When the shear stress is higher than the long-term strength, the test specimen exhibits a nonattenuation creep due to the level of the strengthening and weakening effects change in different stages. As the confining pressure increases, the test specimens only exhibit an attenuation creep because of the enhancing strengthening effect. Both the hardening parameter and the damage variable were introduced to describe the strengthening and weakening effects, respectively, and a new creep constitutive model for frozen soil considering these effects was put forward based on the theory of elastoviscoplastic and the fractional derivative. Finally, the model parameters were analyzed and their determination method was also provided to reveal the trend of parameters according to the triaxial test results. The calculated results of the constitutive model show that the proposed model can describe the whole creep process of frozen soil well.

Time-dependent displacement behaviour of model adfreeze and grouted piles in saline frozen soils

1994 ◽  
Vol 31 (3) ◽  
pp. 395-406 ◽  
Author(s):  
K.W. Biggar ◽  
D.C. Sego
Keyword(s):  
Field Studies ◽  
Frozen Soil ◽  
Silty Sand ◽  
Time Dependent ◽  
Test Results ◽  
Model Pile ◽  
Laboratory Test Results ◽  
Load Carrying ◽  
Pile Deformation

The findings of a laboratory study on the time-dependent displacement of model piles in saline frozen soil are reported. The short-term time-dependent pile deformation in ice-poor saline silty sand was best described using a simple power law of time, whereas the long-term time-dependent deformations were best described using a flow law formulation similar to that used to describe the long-term time-dependent deformation of ice or ice-rich permafrost. The use of cementitious grout as a backfill resulted in doubling of the pile load carrying capacity for a given displacement rate. The laboratory test results compare well with other laboratory and field studies. Key words : frozen soil, saline, model pile, time-dependent deformation, sand backfill, grout.

scholarly journals Applicability of single sample method to test strength parameters of sandstone

2021 ◽  
Vol 2076 (1) ◽  
pp. 012019
Author(s):  
Shaoan Li ◽  
Wenxia Li ◽  
Yunlei Hu ◽  
Tao Zhang ◽  
Xiangchao Shi
Keyword(s):  
Yield Point ◽  
Confining Pressure ◽  
Single Sample ◽  
Term Strength ◽  
Strength Parameters ◽  
Loading Tests ◽  
Sample Method ◽  
Compressive Tests ◽  
Multistage Loading

Abstract The single sample method allows the mechanical parameters of rocks to be obtained with very few rock samples; however, the method has not been widely used. This is mainly because the yield point of the single sample method is more difficult to control than the conventional triaxial compressive test and the effect of the different control methods on the measured data is not well understood. The single sample method obtains the strength parameters of the rock by loading a single rock sample with multiple stages of confining pressure. Multistage loading tests are divided into peak strength control and long-term strength control according to yield point control. In this study, multistage loading tests of sandstone were carried out to obtain strength parameters using long-term strength control. The results show that sandstones undergo seriously brittle damage in conventional triaxial compressive tests. Although the sandstones have been rigorously selected, they still vary considerably, and long-term strength points are more difficult to control. The error of strength parameters of sandstone obtained using the single sample method may exceed 20% compared to those obtained by conventional triaxial compressive tests. So this method must be used with caution for sandstones.

A New Creep Constitutive Model for Eutectic Solder Alloy

2002 ◽  
Vol 124 (2) ◽  
pp. 85-90 ◽  
Author(s):  
X. Q. Shi ◽  
Z. P. Wang ◽  
W. Zhou ◽  
H. L. J. Pang ◽  
Q. J. Yang
Keyword(s):  
Constitutive Model ◽  
Testing Temperature ◽  
Creep Model ◽  
Temperature Dependent ◽  
Creep Tests ◽  
Creep Flow ◽  
Reliability Of Solder Joints ◽  
Power Law Creep ◽  
Creep Constitutive Model

In this study, a large number of creep tests were carried out to study the effect of stress level and testing temperature on the creep behavior of 63 Sn/37Pb solder in a systematic manner. Based on the dislocation controlled creep mechanism and Gibbs’ free-energy theory, a new creep constitutive model was proposed. The model was found to describe accurately the creep flow of the solder and to be capable of explaining the issues of stress and temperature dependent stress exponent and activation energy in the Arrhenius power-law creep model. Furthermore, the model was employed to predict accurately the long-term reliability of solder joints in a PBGA assembly.

Experimental Study on Direct Shear Creep Characteristics and Long-Term Strength of Red Layer Sliding Zone Soil in Southern Hunan

2013 ◽  
Vol 842 ◽  
pp. 782-787 ◽  
Author(s):  
Feng Zhu ◽  
Zhong Yuan Duan ◽  
Zhen Yu Wu ◽  
Yu Qi Wu ◽  
Tian Long Li ◽  
...  
Keyword(s):  
Shear Stress ◽  
Term Strength ◽  
Direct Shear ◽  
Creep Tests ◽  
Shear Creep ◽  
Creep Characteristics ◽  
Southern Hunan ◽  
Sliding Soil ◽  
Sliding Zone

The creep characteristics of red layer sliding soil under the condition of different vertical loads and water contents were studied through a series of direct shear creep tests. Tests results showed that the water infiltrated to the sliding zone along the fissure of red layer sliding belt due to the crush of red layer sliding rock, leading to softening of sliding zone and acceleration of shear creep. When the shear stress reached the limit of long-term shear strength, sliding soil was broken suddenly with small vertical loads (50 kPa and 100kPa), while the sliding soil presented as a constant acceleration creep with enough vertical loads (200 kPa and 300 kPa). The inflection point in shear stress-shear displacement isochronous curve corresponded to the long-term strength of the soil.

scholarly journals Triaxial Creep Behavior of Red Sandstone in Freeze-Thaw Environments

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Yongjun Song ◽  
Yongxin Che ◽  
Leitao Zhang ◽  
Jianxi Ren ◽  
Shaojie Chen ◽  
...  
Keyword(s):  
Stress Level ◽  
Creep Deformation ◽  
Transverse Shear ◽  
Shear Plane ◽  
Confining Pressure ◽  
Term Strength ◽  
Red Sandstone ◽  
Freeze Thaw ◽  
Viscoelastic Strain

To investigate the time-dependent mechanical properties of rock masses in cold regions under the effects of freeze-thaw cycling and long-term loading, triaxial multilevel loading and unloading creep tests were performed on saturated red sandstone samples subjected to different numbers of freeze-thaw cycles. The effects of freeze-thaw cycles and confining pressure on the creep properties, long-term strength, and creep failure mode of the rock were analyzed. The effect of freeze-thaw cycles on the microstructure of the rock was analyzed using scanning electron microscopy. The results showed that as the number of freeze-thaw cycles increased, the rock particle boundaries became more distinct, and more pores formed. The effect of freeze-thaw cycles on the creep deformation of red sandstone was related to the loading stress level. At low stress levels, the rock viscoelastic strain increased gradually and almost linearly with an increasing number of freeze-thaw cycles; in contrast, at high stress levels, the rock viscoelastic strain increased nonlinearly. The viscoplastic strain increased almost linearly with increasing freeze-thaw cycles. The fourth loading stress level (70% σ c ) corresponded to the transition of the creep deformation of the red sandstone. When the confining pressure was low, a higher stress level caused the confining pressure to have a more significant effect on the creep strain. However, as the confining pressure continued to increase, the effect of the confining pressure on the creep strain eventually disappeared. The long-term strength of the red sandstone decreased approximately linearly with an increase in the number of freeze-thaw cycles. When the number of freeze-thaw cycles and the confining pressure were high, the rock samples formed a transverse shear plane and were more fragmented than those without a transverse shear plane. These results provide a reference for construction in rock mass engineering and long-term stability analysis in cold regions.

scholarly journals Study on the Creep Constitutive Model of a Sandstone Rock under the Water-Rock Interaction

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zuosen Luo ◽  
Zuoxiang Zhu ◽  
Jianlin Li ◽  
Lehua Wang ◽  
Qiao Jiang ◽  
...  
Keyword(s):  
Rock Mass ◽  
Constitutive Model ◽  
Nonlinear Creep ◽  
Rock Interaction ◽  
Long Term Stability ◽  
Sandstone Rock ◽  
Influence Of Water ◽  
Creep Constitutive Model ◽  
Water Rock Interaction

With the continuous construction of large-scale geotechnical engineering, more and more attention has been paid to the long-term stability of rock mass engineering, especially the problem of rock creep under the influence of water. Combined with the author’s previous research on the triaxial creep characteristics of sandstone under water-rock interaction, a nonlinear creep constitutive model was established to capture the degradation behavior of a sandstone rock due to cyclic wetting and drying of the reservoir water. Due to the limitations of the visco-elastoplastic model, a thorough modification was done to account the effect of the water-rock interaction on the mechanical degradation of the sandstone rock. Finally, the predicted results were proved to be in a good agreement with the experimental results. Moreover, the strong correlations between the predicted results and the experimental results show the effectiveness of the modified model to scrutinize the nonlinear creep behavior of sandstone rock. Relevant research results have important theoretical significance for the accurate prediction and effective control of the long-term stability of rock mass engineering under the influence of water-rock interaction.

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