Analysis of Creep Characteristics of Shallow Mined-Out Areas Roof under Low Stress Conditions

Under low stress conditions, when the load exerting on the mined-out areas roof is less than the rock long-term strength, the rock roof will generate some creep deformation. In order to prevent the roof of the mined-out areas suddenly collapse, and to ensure the operator and construction equipment above the mined-out areas safety, it is an important security technical problem to reveal the creep characteristics of the shallow mined-out areas roof. Taking the mined-out areas of Antaibao Surface Mine as background, considering the rheological properties of rock roof, and assuming the roof was a rectangular thick plate, the creep characteristics of mined-out areas roof were analysed by applying the thick plate theory and Kelvin creep model. The regression equation of the roof deflection increment over time was given, and the creep characteristics of the shallow mined-out areas roof were revealed also.

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Experimental and Analytical Study on Creep Characteristics of Box Section Bamboo-Steel Composite Columns under Long-Term Loading

Materials ◽

10.3390/ma14040983 ◽

2021 ◽

Vol 14 (4) ◽

pp. 983

Author(s):

Shixu Wu ◽

Keting Tong ◽

Jianmin Wang ◽

Yushun Li

Keyword(s):

Load Level ◽

Experimental Results ◽

Creep Model ◽

Composite Column ◽

Composite Columns ◽

Creep Coefficient ◽

Creep Characteristics ◽

Section Size ◽

Steel Composite

To expand the application of bamboo as a building material, a new type of box section composite column that combined bamboo and steel was considered in this paper. The creep characteristics of eight bamboo-steel composite columns with different parameters were tested to evaluate the effects of load level, section size and interface type under long-term loading. Then, the deformation development of the composite column under long-term loading was observed and analyzed. In addition, the creep-time relationship curve and the creep coefficient were created. Furthermore, the creep model of the composite column was proposed based on the relationship between the creep of the composite column and the creep of bamboo, and the calculated value of creep was compared with the experimental value. The experimental results showed that the creep development of the composite column was fast at first, and then became stable after about 90 days. The creep characteristics were mainly affected by long-term load level and section size. The creep coefficient was between 0.160 and 0.190. Moreover, the creep model proposed in this paper was applicable to predict the creep development of bamboo-steel composite columns. The calculation results were in good agreement with the experimental results.

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On the long-term strength of metals and the ideal-creep model

Doklady Physics ◽

10.1134/s1028335807070117 ◽

2007 ◽

Vol 52 (7) ◽

pp. 388-390

Author(s):

A. M. Kovrizhnykh

Keyword(s):

Creep Model ◽

Term Strength ◽

The Ideal

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A Review of Factors to Consider for Permanent Cordon Establishment and Maintenance

Agronomy ◽

10.3390/agronomy11091811 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1811

Author(s):

Patrick O’Brien ◽

Roberta De Bei ◽

Mark Sosnowski ◽

Cassandra Collins

Keyword(s):

Climate Change ◽

Heat Stress ◽

Vascular System ◽

Vascular Diseases ◽

Stress Conditions ◽

Normal Flow ◽

Training Techniques ◽

Long Term Consequences ◽

Over Time

Decisions made during the establishment and reworking of permanent cordon arms may have long-term consequences on vineyard health and longevity. This review aims to summarise several of the important considerations that must be taken into account during cordon establishment and maintenance. Commonly practiced cordon training techniques such as wrapping developing arms tightly around the cordon wire may result in a constriction of the vascular system, becoming worse over time and disrupting the normal flow of water and nutrients. Studies have shown that other factors of cordon decline such as the onset of vascular diseases may be influenced by pre-existing stress conditions. Such conditions could be further exacerbated by water and heat stress events, an important consideration as these scenarios become more common under the influence of climate change. Vineyard sustainability may be improved by adopting cordon training techniques which promote long-term vitality and avoid a reduction in vine defence response and the costly, premature reworking of vines.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.842.782 ◽

2013 ◽

Vol 842 ◽

pp. 782-787 ◽

Cited By ~ 1

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.

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Triaxial Creep Behavior of Red Sandstone in Freeze-Thaw Environments

Geofluids ◽

10.1155/2020/6641377 ◽

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.

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A Nonlinear Creep Model of Rock Salt and Its Numerical Implement in FLAC3D

Advances in Materials Science and Engineering ◽

10.1155/2015/285158 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8 ◽

Cited By ~ 6

Author(s):

Xinrong Liu ◽

Xin Yang ◽

Junbao Wang

Keyword(s):

Numerical Simulation ◽

Rock Salt ◽

Creep Model ◽

Secondary Development ◽

Nonlinear Creep ◽

Creep Properties ◽

Long Term Stability ◽

Creep Characteristics ◽

Salt Creep

Creep characteristics are integral mechanical properties of rock salt and are related to both long-term stability and security of rock salt repository. Rock salt creep properties are studied in this paper through employing combined methods of theoretical analysis and numerical simulation with a nonlinear creep model and the secondary development in FLAC3Dsoftware. A numerical simulation of multistage loading creep was developed with the model and resulting calculations were found consequently to coincide with previously tested data.

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Unloading Creep Characteristics of Frozen Clay Subjected to Long-Term High-Pressure K0 Consolidation before Freezing

Advances in Civil Engineering ◽

10.1155/2019/7192845 ◽

2019 ◽

Vol 2019 ◽

pp. 1-18 ◽

Cited By ~ 1

Author(s):

Jinbo Jia ◽

Yansen Wang ◽

Yangguang Leng

Keyword(s):

High Pressure ◽

Creep Property ◽

Frozen Soil ◽

Soil Parameters ◽

Unfrozen Water ◽

Term Strength ◽

Creep Characteristics ◽

Frozen Clay ◽

Consolidation Time

Artificial ground freezing has been widely applied in the construction of vertical shafts in deep and thick alluvia. As an important factor, the in situ creep behavior of deep, frozen soil affects the mechanical properties of frozen walls and the safety and stability of shaft linings. Acquiring creep characteristics and deep soil parameters by methods that ignore the engineering and geological situations is currently inadvisable. A series of triaxial unloading tests were conducted with frozen clay subjected to long-term high-pressure K0 consolidation before freezing to research the unloading creep characteristics, creep strength, and other parameters of the clay, and the results indicated the following: (1) The creep behaviors of frozen clay are affected by the consolidation time and consolidation stress. Long-term high-pressure K0 consolidation reduces the creep strain and creep rate of frozen clay. (2) The decrease in the ice and the unfrozen water contents of frozen clay caused by the prolongation of consolidation time result in an increase in the long-term strength and instantaneous strength. Consolidation time has an obvious effect on long-term strength and weakens the creep property of frozen clay. Consolidation stress significantly affects the instantaneous strength. (3) The deformation resistance capability of frozen clay is enhanced by compaction; thus, E1, η1, and η2 increase with prolonged consolidation, and the nonlinearity of the accelerated creep increases.

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Experimental Research on Coupling of Swelling Rock between Swelling and Creep

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.293 ◽

2013 ◽

Vol 353-356 ◽

pp. 293-302

Author(s):

Qiu Yan Fan ◽

Mei Qian Wang ◽

Xian Li ◽

Bo Zhang

Keyword(s):

Creep Deformation ◽

Residual Deformation ◽

Swelling Pressure ◽

Initial Water Content ◽

Term Strength ◽

Compression Tests ◽

Initial Water ◽

Multi Stage ◽

Swelling Rock

Swelling rock has the properties of swelling and creep. Researches on coupling between swelling and creep have not yet been carried out. The expansive Paleogene mudstone is used to laboratory uniaxial compression tests, to find the coupling regularity between swelling and creep under different initial water contents, influent modes and loading methods. For coupling, the creep curves show similar characteristic of non-coupling. The creep deformation increases obviously and the long-term strength decreases comparing with non-coupling. With increasing initial water content, the creep deformation increases for coupling. The creep deformation increases with the enlargement of water-absorption area during the coupling creep. For single-stage and multi-stage loading, the creep regularity is similar to non-coupling. The sample will have a permanent residual deformation when unloaded at the second stable creep stage. The long-term strength of swelling rock is greater than the swelling pressure and the long-term strength is lower than that of non-coupling.

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An Experimental Study on the Creep Characteristics of Sandstone in the Interval of Different Critical Stresses

Shock and Vibration ◽

10.1155/2021/4604027 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Chao Yang ◽

Xingchen Dong ◽

Xuan Xu ◽

Qiancheng Sun

Keyword(s):

Failure Time ◽

Strain Curve ◽

Creep Model ◽

Creep Process ◽

Term Strength ◽

Creep Tests ◽

Critical Stresses ◽

Brittle Sandstone ◽

Time Required

Creep tests on brittle sandstone specimens were performed to investigate the time-dependent characteristics in the interval of different critical stresses. The results showed that failure will not occur when the loaded stress σ1 is less than the critical stress of dilation σcd, while all specimens were destroyed when σ1 is larger than σcd. In addition, the value of σcd was very close to the long-term strength obtained by the method of the isochronous stress-strain curve. Therefore, σcd can be regarded as the long-term strength of the sandstone specimens. When σ1 is larger than σcd, the time required for the failure of specimen tf decreases with the increase of σ1; the creep rate dε/dt increases with time t, and the specimen will be destroyed when it reaches a maximum value (dε/dt)max. Both relationships tf and σ1 and (dε/dt)max and σ1 can be described by the exponential function. Then, a nonlinear damage creep model considering the deformation damage and strength damage in the interval of different critical stresses was established, which can describe the whole creep process and predict the failure time of sandstone specimens.

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