scholarly journals Experimental Study on the Creep Characteristics of Cemented Backfill in a Goaf under Water Pressure

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
JingYu Zhang ◽  
Huafeng Deng ◽  
GuoYong Duan ◽  
LiangPeng Wan ◽  
Zuosen Luo ◽  
...  
Keyword(s):  
Creep Rate ◽  
Creep Strain ◽  
Axial Stress ◽  
Water Pressure ◽  
Steady Creep ◽  
Long Term Stability ◽  
Groundwater Environment ◽  
Creep Characteristics ◽  
North Water

As the groundwater environment changes in a goaf, the creep deformation of the backfill underwater pressure is worthy of attention. This paper takes the undercut goaf filling in the Yuzhou section of the middle route of the South-to-North Water Transfer Project as an example. Grading loading creep testing of the backfill under different water pressures was carried out using equipment developed by our research team. Based on the experimental results, the following key points were observed: (1) under the same axial stress, the creep strain and steady creep rate increase with increasing water pressure. Under the same water pressure, the creep strain and steady creep rate also increase with increasing axial stress. (2) The long-term strength of a backfill sample decreases with increasing water pressure and has a nonlinear relationship with water pressure. (3) The increase in water pressure exacerbates the damage of a backfill sample, which is manifested by the secondary crack propagation at the time of failure. Therefore, the increase in water pressure degrades the mechanical properties of the backfill to some extent. The results of this paper provide a reliable theoretical basis for the long-term stability analysis of goaf filling underwater pressure.

scholarly journals Study on the Creep Characteristics of Sandstone under Coupled Stress-water Pressure

2019 ◽  
Author(s):  
Zuosen Luo ◽  
Jianlin Li ◽  
Lehua Wang ◽  
Eleyas Assefa ◽  
Huafeng Deng
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Creep Strain ◽  
Water Pressure ◽  
Steady State Creep ◽  
Three Gorges Reservoir Area ◽  
Steady State Creep Rate ◽  
Axial Pressure ◽  
Coupled Stress

Long-term interaction between stress and water pressure leads to creep damage of reservoir bank slope. As a result there will be instability of the bank slopes in many water conservancy projects. The rock mass creeping effect of coupled stress-water pressure was studied by using a typical sandstone rock from the Three Gorges reservoir area. The experiment was conducted by using the rock immersion-air-drying cyclic load rheometer device (designed and manufactured by our research team). Based on the experimental results, the following key points were observed: 1) the creep strain and the steady-state creep rate was increasing when the water pressure increased (at the same stress level). Under the same water pressure, the increase in the axial pressure resulted in the increase in the creep strain and steady creep rate of the sandstone specimens. 2) the increase in the axial pressure increased the creep strain and steady-state creep rate of the sandstone specimens while the water pressure increased. The mechanical properties of the sandstone specimens were affected by the water pressure. 3) the water infiltrates through the pore surfaces. As a result, the rate of deformation will increase while the bearing capacity and long-term strength of the rock decrease. This paper provides a solid theoretical foundation for the evaluation and prediction of reservoir geological hazards.

Finite Element Analysis of Creep Behavior of AZ91D Magnesium Matrix Composites Reinforced with Aluminum Silicate Short Fibers

2012 ◽  
Vol 568 ◽  
pp. 311-314
Author(s):  
Jun Tian ◽  
Shou Yan Zhong ◽  
Zi Qiong Shi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Creep Rate ◽  
Creep Behavior ◽  
Axial Stress ◽  
Short Fiber ◽  
Steady Creep ◽  
Element Analysis ◽  
Interface Module ◽  
The Impact

By Computer finite element analysis, the impact of the interface thickness, the interface module and the short fiber orientation of Al2O3-SiO2(sf)/AZ91D composite on the maximum fiber axial stress and the steady creep rate is studied. Maximum axial stress of the short fiber is in the fiber center, and the axial stress gradually decreases along the direction of the fiber length. When the external stress is constant, the maximum fiber axial stress increases with decreasing of the thickness of the interface, and the steady creep rate increases with the increasing of thickness of the interface. The maximum fiber axial stress increases with the increasing of the interface modulus, the increasing of the interface module improves the load transfer and the creep resistance. Finite element simulation results and experimental results can be well matched to better explain the creep behavior.

scholarly journals Evaluating Long-Term Strength and Time to Failure of Sandstone with Different Initial Damage

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Rongbin Hou ◽  
Yanke Shi ◽  
Leige Xu ◽  
Jinwei Fu ◽  
Kai Zhang
Keyword(s):  
Failure Time ◽  
Term Strength ◽  
Steady Creep ◽  
Creep Failure ◽  
Damage State ◽  
Term Stability ◽  
Long Term Stability ◽  
Creep Stress ◽  
Initial Damage

Long-term strength (LTS) of rock materials is important for the long-term stability analysis and the failure prediction of structures in rock engineering. Numerous studies have been carried out on the LTS for various kinds of rock; however, the effects of initial damage on the LTS and creep failure time of rock have not been conducted. In the present study, the creep experiment with controllable initial damage state of rock was designed. Then, the LTS of rock specimens with different initial damage was determined by four methods (i.e., the isochronous stress-strain curve method, the steady creep discriminated method, the volumetric strain inflexion point determined method, and the intersection of the steady creep rate method). The results show that, with the increase in the initial damage, the LTS of rock decreases and the relationship between the initial damage and the LTS of rock can be described as a linear function. Finally, an evaluation method for predicting the creep failure time of rock under a single stress level was proposed. In addition, the creep failure time of rock with different initial damage under different creep stress levels was obtained by the method. The results indicate that both the initial damage and the creep stress levels have a great influence on creep failure time, i.e., greater initial damage or creep stress leads to a shorter period for rock failure. Thus, for analyzing the long-term stability of rock mass structure, not only the influence of in situ stress but also the initial damage state of the surrounding rock should be considered.

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

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
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.

Experimental Research on Creep Laws of High-Water Material under Real Pressure Water Environment

2016 ◽  
Vol 705 ◽  
pp. 350-354
Author(s):  
Hui Xie ◽  
Ying Chen
Keyword(s):  
Experimental Research ◽  
Carrying Capacity ◽  
Water Pressure ◽  
Water Environment ◽  
High Water ◽  
Term Strength ◽  
Steady Creep ◽  
Creep Tests ◽  
Pressure Water

High-water material is a kind of new inorganic nonmetal material which mainly used in coal mine goaf filling. In order to simulate the real stress conditions of this material in goaf filling, the creep tests of high-water material in real pressure water environment were conducted and the creep laws were also researched. The results showed that water environment was conductive to maintaining and developing the strength of high-water material, and pressure water environment can improve the carrying capacity and long-term strength of high-water material. The deformation of steady creep period decreased while water pressure increased. And strain increasing caused by axial compression was less than strain increasing caused by water pressure. The time needed from starting to steady creep period was longer when water pressure was bigger.

Long-Term Creep Life Estimation for Manaurite XM Material, Using a Constrained Monkman-Grant Plot and Proportional Similitude

2011 ◽  
Author(s):  
Howard R. Voorhees ◽  
H. Chong Rhee ◽  
Michael K. Baker
Keyword(s):  
Creep Rate ◽  
Early Stage ◽  
Test Results ◽  
Steady Creep ◽  
Creep Life ◽  
General Validity ◽  
Curve Fit ◽  
Term Creep ◽  
Short Term Creep

The present paper revisits a constrained use of Monkman-Grant coordinates, a relatively little employed or appreciated method for estimation of long-term creep life. This method is based on a logarithmic plot of remaining life versus the steady creep rate. A procedure, here called proportional similitude, is also discussed as a means to estimate the steady creep rate or time to rupture at an early stage of a test. Numerous studies as yet mostly unpublished increasingly demonstrate for many steel samples from prior creep service that a combination of these two methods permits extrapolations at least as soon, as accurate, and at overall cost similar to other popular procedures. One of the advantages of this procedure is that short term creep test results can be extrapolated to long-term creep life in a transparent manner without complex mathematical maneuvers or need for typical reference properties or initial behavior of the sample. Results now available for a variety of widely-employed materials suggest that these methods may have more-general validity for remaining creep life evaluations than industry has recognized. This paper presents remaining creep lives obtained though a combination of four procedures, i.e., Monkman-Grant, proportional similitude, Larson-Miller, and curve fit methods, for exposed hydrogen reformer tube samples. Results are compared with those of previous Omega analyses performed independently for the same sample.

Stability and Change in Emotional Intelligence: Exploring the Transition to Young Adulthood

2005 ◽  
Vol 26 (2) ◽  
pp. 100-106 ◽  
Author(s):  
James D.A. Parker ◽  
Donald H. Saklofske ◽  
Laura M. Wood ◽  
Jennifer M. Eastabrook ◽  
Robyn N. Taylor
Keyword(s):  
High School ◽  
Emotional Intelligence ◽  
Postsecondary Education ◽  
Life Transition ◽  
Full Time ◽  
Major Life ◽  
Long Term Stability ◽  
Time Period ◽  
Transition From High School

Abstract. The concept of emotional intelligence (EI) has attracted growing interest from researchers working in various fields. The present study examined the long-term stability (32 months) of EI-related abilities over the course of a major life transition (the transition from high school to university). During the first week of full-time study, a large group of undergraduates completed the EQ-i:Short; 32 months later a random subset of these students (N = 238), who had started their postsecondary education within 24 months of graduating from high school, completed the measures for a second time. The study found EI scores to be relatively stable over the 32-month time period. EI scores were also found to be significantly higher at Time 2; the overall pattern of change in EI-levels was more than can be attributed to the increased age of the participants.

Multi-Center Calibration of the Second Reference Material for Thromboplastin, Rabbit, Plain, Coded CRM 149R

1991 ◽  
Vol 65 (03) ◽  
pp. 263-267 ◽  
Author(s):  
A M H P van den Besselaar ◽  
R M Bertina
Keyword(s):  
Reference Material ◽  
Standard Error ◽  
Standard Errors ◽  
Sensitivity Index ◽  
Long Term Stability ◽  
Significant Bias ◽  
The Mean ◽  
The Relationship ◽  
International Sensitivity Index

SummaryIn a collaborative trial of eleven laboratories which was performed mainly within the framework of the European Community Bureau of Reference (BCR), a second reference material for thromboplastin, rabbit, plain, was calibrated against its predecessor RBT/79. This second reference material (coded CRM 149R) has a mean International Sensitivity Index (ISI) of 1.343 with a standard error of the mean of 0.035. The standard error of the ISI was determined by combination of the standard errors of the ISI of RBT/79 and the slope of the calibration line in this trial.The BCR reference material for thromboplastin, human, plain (coded BCT/099) was also included in this trial for assessment of the long-term stability of the relationship with RBT/79. The results indicated that this relationship has not changed over a period of 8 years. The interlaboratory variation of the slope of the relationship between CRM 149R and RBT/79 was significantly lower than the variation of the slope of the relationship between BCT/099 and RBT/79. In addition to the manual technique, a semi-automatic coagulometer according to Schnitger & Gross was used to determine prothrombin times with CRM 149R. The mean ISI of CRM 149R was not affected by replacement of the manual technique by this particular coagulometer.Two lyophilized plasmas were included in this trial. The mean slope of relationship between RBT/79 and CRM 149R based on the two lyophilized plasmas was the same as the corresponding slope based on fresh plasmas. Tlowever, the mean slope of relationship between RBT/79 and BCT/099 based on the two lyophilized plasmas was 4.9% higher than the mean slope based on fresh plasmas. Thus, the use of these lyophilized plasmas induced a small but significant bias in the slope of relationship between these thromboplastins of different species.

Sign in / Sign up

Export Citation Format

Share Document