Large Scale Triaxial Rheological Apparatus Development and Granular Soils Rheological Properties Analysis

2011 ◽  
Vol 90-93 ◽  
pp. 79-89 ◽  
Author(s):  
Xiao Bin Chen ◽  
Jia Sheng Zhang
Keyword(s):  
Rheological Properties ◽  
Stress Level ◽  
Large Scale ◽  
High Stress ◽  
Confining Pressure ◽  
Granular Soil ◽  
Axial Pressure ◽  
Creep Tests ◽  
Creep Properties ◽  
The Stability

To study the granular soil’s rheological properties, a large triaxial rheological apparatus was developed by assemblying a axial pressure and confining pressure providing equipments for the SZ30-4 large scale triaxial apparatus, and the stability examinations proved that the stability of this pressure providing equipments was competent for granular soil’s rheological tests. The large triaxial rheological apparatus have the axial pressure ranging from 0 to 1.0 MPa, confining pressure of 50kPa, 100kPa, 150kPa, 200kPa, 250kPa and the soil sample dimension of Φ=300mm, h=600mm. A series of granular soil creep tests were executed on this apparatus. The tests discussion shows that stress conditions are the main factors, which affects the creep properties of granular soil. There are different rheological properties at different stress level. eg. at low stress level (S=0.1) for the elastic, at middling stress level (0.2<S≤0.6) for the linear viscoelastic and at high stress level (S>0.8) for the non-linear viscous plastic. The total rheological strain nonlinearly increase with stress level increments but linearly increase with confining pressure increments. According to the discussion of redstone granular soil’s creep properties, a rheological component based on hyperbola function was presented, and a nonlinear viscous elastioplastic rheological constitutive model was set up by putting the component and the Burgers model in series. The creep properties analysis shows the rheological model can describe the granular soil’s whole rheological phase well.

Experimental Investigation on Triaxial Rheological Mechanical Properties of Biotite Granitic Gneiss

2011 ◽  
Vol 90-93 ◽  
pp. 311-316
Author(s):  
Yu Zhou Jiang ◽  
Rui Hong Wang
Keyword(s):  
Rheological Properties ◽  
Stress Level ◽  
Rock Specimen ◽  
Testing Machine ◽  
High Stress ◽  
Linear Acceleration ◽  
Confining Pressure ◽  
Granitic Gneiss ◽  
Confining Pressures ◽  
Rheological Experiments

In order to know about the rheological properties of typical biotite granitic gneiss in Xiaowan Hydropower Project, triaxial rheological experiments with biotite granitic gneiss were carried out on the rock servo-controlling rheological testing machine. As a result the typical complete rheological curve of the biotite granitic gneiss indicates that when the stress level is low, the rheological deformation of rock specimen is not obvious; when in high stress conditions, the rock mass rheological properties are very significant with large rheological deformation, including three typical rheological phases. The rheological deformation decreases with the increase of the confining pressure, and at the same time the rheological rate of rock specimen changes with the change of stress level. In low stress state, the corresponding rheological rate of the rock specimen incarnated as the rheological rate attenuation stage and the rheological rate uniform stage, while once the stress level exceeds the long-term strength of rock specimen, the rheological rate would first decreases and then keep at a constant value, and finally it will trend to follow the non-linear acceleration law. The rupture form of the low-intensity biotite granitic gneiss specimen is the main crack surface which causes the damage of rock specimen, and finally generated by the expansion and transfixion of the crack in the initial cavern flaw. The rheological deformation and rupture form of rock specimen in different confining pressures are not exactly the same.

scholarly journals Researches on the Constitutive Models of Artificial Frozen Silt in Underground Engineering

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Yugui Yang ◽  
Feng Gao ◽  
Hongmei Cheng ◽  
Yuanming Lai ◽  
Xiangxiang Zhang
Keyword(s):  
Mechanical Characteristic ◽  
Stress Level ◽  
Strain Softening ◽  
Triaxial Compression ◽  
High Stress ◽  
Constitutive Models ◽  
Confining Pressure ◽  
Frozen Soil ◽  
Conventional Triaxial Compression ◽  
Shear Process

The researches on the mechanical characteristic and constitutive models of frozen soil have important meanings in structural design of deep frozen soil wall. In the present study, the triaxial compression and creep tests have been carried out, and the mechanical characteristic of frozen silt is obtained. The experiment results show that the deformation characteristic of frozen silt is related to confining pressure under conventional triaxial compression condition. The frozen silt presents strain softening in shear process; with increase of confining pressure, the strain softening characteristic gradually decreases. The creep curves of frozen silt present the decaying and the stable creep stages under low stress level; however, under high stress level, once the strain increases to a critical value, the creep strain velocity gradually increases and the specimen quickly happens to destroy. To reproduce the deformation behavior, the disturbed state elastoplastic and new creep constitutive models of frozen silt are developed. The comparisons between experimental results and calculated results from constitutive models show that the proposed constitutive models could describe the conventional triaxial compression and creep deformation behaviors of frozen silt.

Small Punch Creep Properties of Heat Affected Zones of Reduced Activation Ferritic Steel

2008 ◽  
Author(s):  
Taichiro Kato ◽  
Shin-Ichi Komazaki ◽  
Yutaka Kohno ◽  
Hiroyasu Tanigawa
Keyword(s):  
Base Metal ◽  
Creep Test ◽  
Ferritic Steel ◽  
Electron Beam Welding ◽  
High Stress ◽  
Creep Rupture ◽  
Creep Tests ◽  
Creep Properties ◽  
Small Punch ◽  
Uniaxial Creep

The small punch (SP) creep test was carried out at the temperatures of 823∼923 K by using a further miniaturized specimen, namely, TEM disk-type specimen (φ 3.0×t0.25 mm). The tests were applied to the fine grain heat affected zone (FGHAZ), tempered HAZ (THAZ) and base metal (BM), respectively, which were removed from the joint of the reduced activation ferritic steel welded by an electron beam welding, in order to investigate the creep properties of such local regimes. The results obtained from the SP creep test were correlated with those of uniaxial creep tests using the base metal (BM) and welded joint (WJ). Experimental results revealed that there were no large differences between the SP creep rupture strengths of the FGHAZ and THAZ and that of the BM at the relatively high load levels. This result was in good agreement with the fact that the uniaxial creep strength of the WJ was almost coincident with that of the BM at the relatively high stress levels. In addition, the ratio of load (P) to stress (σ), which gave same rupture time, was calculated by using the creep rupture data of the BMs. As a result, the ratio was determined to be 0.43, resulting in the following equation; P = 0.43 σ.

CREEP BEHAVIOR AND LIFE EVALUATION OF AGED P92 STEEL

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4231-4236 ◽  
Author(s):  
BUMJOON KIM ◽  
BYEONGSOO LIM ◽  
DONGHYUN KI
Keyword(s):  
Residual Life ◽  
Creep Condition ◽  
Creep Tests ◽  
P92 Steel ◽  
Creep Properties ◽  
Small Punch ◽  
Punch Test ◽  
Life Evaluation ◽  
Long Time ◽  
The Stability

Creep strength and life of material is closely related with the microstructural characteristics. Components used under creep condition for long time are unable to maintain the stability of microstructure and experience degradation of material. From this viewpoint, it is necessary for safety and residual life of power plant to investigate creep properties of specimens prepared from the material cut directly from the operating service components. The small punch test has been developed as a useful method to estimate mechanical properties because of its miniaturized specimen size. In this study, small punch creep tests were carried out to investigate the effect of aging time on creep properties using P92 steel aged from 0~12100 hrs at 600°C.

The Mechanics and Stability of Gold Nanoparticle-Oligo-Ligand-DNA Systems

2013 ◽  
Vol 1513 ◽  
Author(s):  
Letisha A. McLaughlin ◽  
Mohammed A. Zikry
Keyword(s):  
Gold Nanoparticles ◽  
Dislocation Density ◽  
Large Scale ◽  
Mechanical Stability ◽  
Compressive Loading ◽  
High Stress ◽  
System Stability ◽  
Interfacial Behavior ◽  
Thiol Ligands ◽  
The Stability

ABSTRACTSystems in which DNA is adsorbed onto gold nanoparticles have the potential for applications in gene regulation therapies, drug delivery, sensing, and DNA scaffolding. However, the mechanical stability of gold nanoparticles (AuNPs) and interfacial behavior between the gold nanoparticles and thiol ligands are not well understood or quantified. The stability of DNA-AuNP) systems is, therefore, examined using a large-scale specialized finite-element approach with a dislocation-density based crystalline plasticity framework to model the AuNPs and an elastic description to model thiol ligands, DNA, and the ionic solution. For compressive loading conditions, the system exhibited morphological instabilities in the nanoparticles, as well as high stress and dislocation-density gradients at the thiol-nanoparticle attachment sites, which can affect system stability and attachment strength.

scholarly journals Experimental Study on Influence of Unloading Rate on Creep Characteristics of Marble under High Stress

2021 ◽  
Vol 283 ◽  
pp. 01052
Author(s):  
Huajun He ◽  
Huahui Jin
Keyword(s):  
High Stress ◽  
Creep Condition ◽  
Surrounding Rock ◽  
Lateral Strain ◽  
Creep Tests ◽  
Instantaneous Strain ◽  
Lateral Creep ◽  
Creep Characteristic ◽  
Unloading Rate ◽  
The Stability

In the engineering of high stress area, the measures to control the stability of surrounding rock by reducing excavation footage and excavation speed are to adjust the unloading rate of surrounding rock caused by excavation. In this study, unloading creep tests of marble under high stress conditions were carried out to study the effect of unloading rate. Research results showed that the axial and lateral instantaneous strain and creep strain of the sample increased with the increase of unloading rate; the lateral creep characteristic of marble under unloading condition was stronger than that of axial creep characteristic, and it was more obvious with the increase of unloading rate; the failure of specimens under unloading creep condition was mainly caused by the rapid increase of lateral strain, and the brittleness of rock was increasing with the increase of unloading rate. The Burgers model was used to describe the creep curves of specimens, and the variation of the parameters with the unloading rate was analyzed. The fitting results showed that the instantaneous elastic modulus E1, E'1 and the viscosity coefficients η1, η'1 all decreased with the increase of the unloading rate, which can be described by linear relationship within the unloading rate range of this experiment. Compared with the time of whole creep tests, the time for each specimen to enter the steady-state creep was similar, it was considered that the effect of unloading rate on η2/E2 and η'2/E'2 can be ignored.

scholarly journals The Criteria of Underground Rock Structure Failure and Its Implication on Rockburst in Roadway: A Numerical Method

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaofei Guo ◽  
Zhiqiang Zhao ◽  
Xu Gao ◽  
Zhenkai Ma ◽  
Nianjie Ma
Keyword(s):  
Stress Response ◽  
Plastic Zone ◽  
Large Scale ◽  
High Stress ◽  
Confining Pressure ◽  
Surrounding Rock ◽  
Failure Zone ◽  
Rock Structure ◽  
Large Scope ◽  
High Stress Level

Rockburst in roadway happened along with a large-scale destruction of the surrounding rock. To study the failure laws of the surrounding rock in the process of rockburst in roadway, the evolution behaviors of the plastic zone and the criteria of large-scope failure were studied by using FLAC numerical simulation. Meanwhile, the stress response laws of the plastic zone were studied by loading or unloading in a single direction. The results showed that, in the 20 MPa stress environment, large-scale failure zone would appear when the maximum confining pressure was loaded to 50 MPa or the minimum confining pressure was unloaded to 6 MPa. Loading in the direction of maximum confining pressure or unloading in the direction of minimum confining pressure, when the stresses reached a certain limit, could lead to a large-scale expansion to the failure zone of the surrounding rock a roadway. Meanwhile, the stress response of the plastic zone became more sensitive, which might easily trigger rockburst in roadway. In addition, two sine qua nonstress conditions for rockburst in roadway were determined: high stress ratio and high stress level. This might provide a theoretical basis for the stress source mechanism of roadway rockburst.

scholarly journals Creep of calcareous sand in Tunisia: effect of particle breakage at low stress level

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Hyunwook Choo ◽  
Minhyuk Kwon ◽  
Lamia Touiti ◽  
Young-Hoon Jung
Keyword(s):  
Stress Level ◽  
Creep Deformation ◽  
High Stress ◽  
Particle Breakage ◽  
Time Dependent ◽  
Creep Tests ◽  
Calcareous Sand ◽  
Constant Rate ◽  
Sieve Analyses ◽  
High Stress Level

Abstract Aims/hypothesis One of the critical mechanisms determining creep in granular materials is the breakage of soil particles. This study aims at evaluating the time-dependent creep deformation of calcareous sand at low effective stress conditions. Methods K0 creep tests were performed for both calcareous and silica sands at low stresses of 65 and 120 kPa, and the results of creep tests were compared with the results of constant rate of strain (CRS) tests at high stress levels up to 12 MPa. For a quantitative evaluation of the effect of the particle breakage on the creep deformation of calcareous sand, the relative breakage ($$B_{r}$$ B r ) was determined based on the results of sieve analyses. Results The results demonstrate that Tunisia calcareous sand experiences significant particle breakage during creep and the consequent creep deformation at low stress level. The determined $$B_{r}$$ B r after creep at low stress level is comparable with that after the CRS test at high stress level. Conclusions High potential of particle breakage inherited by characteristic minerology of the calcareous Tunisia sand significantly influences the creep deformation at low stress level.

scholarly journals Creep Mechanics of the High-Stress Soft Rock under Grade Unloading

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Shunjie Huang ◽  
Xiangrui Meng ◽  
Guangming Zhao ◽  
Yingming Li ◽  
Gang Liu ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Creep Test ◽  
Creep Behavior ◽  
High Stress ◽  
Soft Rock ◽  
Confining Pressure ◽  
Deviatoric Stress ◽  
Axial Pressure ◽  
Accelerated Creep ◽  
Test Process

In order to study the creep behavior of deep soft rock, gritstone was chosen as the research subject, and a rock triaxial rheometer (Rock 600-50) and acoustic emission (AE) system (SH-II) were used to carry out the grade unloading confining pressure creep test under a high-stress level. The test results showed that the lateral creep behavior of the gritstone was more prominent than the axial creep under the initial high confining pressure. Under the same confining pressure, the creep strain rate (the direction the same as strain) of the gritstone decreases with the increase in axial pressure. As shown by the AE count, AE signals were generated throughout the entire test process, indicating that the creep was a “microdynamic” process. The creep behavior was characterized by a significant confining pressure effect. As the confining pressure was decreased, the degree of creep increases significantly. During the test, the AE energy increased on the whole but decreases during the creep phase. During the entire test process, the overall energy in the constant deviatoric stress grade unloading of the confining pressure was 45% higher than that in the constant axial pressure grade unloading. The degree of failure of the rock was different in these two unloading creep tests, and the constant axial pressure grade unloading of the confining pressure entails greater damage than the constant deviatoric stress grade unloading of the confining pressure. The main reason was that the former had a lower confining pressure level and longer creep process than the latter, and the sample was mainly characterized by creep damage and large cumulative damage, while the latter features mainly unloading damage. Through the inversion of the Burgers constitutive model and nonlinear damage constitutive model for the creep test curve, the nonlinear constitutive equation can better fit the accelerated creep stage, which suggested that this model can describe the accelerated creep characteristics of the high-stress soft rock.

Deformation Mechanism of the Mountain and Research of Reinforcement in Yanchi Mountain

2011 ◽  
Vol 71-78 ◽  
pp. 1429-1434
Author(s):  
Rui Wang ◽  
Ke Jian Li ◽  
Qiu Yuan Liu ◽  
Yan Qiu
Keyword(s):  
Large Scale ◽  
High Stress ◽  
Mining Activities ◽  
Obvious Effect ◽  
Significant Evidence ◽  
Stress Zone ◽  
The Stability ◽  
The Cost ◽  
High Stress Zone ◽  
Strengthening Method

Mining activities would generate large scale goaf, and the existing of goaf makes the mountain body produce great distortion. Therefore, it has become a kind of serious geological hazard. Based on the concrete conditions of Yanchi Mountain, the simulation with ANSYS was conducted for analyzing the stability of goaf, mine pillar and roof, which would find out the high stress zone and plastic zone of the goaf. Therefore, the conclusion that inadequate of the pillar strength is the main cause of the mountain deformation is drawn, and a new strengthening method which is to strengthen the mine pillar and to increase new mine pillars is put forward on basis of the conclusion.The results show that the strengthening method has an obvious effect, and it reduces the workload and the cost, which also provides very significant evidence for the future studying.

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