Plasticity of Ice and Sand-Ice Systems

1975 ◽  
Vol 97 (2) ◽  
pp. 479-484 ◽  
Author(s):  
Leonard L. Smith ◽  
J. B. Cheatham
Keyword(s):  
Triaxial Compression ◽  
Plasticity Theory ◽  
Compression Tests ◽  
Loading Rates ◽  
Conventional Triaxial Compression ◽  
Confining Pressures ◽  
Von Mises ◽  
Comparison Of The Results ◽  
Force Displacement ◽  
Triaxial Compression Tests

The experimental deformation of ice and sand-ice systems is compared with predictions based upon plasticity theory. Properties of the materials were determined under various temperatures, confining pressures, and loading rates using conventional triaxial compression tests. Samples were indented at atmospheric pressure using flat punches and sharp wedges at two loading rates and calculated force-displacement relationships were determined for the von Mises, coulomb, and parabolic yield conditions. Comparison of the results of the experiments with the computations indicates that the force-displacement relationships for ice and sand-ice samples can be approximated using plasticity theory.

Post-Critical Mechanical Properties Of Sedimentary Rocks In The Upper Silesian Coal Basin (Poland)

2015 ◽  
Vol 60 (2) ◽  
pp. 517-534 ◽  
Author(s):  
Mirosława Bukowska
Keyword(s):  
Triaxial Compression ◽  
Residual Deformation ◽  
Confining Pressure ◽  
Compression Tests ◽  
Functional Relationships ◽  
Conventional Triaxial Compression ◽  
Upper Silesian Coal Basin ◽  
Confining Pressures ◽  
Waste Rocks ◽  
Triaxial Compression Tests

AbstractIn this paper, we present the results of a study of the Upper Carboniferous sedimentary rocks of the Upper Silesian Coal Basin (USCB) in Poland. We examined the hard coals, which belong to various stratigraphic units of Upper Carboniferous coal-bearing strata, and waste rocks, i.e., sandstones, mudstones, claystones. We present the results of tests of their post-critical mechanical properties. These results are from tests of the post-critical modulus, residual stress and residual deformation from experiments using a servo-controlled testing machine (MTS) with uniaxial compression and conventional triaxial compression. We applied confining pressures of up to 50 MPa at a strain rate of 10−5− 10−1s−1(0.003-6.0 mm/sec). The confining pressure applied in the triaxial compression tests reflected the conditions of current and future mining activities in the USCB at depths exceeding 1.300 metres. The strain rate applied in the tests reflected the values observed in the rockmass surrounding the mine workings and the rate of certain geodynamic phenomena occurring in the Carboniferous rockmass in the USCB, e.g., rock bursts. We present the values of the sub-critical modulus of coals and waste rocks, the functional relationships between the post-critical modulus and uniaxial compression strength, which are described using an exponential function of high correlation coefficients of the given rocks, and an exponential relationship between the post-critical modulus and the longitudinal elasticity modulus (Young’s modulus). Based on the results of tests of the post-critical properties of the Carboniferous rocks under triaxial compression and at various strain rates, we devised the functional relationships between the properties of the rocks and the confining pressure. The dependence of the post-critical modulus of the sandstones and claystones on the confining pressure is described using a polynomial function of degree 2, and that of the coals is described using an exponential function. The relationship between the residual stress and residual deformation in the rocks and the confining pressure was described using a linear function. The obtained results of tests have a practical application in forecasting behaviour of rocks located deep, and designing safe exploitation of mineral deposits. Confining pressures of up to 50 MPa used in the conventional triaxial compression tests allowed us to predict the behaviour of the rock mass at large depths. These data provide general knowledge of the tendencies in behaviour of rocks at substantial depths and the ability to design safe methods of mining deposits of various raw materials, including energy sources. These deposits are mined from increasingly great depths as the reserves are gradually exhausted and collieries of the largest European coal basins are continuously reconfigured.

scholarly journals Mechanical Properties and Numerical Analyses of Basalt Fiber Crumb Rubber Mortars in Soft Rock Roadways

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Jun-Ling Qin ◽  
Wei-Guo Qiao ◽  
Deng-Ge Lin ◽  
Shuai Zhang ◽  
Ji-Yao Wang
Keyword(s):  
Constitutive Model ◽  
Triaxial Compression ◽  
Basalt Fiber ◽  
Soft Rock ◽  
Crumb Rubber ◽  
Compression Tests ◽  
Confining Pressures ◽  
Roadway Support ◽  
Uniaxial Compressive Stress ◽  
Triaxial Compression Tests

The strength of crumb rubber mortars can be improved by the addition of basalt fibers. However, limited studies have been conducted on basalt fiber crumb rubber mortars (BF-CRM), and the constitutive model is still very immature. In this paper, uniaxial compressive stress-strain curves are obtained for several groups of BF-CRM specimens with different contents. By comparison with the GZH model, modified GZH parameters that can be used in a BF-CRM constitutive model are obtained. Then, taking the support scheme of the main substation of a mine as the background, FLAC3D is used to simulate the roadway support, BF-CRM replaces the ordinary mortars in the original support, and triaxial compression tests are performed at different confining pressures. In this way, the application of BF-CRM in roadway support is studied and analyzed.

scholarly journals A Nonlinear Strength Criterion for Frozen Sulfate Saline Silty Clay with Different Salt Contents

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Yanhu Zhao ◽  
Yuanming Lai ◽  
Jing Zhang ◽  
Chong Wang
Keyword(s):  
Triaxial Compression ◽  
Strength Criterion ◽  
Experimental Results ◽  
Saline Soils ◽  
Silty Clay ◽  
Compression Tests ◽  
Frozen Soils ◽  
Conventional Triaxial Compression ◽  
Confining Pressures ◽  
Pressure Melting

It has been proven that the mechanical properties of frozen saline soils are different from frozen soils and unfrozen saline soils. In this paper, in order to study the effects of the salt contents on the strength characteristics of frozen soils, a series of conventional triaxial compression tests are carried out for frozen saline silty clay with Na2SO4 contents 0.0, 0.5, 1.5, and 2.5% under confining pressures from 0 MPa to 18 MPa at −6°C, respectively. The experimental results show that the strength of frozen saline silty clay presents obvious nonlinearity, the strength of frozen saline silty clay increases with increasing confining pressures at first, but with a further increase in confining pressures, the strength decreases because of pressure melting and crushing phenomena under high confining pressures, and salt contents have an important influence on strength of frozen saline silty clay. A strength criterion is proposed on the basis of the experimental results. The strength criterion could well reflect the nonlinear strength characteristic of frozen saline silty clay and the influence of salt contents on frozen saline silty clay.

Experimental Study of Stress-Strain Characteristics of the Fly Ash Blended with Curing Agent

2010 ◽  
Vol 168-170 ◽  
pp. 1934-1942
Author(s):  
Zheng Shen ◽  
Lan Zong ◽  
Xiang Dong
Keyword(s):  
Fly Ash ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Uniaxial Stress ◽  
Curing Agent ◽  
Compression Tests ◽  
Growth Trend ◽  
Stress Strain ◽  
Confining Pressures ◽  
Triaxial Compression Tests

The stress-strain characteristics of the fly ash blended with curing agent was studied using uniaxial and triaxial compression tests. Curing agent JNS-2 was used as the stabilizing agents in sample preparation. Four curing agent JNS-2 contents of 3%, 6%, 9% and 12% were selected for sample preparation. UU triaxial compression tests were conducted in a range of confining pressures from 100 kPa to 300 kPa. The experimental results obtained from the laboratory tests showed that curing age, mixture ratio, compaction degree and confining pressures had significant influence on the shape of curves. Uniaxial stress-strain test results demonstrated that the latter strength and deformation characteristics of the fly ash blended with curing agent grew little and with the increase of curing agent amount and compaction factor, the curve of uniaxial stress-strain changed significantly. On the other hand, triaxial stress-strain test results indicted that the failure strain showed a partial negative growth trend with the increase of curing agent amount, and the failure stress showed a partial positive growth trend with the increase of curing agent amount. When the curve was at high confining pressure, it showed hardening type, when at low confining pressure it showed softening type.

scholarly journals Change of soil mechanical properties due to triaxial sample size

2019 ◽  
Author(s):  
Šarūnas Skuodis ◽  
Neringa Dirgėlienė ◽  
Ieva Lekstutytė
Keyword(s):  
Shear Strength ◽  
Sample Size ◽  
Triaxial Compression ◽  
Specimen Size ◽  
Compression Tests ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Soil Shear Strength ◽  
Confining Pressures ◽  
Triaxial Compression Tests

Triaxial test is widely used to determine the behaviour and strength parameters of soil. Several consolidated drained triaxial compression tests were performed on two specimen sizes of sand and clay. This article investigate and compares the influence of specimen size and scale effect on the soil shear strength. The tests results show that the shear strength parameters are influenced by the clay specimen size. The results indicate that the effect of triaxial clay sample size is more significant with higher confining pressures. The second type of tests carried out on sand samples shows that sample size doesn‘t influence the results of the shear strength. Author’s show that clay analyses can be significantly affected by the choice of the specimen size used to determine shear strength parameters.

scholarly journals Onset of Crack Initiation in Uniaxial and Triaxial Compression Tests of Dolomite Samples

2014 ◽  
Vol 36 (1) ◽  
pp. 23-27 ◽  
Author(s):  
Jerzy Cieślik
Keyword(s):  
Crack Initiation ◽  
Triaxial Compression ◽  
Lateral Strain ◽  
Compression Tests ◽  
Volume Strain ◽  
Conventional Triaxial Compression ◽  
Crack Volume ◽  
Response Method ◽  
Triaxial Compression Tests ◽  
Strain Method

Abstract The paper presents results of laboratory investigation and analysis of crack initiation threshold identification of dolomite samples. First, selected methods for determining crack initiation thresholds are briefly described with special attention paid to four methods: crack volume strain method [14], change in Poisson’s ratio [8], lateral strain response method [16], and dilatancy method [4]. The investigation performed on dolomite samples shows that for the uniaxial and conventional triaxial compression tests, the above mentioned methods give quite similar values, except for the crack volume strain method. Crack initiation threshold determined by this method has a distinctively lower value than that obtained by the other methods. The aim of the present paper was to review and assess these methods for identifying crack initiation threshold based on laboratory tests of dolomite samples.

Analysis on Bolt Supporting Mechanism for Roadways Driving along next Goaf Based on Triaxial Compression Test

2012 ◽  
Vol 594-597 ◽  
pp. 1159-1162
Author(s):  
Sheng Zhong ◽  
Yong Jie Yang ◽  
Min Wang
Keyword(s):  
Mechanical Test ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Test System ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Conventional Triaxial Compression ◽  
Strength And Deformation ◽  
Rock Mechanical Test ◽  
Triaxial Compression Tests

Conventional triaxial compression tests of coal specimens are carried out by MTS815 servo-controlled rock mechanical test system, and the strength and deformation characteristics of coal under different confining pressure are analyzed. On that basis, bolt supporting mechanism of surrounding rocks of roadways driving along next goaf is studied.

scholarly journals Permeability evolution of unloaded coal samples at different loading rates

2014 ◽  
Vol 18 (5) ◽  
pp. 1497-1504 ◽  
Author(s):  
Ze-Tian Zhang ◽  
Zhang Ru ◽  
Jian-Feng Liu ◽  
Xiao-Hui Liu ◽  
Jia-Wei Li
Keyword(s):  
Triaxial Compression ◽  
Axial Loading ◽  
Peak Stress ◽  
Initial Permeability ◽  
Differential Method ◽  
Permeability Evolution ◽  
Compression Tests ◽  
Evolution Law ◽  
Loading Rates ◽  
Conventional Triaxial Compression

As coal mass is often at unloading status during mining process, it is of great significance to push on the research on permeability evolution of unloaded coal samples at different loading rates. A series of triaxial unloading experiments were conducted for initially intact coal samples using an improved rock mechanics testing system, and the permeability was continuously measured by the constant pressure differential method for methane. Permeability evolution law of unloaded coal samples and the influence mechanism of loading rates on that were studied. The results of triaxial unloading experiments indicate that the permeability of coal samples increases throughout the whole testing process without a descent stage, which is different from the permeability evolution law in conventional triaxial compression tests. The maximum permeability of unloaded coal sample, which is 4 to 18 times to its initial permeability, often appears before reaching the peak stress and increases with the decrease of axial loading rate. Stress state corresponding to the surge point of permeability of the unloaded coal samples is also discussed.

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