Shear Strength of a Cemented Paste Backfill Submitted to High Confining Pressure

2016 ◽  
Vol 858 ◽  
pp. 219-224 ◽  
Author(s):  
Eduardo Eiler Batista de Araújo ◽  
Dragana Simon ◽  
Fagner Alexandre Nunes de França ◽  
Osvaldo de Freitas Neto ◽  
Olavo Francisco dos Santos Jr.
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Binder Content ◽  
Cemented Paste Backfill ◽  
Compression Tests ◽  
Mining Operations ◽  
Geomechanical Properties ◽  
Confining Pressures ◽  
Paste Backfill ◽  
Curing Method

Deep mining operations require special measures in order to keep safe and economic aspects. After mine ore is extracted, voids are created and need to be filled with high-strength, low-cost materials. Cemented Paste Backfill (CPB) has recently become one of the main alternatives in filling stopes. Although numerous papers have mentioned the magnitudes of the strength of this material, its behavior under high confining pressures is still not well understood. Therefore, the purpose of this study is to increase the knowledge regarding the CPB behavior. Triaxial compression tests were performed using a Hoek Cell and Load Frame System under high confining pressures. Samples with two different binder contents were used in order to obtain the CPB strength improvement. Besides the self-weight consolidation curing method, samples were subjected to a different curing method that simulated a zero gravity condition (rotating wheel) in the first curing day to compare their mixture properties. The results suggested that both curing method and binder content have influenced the geomechanical properties of Cemented Paste Backfill. By increasing the curing time, the CPB shear strength has increased slightly, whereas specimens with higher binder content presented a significant increase in shear strength values.

scholarly journals Predicting the Isotropic Volumetric Compression Response of Hydrating Cemented Paste Backfill (CPB)

2021 ◽  
Author(s):  
mohammadamin jafari ◽  
Murray Grabinsky
Keyword(s):  
High Stress ◽  
Binder Content ◽  
Cemented Paste Backfill ◽  
Compression Tests ◽  
Isotropic Compression ◽  
Initial Yield Stress ◽  
Laboratory Test Results ◽  
Cure Time ◽  
Paste Backfill ◽  
Compression Line

Abstract Deep and high-stress mining results in stress transfers onto the previously placed backfill, and mines have recorded several MPa induced backfill stress. Understanding the backfill-rock mass interaction is therefore critical. Previous work considered tabular ore bodies undergoing primarily one-dimensional compression and showed how the backfill reaction curves could be estimated from oedometer laboratory test results. This work considers massive orebodies and develops a similar approach based on isotropic compression curves. Isotropic compression tests exceeding 6 MPa are carried out on samples with 3.0–11.1% binder content, tested at 1-day cure time to 28-day cure time. The compression curve is characterized in three stages: initial elastic compression up to a yield point, followed by a transition stage to the start of a final stage with a linear post-yield compression line in \({\epsilon }_{v}-\text{l}\text{o}\text{g}\left({p}^{\text{'}}\right)\) space. Because these isotropic compression tests are rare (the reported results are the first for Cemented Paste Backfill), attempts are made to relate the isotropic compression test parameters to parameters from the more commonly used Unconfined Compression Strength (UCS) tests. Unifying equations as functions of binder content and cure time are found to determine the initial yield stress and the peak strength from UCS tests. These are then related to the corresponding parameters in isotropic compression. Finally, the slope of the post-yield compression line is found as a function of UCS, thereby enabling complete reconstruction of the isotropic compression response based on parameters from carefully controlled UCS tests, as functions of binder content and cure time. Although the calibrated parameters are specific to the studied mine’s materials, the framework is general and applicable to other mines’ CPBs.

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.

Gravel Content Effect on the Shear Strength of Clay-Gravel Mixtures

2011 ◽  
Vol 71-78 ◽  
pp. 4685-4688 ◽  
Author(s):  
Chen Wang ◽  
Chuan Ni Zhan
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Triaxial Compression ◽  
Constant Strain Rate ◽  
Friction Angle ◽  
Confining Pressure ◽  
Internal Friction Angle ◽  
Compression Tests ◽  
Gravel Content ◽  
Confining Pressures

Gravel content is an important factor affecting the mechanical properties of clay-gravel mixtures. To study the effects of gravel content on the shear strength of clay-gravel mixtures, constant-strain-rate drained triaxial compression tests were conducted for various mixtures. The gravel contents were 30%, 40%, 50% and 70%. The confining pressures were varied from 50kPa to 300kPa. Test results indicate that the deviator stress at failure under the same confining pressure increases with the increase in gravel content. As the gravel content in the mixtures is between 30% and 50%, the shear strength is jointly attributed by clay and gravel. An increase in gravel content results in slight increases in both the cohesion intercept and internal friction angle. At gravel content of up to 70%, the shear strength of the mixture is controlled by that of the gravel, and the cohesion intercept and the internal friction angle increase sharply.

scholarly journals Shear Properties of Cemented Paste Backfill under Low Confining Stress

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Andrew N. Pan ◽  
Murray W. F. Grabinsky ◽  
Lijie Guo
Keyword(s):  
Shear Strength ◽  
Mining Industry ◽  
Binder Content ◽  
Environmental Benefits ◽  
Direct Shear ◽  
Cemented Paste Backfill ◽  
Curing Time ◽  
Confining Stress ◽  
Strain Property ◽  
Paste Backfill

Cemented paste backfill (CPB) plays an important role in the mining industry due to safety, cost efficiency, and environmental benefits. Studies on CPB have improved the design and application of paste backfill in underground mines. Direct shear is one of the most fundamental parameters for assessing backfill strength. This study harnesses direct shear tests to explore the low confining stress behavior of CPB. We perform all the tests in a standard apparatus on the combination of three binder contents of 4.2%, 6.9%, and 9.7% CPB with four curing times of 3, 7, 14, and 28 days, respectively. The applied confining stress levels vary in a range according to the in situ regime. Results are presented by strength envelope, stress-strain property, and shear strength with curing time and binder content. The data suggest that the shear strength follows the Mohr–Coulomb envelope in which the shear strength and behavior are time and binder content dependent. In addition, the results show that shear strength is strongly related to the binder content than the curing time, namely, the higher the degree of binder hydration, the higher the cementation binding force between CPBs.

scholarly journals Experimental Investigation into Multistage versus Conventional Triaxial Compression Tests for a C-Phi Soil

2011 ◽  
Vol 90-93 ◽  
pp. 28-32
Author(s):  
Mohamed A. Shahin ◽  
Alice Cargeeg
Keyword(s):  
Shear Strength ◽  
Simple Procedure ◽  
Triaxial Compression ◽  
Stress Path ◽  
Compression Tests ◽  
Soil Behavior ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Conventional Triaxial Compression ◽  
Confining Pressures

The procedure for conventional triaxial compression (CTC) test requires three separate soil specimens to be examined to failure under different confining pressures so that Mohr-Coulomb (or stress path) failure envelope can be determined and soil shear strength parameters can be obtained. An alternative procedure is the multi-stage triaxial (MST) compression test, which requires only one soil specimen to be tested at three stages of shearing with different confining pressures. There are several advantages for using MST over CTC, which apart from fewer soil specimens, include less laboratory time consumption and reduced effects of heterogeneity among the specimens tested. However, it has been argued in the literature that the advantages of using MST may be compromised by its inability to obtain reliable soil behavior or accurate shear strength parameters. In this paper, the accuracy of MST compared to CTC is investigated for a c-phi soil, and a simple procedure that can be adopted to rectify the MST results is proposed.

Creep behavior in Virginia Beach sand

2013 ◽  
Vol 50 (11) ◽  
pp. 1159-1178 ◽  
Author(s):  
Hamid Karimpour ◽  
Poul V. Lade
Keyword(s):  
Triaxial Compression ◽  
Initial Response ◽  
Grain Structure ◽  
Beach Sand ◽  
Static Fatigue ◽  
Compression Tests ◽  
Time Effects ◽  
Grain Crushing ◽  
Virginia Beach ◽  
Confining Pressures

Triaxial compression tests were performed on dense specimens of Virginia Beach sand at low and high confining pressures to study time effects that relate to grain crushing due to static fatigue or delayed fracture. Experiments to study effects of loading strain rate on subsequent creep showed negligible time effects and no grain crushing at low confining pressures, while tests at high confining pressures indicated increasing amounts of creep with increasing initial loading strain rates and with increasing deviator stress at creep. Investigation of effects of grain-size distribution indicated stiffer initial response and smaller amounts of creep for more uniformly graded soils at high confining pressures. The experimental results showed that structuration effects were not present in the dense Virginia Beach sand. A long-term creep test at high confining pressure indicated continuous creep with no indication of its termination. Sieve analyses following each triaxial test showed that grain crushing, as quantified by Hardin’s relative breakage factor, was proportional to energy input and amount of creep observed for each soil specimen. The creep is due to the time-dependent static fatigue by which the grains crush and cause rearrangement of the grain structure, and this is the reason behind the time effects in granular materials.

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 Experimental Investigation on Mechanical Properties of Cemented Paste Backfill under Different Gradations of Aggregate Particles and Types and Contents of Cementing Materials

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Jiangyu Wu ◽  
Meimei Feng ◽  
Guansheng Han ◽  
Xiaoyan Ni ◽  
Zhanqing Chen
Keyword(s):  
Mechanical Properties ◽  
Cemented Paste Backfill ◽  
Compression Tests ◽  
Deformation Properties ◽  
Paste Backfill ◽  
Strength And Deformation ◽  
Cementing Material ◽  
Optimal Strength ◽  
Ae Signals ◽  
Aggregate Particles

Obtaining the optimal gradation of aggregate particles is beneficial for improving the strength of cemented paste backfill (CPB). Consequently, the uniaxial compression tests with acoustic emission (AE) monitoring were performed on CPB, for which the aggregate particles satisfied the Talbot grading theory. The effects of the Talbot indices of aggregate particles and types and contents of cementing materials on the mechanical properties of CPB were analyzed. The AE characteristics and stress-strain behaviors of CPB were discussed. The results show that the specific Talbot index reflected the optimal strength and deformation properties of CPB is 0.45, and the maximum UCS is 7.6 MPa. The mechanical properties of CPB also can be optimized by changing the type of cementing material and increasing the content of cementing material. The effects of the Talbot indices of aggregate particles and types and contents of cementing materials on the crack damages reflected by the AE signals of CPB are mainly observed in the oa stage and ab stage during the loading process.

Anisotropic shear strength of a residual soil of sandstone

2008 ◽  
Vol 45 (3) ◽  
pp. 367-376 ◽  
Author(s):  
Adriano Virgilio Damiani Bica ◽  
Luiz Antônio Bressani ◽  
Diego Vendramin ◽  
Flávia Burmeister Martins ◽  
Pedro Miguel Vaz Ferreira ◽  
...  
Keyword(s):  
Shear Strength ◽  
Effective Stress ◽  
Yield Surface ◽  
Triaxial Compression ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Compression Tests ◽  
Soil Stiffness ◽  
Particle Bonding

This paper discusses results of laboratory tests carried out with a residual soil originated from the weathering of eolian sandstone from southern Brazil. Parent rock features, like microfabric and particle bonding, are remarkably well preserved within this residual soil. Stiffness and shear strength properties were evaluated with consolidated drained (CID) and consolidated undrained (CIU) triaxial compression tests. Undisturbed specimens were tested with two different orientations between the specimen axis and bedding surfaces (i.e., parallel (δ = 0°) or perpendicular (δ = 90°)) to investigate the effect of anisotropy. When CID triaxial tests were performed with δ = 0°, the yield surface associated with the structure was much larger than when tests were performed with δ = 90°. Coincidently, CIU tests with δ = 0° showed peak shear strengths much greater than for δ = 90° at comparable test conditions. Once the peak shear strength was surpassed, CIU tests followed collapse-type effective stress paths not shown by corresponding tests with remolded specimens. A near coincidence was observed between the yield surface determined with CID tests and the envelope of collapse-type effective stress paths for δ = 0° and δ = 90°.

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