Permeability of mine tailings measured in triaxial cell

2019 ◽  
Vol 56 (4) ◽  
pp. 587-599
Author(s):  
Hernán Patiño ◽  
Eliana Martínez ◽  
Jesús González ◽  
Antonio Soriano
Keyword(s):  
Mine Tailings ◽  
Confining Pressure ◽  
Degree Of Saturation ◽  
Consolidation Pressure ◽  
Coefficient Of Permeability ◽  
Triaxial Cell ◽  
Empirical Function ◽  
Hydraulic Gradients ◽  
The Mean ◽  
Constant Head

The execution of permeability tests using a triaxial cell makes it possible to eliminate the uncertainties that characterize tests performed using conventional equipment. This paper contains the results of 48 tests carried out on three materials recovered from tailings of Riotinto mines (Spain). The equipment involved a modified triaxial system to facilitate the execution of permeability tests under constant head. The tests were performed on samples consolidated to 50, 100, 200, and 300 kPa for four different hydraulic gradients established by applying a backpressure difference (ΔBp). The magnitude of the backpressure difference was applied as a percentage of the initial effective consolidation pressure, expressed as ΔBp/[Formula: see text]; namely, values of 10%, 15%, 20%, and 25%, which resulted in hydraulic gradients between 5 and 80. The backpressure (Bp) was constant (400 kPa) in all cases, allowing a degree of saturation close to 100% to be achieved. This was verified by calculating Skempton’s B parameter, which was very close to unity in all cases. The results indicate that it is feasible to define an empirical function including the coefficient of permeability (k) and the effective consolidation pressure ([Formula: see text]), the mean effective confining pressure ([Formula: see text]), and the backpressure differential (ΔBp).

scholarly journals Investigation on the Influence of Temperature and Confining Pressure on the Hydraulic Conductivity of the Integrated and Fractured Jurassic Conglomerates

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Dingyang Zhang ◽  
Wanghua Sui ◽  
Jiawei Liu
Keyword(s):  
Hydraulic Conductivity ◽  
Shear Failure ◽  
Negative Relationship ◽  
Confining Pressure ◽  
Regression Equations ◽  
Intact Sample ◽  
Triaxial Cell ◽  
Different Temperatures ◽  
Confining Pressures ◽  
Constant Head

This paper presents an experimental investigation on the properties of hydraulic conductivity and permeability of conglomerates under different temperatures and confining pressures with integrated samples and samples with shear failure. Constant head tests were carried out in a temperature-controlled triaxial cell with samples obtained from the Zhuxianzhuang Coal Mine. Five levels of temperatures (10°C, 20°C, 28°C, 35°C, and 50°C) and three levels of confining pressures (3 MPa, 5 MPa, and 7 MPa) were chosen for the tests. The results show that there is a negative relationship between hydraulic conductivity and confining pressure with both original and shear failure samples. An inflection point of 35°C is found in the relationship between the flow rate and temperature. However, with increasing temperature conditions, hydraulic conductivity first increases and then decreases at 50°C with the intact sample, while hydraulic conductivity first decreases from 20°C and then increases with the shear failure sample. Finally, nonlinear regression equations of hydraulic conductivity and temperature were obtained under different confining pressures.

scholarly journals First observations of noctilucent clouds by lidar at Svalbard

2003 ◽  
Vol 3 (1) ◽  
pp. 521-549 ◽  
Author(s):  
J. Höffner ◽  
C. Fricke-Begemann ◽  
F.-J. Lübken
Keyword(s):  
Lower Thermosphere ◽  
Degree Of Saturation ◽  
Noctilucent Clouds ◽  
Backscatter Coefficient ◽  
Maximum Volume ◽  
Height Range ◽  
Large Variability ◽  
The North ◽  
The Mean ◽  
Bad Weather

Abstract. In summer 2001 a potassium lidar was installed near Longyearbyen (78° N) on the north polar island of Spitsbergen which is part of the archipelago Svalbard. At the same place a series of meteorological rockets ("falling spheres", FS) were launched which gave temperatures from the lower thermosphere to the stratosphere. The potassium lidar is capable of detecting noctilucent clouds (NLCs) and of measuring temperatures in the lower thermosphere, both under daylight conditions. In this paper we give an overview on the NLC measurements (the first at this latitude) and compare the results with temperatures from meteorological rockets which have been published recently (Lübken and Müllemann, 2003).. NLCs were observed from 12 June (the first day of operation) until 12 August when a period of bad weather started. When the lidar was switched on again on 26 August, no NLC was observed. The mean occurrence frequency in the period 12 June–12 August ("lidar NLC period") is 77%. The mean of all individual NLC peak altitudes is 83.6 km (variability: 1.1 km). The mean peak NLC altitude does not show a significant variation with season. The average top and bottom altitude of the NLC layer is 85.1 and 82.5 km, respectively, with a variability of ~1.2 km. The mean of the maximum volume backscatter coefficient ßmax at our wavelength of 770 nm is 3.9×10−10/m/sr with a large variability of +/−3.8×10−10/m/sr. Comparison of NLC characteristics with measurements at ALOMAR (69° N) shows that the peak altitude and the maximum volume backscatter coefficient are similar at both locations but NLCs occur more frequently at higher latitudes. Simultaneous temperature and NLC measurements are available for 3 flights and show that the NLC layer occurs in the lower part of the height range with super-saturation. The NLC peak occurs over a large range of degree of saturation (S) whereas most models predict the peak at S=1. This demonstrates that steady-state considerations may not be applicable when relating individual NLC properties to background conditions. On the other hand, the mean variation of the NLC appearance with height and season is in agreement with the climatological variation of super-saturation derived from the FS temperature measurements.

scholarly journals Macroscopic and Mesoscopic Mechanical Properties of Mine Tailings with Different Dry Densities under Different Confining Pressures

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhi-jun Zhang ◽  
Yao-hui Guo ◽  
Ya-kun Tian ◽  
Lin Hu ◽  
Xi-xian Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coordination Number ◽  
Mine Tailings ◽  
Confining Pressure ◽  
Simulation Software ◽  
Particle Flow ◽  
Dry Density ◽  
Stress Strain ◽  
High Confining Pressure ◽  
Confining Pressures

Particle flow numerical simulation software (PFC3D) was utilized to establish the consolidated-undrained triaxial compression test numerical models of mine tailings with different dry densities to deeply investigate the macroscopic and microscopic characteristics of mine tailings in a tailing pond in Hunan Province. Comparing the results of the simulation and the laboratory experiment, the mesoscopic parameters of the particle flow numerical simulation were obtained through continuously adjusting the mesoscopic parameter with the higher degree of agreement between the stress-strain curve, the peak strength, and the elastic modulus as the determining standard. The macroscopic and microscopic characteristics of mine tailings were studied from the perspectives of stress-strain, axial strain-volume strain, coordination number, particle velocity vector, and contact force between particles. After numerous numerical tests, it was found that the PFC3D simulation results are consistent with experiment results of the dry density tailing samples under different confining pressures; compared with the high confining pressure, the simulation test results at lower confining pressures were more with that of the laboratory tests; low density and high confining pressure both have inhibitory effect on the dilatancy characteristics of triaxial samples; with the same confining pressure, the dilatancy tendency of low dry density samples is suppressed comparing with the high dry density samples. The initial coordination number of the numerical model is large, which proves that the contact degree of the model is good to some extent.

scholarly journals Triaxial experiments on iceberg and glacier ice

1995 ◽  
Vol 41 (139) ◽  
pp. 528-540 ◽  
Author(s):  
R. E. Gagnon ◽  
P. H. Gammon
Keyword(s):  
Large Scale ◽  
Freezing Point ◽  
Shear Plane ◽  
Confining Pressure ◽  
Ductile Deformation ◽  
Dominant Factor ◽  
Stick Slip ◽  
Glacier Ice ◽  
Confining Pressures ◽  
The Mean

Abstract Triaxial experiments, at confining pressures in the range 0–13.79 MPa, have been performed on glacial ice collected from four icebergs and one glacier. Tests were conducted at strain rates in the range of 5 × 10−5 to 5 × 10−5s−1 and at four temperatures in the range of −1° to −16°C. Depending on test conditions, the ice failed by one of four possible modes ductile deformation, due to extensive non-interacting microcracks; fracture along a shear plane followed by continuous or stick-slip sliding; large-scale brittle fracture; and combined ductile and shear-plane fracture and slip The strength Increased with decreasing temperature, increasing strain rate up to 5 × 10−3s−1 and increasing confining pressure at the lower temperatures. The strength at 5 × 10−2s−1 was lower than at 5 × 10−3s−1 probably because extension and interaction of microcracks is enhanced at the higher rate. For higher confining pressures at −1°C, the strength decreased due to freezing-point depression. The ice from the different sources exhibited different mean uniaxial compressive strengths. The mean number of air bubbles per unit volume correlated with the mean uniaxial compressive strengths and this may be the dominant factor distinguishing the strengths of the various ice types.

The Effect of Sampling on the Undrained Soil Properties of a Leda Soil

1971 ◽  
Vol 8 (4) ◽  
pp. 546-557 ◽  
Author(s):  
Gerald P. Raymond ◽  
David L. Townsend ◽  
Miroslav J Lojkasek
Keyword(s):  
Sampling Method ◽  
Sampling Methods ◽  
Axial Stress ◽  
Pressure Coefficient ◽  
Confining Pressure ◽  
Stress Difference ◽  
Consolidation Pressure ◽  
Failure Index ◽  
Confining Pressures ◽  
Leda Clay

The comparison of consolidated undrained triaxial results on sensitive Leda clay sampled by six different sampling methods is presented. The results indicate that the failure index, represented by the axial stress difference as a fraction of the axial failure stress difference against strain plots, are widely different at very low consolidation pressures, but are similar and approximate to the results from block samples as the consolidation pressure is increased. The pore pressure coefficient A appears to be independent of the sampling method and remains remarkably consistent throughout any test (up to failure) except where the confining pressure is very low or above the preconsolidation pressure.Routine commercial sampling methods (including laboratory preparation) using 50-mm diameter samples were found to partially destroy the cementation bonds, causing a decrease in strength at low confining pressures and an unsafe increase in strength at medium confining pressures. This trend is decreased by better sampling.

scholarly journals Distribution and air-sea exchange of mercury (Hg) in the Yellow Sea

2011 ◽  
Vol 11 (6) ◽  
pp. 2881-2892 ◽  
Author(s):  
Z. J. Ci ◽  
X. S. Zhang ◽  
Z. W. Wang ◽  
Z. C. Niu ◽  
X. Y. Diao ◽  
...  
Keyword(s):  
East Asia ◽  
Surface Waters ◽  
Yellow Sea ◽  
Elemental Mercury ◽  
Degree Of Saturation ◽  
The Yellow Sea ◽  
East China ◽  
Emission Rates ◽  
The Mean ◽  
Mean Concentration

Abstract. The Yellow Sea, surrounded by East China and the Korea Peninsula, is a potentially important receptor for anthropogenic mercury (Hg) emissions from East Asia. However, there is little documentation about the distribution and cycle of Hg in this marine system. During the cruise covering the Yellow Sea in July 2010, gaseous elemental mercury (GEM or Hg(0)) in the atmosphere, total Hg (THg), reactive Hg (RHg) and dissolved gaseous mercury (DGM, largely Hg(0)) in the waters were measured aboard the R/V Kexue III. The mean (±SD) concentration of GEM over the entire cruise was 2.61 ± 0.50 ng m−3 (range: 1.68 to 4.34 ng m−3), which were generally higher than other open oceans. The spatial distribution of GEM generally reflected a clear gradient with high levels near the coast of East China and low levels in open waters, suggesting the significant atmospheric Hg outflow from East China. The mean concentration of THg in the surface waters was 1.69 ± 0.35 ng l−1 and the RHg accounted for a considerable fraction of THg (RHg: 1.08 ± 0.28 ng l−1, %RHg/THg = 63.9%). The mean concentration of DGM in the surface waters was 63.9 ± 13.7 pg l−1 and always suggested the supersaturation of Hg(0) in the surface waters with respect to Hg(0) in the atmosphere (the degree of saturation: 7.8 ± 2.3 with a range of 3.6–14.0). The mean Hg(0) flux at the air-sea interface was estimated to be 18.3 ± 11.8 ng m−2 h−1 based on a two-layer exchange model. The high wind speed and DGM levels induced the extremely high Hg(0) emission rates. Measurements at three stations showed no clear vertical patterns of DGM, RHg and THg in the water column. Overall, the elevated Hg levels in the Yellow Sea compared with other open oceans suggested that the human activity has influenced the oceanic Hg cycle downwind of East Asia.

scholarly journals Influence of the Saturation Ratio on Concrete Behavior under Triaxial Compressive Loading

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Xuan-Dung Vu ◽  
Matthieu Briffaut ◽  
Yann Malecot ◽  
Laurent Daudeville ◽  
Bertrand Ciree
Keyword(s):  
Nuclear Power ◽  
Water Saturation ◽  
Confining Pressure ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Saturation Ratio ◽  
Concrete Wall ◽  
Saturation State ◽  
Massive Concrete ◽  
The Impact

When a concrete structure is subjected to an impact, the material is subjected to high triaxial compressive stresses. Furthermore, the water saturation ratio in massive concrete structures may reach nearly 100% at the core, whereas the material dries quickly on the skin. The impact response of a massive concrete wall may thus depend on the state of water saturation in the material. This paper presents some triaxial tests performed at a maximum confining pressure of 600 MPa on concrete representative of a nuclear power plant containment building. Experimental results show the concrete constitutive behavior and its dependence on the water saturation ratio. It is observed that as the degree of saturation increases, a decrease in the volumetric strains as well as in the shear strength is observed. The coupled PRM constitutive model does not accurately reproduce the response of concrete specimens observed during the test. The differences between experimental and numerical results can be explained by both the influence of the saturation state of concrete and the effect of deviatoric stresses, which are not accurately taken into account. The PRM model was modified in order to improve the numerical prediction of concrete behavior under high stresses at various saturation states.

scholarly journals Dilatancy Characteristics and Constitutive Modelling of the Unsaturated Soil Based on Changes in the Mass Water Content

2021 ◽  
Vol 11 (11) ◽  
pp. 4859
Author(s):  
Xiao Xu ◽  
Guoqing Cai ◽  
Zhaoyang Song ◽  
Jian Li ◽  
Chongbang Xu ◽  
...  
Keyword(s):  
Water Content ◽  
Unsaturated Soil ◽  
Soil Mechanics ◽  
Constitutive Models ◽  
Confining Pressure ◽  
Prediction Equation ◽  
Constitutive Modelling ◽  
Degree Of Saturation ◽  
Model Parameters ◽  
High Plasticity

Most soil mechanics theories are limited to strain hardening and shrinkage under high compressive stresses, and there are some shortcomings in the selection of suction or degree of saturation as the water content state varies in the constitutive models of unsaturated soil. Based on the triaxial shear tests of unsaturated compacted soil (a silt of high plasticity) with different water content and confining pressure (low-confining), a shear dilatancy model of unsaturated soil based on the mass water content is proposed in this paper. The influence of the water content on the shear deformation characteristics of the unsaturated soil is analysed. The stress–dilatancy relationship and the prediction equation of the minimum dilatancy rate of the unsaturated soil under different water content and different confining pressure are provided. Selecting the mass water content as the state variable, a constitutive model suitable for the dilatancy of unsaturated soil is established. The method of determining model parameters based on the mass water content is analysed. The applicability of the model is verified by comparisons between the predicted and experimental results.

Development and verification of a coefficient of permeability function for a deformable unsaturated soil

1998 ◽  
Vol 35 (3) ◽  
pp. 411-425 ◽  
Author(s):  
Shangyan Huang ◽  
S L Barbour ◽  
D G Fredlund
Keyword(s):  
Porous Medium ◽  
Unsaturated Soil ◽  
Void Ratio ◽  
Constant Volume ◽  
Saturated Soil ◽  
Silty Sand ◽  
Degree Of Saturation ◽  
Experimental Program ◽  
Coefficient Of Permeability ◽  
Permeability Function

The modelling of flow through saturated/unsaturated soils has become routine in geotechnical and geo-environmental engineering. The analysis requires that the coefficient of permeability for an unsaturated soil be defined. The coefficient of permeability can be estimated based on currently available procedures. However, each procedure has limitations and consequently cares should be taken in the selection of a proper procedure. The coefficient of permeability of a saturated soil is a function of void ratio. The coefficient of permeability of an unsaturated soil of constant volume, is a function of the degree of saturation. However, soil is deformable and both the degree of saturation and the void-ratio influence the coefficient of permeability of a compressible, unsaturated soil. In this paper, the literature pertaining to the coefficient of permeability function for an unsaturated soil of constant volume and the coefficient of permeability for a deformable saturated soil are reviewed. A new coefficient of permeability function for a deformable unsaturated porous medium is then developed. A series of triaxial permeameter tests on unsaturated silty sand are described and the results from the experimental program are analyzed using the general form of the newly developed permeability function. The results show good agreement between the experimental data and the proposed model for a deformable unsaturated porous medium.Key words: unsaturated soil, coefficient of permeability, permeability function, soil-water characteristic curve, triaxial permeameter, deformable porous medium.

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