scholarly journals High-density bimodal bentonite blends for hydraulic sealings at the Ibbenbüren coalmine

Clay Minerals ◽  
2015 ◽  
Vol 50 (3) ◽  
pp. 391-403 ◽  
Author(s):  
Felicitas Wolters ◽  
Wiebke Baille ◽  
Katja Emmerich ◽  
Eva Schmidt ◽  
Christian Wolters ◽  
...  
Keyword(s):  
Swelling Pressure ◽  
Mining Area ◽  
Applied Strain ◽  
Sand Mixture ◽  
Pressure Tests ◽  
Pressure Development ◽  
Pressure Water ◽  
Sufficient Magnitude ◽  
Sealing Materials ◽  
Oedometer Tests

AbstractThe two high-pressure water-retaining dams at the Ibbenbüren coalmine in Münsterland (Germany) have to perform reliably under the induced tension caused by further exploitation of the current mining area. The load-bearing and the sealing functions of the new barriers were separated and new sealing materials were developed. An innovative multilayer sealing system of bentonite and sandwiched equipotential layers (SANDWICH) supporting homogeneous swelling and sealing, independent of formation water (Nüesch et al., 2002), was applied in this project. A testing program of strain-controlled swelling pressure tests on compacted bentonite specimens and on a bentonite/sand mixture was conducted to ensure an adequate potential for swelling-pressure development.The measurements under constant volume for dry densities between 1.45 g/cm3 and 1.67 g/cm3 showed an evolving swelling pressure between 1.04 and 1.8 MPa for 100% bentonite samples. Straincontrolled oedometer tests for zero strain and step-wise applied strain up to 2% revealed that a sufficient magnitude of swelling pressure existed at maximum applied strain.

scholarly journals Modelling the hydromechanical behaviour of expansive granular mixtures upon hydration

2020 ◽  
Vol 195 ◽  
pp. 02006
Author(s):  
Benjamin Darde ◽  
Anh Minh Tang ◽  
Jean-Michel Pereira ◽  
Patrick Dangla ◽  
Jean-Noël Roux ◽  
...  
Keyword(s):  
Swelling Pressure ◽  
Relative Volume ◽  
Radioactive Waste Disposal ◽  
Material Behaviour ◽  
Powder Mixtures ◽  
Basic Model ◽  
Granular Mixtures ◽  
Pressure Tests ◽  
Hydromechanical Behaviour ◽  
Sealing Materials

Bentonite pellet-powder mixtures are candidate sealing materials in radioactive waste disposal concepts. The mixture is installed in galleries in dry state as a granular material. The material is progressively hydrated by the pore water of the host rock and becomes homogeneous. Before homogenisation, the granular structure controls the material behaviour. In the present work, a modelling approach able to address particular features of pellet-powder mixtures is introduced. Two domains are considered: i) granular, and ii) homogeneous. The material behaviour before homogenisation is studied through Discrete Element Method (DEM) simulations. Constitutive laws for the granular state are proposed from DEM results. The behaviour of the homogenised material is described by a modified Barcelona Basic Model (BBM). Transition from granular to homogeneous states depends on suction and relative volume fractions of pellets and powder. Swelling pressure tests performed in the laboratory are satisfactorily simulated using this approach.

scholarly journals Investigations on densified beech wood for application as a swelling dowel in timber joints

Holzforschung ◽  
2019 ◽  
Vol 73 (6) ◽  
pp. 559-568 ◽  
Author(s):  
Philippe Grönquist ◽  
Thomas Schnider ◽  
Andreas Thoma ◽  
Fabio Gramazio ◽  
Matthias Kohler ◽  
...  
Keyword(s):  
Beech Wood ◽  
Compressive Loading ◽  
Swelling Pressure ◽  
European Beech ◽  
Densified Wood ◽  
Robotic Fabrication ◽  
Recovery Capacity ◽  
Pressure Development ◽  
Multiple Cycles ◽  
Wooden Structures

AbstractFor robotic fabrication of wooden structures, the simple, quick and tight joining of elements can be solved using swelling hardwood dowels. This topic has been the focus of the present study, and the set-recovery capacity of densified wood (dW) as dowel material was investigated. European beech was compressed in the radial direction at 103°C and 10% moisture content (MC) to a compression ratio of 40%. Multiple swelling and shrinkage cycles were applied to measure swelling behavior, swelling pressure development and combined swelling and creep under compressive loading. It has been demonstrated that dW shows increased swelling and more persisting swelling pressures than native wood (nW). The set-recovery prevents significant contact-stress relaxation over multiple cycles of MC change. Application as a structural joining element for robotic fabrication was studied by shear lap joint tests on round double-dovetail swelling dowels.

scholarly journals Interpretation of the loading–wetting behaviour of compacted soils within the “MPK” framework. Part I: Static compaction

2016 ◽  
Vol 53 (5) ◽  
pp. 783-805 ◽  
Author(s):  
Tanvirul Islam ◽  
Jayantha Kodikara
Keyword(s):  
Moisture Content ◽  
Unsaturated Soils ◽  
Void Ratio ◽  
Swelling Pressure ◽  
The State ◽  
Moisture Ratio ◽  
Parameter Determination ◽  
Compacted Soils ◽  
Pressure Development ◽  
State Path

Depending on the state paths, loading–wetting of compacted unsaturated soils can exhibit complex volumetric behaviour, such as swelling, collapse, collapse followed by swelling, swelling followed by collapse, and swelling pressure development. Microscopically, these behaviours arise from complex interactions among applied stresses, air–water pressure deficit or suction at the water menisci, moisture content or degree of saturation in the voids, and the nature of the micro- and macrosoil aggregates of compacted soils that depend on the level of suction. While significant advances have been made in modelling hydromechanical behaviour of compacted unsaturated soils taking these interactions into account, input parameter determination requires advanced testing equipment and the testing processes can be very time-consuming. In 2012, a relatively simple and practical framework within the void ratio – moisture ratio (water volume / solid volume) – net stress space (referred to as the MPK framework) has been proposed by Kodikara to explain–predict these state paths. A desirable feature of this framework is that it identifies a direct link between the well-known compaction curve and the compacted soil constitutive behaviour. This paper presents a comprehensive series of tests on statically compacted soils, the results of which are in close agreement with this framework. Two soil types, namely lightly reactive kaolin and more reactive clay (referred to as Merri Creek soil), were used in the testing. The soils were prepared with different moisture contents from the dry state and statically compacted at constant water content to obtain void ratio – moisture ratio – net stress constitutive surfaces, as well as soil specimens for state path tests. The state path test results of yielding under loading, collapse under wetting, swelling pressure development, and change in yield pressure due to wetting are explained within this framework. In addition, some published data on a silty soil mixture were also analysed, highlighting that the framework is valid, regardless of the degree of reactivity of the soil. Suction was not measured in the authors’ experiments, as it was not required to explain the above state paths according to this framework. However, it is recognised that suction is the conjugate state variable to the moisture content. Therefore, in future experiments, suction will be measured and its role will be fully explained within the framework, adding more generality.

Investigation of the swelling pressure development during slow pyrolysis of thermoplastic coals

2005 ◽  
Vol 74 (1-2) ◽  
pp. 88-95 ◽  
Author(s):  
Vladimir Strezov ◽  
John A. Lucas ◽  
Les Strezov
Keyword(s):  
Swelling Pressure ◽  
Slow Pyrolysis ◽  
Pressure Development

scholarly journals Effect of Pozzolana and Lime on Expansive Soil Properties

2021 ◽  
Vol 9 (3) ◽  
pp. 94-101
Author(s):  
Omer S. M. Hamza ◽  
Magdi M. E. Zumrawi ◽  
Awad E. M. Mohamed
Keyword(s):  
Soil Properties ◽  
Expansive Soil ◽  
Swelling Pressure ◽  
Swelling Potential ◽  
Quick Lime ◽  
Disturbed Soil ◽  
Constant Content ◽  
Pressure Tests ◽  
Free Swell ◽  
Very High

This study investigates the effect of pozzolana and quick lime as stabilizer materials on expansive soil properties. Disturbed soil sample was collected from Al-Qadarif city in east of Sudan. The basic properties, swelling and strength of the soil were measured. The soil shows very weak strength and very high swelling potential. Mineralogical analysis tests were conducted to the soil using XRD tests. The soil contains significant amount of montmorillonite mineral (86%). Laboratory tests were undertaken on soil stabilized with varying percentage of pozzolana only (0, 5, 10, 15, 20, and 30%) and combination of pozzolana with constant content of quick lime (5%). Compaction, California Bearing Ratio (CBR), free swell, swell present and swelling pressure tests were performed on natural and treated soil. The pozzolana was obtained from Jebal Meidob and the lime obtained from local kilns in Kassala. The results showed that the treatment of expansive soil by combination of pozzolana and quick lime reduced soil swelling coupled with significant increase on soil strength. While the use of pozzolana only has marginal effective. It could be concluded that stabilization of expansive soil by pozzolana-lime admixture is successful.  

scholarly journals Numerical simulation of the effect of fault inclination on the sudden water of the fault bottom plate

2020 ◽  
Vol 185 ◽  
pp. 02026
Author(s):  
Xiao-Liang Jia
Keyword(s):  
Base Plate ◽  
Mining Area ◽  
Simulation Software ◽  
Bottom Plate ◽  
Working Surface ◽  
Safety Design ◽  
Pressure Water ◽  
Ground Stress ◽  
Small Inclination ◽  
Surface Plate

The main reason for the frequent occurrence of water accidents on the bottom plate of the working surface near the mine fault in China is that the excavation activities cause the fault to activate and direct the pressure water of the aquifer. The distribution of ground stress fields and plastic regions under the influence of extraction disturbance spree is analyzed by using the flaC3D simulation software FLAC3D simulation software. The results show that the greater the inclination of the fault, the greater the shear stress and the normal stress at the fault level, and the deeper the activation range of the mining fault is larger than that of the shallow one ,and the small inclination positive fault is more likely to produce the fissure between the working surface base plate and the aquifer, and the small inclination positive fault should be left with a wider water-bearing coal column in the actual safety design. Using this software, the evolution of the stress field and plastic zone in the adjacent mining area is a preview, which is of great application value to prevent the surface plate burst water and determine the retention width of the fault waterproof coal column.

scholarly journals Behavior of compacted Ca-bentonite subjected to HMC loading: observations and interpretation

2021 ◽  
Vol 337 ◽  
pp. 04004
Author(s):  
Takayuki Motoshima ◽  
Sachie Iso ◽  
Tomoyoshi Nishimura
Keyword(s):  
Chemical Properties ◽  
Swelling Pressure ◽  
Simulation Models ◽  
Radioactive Waste Disposal ◽  
Physical Parameters ◽  
Unconfined Compression ◽  
Unconfined Compression Test ◽  
Sand Mixture ◽  
Pressure Test ◽  
Calcium Bentonite

This study presents result of HMC experimental test and discussions of chemical effort in Cabentonite. SWCC test, swelling pressure test and unconfined compression test as hydro-mechanical-chemical (HMC) test were applied to Cabentonite-sand mixture. Na-type bentonite has been studied to predict safety and confidence for artificial barrier layer consist of bentonite that many experimental research reports are represented, and can offer technology advanced comprehensive performance due to mathematical simulation models associated to physical parameters on thermal-hydration-mechanical-chemical properties. This study proposed a significant property for calcium bentonite to relate evaluating safety in radioactive waste disposal system, which emphasised much influence of suction and salinity chloride to hydration-mechanical behaviour for Calcium bentonite.

Some aspects of the compressibility behaviour of a clayey sand

2001 ◽  
Vol 38 (6) ◽  
pp. 1177-1186 ◽  
Author(s):  
Flavia Burmeister Martins ◽  
Luiz Antônio Bressani ◽  
Matthew Richard Coop ◽  
Adriano Virgilio Damiani Bica
Keyword(s):  
Published Data ◽  
Clayey Sand ◽  
One Dimensional ◽  
Sand Mixture ◽  
Oedometer Tests ◽  
Compression Line ◽  
Normal Compression

The intrinsic behaviour of a residual clayey sand derived from sandstone was investigated in one-dimensional compression. The data show some interesting differences when compared with other published data, in that no unique normal compression line can be identified. Although the compressibility on first loading is similar to that for many sandy materials at states on their normal compression lines, the locations of the compression curves were found to be a function of the initial voids ratio, and there was no convergence at higher stresses. Tests on a model clay-sand mixture indicated that this behaviour is common to gap-graded clayey sands.Key words: sands, compressibility, oedometer tests.

scholarly journals Experimental study on the influence of preliminary desiccation on the swelling pressure and hydraulic conductivity of compacted bentonite

Clay Minerals ◽  
2018 ◽  
Vol 53 (4) ◽  
pp. 733-744 ◽  
Author(s):  
Lin Zhi Lang ◽  
Wiebke Baille ◽  
Snehasis Tripathy ◽  
Tom Schanz
Keyword(s):  
Hydraulic Conductivity ◽  
Swelling Pressure ◽  
Shrinkage Strain ◽  
Volumetric Shrinkage ◽  
Barrier Materials ◽  
Compacted Bentonite ◽  
Swelling Capacity ◽  
Pressure Tests ◽  
Volumetric Shrinkage Strain ◽  
Volume Swelling

ABSTRACTIn deep geological repositories, compacted bentonites have been proposed for use as barrier materials for isolating nuclear waste. The prevailing thermo-hydro-mechanical boundary conditions in the repositories may affect the swelling capacity and permeability of the compacted bentonites. In this study, the effect of preliminary desiccation on the subsequent hydro-mechanical behaviour (swelling pressure and hydraulic conductivity) of compacted Calcigel bentonite was investigated experimentally at 22°C and 80°C. In the first stage of the test, the compacted specimens were subjected to suction-controlled desiccation at 22°C and 80°C using the vapour-equilibrium technique. After the water content reached equilibrium at a given suction, the axial, radial and volumetric shrinkage strains were measured. Afterwards, constant-volume swelling-pressure tests were performed on the desiccated specimens (second test stage) by saturating the dried specimens with deionized water at 22°C and 80°C. At the end of the swelling-pressure test, the hydraulic conductivities of four saturated specimens were measured at each temperature. The volumetric shrinkage strain of the compacted bentonite during desiccation is controlled by suction instead of temperature. In addition, the preliminary desiccation increases both the swelling pressure and hydraulic conductivity of compacted bentonite, particularly if compacted bentonite undergoes extreme desiccation at an applied suction of >700 MPa.

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