compaction rate
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2021 ◽  
Vol 1 ◽  
pp. 121-123
Author(s):  
Larissa Friedenberg ◽  
James Bean ◽  
Oliver Czaikowski ◽  
Uwe Düsterloh ◽  
Nina Müller-Hoeppe ◽  
...  

Abstract. In Germany, rock salt formations are possible host rock candidates for a repository for heat-emitting radioactive waste. The safety concept of a repository in salt bases on a multibarrier system consisting mainly of the geological barrier salt and geotechnical seals ensuring safe containment. Crushed salt will be used for backfilling of cavities and sealing measures in drifts and shafts due to its favourable properties and its easy availability (mined-off material). The creep of the rock salt leads to crushed salt compaction with time. Thereby, the crushed salts' porosity is reduced from the initial porosity of 30 %–40 % to a value comparable to the porosity of undisturbed rock salt (≤1 %). In such low porosity ranges, technical impermeability is assumed. The compaction behaviour of crushed salt is rather complex and involves several coupled THM processes (Kröhn et al., 2017; Hansen et al., 2014). It is influenced by internal properties like humidity and grain size distribution, as well as boundary conditions such as temperature, compaction rate or stress state. However, the current process understanding has some important gaps referring to the material behaviour, experimental database and numerical modelling. It needs to be extended and validated, especially in the low porosity range. The objective of the KOMPASS project was development of methods and strategies for the reduction of deficits in the prediction of crushed salt compaction leading to an improvement of the prognosis quality. Key results are as follows (KOMPASS Phase 1, 2020): selection of an easily available and permanently producible synthetic crushed salt mixture, acting as a reference material for generic investigations; development and proof of different techniques for producing pre-compacted samples for further investigations; establishment of a tool of microstructure investigation methods to demonstrate the comparability of grain structures of pre-compacted samples with in-situ compacted material for future investigations; execution of various laboratory experiments using pre-compacted samples, e.g. long-term creep tests which deliver reliable information about time- and stress-dependent compaction behaviour; development of a complex experimental investigation strategy to derive necessary model parameters considering individual functional dependencies. Its technical feasibility was successfully verified; benchmarking with various existing numerical models using datasets from three different triaxial long-term tests. The result was not entirely satisfactory; however, the number of influencing factors is small and further validation work has to be done. Overall, the KOMPASS project has made significant progress in the approaches to solving the outstanding question, building the basis for further investigations.


Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2009
Author(s):  
Dominik Mayer ◽  
Ann-Kathrin Wurba ◽  
Benjamin Bold ◽  
Jonathan Bernecker ◽  
Anna Smith ◽  
...  

Battery cell production is a complex process chain with interlinked manufacturing processes. Calendering in particular has an enormous influence on the subsequent manufacturing steps and final cell performance. However, the effects on the mechanical properties of the electrode, in particular, have been insufficiently investigated. For this reason, the impact of different densification rates during calendering on the electrochemical cell performance of NMC811 (LiNi0.8Mn0.1Co0.1O2) half-cells are investigated to identify the relevant calendering parameters. Based on this investigation, an experimental design has been derived. Electrode elongations after calendering in and orthogonal to the running direction of the NMC811 cathode are investigated in comparison with a hard carbon anode after calendering. Elongations orthogonal to the machine direction are observed to have no major dependencies on the compaction rate during calendering. In the machine direction, however, significant elongation occurs as a dependency of the compaction rate for both the hard carbon anode and the NMC811. In addition, the geometric shape of the NMC811 electrodes after separation into individual sheets is investigated with regard to different compaction rates during calendering. It is shown that the corrugations that occur during calendering are propagated into the single electrode, depending on the compaction rate.


2021 ◽  
Vol 8 ◽  
Author(s):  
Yue Dong ◽  
Xinguo Zhang ◽  
Jia Lin ◽  
Jinhai Zhao ◽  
Zixuan Meng

The coal mining technology of fully mechanized solid filling is an efficient and green mining method that integrates “sediment reduction” and “emission reduction.” However, the discharge of wasted gangue and surface subsidence are controlled by the amount of wasted gangue used in filling mining and the compaction rate of gangue filled into a goaf, respectively. To increase the consumption of wasted gangue and reduce surface subsidence, mixed gangue composed of equal-quality washed gangue and crushed gangue is proposed as a raw material for solid filling on the basis of gradation theory. Next, a screening experiment was performed to analyze the grain gradation of different specimens, and a compression experiment was executed to compare and analyze the compression characteristics. The results show that the nonuniformity coefficient of mixed gangue is 55.2 and the curvature coefficient is 1.53, which significantly improve the grain gradation of washed gangue. The degree of relative compaction of mixed gangue is 1.226, which is significantly lower than that of washed gangue, which is 1.33. The deformation modulus of mixed gangue is 23–135 MPa, which is better than that of washed gangue (26–100 MPa), indicating that the compressive resistance of mixed gangue is significantly improved. The case study of the Tangkou mine suggests that mixed gangue greatly promotes the consumption of wasted gangue and can effectively control the surface deformation.


2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Eluozo S.N. ◽  
Dimkpa K

This paper monitors the growth rate of tensile strength under partial replacement of locally sourced materials, the study monitor the behaviour of tensile between seven and  twenty eight days of optimum curing age,  modeling and simulation were applied in the study, whereby parameters that generate the attained tensile strength from self compacting concrete were monitored considering various factors such as variation of compaction and water cement ratio, the reaction of these parameters were examined in the study through the simulation, the reflection of these parameters influence where observed in all the trend, the study examined the level of significances of tensile on concrete structure, therefore try to evaluate  various reflection effect from permeability and other parameters that were not considered in  experimental process, these are  developed from  self compacting concrete partially replace cement with fly ash and wood.  Tensile strength is an important property of concrete due its level of vulnerability to tensile cracking base on different kind of applied loading itself. The influence of permeability as a physical property has definitely affect the durability of concrete, these  where observed on the its reflection on tensile strength in all the trend, the rate of permeability effect on tensile were monitored to reflect its reaction through microstructural perspective influence from porosity, pore size, connectivity including its rates of bonding, these correlation includes  air content and capillarity, there rate of permeability coefficient on its reduction are determined by the decrease in porosity and void ratios from concrete compaction rate, it is  reflected on  its variation  of tensile strength in self compacting concrete, the rate of permeability reducing at constant rates determined the tensile strength through it microstructural  setting on the self compacting concrete, these condition were applied on the simulation to generates the predictive values compared with experimental values by an expert [22], while an improvement were made on it study, these include monitoring of concrete permeability and void ratios effect on tensile, the behaviour of porosity under the influence of permeability and variation concrete void were examined from the permeability influence on tensile strength.


2021 ◽  
Vol 176 (4) ◽  
Author(s):  
Giuliano Krättli ◽  
Max W. Schmidt

AbstractCentrifuge-assisted piston cylinder experiments were conducted on plagioclase in basaltic melt at 1140–1250 °C, 0.42–0.84 GPa and mostly 1000 g. One set of experiments assesses the settling velocity of a dilute plagioclase suspension; a second sinks or floats plagioclase in a MORB-type melt exploring conditions of neutral buoyancy; and a third set examines floatation of plagioclase from an evolved lunar magma ocean composition. A compaction rate for plagioclase cumulates is established. The experiments demonstrate that neutral density of plagioclase An74 in a MOR-type tholeiitic basalt occurs at 0.59 ± 0.04 GPa (1200 °C), contrasting predictions by present models on melt density which yield a density inversion pressure at 0.10–0.15 GPa. In nature, the level of neutral buoyancy depends on melt composition; nevertheless, for the onset of plagioclase crystallization in dry tholeiitic basalts, our result is robust. As the molar volume of plagioclase is well known, the experimentally determined pressure of neutral buoyancy indicates a correction of -1.6% to previous density models for silicate melts. It follows that for (tholeiitic) layered mafic intrusions, plagioclase is negatively buoyant for early, relatively primitive, parent melts. In contrast, the extreme Fe enrichment of a fractionating lunar magma ocean leads to melt densities that let anorthite always float. Compaction φ/φ0 of experimental plagioclase cumulates is quantified to φ/φ0 = − 0.0582 log (Δρ·h·a·t) + 1.284, where φ0 is the porosity after settling (67 ± 2%), h the cumulate pile height, a acceleration and φ porosity as a function of time t. Gravitational-driven compaction in tens of m-thick plagioclase cumulate in basaltic magmas reaches down to ~ 40% porosity within hundreds of years, a timescales competing with characteristic cooling times of cumulate layers of mafic intrusions. To achieve plagioclase modes > 80% due to compaction, an additional overload of ~ 100 m (layers) of mafic minerals would be required. Compaction of a lunar anorthosite crust of 35 km to 20% porosity (i.e. ~ 90% plagioclase after crystallization of the interstitial melt) would require 30 kyrs.


2021 ◽  
Author(s):  
A. Aulia Valencia ◽  
J.E.A. (Joep) Storms ◽  
Dirk-Jan Walstra ◽  
Helena van der Vegt ◽  
H.R.A. (Bert) Jagers

<p>Only a limited amount of data is available to quantify the impact of syn-depositional compaction on delta depositional patterns. In this study, we investigate numerically how different scenarios for compaction rate (0 - 10 mm yr<sup>-1</sup>) drives morphological variations in mud- and sand-rich fluvial-dominated deltas. To do this, a 1D grain-size dependent compaction model was implemented into the open-source Delft3D. This implementation allows deposited sediment to decrease in thickness over time due to the accumulation of newly deposited sediments above. The resultant sedimentary deposits of a prograding delta are post-processed to highlight the changes in depositional patterns under different compaction scenarios. Deposits are classified into sub-environment (e.g., delta top, delta front, and pro delta). The delta top geometry (e.g., area, shape, and rugosity) and the distribution of sediment between different sub-environments are compared. The modeling results verify that the larger compaction-induced subsidence affects accommodation provision. We show that this results in more significant sediment deposition and more evenly distributed sediment across the delta top. Larger compaction results in a smaller area with a more semi-circular shape and less rugose delta top. The modeling results presented here bridges the knowledge gap on the effects of syn-depositional compaction on delta morphology evolution.</p>


2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Chao Ma ◽  
Lianying Zhang ◽  
Bing Li ◽  
Xianbiao Mao

Solid backfill mining is an efficient and environmental-friendly coal mining technology, which can effectively solve the problems of coal gangue pollution, water resource loss, and surface subsidence. Based on the mechanical behavior of backfill materials in the compaction process, volume strain was used to express the deformation modulus, and a constitutive model of backfill materials was proposed in this study. The ABAQUS UMAT was used to develop the numerical calculation subroutine of the model. Finally, the rationality of the model was verified that simulated stress-strain curves of the backfill materials during the compaction process agree well with experiments. Based on the proposed constitutive model, the influence of three factors (the initial compaction rate of the filling body, the mining height, and the mining depth) on the key strata and surface subsidence was analyzed systematically. The results show that the initial compaction rate and the height of coal seams have significant influences on surface subsidence. When the thickness of topsoil is only changed and the structural composition and lithology of overburden are not changed, the mining depth has little influence on surface subsidence, but a significant influence on surface subsidence range. The influence of mining height and mining depth on the deformation of key strata of overburden and surface subsidence is approximately linear, while the influence of the initial compaction rate is nonlinear.


2021 ◽  
Vol 2 ◽  
Author(s):  
Cedrick Victoir Guedessou ◽  
Jean Caron ◽  
Jacques Gallichand ◽  
Moranne Béliveau ◽  
Jacynthe Dessureault-Rompré ◽  
...  

Reclaiming histosols in Montéregie region, Québec, Canada, increases peat decomposition and compaction rate and decreases the effectiveness of subsurface drainage. The objective of this paper was to use HYDRUS-2D to model the behavior of subsurface drainage systems, in order to evaluate the compaction effect on drain depth and spacing, and to determine the compact layer thickness and saturated hydraulic conductivities (Ksat) resulting in an improvement of subsurface drainage]. The drainage model was calibrated [Nash-Sutcliffe efficiency coefficient (NSE) = 0.958, percent bias (PBIAS) = −0.57%] using Ksat, meteorological data, and matric potential (h) data measured on the project site from June 10 to July 19, 2017. The calibrated and validated model was used to analyze the variation of h values (Δh in cm d−1) as a function of drain spacing (2–7 m) and drain depth (1 and 1.2 m) and to identify the response surface of Δh to various compact layer thickness and Ksat combinations. The results showed that Δh was on average 58% greater below the compact layer than above it and that reducing drain spacing or increasing drain depth does not improve the drainage rate. The analysis of the compact layer thickness and Ksat effect on Δh showed that for a Δh of 40 cm d−1, Ksat actual values in the two uppermost layers should be multiplied by 50 for compact layer thickness varying from 12 to 35 cm. Water percolation in the soil is reduced by the compact layer. Soil management methods for improving Ksat should therefore be better than deepening the drains or and reducing the spacing.


2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Feng Chen ◽  
Shenghao Tong

Over the past few years, soil-cement has been widely used in marine geotechnical engineering; meanwhile, the safety of soil-cement in marine environment has attracted wide attention. In order to study the influence of composite ferronickel slag powder on the strength and micro morphology of soil-cement in marine environment, the composite nickel iron slag powder was added into the soil-cement in this paper. The unconfined compressive strength test, erosion resistance coefficient analysis, SEM, and EDS test analysis of soil-cement were carried out.. Results showed that the marine environment had great influences on the strength of soil-cement, and the addition of compound nickel-iron slag powder can enhance the strength of soil-cement, and the deterioration of the strength of soil-cement is reduced. In addition, the compound ferronickel slag powder has microaggregate effect, morphological effect, and activation effect, which not only improves compaction rate of soil-cement and prevents invasion of erosive ions in marine environment but also has positive effects on the performance of soil-cement.


2019 ◽  
Vol 970 ◽  
pp. 265-275
Author(s):  
Anatoly P. Surzhikov ◽  
Andrey V. Malyshev ◽  
Anna B. Petrova ◽  
Elena A. Sheveleva

The effect of intensification of the compaction rate of ferrite compacts under irradiation conditions with a high-power electron beam both in the heating regime and in the isothermal stage of sintering was established. The compaction mechanisms of the compacts are different at each of these stages. The intensification of compaction at the non-isothermal stage in radiation-thermal conditions is due to processes involving the liquid phase. The role of bismuth oxide in the compaction of the material at the isothermal stage of sintering is unessential, but its influence is significant in recrystallization processes. Under of Ivensen’s phenomenology, compaction curves are explained by the deceleration of annealing of structural defects responsible for the fluidity of the material. Dislocations are the most probable type of defects, satisfying the detected regularities.


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