Mine Backfilling in the Permafrost, Part I: Numerical Prediction of Thermal Curing Conditions within the Cemented Paste Backfill Matrix

The mechanical behavior of cemented paste backfill (CPB) in permafrost regions may depend on the thermal curing conditions. However, few experimental data are available for calibrating and validating numerical models used to predict these conditions. To fill this gap, a three-dimensional (3D) laboratory heat transfer test was conducted on CPB placed in an instrumented barrel and cured under a constant temperature of −11 °C. Results were used to calibrate and validate a numerical model built with COMSOL Multiphysics®. The model was then used to predict the evolution of the temperature field for CPB cured under the thermal boundary conditions for a backfilled mine stope in the permafrost (at −6 °C). Numerical results indicated that the CPB temperature gradually decreased with time such that the entire CPB mass was frozen about five years after stope backfilling. However, the permafrost equilibrium temperature of −6 °C was not reached throughout the entire CPB mass even after 20 years of curing. In addition, the evolution of the temperature field in the permafrost rock showed that the thickness of the thawed portion reached about 1 m within 120 days. Afterwards, the temperature continues to drop over time and the thawed portion of the permafrost refreezes after 365 days.

Download Full-text

Solar Radiation-Induced Temperature Variation of Concrete Bridge Piers

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.178-181.2451 ◽

2012 ◽

Vol 178-181 ◽

pp. 2451-2455 ◽

Cited By ~ 1

Author(s):

Bo Chen ◽

Xiu Jin Li ◽

Han Ming Pan ◽

Jin Zheng

Keyword(s):

Temperature Field ◽

Temperature Variation ◽

Numerical Models ◽

Time Instant ◽

Concrete Bridges ◽

Concrete Bridge ◽

Thermal Boundary Conditions ◽

Infrared Imager ◽

Structural Temperature ◽

Radiation Induced

The dynamic temperature field of a concrete pier is actively studied in this study with the aiding of the commercial package ANSYS. Thermal boundary conditions are utilized to obtain the temperature distribution of the concrete bridge pier. The surface temperature of the pier is measured by using a thermal infrared imager at different time instant. The ambient temperature and wind velocity are also collected at the same time. The made observations demonstrate that the simulated temperature variation of the concrete pier agrees well with measurement results. The thermal gradient of the concrete in the thickness direction is a little large. It is seen that the numerical models can successfully predict the structural temperature field at different time. The methodology employed in the paper can be applied to other concrete bridges as well.

Download Full-text

Two Numerical Models for Prediction of an Industrial Concasting Process

Residual Stress, Fitness-For-Service, and Manufacturing Processes ◽

10.1115/pvp2003-2054 ◽

2003 ◽

Author(s):

Frantisek Kavicka ◽

Josef Stetina ◽

Karel Stransky ◽

Jana Dobrovska ◽

Vera Dobrovska ◽

...

Keyword(s):

Temperature Field ◽

Numerical Model ◽

Numerical Models ◽

Three Dimensional ◽

Crystallization Rate ◽

Dendritic Segregation ◽

Distribution Of Elements ◽

Technological Impact ◽

The Mean ◽

Constituent Elements

This paper introduces the application of two three-dimensional (3D) numerical models of the temperature field of a caster. The first model simulates the temperature field of a caster—either as a whole, or any of its parts. Experimental research and data acquisition take place simultaneously with the numerical computation in order to enhance the numerical model and to perfect it in the course of the process. In order to apply the second original numerical model—a model of dendritic segregation of elements—it is necessary to analyze the heterogeneity of samples of the constituent elements and impurities in characteristic places of the solidifying slab. The samples are taken from places, which provide information on the distribution of elements under both standard and extreme conditions for solidification, where the mean solidification (crystallization) rate is known for points between the solidus and liquidus curves. Using this method, it is possible to forecast the occurrence of the critical points of a slab from the viewpoint of its susceptibility to crack and fissure. Verification of the technological impact of optimization, resulting from both models, is conducted on a real industrial caster.

Download Full-text

Transient, Three-Dimensional Numerical Model of a Laser Cutting Process With Phase Change Consideration

Heat Transfer, Volume 2 ◽

10.1115/imece2004-61460 ◽

2004 ◽

Author(s):

Gustavo Gutie´rrez ◽

Juan Guillermo Araya

Keyword(s):

Temperature Field ◽

Laser Beam ◽

Phase Change ◽

Numerical Models ◽

Three Dimensional ◽

Phase Changes ◽

Ceramic Surface ◽

Numerical Predictions ◽

Physical Shape ◽

Finite Volume Approach

Phase change problems are encountered in several manufacturing and material processing applications. Such problems are computationally challenging because it is necessary to solve a non-linear heat conduction equation and take into considerations the conditions needed to produce material ablation, varying continuously the heat source position, thermo physical properties and physical shape of the domain. This research presents a numerical simulation of the temperature field and the removed material resulting from the impingement of a moving laser beam on a ceramic surface. A finite volume approach has been developed to predict the temperature field including phase changes generated during the process. The model considers heat losses by convection and radiation due to the high temperatures involved and uses a coordinate system affixed to the workpiece; therefore no quasi-steady conditions are assumed, as in the majority of previous works. Numerical predictions were compared with former three-dimensional numerical models considering a semi-infinite solid and from experimental data found in the literature. This study gives insight into the interactions between the laser beam and a silicon nitride workpiece during the cutting.

Download Full-text

Investigation of a Temperature Field of the Steel Billet 150x150 mm Continuously Cast

MATEC Web of Conferences ◽

10.1051/matecconf/202032803002 ◽

2020 ◽

Vol 328 ◽

pp. 03002

Author(s):

František Kavička ◽

Jaroslav Katolický ◽

Josef Štětina ◽

Tomáš Mauder ◽

Lubomír Klimeš

Keyword(s):

Mass Transfer ◽

Temperature Field ◽

Numerical Models ◽

Three Dimensional ◽

Cast Billet ◽

Operational Parameters ◽

Measurement Results ◽

Simultaneous Heating ◽

Continuously Cast Billet ◽

Continuously Cast

The solidification and cooling of a continuously cast billet and the simultaneous heating of the mold is a very complicated problem of three-dimensional (3D) transient heat and mass transfer. The solving of uch a problem is impossible without numerical models of the temperature field of the concasting itself which it is being processed through the concasting machine (caster). The application of the numerical model requires systematic experimentation and measurement of operational parameters on a real caster as well as in the laboratory. The measurement results, especially temperatures, serve not only for the verification of the exactness of the model, but mainly for optimization of the process procedure. The most important part of the investigation is the measurement of the temperatures in the walls of the mold and the surface of the slab in the zones of secondary and tertiary cooling.

Download Full-text

Insight into Saturated Hydraulic Conductivity of Cemented Paste Backfill Containing Polycarboxylate Ether-Based Superplasticizer

Minerals ◽

10.3390/min12010093 ◽

2022 ◽

Vol 12 (1) ◽

pp. 93

Author(s):

Sada Haruna ◽

Mamadou Fall

Keyword(s):

Hydraulic Conductivity ◽

Environmental Performance ◽

Mining Industry ◽

Design Criterion ◽

Saturated Hydraulic Conductivity ◽

Curing Temperature ◽

Partial Replacement ◽

Cemented Paste Backfill ◽

Curing Conditions ◽

Paste Backfill

Recycling of tailings in the form of cemented paste backfill (CPB) is a widely adopted practice in the mining industry. Environmental performance is an important design criterion of CPB structures. This environmental performance of CPB is strongly influenced by its saturated hydraulic conductivity (permeability). Superplasticizers are usually added to improve flowability, but there is a limited understanding of their influence on the hydraulic properties of the CPB. This paper presents new experimental results on the variations of the hydraulic conductivity of CPB containing polycarboxylate-based superplasticizer with different compositions and curing conditions. It is found that the hydraulic conductivity of the CPB decreases with the addition of superplasticizer, which is beneficial to its environmental performance. The reduction is largely attributable to the influence of the ether-based superplasticizer on particles mobility and cement hydration. Moreover, both curing temperature and time have correlations with the hydraulic conductivity of CPB containing superplasticizer. In addition, the presence of sulfate and partial replacement of PCI with blast furnace slag reduces the hydraulic conductivity. The variations are mainly due to the changes in the pore structure of the CPB. The new results discussed in this manuscript will contribute to the design of more environmental-friendly CPBs, which is essential for sustainable mining.

Download Full-text

Comparison of Three-Dimensional Multidomain and Single-Domain Models for the Horizontal Solidification Problem

Journal of Heat Transfer ◽

10.1115/1.4033700 ◽

2016 ◽

Vol 138 (11) ◽

Cited By ~ 6

Author(s):

M. H. Avnaim ◽

A. Levy ◽

B. Mikhailovich ◽

O. Ben-David ◽

A. Azulay

Keyword(s):

Numerical Models ◽

Three Dimensional ◽

3D Models ◽

Single Domain ◽

Temperature Fields ◽

Experimental Setup ◽

Mean Velocity ◽

Interface Position ◽

Thermal Boundary Conditions ◽

Vof Model

In this paper, horizontal solidification of gallium in a rectangular cavity was studied both experimentally and numerically. Two three-dimensional (3D) numerical models related to different numerical approaches were built. The first is a single-domain (SD) model based on the volume-of-fluid (VOF) method. This model also takes into account the presence of a mushy zone. The second model is a multidomain (MD) one; it includes two different meshes for the two phases and uses Stephan's boundary condition to determine the front velocity. The 3D models were tested under various thermal boundary conditions and compared with experimental results obtained in an appropriate experimental setup. The experimental setup included an ultrasonic Doppler velocimeter (UDV) for noninvasive measurements of the velocities in the liquid part of the metal, liquid–solid interface position and profile, its displacement, and longitudinal mean velocity. For determining the boundary influence, both 3D and 2D models were built. The comparison was carried out for the solidification front location and shape and the velocity and temperature fields. In general, the 3D numerical model gave more accurate results than the 2D model with respect to the experiments results. Although the MD model is more complicated to build and requires more computational efforts than the VOF model, the 3D MD model provides the most accurate results in comparison with current experiments.

Download Full-text