Effect of Freeze Pipe Eccentricity in Artificial Ground Freezing Applications

Abstract Building concentric tubes is one of biggest practical challenges in the construction of freeze-pipes of artificial ground freezing (AGF) applications for deep underground mines. In this study, the influence of tubes eccentricity on phase-front expansion (i.e., expansion of the frozen body) and energy consumption of AGF systems is analyzed. A 1+1D semi-conjugate model that solves two-phase transient energy conservation equation is derived. The model is firstly validated against experimental data and then verified with a fully-conjugate model from the literature. After that, the model is extended to a field scale of typical deep underground mines to study freeze-pipe eccentricity. The results show that an eccentric freeze pipe can reduce the phase-front expansion by around 25%, as compared with a concentric one. Also, the geometrical profile of the phase-front is significantly influenced by the freeze-pipe eccentricity. Furthermore, in the passive zone, where AGF coolants are isolated from the ground to reduce energy consumption, freeze pipe eccentricity can increase the coolant heat gain by 10%. This percentage can increase up to 200% if radiation heat transfer is minimized.

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Effect of Freeze Pipe Eccentricity in Selective Artificial Ground Freezing Applications

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4052595 ◽

2021 ◽

pp. 1-33

Author(s):

Ahmad Zueter ◽

Ali Madiseh ◽

Ferri Hassani ◽

Agus Pulung Sasmito

Keyword(s):

Energy Consumption ◽

Radiation Heat Transfer ◽

Conservation Equation ◽

Underground Mines ◽

Frozen Ground ◽

Two Phase ◽

Ground Freezing ◽

1D Model ◽

Artificial Ground Freezing ◽

Conjugate Model

Abstract Building concentric tubes is one of biggest practical challenges in the construction of freeze-pipes of selective artificial ground freezing (S-AGF) applications for underground mines. In this study, the influence of tubes eccentricity on phase-front expansion (i.e., expansion of the frozen body) and energy consumption of S-AGF systems is analyzed. A 1+1D semi-conjugate model that solves two-phase transient energy conservation equation is derived based on the enthalpy method. The 1+1D model is firstly validated against experimental data and then verified with a fully-conjugate model from our previous work. After that, the 1+1D model is extended to a field-scale of typical underground mines to examine the effect of freeze-pipe eccentricity. The results show that concentric freeze-pipes form the desired frozen ground volume 15% faster than eccentric freeze-pipes. Also, the geometrical profile of the phase-transition-front of the frozen ground is found to be significantly influenced by the freeze-pipe eccentricity. Furthermore, in the passive zone, where S-AGF coolants are isolated from the ground to reduce energy consumption, freeze pipe eccentricity can increase the coolant heat gain by 20%. This percentage can increase up to 200 % if radiation heat transfer is minimized.

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Simulation of the Effects of Thermo Insulating Shotcrete on the Energy Consumption of Ventilation and Cooling Systems at Deep Underground Mines

Mine Planning and Equipment Selection ◽

10.1007/978-3-319-02678-7_4 ◽

2014 ◽

pp. 37-42

Author(s):

Derek Apel ◽

Wei Liu ◽

Vivek Bindiganavile

Keyword(s):

Energy Consumption ◽

Underground Mines ◽

Cooling Systems ◽

Deep Underground

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Development of Analytical Solution for a Two-Phase Stefan Problem in Artificial Ground Freezing Using Singular Perturbation Theory

Journal of Heat Transfer ◽

10.1115/1.4048137 ◽

2020 ◽

Vol 142 (12) ◽

Cited By ~ 1

Author(s):

Minghan Xu ◽

Saad Akhtar ◽

Ahmad F. Zueter ◽

Victor Auger ◽

Mahmoud A. Alzoubi ◽

...

Keyword(s):

Analytical Solution ◽

Singular Perturbation ◽

Stefan Problem ◽

Underground Structure ◽

Computational Cost ◽

Singular Perturbation Theory ◽

Singular Perturbation Method ◽

Two Phase ◽

Ground Freezing ◽

Artificial Ground Freezing

Abstract Artificial ground freezing (AGF) has historically been used to stabilize underground structure. Numerical methods generally require high computational power to be applicable in practice. Therefore, it is of interest to develop accurate and reliable analytical frameworks for minimizing computational cost. This paper proposes a singular perturbation solution for a two-phase Stefan problem that describes outward solidification in AGF. Specifically, the singular perturbation method separates two distinct temporal scales to capture the subcooling and freezing stages in the ground. The ground was considered as a porous medium with volume-averaged thermophysical properties. Further, Stefan number was assumed to be small, and effects of a few site-dependent parameters were investigated. The analytical solution was verified by numerical results and found to have similar conclusions yet with much lesser computational cost. Keywords: artificial ground freezing, Stefan-like problems, singular perturbation, porous media, outward solidification.

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