SIMPLIFICATION POSSIBILITIES FOR COUPLED THM MODELS OF ARTIFICIAL GROUND FREEZING IN THE CONSTRUCTION OF MINE SHAFTS

2021 ◽  
Vol 4 (1) ◽  
pp. 453-463
Author(s):  
M. A. Semin ◽  
Keyword(s):  
Mechanical Model ◽  
Soil Freezing ◽  
Underground Structures ◽  
Physical Processes ◽  
Reasonable Degree ◽  
Ground Freezing ◽  
The Media ◽  
Artificial Ground Freezing ◽  
Frozen Wall ◽  
The Relationship

An important stage in the design of the artificial ground freezing during the construc-tion of mine shafts (and other underground structures) is the simulation of deformation and heat transfer in the media to be frozen. This is necessary to calculate the required thicknesses of frozen wall, the time of its formation and the parameters of freezing stations. The choice of an adequate mathematical model is impossible without analyzing the significance and coupling of various physical processes occurring during the freezing of soil. Such an analysis allows se-lecting a reasonable degree of detailing of physical processes in the model: take into account all important factors and neglect the rest. This article proposes a methodology for analyzing the significance and coupling of such physical processes. For this, a general thermo-hydro-mechanical model of soil freezing has been formulated, a set of dimensionless complexes has been identified and classified, which determine the relationship between various physical pro-cesses. The transition from the general thermo-hydro-mechanical model to simpler models is possible only if the corresponding dimensionless complexes are small.

THE APPLICA TION OF "FROZEN WALL " SOFTWARE IN SIMULA TION OF ARTIFICIAL GROUND FREEZING

2019 ◽  
Vol 4 (1) ◽  
pp. 269-282
Author(s):  
L.Y. Levin ◽  
◽  
M.A. Semin ◽  
A.V. Bogomyagkov ◽  
O.S. Parshakov ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Numerical Solution ◽  
General Information ◽  
Software Application ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Frozen Wall ◽  
The Mathematical Model ◽  
Best Fit ◽  
Technical Measures

The paper presents general information about the software application “Frozen Wall ”, which was designed to simulate frozen wall formation around constructed vertical shafts. The main feature of the developed application is the possibility of calibrating the mathematical model for the best fit with the experimental temperature measurements by numerical solution of the inverse Stefan problem. In addition, it takes into account a number of technological processes that affect the state of the frozen wall. Based on calculations performed in the application, it is possible to develop technical measures aimed at ensuring the efficiency of mine shafts construction in difficult hydrogeological conditions.

Development and Validation of Enthalpy-Porosity Method for Artificial Ground Freezing Under Seepage Conditions

2018 ◽  
Author(s):  
Mahmoud A. Alzoubi ◽  
Agus P. Sasmito
Keyword(s):  
Seepage Flow ◽  
High Water ◽  
Flow Conditions ◽  
Ground Structure ◽  
Reliable Prediction ◽  
Closure Time ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Frozen Wall ◽  
Development And Validation

Groundwater flow has an undesirable effect on ice growth in artificial ground freezing (AGF) process: high water flow could hinder the hydraulic sealing between two freeze pipes. Therefore, a reliable prediction of the multiphysics ground behavior under seepage flow conditions is compulsory. This paper describes a mathematical model that considers conservation of mass, momentum, and energy. The model has been derived, validated, and implemented to simulate the multiphase heat transfer between freeze pipes and surrounded porous ground structure with and without the presence of groundwater seepage. The paper discusses, also, the influence of the coolant’s temperature, the spacing between two freeze pipes, and the seepage temperature on time needed to create a closed, frozen wall. The results indicate that spacing between two pipes and seepage velocity have the highest impact on the closure time and the frozen body width.

Prediction and Improvement of Artificial Ground Freezing

2005 ◽  
Author(s):  
M. Yokoo ◽  
M. Shibazaki ◽  
H. Yoshida ◽  
H. Souma ◽  
A. Ousaka ◽  
...  
Keyword(s):  
Numerical Model ◽  
Numerical Solutions ◽  
Physical Property ◽  
Flow Speed ◽  
Soil Freezing ◽  
Physical Parameters ◽  
Interface Growth ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Water Saturated

The aim of present study is to establish the numerical model for the solidification or melting of water saturated soil and to clarify the effect of thermal and physical parameters on the artificial soil freezing by comparing between the numerical and experimental results. First, the numerical model has been modified to adapt for freezing of soil. By comparing between obtained numerical solutions and experimental data, the validity of the model has been checked and certified. Next, the effect of physical property of soil, initial and boundary conditions of soil and freezing pipes, the velocity of groundwater, and the arrangement of freezing pipes on soil freezing have been examined. As the results, it was found that the water content of soil and ground water affect the volume of solid, besides the groundwater also especially changes the profile of solid/liquid interface. The rate of the interface growth would gradually stop provided that the flow speed exceeds certain limits. The knowledge obtained from our study will be useful to predict solid volume, decrease in thermal energy consumption and minimize the influence to ambience on artificial ground freezing precisely.

scholarly journals A Field Study on the Freezing Characteristics of Freeze-Sealing Pipe Roof Used in Ultra-Shallow Buried Tunnel

2019 ◽  
Vol 9 (8) ◽  
pp. 1532 ◽  
Author(s):  
Xiangdong Hu ◽  
Yuanhao Wu ◽  
Xinyi Li
Keyword(s):  
Large Diameter ◽  
Frozen Soil ◽  
Primary Role ◽  
Steel Pipes ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Design Requirements ◽  
Frozen Wall ◽  
Two Stages ◽  
Shallow Buried Tunnel

A new pre-supporting technology named the freeze-sealing pipe roof (FSPR) method was adopted in the construction of Gongbei tunnel (Zhuhai, China), a critical part of the Hong Kong–Zhuhai–Macau bridge (HZMB) project. The method combined pipe-roofing with artificial ground freezing (AGF). The pipe roof which included a number of large-diameter steel pipes was designed to play a primary role in load bearing, while the frozen wall between pipes was designed for water sealing. The refrigeration proceeded in two stages called the active freezing period and excavation period. This paper mainly focuses on the freezing characteristics of FSPR to explore how the frozen soil wall developed and changed over time during both periods based on field temperature data. The results show that the development of the frozen wall met the design requirements in fewer than 80 days of refrigeration considering the most unfavorable situation. The distribution of frozen soil along the entire tunnel was non-uniform. Frost heave and thaw weakening problems should be taken into account, since some of the bottom section of the frozen wall was more than 3 m. The frozen soil at the excavation side was visibly influenced by the replenishment of heat due to excavation, while the frozen soil outside the excavation face was much less influenced. The thermal effects of Hurricane Nicole on the frozen soil wall was also observed. The conclusions provide experience, reference, and guidance for the development of similar projects in the future.

scholarly journals Modeling Artificial Ground Freezing for Construction of Two Tunnels of a Metro Station in Napoli (Italy)

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1272 ◽  
Author(s):  
Alessandro Mauro ◽  
Gennaro Normino ◽  
Filippo Cavuoto ◽  
Pasquale Marotta ◽  
Nicola Massarotti
Keyword(s):  
Cross Sections ◽  
Coolant Fluid ◽  
Freezing Process ◽  
Metro Station ◽  
Ground Freezing ◽  
Excavation Process ◽  
Artificial Ground Freezing ◽  
Frozen Wall ◽  
Underground Station ◽  
The Stability

An artificial ground freezing (AGF) technique in the horizontal direction has been employed in Naples (Italy), in order to ensure the stability and waterproofing of soil during the excavation of two tunnels in a real underground station. The artificial freezing technique consists of letting a coolant fluid, with a temperature lower than the surrounding ground, circulate inside probes positioned along the perimeter of the gallery. In this paper, the authors propose an efficient numerical model to analyze heat transfer during the whole excavation process for which this AGF technique was used. The model takes into account the water phase change process, and has been employed to analyze phenomena occurring in three cross sections of the galleries. The aim of the work is to analyze the thermal behavior of the ground during the freezing phases, to optimize the freezing process, and to evaluate the thickness of frozen wall obtained. The steps to realize the entire excavation of the tunnels, and the evolution of the frozen wall during the working phases, have been considered. In particular, the present model has allowed us to calculate the thickness of the frozen wall equal to 2.1 m after fourteen days of nitrogen feeding.

scholarly journals Modeling Seepage Flow and Spatial Variability of Soil Thermal Conductivity during Artificial Ground Freezing for Tunnel Excavation

2021 ◽  
Vol 11 (14) ◽  
pp. 6275
Author(s):  
Pu Qiu ◽  
Peitao Li ◽  
Jun Hu ◽  
Yong Liu
Keyword(s):  
Thermal Conductivity ◽  
Spatial Variability ◽  
Seepage Flow ◽  
Freezing Time ◽  
Soil Thermal Conductivity ◽  
Element Analysis ◽  
Rule Of Thumb ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Frozen Wall

Artificial ground freezing (AGF) technology has been commonly applied in tunnel construction. Its primary goal is to create a frozen wall around the tunnel profile as a hydraulic barrier and temporary support, but it is inevitably affected by two natural factors. Firstly, seepage flows provide large and continuous heat energy to prevent the soil from freezing. Secondly, as a key soil parameter in heat transfer, the soil thermal conductivity shows inherent spatial variability, binging uncertainties in freezing effects and efficiency. However, few studies have explored the influence of spatially varied soil thermal conductivity on AGF. In this study, a coupled hydro-thermal numerical model was developed to examine the effects of seepage on the formation of frozen wall. The soil thermal conductivity is simulated as a lognormal random field and analyzed by groups of Monte-Carlo simulations. The results confirmed the adverse effect of groundwater flow on the formation of frozen wall, including the uneven development of frozen body towards the downstream side and the higher risk of water leakage on the upstream face of the tunnel. Based on random finite element analysis, this study quantitively tabulated the required additional freezing time above the deterministic scenario. Two levels of the additional freezing time are provided, namely the average level and conservative level, which aim to facilitate practitioners in making a rule-of-thumb estimation in the design of comparable situations. The findings can offer practitioners a rule of thumb for estimating the additional freezing times needed in artificial ground freezing, accounting for the seepage flow and spatial variation in soil thermal conductivity.

scholarly journals Numerical simulation of vertical shaft sinking using artificial ground freezing

2021 ◽  
Vol 266 ◽  
pp. 03008
Author(s):  
M.S. Zhelnin ◽  
A.A. Kostina ◽  
O.A. Plekhov ◽  
L.Y. Levin
Keyword(s):  
Numerical Simulation ◽  
Soil Freezing ◽  
Design Parameters ◽  
Freezing Process ◽  
Vertical Shaft ◽  
Ground Freezing ◽  
Shaft Sinking ◽  
Artificial Ground Freezing ◽  
Ice Content ◽  
Fully Coupled

Artificial ground freezing (AGF) is used worldwide for vertical shaft sinking in difficult hydrogeological conditions. The modern tendency is to determine the design parameters of the freezing technique based on numerical simulation. This work is devoted to the numerical simulation of the formation of an ice-soil wall in the soil stratum due to the AGF and shaft sinking under the protection of the wall. For this purpose, a fully coupled thermo-hydro-mechanical model of soil freezing has been developed on the basis of the theory of poromechanics. The developed model considers important features of the freezing process, such as the phase change, pore water migration due to cryogenic suction, frost heave, and consolidation of the soil. The results have shown that the model allows to predict the distribution of ice content, assess stress and strain in the ice-soil wall, and estimate displacement of the excavation wall.

scholarly journals Case Study of Heat Transfer during Artificial Ground Freezing with Groundwater Flow

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1322 ◽  
Author(s):  
Rui Hu ◽  
Quan Liu ◽  
Yixuan Xing
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Numerical Model ◽  
Groundwater Flow ◽  
Average Temperature ◽  
Closure Time ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Frozen Wall ◽  
Groundwater Flow Field

For the artificial ground freezing (AGF) projects in highly permeable formations, the effect of groundwater flow cannot be neglected. Based on the heat transfer and seepage theory in porous media with the finite element method, a fully coupled numerical model was established to simulate the changes of temperature field and groundwater flow field. Firstly, based on the classic analytical solution for the frozen temperature field, the model’s ability to solve phase change problems has been validated. In order to analyze the influences of different parameters on the closure time of the freezing wall, we performed the sensitivity analysis for three parameters of this numerical model. The analysis showed that, besides the head difference, the thermal conductivity of soil grain and pipe spacing are also the key factors that control the closure time of the frozen wall. Finally, a strengthening project of a metro tunnel with AGF method in South China was chosen as a field example. With the finite element software COMSOL Multiphysics® (Stockholm, Sweden), a three-dimensional (3D) numerical model was set up to simulate the change of frozen temperature field and groundwater flow field in the project area as well as the freezing process within 50 days. The simulation results show that the freezing wall appears in an asymmetrical shape with horizontal groundwater flow normal to the axial of the tunnel. Along the groundwater flow direction, freezing wall forms slowly and on the upstream side the thickness of the frozen wall is thinner than that on the downstream side. The actual pipe spacing has an important influence on the temperature field and closure time of the frozen wall. The larger the actual pipe spacing is, the slower the closing process will be. Besides this, the calculation for the average temperature of freezing body (not yet in the form of a wall) shows that the average temperature change of the freezing body coincides with that of the main frozen pipes with the same trend.

Artificial Ground Freezing for Rehabilitation of Tunneling Shield in Subsea Environment

2013 ◽  
Vol 734-737 ◽  
pp. 517-521 ◽  
Author(s):  
Xiang Dong Hu ◽  
Luo Yu Zhang
Keyword(s):  
Strength Loss ◽  
Frozen Soil ◽  
Special Design ◽  
Ground Freezing ◽  
Subsea Tunnel ◽  
Artificial Ground Freezing ◽  
Frozen Wall ◽  
Cutter Head ◽  
Limited Depth ◽  
Tunneling Shield

Artificial ground freezing method was employed in the rehabilitation project of a subsea tunnel. To ensure safety of the subsea rehabilitation work, special design and research were conducted considering the unfavorable influence of the salt in seawater had on freezing effect, such as thickness thinning and strength loss of the frozen wall. A shell-shaped frozen soil wall was designed to cut off the leakage channel into the shield. Double rows of vertical freezing pipes with limited-depth freezing were settled in front of the cutter head, and auxiliary freezing pipes were settled at the sides of the shield to achieve the design goal. Results of analyzing monitoring data on frozen soil temperature showed that the design was reasonable for shield rehabilitation in subsea stratum.

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