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.

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.

scholarly journals Fractal study in soil spatial variability and thermal conductivity

2019 ◽  
Vol 23 (5 Part A) ◽  
pp. 2849-2856
Author(s):  
Jingfang Shen ◽  
Xu Zhang ◽  
Wenwei Liu ◽  
Ying Zhang
Keyword(s):  
Thermal Conductivity ◽  
Spatial Variability ◽  
Effective Thermal Conductivity ◽  
Multifractal Spectrum ◽  
Coarse Sand ◽  
Soil Thermal Conductivity ◽  
Sierpinski Carpet ◽  
Fractal Method ◽  
Scatter Plots ◽  
Sierpiński Carpet

This paper takes advantage of fractal method to research some soil characteristics through case analysis. The multifractal spectrum and random Sierpinski carpet are used to describe the spatial variability and thermal conductivity of soil quantitatively. On the basis of predecessors, the scatter plots of various types of data have been used to supplement the multifractal results in a more detailed way. It turns out that the content of clay, silt, and coarse sand could reflect the degree of spatial variability of soil. Then based on this case, the effect of porosity on soil thermal conductivity is discussed by using random Sierpinski carpet. The result shows that the effective thermal conductivity of the clay, silt and coarse sand decreases linearly with the increase of porosity, but the degree of reduction is different. Moreover, when the porosity is definite, the effective thermal conductivity of the coarse sand is the largest, that of the clay with the highest thermal conductivity is second, and that of the silt is the smallest.

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.

Numerical Analysis and Spot-Survey Study of Horizontal Artificial Ground Freezing in Tunnel Connecting Passage Construction

2015 ◽  
Vol 744-746 ◽  
pp. 969-977
Author(s):  
Feng Tian Yue ◽  
Shan Guo Lv ◽  
Rong Jian Shi ◽  
Yong Zhang ◽  
Lu Lu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Field Survey ◽  
Temperature Fields ◽  
Survey Study ◽  
Freezing Process ◽  
Road Tunnel ◽  
Element Analysis ◽  
Ground Freezing ◽  
Artificial Ground Freezing

In this paper, a comprehensive method combined spot-survey and numerical simulation tests has been used to make an approach to systematically study of the technology of level artificial ground freezing in tunnel connecting passage construction. By simulating the freezing process of artificially frozen soils of Dalian Road tunnel connecting passage with finite element analysis method, the varying laws of temperature fields, displacement fields and stress fields had been worked out. According to the results of actual field survey, the changing laws of frost heave pressure and tunnel deformation with freezing temperature, elapsed freezing time during the artificial ground freezing period are obtained. The laws from finite element analysis are consistent with that from field survey, which has proved that finite element analysis is correct. The conclusions of the research prove the advantages of horizontal artificial ground freezing in such similar construction and set up a successful model for related freezing projects in the future, which, will guide the coming practice and safeguard the success.

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