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 In situ monitoring of frost heave pressure during cross passage construction using ground-freezing method

2016 ◽  
Vol 53 (3) ◽  
pp. 530-539 ◽  
Author(s):  
Lei Han ◽  
Guan-lin Ye ◽  
Yuan-hai Li ◽  
Xiao-he Xia ◽  
Jian-hua Wang
Keyword(s):  
Pressure Gauge ◽  
Earth Pressure ◽  
In Situ Monitoring ◽  
Frost Heave ◽  
Freezing Process ◽  
Groundwater Levels ◽  
Freezing Method ◽  
Ground Freezing ◽  
Artificial Ground Freezing

The artificial ground-freezing method has the dual effect of ground reinforcement and waterproof sealing, and the frozen curtain can be designed flexibly. It is widely used in the construction of cross passages for shield tunnels in soft ground with high groundwater levels. However, due to the lack of in situ monitoring data, it remains difficult to determine the frost heave pressure acting upon a tunnel. In this study, based on the use of an anti-freezing pad-type earth pressure gauge, in situ monitoring was carried out to measure the frost heave pressure acting upon tunnel segments during the construction of cross passages for the Shanghai Yangtze River Tunnel. The monitoring results show that the earth pressure acting upon the tunnel could decrease dramatically during freezing, and this kind of decrease can take place suddenly and unpredictably, which can be illustrated using the finite element method. The maximum measured frost heave pressure during freezing and cross passage excavation was approximately 0.2 MPa, which was much smaller than the predicted value. Combining the distribution of temperature in the ground and construction countermeasures, the observed phenomena are mainly related to three factors: water migration during the freezing process, the tunnel–ground interaction, and the countermeasure of pressure release holes. The tunnel showed a horizontal extension–deformation, which was consistent with the releasing frost heave pressure acting upon it.

Optimization of Double-Ring-Pipe Freezing Scheme for Tunnel Cross-Passage Construction

2012 ◽  
Vol 446-449 ◽  
pp. 2262-2266 ◽  
Author(s):  
Xiang Dong Hu ◽  
Bing Yi Ji
Keyword(s):  
Frozen Soil ◽  
Shield Tunnel ◽  
Freezing Process ◽  
Unfrozen Water ◽  
Double Ring ◽  
Average Temperature ◽  
Unfrozen Water Content ◽  
Ground Freezing ◽  
Different Temperatures ◽  
Frozen Wall

For numerically simulating the phase change of water in ground freezing process, a correct method is proposed in this paper, that the unfrozen water content in frozen soil is taken into account to calculate the enthalpy value at different temperatures. A calculation example of a cross-passage project in shield tunnel shows that the thickness and the average temperature of the frozen wall calculated by this method are very close to the in-situ monitored data. Based on this method, by comparison of the development rate of thickness and the average temperature of the frozen wall according to different design plans, the ground freezing scheme for the cross-passage is optimized for the shortest duration of freeze in agreement with the work standard. The study could enlighten the design for similar projects in the future.

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.

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.

Study on Site Measurement of Freezing Soft Aquifer in Cretaceous Strata

2013 ◽  
Vol 774-776 ◽  
pp. 771-774
Author(s):  
Tie Qi Zheng ◽  
Hua Jun Xue ◽  
Jun Chen ◽  
Ming Nan Ji ◽  
Zeng Lin Zhen
Keyword(s):  
Frozen Soil ◽  
Operating Conditions ◽  
Freezing Process ◽  
Refrigeration System ◽  
Ground Freezing ◽  
Complex Process ◽  
Geological Conditions ◽  
Efficient Construction ◽  
Artificial Ground Freezing ◽  
System Operating

Artificial ground freezing is a time-varying dynamic and complex process. Traits of the frozen soil wall are influenced by the refrigeration system operating conditions, geological conditions, boundary cooling, construction conditions and many other factors. Nature of the frozen soil and the structural state of the frozen soil wall is a function of temperature, yet the temperature field of the frozen soil wall is changing with time. Further, it has a bad influence on the buildings nearby when Frost-heaving and Thawing-settlement happened during freezing process. it will be necessary to comprehend their real-time settlement and deformation as well as to keep sure the frozen soil wall and the buildings nearby are on regular service. The Lindong mine wellbore is located in the Cretaceous Stratum. A information technology of freezing construction method is used to ensure the safe and efficient construction of the wellbore. It made a great contribution to the lingdong mine yielding and other similar projects.

A Space-Time-Dependant Design Method and the Stability of Ice Wall for Deep Shafts

2012 ◽  
Vol 204-208 ◽  
pp. 3275-3281
Author(s):  
Xiang Sheng Chen
Keyword(s):  
Design Method ◽  
Space Time ◽  
Ground Freezing ◽  
Creep Characteristics ◽  
Testing Data ◽  
Artificial Ground Freezing ◽  
Frozen Clay ◽  
The Stability ◽  
New Equation ◽  
Separated Variables

The mechanical properties of artificial frozen soils are the key for application of artificial ground freezing, (AGF) especially the creep characteristics of artificial frozen clay when a deep shaft is sunk by using AGF. Many catastrophic accidents took place in clay strata in deep freezing shafts past because of freezing tube breaking and flooding through ice wall caused by large creep deformation of ice wall. A new creep constitutive equation with separated variables for artificial frozen clay, after C. C. Vialov, is presented on base of testing data of most kinds of artificial frozen clay under the condition of drained system. On base of the new equation, a space-time- dependant design method, a modified C. C. Vialov’s, is proposed and has been successfully used for ice wall of deep shafts all over China since 1996. Finally, the stability of ice wall for deep shafts can economically and efficiently be controlled by adjusting the variables of temperature T, un-supported height h and time elapsed t according to their sensitivity or influence.

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