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.

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.

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.

scholarly journals Site Measurement and Study of Vertical Freezing Wall Temperatures of a Large-Diameter Shield Tunnel

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Jun Hu ◽  
Wenbo Liu ◽  
Yutao Pan ◽  
Hui Zeng
Keyword(s):  
Surface Deformation ◽  
Ground Improvement ◽  
Large Diameter ◽  
Tunnel Boring Machine ◽  
Frozen Soil ◽  
Shield Tunnel ◽  
Tunnel Face ◽  
Water Permeation ◽  
Ground Freezing ◽  
Cement Treatment

When a large-diameter shield tunnel boring machine enters or exits a tunnel, the newly exposed tunnel face is prone to instability and water seepage. In order to prevent collapse of the tunnel face, local ground improvement can be used until the permanent tunnel lining can be installed. The tunnel launching project of the Nanjing Metro Line 10 cross-river tunnel had a high stability requirement for the entry and exit phases. To this end, this project used a combination of cement treatment and ground freezing methods. In this project, field measurement of the vertical freezing improvement of the large-diameter shield tunnel was carried out. The temperature distribution and ground surface deformation of the vertical frozen soil wall at the end of the tunnel during the active freezing and maintenance freezing periods were analyzed in detail. The result shows that the surface settlement and seepage were successfully controlled by the combined cement treatment and ground freezing. On the other hand, the combination of cement treatment and ground freezing helps to control the freezing-induced heaving. The hydration heat in improved ground leads to an increase in ground temperature and this leads to additional freezing duration. It was examined that the frozen soil wall and the enclosure structure were in a good cementation condition. These measured values provide guidance on the timing of the shield departure. The project results confirmed that instability and water permeation did not occur in the tunnel face during the subsequent excavation.

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.

Properties of Frozen Soils for Cross Passage Construction in Line 1 and 2 of Wuxi Metro

2013 ◽  
Vol 353-356 ◽  
pp. 1662-1665 ◽  
Author(s):  
Xiang Dong Hu ◽  
Yan Guang Han
Keyword(s):  
Mechanical Properties ◽  
Laboratory Tests ◽  
Freezing Point ◽  
Frozen Soil ◽  
Frost Heave ◽  
Soil Test ◽  
Frozen Soils ◽  
Freezing Method ◽  
Ground Freezing ◽  
Artificial Ground Freezing

Artificial ground freezing method (AGF) was applied in cross passage constructing of line 1 and 2 of Wuxi Metro. Mechanical properties of frozen soils such as uniaxial compressive strength, modulus of elasticity, Poissons Ratio, frost heave rate and freezing point are prerequisite for design and construction of AGF. In order to obtain the parameters mentioned, laboratory tests were conducted. One was the basic geotechnical test. Another was the frozen soil test.

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.

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