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 Modeling the Unfrozen Water Content of Frozen Soil Based on the Absorption Effects of Clay Surfaces

2020 ◽  
Vol 56 (12) ◽  
Author(s):  
Xiao Jin ◽  
Wen Yang ◽  
Xiaoqing Gao ◽  
Jian‐Qi Zhao ◽  
Zhenchao Li ◽  
...  
Keyword(s):  
Water Content ◽  
Frozen Soil ◽  
Unfrozen Water ◽  
Unfrozen Water Content

Strength of frozen saline soils

1995 ◽  
Vol 32 (2) ◽  
pp. 336-354 ◽  
Author(s):  
E.G. Hivon ◽  
D.C. Sego
Keyword(s):  
Water Content ◽  
Fine Particles ◽  
Constant Strain Rate ◽  
Significant Loss ◽  
Time Domain Reflectometry ◽  
Frozen Soil ◽  
Unfrozen Water ◽  
Strain Behavior ◽  
Unfrozen Water Content ◽  
The Time Domain

This paper summarizes an extensive laboratory program undertaken to study the influence of soil type, temperature, and salinity on the strength of three different frozen soils under conditions of unconfined constant strain rate tests. Since the effects of temperature and salinity can be unified by studying the variation of unfrozen water content, measurements of unfrozen water at different temperatures were carried out using the time-domain reflectometry (TDR) method. The stress–strain behavior is influenced by the presence of fine particles in the soil, and an increase in temperature and salinity (unfrozen water content) causes a significant loss of strength. For each soil tested, a predictive model of its strength in terms of salinity and temperature (unfrozen water content) is presented. Key words : frozen soil, saline, unfrozen water, strength.

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.

scholarly journals Coupled cellular automata for frozen soil processes

SOIL ◽  
2015 ◽  
Vol 1 (1) ◽  
pp. 103-116 ◽  
Author(s):  
R. M. Nagare ◽  
P. Bhattacharya ◽  
J. Khanna ◽  
R. A. Schincariol
Keyword(s):  
Cellular Automata ◽  
Phase Change ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Potential ◽  
Frozen Soil ◽  
Soil Freezing ◽  
Unfrozen Water ◽  
First Order ◽  
Unfrozen Water Content

Abstract. Heat and water movement in variably saturated freezing soils is a strongly coupled phenomenon. The coupling is a result of the effects of sub-zero temperature on soil water potential, heat carried by water moving under pressure gradients, and dependency of soil thermal and hydraulic properties on soil water content. This study presents a one-dimensional cellular automata (direct solving) model to simulate coupled heat and water transport with phase change in variably saturated soils. The model is based on first-order mass and energy conservation principles. The water and energy fluxes are calculated using first-order empirical forms of Buckingham–Darcy's law and Fourier's heat law respectively. The liquid–ice phase change is handled by integrating along an experimentally determined soil freezing curve (unfrozen water content and temperature relationship) obviating the use of the apparent heat capacity term. This approach highlights a further subtle form of coupling in which heat carried by water perturbs the water content–temperature equilibrium and exchange energy flux is used to maintain the equilibrium rather than affect the temperature change. The model is successfully tested against analytical and experimental solutions. Setting up a highly non-linear coupled soil physics problem with a physically based approach provides intuitive insights into an otherwise complex phenomenon.

Effect of Sulfate Contaminant on Soil Properties and Infrastructure Safety in Permafrost Regions

2010 ◽  
Vol 113-116 ◽  
pp. 1208-1211
Author(s):  
Xi Zhong Yuan ◽  
Yuan Lin Zhu ◽  
Ning Zhang
Keyword(s):  
Physical Properties ◽  
Mechanical Behavior ◽  
Water Content ◽  
Contaminated Soil ◽  
Freezing Temperature ◽  
Frozen Soil ◽  
Unfrozen Water ◽  
Compression Tests ◽  
Exponential Relationship ◽  
Unfrozen Water Content

Contamination of unfrozen water in frozen soil could have adverse effects on surrounding infrastructure such as foundation instability or deterioration of trafficability. This paper describes the results of the experimental examination of the physical properties and mechanical behavior of Na2SO4 contaminated soil. Initial freezing temperature test, unfrozen water content test and unconfined compression tests were conducted on silts with 3 levels of concentrations (6, 18 and 42 ppt) of Na2SO4 and nonsaline cases at temperatures ranging between 0°C and -20°C. The test results indicate that the presence of salt significantly affect the physical properties and mechanical behavior of the frozen soil. Contamination of soils will cause depression of freezing temperature and degradation of permafrost. The freezing temperature depression ratio of Na2SO4 contaminated soil is 0.028°C/ppt. The unfrozen water content increases with an increase in salinity and temperature. The strength decreases with an increase in salinity, and the strength loss ratio of Na2SO4 contaminated soil is among 0.02-0.04MPa/ppt. Combined the effect of salinity and temperature on the strength, the decrease in strength with increase in unfrozen water content follows an exponential relationship. So estimation of salt concentration in the soil, and predictions of future increases of salt in the soil, is essential for design of buildings and roadways in permafrost.

Unfrozen water content in saline soils: results using time-domain reflectometry

1985 ◽  
Vol 22 (1) ◽  
pp. 95-101 ◽  
Author(s):  
D. E. Patterson ◽  
M. W. Smith
Keyword(s):  
Water Content ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Frozen Soil ◽  
Probe Design ◽  
Unfrozen Water ◽  
Use Of Time ◽  
Unfrozen Water Content ◽  
Pore Water Salinity ◽  
Apparent Dielectric Constant

The use of time-domain reflectometry (TDR) for determining the phase composition of saline permafrost from measurement of the apparent dielectric constant, Ka, is examined.Combined TDR–dilatometry experiments were performed to assess whether the TDR method could be used on frozen soil samples with high pore water salinity. In general, unfrozen water content determinations by TDR were within ±0.025 cm3∙cm−3 of those obtained by dilatometry, with no marked influence due to salinity. A novel probe design for use on saline core samples shows promise as a means for determining unfrozen water contents in the field.

Sign in / Sign up

Export Citation Format

Share Document