Large-scale laboratory tests on artificial ground freezing under seepage-flow conditions

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.

Download Full-text

Large-scale physical model for simulation of artificial ground freezing with seepage flow

Physical Modelling in Geotechnics, Two Volume Set ◽

10.1201/b10554-63 ◽

2010 ◽

pp. 405-408

Keyword(s):

Physical Model ◽

Large Scale ◽

Seepage Flow ◽

Ground Freezing ◽

Artificial Ground Freezing

Download Full-text

Numerical simulation model of artificial ground freezing for tunneling under seepage flow conditions

Tunnelling and Underground Space Technology ◽

10.1016/j.tust.2019.103035 ◽

2019 ◽

Vol 92 ◽

pp. 103035 ◽

Cited By ~ 10

Author(s):

Zhiming Li ◽

Jian Chen ◽

Mitsutaka Sugimoto ◽

Hongyan Ge

Keyword(s):

Numerical Simulation ◽

Simulation Model ◽

Seepage Flow ◽

Flow Conditions ◽

Ground Freezing ◽

Artificial Ground Freezing

Download Full-text

Large Scale Application of Artificial Ground Freezing

Soft Ground Technology ◽

10.1061/40552(301)25 ◽

2001 ◽

Cited By ~ 2

Author(s):

Peter van Dijk ◽

Jeannette Bouwmeester-van den Bos

Keyword(s):

Large Scale ◽

Ground Freezing ◽

Artificial Ground Freezing

Download Full-text

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

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.1662 ◽

2013 ◽

Vol 353-356 ◽

pp. 1662-1665 ◽

Cited By ~ 1

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.

Download Full-text

Artificial Ground Freezing Impact on Shear Strength and Microstructure of Granite Residual Soil Under an Extremely Low Temperature

Frontiers in Earth Science ◽

10.3389/feart.2021.772459 ◽

2021 ◽

Vol 9 ◽

Author(s):

Ran An ◽

Xianwei Zhang ◽

Lingwei Kong ◽

Jianwu Gong ◽

Xuewen Lei

Keyword(s):

Shear Strength ◽

Low Temperature ◽

Magnetic Resonance Image ◽

Large Scale ◽

Friction Angle ◽

Treatment Temperature ◽

Residual Soil ◽

Ground Freezing ◽

Artificial Ground Freezing ◽

Granite Residual Soil

The Artificial Ground Freezing (AGF) method, which is widely used in tunnel excavations, significantly affects the properties of geotechnical materials in frozen walls under extremely low temperatures. In order to simulate the AGF process, the freezing treatment with a temperature of −30°C and thawing treatment temperature of 25°C were performed on natural specimens of granite residual soil (GRS). Subsequently, triaxial (TRX) tests were conducted to evaluate mechanical properties and Nuclear Magnetic Resonance Image (NMRI) tests were applied to detect pore distributions of GRS. To clarify variations of microstructure after freezing-thawing, the relaxation time (T2) distribution curves and T2-weighted images from NMRI results were thoroughly analyzed from the perspective of quantization and visualization. Results show that the shear strength as well as the cohesion of GRS are reduced sharply by the AGF process, while the internal friction angle decreases gently. The pore size distribution (PSD) converted from the T2 curve is constituted of two different peaks, corresponding to micro-pores with diameters from 0.1 to 10 µm and macro-pores with diameters from 10 to 1,000 µm. Under the AGF impact, the expansion in macro-pores and shrinkage in micro-pores simultaneously exist in the specimen, which was verified from a visualized perspective by T2-weighted images. The frost heaving damage on shear strength is attributed to the microstructural disturbance caused by the presence of large-scale pores and uneven deformations in GRS, which is subjected to the AGF impact under an extremely low temperature.

Download Full-text

Analysis of Ground Movement during Large-Scale Pipe Roof Installation and Artificial Ground Freezing of Gongbei Tunnel

Advances in Civil Engineering ◽

10.1155/2021/8891600 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Xiao-qi Zhou ◽

Jian-li Pan ◽

Yang Liu ◽

Cai-cheng Yu

Keyword(s):

Large Scale ◽

Volume Ratio ◽

Frozen Soil ◽

Ground Movement ◽

Frost Heave ◽

Ground Settlement ◽

Soil Thickness ◽

Ground Freezing ◽

Artificial Ground Freezing ◽

Ground Heave

This paper analyzes the vertical ground movement during large-scale pipe roof installation and artificial ground freezing of Gongbei tunnel of the Hong Kong-Zhuhai-Macau bridge project. The transverse ground settlement during pipe roof installation is analyzed. The ground loss volume ratio and settlement trough width coefficient during pipe jacking are estimated based on the field measurement of ground settlement. The interaction of pipes during multiple jacking is investigated. The effect of frost heave control by pregrouting, limiting frozen soil thickness, and combination of the two methods is evaluated. The analysis shows that the ground settlement during pipe roof installation by jacking 37 pieces of 1620 mm steel pipes is relatively small with a maximum value of 2.2 cm. The reinforcement to ground provided by the fore-jacked pipes reduces the ground loss volume ratio and, consequently, the ground settlement during the follow-up pipe jacking. The artificial ground freezing generates a relatively large ground heave with a maximum value of 7.8 cm. Pregrouting plays a critical role in the frost heave control by reducing the heave by about 33%. Limiting the frozen soil thickness by heating pipes serves as an effective supplement to frost heave control by reducing the heave by about 9%. The combination of the two measures reduces the ground heave by about 42%. Findings from this paper provide valuable reference to the tunnel construction using pipe roof and artificial ground freezing as presupport.

Download Full-text

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

Applied Sciences ◽

10.3390/app11146275 ◽

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.

Download Full-text