scholarly journals Research on the Ground Subsidence Mechanism of Cross Passage Caused by Freezing Method Construction

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Ruimin Zhang ◽  
Xuelei Cheng ◽  
Yan Li ◽  
Lin Pan ◽  
Jinhong Xia
Keyword(s):  
Temperature Field ◽  
Soft Soil ◽  
Internal Heat ◽  
Freezing Temperature ◽  
Treatment Method ◽  
Phase Changes ◽  
Ground Subsidence ◽  
Undisturbed Soil ◽  
Freezing Method ◽  
Method Construction

At present, the built or newly built underground structures are mostly concentrated in developed areas along the coast, lakes, and rivers, while deep soft soil is widely distributed in these areas. The cold heat treatment method is one of the advanced foundation treatments and has broad application prospect. However, geothermal exchange and temperature field change are complex Stefan problems with mobile boundaries, internal heat sources, and phase changes. It is important to determine the freezing area and freezing temperature reasonably under the premise of ensuring the safety of the frozen construction. Therefore, this paper summarizes the research methods of freezing method construction of cross passage and introduces the research on the constitutive model of freezing undisturbed soil, the theory of freezing wall calculation, and the evolution mechanism of the temperature field. Then, a brief evaluation is made in view of the lack of research, and the development direction of this field is put forward with the research characteristics. It is to deepen the understanding of the deformation mechanism of cross passage embedded in soft soil caused by the freezing and melting.

scholarly journals Pore Size Changes in Marine Soft Soil under Various Freezing Conditions

2020 ◽  
Vol 8 (3) ◽  
pp. 170 ◽  
Author(s):  
Bowen Kong ◽  
Fan Xia ◽  
Bingqi Yu ◽  
Tangdai Xia ◽  
Zhi Ding
Keyword(s):  
Pore Size ◽  
Soft Soil ◽  
Free Water ◽  
Freezing Temperature ◽  
Engineering Properties ◽  
Undisturbed Soil ◽  
Free Water Content ◽  
Differential Settling ◽  
Artificial Freezing ◽  
Freezing Temperatures

Artificial freezing methods can help highlight the mechanical properties of marine clay. The construction of cross passages in metro tunnels employs the freezing method. Freeze–thaw circulation, which is part of the process, affects the engineering properties of clay and produces differential settling. This paper describes the percentages of specific diameters of frozen–thawed soil under different freezing temperatures, measured with the help of nuclear magnetic resonance (NMR). In response to the experimental results, a weakening effect of freezing temperature and speed on soft soil is proposed. All sizes of undisturbed soil pores tend to increase under various freezing temperatures. Owing to differences in free water content, the water in medium pores freezes quicker than that in tiny pores. The quicker the freezing, the greater the resulting void ratio. Finally, potential reasons for changes in pore size under different freezing conditions are explained from a microcosmic perspective.

Study on Artificial Island Ground Improvement Method and Effect

2014 ◽  
Vol 1030-1032 ◽  
pp. 1037-1040
Author(s):  
Jin Fang Hou ◽  
Ju Chen ◽  
Jian Yu
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Improvement ◽  
Soft Soil ◽  
Horizontal Displacement ◽  
Treatment Method ◽  
Surcharge Preloading ◽  
Porosity Ratio ◽  
Improvement Method ◽  
Consolidation Degree

The artificial island ground on an open sea is covered by thick soft soil. It must be improved before using. In accordance with a designing scheme, the ground treatment method is inserting drain boards on land and jointed dewatering surcharge preloading, the residual settlement is not more than 30cm after improvement and the average consolidation degree is more than 85%. In order to estimate ground improvement effect and construction safety, instruments are buried to monitor the whole ground improving processes. By monitoring settlement and pore water pressure, it is shown that the total ground settlement in construction is 2234mm, its final settlement is 2464mm, and consolidation degree and residual settlement respectively satisfy requirements. In ground improvement, horizontal displacement is small and construction is safe. Meanwhile, the results of soil properties and vane shear strength detection tests show the soft soil ground is greatly reduced in water content and porosity ratio, and improved in strength. It is named that the ground improvement method is reasonable and reaches expected effect.

scholarly journals Study on the Formation Law of the Freezing Temperature Field of Freezing Shaft Sinking under the Action of Large-Flow-Rate Groundwater

2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
Bin Wang ◽  
Chuan-xin Rong ◽  
Jian Lin ◽  
Hua Cheng ◽  
Hai-bing Cai
Keyword(s):  
Temperature Field ◽  
Groundwater Flow ◽  
Flow Velocity ◽  
Flow Rate ◽  
Freezing Temperature ◽  
Freezing Process ◽  
Flow Rates ◽  
Porosity Reduction ◽  
Shaft Sinking ◽  
Large Flow

Taking into account moisture migration and heat change during the soil freezing process, as well as the influence of absolute porosity reduction on seepage during the freezing process, we construct a numerical model of hydrothermal coupling using laws of conservation of energy and mass. The model is verified by the results of large-scale laboratory tests. By applying the numerical calculation model to the formation of artificial shaft freezing temperature fields under the action of large-flow groundwater, we conclude that groundwater with flow rates of less than 5 m/d will not have a significant impact on the artificial freezing temperature field. The maximum flow rates that can be handled by single-row freezing pipes and double-row freezing pipes are 10 m/d and 20 m/d, respectively, during the process of freezing shaft sinking. By analyzing the variation of groundwater flow rate during freezing process, we find that the groundwater flow velocity can reach 5–7 times the initial flow velocity near the closure moment of the frozen wall. Finally, in light of the action characteristics of groundwater on the freezing temperature field, we make suggestions for optimal pipe and row spacing in freezing pipe arrangement.

scholarly journals Structural and Phase Changes in the System Al-Si-Ti-B, Synthesized Using the Electron-Ion-Plasma Treatment Method

2017 ◽  
Vol 189 ◽  
pp. 012031
Author(s):  
A A Klopotov ◽  
E A Petrikova ◽  
Yu F Ivanov ◽  
A D Teresov ◽  
N N Cherenda ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Treatment Method ◽  
Phase Changes ◽  
Ion Plasma

Dewatering Preloading Test and Ground Subsidence in a Project

2011 ◽  
Vol 250-253 ◽  
pp. 1912-1916
Author(s):  
Yong Mou Zhang ◽  
Jian Chang Zhao
Keyword(s):  
Water Level ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
New Technology ◽  
Soft Soil ◽  
Soil Treatment ◽  
Ground Subsidence ◽  
Confined Water ◽  
Phreatic Water ◽  
The Relationship

Ground subsidence is one of the main geological hazards in Shanghai. The ground subsidence is caused by pumping groundwater greatly. In the past, studies of ground subsidence in Shanghai were mostly taken for the ground subsidence caused by pumping confined water in Puxi. And ground subsidence caused by pumping phreatic water was rarely studied. Dewatering preloading is a new technology for soft soil treatment. The monitoring of ground water level, ground subsidence, pore water pressure in the process of dewatering preloading test for a soft soil treatment project in Pudong showed that pumping phreatic water can also cause ground subsidence. The ground subsidence caused by pumping phreatic water was analyzed in this paper. The relationship between phreatic water level and ground subsidence was obtained.

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