scholarly journals Experimental and Numerical Investigation on Improved Design for Profiled Freezing-tube of FSPR

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 992
Author(s):  
Yin Duan ◽  
Chuanxin Rong ◽  
Hua Cheng ◽  
Haibing Cai ◽  
Zongjin Wang ◽  
...  
Keyword(s):  
Vertical Direction ◽  
Calculation Model ◽  
Frozen Soil ◽  
Working Environment ◽  
Scaled Model ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Improved Design ◽  
Lower Temperature ◽  
The Right

The freeze-sealing pipe roof (FSPR) method, which combines the pipe roof method (PRM) with the artificial ground freezing (AGF) method, has been successfully utilized for the first time in the Gongbei Tunnel Project in China. During the construction process, there have been practical problems such as difficulty in welding of the profiled freezing-tube, easy leakage of refrigerant, and working environment pollution, which bring difficulties to the tunnel construction and may affect the further promotion of this new method in the future. To address these problems, a method of placing double circular freezing-tubes on the inner wall of the hollow pipe and wrapped with cement mortar was put forward to replace the welding profiled freezing-tube in the actual project. By designing a scaled model test, the feasibility and freezing effect of this improved design were verified. The corresponding numerical calculation model was established to study the distribution characteristics and differences of temperature field under two different configurations. The research results show that the Configuration 2, with the improved design, presents a lower temperature and a higher cooling rate; the limiting-tube could limit the excessive development of the frozen soil wall within a certain range, to avoid the adverse impact of frost heave on the ground building structure. Under the premise of meeting the design requirements for freezing, the freezing time of Configuration 2 at the centerline between the pipes and the vertical line of the hollow pipe is 33% and 46% shorter than that of Configuration 1, respectively. Finally, the average thickness of the frozen soil wall at the right side of the hollow pipe, the vertical direction of the hollow pipe, and between the pipes increased 33%, 17%, and 13% in Configuration 2, respectively. The improved design proposed in this paper is not only more convenient in production and installation but is also demonstrated to provide improved freezing effects, providing a strong guarantee for the further popularization and application of the freeze-sealing pipe roof method.

scholarly journals Freezing Temperature Field of FSPR under Different Pipe Configurations: A Case Study in Gongbei Tunnel, China

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Yin Duan ◽  
Chuanxin Rong ◽  
Hua Cheng ◽  
Haibing Cai ◽  
Wei Long
Keyword(s):  
Temperature Field ◽  
Freezing Temperature ◽  
Cooling Capacity ◽  
Frozen Soil ◽  
Construction Technology ◽  
Scaled Model ◽  
The Difference ◽  
Improved Design ◽  
Lower Temperature ◽  
Time Required

As a new tunnel presupport construction technology, the freeze-sealing pipe roof method (FSPR) has been successfully applied to the Gongbei Tunnel Project for the first time in China. To overcome the practical difficulties of this new method in the freezing construction process, such as welding difficulties of the profiled freezing tube, refrigerant leakage, and long construction period, based on the principle of an equal cooling capacity, an improved design of freezing tube was proposed. By designing three different pipe configurations and using scaled model tests and numerical simulation, the feasibility of the improvement and the difference in the freezing temperature field were studied. The research results show that the improved design with double circular freezing tubes exhibited a lower temperature and a higher cooling rate during the test, and the time required to meet the freezing design requirements was significantly shortened. Finally, a composite structure of “pipe roof and frozen soil curtain” with a better carrying capacity and water sealing performance was formed. It was recommended to strengthen the temperature monitoring at the pipe wall in the preliminary stage of the freezing construction to ensure the water sealing effect between the pipes. In the later stage, attention should be paid to monitoring the thickness of the frozen curtain and reducing excessive frost heave through technical means such as cooling capacity control. The improvement and configurations proposed in this research could effectively replace profiled freezing tubes in the original project, better adapt to horizontal freezing projects of similar curved tunnels, achieve the freezing goal faster, and provide a reference for the promotion of the FSPR.

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.

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

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.

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.

Inverse Heat Conduction Problem of the Temperature Field with Artificial Ground Freezing Method

2011 ◽  
Vol 243-249 ◽  
pp. 89-92
Author(s):  
Shi Liang Xu
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Heat Conduction ◽  
Heat Conduction Problem ◽  
Back Analysis ◽  
Inverse Heat Conduction Problem ◽  
Frozen Soil ◽  
Inverse Heat Conduction ◽  
Ground Freezing ◽  
Artificial Ground Freezing

The Artificial Ground Freezing (AGF) Method play an important role in the geotechnical engineering and the back analysis of thermal conductivity of frozen soil is the main inverse heat conduction problem of temperature field. In this paper the physical modelling test of AGF is carried out with double-row-pipe freezing in the lab. According to the measured temperature, the back analysis of thermal conductivity of frozen soil is solved based on the two-dimensional finite element simulation and the least square principle. It is helpful to investigate the freezing process and determine the frozen wall thickness.

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.

scholarly journals Field Test Study of the Artificial Ground-Freezing Method Subsurface Excavation Construction of Watered Sandy Stratum in Collapsible Loess Area

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yuan Mei ◽  
Liangjie Zhao ◽  
Xueyan Wang ◽  
Dongbo Zhou ◽  
Tong Yang ◽  
...  
Keyword(s):  
Development Rate ◽  
Frozen Soil ◽  
Cooling Curve ◽  
High Water Content ◽  
Frost Heaving ◽  
Loess Area ◽  
Ground Freezing ◽  
Collapsible Loess ◽  
Artificial Ground Freezing ◽  
The Cross

Saturated sandy stratum often makes tunnel excavation exceedingly difficult owing to its high water content. The artificial ground-freezing (AGF) method is an effective way to reduce the construction risks in such stratum; however, the AGF mechanism in the saturated sandy stratum of a collapsible loess area still lacks sufficient research. Based on field tests and numerical simulations, this study investigates the regularity of the temperature development, frost heave, and thaw subsidence distribution during the cross passage construction of a saturated sandy stratum in a collapsible loess area, using the AGF method. The results showed that the inward development rate of the frozen soil wall in the saturated sandy stratum was faster than its outward development rate. The gradient of the soil cooling curve was positively related to the longitudinal depth of the cross passage. The thickness of the frozen soil wall calculated by the slowest development rate of the frozen soil was conservative. The application of the pressure relief hole was beneficial to the release of the frost-heaving force and the control of the frost-heaving displacement. The pressure gauge pressure increase could be used as an identifier for the closure of a frozen soil wall. After excavation, the inner wall of the cross passage moved toward the inner space of the passage.

Effects of Menopausal Symptoms on Work Life and Organizational Environment.

2020 ◽  
Vol 16 ◽  
Author(s):  
Aslı Eker ◽  
Meltem Aydın Besen ◽  
Mine Yurdakul
Keyword(s):  
Work Performance ◽  
Work Life ◽  
Working Environment ◽  
Detailed Knowledge ◽  
Physical Conditions ◽  
Negative Effect ◽  
Perceived Effects ◽  
Study Population ◽  
Policies And Programs ◽  
The Right

Background: Every working woman has the right to continue to live as a healthy individual. The working environment has important effects on general health status and reproductive health of women. If menopouse period of women is not taken into consideration and if appropriate arrangements are not made at workplaces, their work performance and productivity decrease. It is important to have detailed knowledge about factors creating risk for health in order to develop effective policies and programs directed towards preventing them. Objective: This study was performed to determine perceived effects of menopause on work life and attitudes of an institution towards menopausal women. Methods: The study population included 419 women aged 45-55 years and working at a university. Out of 419 women, 291 could be contacted. Data were collected with a questionaire composed of questions about descriptive characteristics, effects of menopause on work life and support from and attitudes of the institution about menopause. Data collected to reveal menopausal women’s experiences at work were analyzed with statistical methods frequency, percentages and mean. Results: The mean age at which menopause started was 47 years and 89.7% of the women experienced menopausal complaints. Conclusions: Physical conditions at work and stressors were found to increase menopausal complaints and had a negative effect on work performance.

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