Site Measurement and Study of Vertical Freezing Wall Temperatures of a Large‐Diameter Shield Tunnel

Hu, Jun; Liu, Wenbo; Pan, Yutao; Zeng, Hui

doi:10.1155/2019/8231458

Cited by 14 publications

(6 citation statements)

References 34 publications

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“…Many scholars have studied the end of tunnel construction and the connecting channel by using the freezing method. In terms of the measurement of the freezing temperature and displacement fields, Hu et al (2019), Fan et al (2019) and Fan et al (2020) analyzed in detail the vertical frozen-soil curtain at the end of the tunnel during freezing. The temperature distribution and surface deformation provide measured data for the freezing temperature field at the end of a large-diameter crossriver tunnel.…”

Section: Introductionmentioning

confidence: 99%

Water-Rich Soft Soil Freezing Method Combined With Steel Sleeve Receiving-Shield Technology Field Test Research

et al. 2022

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The initiation and reception of shields are major risk events for shield construction in water-rich and weak strata. Although the freezing method and the steel sleeve method receiving-shield tunneling technologies both have engineering applications, the environmental safety control effect cannot meet the construction requirements of water-rich soft soil. Considering the shield construction of a typical soft soil layer in Suzhou, China, as a research target, the applicability and safety of the freezing method combined with steel sleeve receiving-shield technology in water-rich soft soil were evaluated based on a field test system. The test results show that, during soil freezing, the temperature change trend of each measuring point in the temperature measuring hole is roughly the same. The freezing process can be divided into five typical stages. The closer the active freezing period of the water-rich soft soil is to the inside of the frozen-soil curtain, the faster the development rate of the frozen wall. The soil cooling gradient increased with an increase in the radial depth. After freezing the curtain circle, the soil frost heave significantly accelerated until the frost heave amount peaked. During the construction process, special attention should be paid to the change in the value of the soil settlement during each stage change to prevent sudden changes in soil displacement. The freezing method, combined with steel sleeve receiving-shield technology, can effectively reduce the environmental disturbance caused by shield construction in water-rich soft soil.

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Section: Introductionmentioning

confidence: 99%

Water-Rich Soft Soil Freezing Method Combined With Steel Sleeve Receiving-Shield Technology Field Test Research

et al. 2022

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“…erefore, effective risk mitigation techniques are required to ensure the safe recovery of the shield from water-rich and sandy ground. A review of previous literature indicates that shield recovery technology in water-rich sandy strata predominantly includes artificial freezing [9], high-pressure rotary jet grouting [10], cement-soil deep mixing [11], and combinations of multiple approaches [12]. Another effective method for shield recovery in water-rich sandy strata involves covering the shield with a steel sleeve [13,14].…”

Section: Introductionmentioning

confidence: 99%

Risk Mitigation and Construction Control for Effective Underwater Recovery of an EPB Shield: A Case Study of the First Metro Tunnel in Tel Aviv

Yang

Jiang

et al. 2020

Advances in Civil Engineering

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Shield recovery in water-rich sand strata is a challenging issue in the field of shield tunnel engineering, especially when the end of the shaft cannot be reinforced by jet grouting or freezing or when the shield cannot be supported with a steel sleeve. Therefore, it is important to develop an effective recovery approach and adopt suitable techniques to control the risks. In this study, a new method based on filling the receiving shaft with water is proposed for the underwater recovery of an earth pressure balance (EPB) shield with zero end reinforcement from a metro tunnel in Tel Aviv, Israel. Several additional techniques are used to ensure safe recovery of the shield, including the design of a concrete cradle, drilling of pressure relief holes, control of excavation parameters, screw conveyor sealing, portal sealing, tail sealing, and grouting. Furthermore, according to the actual situation on site, filling the shaft with water to 1 m above the water level in the strata can prevent the fine sand from percolating into the shaft. Before the cutterhead approaches the underground diaphragm wall, the driving attitude should be strictly controlled, and the edge hob should be inspected for wear. The necessary thrust of shield tunneling in the underground diaphragm wall and shaft is calculated theoretically. In order to ensure the deformation control of the underground diaphragm wall and the smooth tunneling of the shield, the thrust of the shield excavating the underground diaphragm wall will not be larger than 12 000 kN, and the penetration degree will be limited to 3 mm/r. Qualitative observations and measurements of surface subsidence in the metro tunnel indicate that these risk mitigation techniques are effective and suitable for the underwater recovery of EPB shields in water-rich sand strata.

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“…Until now, a lot of research studies have been performed on the stratum freezing technology [1,[6][7][8][9][10][11][12][13][14][15][16][17][18][19], but some limitations still exist. Firstly, when they are used to study the development law of the frozen wall under the seepage, most of the model tests are the single-row-pipe frozen one.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Influencing Factors of Characteristic Index of Local Horizontal Frozen Body of Double‐Row Pipe under Seepage

Shan

Liu

et al. 2020

Advances in Materials Science and Engineering

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In order to deeply understand the influence of different factors on the characteristic indicators of the double-row-pipe partial horizontal frozen body in the sand-gravel stratum under the effect of seepage flow, several sets of sand-gravel stratum frozen model tests were carried out based on the similarity theory. The research showed that (1) under the effect of seepage flow, the backwater surface of the horizontal frozen body is in the shape of a quadratic parabolic and the development velocity of the backwater surface is inversely proportional to the square of the freezing time. The influence of seepage velocity on the downstream length and the freezing front development velocity of the backwater surface is stronger than the refrigerant temperature; (2) overlap time of the second row of frozen soil column increases with the increase of the distance between frozen pipes and seepage velocity and decreases with the decrease of the refrigerant temperature. The influence of various factors on the overlap time follows the order as the distance between freezing pipes > seepage velocity > refrigerant temperature. The average development velocity of the upstream surface decreases with the increase of the seepage velocity and the refrigerant temperature and first increases and then decreases with the increase of freezing pipe spacing. The influence of various factors on the average development velocity follows the order as seepage velocity > the distance between freezing pipes > refrigerant temperature. In addition, through the regression analysis, the quantitative relationship between the maximum arrangement spacing of the frozen pipes, the seepage velocity, and the refrigerant temperature was obtained. The research results can provide a basis for large-area partial horizontal freezing construction in Beijing sand-gravel stratum.

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Site Measurement and Study of Vertical Freezing Wall Temperatures of a Large‐Diameter Shield Tunnel

Cited by 14 publications

References 34 publications

Water-Rich Soft Soil Freezing Method Combined With Steel Sleeve Receiving-Shield Technology Field Test Research

Water-Rich Soft Soil Freezing Method Combined With Steel Sleeve Receiving-Shield Technology Field Test Research

Risk Mitigation and Construction Control for Effective Underwater Recovery of an EPB Shield: A Case Study of the First Metro Tunnel in Tel Aviv

Experimental Study on Influencing Factors of Characteristic Index of Local Horizontal Frozen Body of Double‐Row Pipe under Seepage

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