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SCIENCE CHINA Technological Sciences, Volume 62 , Issue 9 : 1636-1648(2019) https://doi.org/10.1007/s11431-018-9482-1

Development of pot-cover effect apparatus with freezing-thawing cycles

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  • ReceivedDec 4, 2018
  • AcceptedMar 4, 2019
  • PublishedJun 4, 2019

Abstract

‘Pot-cover effect’ refers to the phenomenon of moisture accumulation beneath the pavement under condensation or desublimation because the vapor transfer in the soil is blocked by the pavement. To study this phenomenon in the laboratory, we have developed the pot-cover effect apparatus with freezing-thawing cycles (PEAFC), which consists of three parts, namely, the vapor transfer system, the temperature control system, and the temperature and water content monitoring system. The major functions of this apparatus include: simulation of both vapor transfer and freezing-thawing cycling in the soil, real-time monitoring of the temperature and the water content in soil samples, and one-dimensional heat and moisture transfer in the samples. The FDR (frequency domain reflectometry) sensors of the apparatus are calibrated and a calibration formula is proposed to eliminate the water content measurement errors induced by temperature changes. Constant temperature difference tests and a freezing-thawing cycling test are conducted with the apparatus. Results indicate that the apparatus can control the water replenishment in the soil samples, monitor the vapor transfer in the samples in real time, and simulate the vapor transfer process under the condition of the freezing-thawing cycling in the soil. These tests verify the effectiveness and reliability of the apparatus, which indicates that the development purpose is achieved.


Funded by

the National Program on Key Basic Research Project of China(Grant,No.,2014CB47006)

and the National Natural Science Foundation of China(Grant,Nos.,51579005,&,11272031)


Acknowledgment

This work was supported by the National Program on Key Basic Research Project of China (Grant No. 2014CB47006), and the National Natural Science Foundation of China (Grant Nos. 51579005 & 11272031).


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  • Figure 1

    (Color online) Water content profile of soil under the cover at Beijing Daxing International Airport.

  • Figure 2

    (Color online) Cracks in the runway in Shenyang Taoxian International Airport (photographed on Sep. 6th, 2018).

  • Figure 3

    (Color online) Photo of PEAFC.

  • Figure 4

    (Color online) Schematic diagram of PEAFC.

  • Figure 5

    (Color online) Structure diagram of the vapor transfer system. 1 Water pipe, 2 water hose, 3 base temperature-control plate, 4 perforated plate, 5 cylinder, 6 thermal insulation sleeve, 7 flange plate, 8 handle of top temperature-control plate, 9 top temperature-control plate, 10 temperature and moisture sensors, 11 conduit, 12 water reservoir wall, 13 circulation liquid inlet or outlet.

  • Figure 6

    (Color online) Exploded view of the vapor transfer system.

  • Figure 7

    (Color online) Schematic of vapor entering the soil sample.

  • Figure 8

    (Color online) Contact between the top temperature-control plate and the soil sample.

  • Figure 9

    Particle size distribution curve of the soil.

  • Figure 10

    (Color online) Relationship between water contents and temperatures measured by the sensor.

  • Figure 11

    (Color online) Relationship between water contents measured by the sensor and by the microwave oven method.

  • Figure 12

    (Color online) Water contents after the calibration.

  • Figure 13

    (Color online) Measured temperature profile for case 7.

  • Figure 14

    (Color online) Temperature profiles at the end of the test of cases 7–10.

  • Figure 15

    (Color online) Water content profiles at the end of the test of cases 7–10.

  • Figure 16

    (Color online) Relationship between initial water content and amount of water in soil.

  • Figure 17

    (Color online) Position diagram of the sensors. (a) In the freezing-thawing cycling test; (b) in the one-dimensional test.

  • Figure 18

    Time history curve of temperatures of the top temperature-control plate in the freezing-thawing cycle test.

  • Figure 19

    (Color online) Water content and temperature profiles of the soil sample at the end of each cycle in the freezing-thawing cycle test. (a) Temperature profile; (b) water content profile.

  • Figure 20

    (Color online) Time history curves of temperatures (a) and water contents (b) measured by the sensors in the one-dimensional test.

  • Figure 21

    (Color online) Temperature profiles (a) and water content profiles (b) of case 8 and case 16.

  • Table 1   Initial conditions of the calibration test

    Case

    Water content (%)

    Dry density(g/cm3)

    Initialtemperature (°C)

    1

    6

    1.2

    20

    2

    12

    3

    18

    4

    21

    5

    28

    6

    32

  • Table 2   Initial conditions of the constant temperature difference tests

    Case

    Initial watercontent (%)

    Dry density(g/cm3)

    Initialtemperature (°C)

    7

    6

    1.2

    20

    8

    12

    9

    18

    10

    24

  • Table 3   Temperature control schemes of the constant temperature difference tests

    Case

    Time (d)

    Temperature of top temperature-control plate (°C)

    Temperature of base temperature-control plate (°C)

    7

    0–10

    −10

    20

    8

    9

    10

  • Table 4   Temperature control scheme of the freezing-thawing cycling test

    Time (d)

    Temperature of toptemperature-controlplate (°C)

    Temperature of base temperature-controlplate (°C)

    1, 13, 25

    −4.90

    20

    2, 14, 26

    −1.94

    20

    3, 15, 27

    7.33

    20

    4, 16, 28

    18.18

    20

    5, 17, 29

    26.15

    20

    6, 18, 30

    28.29

    20

    7, 19, 31

    28.12

    20

    8, 20, 32

    28.43

    20

    9, 21, 33

    22.45

    20

    10, 22, 34

    15.33

    20

    11, 23, 35

    3.21

    20

    12, 24, 36

    −4.51

    20

  • Table 5   Mean monthly ground temperatures in Beijing in 2012

    Month

    Mean groundtemperature (°C)

    Month

    Mean ground temperature (°C)

    1

    −4.90

    7

    28.12

    2

    −1.94

    8

    28.43

    3

    7.33

    9

    22.45

    4

    18.18

    10

    15.33

    5

    26.15

    11

    3.21

    6

    28.29

    12

    −4.51

  • Table 6   Depth of the sensors in the freezing-thawing cycling test

    Sensor number

    Depth (cm)

    Sensor number

    Depth (cm)

    1

    2

    7

    20

    2

    4

    8

    25

    3

    6

    9

    30

    4

    8

    10

    35

    5

    10

    11

    45

    6

    15

    12

    55

  • Table 7   Temperature control scheme of the one-dimensional test

    Time (d)

    Temperature of toptemperature-controlplate (°C)

    Temperature of basetemperature-controlplate (°C)

    1

    −8

    20

    2

    8

    20

    3

    −8

    20

    4

    8

    20

    5

    −8

    20

    6

    8

    20

    7

    −8

    20

    8

    8

    20

    9

    −8

    20

    10

    8

    20

  • Table 8   Depth of the sensors of the one-dimensional test

    Sensor number

    Depth (cm)

    Sensor number

    Depth (cm)

    1

    10

    7

    40

    2

    10

    8

    40

    3

    10

    9

    40

    4

    25

    10

    55

    5

    25

    11

    55

    6

    25

    12

    55

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