FROST HEAVE INDUCED PIPE STRAIN OF AN EXPERIMENTAL CHILLED GAS PIPELINE SCOTT HUANG, PH.D. University of Alaska Fairbanks.

Transcription

1 FROST HEAVE INDUCED PIPE STRAIN OF AN EXPERIMENTAL CHILLED GAS PIPELINE SCOTT HUANG, PH.D. University of Alaska Fairbanks August 5, 2015 ISSAEST, Fairbanks, AK, USA, August 2-5, 2015

2 FROST HEAVE INDUCED PIPE STRAIN OF AN EXPERIMENTAL CHILLED GAS PIPELINE ISSAEST, FAIRBANKS, ALASKA, USA AUGUST 5, 2015 SCOTT HUANG, UAF, USA YANG KUN, CUPB, CHINA SATOSHI AKAGAWA, CRYOSPHERE ENGINEERING LABORATORY, JAPAN MASAMI FUKUDA, FUKUYAMA CITY UNIVERSITY, JAPAN SHUNJI KANIE, HOKKAIDO UNIVERSITY, JAPAN

3 OUTLINE 1. Introduction Proposed Alaska Gas Pipeline Engineering Challenges Pipeline Test Facility in Fairbanks, Alaska 2. Pipe Strain Analysis Frost Heave Induced Strain 3. Conclusions

4 1. Introduction Proposed Alaska Gas pipeline 1. The Producers Group (inactive) 2. TransCanada & ExxonMobil (inactive) 3. Alaska LNG Pipeline to Nikiski Engineering Challenges Pipeline Test Facility in Fairbanks, Alaska

5 TransCanada X psi; 4.5Bcf/day; ~ -10 o C The producers group X psi; 4.0Bcf/day; ~ -10 o C

6 Alaska LNG, 2015 The Alaska LNG Project; 3.0 ~ 3.5 Bcf/day; 20 M Tons LNG per year for export; $45B to $65B

7 1. Introduction Proposed Alaska Gas pipeline Engineering Challenges 1. Permafrost Terrains 2. Continuous vs. Discontinuous Permafrost 3. Thaw Stable Soil vs. Thaw Unstable Soil 4. Frost Susceptible Soil vs. Non-frost Susceptible Soil 5. Others (Earthquakes, Landslides, etc.) Pipeline Test Facility in Fairbanks, Alaska

8 Permafrost Distribution Modified after Jorgenson et al., 2008

9 Discontinuous Permafrost (Modified from G. H. Johnston, 1981) (Modified from Ferrians et al., 1969)

10 Discontinuous Permafrost Complex permafrost terrain relationship Mean annual air temperature is -5.5 C Thickness of active layer varies between 1-3 m Thickness of permafrost is up to ~45 m Ice-rich zones occur likely in the transient layer (i.e. upper part of permafrost)

11 Thaw Unstable Soil In areas of thaw unstable soil where heat from the gas in the pipeline (i.e. warm pipe) might cause thawing and consequent loss of soil foundation stability Photo by Daniel Fortier 2007

12 Frost Susceptible Soil In areas of frost susceptible soil where cooling from the gas in the pipeline (i.e. chilled pipe) might cause frost heave and consequent loss of pipeline structural integrity.

13 1. Introduction Proposed Alaska Gas pipeline Engineering Challenges Pipeline Test Facility in Fairbanks, Alaska

14 Test Facility

15 Test Facility 105 m long experimental gas pipeline (0.9 m diameter, 8.5 mm wall thickness) Monitoring devices used in this study 11 strain monitoring stations 28 pipe movement measuring stations, 5 frost heave gauges for foundation soil

16 Test Facility Ground Surface Seasonally frozen zone Permafrost zone 75 m 30 m 1 m

17 Test Facility Ground Temperature Elev m TFA Elev 0 m 1 m 1 m S N Dry Sand Native Silt Frozen Silt (permfrost) Peat Elev m Borehole Elev m Elev. 0 m TFB Elev. 0 m TFC 1 m 1 m 1 m 1 m S N S N Dry Sand Native Silt Frozen Silt (permfrost) Borehole Dry Sand Native Silt Frozen Silt (permfrost) Borehole Elev m Elev m

18 Test Facility Soil Heave

19 Test Facility Pipe Strain

20 2. Pipe Strain Analysis Frost Heave Induced Strain 1.Longitudinal 2.Circumferential

21 Frost Heave Monthly Averages

22 Frost Heave Monthly Averages

23 Frost Heave Monthly Averages

24 2. Pipe Strain Analysis Frost Heave Induced Strain 1.Longitudinal 2.Circumferential

25 Induced Longitudinal Strain Adfeeze Force Thermal Effect

26 Induced Longitudinal Strain - SG-4-0deg-L Temperature Measurements Strain Measurements Removal of Thermal Effects

27 2. Pipe Strain Analysis Frost Heave Longitudinal Circumferential

28 Induced Circumferential Strain Frozen Soil Pressure Secondary Freezing Pressure Adfreeze Force Frost Heave Pressure

29 Monthly Averages (March 2000)

30 Monthly Averages (September 2003)

31 Monthly Longitudinal Strain (March 2000) 270 Deg

32 Monthly Longitudinal Strain (September 2000) 270 Deg

33 Longitudinal Strain along the Pipeline (March 2003)

34 3. Conclusions Bending was one of the primary loading conditions on the pipeline. Generally speaking, the values of circumferential strain ranged from about 100 to 500 µε before chilled air was stopped. After the chilled air was ceased in July 2003, the circumferential strain decreased quickly.

35 3. Conclusions The induced maximum strains were approximately located at the edges of the transition zone. The pipeline has experienced more in tension than in compression due in part to the effect of soil heave.

36 Questions?