FROST JACKING FORCES ON H AND PIPE PILES EMBEDDED IN FAIRBANKS SILT. INTERIM REPORT

Axial strains caused by frost heaving and the volumetric expansion of near surface soil layers, were measured between 23 November 1982 and 13 April 1983, on two test piles, embedded in Fairbanks. Test piles consisted of a 12 in. diameter pipe and a 10 x 57 H-pile, instrumented with strain gauges and temperature sensors at 6 in. intervals. The strain measurments were used to calculate the uplift forces and shear stresses along the pile-soil interfaces to a depth of approximately 10 ft. Uplift forces caused by frost heaving were highest following major cold periods. Fluctuation in force levels through the year correlated well with soil temperature fluctuations at depth, but lagged air temperature fluctuations by one or more days. Beginning in February, strong diurnal force fluctuations occurred which were directly correlated with near surface soil temperature fluctuations. These were ascribed to temperature-induced volumetric expansion and contraction of the upper soil layers. The highest uplift force for the H-pile was 212 kips at a depth of 8 ft., measured on 22 January 1983. The maximum shear stress was 93 psi on the total H-pile surface area, and 152 psi when the H-pile surface area was computed using a rectangular outer boundary geometry for the pile. The maximum force and shear stress for the pipe pile were 158 kips at a depth of 6.8 ft. and 130 psi on 18 January 1983. Water was frozen around each pile in mid-winter to simulate the formation of aufeis around bridge piles. Tangential forces and stresses on the piles were highest during the freezing period and caused a maximum increase in force in the H and pipe piles of about 12 kips and 25 kips above the ambient force levels. Once the water was frozen, force and stress levels in the piles returned to levels caused by frost heaving only.

• Record URL:
  • http://www.dot.state.ak.us/stwddes/research/assets/pdf/fhwa_ak_rd_84_13.pdf
• 
• Corporate Authors:

  Alaska Department of Transportation and Public Facilities

  2301 Peger Road
  Fairbanks, AK  United States  99701
• Authors:
  • Johnson, J B
• Publication Date: 1983

Media Info

• Pagination: 64 p.

Subject/Index Terms

• TRT Terms: Frost heaving soils; Mechanical strain; Pipe; Shear stress; Soil structure interaction; Support piles; Temperature; Uplift pressure
• Uncontrolled Terms: Axial strain; Pipe piles
• Old TRIS Terms: H bearing piles
• Subject Areas: Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00488180
• Record Type: Publication
• Source Agency: Alaska Department of Transportation and Public Facilities
• Report/Paper Numbers: AK-RD-84-13
• Files: TRIS, STATEDOT
• Created Date: Sep 30 1989 12:00AM