History of Pre-Thawing

Margaret Cysewski and Yuri ShurM.S. Arctic EngineeringUniversity of Alaska Fairbanks

Introduction

Thesis: History of Permafrost Engineering and Research in Fairbanks and Interior Alaska Alaska and Richardson Highways and Alaska

Railroad CRREL’s Fairbanks Permafrost Experimental

Station CRREL’s Permafrost Tunnel Near Fox, Alaska Pre-thawing techniques developed my gold

miners and Davidson Ditch

Outline

Introduction Steam thawing Hot-water thawing Cold-water thawing

Miles Method Pearce Method

Russian adaptation Recent application Final Remarks

Introduction

In frozen ground, the gold within in frozen gravel and very difficult to obtain.

In addition, the gravel was often covered with silt or muck.

Miners used fires and heated rocks for thawing

From Boswell, John C. (1979) History of Alaskan Operations of United States Smelting, Mining, and Refining Company. Fairbanks, AK: Mineral Industries Research Laboratory, University of Alaska Fairbanks.

Steam Thawing

Accidentally discovered in 1898 in Dawson. Clarence J. Berry noticed that the steam

coming from a hoisting engine’s exhaust hose had thawed the ground it was lying on.

Developed into steam points or sweaters.

Steam Points

1.9 to 2.5 centimeters extra-heavy pipe Commonly, 1.8 to 7.3 meters in length An 0.5-centimeter diameter orifice tip was welded to

the lower end of the pipe The upper end of the pipe had a driving head. These steam points varied with different drive-

heads, tips, and steam connections They were sunk through the silt layer to the gravels,

where intervals of steaming and driving was used to get through the gravel layer.

Application

Steam from a boiler was split off into a network of steam points.

Points were placed 1.5 to 3 meters apart.

Gravels was usually thawed between 8-48 hours

The variation is due to the soil condition and percentage of ice.

Hot-water thawing

One experiment showed that hot-water could thaw four times as much gravel in two-thirds the time and with half the fuel.

However, miners generally preferred steam over hot-water and hot-water thawing never took off.

Cold-Water Thawing: Miles Method John H. Miles

conducted his own thawing experiments in 1917 within the Cape Nome District.

Used water at its natural summer temperature.

Gol’dtman, V.G., Znamenskiy, V.V., and Chistopol’skiy S.D. (1970). Hydraulic thawing of frozen soils. Magadan: VNII-1, 448 p.

Comparison

Hours ThawedVolume (m^3)

Kilowatts UsedKilowatts

ThawingEfficiency(%)

Superheated Steam 156 83 231 8.9 3.8

Saturated Steam 98 63 185 10.8 5.8

Hot Water 67 62 124 15.3 12.3

Cold Water 192 421 58.7 33.7 57.4

Weeks, W.S. (1920). “Thawing frozen gravel with cold water.” Mining and Scientific Press, 120 (March 13), 367-370.

Miles Results

Miles concluded that the rate of water going into the thaw pipe should be dependent on the out flowing water temperature in order to maximize efficiency.

His theory of why the water flowed out the edges of the thawed hole and not next to the pipe is that, “the ground in thawing forms a porous streak between the

frozen and thawed area, and the water finds less resistance in this channel than in the thawed area”

Became the preferred method for dredging.

Cold-Water Thawing: Pearce Method Edward E. Pearce and Iver Johnson developed the

Pearce method in 1918 and 1919 within the Candle Creek district.

The Pearce Method uses the flow of surface water through soil to a lower point to thaw the ground.

Gol’dtman, V.G., Znamenskiy, V.V., and Chistopol’skiy S.D. (1970). Hydraulic thawing of frozen soils. Magadan: VNII-1, 448 p.

Pearce Experiment

Pearce, E.E. (1922). “Cold-Water Thawing of Frozen Gravel.” Mining and Scientific Press, 124 (February 4), 154-156.

Pearce Results

After 15 days of thawing and 80 hours of pumping water from the shaft, the area was thawed to the bedrock.

The final thawed area was 241 meters upstream from the shaft, 72 meters downstream from the shaft, an average width of 18 meters, and 2.7 meters to the bedrock with no frozen mounds.

Russian adaptation

Instead of hammering points, Russian miners install them in rotary-drilled holes, which made their installation much faster.

By using this method, many millions of cubic meters of frozen overburden and gravel were thawed on placer mining sites to a depth up to 40 to 50 meters.

Russian – Experiments The shape of the thawed

zone around a water point depends on soil properties. Layers of lower hydraulic

conductivity will thaw much slower.

A higher rate of water leads to greater thawing but to a limit. Excessive water will erode

channels which will then concentrate the flow of water along a point and slows the overall thawing. Gol’dtman, V.G., Znamenskiy, V.V., and Chistopol’skiy S.D. (1970).

Hydraulic thawing of frozen soils. Magadan: VNII-1, 448 p.

Russian – Miles Method

Time (T) dependence on flow rate (W) and distance between water points for specific conditions.

Most effective in coarse soils of high hydraulic conductivity the water will penetrate the

thawing soil then convective heat transfer will directly affect the frozen soil.

Gol’dtman, V.G., Znamenskiy, V.V., and Chistopol’skiy S.D. (1970). Hydraulic thawing of frozen soils. Magadan: VNII-1, 448 p.

Russian – Pearce Method Can only be used if the average permeability of the thawed soil is

not less than 40 meters/day the minimal permeability of the layers is not less than 10

meters/day. For sloping sites with the hydraulic gradient of 0.1 to 0.2, can be

used with an average permeability is 20 meters/day. The water channel length from the source to the drain was

usually kept between 20 to 80 meters. River water is used when its temperature was more than 3°C

usually water thawing index should be greater than 800 degree C-days

The air thawing index is greater than 1,000 degree C-days.

Recent Applications Modern technologies included closed system and open system

steam thawing. Closed systems used a double-walled probe where the

condensation returns to the boiler. Water thawing should only be used for well-drained, coarse-grained

soils Steam thawing examples

Fairbanks Airport Post Office in 1979, the Big Dipper Recreation Center in 1981 the Lathrop High School gymnasium in 1986 the West Valley High School gymnasium and theater in 1998 and 1999

Steam thawing for pile installation for soil temperatures below -1.5°C. Keep a pile unloaded for one to two weeks in the continuous permafrost

zone and several months in the discontinuous permafrost zone.

Final Remarks

While these pre-thawing methods were not developed in the Interior of Alaska, they were heavily used with gold mining in the area and an important part of its history.

www.cysewskipermafrost.com

References

Boswell, John C. (1979) History of Alaskan Operations of United States Smelting, Mining, and Refining Company. Fairbanks, AK: Mineral Industries Research Laboratory, University of Alaska Fairbanks.

Esch, D.C. (2004). “Chapter 7: Thawing Techniques for Frozen Ground.” Thermal Analysis, Construction, and Monitoring Methods for Frozen Ground, ed. D.C. Esch, American Society of Civil Engineers, Reston, Virginia, 239-257.

Goncharov, Y.M., Kim, M.V., Targulian, Y.O., and Vartanov, S.Kh. (1971). Pile construction in permafrost. Moscow, Civil Engineering Publishing, 187 p.

Gol’dtman, V.G., Znamenskiy, V.V., and Chistopol’skiy S.D. (1970). Hydraulic thawing of frozen soils. Magadan: VNII-1, 448 p.

Janin, C. (1922) Technical Paper 309: Recent Progress in the Thawing of Frozen Gravel in Placer Mining, Department of the Interior Bureau of Mines, Washington D.C.

McFadden, T.T and F.L. Bennett. (1991). Construction in cold regions: a guide for planners, engineers, contractors, and managers. John Wiley & Sons, United States of America.

Pearce, E.E. (1922). “Cold-Water Thawing of Frozen Gravel.” Mining and Scientific Press, 124 (February 4), 154-156.

Perl’shtein, G.Z. (1979). Water and thermal impact on frozen soils in North-East of USSR. Novosibirsk: Nauka, 232 p.

Weeks, W.S. (1920). “Thawing frozen gravel with cold water.” Mining and Scientific Press, 120 (March 13), 367-370.

Wimmler, N.L. (1927). Placer-Mining Methods and Costs in Alaska, United States Government Printing Office, Washington, D.C.