THERMAL DESIGN IN PERMAFROST SOILS

METHODS OF CALCULATING THE THERMAL REGIME FOR THERMAL DESIGN IN PERMAFROST SOILS ARE DISCUSSED, AND A SET OF EXAMPLES PRESENTED TO ILLUSTRATE SOME DESIGN PROCESSES. THE OCCURRENCE OF PERMAFROST IS SCHEMATICALLY SHOWN IN A FIGURE WHERE PERMAFROST IS THAT SOIL WHICH IS NEVER WARMER THAN 32 F DURING THE YEAR. THE ACTIVE LAYER AT THE GROUND SURFACE IS SEASONALLY THAWED AND FROZEN, AND THE SOIL BELOW THE PERMAFROST LAYER HAS VERY LITTLE SEASONAL VARIATION AND IS ABOVE FREEZING. MANY DESIGN PROBLEMS CAN BE PROPERLY SOLVED BY USING RELATIVELY SIMPLE STEADY STATE HEAT FLOW CALCULATIONS. THE GREAT ADVANTAGE TO STEADY STATE ANALYSIS IS THAT SUPERPOSITION CAN BE APPLIED. A USEFUL, ANALYTICAL METHOD USING SUPERPOSITION BY AN EASY GRAPHICAL METHOD IS DESCRIBED. THIS METHOD IS CALLED THE TWO-LANE ROAD CASE BECAUSE HEAT FLOW LINES ARE SEGMENTS OF CIRCLES AND ISOTHERMS ARE DQUALLY SPACED RADIAL LINES. TWO SOLUTIONS OF THIS TYPE CAN BE SUPERIMPOSED WHERE THE DISTURBANCE CAUSED BY THE HEATED REGION IS ADDED TO THE ORIGINAL UNIFORM SOIL TEMPERATURE. THE ISOTHERMS ARE THEN CONSTRUCTED BY CONTOURING THE MANY INDIVIDUAL POINTS OF EQUAL TEMPERATURE AT INTERSECTIONS OF RADIAL LINES. THIS TYPE OF SOLUTIONS ASSUMES A HOMOGENEOUS SOIL, AND A LAYERED SYSTEM OF SOILS WITH VARIABLE THERMAL CONDUCTIVITY WILL HAVE A DIFFERENT THERMAL REGIME. THE LAYERED CASE CAN BE SOLVED BY SUPERPOSITION, BUT NOT DIRECTLY BY THIS METHOD. ANOTHER STEADY STATE SOLUTION IS THE CASE OF HEATED PIPELINE SUCH AS ONE CARRYING WARM CRUDE OIL. A SOLUTION HAS BEEN ANALYTICALLY SOLVED IN CLOSED FORM. PROBLEMS WHICH REQUIRE A THREE-DIMENSIONAL SOLUTION ARE CONSIDERABLY MORE DIFFICULT TO ANALYZE. AN EXCELLENT ANALYTICAL PROCEDURE WITH MANY APPLICATIONS HAS BEEN DEVELOPED BY LACHENBRUCH, 1958. THIS PROCEDURE ALLOWS A RATHER COMPLETE DETERMINATION OF THE THERMAL REGIME UNDER DISTURBED GROUND SURFACE AREAS OF ANY SHAPE AND IS APPLICABLE TO PROBLEMS ASSOCIATED WITH BUILDINGS, ROADS, AIRFIELDS, LAKES, AND SHORELINES. SEVERAL NUMERICAL TECHNIQUES ARE AVAILABLE FOR SOLVING STEADY STATE PROBLEMS, HOWEVER, ONLY RELAXATION IS DISCUSSED. THE TWO- DIMENSIONAL CASE IS USED AS AN EXAMPLE, AND IT IS SEEN THAT THE THREE DIMENSIONAL CASE IS A SIMPLE EXTENSION. SINCE ROAD CONSTRUCTION INCREASES THE MEAN ANNUAL SOIL SURFACE TEMPERATURE AND THE VARIATION OF SEASONAL SOIL TEMPERATURE, BOTH OF WHICH INCREASE THE DEPTH OF SEASONAL THAW AND CAN CAUSE PERMAFROST THAWING, THE SOLUTION IS TO APPLY ENOUGH INSULATION BENEATH THE ROAD SURFACE TO PREVENT PERMAFROST DEGRADATION.

  • Supplemental Notes:
    • Tech Memo NO 96, PP 85-119, 20 FIG, 3 TAB, 5 REF
  • Corporate Authors:

    Canadian Conf Proc On Permafrost

    /Third Conf
    ,   United States 
  • Authors:
    • Peyton, H R
  • Publication Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 00232791
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 24 1970 12:00AM