A simple theory is proposed for crack formation and development by soil desiccation on the basis of laboratory experiments utilizing soil samples (Bloomington till) with maximum particle size of 1 mm diam held in flat wooden containers. Slurry of the soil or loose compacted soil saturated with water by an ice sheet method was desiccated in containers of about 85 x 60 cm2. Relative humidity of the air under which desiccation took place was about 35% except for some supplementary experiments. The crack pattern is more dependent on the thickness of the soil sample than on temperature or humidity. Some effect is caused also by differences in the bottom material of the containers. The area of cells made by crack patterns has a log normal size distribuion. Total length of cracks decreases with increase in sample thickness. The number of sides of cells also depends on the thickness. Cracking was found to begin from the center of the soil layer and to propagate to the surface or bottom with non-uniform speed. The effects of stones on desiccation cracking can be summarized as follows: stones are nucleating points where desiccation cracks start. Shape, size, and porosity of the particle, and depth at which the particle is buried affect the initiation of cracks. The geometry and mean area of the cells is not affected by the presence of stones in a drying soil. Factors which promote "habituation" in the soil to crack in the same pattern at different wetting and drying cycles are: (1) complete soaking of the soil, (2) mixture of particles with the soil. Particles placed on top of the soil affect "habituation" differently. Sorting of particles into desiccation cracks requires "habituation". This is accomplished if the soil is soaked and dried repeatedly under wind and rain without vegetation. Areas above the timber line in cold environments (polar and high mountain regions) have the proper conditions for sorting into desiccation cracks. The unusual phenomenon called "wetting cracks", produced during wetting, and sorting into wetting cracks are also mentioned. Factors which promote or hinder sorting into desiccation cracks are indcated. /Author/

Media Info

  • Features: Appendices; Figures; References;
  • Pagination: 72 p.

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Filing Info

  • Accession Number: 00264412
  • Record Type: Publication
  • Report/Paper Numbers: CRREL-RR-66 Final Rpt.
  • Files: TRIS
  • Created Date: Jan 29 1975 12:00AM