SHEAR STRENGTH OF SOME HAWAIIAN LATOSOLS.
IOWA STATE UNIV AMES SOIL RESEARCH LAB
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In situ shear strength measurements were made on three different soil series on the island of Oahu, Hawaii. Tests at depths between 2 and 3 ft indicate a low cohesion averaging about 0.6 psi and an angle of internal friction averaging about 25 degrees. Tests at about 3.5 ft depth gave the same internal friction angle but an appreciably higher cohesion. The kaolinite content determined from x-ray diffraction showed a positive correlation with cohesion. A slope stability analysis assuming saturation and seepage and using the average values of cohesion, internal friction, soil unit weight, and slope angle, resulted in a calculated depth to failure of 1.9 ft. This is close to the observed depth of slides described in the literature. At ordinary moisture contents, calculations indicate the slopes are stable. The increase in cohesion with depth precludes deep soil slides and is an argument for parallel slope retreat as a result of weathering. Author
- Soil Mechanics