In Situ Stress Determination by Iowa Stepped Blade

by Richard L. Handy, (M.ASCE), Prof. of Civ. Engrg.; Iowa State Univ., Ames, Iowa 50011,
Bernard Remmes, (A.M.ASCE), Geotechnical Engr.; McClelland Engrg., Houston, Tex.,
Steven Moldt, (A.M.ASCE), Geotechnical Engr.; Warzyn Engrg., Inc., Madison, Wisc.,
Alan J. Lutenegger, (A.M.ASCE), Pres.; Geotechnical Test Systems, Inc., Ames, Iowa 50010,
Gary Trott, (A.M.ASCE), Geotechnical Engr.; Weideman & Singleton, Atlanta Ga.,

Serial Information: Journal of the Geotechnical Engineering Division, 1982, Vol. 108, Issue 11, Pg. 1405-1422

Document Type: Journal Paper


Lateral soil pressure is a vital element in soil mechanics theory and practice, but is very sensitive to disturbance and, therefore, difficult to measure. A step-tapered blade was developed to compensate for disturbance by measuring soil pressures on three thicknesses of blades, and extrapolating for the hypothetical pressure at zero blade thickness. The nature of the extrapolation was found to be exponential, with the slope theoretically inverse to the soil compression index Cc. In situ soil stresses measured in fine-grained soils generally agree with stresses from overburden pressures, elastic theory, and pressuremeters. Measured Ko's in natural soil deposits are generally within acceptable ranges, 0.5-1.5 depending on the consolidation state of the soil, and up to 4.2 in expansive clay. About 8-10 tests may be performed per hour; the test may not be reliable in dense sands. Directional horizontal stresses may be obtained with a three-bladed stepped vane.

Subject Headings: Soil pressure | Soil stress | Consolidated soils | Pressure measurement | Expansive soils | Field tests | Lateral pressure | Thickness | Iowa | United States

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