Part I of this report focuses on the comparison of strength parameters of the loess soils of southeastern Washington obtained by laboratory triaxial shear testing and in situ testing using the Iowa Borehole Shear Test (IBST). Also, the disturbance of samples due to sampling technique is addressed. Loess samples tested with the IBST generally produce a lower cohesion but higher friction angle than if the same soils were tested by a UCU triaxial test. Also, the IBST produces a higher cohesion and a lower friction angle than a CU test. The failure envelopes tend to merge at higher normal stresses.
Part II of this report suggests drainage schemes to protect cut slopes in loess from rapid deterioration by erosion. This part of the report is a continuation of work completed under an earlier contract (WA-RD 69.1). Specific drainage schemes to divert surface water around or over cut slopes in loess are discussed.