Citation

Shepard CH, Mason NE, Ray DJ. Highw. Res. Board bull. 1962; 309: 11-130.

Copyright

(Copyright © 1962, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

During construction of a highway cut through clays, silts, and sands of glacial outwash origin, the cut slope became very unstable. Extensive sloughing and erosion, with some slope movement, developed as excavation of the cut proceeded. A heavy flow of ground-water seepage developed in the cut slope. Drainage methods used to control this seepage are described. After excavation of the cut area was complete, further slow movement of the slope face was observed. Successive cross-sections showing rate and nature of movement are presented. Additional field explorations employing continuous sampling techniques were made to determine cause of movement.

METHODS of sampling and testing are described. Investigation revealed slickensides, resulting in low-strength zones, in a soil mass that had general high-shear strength. Also, a zone of soft low- strength elastic clay was disclosed at a critical location below subgrade. Observations indicated movement on a failure plane approaching the shape of a circular arc. Analyses by the swedish circular arc method and the critical height of slope method are discussed.

RESULTS of further study to determine the slope section required to attain stability are presented. Corrective treatment used is described, and principles and techniques used in this solution that are considered to have general application to similar problems are summarized. Pictures illustrate conditions from the beginning of construction to final completion of corrective work in september 1960.