Study of Clay Shale Slopes along the Panama Canal. Report 3. Engineering Analyses of Slides and Strength Properties of Clay Shales along the Gaillard Cut.

This report summarizes the results of engineering studies and analyses which provide guidance on shear strength parameters applicable to the stability evaluation of existing slopes along the Gaillard Cut, the effects of future modifications, and evaluation of newly excavated slopes in clay shales. 128 undisturbed 6-in.-diam core samples of clay shales were obtained for laboratory testing from 10 borings at 9 sites along the Gaillard Cut. Piezometers and slope indicators were installed to monitor pore water pressures with depth, determine groundwater conditions, and detect slide movements. Material properties determined in the laboratory provided information on index properties, consolidation characteristics, and shear strength for the Culebra, Cucaracha, and La Boca formation. Existing shear strength data for these formations and the Las Cascadas formation and the Pedro Miguel agglomerate are incorporated, and comparisons made. Slope stability analyses of 98 past slides at 64 locations provided estimated shear strengths required for initial slides and reactivated slides during and after construction in all of the above formations. Comparisons are made with shear strengths from laboratory tests. Four active slopes investigated in the field were analyzed in detail to provide shear strengths required for stability under existing conditions. Engineering information on surface crack patterns, blockage depths of bore holes, surface movements, rainfall data, and groundwater levels was obtained.