Stability of deep cuts in soft estuarine clays : Bell, R A; Theissen, J R; Tsai, K W Proc 10th International Conference on Soil Mechanics and Foundation Engineering, Stockholm, 15–19 June 1981V3, P353–356. Publ Rotterdam: A. A. Balkema, 1981

Abstract

Increased development of reclaimed tidal marshland will require deeper excavations than previously attempted in such soils. This paper describes analysis to design stable slopes for an 8,5 M deep excavation in San Francisco bay mud. Published strength correction factors and observed strength variations due to testing procedures, topographic features and construction activities were incorporated in analysis to improve predictions. Based on the results of these studies it is concluded: (1) seemingly insignificant strength reductions (within the scatter of test data) caused by such topographic features as former sloughs or construction traffic may influence stability of planned slopes, (2) use of percentage strength correction factors on bay mud soils may underestimate soil strengths at depth due to inappropriate reduction of the ratio, (3) small diameter laboratory van shears tests of bay mud soils may overestimate actual strengths by approximately 45 per cent, (4) lower bound test results may provide a reasonable first approximation of actual in situ strengths of bay mud soils, provided sufficient data exist to yield a representative strength envelope. (TRRL)