Peat soils exhibit strength and stiffness characteristics that are strongly influenced by extension and interlocking of fibers within the peat. Consequently, the in situ strength and stiffness characteristics of peat cannot be measured accurately with existing small-scale laboratory or field testing instruments. The use of an instrumented pile lateral load test is described for evaluation of the strength and stiffness characteristics of a peat deposit that had been exerting lateral stresses on existing pile foundations. Pile load tests were performed on two relatively flexible piles installed in approximately 45 to 50 ft of fibrous peat. Each pile was instrumented with both strain gauges and inclinometers. The piles were loaded laterally at the ground surface until displacements increased so quickly that additional loads could not be placed. At this point, the strength of the peat had been mobilized in a relatively large volume of soil in the vicinity of the pile. Interpretation of the strain gauge and inclinometer readings allowed definition of the deflected shapes of the piles and of the unit soil resistance profiles. Those deflected shapes allowed evaluation of the p-y behavior of the soil from which the strength and stiffness could be obtained. Those strength andstiffness values were consistent with those obtained for other peats and with the available results of a previously performed laboratory testing program. This paper appears in transportation research record no. 1278, Dynamic testing of aggregates and soils and lateral stress measurements 1990.
Samenvatting