in the triaxial test for measuring the shear-strength properties of soils, the specimen is enclosed in a rubber membrane and a paper filter drain is used to accelerate the removal of water during consolidation. a correction must be made to the observed stresses to allow for the restraint imposed by the rubber membrane and paper filter drain. for tests continued to large strain in which failure takes place along a single plane, such as occurs during the determination of residual strength on specimens containing a natural or pre-cut slip surface, the factors governing the restraint are complex and it is not possible to calculate the magnitude of the correction required. this report describes some experimental work to determine the correction necessary for the effect of the restraint of the membrane and filter drain for failure on a single plane inclined at an angle of 52 degrees to the horizontal. the tests were carried out using a cylindrical perspex specimen 38mm in diameter by 76mm in length (1 1/2 in x 3 in ) having a specially prepared shear plane on which the friction was reduced to a very small value. charts are given for the corrections to be applied to the shear and normal stress for a range of cell pressures. (a)

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