The report deals with increments of resistance against circular slides in soft cohesive layers, which are brought by pipes penetrated into them. Amount of the increments depend upon strength of clay, and bending strength, embedded length from sliding surfaces and lateral deflection of pipes.Clayey strength determines them if embedded length is not long enough, in the other case, characters of pipes do.
　As long as foundation does not fail, its reaction to pipes are assummed in proportion to the lateral deflection according to Chang's idea, and they are assummed constant values, 9 times of the cohesion, after its failure according to Bengt B. Broms' idea.
　The increments are calculated in ranges of the cohesion between 1t/m2 and 6t/m2, of diametre of pipes between 40 cm and 100 cm, and of embedded length from sliding surfaces between 0.3/β and 3/β, here β is 4√Es/4EI. For convenience, they are figured as concentrated loads, applied on sliding surfaces, in this report, and you can compute the increasing resisting moment easy to multiply them by radii of sliding circles.