Geotechnical characteristics some egyptian collapsing soils

This work is concerned with the study of some Egyptiancollapsing soils. The geology and occurence of collapsingsoils in the World and in Egypt are presented. Anexperimental programme included a total of 193 tests onundisturbed samples from 6 October City was carried out. Theresults were obtained from oedometer, shear box and triaxialtests.the main factors governing the behaviour of thetested soils were:inundation pressure, stress path (K ratio,where K=Q3/0!), the mode of inundation and using of backpressure as may be concluded from test results.Detailed investigation of the texture, chemical andmineralogical composition of the tested samples indicatedthat particle arrangement, skeleton grains, total solublesalt content and interparticle voids had important role indetermining the shear strength and collapse of this type ofsoil.Other soil characteristics and constitutive relationshipswere also presented.