In this paper the geotechnical description of a halloysite clay, coming from boreholes performed in Barlovento Dam, is made. It is important to remark this material had a difficult behaviour during the performance of laboratory tests, clearly different of the materials Soil Mechanics usually treats with. The geotechnical description comprised the following aspects:
identification tests: the grain size and plasticity tests had to be made with different procedures of the ones described in the technical Spanish standards due to the special characteristic of the material;
X-Ray diffraction tests;
dry density and natural water content of the material;
strength tests that comprised dynamic penetration tests (SPT and DPSH test),triaxial and direct shear tests and pressuremeter tests made in the boreholes;
deformability tests that included oedometer and pressuremeter tests
permeability and dispersibility tests.