Geotechnical characterization of residual granite soils. The test site of Polytechnic Institute of Guarda (Portugal)

The geotechnical characterization of residual soils is a complex matter and is not always successful because current interpretation methodologies dedicated to sedimentary soils do not adequately respond to the behavior of this type of soils. The problem has been under scope by several Portuguese and international institutions. The work carried out in the experimental Site of the Polytechnic Institute of Guarda (IPG) since 2003, constituted by residual soils and decomposed rocks of the local granite massif, is highlighted herein. The work was strongly supported by MOTA-ENGIL (Portuguese construction company) and the Laboratory of Math Engineering (LEMA, Polytechnic Institute of Porto). The characterization of the test site and the respective research work is presented. The research work involved interpretation of in situ tests (SDMT, SCPTu, PMT, SPT, DPSH, and geophysical tests), tests in controlled chambers (DMT, geophysical, and suction tests), and laboratory tests (oedometric tests, direct shear tests, and triaxial tests with several stress paths). The tests were performed on natural structured soils, artificially cemented mixtures, and unstructured soils. Advanced math and statistical analysis were applied in the development of new correlations to obtain geotechnical parameters representative of these soils. Furthermore, the work also allowed to recognize the physical characteristics of the materials and better understand their mechanical behavior.