André Vervoort

Experimental and numerical study of the Kaiser effect in cyclic Brazilian tests with disk rotation

Sensitivity of the Kaiser effect to the deviations of the directions of s1-principal stress experienced by rock in successive loading cycles has an important impact on the application of this effect for stress measurements in rocks. The paper presents an analysis of the gradual Kaiser effect degradation with increasing deviation of the principal stress axes between loading cycles in Brazilian experiments. An experimental study was carried out to investigate the Kaiser effect in cyclic loading tests of disk specimens of a brittle limestone in diametrical compression with acoustic emission measurement. Tests were performed in which disks were loaded in two cycles without or with rotations between successive cycles. The rotation angle varied between 01 and 901. The Kaiser effect became gradually less pronounced with increasing rotation angle, but remained detectable for angles o101. Rotation by more than 101 resulted in complete disappearance of the effect. These experimental results were confirmed by numerical simulations using the displacement discontinuity method. r 2002 Elsevier Science Ltd. All rights reserved.

Deep soil mix technology in Belgium: effect of inclusions on design properties

The application of deep soil mix (DSM) technology in Belgium is sharply increasing. Next to soil improvement applications, DSM walls are extensively used for excavation support. Even permanent retaining and foundation applications with soil mix are increasingly applied. This paper gives an overview of the DSM procedures carried out in Belgium and deals with methodologies applied to determine the amount of soil inclusions, the elastic modulus and the compressive strength of DSM material. The influence of soil inclusions on the stiffness of DSM material is investigated with the help of numerical simulations. The methodologies are validated on a large population of laboratory tests on in situ DSM material, executed in Belgian soils. These research activities have been performed in the framework of the research program Soil Mix that the Belgian Building Research Institute (BBRI) carries out in collaboration with the Catholic University of Leuven and the Belgian Association of Foundation Contractors (ABEF). This research program is financially supported by the Agency for Innovation by Science and Technology of the Flemish Region IWT (BBRI, 2009-2013).