Some Experience in the Execution, QA and QC of Deep Foundations in Weak Rock in Slovenia

摘要

The paper deals with some geotechnical problems which were encountered in the construction of deep foundations for structures that have been under construction over the fast two years along the demanding, 16.8 km long Vransko-Blagovica section of the southeast-northwest motorway link, which is part of the Slovenian National Motorway Construction Programme. Along this section the motorway runs across morphologically very varied hilly ground, so that 13 viaducts, 18 bridges, and 5 tunnels, as well as many retaining and supporting structures up to 12 m high, are needed. The bedrock consists mainly of weak, tectonically altered Carboniferous - Permian rocks, which are predominantly clayey schists, siltstones and sandstones. To assist in the design of this motorway section and its structures, over 13,000 metres of trial boreholes, as well as various field and laboratory tests, were executed. A general geological description of the area is presented, together with some of the strength and deformation characteristics of the typical rock types. An example of the deep, piled and caissoned foundations which were needed for the construction of a viaduct is presented, including the assembly of geotechnical data and the execution of the works. Some geotechnical problems, which were encountered during the construction of an anchored piled wall are also presented, with emphasis on the results of geotechnical monitoring obtained during and after construction. Conformity between predicted and actual in-situ geotechnical conditions was verified by means of quality assurance/quality control procedures, according to the programme specified in the National Motorway Construction Programme.