Selected geotechnical issues related to the foundation of drilling rigs

Abstract

This article presents selected geotechnical issues occurring at the foundation of drilling rigs for geological works included in the Operation Plan of a company performing geological works, in the aspect of designing and construction of their foundations and a yard. In the construction of drilling equipment, at least two main zones can be distinguished, often requiring separate foundations for individual machines: the zone near the borehole, including crane components, mast and drill pipe drive, and the so-called machine hall zone, including drive units and elements of mud system. The machine foundation is designed to mount a particular type of machine on it in order to transfer to the ground the static and dynamic loads generated during the movement of the machine. In particular, the current legislation, technical literature and standards were reviewed, especially: API recommended practice 51R and 4G, Working platforms for tracked plant, Eurocode 7 PN-EN 1997-2:2009 Standard. The values of safe bearing capacity of some soils and the magnitude of pressures generated by static and dynamic loads of selected drilling equipment were presented, which can be useful for preliminary assessment of the location of drilling equipment in the field and selection of surface and type of foundations. Typical examples of foundation of drilling rigs in various geotechnical conditions on direct foundations with the use of prefabricated elements such as reinforced concrete road slabs, wooden slabs and composite slabs based on HDPE plastic or on indirect ones with the use of micropiles were described. The following essential elements of the process of geotechnical design of the foundation of drilling rigs and their execution were indicated. According to legal regulations, the form of presentation of geotechnical foundation conditions and the scope of necessary tests should depend on assigning the building structure to a proper geotechnical category, which for practical purposes is tabulated in this article. The design and construction of foundations for drilling rigs should ensure, among other things, that their intrinsic vibrations are sufficiently different from those induced by subassemblies of the rig, that the vibration amplitudes are smaller than permissible, and that the foundations of individual machines are adequately separated from each other and from the rest of the facilities (yard). Conclusions on the safe foundation of drilling rigs on the ground, including, among others, the strengthening of the ground, design of independent building structures such as foundations for drilling rigs and their execution and removal were presented.