![]() ![]() With this concern, the key controls on the formation of mudrocks, the terminology used to classify fine-grained sedimentary rocks and the main geological and geotechnical characteristics of mudrocks, including the relevant laboratory techniques are presented as well as the geological and engineering geological classifications of mudrocks are reviewed. This chapter aims to provide a framework of the main geological and engineering geological aspects of mudrocks that control their engineering properties and behaviour. ![]() Mudrocks can show a range of engineering behaviours as function of their composition and structural features however, by reputation, they are regarded as poor engineering materials in construction displaying low strength and durability as well as susceptibility to volume changes. ![]() As mudrocks constitute more than 60% of all sedimentary rocks and occur frequently in geological sequence, they are often encountered in construction sites either in their natural undisturbed state or as construction materials. Mudrocks are part of the broader group of soft rocks which correspond to fine-grained, clay-rich detrital sedimentary rocks. Soft rocks comprise the geological materials with poor mechanical characteristics that span the range between soils and hard rocks. For practical reasons soft rocks which are differentiated from soils due to engineering reasons through a UCS of 5 MPa approximately will no more be considered soft when reaching a uniaxial compression strength about that of a strong concrete, that is, approximately 27.5 MPa and a modulus ratio above 200:1. So harder rocks may be transformed into sot rocks or “altered” rocks. However, the transformation of hard rocks into soft is imposed by the inverse physical–chemical equilibrium conditions to which high PT minerals are easily transformed through weathering or when subjected to hydration under lower conditions of pressure and temperature (retro metamorphism, for example). Although reasonable, this is not a general rule since exceptions are found specially during the formation of chemical sedimentary rocks and by cementation effects by silica/iron rich oxides that may turn soft sands into very hard rocks. It is expected that the input of highly energetic pressure–temperature (PT) conditions should impose the formation of harder rocks in relation to those related to the origin of soft rocks. One may think that geological affiliation and environmental conditions of formations are the main hint to understand the mechanical properties of the rocks. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |