Sedimentary argillaceous rocks play an important role in many areas of civil, mining and petroleum engineering. Rock slopes, dam foundations and abutments, underground storage facilities for nuclear waste and oil wells are examples of engineering structures that proper design procedures depend upon the knowledge of shale behavior. These rocks are the most common sedimentary rocks in nature which has led to much investigation on its origin, composition and structure. Fantastic geological, petrographic and geochemical knowledge on these rocks has been accumulated over the years. However, its complex behavior still poses great challenge when facing an engineering design exercise. This paper presents an overview of the significant properties of argillaceous rocks for engineering purpose and will cover laboratorial procedures for testing these materials for obtaining their mechanical, and mass transport properties. Test results and properties of argillaceous rocks from both onshore.
Argillaceous sedimentary rocks are the most common rock type in sedimentary basins. These rocks are formed by compaction and cementation of clastic, fine-grained sediments and its engineering behavior is highly dependant upon composition, micro-fabric and saturation state. Shale, mudrock, mudstone, claystone and marls are all sedimentary argillaceous rocks and to distinguish one from the other, it is required expertise in petrography, mineralogy and geochemistry. Weaver, , Blatt et al, , and many others, discuss the techniques available to identify the origin and composition of these rocks. Herein, the terminology suggested by Blatt et al , based upon fissility and grain size, will be used, see Table 1.
The presence of mudrocks greatly impacts the design and performance of engineering structures or processes developed in sedimentary basins. These rocks present very low permeability, have very small pore-size and special micro-fabric, with variable degree of cementation, and present a remarkable tendency to weaken when subjected to cycles of dryingwetting. Only for very few exceptions, these rocks have no major economical value as such but their behavior may affect substantially the economics of an engineering project. Table 1 – Classification of argillaceous rocks (Adapted from Blatt et al, 1980)
> 2/3 silt Silt – shale Siltstone 1/3 – 2/3silt Mud – shale Mudstone > 2/3 clay Clay – shale Claystone Civil works and mining engineering applications such as dam foundations, large slopes and cuts and underground excavations constituted the main challenges in the past. Early work dated 1916 on the slope failures during the construction of the Panama Canal, , points out the so-called Cucaracha beds (later on defined as Cucaracha shale), composed by weak clayformed rocks, as responsible for the major Culebra slides at Gaillard Cut. In spite of the fact that this report, , is pre-effective stress pr material was considered to be a major challenge for evaluating the failure processes.;
Slurry fracture injection is a process by which solid particulate wastes may be combined with waste fluids and injected at fracturing conditions into the deep subsurface for disposal. It holds a number of significant environmental advantages over traditional landfill disposal, and has been applied with increasing success for large volume waste di