China
Africa
Explore chapters and articles related to this topic
Soil and rock strength
Published in Burt G. Look, Earthworks, 2023
Three types of rocks are formed from different processes (Figure 6.1-1): Sedimentary rocks are the most common rock types found at the earth’s surface and sea floor. They are formed from soil sediments or organic remains of plants and animals, which have been lithified under significant heat and pressure of the overburden, or by chemical reactions. This rock type tends to be bedded.Igneous rocks are formed when hot, molten rock solidifies. They are also known as primary rocks and are classified mainly on their mineral content and texture.Metamorphic rocks are formed from other rock types when they undergo pressure and/or temperature changes. Metamorphic rocks are classified as either foliated or non-foliated.
Rocks and rock minerals
Published in Ivan Gratchev, Rock Mechanics Through Project-Based Learning, 2019
When rocks are subjected to high temperatures and pressures, their texture and mineralogy may change so dramatically as to create a new type of rock: a metamorphic rock. Under high temperatures and pressures, the porosity of rock decreases, its strength increases and the unit weight of the solid material increases due to the loss of chemically bound water. In addition, many metamorphic rocks develop a strong directional structure (anisotropy), in which rock properties (strength, Young’s modulus etc.) depend on direction. In such metamorphic rocks (e.g., slates and schists), new minerals are developed and arranged in a parallel order, forming foliation.
Recognising the different types of building stone
Published in John A. Hudson†, John W. Cosgrove, Understanding Building Stones and Stone Buildings, 2019
John A. Hudson†, John W. Cosgrove
Typical examples of metamorphic rocks are marbles, slates, schists and gneisses. Marble is produced by the metamorphism of limestone by heat and stress. The dominant mineral constituent of the limestone, calcium carbonate, recrystallises to form an interlocking mosaic of crystals, thus destroying any original porosity, primary sedimentary textures including bedding, and any fossil shell the rock contained. Thus, if a rock visibly contains shells, it should be termed a limestone and not a marble. However, non-geologists use the term much more loosely and many well-known limestones are termed ‘marble’ by architects and builders (e.g., the Purbeck marble, Fig. 3.27) even when the limestone is unmetamorphosed, as indicated by the fossil shell content.
Assessing groundwater quality and health risks of fluoride pollution in the Shasler Vagu (SV) watershed of Nalgonda, India
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Narsimha Adimalla, Sudheer Kumar Marsetty, Panpan Xu
Shasler Vagu (SV) watershed is located in the southwest of Nalgonda district, India in between north latitudes from 16°55' to 17°00' and east longitudes from 78°45' to 79°10'. The study area falls in the Survey of India Toposheet Nos. 56 L/13 and 56 P/1 and covering an area of about 365 km2. Geologically, the study region is underline by Peninsular Gneissic Complex (PGC), and the dominant rock type are of granite and granite gneiss. Younger intrusive include gabbro, dolerite and hornblendite, apatite, pegmatite, quartz and epidote veins, and alluvium. Older metamorphic rocks include hornblende schists, amphibolites, banded magnetite quartzite, meta-basalt, and biotite schist. In the investigated area, biotite schist rock occurs as lenses, schlieren, and inclusion within the migmatitic gneisses. The exposures of biotite schist are oval shaped trending NNW-SSE in the study area. Low-grade metamorphosed basic igneous rock occurs as enclaves within the porphyritic granite, while banded magnetite quartzite is narrow bands trending NW-SE. Hornblende and amphibolite schist are mainly consisted of hornblende and plagioclase as an essential mineral, while quartz, sphene, sericite, and magnetite occur as accessory minerals. These rocks occur as elongated in N–S direction with vertical dip. The migmatite rocks are medium to coarse-grained in nature and are well exposed, while biotite gneisses are generally banded in nature and occur as sheets and inselbergs in low topographic areas (CGWB 2013; Sudheer Kumar et al. 2017).