China
Africa
Explore chapters and articles related to this topic
The Groundwater Geochemical System
Published in William J. Deutsch, Groundwater Geochemistry, 2020
The three basic rock types are classified by geologists as igneous, metamorphic, and sedimentary. Igneous rocks are formed from the solidification of molten material (magma) either deep within the earth’s crust to form granitic/gabbroic (silica rich/silica poor) rock types or at the surface to form basaltic/andesitic rock types. Metamorphic rocks (e.g., gneiss and schist) form at relatively high temperatures and pressures compared with earth surface conditions by the recrystallization of a rock without its undergoing melting. Sedimentary rocks form under surface or near-surface conditions. They are derived either from the accumulation of the physical weathering products of other rock types producing, for example, sandstones and shales, or from the accumulation of the shells and tests of organisms resulting in rocks such as limestone and chert. Approximately 75% of the continental rocks near the earth’s surface are sedimentary rocks or metamorphic rocks derived from sedimentary material with the remaining 25% being igneous rocks.15 Aquifers can be present in all the different rock types. In general, porous, intergranular flow will predominate in poorly cemented sedimentary rocks, and fracture flow will predominate in igneous and metamorphic rocks.
Petroleum Geological Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
The litho-logy of a rock unit is a description of its physical characteristics, rock type, origin, color, texture, grain size, mineral nature and composition, constituent distribution and rock structure. Litho-logy stratigraphy is based on subdividing rock sequences (layers) into individual litho-stratigraphic units. Originally the term ‘litho-logy’ was used for rock types. The three major rock types are sedimentary, metamorphic and igneous rocks. Stratigraphy distinguishes rock formation on the basis of litho-logy. A ‘rock formation’ is a distinct unit of the whole rock. A rock formation has particular litho-logical characteristics that differentiate the formation from other formations of the rock.
The geological origin of building stones
Published in John A. Hudson†, John W. Cosgrove, Understanding Building Stones and Stone Buildings, 2019
John A. Hudson†, John W. Cosgrove
There are two principal methods for determining the age of rocks. One is radiometric dating (or radioactive dating) which is based on the known decay rate of radioactive isotopes and compares the abundance of a naturally occurring radioactive isotope within the rock to the abundance of its decay products—giving, within error limits, an absolute age. The other is the law of superposition of strata which is based on the assumption that, in general, underlying strata were deposited before the overlying strata, and hence are older. Of course, this latter method of dating provides only the relative ages of the rocks.
Orange, Yellow, Brownish Stains and Alteration on White Marble at El Montazah in Alexandria, Egypt
Published in International Journal of Architectural Heritage, 2021
On the other hand, the white marble from statues at El Montazah site has a fairly homogeneous color ranging from white to off-white up to grey and contains several yellow to brown stains. The rock consists of calcite and small amounts of quartz, feldspar, as well as, small amounts of pyrite and hematite. The groundmass is interrupted by irregular pattern of dark grayish veins. These veins are more visible and more common, present as irregular wavy lines limited in length.
Experimental and analytical investigations on strength and deformation behaviour of red sandstone under conventional triaxial compression
Published in European Journal of Environmental and Civil Engineering, 2023
Hai-Ling Shi, Lun-Yang Zhao, Qi-Zhi Zhu
Sandstone, a typical sedimentary rock, is utilised in various geotechnical engineering, such as underground excavation, rock structures of hydraulic power station, oil gas drilling, etc. Understanding and modelling the mechanical behaviour of such rock is essentially important for stability and durability analyses of rock structures. In literatures were found many experimental and numerical studies on the mechanical behaviour of sandstone, including material strength (Zhang et al., 2009; Taheri et al., 2016; Armaghani et al., 2016; Wang et al., 2018b), deformation feature (Bésuelle et al., 2000; Zong et al., 2016; Kim et al., 2016; Liu et al., 2019), failure modes (Klein et al., 2001; Yang et al., 2012; Liu et al., 2020), multiphysical coupling (Abdulagatova et al., 2009; Vitel et al., 2016; Lu et al., 2017; Wang et al., 2021; Gao et al., 2022) and time-dependent behaviour (Tsai et al., 2008; Heap et al., 2009; Chen et al., 2019; Gholami et al., 2021), as well as various mathematic models (Wang et al., 2018a, 2020; Zha et al., 2021; Wang et al., 2022b). Complex loading path means, including true triaxial experiments, have also been extensively applied for the investigation of the sandstone in recent years (Yang & Jing, 2013; Wang et al., 2019; Zhang et al., 2020; Peng et al., 2021; Gao et al., 2022; Wang et al., 2022a). To capture the microstructure of sandstones and its impact on their macroscopic behaviour, some imaging techniques such as scanning electron microscopy (SEM) (Bésuelle et al., 2000; Liu et al., 2017b, 2021), optical microscopy (Veerle et al., 2009; Li et al., 2021), X-ray tomography (Bera et al., 2011; Yang et al., 2019) and digital photography (Song et al., 2013; Yang et al., 2020) have been applied. Limited by experimental conditions and techniques, the above-mentioned experimental studies were mostly performed in a small range of confining pressure. The present work is devoted to investigating the mechanical behaviour of red sandstone under a larger range of confining pressure through both experimental and numerical methods.
Nonlinear seepage–erosion coupled water inrush model for completely weathered granite
Published in Marine Georesources & Geotechnology, 2018
Jinquan Liu, Weizhong Chen, Diansen Yang, Jingqiang Yuan, Xiaofei Li, Qingyan Zhang
With the rapid development of transportation infrastructure, more and more tunnels are to be constructed in China. Unfavorable geology such as water-rich completely weathered granite, which is easy to induce water inrush disaster, is often encountered during the construction of subsea tunnels in southern China (Shin et al. 2011; Zhao, Li, and Tian 2013). Human casualties and property loss caused by water inrush are very serious at present. Tunneling in such conditions will be particularly difficult because of the potential for encountering mixed-face conditions, collapse, and erosion (Zhao, Gong, and Eisensten 2007; Zhang, Fang, and Lou 2014a; Shirlaw 2016). Over the last 40 years, much research has been devoted to studying the description, classification, weathering process, and engineering behavior of weathered rocks. Anon (1977) and Arıkan, Ulusay, and Aydın (2007) have developed a systematical description and classification of weathered rocks. Irfan (1997) studied the mineralogical characterization and classification of weathered granite. Six grades from fresh rock (Grade I) to residual soil (Grade VI) were adopted to classify weathered granites. The main minerals of fresh rock include quartz, feldspar, biotite, and hornblende. Weathering results in a loss of feldspar, leaving a material predominantly consisting of quartz particles and clay minerals such as kaolinite and montmorillonite as the weathering grade increases to completely weathered granite (Grade V). This material erodes rapidly and becomes weak and soil-like. Shirlaw, Hencher, and Zhao (2000) also claimed that the completely weathered rocks were prone to erosion when exposed because of little cementation. Under certain conditions, the quartz particles and clay minerals may be gradually eroded by groundwater flow, leading to the rapid increase in ground permeability and the formation of water channels, and ultimately the water inrush disaster. Undoubtedly, water inrush disasters have become a serious threat to the tunnel construction in completely weathered granite due to its special engineering behavior. So predicting the evolution of water inrush for an advance warning is very meaningful and urgent, but improvements in this area are seriously hindered due to the complexity of water inrush mechanisms.