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The Geosphere and Geochemistry
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Although more than 2,000 minerals are known, only approximately 25 rock-forming minerals make up most of Earth's crust. The nature of these minerals may be better understood with a knowledge of the elemental composition of the crust. Oxygen and silicon make up 49.5% and 25.7% by mass of Earth's crust, respectively. Therefore, most minerals are silicates such as quartz, SiO2, or orthoclase, KAlSi3O8. In descending order of abundance, the other elements in Earth's crust are aluminum (7.4%), iron (4.7%), calcium (3.6%), sodium (2.8%), potassium (2.6%), magnesium (2.1%), and other (1.6%). Table 14.1 summarizes the major kinds of minerals in Earth's crust.
Environmental Health Emergencies, Disasters, and Terrorism
Published in Herman Koren, Best Practices for Environmental Health, 2017
An earthquake occurs when two sides of a fault slip suddenly against each other and produce vibrations. A fault is a fracture in the rock or the crust of the Earth where the two sides are displaced against each other in a minor or major way. The slippage causes a shaking or vibration because of a sudden release of stored elastic energy from within the Earth and seismic waves (waves of energy) may be produced. Seismic shaking is not uniform. As the waves approach the ground surface and potentially travel through areas of loose soil, the amplitude of the waves will increase producing larger waves that may be far more damaging to structures than the original waves. Other earthquake hazards include ground failure and/or rupturing of the fault resulting in the creation of cracks, settlement of the soil, vertical shifting of the ground after large earthquakes, soil liquefaction, where the soil, in an area of sand and silt as well landfill areas, takes on the characteristics of a liquid during the shaking of an earthquake and flows like a liquid; this can cause enormous damage to any structures that are within this area. Aftershocks, which may occur for periods of time after the initial major shock, can be extremely damaging to structures and can cause additional injuries and deaths. (See endnotes 6, 8, 10.) Thousands of faults are currently present in California, the United States, and the rest of the world. There are thousands of earthquakes each year throughout the world.
Retaining walls
Published in Gopal Madabhushi, Centrifuge Modelling for Civil Engineers, 2015
Retaining walls are commonly used to hold a soil mass back, next to an excavation or earth fill. These can be used to form an artificial embankment that supports a railway or a roadway or to create space below ground level. There are different types of retaining walls, such as: Gravity retaining wallsFlexible, cantilever retaining wallsAnchored retaining wallsL-shaped wallsPropped or braced retaining walls
Parametric studies on two-tiered model fly ash wall
Published in International Journal of Geotechnical Engineering, 2022
A retaining wall is a geotechnical structure constructed to counteract the lateral earth pressure when a change in ground elevation is needed. For many years, retaining walls have been designed using traditional methods as gravity wall or cantilever wall. Such types of walls are essentially constructed using reinforced concrete. The demands for construction of taller retaining wall are increasing with the rapid development of urban infrastructure and growing restriction of space. However, with the increase in height, the cost of the retaining wall constructed using conventional methods increases rapidly. Therefore, there is a need for alternate arrangements for the construction of retaining walls. Reinforced earth wall is such structure which can be used to construct taller and economically feasible walls. These walls provide a different option to the standard retaining wall by improving its tensile strength. Several researchers (Anubhav and Basudhar 2011; Chalermyanont and Benson 2004; Karpurapu and Bathurst 1995; Kandolkar and Mandal 2015; Krieger and Thamm 1991; Lal and Mandal 2014b; Leshchinsky and Perry 1989; Mandal and Jambale 1992; Sawicki and Les̀niewska 1986, etc.) have carried out studies on MSE walls. Hatami, Bathurst and Pietro (2001) reported that the reinforcement load is influenced by the type of facing. Bathurst, Mitaya and Allen (2010) performed a full-scale test on reinforced soil wall and reported that compaction efforts and global reinforcement stiffness affect the deformations at the end of construction, considering other factors remain unchanged.
Simulation with Monte Carlo methods to find relationships between accumulated mechanical energy and atomic/nuclear radiation in piezoelectric rocks with focus on earthquakes
Published in Radiation Effects and Defects in Solids, 2022
Abouzar Bahari, Saeed Mohammadi, Mohammad Reza Benam, Zahra Sajjadi
Modern ideas on the mechanism of earthquakes began with the elastic rebound theory of H. F. Reid. According to this theory, the immediate source of an earthquake is a sudden release of elastic strain energy accumulated in the rock mass surrounding a pre-existing fracture in the earth's crust, known as a fault (46). Faults themselves occur when rocks break due to the forces acting on them. Stress may build up over a period of many years until the fault suddenly moves perhaps a few centimeters, or even a few meters. When this happens, it releases a huge amount of energy in an earthquake (47). Therefore, an earthquake is happened when either a pre-existing fault moves, or when an intact block of rock is under a huge stress value and suddenly it breaks, creating the faults. If we suppose that the stress is applied on a giant block of a brittle rock like granite, the elastic energy stored in the block can cause the earthquake.
Determination of critical phreatic level for landslide assessment using a scaled down laboratory model
Published in International Journal of Geotechnical Engineering, 2022
R. Ramkrishnan, Animesh Sharma, Karthik Viswanathan, D. Ravichandran
The term landslide refers to a form of slope stability failure characterized by massive ground movements of the earth, rocks, or debris under the effect of external factors like extreme precipitation and earthquakes, eventually resulting in various modes of mass movements such as rock-falls, slope failures, mud-flows or debris flows. Occurrences of landslides can be characterized as disastrous events as they often result in the loss of a multitude of resources and even human lives. The city of Coimbatore, Tamil Nadu is located on the banks of river Noyyal and is surrounded by Western Ghats (Sahayadri mountain range), which are frequently prone to landslides and slope failures, often during monsoons and thereby attributing the effect to changes in hydrological factors. Several other human factors can also be attributed to slope stability issues such as topographical variations induced due to human activities such as quarrying, mining, construction, etc. (Sajinkumar et al. 2014).