MODULE 1. GENERAL GEOLOGY

GEOLOGY IN CIVIL ENGINEERING

The importance of geology in civil engineering can be outlined as follows:

Geology provides a systematic study of the structure and properties of construction materials and their occurrence.
Geology provides knowledge about the site used in construction of buildings, dams, tunnels, tanks, reservoirs, highways, and bridges.
Geology helps to identify area susceptible to failures due to geological hazards.
The knowledge about the nature of the rock is very necessary for tunneling and constructing roads.
The foundation problems of dams, bridges, and buildings are directly related to the geology of the area.
The knowledge of groundwater is necessary for connection with excavation and other water works.
Geological map helps in planning civil engineering projects.
Geology helps in determining earthquake prone areas.
The knowledge of erosion, transportation, and deposition by surface water helps soil conservation, river control, coastal and harbor works.
A geological survey before starting a project will reduce overall cost.

BRANCHES OF GEOLOGY

Geology is divided into different branches, which are as follows:

Mineralogy – It deals with the study of minerals and their chemical structure.
Petrology – It deals with the study of how rocks are formed including their classifications.
Geochemistry – This field deals with the application of chemistry to geology such as the chemical composition of earth layers and recycling of minerals.
Economic Geology – It deals with the study of minerals, ores, and fossil fuels.
Volcanology – It deals with geologic processes involving volcanic activity.
Seismology – It is the study of earthquakes and similar phenomena.
Astrogeology – This study deals with the geology of extraterrestrial bodies in outer space such as asteroids, planets, and their moons.
Structural Geology – It deals with the study of the 3D geometry of rocks to explain their deformation processes.
Topography – It is the study of the earth’s surface that shows a detailed mapping of landforms and other earth’s physical features such as rivers, lakes, mountains, hills plateaus, and plains.
Engineering Geology – This refers to the application of geology to ensure a safe and structurally stable design of any civil engineering project.

EARTH'S STRUCTURE AND COMPOSITION

Based on relative position. Density and earth’s composition, the earth is subdivided into three layers. These are the crust, mantle, and core.

The crust is the outermost layer of the earth, and there are two fundamentally different types of crust—oceanic crust, which underlies the seafloor, and continental crust, which underlies continents.
The mantle of the Earth is the largest layer of the earth surrounding the core, making up 84% of the earth’s total volume. It is composed mainly of iron and magnesium silicates and is divided into four layers - the upper mantle, transition zone, lower mantle, and D double prime.
The earth’s core consists of two layers – the outer core which is mostly composed of liquid iron and nickel, and the inner core which is composed of solid iron alloy.
At the base of every layer, there are boundaries separating them which are as follows: (1) Moho Discontinuity (Crust-Mantle Boundary), (2) Gutenberg Discontinuity (Core-Mantle Boundary), and (3) Bullen Discontinuity (Outer-Inner Core Boundary).

Elementary knowledge on continental drift and plate tectonics

Alfred Wegener, a German meteorologist, proposed the hypothesis of continental drift. His assumption was that the continents were once fit together like pieces of a giant jigsaw puzzle, to make one vast supercontinent. He suggested that this supercontinent, which he named Pangaea, later fragmented into separate continents that drifted apart, moving slowly to their present position. Some of Wegener’s arguments that led him to formulate his hypothesis of continental drift include continental puzzle, fossil evidence, matching rock types and structures, and ancient climates or distribution of climatic belts.

New studies defined the types of plate boundaries, constrained plate motions, related plate motions to earthquakes and volcanoes, showed how plate interactions can explain mountain belts and seamount chains, and outlined the history of past plate motions. From these, the modern theory of plate tectonics evolved. Plate tectonics is a theory which states that Earth’s rigid outer shell is broken into plates made up of the crust and upper mantle known as lithosphere.

The breaks between plates are known as plate boundaries which are extended deep into the lithosphere. There are three types of plate boundaries which are as follows: (1) Divergent Boundaries, (2) Convergent Boundaries, and (3) Transform Boundaries.

CONVERGENT BOUNDARY

DIVERGENT BOUNDARY

TRANSVERSE BOUNDARY

EARTH PROCESSES

Weathering refers to the combination of processes that break up and corrode solid rock, eventually transforming t into sediment. Nature can attack rocks via two types of weathering: physical and chemical. Physical weathering, sometimes referred to as mechanical weathering, breaks intact rock into unconnected clasts (grains or chunks), collectively called debris or detritus. Chemical weathering, on the other hand, refers to the many chemical reactions that alter or destroy minerals when rock comes in contact with water solutions and/or air. Both physical and chemical weathering can happen simultaneously, aiding one another in disintegrating rock to form sediment.

Concerning all aspects of the Earth’s structure, composition, physical properties, constituent rocks and minerals, and surficial features, the effects of natural agencies are constantly modifying the physical Earth. These effects include the Geological Work of River, Wind, and Seas. The said geological works are broadly divided into three phases: erosion, transport, and sedimentation. These geologic processes are also of significant importance in various engineering professions especially in the field of civil engineering.

An earthquake is an intense shaking of the Earth’s surface caused by movements in the Earth’s outermost layer. Seismologists distinguish among different types of seismic waves, on the basis of where and how the waves move. Earthquakes cause devastation because ground shaking topples buildings, and it can also be worsened by landslides, tsunamis, and sediment liquefaction triggered by the shaking. We can mitigate or diminish the consequences of earthquakes by taking sensible precautions. In relation to civil engineering, buildings and bridges should be constructed so they are able to withstand vibrations without collapsing.

Prospecting – ground water: Importance in civil engineering

Water is a fundamental part of life, and the need for water is strongly ascending due to the following developmental activities such as population growth, urbanization, and industrialization. In order to have effective utilization of groundwater resources, groundwater investigation or exploration needs to be performed. It is because groundwater is of vital importance for different water supply purposes in both urban and rural areas,

Groundwater exploration is a typical task of an engineer to determine the place or location of the availability of groundwater. It can be made through direct or indirect means of exploration. One of the most common direct approaches used is test drilling. However, engineers find it expensive to use, so more and more techniques have been developed to explore the groundwater. These include the surface methods and subsurface methods. The surface methods of groundwater exploration are subdivided into different types: Esoteric method, Geomorphological method, Geological and Structural Methods, Soil and micro-biological method, Remote sensing techniques, and Surface geophysical method.

On the other hand, the main geophysical methods used in solving problems concerning hydrogeology include the gravity method, magnetic method, electrical resistivity method, and seismic method.

assignment/s submitted in module 1

coursework#1

Coursework #1_BARTOLOME.docx

reflection:

Geology does not address only the academic question such as the formation and composition of Earth, but it also addresses the practical problems especially those that are concerned or involving the expertise of civil engineering. After watching the presentation that my groupmates have presented, I learned that it is important for civil engineers to study the structure of the earth for us to correctly execute and ensure a safe and cost-effective design in our future construction projects. Thus, studying geology in engineering context gave me an holistic approach on how to interpret the surroundings, especially the variability of soil and rock. It is because the principles tackled in this subject will help me to determine the properties of soil or mineral, and when handling large construction projects, I might create a safer structure through seismic retrofitting or avoiding construction on lands underlain by weak soil (prone to liquefaction). Lastly, I have learned that it is highly significant for us on how to conduct groundwater investigation or exploration. It is because a near surface groundwater might affect the strength characteristics of a soil, and is considered dangerous when a nearby structure is built. Knowing different methods of groundwater exploration would be of great help for us to find out the flow or behavior of groundwater.

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