GEOLOGY FOR CIVIL ENGINEERS
GENERAL GEOLOGY
- Any rock which is hard and strong may weaken when it is exposed to the atmosphere, ultimately making the rock unfit to be at the site of foundation or to be used as a construction material. - Details of the response of different minerals which constitute the rocks will give the proper understanding of the weathering phenomenon. Hence the weathering of rocks is studied in General Geology
Importance of Geology in Civil Engineering
- Before constructing roads, bridges, tunnels, tanks, reservoirs and buildings, selection of site is important from the point of stability of foundation. - Geology provides a systematic knowledge of construction materials and their properties. - The knowledge about the nature of the rocks in tunneling and construction of roads. - The foundation problems of dams, bridges and buildings are directly related with geology of the area where they are to be built. - The knowledge of ground water is necessary in connection with excavation works, water supply, irrigation and many other purposes. - The knowledge of Erosion, Transportation and Deposition (ETD) by surface water helps in soil conservation and river control. - Geological maps and sections help considerably in planning many engineering projects. - If the geological features like faults, joints, beds, folds are found, they have to be suitably treated. Hence, the stability of the rock structures is important. - Pre-geological survey of the area concerned reduces the cost of planning work.
SCOPE OF GEOLOGY
- Geology provides necessary information about the construction materials at the site used in the construction of buildings, dams, tunnels, tanks, reservoirs, highways and bridges. - Geological information is most important in planning stage, design phase, and construction phase of an engineering project.
EXOGENOUS GEOLOGICAL AGENTS (Case study Example)
- Himalayan rivers i.e., Ganga, Indus and Brahmaputra physically transport 1 million tons of sediments daily. - Southwest monsoon winds transport over 130,000 tons of salt particles annually from run of Kutch toward Rjasthan. - Glaciers also do work of such magnitude even they are capable of transporting huge boulders many meters in diameter
PALEONTOLOGY
- If, under favorable condition, animals and plants life gets embedded in sediments, it will be preserved partly or completely such remnants of ancient life preserved in rocks by natural processes are known as Fossils. - Details of mode of formation of fossil, their types, occurrence etc. form the subject matter of paleontology. It is not of much importance from civil engineering point of view.
MINERALOGY
- It deals with the study of minerals - It deals with the detailed mode of formation, composition, occurrence, types, association, properties, uses etc.
TROPOSPHERE
- It is the lowermost zone of the atmosphere rising from the surface of the earth extending on an average to a height of 20 km.
STRATOSPHERE
- It is the second layer of the atmosphere starting from the tropopause and extending up to an average height of 50 km. - The temperature becomes constant for a height of 20 km (above tropopause) and then starts increasing. - The ozone layer starts at a height of 9km above the surface and continues up to 35 km.
Geology plays a very important role in the field of civil engineering.
- It provides knowledge about materials used for construction. - Its knowledge is helpful for constructing dams. - Geotechnical engineers needs knowledge about this subject for excavation work (digging work). - Its knowledge is required for foundation faults - For design of highways and roads - In construction of tunnels - Soil tests are done before any project begins - Its knowledge is helpful for river control and shipping work - Nature of soil materials can be found out
GEO HYDROLOGY
- May also be called Hydrogeology. It deals with occurrence, movement and nature i.e., (quality and quantity) of ground water in an area. - This branch is closely related to geology because the very existence movement of ground water are directly related to porosity, permeability, structure, texture and composition of ground water and underground rocks.
ECONOMIC GEOLOGY
- Minerals can be grouped into rock forming minerals and economic mineral. Some of the economic minerals like talc, graphite, mica, asbestos, gypsum, magnetite and diamond are useful as raw materials in some industries. - Some others like hematite, chromite, galena and pyrolusite are used for ore extraction of various metals. - The prosperity of a nation depends to a large extent of rich reserves of economical mineral deposits. - Gulf countries are rich because of their oil deposit. - South Africa is rich because of its gold and diamond deposits. - It deals with the mode of formation, occurrence, classification, association, varieties and concentration, properties and uses, etc. - It is related to economic importance. It is not relevant to civil engineering point of view.
EXOGENOUS GEOLOGICAL AGENTS
- The agents originated on the earth's surface, work slowly but steadily and erase topographic irregularities i.e., ups and downs on the surface. - The geological work in a way is systematic, i.e., commencement with erosion is followed by transportation and deposition.
PETROLOGY
- The composition and texture characteristics of rocks primarily contribute to their strength and durability. - Rocks based on their suitability can be used for foundation for dams, tunnels and construction materials. Hence it is the most important branch of Geology from civil Engineering point of view.
EXOGENOUS GEOLOGICAL AGENTS
- The erosion process causes the disappearance of land mass like hills. - The deposition process causes the disappearance of depressed land mass like pit, lakes and sea. - Rivers, wind, glaciers, tides and waves of sea are typical example of exogenous agents.
ENDOGENOUS GEOLOGICAL AGENTS
- The nature, origin and function of endogenous geological agents are in principal opposite to exogenous geological agents. They originated below the earth surface, work suddenly and create topographic irregularities. - Volcanoes, earthquakes, ground water and tectonic forces are typical example.
STRUCTURAL GEOLOGY
- The rocks which forms the earth's crust undergoes various deformation, dislocations and disturbances under the influence of tectonic plates forces. - The result is the occurrence of geological structures like folds, faults, joints and unconformities in the rocks. - The detailed mode of formation, causes, types classification, importance etc
GEOPHYSICS
- The study of physical properties like density and magnetism of earth. - It is sub-divided into Pure geophysics and Exploration geophysics.
GEO CHEMISTRY
- This branch is relatively more recent and deals with occurrence, distribution, abundance, mobility, etc., of different elements on the earth crust. - It is not important from the civil engineering point of view.
MINING GEOLOGY
- This deals with the application of geological knowledge in the field of mining. - A mining engineer is interested in the mode of occurrence of ores, their association, tenor, properties, etc. - It is also necessary to know other physical parameter like depth, direction(strike), inclination (dip) thickness and ore bodies.
There are three types of weathering namely:
1. Mechanical weathering 2. Chemical weathering 3. Biological weathering
STRUCTURAL GEOLOGY
Civil Engineering point of view - Geological structures modified the inherent characteristics of rock rendering them more suitable or unsuitable for civil engineering purpose. - Dame site sedimentary rocks with upstream dip provided a desirable geological setup while the same rock with down stream dip make geological setup undesirable.
MINERALOGY
Civil Engineering point of view The strength and durability of the material depends on chemical composition. The quartzite and marble resemble one another in shine color and appearance but quartzite by virtue of its mineral composition is very hard, tough, strong and durable while the marble disintegrates and decomposes in a short period because of its mineral composition and properties.
PURE GEOPHYSICS
Deals with general aspects of earth as a whole
EXPLORATION GEOPHYSICS
Deals with the study of upper layer of the earth's crust in order to solve civil engineering problem and locating oil, gas and ground water, explore and estimate the ore deposit.
GEOLOGY
Geology is the science of the earth GEO = Earth LOGY = Study of science - It deals with the study of origin, age, interior structure and history of earth - Evolution and modification of various surface features like rivers, mountains and Lakes. - Material that makes up the earth
TROPOPAUSE
Its upper boundary about 9km above the poles and at 18 km above the equator
EXOGENOUS GEOLOGICAL AGENTS
On hills, due to erosion, rocks are broken down into smaller pieces, which are transported and deposited in the depression
PETROLOGY
Petrology deals with the study of Rocks. Petro = Rock Logos = Study of Science - The earth's crust is also called lithosphere, which is made of different types of rocks. - Petrology deals with the formation, structure, texture, composition, occurrence, types etc.
HISTORICAL GEOLOGY
The earth surface was always suitable condition for the deposition of sediments at some place or other place. Therefore there are sedimentary rocks on earth representing the entire period of the earth's history. Proper investigation of this rocks reveals the chronological sequence of formation of rocks, evolution, migration and plants and animals life during different period of the earth history.
GEOLOGICAL AGENTS
The natural forces which are responsible for the visible changes on the earth's surface are called Geological agents. Based on their origin these natural forces can be grouped into two types - Exogenous - Endogenous
ATMOSPHERE
The outer gaseous part of the Earth starting from the surface and extending as far as 700 km and even beyond is termed atmosphere.
GEO CHEMISTRY
The process by which rocks are broken down and decomposed by action of external agencies such as wind, rivers, rain, temperature changes is called weathering
HISTORICAL GEOLOGY
These kind of study of the earth's history through sedimentary rocks is called historical geology.
ENGINEERING GEOLOGY
This deals with the application of geological knowledge in the field of civil engineering for execution of safe, stable and economic construction like dams, bridges and tunnels.
PHYSICAL GEOLOGY
This is also called Dynamic geology or Geomorphology. - Physical Geology deals with the different physical features of the earth such as mountain, rivers, lakes, glaciers and volcanoes. - It also deals with different changes occurring on the earth's surface like marine formation or disappearance of rivers, spring and lakes - Natural phenomena like land slides, earthquake and weathering. - Geological works of wind, glaciers, rivers, oceans, ground water and their role in constantly molding of earth surface.
