INTRODUCTION TO ENGINEERING GEOLOGY (StudyCivilEngg.com)

INTRODUCTION TO ENGINEERING GEOLOGY

SUBJECT : ENGINEERING GEOLOGY

INTRODUCTION

The planet earth is a dynamic planet, only of its kind in the solar system. According to the Ecological approach wherein we study the interaction between the living things and their environment we come across three segments with respect to the planet earth. These segments are Lithosphere, Hydrosphere and Atmosphere. Sine the subject matter of geology is related with the study of the solid earth and its interior, the Lithosphere becomes the most important segment for geology.

• Atmosphere: The gaseous layers surrounding the earth upto a distance of about 700 km is called atmosphere. The atmosphere is therefore a life supporting gas mantle, surrounding the earth.
• Hydrosphere: The entire collection of water over the earth a well as inside the earth is called the hydrosphere.
• Lithosphere: The solid earth and its interior is known as lithosphere. It is the uppermost 100 km layer extending towards the core of the earth from the top of the earth crust. It shows the presence of varieties of rocks, of different origin, which have been subjected to weathering. Lithosphere behaves in a dynamic manner and its behaviour is heterogeneous in nature. Thus, at some places, lithosphere is prone to volcanic eruptions and earthquakes. The study of these factors is a very fascinating subject.
• Biosphere: The earth is the only planet on which life has flourished. The biosphere includes innumerable large and small living beings, grouped into million of species.

BRANCHES OF GEOLOGY

The 'Geological Science' can be studied from different view points. Each aspect is considered as an arm of geology and thus geology is divided into different arms/branches:

• Petrology: An important branch of geology that deals with the occurrence, origin and history of rocks is known as petrology. The knowledge of basic properties of rocks and minerals constituting the earth's crust is necessary in geotechnical studies.
• Geomorphology/Physical Geology: This is a study of the processes that activate at or beneath the surface of the earth and the material on which those processes operate.
• Structural Geology: This is Wa branch of geology devoted to the study of rock deformation and geometry of rocks
• Historical Geology: Study of the chronology of the earth's past events, both biological and physical is covered in this branch.
• Hydrogeology: This is the geological aspect of surface and subsurface water. This aspect is very important in deciding stability of many civil engineering operations.
• Geophysics: This branch deals with the study of the application of the methods of physics to the properties of rocks and soils.
• Pedology: It is also known as soil science which is a study of the uppermost layers of the earth's crust.
• Engineering Geology: This branch is concerned with the application of geology to various engineering operations.

SCOPE OF ENGINEERING GEOLOGY

• Geology is branch of applied science and has major application in civil and mining engineering. Studying geological character the construction sites is essential for planning, design, construction, costing and safety of projects.
• Geological condition at sites can be studied by drilling or geophysical methods. Many times rock or soil excavated at a place is used as construction material at other places. Geological study provides necessary information about excavated material and its suitability.
• Negligence of geological conditions lead to rise in construction cost and may also face technical difficulties. Post construction performance of such sites is uncertain.

Example: Tigra dam in Madhya Pradesh is oldest dam in India constructed in 1917 across river Sank. This dam is masonry gravity structure. It is founded on sandstone alternated with thin bed of shale on downstream side with low angle. Low dipping bed at downstream direction passes water and generated uplift pressure, and caused dam to fail functionally. Srisailam dam, in Andhra Pradesh, 139 m high masonry construction across the river Krishna is best example of how geology affects the structure.

• Horizontal bed of quartzite and shale are present at dam site. Quartzite can sustain load because it has high strength, but shale can’t sustain. For structural stability, shale beds were excavated and that portion filled with concrete. 

IMPORTANCE OF GEOLOGY IN CIVIL ENGINEERING

• Engineering geology is concerned with the applications of geology to civil, mining and water resources engineering. All the civil engineering structures, small or large, are constructed either on rocks or soil material. It is essential to study these earth materials in neatly details.
• The recent natural hazards have given enough evidence that every person must possess basic knowledge about the earth and its processes. It is seen that geology has contributed a great deal to civilization, both intellectually and economically. Among the most important of them are an understanding of the great age of the earth and the development of an absolute time scale.
• Geology differs from most of the other sciences, in that, it is concerned with absolute time which extends back almost five billion years when the earth was formed. Thus, as compared to human life span (approximately 60 years), geology is concerned with immense length of time. In this field, results of the experiments conducted by earth and other forces seen in the form of different rocks, structures, fossils etc. Some of the experiments are still going on, i.e. earthquakes, volcanism, landslides etc. In other words, geologists start with the results and with the help of qualitative and quantitative analysis of these results, they try find out the causes.
• Geology is a field science. Understanding of geologic knowledge is required to locate exploit mineral resources. Except water, other resources are non-renewable (for example, petroleum, coal, metals etc.). Thus, only after discoveries of these precious resources, our civilization has undergone revolution. In the modern urbanization era, development of big cities has resulted in the construction of large structures like high rise buildings, dams etc. Geology helps in-designing foundations for these structures. However, experiences suggest that, detailed investigation has seldom been carried out. Dams fail because they are built on permeable foundations. Similarly, seismic micro zonation required before the process of urbanization.
• Geology is based mainly on observations and seeks to determine history of the earth by these observations using other sciences like physics, chemistry, biology and mathematics scale of most geologic problems prevents laboratory study i.e. one cannot study a volcano in the laboratory. In this, the most important factor is geologic time, which cannot be studied in the laboratory. One must also understand limitations of the study. The surface exposures can be studied in greater details with satisfactory results. The same can be said of shallow sub-surfaces studies.
• However, deeper sub-surface studies are to be carried out with the help of geophysical methods. In this, the information received is in the form of magnetic, and electric properties of rocks, velocity of sound waves etc. In other words, interpretation of this information varies from person to person. Hence, the same information may be interpreted in different ways by different persons producing heterogeneity in the results.

FAQs COVERED IN THIS POST

What are the branches of Engineering Geology?

What is Petrology?

What is Geomorphology?

What is Pedology?

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What is the importance of Geology in Civil Engineering?

Write the Introduction to Geology

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