Introduction to Engineering Geology PDF

Engineering Geology It is a branch of geology that focuses on the application of geological principles, techniques, and knowledge to engineering practice. It involves the study of the Earth's materials, such as rocks, minerals, soil, and water, with the aim of providing a comprehensive understandi...

Engineering Geology It is a branch of geology that focuses on the application of geological principles, techniques, and knowledge to engineering practice. It involves the study of the Earth's materials, such as rocks, minerals, soil, and water, with the aim of providing a comprehensive understanding of the geological conditions at construction sites or areas of engineering interest. Geo = earth Logy = study of science William Smith- known as the Father of Civil Engineering and the Father of Historical Geology. He was a keen observer of the rocks in England. Geologists- concerned with understanding the nature of natural phenomena. Branches of Geology 1. Physical or dynamic (al) geology deals with the materials that constitute the earth, the structure and surface features of the earth, and the processes that have given the earth its present structure and appearance. 2. Historical geology deals with the history of the earth-its changing face and structure and the changing forms of living things whose remains or traces are found as fossils in the rocks. Important Fields of Geology 1. Mineralogy is the study of minerals, their composition, the ways in which they occur, their crystal structure, and their behavior. Minerals are the constituents of all soils, rocks, and ores. 2. Petrology is the study of the origin of rocks, their structures and textures, and their alteration. a. Petrography is the systematic description and classification of rocks. b. Sedimentation is a specialized branch of petrology that deals with the way in which sedimentary rocks are deposited in water, air, and ice. 3. Stratigraphy is the description and study of stratified rocks. It is concerned with the distribution, composition, thickness, age, variations, and correlation of rock strata. 4. Paleontology is the study of fossils, the remains and traces of the life of the past. 5. Structural Geology is concerned with the shape and configuration of the rocks in the crust of the earth. 6. Glacial Geology is the study of the cause, distribution, erosion, transportation, deposition, and other effects of the formation of large masses of ice on the continents. 7. Geomorphology means the study of the shape of the earth. It is specifically devoted to the description and origin of land forms. It is the systematic examination of land forms and the interpretation of them as records of past history. 8. Oceanography, the study of the oceans, includes investigation of the physiography and structure of the ocean basins, and the mechanism and nature of waves, tides, and oceanic circulations. It is concerned with the composition and variations in density of sea water, and with the past history of the oceans. 9. Meteorology is one branch of geology that has grown so fast it is often considered as a separate field. It is the study of the atmosphere, weather, and climates. The investigation of ancient climate is called Paleoclimatology. 10. Geophysics is a branch of experimental physics that deals with the structures, composition, and development of the earth, its atmosphere, and its hydrosphere. It includes geodesy, seismology, meteorology oceanography, and earth magnetism. 11. Terrestrial Magnetism is the study of the earth’s magnetic field- its causes, variations, and the history of changes that have taken place in the position of the field and the poles. 12. Seismology is devoted to the detection and interpretation of earthquake waves. These have proven to be our best means of investigating the structure and composition of the interior of the earth and the structure of that part of the crust that is not exposed to direct observation. 13. Geodesy is the investigation of any scientific questions connected with the shape and dimension of the earth. 14. Geochemistry is defined broadly to include all parts of geology that involve chemical changes. It may also be defined as the study of the relative and absolute abundances of the elements and of the atomic species, isotopes, in the earth, and the distribution and migration of the individual elements in the various parts of the earth. 15. Petroleum Geology is an applied field of geology in which the study of various other branches is brought to focus on the occurrence and migration of oil. 16. Economic Geology treats the origin, occurrence, and distribution of ore minerals and other economically important mineral and rock resources. 17. Engineering Geology is the application of geological sciences to engineering practice. The purpose is to assure that the geologic factors affecting the location, design, operation, and maintenance of engineering works are recognized and provided for. 18. Hydrology is the science of the distribution and phenomena related to the water on the surface of the earth. Groundwater geology is concerned specifically with the occurrence, distribution, movement, and action of underground water. 19. Agricultural Geology is the study of soils, especially of their depletion and erosion. 20. Military Geology is the application of geologic knowledge to warfare. Applications of Geology in Engineering 1. Site Investigation Geological surveys help identify potential risks such as landslides, earthquakes, or soil instability. Geological maps aid in selecting suitable locations for construction projects. 2. Foundation Design Understanding the underlying geology is crucial for designing stable foundations. Different soil and rock types have varying bearing capacities. 3. Tunneling and Excavation Geotechnical data guides the design of tunnels and excavations. Identification of weak or unstable strata is vital to prevent collapses. 4. Water Resource Management Geological studies help in locating and managing groundwater resources. Understanding aquifer properties is essential for well design. 5. Environmental Impact Assessment Geology is considered in assessing the impact of engineering projects on the environment. Mitigation measures are developed based on geological considerations. Challenges in Geology in Engineering 1. Uncertainty: Geological conditions can be highly variable, leading to uncertainties in predictions. Engineers must account for these uncertainties in their designs. 2. Human-Induced Changes: Construction activities can alter natural geological conditions. Proper planning and monitoring are essential to minimize negative impacts. Earth's Structures and Composition Size of the Earth Polar diameter = 7,900 miles Equatorial diameter = about 7,927 miles Circumference around the equator = approximately 24,900 miles Area of the earth's surface = about 197 million square miles, of which about 71 per cent is covered by oceans Volume of the earth = more than 250 billion cubic miles Mass = about 6,600 quintillion (6,600,000,000,000,000,000,000) tons. Shape of the Earth The earth is a geoid, a triaxial ellipsoid, nearly spherical but slightly flattened at the poles. Major Division of Earth 1. Lithosphere- the solid central zone 2. Hydrosphere- the water zone 3. Atmosphere- the gaseous envelope that surround the lithosphere and hydrosphere. 1. Internal Structure CRUST The outer part of the solid lithosphere composed mainly of rocks similar to those visible at the surface, extending down 20-30 miles. MANTLE Consist of two major zones presumed to be composed of rocky material under substantial pressure, adequate to keep it from melting at the high temperatures that prevail there. CORE The core is inner part of the earth having a diameter of 4,300 miles. Outer Core- 1,360 miles thick Inner Core- 1,580 miles in diameter 2. Earth's Composition Silicate Rocks: Common Minerals: Feldspar, quartz, mica. Occurrence: Abundant in the Earth's crust and mantle. Non-Silicate Rocks: Examples: Carbonates (e.g., limestone), oxides (e.g., hematite), sulfides (e.g., pyrite). Occurrence: Present in various geological settings. Minerals: Definition: Naturally occurring, inorganic substances with a defined chemical composition and crystalline structure. Diversity: Thousands of minerals, each with unique properties. 3. Earth's External Features Landforms: Types: Mountains, valleys, plains, plateaus, and more. Formation: Result from a combination of geological processes, including tectonic activity and erosion. Hydrological Features: Rivers, Lakes, Oceans: Carve landscapes, shape coastlines, and influence climate. Processes: Erosion, sedimentation, and the water cycle. Atmosphere: Composition: Nitrogen (78%), Oxygen (21%), traces of other gases. Function: Protects life, moderates temperature, and transports moisture. 4. Tectonic Processes Plate Tectonics: Concept: Earth's lithosphere divided into plates that move and interact at plate boundaries. Consequences: Earthquakes, volcanic activity, and the formation of mountain ranges. Volcanism: Origin: Magma rising from the mantle. Consequences: Formation of volcanic landforms, release of gases, and potential hazards. Earthquakes: Cause: Sudden release of energy along faults. Consequences: Ground shaking, surface rupture, and tsunamis. 5. Geological Time Eras are the major divisions of geologic time. 1. Precambrian- rock units are almost completely unfossiliferous. They contain scattered remains of algae an a few questionable fossils of such animals as jellyfishes or worms. 2. Paleozoic (old life) - a period of nearly 300 million years during which the marine invertebrates were abundant forms of life on earth. The first fish appeared about the middle of the Paleozoic Era, and the first amphibians and reptiles were present before its end. 3. Mesozoic (middle life) - a time of development for the land animals. The reptiles, particularly dinosaurs, dominated the earth, and birds, mammals, and modern plants evolved. At the end of the Mesozoic the dinosaurs become extinct, and more modern forms of life appeared. 4. Cenozoic (modern life) - mammals dominate the earth. Continental Drift and Plate Tectonics Understanding the concepts of continental drift and plate tectonics is fundamental to comprehending the dynamic processes shaping the Earth's surface. 1. Continental Drift A large-scale horizontal movement of continents relative to one another and to the ocean basins during one or more episodes of geologic time. Continental drift theory was given by Alfred Wegener in 1915. This theory has explained the origin of continents and ocean basins. According to Wegener, all the continents formed a single continental mass which is called “Pangaea'' which means all earth. This supercontinent was surrounded by a mega ocean called “Panthalassa '' meaning all water. Subsequently, Laurasia and Gondwanaland continued to break into various smaller continents that exist today. Thus, Wegener proposed that continents are floating and constantly drifting on the earth’s surface. 2. Plate Tectonics Plate tectonics is the theory that Earth’s outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like hard and rigid shells compared to Earth’s mantle. This strong outer layer is called the lithosphere. Plate tectonics affects humans in several important ways. - It causes earthquakes - It causes volcanism - It induces the recycling of elements within the biosphere and between the geosphere and biosphere - It causes mountain-building Types of Plate Boundaries: Divergent Boundaries: Plates move apart; new crust forms. Convergent Boundaries: Plates collide; one may subduct beneath the other. Transform Boundaries: Plates slide past each other horizontally. Evidence for Plate Tectonics: Seafloor Spreading: Mid-Atlantic Ridge exhibits volcanic activity and the creation of new oceanic crust. Subduction Zones: Trenches and volcanic arcs mark areas where one plate is forced beneath another. Subduction zone is a region in the earth’s crust where tectonic plates meet. Consequences of Plate Tectonics: Earthquakes: Result from the release of stress along faults. Earthquake- is a trembling or shaking of the ground caused by the sudden release of energy stored in the rocks beneath the earth’s surface. Seismology- is the study of earthquakes. Generating artificial earthquakes is one of the major methods employed in the search for petroleum.  Volcanism: Occurs at convergent and divergent boundaries. The term volcanism is derived from the name of the Roman God of fire, Vulcan. It denotes one of the major geologic processes and covers the origin, movement, and solidification of molten rock. Magma- it is the underground molten rock. Lava- it is the molten rock thrown out by a volcano. Vent- is the opening through which an eruption takes place. Crater- is a basin like depression over a vent at the summit of the cone. Volcanism- is one of the most dramatic evidences of the dynamic nature of the earth.  Mountain Building: Collisions at convergent boundaries lead to the formation of mountain ranges. Mountain building, also known as orogenesis, is a geological process that involves the formation and uplift of large, elevated landforms, known as mountains. These landforms are typically characterized by steep slopes, high elevations, and rugged terrain. Mountain building occurs due to the complex interactions of tectonic plate movements and geological forces. It is a fundamental aspect of Earth’s dynamic geology and has played a significant role in shaping the planet’s surface. 3. Driving Forces Mantle Convection: Convection is the process by which less dense material rises and more dense material sinks. The former is said to be more “buoyant” than the latter, and the vertical forces due to density difference are referred to as buoyancy forces. Mantle convection refers to the slow, but organized, creeping motion in the mantle, driven by buoyancy force. These forces arise primarily because of thermal expansion and contraction associated with temperature difference. Slab Pull and Ridge Push: Ridge Push – magma rises as the plates move apart. The magma cools to form a new plate material. As it cools it becomes denser and slides down away from the ridge. This causes other plates to move away from each other. Slab Pull – the denser plate sinks back into the mantle under the influence of gravity. It pulls the rest of the plate along behind it. 4. Implications for Earth's Surface Landform Evolution: The evolution of landforms refers to the different processes of transformation of one landform to the next, or the transformations of individual landforms once they are formulated. A landform goes through various stages of development- which are youth, maturity, and old age. Erosion and deposition are the two important parts of the evolution of landforms. The evolution depends on the geomorphic agents that include groundwater, glaciers, waves, and winds. Both the processes of erosion and deposition change the surface of the earth. Ocean Basin Formation: The five major ocean basins are the Atlantic, Southern, Arctic, Pacific, and Indian. The five major oceans (from largest to smallest) are the Pacific, Atlantic, Indian, Southern and Arctic. All ocean basins are formed from plate tectonic activity, weathering, and erosion. Seafloor spreading and subduction are the primary forms of plate tectonic activity that provide a pathway for molten rock to leave the earth's mantle and create a new oceanic crust. Distribution of Earthquakes and Volcanoes: Ring of Fire: Circum-Pacific region with frequent earthquakes and volcanic activity. 5. Human Impacts: Natural Hazards: Resource Formation: