Copyright January, Prof. Basuony El-Garhy Geotechnical Engineering and Foundations Civil Engineering Department Faculty of Engineering Types of Rocks

Engineering Geology  Geology is the science of rocks, minerals, soils, and subsurface water, including the study of their formation, structure, and behavior. 2-1  Engineering Geology is the branch that deals with the application of geologic principles to engineering works.  The professions of engineering geology, and geotechnical engineering are complementary, and work as a team

What are Rocks?  A rock is a naturally occurring solid mixture of one or more minerals, or organic matter 2-2  Rocks change over time through the rock cycle  Rocks are classified by how they are formed, their composition, and texture

The Rock Cycle  Rock cycle includes many processes acting simultaneously. The most important of these begin with molten magma from within the earth forming into rock, then continue with rocks being broken down into soil, and that soil being converted back into rock. 2-3

3 Types of Rocks  There are three main types of rocks: 1.Igneous: formed when molten rock cools. 2.Sedimentary: formed by the “cementing together” of small grains of sediment. 3.Metamorphic: rocks changed by the effect of heat and pressure.

 These are rocks formed by the cooling of molten rock (magma.) magma volcano Magma cools and solidifies forming igneous rocks Igneous Rocks 4

5  Intrusive Igneous Rocks: Igneous Rocks  Magma pushes into surrounding rock below the Earth’s surface  Slow cooling deep beneath the Earth’s surface allows crystals to grow to large size

5 Igneous Rocks  forms when magma rapid cooling near or at the Earth’s surface (Lava),  Extrusive Rocks:  Cools quickly produces many small crystals that are not readily seen by the unaided eye.

7 Photo shows Igneous rock

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10 Photo shows Igneous rock

11 Photo shows Igneous rock

Textures of Igneous rock 12  Fine-grained: cools quickly with little to no crystals (such as Basalt)  Coarse-grained: takes longer to cool, giving mineral crystals more time to grow (such as Granite) Granite Basalt

Sedimentary Rocks  Sedimentary rock is formed by withering and erosion  Sediments are deposited in layers, with the older ones on the bottom  Sediments are moved from one place to another (transported by wind or rivers)  The layers become compacted and cemented together by the effect of pressure and minerals 13

Sedimentary Rock  Clastic: made of fragments of rocks cemented together by water-soluble minerals such as calcium carbonate. Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments (over two millimeters in diameter). The spaces between the large angular fragments can be filled with a matrix of smaller particles or a mineral cement that binds the rock together. Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments (over two millimeters in diameter). The spaces between the large angular fragments can be filled with a matrix of smaller particles or a mineral cement that binds the rock together. 14

Sedimentary Rock  Chemical sedimentary: minerals crystallize out of solution to become rock Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO 3 ) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris. Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO 3 ) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris. 15

Sedimentary Rock  Organic sedimentary: remains of plants and animals Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment. 16

17 Samples of sedimentary rocks SandstoneLimestone

Metamorphic Rock  This can greatly affect the hardness, texture or layer patterns of the rocks.  Metamorphic rocks are formed by the effect of heat and pressure on existing rocks (igneous and sedimentary). Magma metamorphic rock forming here heat Pressure from surface rocks

Metamorphic Rocks  Contact Metamorphism: heated by nearby magma  Increased temperature changes the composition of the rock, minerals are changed into new minerals 19

Metamorphic Rocks  The Metamorphic processes generally improve the engineering behavior of the rocks by increasing their hardness and strength. 20  Some metamorphic rocks are foliated, in which, grains oriented similar to bedding planes in sedimentary rocks. This foliations are important because the shear strength is less for stresses acting parallel to the foliations. Other metamorphic rocks are non-foliated and have no such orientations.

End of Types of Rocks PPT Any question 21