Geotechnical Fundamentals: Soil and Rock

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Questions and Answers

What are the differences between igneous, sedimentary, and metamorphic rock?

Igneous rocks are formed by the solidification of molten materials, either by intrusion at depths within the earth crust or by extrusion at the earth’s surface.
Sedimentary rocks are formed by the deposition, alteration and/or compression, and lithification of weathered rock debris, chemical precipitates, or organic sediments.
Metamorphic rocks are formed from the re-crystallization of igneous, sedimentary, or other metamorphic rocks through pressure increase, temperature rise, or chemical alteration.
All of the above. (correct)

Why are there different soil types?

Soil types vary due to differences in parent material, climate, organisms, topography, and time.

What affects the properties of soil?

The properties of soil are affected by factors such as particle size, mineral composition, organic matter content, water content, and density.

What are the two main weathering processes?

Both Physical and Chemical Weathering (A) Signup and view all the answers

What is the difference between transported and residual soil?

Residual soil is formed by the weathering of the bedrock, while transported soil is formed by the movement of soil material from one location to another. (A) Signup and view all the answers

What are the main transportation agents of soil?

Water, wind, glaciers, and gravity are the primary transportation agents of soil. Signup and view all the answers

What does the subsurface environment look like?

The subsurface environment can be viewed as a series of layers or horizons, each with distinct characteristics, which are influenced by soil formation processes. Signup and view all the answers

What are the physical properties of soil?

Physical properties of soil include particle size distribution, density, porosity, permeability, and shear strength. Signup and view all the answers

How are physical properties calculated?

Physical properties of soil can be calculated using laboratory tests and field measurements. Signup and view all the answers

Describe the following environments: Aeolian, lacustrine, marine, alluvial, and glacial.

Aeolian environments are characterized by wind deposition, lacustrine environments are associated with lakes, marine environments are influenced by ocean processes, alluvial environments are formed by rivers, and glacial environments are shaped by glaciers. Signup and view all the answers

Name the three main classes of rock and describe how they were formed.

The three main classes of rock are igneous, sedimentary, and metamorphic. Igneous rocks are formed from the cooling and solidification of molten magma. Sedimentary rocks are formed by the accumulation and lithification of sediments. Metamorphic rocks are formed when existing rocks are transformed by heat, pressure, or chemical reactions. Signup and view all the answers

Provide comments on the hardness, soundness, and durability associated with the three main types of rock.

Igneous rocks are generally the hardest and most durable, while sedimentary rocks are typically less hard and more susceptible to weathering. Metamorphic rocks can vary in hardness and durability depending on the type of rock they were formed from and the degree of transformation they have undergone. Signup and view all the answers

Describe the two processes that transform soil sediments into sedimentary rock.

The two main processes involved in the formation of sedimentary rock are compaction and cementation. Compaction occurs when the weight of overlying sediments presses the sediments together, reducing pore space and increasing density. Cementation occurs when minerals dissolved in groundwater precipitate between the sediment grains, binding them together and forming a solid rock. Signup and view all the answers

What types of processes occur to cause metamorphosis of rocks?

Metamorphism occurs when existing rocks, either igneous, sedimentary, or metamorphic, are subjected to conditions of intense heat, pressure, or chemical reactions. These conditions alter the mineral composition, texture, and structure of the rocks, creating new metamorphic rocks. Signup and view all the answers

Why are sand and gravel deposits found along old river and stream locations?

Sand and gravel deposits, often called alluvial deposits, are found along old river and stream locations because they have been transported and deposited by the flowing water. As the water flows, it carries sediment downstream, and when the water slows down, it deposits the sediment, forming sand and gravel bars. Signup and view all the answers

Describe the main types of weathering and give two examples of each.

The main types of weathering are physical weathering and chemical weathering. Physical weathering involves the mechanical breakdown of rock without any change in its chemical composition. Examples of physical weathering include frost wedging and abrasion. Chemical weathering involves the breakdown of rock through chemical reactions. Examples of chemical weathering include oxidation and hydrolysis. Signup and view all the answers

What are loess soils, and what is the potential danger associated with loess?

Loess soils are wind-deposited silt deposits, often found in areas where there have been glaciers. Loess soils are typically very porous and have a high permeability. However, when they become saturated with water, their strength decreases significantly, making them prone to landslides and erosion. Signup and view all the answers

In a glacially effected area, what types of glacial formations represent possible sources of sand and gravel for the construction industry?

Glacial formations that can provide sources of sand and gravel for the construction industry include moraines, eskers, and outwash plains. Moraines are accumulations of rock debris deposited by glaciers. Eskers are long, sinuous ridges of sand and gravel deposited by meltwater streams flowing beneath glaciers. Outwash plains are areas where sand and gravel have been deposited by meltwater streams flowing away from glaciers. Signup and view all the answers

What is the potential danger to stability in areas where the land is formed from marine clay?

Marine clay is often very soft and compressible, and it can be prone to settlement and liquefaction under load. This can pose a significant risk to the stability of buildings and other structures built on these soils. Signup and view all the answers

The mass of a saturated soil sample is 530 gm. The dry mass after oven-drying is 410g. Determine the a) water content b) void ratio c) saturated unit weight d) porosity.

Water Content = 28.5%. Void Ratio = 0.413. Saturated Unit Weight = 1.667 kN/m³. Porosity = 29.4%. (A), Water Content = 28.5%. Void Ratio = 0.413. Saturated Unit Weight = 1.667 kN/m³. Porosity = 29.4%. (B) Signup and view all the answers

A soil sample has a bulk unit weight of 20.0 kN / m³ at a water content of 12%. Determine the a) void ratio b) dry unit weight c) degree of saturation.

Void Ratio = 0.74. Dry Unit Weight = 17.9 kN/m³. Degree of Saturation = 86.7%. (A), Void Ratio = 0.74. Dry Unit Weight = 17.9 kN/m³. Degree of Saturation = 86.7%. (B) Signup and view all the answers

A wet soil sample has a volume of 500cm³ and has a mass of 950 gm. After oven drying, the mass is 900 g is 2.55. Determine the a) water content b) void ratio c) degree of saturation d) porosity.

Water Content = 5.56%. Void Ratio = 0.667. Degree of Saturation = 75.5%. Porosity = 40%. (A), Water Content = 5.56%. Void Ratio = 0.667. Degree of Saturation = 75.5%. Porosity = 40%. (B) Signup and view all the answers

Flashcards

Lithification

The process of converting sediments into sedimentary rock. It usually involves compaction and/or cementation.

What are Igneous Rocks?

Igneous rocks are formed by the solidification of molten materials either by intrusion at depths within the earth crust or by extrusion at the earth's surface.

What are Sedimentary Rocks?

Sedimentary rocks are formed by the lithification of sedimentary soils.

What are Metamorphic Rocks?

Metamorphic rocks were originally igneous, sedimentary, or metamorphic rocks altered physically, chemically, or mineralogically by the application of intense heat and/or pressure and plastic flow at some time in their geological history.