Soil Mechanics and Formation Quiz

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Questions and Answers

Which engineering discipline focuses specifically on the study of physical properties and behaviors of soil?

Foundation Engineering

Geotechnical Engineering

Soils Engineering (correct)

Environmental Engineering

What is the primary cause of soil formation?

Sedimentation of organic matter

Chemical weathering of minerals

Physical and chemical weathering of rocks (correct)

Vegetative decomposition

Who is recognized as the 'Father of Soil Mechanics'?

Robert Hooke

Henri Darcy

Karl Terzaghi (correct)

James Keeble

What defines soil according to geologists?

A natural aggregate of mineral grains found in a specific geological layer Signup and view all the answers

Which of the following best describes soil mechanics?

The study of the behavior of soil masses under various forces Signup and view all the answers

Which option is not part of the soil-bearing capacity problems addressed prior to the 18th century?

Burj Khalifa Signup and view all the answers

Which of the following is considered a main agent of physical weathering?

Freezing and thawing Signup and view all the answers

What role does Geotechnical Engineering play in civil engineering?

Application of soil and rock mechanics in designing foundations and earth structures Signup and view all the answers

Which type of soil is formed by the deposition in quiet lakes?

Lacustrine soils Signup and view all the answers

What term describes soils that contain decayed organic matter?

Organic soils Signup and view all the answers

What defines a soil as coarse grained?

Its individual particles are visible to the unaided eye Signup and view all the answers

What is primarily responsible for the chemical alteration of rocks during weathering?

Hydration and oxidation Signup and view all the answers

Which of the following is a characteristic of fine grained soils?

Particles are not visible to the unaided eye Signup and view all the answers

What is defined as the process of changing the composition and texture of rocks without melting?

Metamorphism Signup and view all the answers

Which type of soil stays at its site of formation?

Residual soils Signup and view all the answers

How are sedimentary rocks primarily formed?

From weathering and subsequent compaction of soil deposits Signup and view all the answers

What is classified as gravel in soil terms?

Particles larger than 2 mm Signup and view all the answers

What does the dry strength test for fine grained soils measure?

Resistance to breaking when dry Signup and view all the answers

What distinguishes transported soils from residual soils?

Transported soils are moved by natural forces to different locations Signup and view all the answers

Which of the following processes is characteristic of mechanical weathering?

Physical disintegration due to temperature changes Signup and view all the answers

What is the term for the movement of soil due to gravity, such as in landslides?

Colluvial movement Signup and view all the answers

What type of rock undergoes considerable change in constitution and structure through metamorphism?

Either igneous or sedimentary rocks Signup and view all the answers

What is NOT a major agent responsible for chemical weathering?

Erosion Signup and view all the answers

Which of the following describes the process of weathering?

The chemical decomposition and mechanical disintegration of rocks Signup and view all the answers

What property of soil measures its ability to let water pass through?

Permeability Signup and view all the answers

Which property helps in computing the settlement of structures?

Consolidation and compressibility Signup and view all the answers

Which soil type is characterized by the presence of finely divided organic particles?

Organic clay Signup and view all the answers

What type of soil consists of equidimensional grains of quartz and is known as rock flour?

Silt Signup and view all the answers

What is the primary characteristic of bentonite clay?

High percentage of clay mineral Signup and view all the answers

Which property of soil relates to its ability to withstand stresses without failing?

Shear strength Signup and view all the answers

What distinguishes organic silt from regular silt?

Higher plasticity Signup and view all the answers

Which type of soil is typically described as coarse and can settle significantly in a short time?

Sand Signup and view all the answers

What characteristic is unique to black cotton soils?

High compressibility and shrinkage Signup and view all the answers

What is peat primarily composed of?

Fibrous particles of decayed vegetable matter Signup and view all the answers

Which soil is identified by its alternating layers of silt and clay?

Varved clay Signup and view all the answers

Which of the following describes hard pan?

Stratum of hard, cohesive soil Signup and view all the answers

What is glacial till primarily composed of?

Coarse particles and heterogeneous mixtures Signup and view all the answers

What is a defining characteristic of expansive soils?

Significant volume changes from wetting and drying cycles Signup and view all the answers

What do calcareous soils contain that makes them reactive?

Calcium carbonate Signup and view all the answers

Which soil type is a cemented mixture primarily comprised of calcium carbonate?

Caliche Signup and view all the answers

Study Notes

Soil Mechanics introduction

The Leaning Tower of Pisa is an example of a structure that had problems related to soil-bearing capacity.
Soil is a mixture of mineral grains, decayed organic matter, liquid and gas.
Soil Mechanics studies the physical properties of soil and how soil masses behave under different forces.
Soils Engineering applies the principles of Soil Mechanics to practical problems.
Geotechnical Engineering, a subdiscipline of Civil Engineering, deals with natural materials near the Earth's surface.
Foundation Engineering focuses on designing, constructing, and maintaining foundations for buildings and engineering structures.
Karl Terzaghi is considered the "Father of Soil Mechanics".

Rock Cycle and Soil Formation

Soil is formed from the weathering of rocks.
Physical weathering breaks down rocks without changing their composition, through processes like exfoliation, unloading, erosion, freezing, thawing.
Chemical weathering causes both size reduction and chemical alteration of rocks through processes like hydration, carbonation, oxidation.
Soils classified as residual soils are formed in place, while transported soils are moved to new locations.
Civil Engineers are mainly concerned with the top 10-15 meters of soil for most projects.
Soils are derived from igneous, sedimentary, or metamorphic rocks.
Rock weathering is influenced by climatic and surrounding conditions.
Soil particles range from large boulders to tiny clay mineral crystals.
Residual soils form when weathered rock particles remain at their origin; transported soils result from movement by gravity, water, wind, or ice.

Rock Types

Igneous rocks form from the solidification of magma from the Earth's mantle.
Sedimentary rocks form by the compaction and cementation of deposits like gravel, sand, silt, and clay.
Metamorphic rocks are igneous or sedimentary rocks transformed by heat, pressure, and chemical fluids.

Weathering

Weathering is the breakdown of rocks through mechanical and chemical processes.
Mechanical weathering results from rock expansion and contraction due to heat changes.
Chemical weathering alters original rock minerals through chemical reactions.

Weathering Products (Residual Soils)

Glacial soils are transported and deposited by glaciers.
Alluvial or Fluvial soils are transported by running water and deposited along streams.
Lacustrine soils are deposited in quiet lakes.
Marine soils are deposited in seas.
Aeolian soils are transported and deposited by wind.
Colluvial soils form from soil movement by gravity, like during landslides.

Metamorphism

Metamorphism changes the composition and texture of rocks without melting them.

Soil Analysis and Properties

Mechanical analysis determines the size range of particles in a soil.
Soil consists of solid particles, liquid (soil water), and gaseous (air) components.
Solid soil components can be mineral, organic, or both.

Soil Classification

Coarse-grained soils have visible individual particles.
Fine-grained soils have particles not visible to the naked eye.
Organic soils contain decayed animal or plant matter.
Gravel has particles larger than 2 mm.
Clay is made up of particles smaller than 0.005 mm.
Colloids are clay particles smaller than 0.001 mm.

Identifying Fine-Grained Soils (Field Tests)

Dry strength: tests the soil's ability to hold form after drying.
Plasticity: assesses the moldability and ability to form threads without breaking.
Water mobility: observes how quickly water drains from a soil paste.
Dispersion: separates particles by size based on settling rates in water.

Significant Soil Properties

Permeability: measures the ability of soil to allow water flow.
Consolidation and compressibility: measure changes in soil volume under load.
Shear strength: determines the soil's ability to withstand stress without failure.

Additional Soil Properties

Atterberg Limits, moisture content, void ratio, relative density, grain size, and sensitivity are also important.
Base Exchange: a property of some clay minerals to bind exchangeable bases.

Types of Soils

Cohesive Soils: Sand and gravel; can be angular, rounded, or well-rounded, usually composed of unaltered mineral grains.
Silt: Fine-grained soil with little to no plasticity.
Plastic Silt: Contains a significant percentage of flat, taped particles.
Organic Silt: Contains decayed vegetable matter and may be plastic.
Clay: Composed of microscopic and sub-microscopic weathered rock particles.
Organic Clay: Contains finely divided organic matter and is highly compressible when saturated.
Bentonite: Clay with a high percentage of clay minerals, often formed from altered volcanic ash.
Black Cotton Soils: Inorganic and exhibit high compressibility, shrinkage, and swelling under load (dark gray or black color).
Peat: Composed of decayed vegetable matter, highly compressible and unsuitable for foundations.
Varved Clay: Lacustrine deposit with alternating layers of silt and clay, formed seasonally.
Hard Pan: A hard, cohesive soil layer resisting penetration by drilling tools.
Glacial Till: Heterogeneous mixture of soil and rock particles deposited by glaciers.
Boulder Soils: Mixture of boulders and a soil matrix, with properties affected by the amount of matrix.
Calcareous Soil: Contains calcium carbonate and effervesces when treated with acid.
Caliche: Gravel, sand, and clay cemented together by calcium carbonate.
Expansive Soils: Clays that undergo significant volume changes with wetting and drying.
Glacial Clays: Soils deposited in ancient lakes and subsequently frozen, forming stratified layers of silt and clay (varved clay).
Gypsum: Calcium sulfate formed in ocean brine under heat and pressure.
Laterite Soils: Residual soils cemented with iron oxides, found in tropical regions.

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Description

Explore the fundamentals of Soil Mechanics and the Rock Cycle with this quiz. Test your knowledge on how soil forms from rocks, the principles of soil behavior, and the application of geotechnical engineering. Perfect for students interested in civil engineering and environmental science.