Geology: Rocks and Soil Overview

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Questions and Answers

Which types of rock are most commonly found in gravel?

Granite, marble, and schist

Shale, gneiss, and obsidian

Basalt, limestone, and sandstone (correct)

Claystone, quartzite, and slate

What process leads to the formation of sand?

Sedimentation of organic material

Subduction of tectonic plates

Melting of igneous rock under high pressure

Weathering and erosion of rocks over time (correct)

What characterizes igneous rocks?

Formed from the compaction of sediments

Formed from the cooling and solidification of molten rock (correct)

Primarily composed of minerals transported by wind

Formed from the chemical alteration of existing rocks

Which term describes igneous rocks that form from magma below the Earth's surface?

Intrusive igneous rocks Signup and view all the answers

Which type of rock is characterized as being formed from lava erupted from a volcano?

Extrusive igneous rocks Signup and view all the answers

Which of the following examples is NOT an extrusive igneous rock?

Granite Signup and view all the answers

What is the primary environmental concern related to e-waste in landfills?

It contains toxic chemicals and heavy metals Signup and view all the answers

Valorizing e-waste can particularly help which industry by reducing its carbon footprint?

Construction industry Signup and view all the answers

What effect does an increased number of cracks in rocks have on mineral weathering?

It allows agents like water and oxygen to interact more intensely with minerals. Signup and view all the answers

Which type of soil is considered the poorest for growing plants due to low nutrients and poor water holding capacity?

Sandy Soil Signup and view all the answers

What is a characteristic of silt soil?

It retains water better than sandy soil. Signup and view all the answers

Which soil type has the smallest particles and exhibits high water storage qualities?

Clay Soil Signup and view all the answers

What is loamy soil primarily known for?

Being a mixture of sand, silt, and clay with good nutrient retention. Signup and view all the answers

What makes sandy soil suitable for drainage?

Large airspaces between particles. Signup and view all the answers

Which of the following statements about clay soil is true?

It is sticky to the touch when wet. Signup and view all the answers

What is a defining feature of loamy soil compared to other soil types?

Incorporating properties of sand, silt, and clay. Signup and view all the answers

What principle governs the operation of a device that displaces its own weight within a liquid?

Archimedes' principle Signup and view all the answers

Which test is primarily conducted to determine the rate and magnitude of soil consolidation?

Consolidation Test Signup and view all the answers

What does the nuclear density gauge primarily measure?

Wet density, dry density, and moisture content Signup and view all the answers

Which method is not used to determine the density of compacted soils?

Vane Shear Test Signup and view all the answers

What is the purpose of the Proctor Tests?

To determine maximum dry density and optimum moisture content Signup and view all the answers

Which soil type is most suitable for the Sand Cone Test?

Granular soils Signup and view all the answers

For which soil condition is the Rubber Balloon Test generally unsuitable?

Very soft soils Signup and view all the answers

What main factors govern the rate of soil consolidation?

Hydraulic conductivity and compressibility Signup and view all the answers

What is the primary purpose of retaining walls?

To resist lateral pressure of soil due to elevation changes Signup and view all the answers

Which of the following activities are likely to contribute to landslides?

Construction on steep slopes Signup and view all the answers

How does soil nailing assist in preventing landslides?

By inserting reinforcement bars into the failure zone Signup and view all the answers

What is the function of drainage systems in landslide prevention?

To control water infiltration and reduce pore pressure Signup and view all the answers

Which geological factor significantly increases the risk of landslides?

Wet soil structures Signup and view all the answers

What role do geotextiles play in soil stabilization?

They facilitate improved water drainage and soil separation Signup and view all the answers

Which of the following is NOT a method used to prevent soil erosion or landslides?

Building earth mounds Signup and view all the answers

What type of concrete is used to stabilize slopes and prevent soil erosion?

Shotcrete Signup and view all the answers

What does the triaxial test primarily assess in soil samples?

Shear strength and deformation behavior under stress Signup and view all the answers

What is the primary purpose of the direct shear test?

To measure soil's shear strength at a specific angle Signup and view all the answers

Why is ground bearing pressure crucial in soil testing?

To evaluate the soil's ability to support loads Signup and view all the answers

What information can be obtained from sieve analysis?

Distribution of aggregate particle sizes Signup and view all the answers

The Unified Soil Classification System (USCS) is used for what purpose?

To classify soil based on texture and grain size Signup and view all the answers

Atterberg limits are significant for geotechnical engineers because they help in what?

Designing foundations and predicting soil behavior Signup and view all the answers

What method is used to determine moisture content in the oven drying method?

Weighing the sample before and after drying Signup and view all the answers

The hydrometer test is most suitable for which type of soil?

Fine-grained soils like clay and silt Signup and view all the answers

Study Notes

Rocks

Basalt, limestone, and sandstone are common gravel types.
Rock is a solid aggregate of mineral materials, often consisting of a blend of compacted minerals held by a cement-like mineral matrix.
Rocks are relatively hard, naturally occurring.

Igneous Rocks

Igneous rocks, formed from cooled molten rock, are called "fire-born" as they originate from magma deep within the Earth.
Igneous rocks are classified as intrusive (formed underground) or extrusive (formed from volcanic eruptions).
Intrusive Igneous rock (Plutonic Rocks) solidify inside the Earth's crust.
Extrusive Igneous rock (Volcanic Rocks) solidify on the Earth's surface.
Examples of Extrusive Rocks: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff.
Weathering factors include increased surface area, water and oxygen interaction, and mineral composition.

Soil

Soil is the upper layer of earth where plants grow, comprising organic remains, clay, and rock particles.
Sandy Soil: small weathered rock particles, poor in nutrients, excellent for drainage (formed from granite, limestone, and quartz breakdown).
Silt Soil: smoother and finer than sand, better water retention, found near water bodies.
Clay Soil: smallest particles, tightly packed, excellent water storage but poor drainage, sticky when wet, smooth when dry.
Loamy Soil: a mix of sand, silt, and clay, an optimal balance for farming due to moisture and nutrient retention.

Soil Testing

Geotechnical engineers determine soil properties by using a variety of tests.
Triaxial Test: measures shear strength and deformation under varying pressure.
Direct Shear Test: measures shear strength at specific angles to gauge resistance to sliding.
Mechanical Sieve Analysis: determines the soil's particle size distribution by shaking the sample through a series of sieves.
Atterberg Limits: classify the properties of silt and clay soils at different moisture contents.
Moisture Content Test (Oven Drying Method): determines moisture by weighing a sample before and after drying.
Hydrometer Test: measures the particle size distribution of fine-grained soils using an instrument that determines specific gravity.
Consolidation Test: measures the rate and magnitude of soil consolidation under axial loading, crucial for predicting settlement characteristics of clay layers.

Soil Compaction

Soil Compaction Site Testing measures dry and wet density, and moisture content of the material being tested.
Nuclear Density Test: uses gamma radiation to measure density and moisture content.
- Proctor Tests: determine maximum dry density and optimal moisture content in a laboratory setting.
- Sand Cone Test: measures in-situ dry soil density, especially suited for granular soils.
- Rubber Balloon Test: determines field density of compacted, especially well-compacted soils.

Soil Erosion and Landslides

Factors contributing to landslides:
- Heavy Rainfall: unstable soil and poor drainage
- Geological Factors: steep slopes, unstable rock formations, and weak soil structures
- Human Activities: construction, mining, deforestation weaken soil structure
- Earthquakes: ground shaking destabilizes slopes

Structures to Prevent Soil Erosion and Landslides

Retaining Walls: Resist soil pressure and prevent erosion on slopes.
Soil Nailing or Rock Bolts: Reinforcements embedded in the soil or rock to prevent slope failure.
Ground Anchor or Earth Anchor: Strand wire anchors used to retain shoring structures.
Sheet Piling: Interlocking vertical panels forming a barrier to resist soil and water pressures.
Shotcrete: Sprayed concrete for slope stabilization and erosion prevention.
Drainage Systems: Control water infiltration and reduce pressure on slopes.

Geotextile

A permeable textile material used in foundations, soil, rock, and earth to increase stability and reduce wind and water erosion.
Functions of Geotextile:
- Filtration
- Separation
- Drainage
- Reinforcement
- Sealing and Protection

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Description

This quiz covers the fundamentals of rocks and soil, including classifications of igneous rocks and various gravel types. Learn about the characteristics of rocks as aggregates of minerals and the processes that shape them. Test your knowledge on the formation, types, and significance of soil in our ecosystem.