Tunnel Engineering and Rock Mechanics Quiz
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Questions and Answers

What is the primary purpose of rock mechanics in tunnel engineering?

  • To study rock mass behavior under stress (correct)
  • To measure drill core quality
  • To evaluate joint spacing
  • To assess groundwater impact on excavation

Which factor is NOT part of the Q-System formula used for rock quality assessment?

  • Groundwater impact factor (G) (correct)
  • Joint water reduction factor (Jw)
  • Stress Reduction Factor (SRF)
  • Rock Quality Designation (RQD)

What does the term 'joint spacing' refer to in tunnel engineering?

  • The width of the joints in rock
  • The distance between fractures in the rock (correct)
  • The angle at which fractures occur
  • The length of the fractures in the rock

What is the main advantage of using Fiber-Reinforced Shotcrete (FRS) over standard shotcrete?

<p>Reduced cracking and increased flexibility (A)</p> Signup and view all the answers

In the context of tunnel support systems, what is a primary function of rock bolts?

<p>To prevent rock movement by anchoring it (C)</p> Signup and view all the answers

Which support system is typically used for immediate stabilization of tunnel walls?

<p>Shotcrete (C)</p> Signup and view all the answers

What does an Excavation Support Ratio (ESR) indicate about a tunnel project?

<p>The level of support required based on usage (C)</p> Signup and view all the answers

Which of the following factors is NOT influenced by groundwater in tunnel engineering?

<p>Intact rock strength (A)</p> Signup and view all the answers

What is the significance of measuring intact rock strength in tunnel engineering?

<p>It provides resistance measurements for excavation (B)</p> Signup and view all the answers

What common failure mechanism occurs when shotcrete separates from the rock?

<p>Adhesion Failure (D)</p> Signup and view all the answers

What is the role of 'Joint Orientation' in tunnel engineering?

<p>Describes the fracture direction relative to the tunnel. (D)</p> Signup and view all the answers

How does the Excavation Support Ratio (ESR) influence tunnel design?

<p>Reflects the required stability based on tunnel usage. (D)</p> Signup and view all the answers

What does a low Q value indicate regarding rock mass quality?

<p>Poor quality, necessitating robust support systems. (C)</p> Signup and view all the answers

What is the primary function of Cable Bolts in tunnel support systems?

<p>To anchor and stabilize rock at deeper levels. (D)</p> Signup and view all the answers

Which factor does NOT influence the effectiveness of Joint Water Reduction in the Q-System?

<p>Fracture density in drill core samples. (A)</p> Signup and view all the answers

What characterizes Fiber-Reinforced Shotcrete over standard shotcrete?

<p>Reduced cracking and enhanced flexibility. (C)</p> Signup and view all the answers

What does the formula for the Q-System aim to evaluate?

<p>Quality and behavior of rock mass. (B)</p> Signup and view all the answers

What is the main purpose of measuring Joint Persistence in rock mechanics?

<p>To determine the length of fractures. (C)</p> Signup and view all the answers

What is the significance of the Rock Quality Designation (RQD) in rock mass classification?

<p>It indicates the percentage of intact rock in core samples. (A)</p> Signup and view all the answers

What type of failure does shear failure refer to in the context of shotcrete?

<p>The layer slides or shifts under applied pressure. (A)</p> Signup and view all the answers

Which factor primarily affects the stability and excavation process of a tunnel?

<p>Intact Rock Strength (C)</p> Signup and view all the answers

What does the variable 'Jn' in the Q-System formula represent?

<p>Number of Joint Sets (C)</p> Signup and view all the answers

Which method is used for immediate stabilization of tunnel walls?

<p>Shotcrete (B)</p> Signup and view all the answers

What does a higher Excavation Support Ratio (ESR) generally imply for tunnel stability?

<p>Less support needed (A)</p> Signup and view all the answers

Which characteristic of a joint is quantified by the term 'joint aperture'?

<p>Width of the fracture (B)</p> Signup and view all the answers

What is the outcome of a poor quality rock mass, indicated by a low Q value?

<p>Need for enhanced support systems (B)</p> Signup and view all the answers

Which of these materials is reinforced with fibers to improve its properties?

<p>Shotcrete (A)</p> Signup and view all the answers

What does the Q value depend on regarding joint characteristics?

<p>Joint Water Reduction Factor (D)</p> Signup and view all the answers

What is the main purpose of the Rock Quality Designation (RQD) measure?

<p>To determine intact rock percentage (A)</p> Signup and view all the answers

Which failure type is characterized by the layer sliding under pressure in shotcrete?

<p>Shear Failure (C)</p> Signup and view all the answers

What does the variable 'Ja' represent in the Q-System formula?

<p>Joint alteration (B)</p> Signup and view all the answers

Which material is typically used to distribute forces during tunnel support?

<p>Steel mesh (C)</p> Signup and view all the answers

In the context of tunnel engineering, what does a low Excavation Support Ratio (ESR) suggest?

<p>Less stability is required for the tunnel (C)</p> Signup and view all the answers

What does 'RQD' stand for in rock mass classification?

<p>Rock Quality Designation (B)</p> Signup and view all the answers

Which aspect of rock behavior is assessed by studying joint persistence?

<p>Length of fractures within the rock (A)</p> Signup and view all the answers

What factor influences the stability of shotcrete in tunnel construction?

<p>Adhesion failure (D)</p> Signup and view all the answers

Which support system is specifically designed for deeper tunnel applications?

<p>Cable bolts (C)</p> Signup and view all the answers

What is the purpose of measuring groundwater in tunnel engineering?

<p>To evaluate rock stability (A)</p> Signup and view all the answers

Which of the following describes the joint shape in rock mechanics?

<p>Joint contour (B)</p> Signup and view all the answers

What does the term 'stress reduction factor (SRF)' refer to in the Q-System?

<p>Net rock stress divided by excavation impact (C)</p> Signup and view all the answers

Flashcards

Tunnel Engineering

Construction of underground passages for transport, utilities, or mining.

Rock Mechanics

Study of how rock behaves under stress, crucial for tunnel design.

Intact Rock Strength

Lab-measured resistance of solid rock to force.

Field Stresses

Natural stresses in rock before a tunnel is built.

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Groundwater

Water in the ground, affecting tunnel stability during excavation.

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Drill Core Quality

Indicates rock quality by measuring fracture density.

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Rock Quality Designation (RQD)

Percentage of intact rock in core samples, used to evaluate rock quality.

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Q-System

Rock quality assessment system using RQD, joint conditions, etc.

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Joint Spacing

Distance between rock fractures or joints.

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Joint Persistence

Length of rock fractures.

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Excavation Support Ratio (ESR)

Support level for a tunnel based on usage and safety requirements.

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Rock Bolts

Short steel bars anchored into rock for stability.

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Cable Bolts

Longer, flexible steel cables for deep tunnels.

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Shotcrete

Spraying concrete onto tunnel walls for stability.

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Adhesion Failure

Shotcrete separates from the rock.

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Intact Rock Strength

Lab test measuring solid rock's force resistance.

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Field Stresses

Natural rock pressure before tunnel is built.

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Groundwater's Impact

How groundwater affects tunnel stability during construction.

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Drill Core Quality

Fracture density in rock samples; measures rock quality.

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Joint Spacing

Distance between rock fractures.

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Joint Persistence

Length of rock fractures.

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Joint Orientation

Fracture direction in relation to tunnel.

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Q-System

Rock quality assessment, crucial for tunnel plans.

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RQD (Rock Quality Designation)

Intact rock percentage in core samples.

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Rock Bolt Length

Formula (L = 2 + 0.15 * Span) to calculate stable anchor depth required for stability.

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Excavation Support Ratio (ESR)

Support level for tunnels based on usage and safety needs.

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Shotcrete

Spraying concrete onto tunnel walls to improve stability.

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Adhesion Failure

Shotcrete separates from rock during tunneling.

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Shear Failure

Rock layer slides during tunneling.

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Tunnel Engineering

Construction of underground passages for transport, utilities or mining.

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Rock Mechanics

Study of how rock behaves under stress, crucial for safe tunnel design.

Signup and view all the flashcards

Intact Rock Strength

Lab-measured resistance of solid rock to a force.

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Field Stresses

Natural stresses in rock before a tunnel is built.

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Groundwater's Impact

How groundwater affects tunnel stability during excavation.

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Drill Core Quality

Indicates rock quality through fracture density measurements.

Signup and view all the flashcards

RQD (Rock Quality Designation)

Percentage of intact rock in core samples, used to evaluate rock quality.

Signup and view all the flashcards

Q-System

Rock quality assessment system using RQD, joint conditions, and more, aiding tunnel design.

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Joint Spacing

Distance between rock fractures or joints.

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Joint Persistence

Length of rock fractures.

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Support Systems for Tunnels

Methods to improve tunnel stability, including rock bolts, cable bolts, plates, and mesh.

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Rock Bolts

Short steel bars anchored into the rock for stability.

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Shotcrete

Spraying concrete onto tunnel walls for immediate stabilization.

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Excavation Support Ratio (ESR)

Support level for a tunnel based on usage and safety requirements.

Signup and view all the flashcards

Bolt Length Calculation

Formula (L = 2 + 0.15 * Span) to calculate the length of support necessary for stability.

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Adhesion Failure

Shotcrete separates from the rock.

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Shear Failure

Rock layer slides under pressure.

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Intact Rock Strength

Resistance of solid rock to a force, measured in a lab setting.

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Field Stresses

Natural pressures in the rock before a tunnel is built.

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Groundwater's Impact

Effect of water in the ground on tunnel stability during excavation.

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Drill Core Quality

Measures rock quality by assessing fracture density in core samples.

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RQD (Rock Quality Designation)

Percentage of intact rock (no fractures) in extracted core samples.

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Q-System

Rock quality assessment system using RQD, joint conditions, etc. , for tunnel design.

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Joint Spacing

Distance between rock fractures (joints).

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Joint Persistence

Length of rock fractures.

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Excavation Support Ratio (ESR)

Support level needed for a tunnel based on its usage and safety.

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Rock Bolts

Short steel bars anchored into rock for stability.

Signup and view all the flashcards

Shotcrete

Sprayed concrete for immediate tunnel wall stabilization.

Signup and view all the flashcards

Adhesion Failure

Shotcrete separates from the tunnel wall.

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Shear Failure

Rock layer sliding under pressure.

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Bolt Length Calculation

Formula (L = 2 + 0.15 * Span) to determine needed anchorage depth.

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Study Notes

Tunnel Engineering and Rock Mechanics

  • Tunnel engineering focuses on building underground passages for transportation, utilities, or mining.
  • Rock mechanics studies how rocks behave under pressure, essential for safe tunnel design.

Key Data Types

  • Intact Rock Strength: Measured in a lab, it's the resistance a rock piece offers to force.
  • Field Stresses: Pre-existing stresses within the rock before tunnel construction.
  • Groundwater: Affects tunnel stability; it can cause the rock mass to collapse.
  • Drill Core Quality (Fracture Density): Shows how much the rock is fractured; high fractures mean less stable rock.
  • Joint Spacing: Distance between fractures in the rock mass, a critical stability factor.
  • Joint Persistence: Length of a fracture; longer fractures can lead to greater structural weakness.
  • Joint Orientation: Fracture direction relative to the tunnel; alignment affects stability.
  • Joint Contour (Shape): Smooth or rough joint surfaces. Smooth surfaces cause less disruption to the rock mass.
  • Joint Aperture and Surface Condition: Joint width and condition influence the tunnel's stability greatly.

Rock Mass Classification

  • Purpose: To assess the quality and behavior of the rock mass.
  • Applications: Helps determine tunnel project feasibility, the appropriate tunnel support system, and initial estimations of rock strength and deformation.
  • Q-System (Rock Quality Assessment): Formula to rate rock mass quality.

Q-System Formula

  • Q = [RQD / Jn] * [Jr / Ja] * [Jw / SRF]

  • RQD (Rock Quality Designation): Percentage of intact rock in core samples. High RQD indicates better rock conditions.

  • Jn: Number of joint sets; higher numbers signify more problematic joints (more likely to cause failure).

  • Jr: Roughness of the most unfavorable joint; smoother joints mean more stability for the tunneling process.

  • Ja: Joint alteration (weakness or filling); poor alteration values indicate more rock issues.

  • Jw: Joint water reduction factor; presence of water reduces stability.

  • SRF (Stress Reduction Factor): Evaluates the impact of stresses on the rock mass; greater stress means less certainty about the rock's behavior.

Support Systems for Tunnels

  • Reinforcement: Steel bars and cables embedded in the rock to improve stability
    • Rock Bolts: Short steel bars anchored into the rock.
    • Cable Bolts: Longer, flexible steel cables for greater depths.
  • Surface Support: Methods to prevent rock movement along the tunnel walls
    • Plates & Straps: Distribute forces, prevent movement.
    • Mesh: Steel mesh to contain loose rock.
    • Shotcrete: Sprayed concrete for immediate stabilization (a type of surface support).

Excavation Support Ratio (ESR)

  • Definition: Measures support level for a tunnel, based on safety needs.
  • Values: Lower ESR values (e.g., nuclear facilities) require more extensive support to ensure stability. Higher ESR (e.g., temporary mine tunnels) need less support.

Bolt Length and Design

  • Bolt length (L) calculation: L = 2 + 0.15 * Span. This ensures proper anchorage for stability.

Shotcrete and Fiber-Reinforced Shotcrete (FRS)

  • Shotcrete: Spray-applied concrete improving tunnel wall stability.
  • Fiber-Reinforced Shotcrete (FRS): Improves shotcrete's resilience and resistance to cracking.

Failure Mechanisms

  • Adhesion Failure: Shotcrete separates from rock.
  • Shear Failure: Layers of rock slide under pressure.
  • Compression/Tension Failure: (rare, in thin shotcrete).

Applications of Tunnel Engineering

  • Transportation: Rail, road tunnels.
  • Utilities: Water, sewage, power transmission.
  • Mining: Underground ore extraction.

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Description

Test your knowledge on tunnel engineering and rock mechanics through this quiz. Explore critical data types like joint spacing, rock strength, and the effects of groundwater on tunnel stability. Perfect for students and professionals in the field of civil engineering.

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