Civil engineeringLesson 1 of 2 in the course Geotechnical engineering

Soil Shear Strength: Drainage, Stress, and Large-Strain Models

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces soil shear strength, the mechanisms that produce it, and the key factors that influence it. Understanding these ideas helps explain why soils respond differently to loading and why drainage conditions matter in geotechnical design.

Shear strength is the magnitude of shear stress a soil can sustain before it shears or undergoes continuing deformation. Resistance comes primarily from friction and interlocking between particles; cementation or bonding at particle contacts can also contribute.

All flashcards

How are total normal stress, pore-water pressure, and effective normal stress related?
Effective normal stress is total normal stress minus pore-water pressure: σ′=σ−u\sigma' = \sigma - u.
What is undrained shear strength?
Shear strength measured or adopted when pore fluid cannot drain during shearing.
What does the SHANSEP framework relate?
Normalized soil properties to stress history, including the influence of overconsolidation ratio.
What is residual strength?
Resistance that may develop after large displacement, often as particles align along a shear surface.
How does critical state differ from steady state?
Critical state requires continued shearing at constant volume; steady state additionally requires constant stresses, velocity, and statistically steady particle structure.

Quiz questions

  1. In the Tresca idealization for undrained shearing, how are principal stresses related to undrained strength?Answer: σ1−σ3=2Su\sigma_1 - \sigma_3 = 2S_u
  2. For many clays, what does the SHANSEP approach use to compare undrained strength across stress histories?Answer: The ratio of undrained strength to consolidation stress, considered with OCR.
  3. Which equation gives the drained Mohr–Coulomb approximation for shear strength?Answer: τ=σ′tan⁡(ϕ′)+c′\tau = \sigma'\tan(\phi') + c'
  4. In a linear Mohr–Coulomb fit, how should the effective-stress cohesion intercept c′c' generally be interpreted?Answer: As a fitted intercept that can depend on the stress range.
  5. Which set of conditions defines steady state in soil shearing?Answer: Constant volume, normal effective stress, shear stress, and deformation velocity, with steady particle arrangement.

Based on the Wikipedia article Shear strength (soil), licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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