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Arabian Journal of Geosciences

, Volume 4, Issue 7–8, pp 1095–1101 | Cite as

Evaluation of shear strength of cohesionless soil due to excess pore water pressure

  • Awad A. Al-KarniEmail author
Original Paper

Abstract

The shear strength of cohesionless soil is reduced as the water pressure inside the pores of the soil mass increases. The mathematical relationship between the shear strength and the pore water pressure was derived using Mohr–Coulomb failure criteria as a function of the confining pressure and the effective angle of friction. Experimentally, a series of consolidated drained triaxial tests with back pore water pressure was run on samples of saturated uniform dense sand. The tests were conducted at different confining pressures in the range of 100–400 kPa with an increment of 100 kPa. At each level of confining pressure, the tests were repeated at different values of back pore water pressure in the range of 0–100 kPa with an increment of 25 kPa. For each test, the initial applied back pore water pressure was kept constant during the test for comparing the results at the same effective confining pressure. This study concludes that the mathematical relationship gives accurate results at any level of confining pressure and/or pore water pressure as a function of the effective angle of friction that can be evaluated using single consolidated drained triaxial test at zero back pore water pressure.

Keywords

Shear strength Confining pressure Water pressure Cohesionless soil 

Nomenclature

c

Soil cohesion

e

Void ratio

Gs

Specific gravity

u

Pore water pressure

ϕ

Angle of internal friction at zero pore water pressure

\( \phi \prime \)

Effective angle of internal friction

ϕt

Total angle of internal friction

γd

Dry unit weight

σ1

Major principle stresses

\( \sigma_1^\prime \)

Effective major principal stress

σ3

Minor principle stresses

\( \sigma_3^\prime \)

Effective minor principal stress

σc

Consolidation pressure

σd

Deviator vertical stress

σd(max)

Maximum deviator stress

σn

Total normal stress

\( \sigma_{\rm{n}}^\prime \)

Effective normal stress

Δσn

Reduction in normal stress

τ

Shear strength

تقويم مقاومة القص للتربة غير المتماسكة نتيجة زيادة ضغط الماء المسامي

Abstract

تتناقص قيمة مقاومة القص للتربة غير المتماسكة نتيجة زيادة ضغط الماء داخل المسامات في كتلة التربة. وتم اشتقاق العلاقة الرياضية بين قوة القص وضغط الماء المسامي باستخدام معايير الانهيار لموروكولمب (Mohr–Coulomb) كدالة في ضغط الحصر وزاوية الاحتكاك الفعالة. أما تجريبياً, فقد تم إجراء سلسلة من التجارب ثلاثية المحاور المصرفة والمدمجة تحت تأثير ضغط ماء مسامي خلفي على عينات من الرمل الكثيف والمشبع. وأجريت التجارب عند ضغط حصر يتراوح من 100 كيلو باسكال الى 400 كيلو باسكال عند زيادة 100 كيلو باسكال لكل تجربة. وعند كل ضغط حصر محدد، تم تكرار التجربة عند ضغوط ماء مسامي تتراوح من صفر كيلو باسكال الى 100 كيلو باسكال بزيادة قدرها 25 كيلو باسكال لكل تجربة. وقد تم تثبيت ضغط الماء المسامي خلال كل تجربة عند القيمة الأولية له لضمان مقارنة النتائج عند نفس قيمة ضغط الحصر الفعال. ومن هذه الدراسة تبين دقة العلاقة الرياضية في حساب مقاومة القص عند أي مستوى لضغط الحصر و/أو ضغط الماء المسامي كدالة في زاوية الاحتكاك الفعالة التي يمكن تقويمها من إجراء تجربة واحدة ثلاثية المحاور مصرفة ومدمجة عند ضغط ماء مسامي يساوي للصفر.

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Copyright information

© Saudi Society for Geosciences 2009

Authors and Affiliations

  1. 1.Civil Engineering Department, College of EngineeringKing Saud UniversityRiyadhSaudi Arabia

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