THEHONGKONGDEPARTMENTOFCIVILANDENVIRONMENTALENGINEERINGPOLYTECHNICUNIVERSITY土木及崋境工程系香港理工大學Consolidationof soils(1-D, 2-D and 3-D)Prof. Jian-Hua YINRm ZS909, Tel: 2766 6065, Email: cejhyin@polyu.edu.hkHomepage:http://www.zn903.com/cejhyin/Dr.Wen-BoCHENRmZS969,Tel:34008075,Email:wenbochen@polyu.edu.hk
Consolidation of soils (1-D, 2-D and 3-D) Prof. Jian-Hua YIN Rm ZS909, Tel: 2766 6065, Email: cejhyin@polyu.edu.hk Homepage: http://www.zn903.com/cejhyin/ Dr. Wen-Bo CHEN Rm ZS969, Tel: 3400 8075, Email: wenbochen@polyu.edu.hk
THEHONGKONGDEPARTMENTOFCIVILANDENVIRONMENTALENGINEERINGPOLYTECHNICUNIVERSITY土木及璨境工程季系香港理工大學>EssentialReferencesLecture notesCraig,R.F.(2004). Soil Mechanics, 7th edition, Spon Press,Londonand New York (ISBN 04-415-32702-2) (or more updatedversion).Das, Braja M.(2007).Principles of Foundation Engineering (6thedition),Thomson,UnitedStates(ISBN0-534-40752-8)(ormoreupdated version).2
➢ Essential References • Lecture notes • Craig, R.F. (2004). Soil Mechanics, 7th edition, Spon Press, London and New York (ISBN 04-415-32702-2) (or more updated version). • Das, Braja M. (2007). Principles of Foundation Engineering (6th edition), Thomson, United States (ISBN 0-534-40752-8) (or more updated version). 2
THEHONGKONGDEPARTMENTOFCIVILANDENVIRONMENTALENGINEERINGPOLYTECHNICUNIVERSITY土木及璟境工程学系香港理工大學>Learningoutcomes ofthis lectureUnderstandthederivationprocess of Terzaghi'stheoryofonedimensional consolidation and its 8 assumptions;Understand the meaning of coefficient of consolidation, cy, andwhat soil properties it includes;Masterthecalculationmethodforconsolidationsettlementofsoilswithout or with vertical drains;Understandthemechanismof soilcreep,andmasterthesimplifiedmethod for calculation of consolidation settlement of clayey soilswith creep.3
➢ Learning outcomes of this lecture • Understand the derivation process of Terzaghi’s theory of onedimensional consolidation and its 8 assumptions; • Understand the meaning of coefficient of consolidation, cv , and what soil properties it includes; • Master the calculation method for consolidation settlement of soils without or with vertical drains; • Understand the mechanism of soil creep, and master the simplified method for calculation of consolidation settlement of clayey soils with creep. 3
Reviewof SoilMechanicsI.Terzaghi'stheoryofone-dimensional consolidationReviewonconsolidationprocessforsaturatedsoilsChange in total stress (Ao) generates excess pore pressure, ue, because soilis undrained under initial loading.Overtime waterflows outof soil inresponseto change intotal stressAs water flows out, soil undergoesa.a decrease in magnitude ofub.anincreasein o'asu.decreases(principle ofeffective stress:'=g-ue)adecreaseinvolumegeneratingsettlement,sC.Rate of consolidation will depend ona.soilproperties:compressibility&hydraulicconductivityb.distributionofinitialexcessporepressure,ueC.drainageboundaryconditionsAs soil consolidates, ue +, o'↑, and S ↑4
4 Review on consolidation process for saturated soils • Change in total stress (Δσ) generates excess pore pressure, ue , because soil is undrained under initial loading • Over time water flows out of soil in response to change in total stress • As water flows out, soil undergoes a. a decrease in magnitude of ue b. an increase in σ’ as ue decreases (principle of effective stress: σ’ = σ- ue ) c. a decrease in volume generating settlement, S • Rate of consolidation will depend on a. soil properties: compressibility & hydraulic conductivity b. distribution of initial excess pore pressure, ue c. drainage boundary conditions • As soil consolidates, ue ↓, σ’ ↑, and S ↑ Review of Soil Mechanics I. Terzaghi’s theory of one-dimensional consolidation
ReviewofSoilMechanicsI.Terzaghi's theory of one-dimensional consolidationReview on consolidation process forsaturated soilssurchargegroundAo0.ut5
5 Review on consolidation process for saturated soils t t t t Δσz σz u σ’z surcharge ground Review of Soil Mechanics I. Terzaghi’s theory of one-dimensional consolidation