Part-VI-Consolidation

Part-VI-Consolidation - PART VI -A CONSOLIDATION: 1D...

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Prof. M. Santagata CE 383 SLIDE 1 PART VI -A CONSOLIDATION: 1D COMPRESSION BEHAVIOR OF SOILS AND FINAL SETTLEMENT CALCULATION ± INTRODUCTION ± 1D CONSOLIDATION TEST ± COMPRESSION CURVE (e – log σ v ) ± PRECONSOLIDATION STRESS ( σ p ) ± NC AND OC CLAYS ± COMPRESSIBILITY PARAMETERS ± CALCULATION OF FINAL CONSOLIDATION SETTLEMENT Prof. M. Santagata CE 383 SLIDE 2 ± INTRODUCTION CONSOLIDATION Settlement = IMMEDIATE+ PRIMARY CONSOLIDATION + SECONDARY SANDS Elastic Deformation Creep CLAYS STRESS INCREASE CAUSED BY APPLICATION OF LOADS COMPRESSION OF SOIL LAYERS Generated by deformation of soil particles, relocation of soil particles, expulsion of water Time dependent Volume change due to expulsion of water
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Prof. M. Santagata CE 383 SLIDE 3 ± HYDROMECHANICAL ANALOGY TIME APPLIED FORCE Time Force In spring In water INTRO Prof. M. Santagata CE 383 SLIDE 4 q u 0 We have learned ± Soil is a multiphase material: solid phase + liquid phase (if S=1) ± Load applied to a soil mass is SHARED in part by mineral grains and in part by pore fluid FOCUS ON SATURATED SOILS Effective stress principle: σ = σ ’+u (For S=1) ± Hydraulic conductivity cohesive soils << sands Soil layer subjected to stress increase u 0 + u u 0 u 0 u 0 Excess pore pressures ( u) are generated by applied load (magnitude is a function of location) Pore water drainage towards zone where u = u 0 to dissipate u SANDS & GRAVELS: high k Æ Dissipation instantaneous Immediate & consolidation settlement occur simultaneously CLAYS: low k Æ consolidation = long process (years) resulting settlement significantly greater than immediate settlement CONSOLIDATION SETTLEMENT
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Prof. M. Santagata CE 383 SLIDE 5 INTRO ± HYDROMECHANICAL ANALOGY Represents resistance to the flow of water Represents resistance to compression of the mineral skeleton TIME APPLIED FORCE Time Force In spring In water Prof. M. Santagata CE 383 SLIDE 6 q q SAND SAND CLAY H AT TIME 0 ∆σ v u ∆σ v ∆σ v u ∆σ v AT TIME SAND SAND CLAY H t q = 0 = 0 AT TIME t ∆σ v u ∆σ v INTRODUCTION SAND SAND CLAY H q No ∆σ v No settlement S~0 Increasing S as ∆σ v increases AT ANY POINT PORE PRESSURE AND EFFECTIVE STRESS CHANGE IN TIME
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Prof. M. Santagata CE 383 SLIDE 7 INTRODUCTION ± AT ANY POINT AND ANY TIME σ v = σ v + u ( ∆σ v = ∆σ v + u) ±
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Part-VI-Consolidation - PART VI -A CONSOLIDATION: 1D...

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