LAB MANUAL 8Consolidation

# LAB MANUAL 8Consolidation - CIVE 310 Soil Mechanics ONE...

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CIVE 310 Soil Mechanics ONE DIMENSIONAL CONSOLIDATION Section Assigned Due Before Lab: Read this Handout 76

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ONE-DIMENSIONAL CONSOLIDATION PROPERTIES OF SOILS Our lab today will be about consolidation. This particular test is also known as a one- dimensional (1-D Consolidation) test because the sidewalls of the consolidometer are fixed and allow movement in only the vertical direction. Why do we do consolidation testing? We do consolidation testing to estimate the magnitude and rate of consolidation settlement, mainly for clays. What do we need to find in order to estimate consolidation settlement? 1) Calculate σ V (also seen as P 0 ), the vertical effective stress on the soil at the depth we are concerned with. We estimate this by assuming unit weights and water pressures. 2) Estimate the preconsolidation pressure, σ p (also seen as P c or P p ), which is the maximum past vertical effective stress the soil has experienced. (See Example 1) 3) Estimate C c the Compression Index (the slope of the “virgin curve”). (See Example 1) 4) Estimate C r , the Recompression Index (the slope of the “recompression curve”). (See Example 1) We can find items 2 through 4 on the e-log σ ’ (log P) curve we get from our consolidation test. 5) Estimate C v , the Coefficient of Consolidation (units = T L 2 ). Knowing the load we will place on the soil, Δσ (or Δ P) and c V , we can estimate real settlements. (See Example 1 for determination of c V ) We can find c V when we plot settlement vs. time for the load increments we apply to our soil sample. When we run a consolidation test we need to calculate the value of certain parameters: When doing this you need to recall some of the relationships you established using phase diagrams for soil: Void Ratio = s v V V e = G s = the specific gravity of the soil V = A * H (Area * Height) Then s v s v AH AH V V e = = To determine the height of the solids , recall that: w s s s G W V γ = Since volume can be expressed as: s s AH V = 77
Then: w s s s G W AH γ = Rearranging, A G W H w s s s = The initial height of the voids is: s o vo H H H = Where; H 0 is the initial sample height, H s the height of the solids The initial void ratio is: s s o H H H e = 0 The void ratio during the test

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## This note was uploaded on 04/03/2008 for the course CIVE 310 taught by Professor Iforget during the Spring '08 term at Drexel.

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LAB MANUAL 8Consolidation - CIVE 310 Soil Mechanics ONE...

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