Example

Example: The Effect of PVDs on Consolidation Time

A 10-meter thick layer of normally consolidated clay rests on impermeable bedrock. The water table is at the surface. A large surcharge fill is placed on top. The clay has a coefficient of consolidation for vertical flow (cvc_v) of 1.5 m2/year1.5 \text{ m}^2/\text{year} and for horizontal flow (chc_h) of 3.0 m2/year3.0 \text{ m}^2/\text{year}. Compare the time required to achieve 90% consolidation (U=90%U = 90\%) with and without the installation of PVDs.

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Example

Example: Preloading Surcharge Calculation

A new warehouse is to be built on a 4 m thick layer of compressible clay. The warehouse floor will exert a permanent uniform load of Deltap=50 kPa\\Delta p = 50 \text{ kPa}. The clay has a consolidation coefficient cv=1.2 m2/monthc_v = 1.2 \text{ m}^2/\text{month}. The target settlement is 100%100\% of primary consolidation (U=100%U = 100\%). To accelerate this, a surcharge load (Deltaps\\Delta p_s) will be added. The total preload is pf=Deltap+Deltaps=80 kPap_f = \\Delta p + \\Delta p_s = 80 \text{ kPa}. Determine the required degree of consolidation (UsurchargeU_{surcharge}) under the 80 kPa80 \text{ kPa} load to achieve the equivalent 100%100\% settlement of the 50 kPa50 \text{ kPa} load.

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Example

Example: PVD Spacing and Equivalent Diameter

Prefabricated Vertical Drains (PVDs) are being used to accelerate consolidation. The PVDs have a width a=100 mma = 100 \text{ mm} (0.1 m0.1 \text{ m}) and a thickness b=5 mmb = 5 \text{ mm} (0.005 m0.005 \text{ m}). They are installed in a triangular grid pattern with a spacing of S=1.5 mS = 1.5 \text{ m}. Calculate the equivalent diameter of the drain (dwd_w) and the diameter of the influence zone (ded_e).

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Example

Example: Radial Consolidation Time

Using the PVDs from the previous example (de=1.575 md_e = 1.575 \text{ m}, dw=0.0668 md_w = 0.0668 \text{ m}), the horizontal coefficient of consolidation of the clay is ch=2.0 m2/monthc_h = 2.0 \text{ m}^2/\text{month}. Calculate the time required to achieve 90%90\% average degree of radial consolidation (Ur=0.90U_r = 0.90). Assume no smear or well resistance for simplicity.

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Example

Case Study: Vibro-Compaction for Liquefaction Mitigation

A new power plant is being constructed near a river delta. The upper 10 meters of the site consists of very loose, saturated, clean sand. Seismic analysis indicates a very high risk of liquefaction during an earthquake.

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Example

Case Study: Electro-Osmosis on a Landslide

A sensitive, highly plastic clay slope adjacent to a critical railway line was experiencing slow, continuous creeping movement due to high internal pore water pressures. Traditional drainage methods were ineffective because the clay's permeability was extremely low (k<109 m/sk < 10^{-9} \text{ m/s}).

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