Principles of Geotechnical Engineering (MindTap Course List)
9th Edition
ISBN: 9781305970939
Author: Braja M. Das, Khaled Sobhan
Publisher: Cengage Learning
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Chapter 11, Problem 11.9P
To determine
Calculate the primary consolidation settlement of the clay layer.
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In a normally consolidated clay specimen, the following
data are given from the laboratory consolidation test.
e₁ = 1.10
σ= 65.0 kN/m²
€₂ = 0.85
o₂ = 240.0 kN/m²
a. Find the compression index C.
b. What will be the void ratio when the next pressure incre-
ment raises the pressure to 460.0 kN/m²?
Refer to the soil profile shown in figure below. A laboratory consolidation test on the clay gave
the results:
o'c = 100 kPa
Cc = 0.4
Cs = 0.2Cc
If the average effective stress on the clay layer increases by 60 kN/m², what would be the total
consolidation settlement in cm.
Dry sand; e = 0.55 G,= 2.66:
Sand G₂ = 2.66 e = 0.48.
Clay w 34.78% G₂ = 2.74
Rock
1.5 m.
5 m
Water table;
Solve the following problems using the figure.
1. Calculate the ultimate settlement of the clay layer.
2. Calculate the excess pore pressure (ue) and the
effective stress at the midpoint of the clay layer
after 3 years.
10'
Fill, y = 118b/³
Sand, y 109 lb/ft³
Sand, Ysat 114 lb/ft³
eo = 1.1
Cc = 0.25
C₁ = 7 ft²/yr
C₁ = 0.06
clay
14'
N.C
Ysat = 122 lb/ft³
sand
8.
For the previous problem, report the predicted settlement after 365 days.
3. Create a plot (or plots) in a spreadsheet showing
the hydrostatic pressure in the clay with depth and the excess pore pressure (ue) with
depth after 3 years and the combined pore pressure after 3 years. (This is similar to an
example worked in class)
4.
Calculate the average percentage of consolidation (U%) for the clay layer after 3 years.
5. How long will it take for 80% of the ultimate settlement of the clay layer to take place?
6. Assume thin layers of drainable sand are present every two feet within the clay so it is
actually five clay layers that…
Chapter 11 Solutions
Principles of Geotechnical Engineering (MindTap Course List)
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- The following are the results of a consolidation test on a sample of a clayey soil. • Plot the e-log o curve. • Determine the pre-consolidation pressure. • Calculate the compression index, Ce and the ratio of C; /Ce. Pressure, o' (kN/m?) 1.113 25 1.106 50 1.066 100 0.982 200 0.855 400 0.735 800 0.63 1600 0.66 800 0.675 400 0.685 200arrow_forwardA normally consolidated clay has the following values. Void ratio, e k (cm/sec) 1.5 0.2 × 10-6 1.9 0.91 × 10–6 Estimate the magnitude k of the clay at a void ratio (e) of 0.9. Use en k = C 1+e (Enter your answer to three significant figures.) k = cm/secarrow_forwardFor a normally consolidated soil, the following is given: Determine the following: a. The compression index, Cc. b. The void ratio corresponding to pressure of 200 kN/m2arrow_forward
- A given saturated clay is known to have effective strength parameters of c' = 10 kPa and = 28°. A sample of this clay was brought to failure quickly so that no dissipation of the pore water pressures %3D could occur. At failure it was known that o KPa, o = 10 KPa and = 20 kPa. %3D (a) Estimate the values of o, and oz at failure (b) Use the Mohr circle to illustrate the effective stress and total failure stress.arrow_forward1. The pressure versus void ratio data determined from a consolidation test on an undisturbed clay specimen are as follows: Applied Pressure (kPa) 20 40 80 160 320 640 1280 320 80 20 0 Void Ratio 0.953 0.948 0.938 0.920 0.878 0.789 0.691 0.719 0.754 0.791 0.890 (a) Plot this pressure versus void ratio data on a semi-logarithmic graph. (b) Determine the equations for the virgin compression curve and for the rebound curve for unloading starting at 1,280 kPa. (c) What are the corresponding compression and recompression indices for this soil? (d) Estimate the stress to which this clay has been preconsolidated. (After A. Casagrande.)arrow_forwardRedo Problem 11.6 using the weighted average method [Eq. (11.68)] to calculate the stress increase in the clay layer. Problem 11.6 Refer to Figure 11.43. Considering the soil to be a uniform clay layer, estimate the primary consolidation settlement due to the foundation load. Given: P = 150 kN; B = 3 m; L = 3 m; D, = 1.5 m; H = 8 m; e = 0.7; G, = 2.72; and LL = 42. Assume that the clay is normally consolidated, and the groundwater P table is at the foundation level. Use Ao = BL Figure 11.43 Foundation BxL Ao Soil H, = Poisson's ratio E, = modulus of elasticity H %3D Rock Figure 11.43 ©Cengage Leam ing 2014arrow_forward
- Refer to the soil profile shown in Figure P2.12. The clay is normally consolidated. A laboratory consolidation test on the clay gave the results: If the average effective stress on the clay layer increase by 50 kN/m2.a. What would be the total consolidation settlement?b. If Cv = 9.36 x 10-4 cm2/sec, how long will it take for half the consolidation settlement to take place?arrow_forward4. Figure Q4 shows a soil profile loaded with a uniformly distributed load, Ao=50kPa. The water table is located 2.5m below ground level and the soil above can be considered to be completely dry. The unit weight of the soil in each layer is given in the figure. Assume a unit weight for water, ywater=10KN/m. Results from an oedometer test carried out on a clay sample provide the following consolidation parameters: Preconsolidation stress, o'p=125kPa Recompression index, C,=-0.06 Compression index, Cc=-0.36 Initial void ratio, eo=0.9 Determine the consolidation settlement at the middle of e clay layer Aa'=50kPa dry sand Yary=16.5kN/m 2.5m saturated sand Ysat =18.8kN/m 4.5m saturated clay yat 19.2kN/m' e,=0.9 o =125kPa 5.0m Figure Q4arrow_forward5. For the soil profile given below, assume that the primary consolidation settlement for the clay layer is completed in 3 years. Estimate the secondary consolidation settlement for the clay layer at the end of 10 years. Yw= 10kN/m³, Ca = 0.03 1m 1.5m 2m Groundwater table 0.5m BXL = 2m x 4m Sand y = 17.0 kN/m³ 90 = 100kPa Sand Ysat = 19.0 kN/m² Normally consolidated Clay Ysat = 20 kN/m³ eo = 0.7 Cs = 0.09 Cc = 0.2 -arrow_forward
- As indicated in the following figure, an incompressible silty sand fill 16.4 ft thick was placed on top of a 49.2 ft thick layer of soft and compressible silty clay. Underlying the clay is a layer of incompressible sandy gravel. The soil properties of the silty clay layer are given in the following figure. The ultimate settlement, Sult = 5.64 ft, from the primary consolidation of silty clay layer due to the weight of the silty sand fill is calculated. O ft Fill Material - Silty Sand (SM), y = 124.86 pcf, 16.4 ft Silty Clay (CL) 94.89 pcf Y = Normally Consolidated 1.1 e, = Cc = 0.36 0.06 Cv = 9.235 ft/year 65.6 ft Dense Sandy Gravel (GP), Incompressible layer 82.0 ft A) Find the time rate of settlement by showing the Time [year] vs. Settlement [ft] curve. Show sample calculation when percentage of consolidation, Ugyg = 50%arrow_forwardC 5. For the soil profile given below, assume that the primary consolidation settlement for the clay layer is completed in 3 years. Estimate the secondary consolidation settlement for the clay layer at the end of 10 years. Yw= 10kN/m³, Ca = 0.03 t 1m 1.5m 2m Groundwater table 0.5m 90 = 100kPa BXL = 2m x 4m Sand y = 17.0 kN/m³ Sand Ysat = 19.0 kN/m³ = Normally consolidated Clay Ysat = 20 kN/m³ eo = 0.7 Cs= 0.09 Cc = 0.2arrow_forward2.9 A normally consolidated clay has the following values. Void ratio, e k (cm/sec) 0.2 × 10 0.91 x 10-6 1.2 1.9 Estimate the magnitude of k of the clay at a void ratio (e) of 0,9. Use Eq. (2,41).arrow_forward
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