Geotechnical design

TABLE OF CONTENTS

QUESTIONS 2
SOLUTIONS 2
Question 1 2
Question 2 5
Question 3 5
Question 4 6
Question 5 7
REFERENCES 9

QUESTIONS

1) Determine the total consolidation settlement of the clay layer after application of the maximum load or pressure from the tank. Assume the tank is founded at existing ground level.
2) Determine the overall settlement of the superficial deposits (above rockhead) after the application of the maximum pressure from the tank.
3) Determine the time required to reach 75% consolidation settlement.
4) Determine the bearing capacity of the soil at 4.0 m below ground level, assuming the tank will be founded at this level on a rigid 0.5 m thick reinforced concrete slab with minimum width of 6.0 m.
5) If the tank foundations are to be piled, assume foundation level of 4.0 m below ground level with the maximum load of the tank and foundation slab (0.5 m thick reinforced concrete slab with dimensions matching the base dimensions of the tank) is equally distributed over thirty (30 no.) precast piles 0.30x0.30 cm2 cross-section, driven down though the alluvial sands/gravel to bear within the clay layer. Determine the pile length for FoS=2 on the ultimate bearing capacity.

SOLUTIONS
Question 1

Empty tank weight: 1554.13 KN
Tank dimensions: - Width: B=7.87 m - Length: L=9.15 m - Height: h=5.00 m
Total tank load: 1554.13+(7.87×9.15×5.0×9.81)=5,086.24 KN

From the Fadum chart: q=5,086.24⁄((9.15x7.78))=70.63 KN/m^2 Top of the clay (Z=10 m) Bottom of the clay (Z=20 m) n=L⁄((Z)) 9.15⁄10 = 0.4575 9.15⁄20 = 0.2288 m=B⁄((Z)) 7.87⁄10 = 0.3935 7.87⁄20 = 0.1968 I_σ 0.066 0.020 σ_z=q× I_σ 70.63 × 0.066 × 4 = 18.65 70.63 × 0.020 × 4 = 4.8
Vertical Stress (kN/m2) 18.65 5.65

d_sand = 1780 Kg/m^3 γ_sand = (1780 x 9.81)/1000 = 17.46 KN/m^3
Before Construction Top of clay Bottom of