Geotechnical Engineering & Ground Improvement

Running head: GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT 1
Geotechnical Engineering & Ground Improvement
Name
Institutional

GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT 2
Geotechnical Engineering & Ground Improvement
Task 2.1
Terzaghi developed the formula which can be used to calculate the soil bearing capacity
of foundations which are shallow. Given the cohesion, unit weight as well as the surcharge, the
following equation can be used;
qu= cNcSc + γ DNqSq + 0.5BγNγS γ (Bartlett, 2010)
Where;
qu = ultimate bearing capacity
D = foundation depth
B – Breadth of the foundation
Nc, Nq, Nγ, and, Sc, Sq and S γ are factors called bearing capacity and shape factors (Bartlett, 2010)
Development Area 1
The type of footing used is pad footing and supports a load not exceeding 800 kN. Also,
the foundation supports a perimeter wall having a load not exceeding 70 kN/m.
Taking the shape of the footing to be a square, the following equation can be used to determine
Qu
Qu = 1.3cNc + γ DNq + 0.4 γ BγNγ
Where D = 2.4m, B = 2.5m, and the angle of friction φ =20° Nc =17.69, Nq= 7.44 and Nγ= 3.64.
Assuming the unit weight of clay to be 20 KN/m3, Qu is calculated as shown below
qu = (1.3×35×17.69) + (20×2.4×7.44) + (0.4×20×2.5×3.64)

GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT 3
= 807.895 + 357.12 + 72.8
= 1237.815 KN/M2
Taking the type of foundation to be a pile foundation, skempton equation can be used
Here, Nc = 9. Thus, Qu is given by the equation;
Qu= αcAf + 9CAb where; Ab= ❑
4 B2 and Af = BD
Thus, Qu =αBDc +2.25 B2c, Taking Cu = 35 KN/m2, B = 600mm, D = 8m, and α =0.57
Qu = (0.60×0.6×8×35) + (2.25× 0.62 × 35)
= 100.8 + 89.019
= 189.819 KN/m2
Task 2.2
The soil properties of the site should be ensured that it is of a good standard and is well
compacted. Compaction is done to reduce voids. By minimising the voids, the engineering
properties of the soil is improved. The properties of the soil at the site can also be enhanced
through consolidation. This involves applying loads on the soil to improve the bearing capacity
of the soil. The load is applied over a given period to ensure required consolidation is achieved.
Weak soil provides room for foundation settlement. Thus, it should be ensured that the
site is well compacted as well as well consolidated. Through this, the bearing soil would be able
to withstand the load from the superstructure. This is because the overlying structure tends to
exert some pressure which reduces soil voids which in turn makes the foundation to settle.
However, the settlement should be within the permissible limit.