Geotechnical Engineering & Ground Improvement

This article discusses soil bearing capacity, foundation types, soil properties, consolidation, and challenges faced by geotechnical engineers in ground improvement. It includes equations to calculate ultimate bearing capacity for pad and pile foundations. The article also emphasizes the importance of soil compaction and consolidation to improve soil properties. The subject is relevant to civil engineering and geotechnical engineering courses.

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.

GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT 4
For laterally confined soil, ∆H= mvH0∆P
Where; mv = volume of compressibility
H0 = initial thickness of the soil
∆P = change in pressure
Compression index is given by;
Cc= ∆ e
log 10 P 1/ p 0 γ (Bartlett, 2010)
Thus,
∆e =Cc log10
p1
p 0
But ∆ H
H = ∆ V
V = ∆ e
1+∆ e = Cc log 10 p 1
p 0
1+∆ e
Therefore, consolidation settlement Sc is:
Sc = H0
Cc
1+ ∆ e log10
P 0+P 1
P 0
Task 2.3
There are numerous challenges which face geotechnical engineers during their design and
implementation of their design especially when it comes to ground improvement. This part
presents some of the challenges geotechnical engineers face.

GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT 5
 The high cost associated with improvement of onsite soil as the importation of
soil of better engineering properties ought to be very expensive. This increase the
cost of construction (Day, 2017).
 Changes in weather. Raining condition mostly interfere with the process of soil
improvement and sometimes tend to delay the activities. This is because rainwater
increases the water content of the soil beyond the permissible limit.
 The case of foundation settlement is very common, and this poses a challenge to
geotechnical engineers.

GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT 6
References
Bartlett, Steven. (2010). Shallow Foundations. [Online]. Available at:
http://www.civil.utah.edu/~bartlett/CVEEN6920/Shallow%20Foundations.pdf. Accessed
13th Aug 2018.
Day, Peter. (2017). Challenges and shortcomings in geotechnical engineering practice in the context of
a developing country. [Online]. Available at:
https://www.issmge.org/uploads/publications/1/45/03-terzaghi-oration-01.pdf. Accessed 13th
Aug 2018.