Geotechnical Engineering & Ground Improvement

This article discusses soil bearing capacity calculation for shallow and deep foundations, consolidation, compaction, and challenges faced by geotechnical engineers in ground improvement. It includes solved examples and references.

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Running head: GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT
Geotechnical Engineering & Ground Improvement
Student’s Name
Institutional Affiliation

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GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT
Geotechnical Engineering & Ground Improvement
Task 2.1
The soil bearing capacity for shallow foundation can be calculated using the Terzaghi’s
ultimate bearing capacity equation. When the unit weight and the cohesion of the soil in addition
to the surcharge are considered, the equation below can be applied:
qu= cNcSc + γ DNqSq + 0.5BγNγS γ (Das, 2017)
Where:
 qu is the ultimate bearing capacity
 D is the depth of the foundation
 B is the width of the foundation, and
 Nc, Nq, Nγ, and, Sc, Sq and S γ are bearing capacity and shape factors respectively (Das,
2014).
In Development Area 1, a pad footing is used to support loads of up to 800 KN. In addition to
that, a strip foundation supports a perimeter wall load of up to 70 KN/m.
For square footing:
Qu = 1.3cNc + γ DNq + 0.4 γ BγNγ
Taking D= 2.10m; B= 3m and the angle of friction φ =20° Nc =17.69, Nq= 7.44 and Nγ= 3.64.
Also, assume a unit weight of 20KN/m3 for clay soil.
Therefore, qu = (1.3×35×17.69) + (20×2.1×7.44) + (0.4×20×3.64)
= 804.895 + 312.480 + 29.120

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GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT
=1146.495 KN/m2
Pile foundation
According to Skempton, for a deep foundation, Nc = 9. Therefore;
Qu= αcAf + 9CAb.
For a pile of diameter B and embedded depth D
Ab= ❑
4 B2 and Af = BD
Therefore, Qu =αBDc +2.25 B2c
With Cu=35KN/m2 and using a concrete pile of B= 400mm and D= 10 meters. Taking the
adhesive factor α =0.60
Qu =(0.60×0.4×10×35) + (2.25× 0.42 × 35)
=84+ 39.58
=123.58 KN/m2
Task 2.2
The engineering properties of a site should be improved in cases where the ground
quality is not up to standard. This can be done by reducing the volume of voids in the soil,
reducing pore water pressure and using stronger materials. The main methods of achieving this
are consolidation and compaction. Consolidation is the improvement of the soil bearing capacity
of a soil mass by the application of load over a given period.

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GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT
Alluvial soil deposits have a large of amount of water that heavily reduces its soil bearing
capacity. Therefore, to increase its bearing capacity, consolidation is used. If the ground quality
is not improved, settlement tend to happen as the soil mass is consolidated as the result of the
load of the structure.
Stress increment because of the new structure will cause a reduction in the void ratios. As
a result, the height of the soil layer reduces. For a laterally confined soil
∆H= mvH0∆P
Where:
 mv is the volume of compressibility
 H0 is the initial thickness of the soil
 ∆P is the change in pressure.
By definition, the compression index Cc is:
Cc= ∆ e
log 10 P 1/ p 0 (Hirkane et al., 2014)
Therefore;
∆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

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GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT
Task 2.3
Geotechnical engineers are faced with numerous challenges when attempting to implement the
various ground improvement solution. Some of these challenges include:
 Unpredictable weather. When trying to improve the soil quality through the expulsion of
water, raining conditions may reverse the process hence nullifying all the work (Hirkane
et al., 2014). Additionally, swelling of clay due to moisture may interfere with the works.
 Improvement, which entails the importation of soils with better engineering properties,
incurs high costs that increases the cost of construction.
 In addition, incidences of uneven settlement after consolidation and compaction are
common.

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GEOTECHNICAL ENGINEERING & GROUND IMPROVEMENT
References
Das, B. M. (2017). Shallow foundations: bearing capacity and settlement. CRC press.
Hirkane, S. P., Gore, N. G., & Salunke, P. J. (2014). Ground Improvement
Techniques. International Journal of Inventive Engineering and Sciences, 2, 11-13.