Embankment foundation design
Given data :
380 3.1 18 3.2 3.5E-10 6.9 40 8 100E-09
Based on the given data, the embankment foundation should be designed. The height of the
road infrastructure is 5 m, the width of the embankment is 12 m on the crest, the slope angle is
1:1,5.
The consolidation time should be lower than it is given in the table.
The study should include the following:
1) Analysis of settlement, consolidation time and stability (without any improvement technology)
- settlement should be calculated for the upper layer and for the bottom layer separately and
than you have to add them. This will be the settlement without using ground improvement -
consolidation time shoud be calculated only for the upper layer (because the hydraulic
conductivity is lower for the upper layer) - stability should be calculated only for the upper layer
2) Select a technology to solve the calculated problem. Please explain why you have chosen that
technology.
3) Verify the selected technology. It means that you have to calculate the settlement,
consolidation time and stability applying the selected technology. (Pribe diagram, Barron curves,
…) Based on the calculation, please prepare an engineering report.
Solution:
1 – Embankment:
• Y = 20 kN/m³
• H=5m
• Lroad = 12 m
• La = 7.5 m
• Slope lateral = 1:1.5
2 – Upper layer:
• Yupper = 18 kN/m³
1
, • Z1 = 3.1 m
• Cu = 18 kPa
• Es = 3.2 MPa
• K = 3.5x10-10
3 – Bottom layer:
• Ybottom =19 kN/m³
• Z1 = 6.9m
• Cu = 40 kPa
• Es = 8 MPa
• K = 1x10-9
Analysis of the settlement
Construction time 380 days
5 5
Embankment shoulders : = = 7.5 𝑚
tan 𝜃 33.7
For Upper layer:
➢ Consolidation settlement
𝐻∗𝛾 5 ∗ 18
𝑆= ∗ℎ = ∗ 3.1 = 0.87𝑚 = 8.7 𝑐𝑚
𝐸𝑠 3200
➢ Consolidation time :
𝐾𝐸𝑠 3.5x10−10 ∗ 3200
𝐶𝑣 = = = 1.12 ∗ 10−7 𝑚2
𝛾𝑤 10
1 1
𝑇 = 𝐶𝑣 2 ∗ 𝑡 = 1.12 ∗ 10−7 ∗ ∗ 300 ∗ 86400 = 0.3𝑠𝑒𝑐
𝐻 3.12
Hence
𝐾𝐸𝑠
𝑇= ∗𝑡
ℎ2∗ 𝛾𝑤
3.5x10−10 ∗ 3200
0.3 = ∗𝑡
(3.1)2 ∗ 10
𝑡 = 9.8𝑚𝑜𝑛𝑡𝑠 > 3 − 4 𝑚𝑜𝑛𝑡ℎ
➢ Rotational stability:
2
Given data :
380 3.1 18 3.2 3.5E-10 6.9 40 8 100E-09
Based on the given data, the embankment foundation should be designed. The height of the
road infrastructure is 5 m, the width of the embankment is 12 m on the crest, the slope angle is
1:1,5.
The consolidation time should be lower than it is given in the table.
The study should include the following:
1) Analysis of settlement, consolidation time and stability (without any improvement technology)
- settlement should be calculated for the upper layer and for the bottom layer separately and
than you have to add them. This will be the settlement without using ground improvement -
consolidation time shoud be calculated only for the upper layer (because the hydraulic
conductivity is lower for the upper layer) - stability should be calculated only for the upper layer
2) Select a technology to solve the calculated problem. Please explain why you have chosen that
technology.
3) Verify the selected technology. It means that you have to calculate the settlement,
consolidation time and stability applying the selected technology. (Pribe diagram, Barron curves,
…) Based on the calculation, please prepare an engineering report.
Solution:
1 – Embankment:
• Y = 20 kN/m³
• H=5m
• Lroad = 12 m
• La = 7.5 m
• Slope lateral = 1:1.5
2 – Upper layer:
• Yupper = 18 kN/m³
1
, • Z1 = 3.1 m
• Cu = 18 kPa
• Es = 3.2 MPa
• K = 3.5x10-10
3 – Bottom layer:
• Ybottom =19 kN/m³
• Z1 = 6.9m
• Cu = 40 kPa
• Es = 8 MPa
• K = 1x10-9
Analysis of the settlement
Construction time 380 days
5 5
Embankment shoulders : = = 7.5 𝑚
tan 𝜃 33.7
For Upper layer:
➢ Consolidation settlement
𝐻∗𝛾 5 ∗ 18
𝑆= ∗ℎ = ∗ 3.1 = 0.87𝑚 = 8.7 𝑐𝑚
𝐸𝑠 3200
➢ Consolidation time :
𝐾𝐸𝑠 3.5x10−10 ∗ 3200
𝐶𝑣 = = = 1.12 ∗ 10−7 𝑚2
𝛾𝑤 10
1 1
𝑇 = 𝐶𝑣 2 ∗ 𝑡 = 1.12 ∗ 10−7 ∗ ∗ 300 ∗ 86400 = 0.3𝑠𝑒𝑐
𝐻 3.12
Hence
𝐾𝐸𝑠
𝑇= ∗𝑡
ℎ2∗ 𝛾𝑤
3.5x10−10 ∗ 3200
0.3 = ∗𝑡
(3.1)2 ∗ 10
𝑡 = 9.8𝑚𝑜𝑛𝑡𝑠 > 3 − 4 𝑚𝑜𝑛𝑡ℎ
➢ Rotational stability:
2
