Rak50.3125 Advanced course in Soil Mechanics
CALCULATION EXERCISE: SETTLEMENT OF AN EMBANKMENT ON SOFT CLAYS
Figure 1 shows the geometry of a typical Finnish road embankment on a sensitive clay which was
constructed in 2014. The sides of the road embankment has a slope of 1V:1.5H and the pavement
itself has 3% inclinations to both sides as shown in the Figure 1. Assume the unit weight of the fill
material is 20 kN/m3. The ground water table is 1m below the existing ground surface and the soil
profile beneath the embankment is shown in Figure 1. Necessary soil parameters that are needed to
perform the settlement analysis given in Table 1 below.
a. By performing necessary settlement calculations (Geoclac), find out the settlement vs. time
behavior of the embankment in 50 years (1,2,5,10,20,50 a) and draw the profiles of the
embankment at these times.
b.
Comment on the inclinations of the pavement after 1..50 years by referring to the Finnish
Road Authority regulations (InfraRYL) (App. 2). Check when the road needs repair mention
what kind of necessary actions can be taken to meet Finnish regulations (InfaRYL,
Appendix 2).
Figure1. Geometry of the road embankment and the soil profile beneath
Table 1. Soil parameters
Material
γ
γ'
σp
m1
m2
𝜷𝟏
𝜷𝟐
Dry Crust
Clay 1
Clay 2
Clay 3
17
15
16.5
15
7
5
6.5
5
60
44.5
37
62
10
7
8
5.5
50
110
120
75
0.7
-0.5
-0.5
-0.6
0.8
-0.3
-0.25
-0.25
Cv NC
m2/year
0.32
0.38
0.79
0.32
Cv OC
m2/year
3
4
8
3
Consolidation
pressure
?
?
?
?
You can make reasonable assumptions for any missing parameters.
Appendix 1 shows the effective insitu stresses (’v0, before construction) and consolidation pressures
’p obtained from oedometer tests.
Appendix 1
Effective insitu stresses ’v0 (before construction) and consolidation pressures p’ for
different layers from oedometer tests.
Appendix 2
InfraRYL 2006
Appendix 3
Painumaharjoitusohjeita (GeoCalc)
1. GeoCalc-program (Romm R266). Choose: Settlement.
2. Basic info to General-page (names, course, exercise etc.).
3. Creating model (Geometry, Soil Layers, Ground water polylines) like with Stability-program.
From Help you can find manuals etc. Figure below gives coordinates for layer borders and calculation
points
(minimum
number,
7
points,
shown
with
arrows).
-Matrial model: Ohde –Janbu (Parameters see Table 1)
- Consolidation Pressure: Choose right alternative for each layer (Constant
Cons.pressure/POP/Normally consolidated etc). according to Appendix 1 (sigma_p – sigma_v0).
Che
4. Road embankment is given a Load. Draw line according to geometry in Fig. above (density
20kN/m3).
5. Calculation points (Point->(Add points). (Arrows in Fig above).
6. Calculation: Calculate. Choose Primary Consolidation, Max time 50 years.
Calculation times: Initial calculation times: 1, 2, 5, 10, 15, 20, 50, Final (More times can be added
with + -button or from Load histories).
7. You can check results roughly from Results-figure after calculation. (Stresses and deformations
in different points can be checked by sliding the Point-tab with mouse).
8. More detailed analysis of results can be done at Graph-page by choosing time (1..,50v) ja and
points of interest (Most important are Points 3,4 ,5):
9. At Report-page (Brief Calculation Report) you can find numerical values for settlements at
different times etc. (Times 10, 20 ja 50v, Final):
9. Draw manually or with Autocad or Exel the sahpe of the embankments in the beginning and in
different times (1…. 50v, Final) according to results given in Report-page.
10. Calculate the inclinations of the road surface at different times (10v, 20v, 50v, Final) and compare
the values with values given InraRYL (Muut yleiset tiet).
Print results from GeoCalc (figures and data-tables with eg. print screen etc.). Compile the results
with (Exel-tables and Figures) in a report (max length 3-4 pages with figures). In the report you should
write short description what has been done (parameters, calculations, models, results) and estimate
the quality of the road in different times and when it need repair. Give some possible
improvements/actions to make it be better. The settlements of the left and right corner of the road act
different way with different times; why
Return the report to Henry Gustavsson within one week (before next exercise). The exercise can be
done in a group of 1-2 students.