CREEP AND CONSOLIDATION - Introduction to Soft Soil Geotechnique: Content, Context and Application - page 89

Settlement, using the non-linear compression according to (6.2), adopting for the
top a separate clay layer of 1 m thick and evaluation in the middle (to avoid the
zero stress state at the ground surface), leads to 0.99 m, and creep in 25 years
would add another 0.22 m, giving then a total settlement of 1.21 m.

application 6.3
A 5m layer of clay is consolidating under a surface load. Drainage is to the
surface. Settlement is monitored. 1m, 1.2m and 1.35m are measured after 60, 90
and 120 days respectively. Predict the hydrodynamic period. Predict the final
settlement.

application 6.4
A road embankment was placed 50 years ago on soft soil, and its settlement in
the last 10 years was 0.05 m. Determine the creep index c of the soft soil, if its
thickness is 10 m.

application 6.5
A clay layer in a planned industrial site is too soft for use so it is to be covered
by sand. The sand compresses the clay and gradually settles, thereby becoming
partially submerged under the groundwater table and so reducing the load on the
clay.
Clay data: layer 6 m thick, lies at surface, underlain by dense sand, wet unit
weight 15 kN/m 3 , saturated, groundwater table at surface, compressibility indices
a = 0.01, b = 0.1, c = 0.005, yield stress 25 kPa. Sand data: dry unit weight equals
16 kN/m 3 , porosity 40%, thickness 2 m. w = 10 kN/m 3 .

Find a maximum value of the settlement ( Z max ) of the clay layer after 10 4 days by
neglecting the gradual submergence of the load. Find a minimum value of the
settlement ( Z min ) of the clay layer after 10 4 days by assuming immediate
submergence to the value of Z max .
Hints: Consolidation effects may be disregarded. Take the stresses at 1/3 of the
layer depth as representative for the whole layer.

application 6.6
A Roman road built over a peat moor was eventually abandoned around 200 AD
At that time the road level was 20 cm above the moor. The moor adjacent to the
road grew upward by accumulation of dead plant material with a rate of 0.5
mm/year. Does consolidation plays a role in this problem? By how many years did
the peat level reach the road level without considering creep. By how many years
did soil creep hasten this event? Assume a peat layer of 3 m thick, having a c -value
of 0.0225.

application 6.7
What is the relation between the recompression index C r and the isotache
parameter a .