Hydro-Mechanical Properties of an Unsaturated Frictional Material

10.2. BEARING CAPACITY EQUIPMENT 199
45 mm
477 mm
Figure 10.4: Model strip footing
79 mm
Model strip footing
2 burettes (1 at each side), that are used to apply suction to the specimen by hanging water
column technique. Bearing capacity tests are performed using a model footing 477 mm in
length, 79 mm in width and 45 mm in height, that is a strip footing. The strip footing is
made of steel and is shown in Fig. 10.4. The friction angle was determined for plane strain
loading conditions using a double wall cell (Schanz & Alabdullah 2007, Alabdullah & Schanz
2009). The measured friction angle was equal to φ = 46.9 ◦ . The calculations using Rankine’s
analysis shows that the failure zones extends to a length approximately equal to 500 mm and
the maximum depth to 100 mm. The box was designed such that the box dimensions are
greater than the calculated values of the failure zone (i.e. 1000 mm in length, 500 mm in
width and 500 mm in height). The failure mechanism is given in Fig. 10.5. Additionally the
box may be equipped also with tensiometer sensors in several depth for measuring pore-water
pressure. The bearing capacity equipment is placed in a loading frame. Using the loading
frame the bearing capacity was measured by loading the surface footing in the saturated
specimens as well as unsaturated specimens. During the test the loading system is measuring
settlements and the applied load. The accuracy of settlement readings is 0.001 mm and the
10 cm
α β
25 cm
α = 45°+ φ/2
β = 45° - φ/2
Figure 10.5: Failure below strip footing following Rankine