Consolidation By Attila Bukholcz, Michael Tse, Tong Haibin

Consolidation occurs when a stress is applied to a soil. Therefore it decreases its volume with time. When the soil is saturated with water, it will be squeezed out due to the pressure.

 The oedometer test is a popular method to determine the consolidation properties. The apparatus consists a vertically loaded one-dimensional cell.

 The sample is placed in a metal ring, then it is inserted into a hydraulic cell. Previously the water content of the soil has been determined.

 The specimen is covered with porous plates in the top and the bottom, that can allow pore water to escape. These plates need to be previously saturated with water.  During the test the cell is filled up with water to ensure the saturation of the sample.

 The oedometer is fitted with a device that measures the settlement of the soil specimen. This device is connected with a computer that records the time (in seconds) and the settlement (in digital units).

 In the loading period the pressure is applied to the surface of the specimen through the porous disc, so that the surface always remains plane.  Before the actual test starts, the sample needs to be preloaded with 10kPa (2.5kg of applied weight).

 In the first stage of the loading the displacement was increased steadily. It reached a level where there was no further volume change occurring. This was the end of the primary consolidation. At this stage the stress was doubled and the recording of data was restarted.  If the load remained for a longer time secondary consolidation would have occurred.

Calculations  Initial moisture content  Initial density of the specimen

Calculations  Initial dry density  Particle density of the soil

Calculations  Initial void ratio

End of presentation Thanks you!