Consolidation Test Press (Oedometer Test)

The consolidation press runs the consolidation test, or oedometer test: it applies to the soil specimen, laterally confined in a ring and drained, stages of vertical load that are held constant until consolidation is complete, while the change in height is measured. The test yields the compression index Cc, the preconsolidation pressure and the coefficient of consolidation cv, which predict how much and how fast a clay layer will settle.

ABNT NBR 16853:2020, Soil: one-dimensional consolidation test (the Brazilian standard). It absorbed the technical content of NBR 12007, withdrawn on 07/20/2015, and remains in force. In highway work in Brazil, DNER-IE 005/94 is also used, and laboratories that follow US standards use ASTM D2435/D2435M.

Yes. Biopdi's electric automatic consolidation press is the PCM-5k CBR, Marshall and Consolidation Press, rated at 50 kN. Changing the fixture changes the test: oedometer cell for consolidation, penetration piston for CBR and compression mold for Marshall. If you already have the automatic CBR / Marshall test press, you only need the consolidation fixture and a suitable load cell.

On the manual press, the load comes from slotted weights, up to 500 kgf (4.9 kN), multiplied by a lever, and the height is read on a dial indicator. On the electric automatic press, the ball screw applies the load and holds it constant at each stage, the load cell measures the force, the LVDT measures the height, and the press takes the readings at the test times and saves the data to the SD card.

Two, 2-inch and 3-inch (D2P-ADS and D3P-ADS). Each is an oedometer cell with a rigid base, specimen ring, porous stones and a rigid loading cap, and it allows the sample to be submerged. NBR 16853 requires a ring with an inside diameter of at least 50 mm and a diameter-to-height ratio of at least 2.5; state the ring diameter your laboratory uses when you request a quote.

The press reads the specimen height at 1/8, 1/4, 1/2, 1, 2, 4, 8, 15 and 30 minutes and at 1, 2, 4, 8 and 24 hours after each load increment, plus more if needed. These are the times of DNER-IE 005/94, the same as in NBR 16853, and they are used to plot the height versus log of time and versus square root of time curves from which cv is obtained.

The force is the stage pressure times the ring area. In a 63.5 mm ring taken to 1,280 kPa, the maximum force is about 4.05 kN, and a 500 kgf (4.9 kN) load cell covers the test with better resolution in the low stages. The 50 kN of the press is more than enough; what you size is the load cell, interchangeable from 5 to 5,000 kgf.

Each load stage usually lasts 24 hours, and the pressures double at each stage (about 10, 20, 40 kPa and so on) until the virgin compression range is defined; then come at least three unloading stages. A complete test takes one to two weeks, which is why automatic data acquisition spares the operator the overnight readings.