The main observation of the plate load test is:

Asked in SSC JE 2015

Detailed Explanation

In a plate load test the load is applied in steps by a jack, and dial gauges resting on the plate record how much it moves down.

Why “Settlement of the test plate” Is Correct

The quantity that is observed and recorded is the settlement of the test plate under each load step. Plotting load against plate settlement gives the curve from which the ultimate bearing capacity and the safe bearing pressure are worked out.

Plate load test (IS 1888). A rigid steel plate, 300 mm to 750 mm square (or circular) and at least 25 mm thick, is seated at foundation level at the bottom of a pit at least five times the plate width. A hydraulic jack pushes the plate against a reaction beam held down by kentledge or soil anchors. Load is applied in steps and the settlement of the plate is read on dial gauges for each step.

Why the Other Options Are Wrong

B. Stability of soil: Stability is inferred from the results, not observed directly.
C. Stability of the test plate: The plate's stability is not the purpose of the test.
D. Settlement of soil: The gauges read the plate's movement; soil settlement elsewhere is not measured.

Key Point

Plate load test observation: load vs settlement of the plate.

Key Concepts for Students

Settlement readings are taken at intervals until the rate becomes very small.
The test is stopped at failure or at about 25 mm settlement.
Settlement of a real footing is estimated from the plate settlement by size correction.

Practice more: this is question 39 in Shallow and Deep Foundation MCQs – Part 3. Try the whole set and check every answer instantly.