Shallow Foundation: Plate Load Test

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plate load test is useful to estimate bearing capacity of soil on field.
The test procedure is given in IS:
1888–1982 (Revised). The procedure, in brief, is as follows:
(i) After excavating the pit of required size and levelling the base, the test plate is
seated over the ground. A little sand may be spread below the plate for even support. If ground water is encountered, it should be lowered slightly below the base by
means of pumping.
(ii) A seating pressure of 7.0 kN/m2 (70 g/cm2) is applied and released before actual
loading is commenced.
(iii) The first increment of load, say about one-tenth of the anticipated ultimate bearing
capacity, is applied. Settlements are recorded with the aid of the dial gauges after 1
min., 4 min., 10 min., 20 min., 40 min., and 60 min., and later on at hourly intervals
until the rate of settlement is less than 0.02 mm/hour, or at least for 24 hours.
(iv) The test is continued until a load of about 1 1
2 times the anticipated ultimate load is
applied. According to another school of thought, a settlement at which failure occurs
or at least 2.5 cms should be reached.
(v) From the results of the test, a plot should be made between pressure and settlement, which is usually referred to as the ‘‘load-settlement curve’’, rather loosely.
The bearing capacity is determined from this plot, which is dealt with in the next
subsection.