case study on plat load test

2.  Geotechnical engineering -2
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3.  The Plate Bearing Test is done when shallow foundations are to be
used, or when temporary work structures such as piling rigs or cranes
would be required on site.
 This test checks the bearing capacity of the soil near the surface of the
ground.
 It also checks the possible settlement under a certain load.
 The standards applicable to this test are British Standard (BS) 1377 Part
9 and American Society for Testing and Materials (ASTM) D1194.

4.  Test in which a load is repeatedly applied and released in
increments using a circular loading plate aided by a loading
device, with the settlement of the loading plate being measured.

5. Figure shows how this test is set up. Basically, it contains a plate,
loading column, jack, counter weight, pressure gauge and settlement
gauge.

6.  The Plate Load ( ASTM D-1194-72), involves determining the Ultimate
Bearing Capacity of the soil and the Likely settlement under a given
load. The Test basically consist of loading a steel plate placed at the
foundation Level and recording the settlement corresponding to each
load increment. Typical Loading curves for different soil types is shown
below.

8.  Test Pit of less than 1m was dug at the Proposed Foundation Level, with
width at least 5 times the width of the Test Plate. A circular Steel Plate
with thickness not less than 25mm and diameter 30cm was used. A
reaction load was placed over a 700 bar capacity hydraulic Jack, which
lies on a Test Plate after the placement of a sitting load of 7KN/m2. Each
Load increment was kept for not less than one hour or when the
settlement gets appreciable reduced ( a value of 0.2mm per hour). The
next Increment was then applied and observation repeated. The Test was
continued till a settlement of 25mm or more was obtained.

9. Presure, kpa Initial dial
reading
Final dial
reading
Settlement Cum.
Settlement
66.694 50.529 47.175 3.354 3.354
133.389 47.175 43.2 3.975 7.329
266.778 43.2 26.35 16.85 24.179
306.794 26.35 16.47 9.88 34.059

11. Pressure, kpa Intial dial
reading
Final dial
reading
settlment Cum.
settlement
66.69 50.15 45.89 4.26 4.26
133.39 45.89 42.45 3.44 7.7
266.78 42.45 27.91 14.54 22.24
293.46 27.91 22.31 5.6 27.84

13. Pressure , kpa Intial dial
reading
Final dial
reading
settlement Cum.
Settlement
66.69 50.12 47.73 2.385 2.385
133.39 47.73 45.28 2.45 4.835
266.778 45.280 24.184 21.096 25.931
400.167

15. Pressure, kPa Initial Dial
Reading
Final Dial
Reading
settlement Cum. settlement
66.694 50.21 45.619 4.591 4.591
133.389 45.619 42.32 3.299 7.89
266.778 42.32 33.345 8.975 16.865
333.472 33.345 22.65 10.694 27.56

17.  The Safe Bearing Capacity was obtained using plate load test based on
25mm Permissible Settlement with a footing size of 1m in the area of
investigation. The Result obtained is in congruent with the Soil
Compressive Strength. The classification of the soil based on the
IProperties also correlates reasonably with load - settlement Curve
obtained from the Plate Load Tests.
 The low degree of dispersion of results as obtained from the Coefficient
of Variation shows that the Plate Load Test method of obtaining the Safe
Bearing Capacity based on Permissible Settlement on a partially
cohesive soil is reliable in the region.

18.  Allen, J. R, L., (1965) Late Quaternary Niger Delta and Adjacent Areas:
Sedimentary Environmental and Lithofacies. AAPG Bulletin, 49(5):
547-600.
 Das. B.M (1994) Principles of Foundation Engineering . 3rd ed. PWS
Publishing Company,
 Boston Geological Survey of Nigeria (1957), “Geological Map of
Calabar sheet 85”. first edition 1957.

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