Geotechnical engineering -2 prepared by:- 14soecv11040 14soecv11035 14soecv11025 14soecv11021

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.

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.

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

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.

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.

Presure, kpa

Initial dial reading

Final dial reading

Settlement Cum. Settlement

66.694 50.529 47.175 3.354 3.354133.389 47.175 43.2 3.975 7.329266.778 43.2 26.35 16.85 24.179306.794 26.35 16.47 9.88 34.059

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

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

Pressure, kPa Initial Dial Reading

Final Dial Reading

settlement Cum. settlement

66.694 50.21 45.619 4.591 4.591133.389 45.619 42.32 3.299 7.89266.778 42.32 33.345 8.975 16.865333.472 33.345 22.65 10.694 27.56

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.

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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