Determination of Bearing capacity of soil using Plate load test

Name of the Experiment	Determination of Bearing capacity of  soil using Plate load test
Theory
Bearing capacity is the capacity of soil to support the loads applied to the ground. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil.
List of Equipment needed
Bearing Plates: Consist of mild steel 75 cm in diameter and 0.5 to 2.5 cm thickness and few other plates of smaller diameters (usually 60, 45, 30 and 22.5 cm) used as stiffeners. Loading equipment: Consists of a reaction frame and a hydraulic jack. The reaction frame may suitably be loaded to give the needed reaction load on the plate. Settlement Measurement: Three or four dial gauges fixed on the periphery of the bearing plate. The datum frame should be supplied for from the loading area.
Procedure
1. Test pit should be at least 4 times as wide as the plate and to the foundation depth to be placed. 2. The test shall be carried out at the same level of the proposed foundation level or as directed by the Engineer while the same conditions to which the proposed foundation will be subjected should be prepared if possible. 3. At least three (3) test locations are required for calibration on size effect of test plates, and the distance between test locations shall not be less than five (5) times the diameter of the largest plate used in the tests The test surface should be undisturbed, planar and free from any crumbs and loose debris. 4. When the test surface is excavated by machinery, the excavation should be terminated at 200mm to 300mm above the test surface and the test surface should be trimmed manually. 5. To ensure even transference of the test load on to the test surface, the steel plate should be leveled and have full contact with the ground. Sand filling or cement mortar or plaster of Paris could level small uneven ground surface. If the test is carried out below the groundwater level, it is essential to lower the groundwater level by a system of wells or other measures outside and below the test position. 6. The preparation of the test surface may cause an unavoidable change in the ground stress which may result in irreversible changes to the subsoil properties. It is essential that the exposure time of the test surface and the delay between setting up and testing should be minimized. 7. The time lag shall be reported with the test result. Support the loading platforms or bins by cribbing or other suitable means, at points as far removed from the test area, preferably not less than 2.4m. 8. The total load required for the test shall be available at the site before the test is started. The support for the beam with dial gauges or other settlement-recording devices shall not less than 2.4m from the center of the loaded area. 9. Mackintosh Probe Test to be carried out at load test location (center of plate) at testing level before the test for calibration purpose. 10. Loading shall be applied in 3 cycles. The time interval of each stage of loading should not less than 15 minute. Longer time interval is required at certain specified loading stages. The settlement at each stage of loading should be taken at the interval of every 15 minutes before and after each load increment. 11. If the required time interval is more than 60 minutes, the reading shall be taken at every 15 minutes interval. In the load measurement, the test record sheet should include the targeted load schedule, load cell readings (primary measurement) & pressure gauges readings (secondary measurement). 12. The testing contractor shall control the loading using load cell readings to achieve the targeted load in each stage of loading & record the actual readings in the load cell & the pressure gauge simultaneously. 13. Continue each test until a peak load is reached or until the ratio of load increment to settlement increment reaches a minimum, steady magnitude. 14. If sufficient load is available, continue the test until the total settlement reaches at least 10 percent of the plate diameter, unless a well-defined failure load is observed.
Observation and Tabulation
Load Settlement Time escaped 1 2 3
Calculation
Determine the settlement of footing using the following relationship Sf = Sp {[B (Bp + 0.3) ]/[ Bp (B + 0.3) ]}^2 Where, B = width of footing in mm. Bp = width of test plate in mm. Sp= settlement of test plate in mm. Sf = settlement of footing in mm.
Result and Discussion
Bearing capacity of soil ___________________, Settlement of Footing ____________