procedure of plate load test

Level the area to be tested with Ottawa sand using a straight edge and ensure test surface is level using a 2 ft. long spirit level.  Use the least quantity of sand required for uniform bearing.  If additional in-situ testing is to be conducted, cover the exposed soil materials to a distance of 6 ft. from the edge of the bearing plate with a tarpaulin or proof paper to prevent moisture loss during the test. Seat the 18 inch bearing plate on the leveled surface and verify that it is level. One way to do this is apply a 50 pound load and then check whether the plate is level. If it is not level, remove the load, turn or work the plate back and forth and then apply the 50 pound load and check the level again. Repeat this process until uniformly level seating of the plate is achieved. Center the remaining plates of smaller diameters concentric with and on top of the bearing plate.  Center the hydraulic jack or the drill rods on the smallest diameter plate.  Place the load cell between the hydraulic jack and the loading device.  In the case of drill rigs, the top load cell is attached to a short rod connected to the drill head and the bottom of load cell is attached to a longer rod that directly applies the load to the plate assembly. Mount the LVDT’s onto the deflection beam.  Place the LVDT’s so that the stems rest on the bearing plate not more than ¾ inches from the outer plate edge spaced 180 degrees apart.  Ensure the deflection beam is level and the LVDT’s have sufficient travel length to accommodate a minimum deflection of 1.5 inch. Extreme care must be exercised in order to avoid touching or bumping into the deflection beam while the test is in progress. Connect the cables for LVDT’s and load cell to the data acquisition system.  Also connect the data acquisition system to the lap top Computer.  Connect lap top Computer and data acquisition system to the power supply system. Confirm all electronic components are working, drill rig is level and load application system is plumb. Seating Procedure:  Seat the loading system and bearing plate by applying a load of 1,000 pounds.  Maintain the seating load for a minimum period of 2 minutes.    Record the deflections reading from each LVDT for the 1,000 pound seating load and calculate the average deflection. Do not start the test until the deflection from each LVDT does not change by more than 0.001” per 30 seconds. oad Application:  Apply load continuously at a rate of 1,000 lbs. per 15 seconds until a load of 10,000 lbs. is achieved.  Maintain the 10,000 lbs. load for one minute and then start decreasing the load at a rate of 1000 lbs. per minute for the first 2,000 pounds (from 10,000 to 8,000 lbs.) and then increase the rate to 1,000 lbs. per 15 seconds from 8,000 lbs. to 1,000 lbs.  Maintain the 1,000 lbs. load constant for one minute and then repeat the loading sequence for one more cycle. There is no need to maintain the 1,000 pound seating load for 1 minute at the end of the second cycle. Observe the data acquisition system throughout to ensure that all the data is being recorded.  The test is terminated after the third cycle