A load settlement curve for point bearing pile is shown in Fig.3.
Load Measurement – The load is measured by any one of the following equipment
- Burdon Gauge
- Proving Ring
- Load Cell
Settlement Measurement – The settlement is measured either by a dial gauge or by a leveling instrument.
Ultimate Load – The failure load is taken as either of the followings.
- 2/3rd of final load casing 12 mm settlement
- ½ load causing a total settlement of 10 % of pile diameter for straight piles or 7.5 % of base diameter for a belled pile.
Constant Rate of Penetration Test – This test is most suitable for friction pile. In this test, the well defined failure load is obtained and the method is very quick. However, this method does not provide elastic settlement at working load.
Method of Testing – In this method, the pile is jacked continuously into soil at a constant rate till failure takes place. The jacking rate in clay is 0.75 mm/min and a small movement required for failure. In sands, the jacking rate is 5 mm/min and a large movement required for failure.
Failure – The failure is defined as follows.
- Load at which pile continues to move downwards without any further loading or
- Load at which settlement is 10 % of pile diameter
The typical load settlement curves are shown in fig.4 below.