PURPOSE OF STATIC LOAD TEST
Pile test by axial static load method (Static load test) can be done at the stage: Design exploration and Construciton quality inspection.
The static load test at design exploration stage is carried out before mass pile construction to determine the required data on the intensity, deformation and the relationship between load – displacement of the pile as the basic for designing or adjusting design, selecting appropriate equipment and pile construction technology.
The static load test at the construction quality inspection stage is carried out during construction or after construction of the pile to check the load capacity of the pile according to the design and quality of the pile construction.
METHOD OF STATIC LOAD TEST
The test was carried out by the method of using static load pressed along the pile axis so that under the effect of pressure, the pile penetrates the ground. The load acting on the pile head is made by hydraulic jacks with the reaction system included load frame, anchor or combine both. The data on load, displacement, deformation, … obtained during the test are the basis for analysing and evaluating of load capacity and load – displacement relationship of pile in the ground.
The static load test is only carried out for the pile that have enough time to recover the soil structure damaged during construction or concrete meet the intensity to test in accordance with the design (for bored pile). The rest time from the end of construction to the time of testing is prescribed as follows:
- Minimum 21 days for bored pile;
- Minimum 7 days for other pile.
The largest test load is specified by the design, usually taken as follows:
- For ultimate test pile: Destructive load or 250% to 300% of design load;
- For working test pile: 150% to 200% of design load.
The allowable load capacity of vertical single piles is determined by the limited load bearing capacity divided by the safety factor. Depending on the importance level of the project, ground conditions, testing method and method of determining the limited load bearing capacity, the Design Consultant decides to apply the suitable safety factor for each specific case.
- TCVN 9393:2012 “Piles – Standard test method in site for piles under axial compressive load”.
- ASTM D3689-07 “Standard Test Methods for Deep Foundations Under Static Axial Tensile Load”