GENERAL REQUIREMENTS APPLICABLE TO ALL TYPES OF TESTS (STATIC):
A pile test is carried out on a single pile or a group of piles as required. In the case of pile groups, caps shall be provided such that the required conditions of actual use are fulfilled.
Generally, the load application and deflection measurement should be made at the pile top.
Vertical Load Test:
In this type of test, compression (vertically downward) load is applied to the pile top by means of a hydraulic jack against rolled steel joist or suitable load frame with adequate kentledge or reaction piles and the settlement is recorded by suitably positioned dial gauges/LVDT.
The loading should be applied in increments of about 20 percent of the estimated safe load for all static tests. All settlement criteria for permissible limits should be as per IS 2911 Part IV (latest revision shall be preferred)
Pullout Load test:
Pull out tests are where the hydraulic jack is made to rest on rolled steel joist(s) resting on two supports on the ground. The jack reacts against a frame attached to the top of the test pile in such a way that when the jack is operated, the pile gets pulled up and the reaction is transferred to the ground through the supports
Lateral load test:
This test is carried out by introducing a hydraulic jack with a gauge between two piles or pile groups under test or the reaction may be suitably obtained otherwise. If it is conducted by jack located between two piles or groups, the full load imposed by the jack shall be taken as the lateral resistance of each pile or group.
The corresponding Displacements shall be read by using two dial gauges or LVDTs.
Pile Integrity Test:
The pile integrity testing is a qualitative evolution of the physical dimensions, continuity of a pile, and consistency of the pile material and more popular and acceptable nowadays as it is basic, quick and also inexpensive. A large number of piles may be quickly tested at a construction site with a low strain method.
The procedure for determining the integrity of the individual, pile length, vertical or inclined pile by measuring and analyzing the velocity (required) and force (optional) response of the pile induced by a (handheld hammer or another similar type) impact device applied axially to the pile normally at the pile head.
Standard test Method for Low Strain Integrity Testing of Piles is as per ASTM Designation D 5882-96.
High Strain Dynamic Pile Load Test:
The High Strain Dynamic load test is similar to the Static load test which evaluates pile load-bearing capacity. The test procedure is standardized according to ASTM D4945 and also forms part of various specifications and code provisions worldwide. The method is convenient, reliable and helps to evaluate pile capacity and integrity in a short time and one or more piles can be tested per day.
The testing is conducted using Pile Driving Analyzer (PDA) Make: PDI, USA, by obtaining and analyzing records of force and velocity under drop-weight impacts. The field results are further analyzed with a signal matching technique (CAse Pile Wave Analysis Program – CAPWAP) to refine the soil parameter assumptions. The output from the test result can be summarized as below:
- The static capacity of the pile at the time of testing
- Simulated static load test curve
- Total skin friction and end bearing of the pile
- Skin friction distribution along the length of the pile
- Compressive stresses developed in the pile during testing
- Displacement of the pile
- The integrity of the pile shaft