The sonic test
Sonic tests allow us to ascertain piles’ length and integrity. If the piles have any defects, the test reveals how deep and serious they are. The sonic test does not demand any special preparation, and is carried out on a clean pile. Its cost isn’t high when compared with the other possibilities (ultra-sonic tests and core drilling). It takes a relatively short while and produces results speedily. This test is nowadays considered mandatory by most soil consultants, constructors, engineers and supervisors of all construction types.
The test uses a plastic hammer to hit the pile and transmit a wave to its base. On its way back, the wave is picked up by a sensor, and this allows the test equipment to carry out a graphic analysis into the pile’s depth and integrity. The test can be administered 5-7 days (or more) after pouring – until that time, all iron or mold work should be avoided.
The sonic test’s precision is informed by several factors. The more accurate their readings, the less there is a chance of deviation. Among these are a pile’s depth, the concrete’s age and kind, the soil’s profile and any special occurrences during drilling and pouring. However, the data changes with each pile tested and hence a ±10% deviation in gauging depth is figured in. The test does not yield any information about a pile’s endurance, and supplies only limited information about the quality of the concrete.
To arrive at the most precise and effective results, the top of the pile must be chiseled until the concrete is smooth, crack-free and clean of chiseling debris such as Bentonite, as well. Testing a pile not properly prepared might result in interpreting mistakes.
The returning wave is influenced by changes in a pile’s cross-section and friction along its mantle. These two elements can be separated in the process of interpretation only if there is enough data about the soil profile and a sufficient number of piles to test. Moving along the length of the pile, the wave loses energy as a function of friction along the mantle. In certain rocks and high- to extremely-high-density soils, an unclear return of the wave back from the end of the pile is a possibility. These cases can occur when the relation of a pile’s length to its diameter is between 20 and 40 (the relation depending on amount of friction).
And since a serious defect or non-contiguity will result in a wave’s full return, a sonic test will not yield clear data concerning the state of a pile underneath these defects. The difference between a major defect and a fissure in a pile’s cross-section is likewise hard to detect.
Q-Basing administers the sonic test using Piletest.com’s PET (Pile Echo Tester) technology.