SIMBAT™ is a dynamic pile test that allows the prediction of static load settlement behaviour of bored, cast-in-place and pre-cast driven piles. The prime advantages of dynamic load testing are speed and low cost. Typically, up to 10 piles per day can be tested and preliminary results available the same day. The SIMBAT™ system, proven in recent trials to be superior to other dynamic pile testing systems, comprises the following main components:
- Data collection unit, for capture of strain, acceleration and displacement
- Site computer
- Optical theodolite to measure dynamic displacement of pile
- Accelerometers and strain gauges
- Software for signal acquisition and data processing
The system is based on wave propagation in the pile. The pile is struck with a drop hammer, the mass of which depends on the pile diameter. Strain gauges, bonded to the side of the pile measure strain under the impact. This is then converted to force from a knowledge of the pile section and modulus. The output from the accelerometers is integrated to give velocity .
The acquisition unit is lightweight, portable and waterproof. It can operate up to 2 days on a single charge and can store over 700 results. Basic processing of data can be carried out on site including determination of the dynamic/total force and permanent settlement for each blow. Transfer of data to a PC can be done concurrently with testing on site or later, in the office.
High Speed Theodolite
During many years of site experience, Testconsult have found that a direct measure of pile deflection during impact is essential for the correct interpretation of data. It is only by making such measurements that the pile top velocity can be correctly inferred from the acceleration data. It also gives a second and totally independent check on the magnitude of the pile movement during the impact.
The Simbat system includes a high speed laser guided, digital, optical theodolite that measures the whole of the deflection cycle of the pile during impact as well as the permanent deflection caused by the blow. The resolution is 0.14mm at a distance of 5m from the pile.
The processing and reporting software is inevitably quite complex and detailed. It has, however, been designed to be clear, user friendly and powerful. The main functions are:
- Creation of a table of files for each pile
- Correction of acceleration data using the theodolite displacement
- Separation of forces to give the dynamic or total reaction of the pile, Rdy, for each blow
- Determination of the dynamic/static correction and plotting of predicted load/settlement graph
- Computer modelling to verify data and to separate shaft and end bearing resistance
The system is applicable to virtually all pile types, ranging from micro-piles up to 2m diameter bored cast-in-place drilled shafts. The only real limitation is the size of drop mass that can be transported and manipulated on site. The largest unit tested to date is a 30,000KN test in Taiwan, using a 30T drop weight.