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2012 Rapid Load Testing instead of High Strain Dynamic Testing

StatRapid Device 8MNThe Dutch CUR commission adopted the Rapid Load Testing technique (over High Strain Dynamic Testing) as the results are consistent and virtually independent of the person analysing the test data when the data are analysed with the Unloading Point Method (UPM).

 

In response to market demand for Rapid Load testing the company Cape-Holland (www.cape-holland.com) has started to manufacture Rapid Load Testing devices (the so-called StatRapid) based on dropping a mass on a soft cushioning system. StatRapid systems are indicated by the maximum rapid load they can achieve. For example  StatRapid 8MN device can achieve rapid loads ranging from 0.2MN till 8 MN. Higher and lower capacity devices can be manufactured. 

An StatRapid 8MN system consists of a lifting and guidance frame, a modular drop mass (allowing for a mass up to 40 tonnes), a catch mechanism and a modular soft spring system. The duration of the load and the maximum load can be adjusted by varying the drop mass weight, the spring stiffness and the lifting height. The system is hydraulically operated and has sensors for a proper vertical and stable position. It should be noted that the dead weight of the drop mass can also be used for the first (static) loading cycle.

The catch mechanism catches the drop mass after bouncing up from the springs. This prevents unwanted rebounds and allows for successive cyclic testing  with increasing loads similar to static load cycling testing.  In accordance with the CUR and ASTM standards the load, displacement and acceleration are measured near the pile top and then recorded. The load is measured with load cells(s), the displacement with an optical system (Reyca) and the acceleration with a servo accelerometer.

The required load duration for rapid load testing depends on the pile length. The modular set up allows for the tuning of the StatRapid system for piles with different lengths before going to site. With the Allnamics-RLT simulation program the set-up can be checked to satisfy the RLT condition.

  The PDR, a pile testing monitoring system and the belonging monitoring and analysis software developed by Allnamics partners, allow the reporting of the  Rapid Load Test results according the ASTM D7383-10 standard and CUR 230 Guideline.

 

In addition a pile testing monitoring system developed by Allnamics allows the monitoring of the required signals. This same system, the PDR  can also be used for pile driving analysis (PDA), high strain dynamic testing or dynamic load testing (DLT) in addition to rapid load testing (RLT). A separate system called Reyca has been developed to measure the pile top displacement during a rapid load test. The PDR can be connected to a PC notebook/computer by Ethernet cable or Wi-Fi. A typical StatRapid pile test result and its analysis results according to the Dutch guideline is presented in the figures.