Bi-directional static load testing (BDSLT) for piles is the most economical & reliable method for performing loads test and optimization process. Its major advantage is non-requirement of heavy beams and dead loads for the reaction load. In this method the skin and bearing reaction is being utilized as the reaction load, thus a major mobilization and demobilization cost can be eliminated.
Further Advantages of BDSLT are explained below:
A. Unlimited Test Load
For pile testing of large load, BDSLT pile test has unmatchable advantages With an embedded Load cell, any desired load force may be applied to fully mobilize the piles for testing.
B. Improved Safety
No reaction system is required as for other static load test. No use of large quantities of girder beams and concrete blocks which could topple if the base is not well prepared.
C. Limited Access and Work Area
BDSLT pile test can be performed next to existing buildings, under overpasses, highway median strips and offshore, with much less space required compared to other static load test.
D. Piles with Deep Cut Off Levels
For basement piles, test pile can be performed below ground, eliminating the pile extension to ground level.
E. Test for Working Piles
With post-test grouting techniques, testing of working piles can also be done.
F. Time Saving
Compared to static load test with test blocks, there is considerable time saving as no pile built up or strip down is necessary. And testing is able to commence at a shorter period of time after installation.
Bi-directional static loading test does apply for statically testing a vertical compression pile using a load cell, in compression and tension. The aim of this technique is to measure the responses to load in the test pile in terms of deflections and relative strain responses throughout the pile length. Such pile shall be subjected to a standard ML (maintained load) static load testing procedure and shall be instrumented with vibrating wire strain gages to ensure that the load distribution along the pile lengths could be monitored during the test. This method statement should be read in conjunction with the loading test procedure as given in ASTM D8169.
We use the super-cell state of the art technology from China, having the following features and advantages as compared to other conventional BDSLT load cells:
(1) The super-cell assembly is light weight enabling it to be more easily handled on site. It can be readily secured inside the rebar cage without the use of bearing plates.
(2) The Super-Cell design utilizes a much greater cross-sectional area of the pile enabling higher loads to be applied using lower hydraulic pressures.
(3) The Super-Cell design incorporates cone-shape flow guides which help to remove any risk of laitance build-up, they also improve the concrete flow at the cell location, between the lower and upper section of the pile.
(4) Super-cell design is fabricated entirely from steel, it’s of an all-welded hermetically sealed construction where the cell’s increase in height is provided by expandable steel bellows. This feature removes the large sliding seals used by other BDSL methods and leads to improved reliability of the fully sealed Super-Cell.
(5) The Super-cell has a calculated gap. Once grouted, the tested piles can be used as production piles.