Civil Engineering Reference
In-Depth Information
FIGURE 13.20
Pile-driving equipment. A prestressed concrete
pile is in the process of being hoisted into position.
should be in line with the proposed grade beam location. The structural engineer will need
to redesign the grade beam for its longer span.
Pile Load Tests.
The best method to evaluate the load capacity of a pile is to use a pile load
test. A pile load test takes a considerable amount of time and effort to properly set up. Thus
only one or two load tests are usually recommended for a particular site. The pile load tests
should be located at the most critical area of the site, such as where the bearing strata are
deepest or weakest. The first step is to install the piles. In Fig. 13.24, the small arrows point
to the prestressed concrete piles, which have been installed and are founded on the bearing
strata. The next step is to install the anchor piles, which are used to hold the reaction frame
in place and provide resistance to the load applied to the test piles. The most common type
of pile load test is the simple compression load test (i.e., see “Standard Test Method for Piles
under Static Axial Compressive Load,” ASTM D 1143). A schematic setup for this test
is shown in Fig. 13.25 and includes the test pile, anchor piles, test beam, hydraulic jack,
load cell, and dial gauges. Figure 13.26 shows an actual load test where the reaction frame
has been installed on top of the anchor piles and the hydraulic loading jack is in place. A load
cell is used to measure the force applied to the top of the pile. Dial gauges, such as shown in
Fig. 13.27, are used to record the vertical displacement of the piles during testing.
