The new semiconductor production facility in Tainan Scientific Park, Taiwan, was to be built on soil with low mechanical properties. Since proper functioning of such a facility is possible only if a high stability of foundation is assured it was estimated that approximately 3000 piles were necessary. All the piles had the same dimensions, a diameter of 1.20m and a length of 35 m, and were constructed to have the same mechanical properties.
Aim of monitoring:
The project aimed to test the mechanical performance of the piles. For this purpose, it was decided to perform pushdown, pullout, and flexion full-scale on-site tests. Smartec SOFO sensors were used to monitor the behavior of the piles during the tests. Two sets of piles, the first on the east side and the second on the west side of the facility’s foundations were tested. Each set consisted of three piles and each set was tested to a single influence: compression, traction, or horizontal force. The sensors were installed on rebar cages before the pouring of the concrete. The position of the sensors for each test is presented in Figure 1 and their installation on the rebar cages is in Figure 2.
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The load was applied step-by-step by using hydraulic jacks while respecting the prepared schedule. The intensity of the load was monitored on the scale of the loading set-up. Each step of the load was maintained during the period (length is dependent on load level). After the maximal load is applied, the piles were unloaded, step-by-step again. Important information is obtained from the test and the results are resumed in Figure 3. For example, the distribution of normal forces in a pile and frictional stresses in the soil are presented in Figure 4 for bearing capacity load (480 t) and for the maximum applied load (840 t) for the pushdown test. A zone of soil with poor quality is distinguished in Figure 4.