In-situ tests programme


The in-situ test includes:

The tests will be executed according to the principles of European Standards.

The description of the piles used for in-situ tests:

The piles are composed of a steel pipe d133 mm with the 4 mm wall thickness, closed on the bottom. The total length is about 5 m, but only L=4 m of it is pressed into the soil.

In the case of the group of piles, their heads will be connected with a pile cap, according to figure 1.

Fig. 1. Diagram of the pile group arrangement

Loading program

The assumed maximum load value for a single pile is 250 kN. The ultimate vertical test load Fu = 250x1.4 x1.2 = 420 kN (factors of 1.4 and 1.2 are required in EN standards);

The load will be applied gradually, at one-hour intervals until reaching the maximum load. The increment will be 25% of SWL, i.e. 62.5 kN. Then, the load will be decreased gradually again, at 15-minute intervals. This time, the increment will be 50% of SWL, i.e. 125 kN. The loading scheme for the single pile loading test is presented in Fig. 2 and for the group of piles in Fig. 3. and the values are presented in Table 1 and Table 2 respectively.

Fig. 2. Loading program of the single pile test

Table 1 Loading steps for axial compression test for a single pile

StepLoadDuration of step, minTotal duration, min
kNPercentages
162.525%6060
212550%60120
3187.575%60180
4250100%60240
5312.5125%60300
6375150%60360
7437.5175%60420
8500200%60480
9375150%15495
10250100%15510
1112550%15525
1200%15540

Fig. 3. Loading program of the pile group

StepLoad, kNDuration of step, minTotal duration, min
1187.56060
237560120
3562.560180
437515195
5187.515210
637560270
7562.560330
875060390
9937.560450
10112560510
111312.560570
12150060630
13112515645
1475015660
1537515675
16015690

As required in the Standards, the pile head displacements and the applied load will be recorded at least at the following time intervals:

Reaction frame description

A reaction frame is used to transfer the load applied to the tested piles.

The special ballasts are used to anchor the reaction frame as presented in Fig. 4. The ballast provides about 1500 kN of dead load.

The load cell and hydraulic jack system will be installed on the pile top.

Fig. 4. Pile test stand with reaction frame

Test equipment installation

For the axial compression test, the following equipment will be put in place:

Taking into account the number of sensors, the acquisition of the data will be carried out via Data Acquisition System connected to a computer. These transducers allow measuring displacements with an accuracy of at least 0.01mm.