2.1.1 Influence of the moisture content on the static behavior

To study the influence of the moisture content, plates belonging to each of the groups described above were used. Figure 2 shows the results obtained in the static test on plates with different degrees of humidity. As can be verified, except for the dry plate which breaks when reaching a certain load value, the rest of the plates present a point of inflection. This phenomenon is due to the fact that increasing the moisture content of the plate increases its deformability and, at some moment in the loading process, the inner part of the hole contacts the screw, and then, they collaborate jointly against the displacement of the rail base.

Figure 2. Results of the static tests conducted on plates with different levels of humidity.

As can be seen in all cases, the contact of the plate with the screw is approximately constant, around 4.4 mm, although, as the plate humidity increases, the force decreases, as the plate becomes more and more flexible.
