Issue 30

A. De Iorio et alii, Frattura ed Integrità Strutturale, 30 (2014) 478-485; DOI: 10.3221/IGF-ESIS.30.58 482 orthogonal to them and parallel to the running plane, until extended flows in the ballast, corresponding to yielding of the ballast at the interface with the sleeper, occurs. Track panels are composed of n. 4 sleepers at least and extracted from a continuous track built according to the prescriptions needed to reproduce in each of them a scenario different from all others. The use of the track panels allows to test several sleepers at the same time reducing the total time of the experimentation. Moreover, the goodness of the results is not affected by this approach since the results, which are referred to a general sleeper belonging to a given scenario, are computed averaging the results of all sleepers of the scenario tested under the same conditions For the chosen series of geometrical configurations of the track and for one ballast material, by means of these tests, the strength offered by the ballast against the longitudinal displacement of the sleeper, crosswise the permanent way, under loading and unloading conditions, is determined. Full-scale tests on railway sections have been carried out according to the following practice: 1. a structure for load-transfer (cluster) is constrained to the track in at least n. 8 points; 2. a tensile load, transversal to the track and parallel to the running plane, is applied on the aforementioned system, until a displacement greater than 30 mm is produced, acquiring both load and displacement values with a sampling rate high enough to plot the load-displacement curve; 3. the contiguous track is loaded, symmetrically to the load axis of the cluster system, by means of a 2 t mass/sleeper; 4. the test load is applied as in point 2 and the load-displacement curve is acquired. To carry out these tests - in addition to, obviously, the hydraulic ram, the load cell, the displacement transducer and the high frequency data acquisition system - the following equipments are needed: - a constraining structure; - block shaped masses, up to a total of 2 t/sleeper, laying on the track with the centre of mass in correspondence of the loading axis of the cluster system; - an interface structure between rail/loading blocks that allows loading and centring of the masses. Figure 2 : Schematic top view of the tested track segment (not in scale). To conduct the full-scale tests in the same place for the different scheduled scenarios, the testing plan on the track schematized in Fig. 2 has been designed. In this figure different colours represent different zones. In particular, the green blocks represent the transition zones between two contiguous scenarios, while the blue one refer to canted track scenarios (only for RFI 230 sleepers). Red and cyan blocks represent scenarios with ballast retaining wall and anchors mounted on ties, respectively, while the brown one represents “classical” scenarios, namely straight track without accessories (such as anchors). T ESTING RIG o implement the testing plan, an area of the Naples Campi Flegrei railway station has been prepared for the experimental activities. From two old tracks two segments having length equal to about 200 m are removed. A new track is rebuilt in place of the old ones, in such a way to match the specifications for the 28 scheduled tests (Fig. 3). The construction details of the testing plant and the procedure adopted to carry out the tests on all the selected scenarios will be published shortly together with the acquired results. In the present paper, some graphs related to the first results acquired during the transverse tests carried out on four of the most common scenarios are reported (see Fig. 4). In particular, the curves depicted in the aforementioned graphs refer to the scenarios reported in the figures with the abbreviations LRS01, LRS04, LRS06, LRS07, which correspond to the following configurations, respectively:  LRS01: n. 4 RFI 230 sleepers, 60 cm ballast shoulder, 30 cm ballast thickness, de-consolidated ballast bed.  LRS04: n. 4 RFI 240 sleepers, 60 cm ballast shoulder, 30 cm ballast thickness, de-consolidated ballast bed.  LRS06: n. 4 RFI 240 sleepers, 60 cm ballast shoulder, 30 cm ballast thickness, DTS consolidated ballast bed, ballast retaining wall.  LRS07: n. 4 RFI 240 sleepers, 60 cm ballast shoulder, 30 cm ballast thickness, DTS consolidated ballast bed. T