Throughout the entire course of phase 2, solutions will have to be developed to deal with the high temperatures on the one hand and the sand, dust and dune movement on the other.
The temperature gradient is not much higher in Saudi Arabia than in many southern regions of Spain, where the high-speed railway lines had been built following a similar methodology to the one included in the bid for the Haramain High Speed Railway.
In the summer months, Seville, Jaén, Córdoba, Ronda, Los Monegros and Albacete reach peak temperatures similar to those on the Arabian Peninsula, and sometimes even higher. However, one important consideration made the Saudi project more difficult: the extreme thermal fluctuations, with maximum annual temperatures higher than fifty degrees and minimums close to or even lower than ten degrees, which posed a technical and human challenge.
Most of the technical studies were aimed at avoiding the potential effects of sand on the infrastructure, the tracks, the systems and the rolling stock. The risks of the platform being invaded with dune advancement were high, in addition to the contamination of the track superstructure and the rolling stock with the sand and dust carried in the wind.
From the start, the entire route was monitored to detect the zones where the most sand accumulated. Furthermore, the possible impact of sandstorms, which reach heights of up to six kilometres, was exhaustively researched.
Division of the construction into ballast and slab tracks
Slab tracks were installed slab tracks on the 30 kilometres that were the most exposed to this phenomenon, in addition to implementing complementary solutions as well. The construction of slab tracks is essentially designed to make maintenance and cleaning easier. The maintenance includes special devices to collect sand, when needed.
Other studies performed by CEDEX which analysed the behaviour of the ballast when it is contaminated by desert sand in different degrees of silting demonstrated that the elastic behaviour of ballast tracks silted with sand was higher than that of unsilted ballast tracks.
Installation of one-metre prefabricated concrete retaining walls along eighty kilometres
An empirical study complementary to a theoretical study on the behaviour of sand analysed the accumulation of sand on the platform to determine the best sites to install the walls along the route. By building these prefabricated concrete walls, the sand which was not held back by the fence is kept at bay, as the last physical barrier against it.
On the most conflictive stretches with the highest sand accumulation, ditches were dug, sand traps that were covered with rubble to prevent the dunes from reaching the platform. The client had these sand traps built in the previous phase. This measure is also designed to facilitate track maintenance.
Installation of a sand blowing system
Front blowers were installed on the trains to eliminate the sand deposited on the tracks.