Monitoring of railway structures HSL BPL with bituminous layer

Abstract

The phenomena of packing and wear of the ballast, under dynamic stresses lead to high frequencies and high maintenance costs. It has been demonstrated that the settlements in the ballast were linked to the high accelerations produced in this layer by the passage of high-speed trains. The solution with bituminous underlay was used since the 1980s in several countries like the United States, Italy, Spain, especially on high-traffic and high-speed lines (HSL). In France, the interest in this technique is recent. Following the satisfactory behavior of the East European HSL, a layer of asphalt concrete was made under the ballast layer on a high scale lane, the Bretagne-Pays de la Loire (BPL) fast lane. It is intended, among other things, to reduce the amplitude of the accelerations produced at the passage of the HST.
The HSL BPL has 105 km of innovative track with an asphalt concrete (GB) sublayer under the ballast, and 77 km with a granular under layer. In order to study the dynamic responses of these different structures and to understand the effect of the different layers on the dynamic response, four sections were instrumented (3 with asphalt concrete, and one on a standard granular structure) using, among others, accelerometers, strain gauges, temperature probes, etc. More than 100 sensors have been installed on the structure in different positions and depths. The acquisition of the data is made during the speed up test phase under controlled conditions with the same train passing with speeds going up from 160 to 352 Km/h. In a later phase, measurements of all the sensors will be treated under actual traffic. The BPL lane is subjected to commercial traffic since July 2017.
The main idea of the project and the expected results for the first phase are to analyze the measurements in the database created and determine the responses of the different sections and the variations of the various parameters measured: Vertical displacements, accelerations at different levels, horizontal deformations in the bituminous layer, etc.
In this paper, a description of the railway track “Bretagne pays De la Loire”, the instrumentation of the different sections and the acquisition system are detailed. The processing and treatment method used for the registered data is explained. The variation of the speed of the trains is also expected to be carried out in this paper to evaluate the behavior of the structures in section 4 with bituminous underlayment in terms of vertical acceleration.