french institute of science and technology for transport ... - Ifsttar

3_APPLICATION OF RESEARCH FINDINGS, TIES WITH INDUSTRY AND EXPERT APPRAISALS
A railway in Saudi Arabia
Coping with sand dunes
Wind
Windward side
Brink
Slip face
Horns
Use of riprap cover to
protect a sandy slope.
Sedimentary dynamics of a dune.
74
The international engineering group ISC, which is
led by the Louis Berger Group and includes Canarail
Consultants, Systra and Khatib & Alami, has asked LCPC
Experts to conduct an expert appraisal in the framework
of the North-South Railway Project (NSR) in the An
Nafud desert in Saudi Arabia.
This assignment provided a way, via its subsidiary LCPC
Experts, of applying IFSTTAR’s expertise in soil mechanics, materials
and sedimentary dynamics on a major international project.
The goal was to validate a technique for stabilizing sandy railway
embankments using lateral sand banks as an alternative
to the initially envisaged solution of protecting the slopes from
erosion by covering them with materials that resist erosion such
as riprap or stabilized soil. The appraisal was conducted by a
team from the GER unit at IFSTTAR, by Thierry Dubeucq on
the spot under the leadership of Jean-Pierre Magnan.
The geotechnical studies showed that wide slopes are stable
with the required safety factor with 1V:3H slopes and a minimum
width of 2.5 m from the rail provides sufficient bearing
capacity under railway loads.
Long-term behaviour is nevertheless affected by the transport
of materials by the wind. The orientation of the slopes of dunes
in the Al Nafud desert, with a steep slope on the northern side
and a gentle slope on the southern side is the result of the
prevailing south-westerly winds. The final recommendations
are to construct a moderate 1V:6H slope on the windward
side while a 1V:2H slope is acceptable on the leeward side.
In addition, it is advisable for there to be a flat surface at least
10m wide on either side of the railway track.
@ CONTACTS
francois.depardon@lcpc-experts.fr
thierry.dubreucq@ifsttar.fr
10 meters
10 meters minimum
Prevailing wind
Railway
Slope 1V:6H
Slope 1V:3H
SAND CORE
Slope 1V:3H
Slope 1V:2H
The profile of an embankment that is stable to wind.
ifsttar French Institute of Science and Technology for Transport, Development and Networks