Vertical drainage can be used to accelerate the consolidation of impervious soils. Vertical drains are flat or round flexible plastic tubes. MENARD has developed its own range of drain installation equipment to cope with a wide variety of subsoil conditions. The picture below shows a static 45 m cable leader machine which can be equipped with a vibrator.

Sand or granular columns may also be used to provide vertical drainage, depending on the type and nature of the soil.
Commonly, a temporary embankment is used in conjunction with vertical drainage to pre-load th ground in order to reach a total primary consolidation and a guarantee of several decades concerning secondary consolidation.

The MENARD VACUUM consolidation process is a much more effective preloading system which saves time and materials. When these methods are used it is usual to install instrumentation to monitor the consolidation in real time.

RABAT/TANGER Motorway (MAROC)

The route planned for the RABAT-TANGER motorway constructed on behalf of the Autoroutes du Maroc company crosses the Loukkos wadi where it is about 100 m wide. The wadi is crossed by a bridge, access to the bridge is via embankments up to 5 m high which are to be constructed over a depth of 30 m of compressible soil. In order to solve the problem of residual settlements beneath the embankments MENARD has installed 630,000 m of vertical drains to speed settlement and stabilize the embankment foundation.
Instrumentation has been installed over the whole site to provide continuous monitoring of the soil's behavior. MENARD was responsible for this monitoring in order to allow the height of the embankment to be raised near the wadi as quickly as possible while ensuring the stability of the embankment.