Réparation de digues en terre au moyen de parois moulées dans le sol

Restoration of earth dykes with walls cast in the ground

Ingénieur Civil des Ponts et Chaussées Ingénieur en Chef à Solétanche-Entreprise

Résumé

Earth dykes can be reconditioned by replacing the original sealing arrangements with a 'continuous plastic concrete wall' or a 'continuous grout wall'. A 'plastic concrete' wall is formed by excavating a trench with drilling mud for protection and then replacing the mud with special concrete capable of withstanding deformation up to 10% without cracking.

EXAMPLE: Balderhead dyke, United Kingdom (Fig. 1). A 'grout' wall is formed in the same manner with drilling mud, except that the mud is self-hardening, i.e. hardens gradually without settling out, thus making its subsequent replacement by another material unnecessary. As a general rule, every other panel is perforated (see Fig. 2).

EXAMPLE 1 Laguna dyke, Mexico (Fig. 5)-A 50 m breach which formed in 1969 was caused by a basalt lens in an advanced state of decomposition. The dyke was rebuilt with clay, after which a continuous wall with a total surface area of 13,000 m2 and extending down to 21 m depth was formed of grout. No further leakage has been observed in the former breach section.

EXAMPLE 2 Tenango dyke, Mexico (Fig. 5)-Leakage flow on the right bank increasing steadily from year to year required urgent attention. A 500 m wall extending down to limited depth stopped outflows at the foot of the dyke and reduced leakage by half.

EXAMPLE 3 Los Reyes dyke, Mexico (Fig. 6)-Leakage through this small dyke rising to a height of 8 m at the centre and 500 m in length amounted to 221/sec. A groutwall with a total surface area of 5.600 m2 cut leakage down to 21/sec (fig. 7).

EXAMPLE 4 Nexapa dyke, Mexico (Fig. 8) - The danger at this dyke did not come from the leakage rate (24I/sec.), which was acceptable for its size (50 m in height), but from the sediment in the water. In order to control erosion rather than stop leakage, a 9,700 m2 wall was cast in the ground, which reduced leakage to 10.71/sec. and completely stopped the sediment (Fig. 9).