Cambodia | Riverbank Stabilization – Deep Soil Mixing (DSM)

Project Overview

On November 2019, VINCI Construction Grands Projets signed a contract with the Phnom Penh Water Supply Authority to design and build the Bakheng water treatment plant in the northern outskirts of the Cambodian Capital. The first phase of the project covers construction of:

• the first treatment line with a capacity of 195,000 cu. metres per day
• the intake in the Mekong River with a capacity of 390,000 cu. metres per day,
• two 1.4 metre diameter pipelines with a length of 1.5 km to carry water from the Mekong to the treatment plant,
• a 2 metre diameter pipeline with a length of 7.8 km (including a 630 metre river crossing to be built using a micro tunneling machine) to bring drinking water to more than 500,000 inhabitants of the capital city.

This phase is designed to double the plant’s treatment capacity to 390,000 cu. metres per day.

Ground Condition

At the intake site, Riverbank is composed of (from working platform elevation +4,00m MASL)

• 2m of Sand Fill layer
• 10m of very soft fat clay
• 10m of clay
• hard soil layers (hard clay / compacted sand / bedrock)

Menard Solution

To prevent slope failure at the intake site due to:

• High backfilled material along the river embankment
• Soil Erosion coming from Mekong river current

The riverbank has been reinforced using Deep Soil Mixing method.

The place of works being narrow, the DSM works have been performed using a small drilling machine that we modified to perform 400mm Diameter columns.

Depth of treatment to achieve was 19m from working platform level and the incorporation ratio was 25% (spacing of 700mm axis to axis between each DSM column).