Diaphragm walls are structural concrete walls formed in-situ in deep trench excavations, and are commonly used in projects with deep shafts, multi-level underground car parks, underground railway stations, underpasses, and basements.

A diaphragm retaining wall is often used where there are very deep excavation levels required, where there is limited headroom on site, where site is congested due to its footprint size and proximity to existing buildings, or where a large volume of soil would need to be removed to create battered slopes with sufficient stability.

What Is The Difference Between A Diaphragm Wall And A Traditional Retaining Wall?


The main difference between a diaphragm wall vs. a retaining wall are the ways in which each type of wall is constructed and its intended purpose:

1) Retaining Walls


Most people, even those not directly involved in construction, are familiar with the concept of a retaining wall. After excavation, a retaining wall is designed to resist the pressure of earth or water by harnessing the mass of the wall and buttressing to redirect the horizontal force behind the wall vertically to the ground.

During construction, the excavation is completed first for the main structure or services, followed by the retaining wall structure which is also formed within the excavation. On completion, the excavation is backfilled (on the retaining side) up to the wall structure.

2) Diaphragm Walls


In contrast, a diaphragm wall does not require any excavation behind the wall or beyond where the wall is to be installed, meaning no earth batter is required enabling the wall to be formed closer to the site boundary and allow the excavations to extend to much greater depths. The wall itself does not rely self-weight to resist the earth and water pressures, and instead will require various levels of propping. The diaphragm wall is constructed by a cutting or grabbing tool that forms a deep ‘trench’ to a required design depth. The wall is usually formed under a support fluid to maintain stability of the trench and prevent collapse. Reinforcement is placed before concreting up to platform level. The support fluid is displaced by concreting process, leaving the reinforced concrete diaphragm wall as the finished product. Multi-level propping is then usually installed whilst digging down to the desired depth within the excavation. The design of the diaphragm wall needs to consider the various pressures and loads exerted and resisted by the propping and wall at various stages during construction and up to the final construction stage or permanent state.

Suitable for most types of subsoil, diaphragm walls generate marginal noise and vibration during installation, making them suitable for construction work near to existing buildings. Floor slab connections and recessed formwork can be integrated into diaphragm walls which generally range in thickness’ from 500mm to 1500mm and can be excavated to depths of more than 55m.

Get In Touch With Franki Foundations


At Franki Foundations, we have over a century of experience perfecting deep foundation techniques, with the knowledge and skills to deliver reliable solutions for any project. To find out more, get in touch on 01322 936208 or email sales@frankifoundations.co.uk.

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