Why Are D-Walls Becoming Extremely Popular with Construction Companies in India?

Diaphragm walls for top-down construction and deep basements have now become commonplace in the industry, and among construction companies in India. But how did D-Wall construction (another name for diaphragm walls) become a popular choice with civil engineers who are now confident to build towering superstructures with basements as deep as 5 levels?

Let us begin by understanding what a diaphragm wall is, how it is different from other traditional methods of ground engineering like Piling, and what makes it a desirable choice for deep basement construction.

What is a diaphragm wall?

Reinforced concrete walls built in the ground to provide support to the structure to be built above, and act as walls for the deep basement space to be built later, are known as diaphragm walls. They act as the cut-off walls for the excavated area of the site, provide a strong foundation to the surface and enclose the structure.

Piling – The traditional method of deep foundation construction

Piling is one of the oldest methods of building foundational bases for under-construction structures to transfer and manage the structural load on a deeper level. They are long, cylindrical structures that are made of either concrete, wood or steel.

There are two types of pile foundations used in building strong bases

1. End-bearing piles, that can transmit weight load directly to the deeper, stronger soil or the rock base of the site.

2. Friction piles, which transfers the load of the building to the soil across the full height of the pile, by friction.

Piling, a traditional method, is used when the structure above has heavy, concentrated loads and the spread footing won’t be able to bear the weight. So the building structure needs to bypass this layer and transfer the weight to the stronger base at depth.

While a diaphragm wall is constructed by excavating a narrow trench with a thickness ranging between 300 mm to 1200 mm, as deep as 45 metres underneath. It actually does the exact same job, and moreover, offers to act as a retaining wall for the basement, making the foundation stronger.

Yet, what makes construction companies in India choose diaphragm walls for basements?

Lower steel consumption

The cage walls made for diaphragm wall construction require lesser steel bars compared to constructing and inserting piles into the ground below. And in scenarios of unstable soil on the site, an additional casing is required on the piles, which may add an extra cost to the materials consumed.

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Building Diaphragm Walls for Top-Down Construction & Bottom-Up Construction

Top-down and bottom-up planning methods are two of the most popular approaches used in the construction industry. And building diaphragm walls is one of the most crucial stages of construction in building a deep basement structure using either top-down or bottom-up method.

Heritage Infraspace (India) Pvt Ltd (HIPL) is ranked as one of the best construction companies in India for its deep basement and underground construction services like diaphragm wall construction services in India for both top-down and bottom-up construction methods. Here, we brief you about how construction of the diaphragm wall in dams, metro stations, basement parking, etc. works, on both top-down and bottom-up construction.

What is top down and bottom up construction?

Tall buildings with deep basements and underground constructions like parking lots, underpasses, and subway stations are the two principal types of urban structures for which the top-down technique is applied. The technique has been applied to deep excavation projects where soil movements needed to be kept to a minimum but tieback or anchor installation was not an option. In this way, it is often possible to shorten the entire building period.

Buildings with underground basements are typically created using the bottom-up approach, where substructure and superstructure floors are built one after the other, starting at the lowest level of the basement and working their way up.

Although this traditional approach, often known as the bottom-up approach, is straightforward in both design and construction, it is not practical for large-scale projects with constrained construction time or site conditions.

Diaphragm construction in both bottom up and top down construction

Diaphragm walls help form the perimeter walls of the excavation site and push the surrounding soil back, preventing the excavation site from collapsing. A hydro fraise machine is typically used for diaphragm walls. A special blade attached to the boom arm of this machine allows a bentonite slurry to be pumped down to the cutters, preventing the excavated area for the wall from collapsing.

The cutter descends to the desired level, and the slurry mixture aids in the preservation of the shaft. Rebar cages are then lowered into the shaft to provide reinforcement for the being built wall.

While one wall is being finished by pouring concrete and pumping out the bentonite slurry, the process on the opposite side begins. Depending on the soil quality, it is sometimes possible to build diaphragm walls on both sides at the same time. HIPL has, in the past, achieved this feat, making it one of the trusted construction companies in India. Rebar is lowered into the completed shaft for wall reinforcement once more. Once all of the walls are completed, the excavation site will have a rigid vertical structure to keep the surrounding soil from moving and collapsing into the excavation area.

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