HIPL X L&T: A Journey of Pace & Modernity

Built by the top civil construction companies in India, modern superstructures depend on sophisticated and calculated geotechnical solutions such as diaphragm walls and anchoring, providing them with a dependable and long-lasting foundation.

After all, the quality truly pays off! This is a shared belief between Heritage Infraspace (India) Pvt. Ltd. (HIPL) and Larsen & Toubro (L&T) Construction, two leading names among the construction companies in India.

This has paved the way for a journey of modernity and paced engineering. Discover all details about it below.

The Client: L&T Construction, making India futureproof

With operations in over 50 countries, L&T Construction has held a customer-focused and sustainability-conscious approach towards civil engineering for over eight decades.

With expertise in infraspace engineering, L&T Construction provides excellence with its forward and well-researched infrastructure solutions. As a leading construction company in India, they firmly believe in sustainable and top-quality results to make the construction of our civilization forever marvellous.

Mumbai Coastal Road Project, the Central Secretariat Integrated Buildings, Ahmedabad Metro, the Statue of Unity, and the Baha’i Temple are a few gems of the L&T Construction.

The Projects:

With L&T Construction, HIPL took charge of diaphragm wall construction for deep basements and underground metro railway station projects and provided piling and anchoring solutions for the following projects:

Metro Projects:

Ahmedabad Metro

Connecting the four corners of Ahmedabad, this metro corridor runs for over 40.03 km in length, out of which approximately 6.5 km lies under the surface. It took HIPL around 4-5 months for its diaphragm wall construction.

Kochi Metro

With over 300 piles stretching from Aluva to Kalamaserry, the construction work for the Kochi metro project began in 2019. And within a tenure of 6 months, HIPL successfully completed the piling process. A 1000/1200 MM diameter pile was placed in the soil for the project.

DMRC Chattarpur station and Chattarpur Mandir Metro

Under the latest venture with L&T Construction, the DMRC Chattarpur station and Chattarpur Mandir metro are under construction in Delhi.

Deep basement projects:

The Central Vista

Being one of the best diaphragm wall construction companies in India, HIPL was awarded the Central Vista project under L&T Limited.

Where a 600 to 800 mm concrete diaphragm wall that stretched over 1500 running metres, was constructed within a time frame of 6 months. The solutions provided also involve soil anchoring at a differentiation of 2.5 metres.

The Challenges:

The key challenges encountered by the HIPL team while working on these projects were diverse and constantly changing. There is a handful of them listed under the following heads:

Obstacles at the metro construction site:

The biggest concern for any metro infrastructure company in India is that these metro lines are to be built amidst bustling areas of a city. This further impacts smart construction solutions with:

Disturbing traffic

Areas with a high influx of traffic and frequent vehicular commotion are not the best-suited construction site for diaphragm walls, particularly for metros. With regular disturbances from traffic, the transport of raw materials and machinery can be affected.

Likewise securing the entire stretch of the excavation site and diverting the traffic was important.

Underground existing structures

The chances of encountering existing underground structures rise exponentially in the interior parts of a city. Such was the case for the above-mentioned metro projects with L&T.

This range from existing diaphragm walls to drainage pipes. Such a situation calls for smart construction solutions. In most cases, the excavated structure could either be removed or strategically broken down as and when required. While others call for engineering expertise to develop an adjourning diaphragm wall along with the existing structure.

Water leakage threats

Drainage might seem trivial but is among the top challenges faced by engineers of every infrastructure company in India. Since any kind of water leakage can harm the diaphragm wall and the metro structure in the long term, ensuring that the construction is fully waterproof was essential.

Overhead cables

For places like the national capital Delhi, overhead cables turn out to be a major challenge for HIPL. Along with being in the way of the construction and causing delays, they pose the additional threat of accidents.

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Are Diaphragm Walls And Retaining Walls Different?

A common question our civil engineers encounter in conversations with people within and related to the construction industry, is the difference between a retaining wall and a diaphragm wall.

The idea of retaining walls is simple, a solid wall used to restrain masses of soil from falling off a slope or the edge of an excavation. And when it comes to deep basement construction, it is required to resist the lateral pressure of the soil from crashing into the excavated cavity where people and machinery are building the underground space.

While diaphragm retaining wall construction helps build multi-level basements for residential and commercial projects and underground metro and subway stations.

Let’s dig deeper to understand the difference better.

How do Retaining Walls work?

A retaining wall is used to retain the backfill against excavation. The whole excavation is made for the structure and then the retaining wall is constructed. There are 4 common types of retaining walls that do this.

1.) Gravity retaining walls: Gravity retaining walls prevent sliding and toppling of soil and resist the lateral pressure behind them with the use of gravitational force of their own weight. They are usually built of bricks, concrete blocks or cast-in-situ concrete with a wider base and sloped faces.

2.) Cantilever retaining walls: Cantilever walls are L-shaped or T-shaped foundational walls, built with the footing or base slab beneath the backfill. The vertical pressure from the soil is transferred onto the base of the structure and the wall in the centre, forming the T shape and preventing the soil from crashing into the excavated area.

3.) Embedded retaining walls: Extending deeper than the site excavation, the embedded retaining walls take advantage, at least partly, of counteracting the active earth pressure being exerted on the wall above. They are used to construct near-surface underground structures, such as basements, car parks and metro stations.

4.) Reinforced retaining walls: Reinforced soil retaining walls, sometimes referred to as mechanically stabilised earth walls, are constructed using layers of geo-grid to reinforce the soil into a stabilised mass. This increases the bearing capacity of the wall, along with its resistance to differential settlement.

Are retaining walls and diaphragm wall construction the same?

A diaphragm wall is a type of retaining wall. As a matter of fact, a diaphragm wall construction can be a type of cantilever, embedded, or even a reinforced soil retaining wall.

Diaphragm walls are 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 on.

They act as the cut-off walls for the excavated area of the site, providing a strong foundation to the surface and enclosing the structure while resisting the soil pressure from the other side.

In construction sites with collapsible soil or where the feasibility of deep excavations is as good as none, developers must opt to build a diaphragm wall. Diaphragm walls can be constructed up to the required depth and then excavation can be started so that soil would not collapse.

So basically, what diaphragm walls do is ‘retain’ the soil from collapsing, while the required excavation and construction of deep basements take place.

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