Importance of Diaphragm Walls in Metros – A Case Study

India’s first metro rail started back in 1984 in Kolkata (then Calcutta), West Bengal . Ever since, India has seen a rapid expansion of metro rail in various cities, with Delhi leading, and other cities catching up like Ahmedabad, Bengaluru, Gurugram, Kanpur, Kochi, Lucknow, Mumbai and now even Agra.

India being a country with densely populated cities, building metro railway lines and stations is nothing short of a challenge. Heritage Infraspace Pvt Limited has assisted and provided metro diaphragm wall construction services to many metro contractors in India. Here, we break down the importance of diaphragm walls in the construction of metro railways, as an interesting case study.

Types of stations built by metro contractors in India

There are majorly two types of metro stations: elevated and underground stations.

An elevated metro railway station or elevated train station is a railway platform alongside the tracks above street level on a viaduct or other elevated structure, usually constructed from steel, cast iron, concrete, or bricks by metro contractors in India.

An underground metro railway station is where the platform is built multiple levels beneath the ground as deep basements. The metro rail tracks run parallel to these stations, with a bustling city above it.

Elevated railways are normally found in urban areas where there would otherwise be multiple level crossings. Usually, the tracks of elevated railways that run on steel viaducts can be seen from street level.

Underground metro stations are generally proposed in older, dense parts of the cities where roads are narrow and sharp turns do not allow elevated rail alignment without major demolitions.

Importance of diaphragm walls for underground metro stations

Diaphragm walls are sturdy underground structures that can act as a permanent structural wall. Diaphragm walls can be installed to deeper depths, which helps in building multi-basement stations.

Compared to construction of a station on an elevated metro corridor, underground metro diaphragm wall construction services require less temporary propping. The top-down construction method can be applied in building an underground metro railway station.

The diaphragm wall is a rigid structure, hence the ground movement induced by basement excavation for underground metro is lesser compared to usage of flexible retaining walls. Diaphragm walls act as a strong guide wall for the launching shaft for metro stations.

Challenges faced by HIPL Ground Team

A major challenge HIPL faces as a commercial construction company in India working on various underground metro projects is accurately/precisely identifying the quality of the soil. With urbanisation, soil quality cannot be determined with a single inspection, and as the excavation takes place, the teams come across various forms of soil, which affects the metro diaphragm wall construction to a great extent.

The other challenges are as below:

Metro construction area sees a lot of activity and hence securing an entire stretch for the excavation work and diverting the traffic is a challenge.

Transportation of various construction materials, utilities, machinery, etc. is a big challenge, as urban areas have constant and heavy flow of vehicular and foot traffic in congested spaces.

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HIPL x Hines: Building Futuristic Superstructures in Gurgaon

Heritage Infraspace Pvt Limited (HIPL) is known as the pioneers of diaphragm wall construction for deep basements in India. As one of the top construction companies in India, HIPL has worked on several residential and commercial projects collaborating with prominent names from the real estate industry. One such commercial complex project is the Adarshini real estate pvt ltd under Hines in Gurgaon.

Here’s a deep-dive into the observations made, challenges faced, and solutions provided during the construction phase of this project.

Adarshini & Hines – The client

Aadarshini Real Estate Developers Private Limited is a wholly-owned subsidiary of DLF Home Developers Limited, a part of the DLF (Delhi Land and Finance) Limited, one of the largest commercial and residential real estate construction companies in India.

Hines is a privately owned global real estate investment, development and management firm, with a presence in 285 cities in 28 countries and $90.3 billion of investment assets under management and more than 114.2 million square feet of assets for which Hines provides third-party property-level services.

Adarshini and Hines combined forces together to build an exceptional and modern commercial space in Gurgaon near the prominent Income Tax complex, to cater to the changing business landscape of India and its growing demand of workspaces that fulfil the requirements of the globally connected enterprises working round the clock.

Projects awarded to HIPL for this project

HIPL was first awarded with a project to build diaphragm walls, conduct anchoring for soil and the requisite excavation activities for the North Parcel in 2020. It took HIPL close to 1 year to complete this project.

Upon completion of the North Parcel, HIPL was awarded a similar project at South Parcel, commissioning them with the construction of diaphragm walls, soil anchoring and excavation.

The excavation activities for diaphragm wall projects are usually commissioned to a third party by the client, but in this case, HIPL was assigned with the excavation activities too, given that we had all the required equipment and manpower to execute it.

This is one of the biggest commercial projects HIPL has worked on. What makes this project unique, is that HIPL engineers used retractable anchors, something which was innovative and executed for the first time on a project of this scale and size.

Challenges in this project

One of the biggest technical challenges faced in this project was the size of the perimeter on which the diaphragm wall was to be built. Apart from that, ramping the soil was also challenging in terms of execution, given the depth of the project.

Supervision in every stage, in every aspect was extremely crucial. The lead engineers were present at the location, guiding, overseeing and ensuring perfection in execution at all the times.

This, because the first leg of the project was being conducted during the monsoons and precautions for the safety of the workers and neighbouring structures were important. One of the most important buildings next to the project site was the Income Tax complex.

Constant rains were a cause of worry. But our engineers and team of workers did everything required as a part of the monsoon precautions on the sides of the perimeter, to ensure all the water drains away and no water gets percolated behind the constructed diaphragm wall.

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