Everything Starts With the Soil in Diaphragm Wall Construction

Understanding soil is a crucial part of building a diaphragm wall for deep basements. Civil engineers from some of the best construction companies in India will agree that for a project to proceed, it is vital to ensure that the soil on the construction site can take the load, withstand the pressure with time and not degrade the construction material used in the structure.

As one of the top civil construction companies in India, we have set standards in constructing diaphragm walls in almost all types of soil across the country and worldwide. Read on to know what our civil engineers look for in the ground they work with and the actions they take to ensure a strong foundation is laid for the diaphragm walls to last for the longest time.

Types of soil

A large country like India has different types of soil in different regions as per its climatic conditions and its exposure to various environmental elements like heat, snow, salinity, etc. Being among the leading construction companies in India and having worked all over the country, our engineers have come to define the types of soil below and how they affect deep basement construction:

– Sandy: In the north-western belt of the country, in states like Gujarat, Rajasthan and Haryana, the top soil strata have more sand in them and are drier because of the excessive exposure to heat. While excavating through them is easier, what’s challenging is ensuring the soil doesn’t collapse.

– Marshy: The coastal belt of India that stretches down south from Maharashtra to Andhra Pradesh and West Bengal, has a much marshier soil thanks to the high water table in the ground, proximity to the sea and the humid climate the regions have. The construction of the diaphragm wall in such soil conditions also involves shoring activities.

– Sand with Silt: The central parts of the country, like Madhya Pradesh, Uttar Pradesh, Delhi and some parts of Gujarat have sandy soil, mixed with silt deposits. These occur from the various rivers flowing through these regions. Ahmedabad is one such city.

– Rocky/Gravel: The central and far northern regions of the country with mountain peaks have rocky strata with lots of gravel in their soil. Working in such conditions is a challenge, as engineers have to involve trench cutters to penetrate the layers to excavate further.

Challenges faced by the best construction companies in India

It is never a walk in the park when it comes to constructing a diaphragm wall for deep basements in a country like India, where the soil type changes with every state, cities are densely populated and the soil quality resultantly going down.

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Bentonite to Polymer Slurry, the Sustainable Route to Building Reinforced Concrete Diaphragm Walls

Bentonite has been a crucial construction element in building reinforced concrete diaphragm walls for deep basement structures. But over the years, civil construction companies have started using polymer in their excavation fluids and slurry.

Read on to understand the importance of both the materials in constructing concrete diaphragm walls, the differences between them, and how polymer is growing as a more sustainable option in excavation activity while bentonite remains the foolproof back plan for civil engineers.

What are Bentonite and Polymer Slurries?

Bentonite clay is formed by the alteration and weathering of volcanic ash and is abundant in the clay mineral montmorillonite, which swells when mixed with water and possesses exchangeable irons on the surface that produce thixotropic suspensions. Typically mined in Rajasthan India, it is extensively used in diaphragm wall construction as an excavation fluid. Bentonite clay (in powder form) is combined with water in a colloidal mixer where the clay particles bond with one another to form a gel-like texture.

The mixing process continues till the standard quality is achieved for the slurry.

Polymer slurry is prepared with the combination of water and hydrophilic superabsorbent polymers like polyethylene glycol, polyvinyl alcohol, or carboxymethylcellulose to form a thick, viscous mix. These water-soluble polymers have been used to stabilise deep excavations for reinforced concrete diaphragm wall trenches. When compared with conventional bentonite slurries,this engineered fluid is known to offer a variety of advantages including smaller site footprint and lesser environmental impact.

How is a bentonite slurry or polymer slurry prepared?

The slurry is prepared with the aim of attaining maximum hydration of bentonite clay or polymers. Hence, it must be slowly added into the mixing water to ensure all particles are irrigated and do not get lumped. Potable fresh water should be used in the mixing process to obtain the best results. Alongside this a chemical analysis, as listed out by the Indian Standard Code of Practice for Construction of Diaphragm Wall, must be conducted to ascertain the suitability of water. If needed, chemical treatment is given to the water before its usage.

The preparation of the slurry is done either in batches or in a continuous process, depending on the type of equipment used. The components are added in a high shear mixer through a simple venturi-hopper. To assure the dispersion of all the individual particles in the mixing water, the mixing equipment must generate sufficient shear. Once prepared, it is moved to storage tanks, and from there they are supplied to the excavation point, to be filled into the cavity of the soil. This entire process, including the testing is done on-site by the civil construction company assigned to build the diaphragm wall.

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