Foundations with arches
This method saves on materials and cost but needs an innovative structural engineer
Strong and sustainable: The curve profile of the arch foundation being
The fourth in the series, ‘Green Sense’ is trying to inculcate sustainable methods in construction and suggest traditional wisdom and ideas to help people achieve socially responsible triumphs during construction.
Take the case of foundations, there are quite a few vital points that could be adopted from long-established principles…
Did you ever realise that building foundations have contributed to much of our historic knowledge? Surprising, but it is true across the world including Harappa and Mohenjodaro. They live long, being firmly held within the earth. It is the soil beneath which fails leading to the collapse of a building, and not the foundation independently.
Look at the Golconda Fort, with high stone walls perching precariously on the corner of a boulder with no separate foundation dug out by blasting the stones. With load-bearing wall systems, Golconda was possible. But the modern RCC column system demands that we blast the rock and anchor the footings. The financial and ecological implications are heavy. Actually, what we call as foundation is not the layer absorbing the weight. All the dead weight goes into the earth, and understanding the earth condition saves money and time.
A good engineer can design an efficient foundation by mere site observation. If in doubt, soil test should be done and in complicated cases geo-investigations may have to be undertaken.
The trench to be excavated and size of footings would vary with the total load to be transferred to ground and the soil-bearing capacity. With all this background, it is surprising to know that most house owners get no drawings done for the foundation, with the mason doing what he knows. So, the first step is to appoint an innovative structural
If the idea is to transfer load to ground, why not an arch action? We all have seen long railway bridges across rivers with big arches and few pillars, where the arch passes on the weight to pillars. Can there be such arches below the building which pass on the load to fewer points in the ground? In all the older civil text books, there used to be arch foundation details, yet of late, its popularity has drastically reduced. Architect Mohan Rao recently worked with this idea and has once again proven the validity of arch foundation, demanding less materials and cost.
It requires certain calculations about the ground arches, their width, curvature rise, and arch materials. Instead of a full 3’x3′ trench, the excavation itself is done in arch forms, a series of them to cover the full wall length, and each curved mud profile takes a natural arch.
The springing points of arches can also be the pillar points, if needed. With reducing application, arch foundation faces the fear of extinction, despite all its advantages. It’s time we revive it.