How does one go about building an underground structure without concrete?

Question

I was reading an article that was linked on another site I frequent on "India's forgotten stepwells", which are basically elaborate wells with stairs to go down to the water level, sometimes 10 m or so below surface (maybe more, looking at the pictures). Some of these are whole temples underground, very impressive.

So I was wondering how one would go about building such a thing, or rather how they would have gone about it 1000 years ago. Would you just dig a very big, deep hole, build a structure inside, then fill the sides (can't imagine this)? Is there a way to start at the surface, then work yourself down, basically building layers under existing ones?

Similarly, how does/did one go about a brick well? Dig a deep hole, hope it doesn't collapse on top of you, start with brick once you hit the bottom during dry season? Or is there a way to work yourself down there? And does it make a difference nowadays; I mean are there new methods now with modern materials that let you do things they couldn't do 1000, 500 or 100 years ago?

Answer 1

General:

The assumption that concrete was not available is probably correct but not certain. The Colosseum is largely concrete and the Pantheon (still) has the largest unreinforced concrete dome in the world. Wikipedia advises that concrete of some form was known in 6000 BC and that eg Bedouins used it to built underground cisterns in desert areas from around 700 BC. But, I could find no clear indication that it was used in India until relatively modern times.

The Taj Mahal was built over ~ 20 years from 1632 and Saint Paul's Cathedral in London was built a few decades later. Both are (as far as my non civil engineering eye and brain can tell - having looked at both) approximately equivalent accomplishments. I'd have expected something like cement would be a given in both cases. Maybe not.

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Stepwells:

A web search showed (as you also will have discovered) that there is a vast amount ABOUT the wells available but almost none of it deals with construction methods.

Better than most, but not really good enough, is Cyark's Rani ki Vav An Ancient, Royal Stepwell which on that page gives an overview and on associated pages gives immense detail in cross section diagrams, photos, sketches and more.

3D interactive 'fly through' - impressive and fun - shows you WHAT was achieved but does not answer the 'how'.

All resources on one pahge, and you can subset them using the menu at top into 3D Point Clouds, Drawings, Panoramas, Perspectives, Photographs and Videos. Some of the detailed material requires an account but there is much there that is accessoible. Hopefully this approaches your "Stepwells 101" level.

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What appears to be very close to what you want is described in a course outline, but without the detail in a school student's course outline. It's possible that the lecturer MAY make the course material avaialable. Course outline here - more questions than answers.

Form, Function, and Spirituality at Rani ki Vav

They say - After completing this lesson, the student will be able to:

• describe well engineering and functionality with regard to several different well typologies.

• recall principles of weight bearing and the effect of water on various materials.

• explain the history and construction of Rani ki Vav, the symbology of its iconography, and the source of its water.

• relate the importance of water for survival to the prominent role water plays in religions across the globe.

• compare the ceremonial aspects of carving across sites around the world, illustrating that the amount of effort placed into the creation of buildings may indicate something beyond its functionality.

• reconstruct a scaled well or stepwell out of new material and engage the scientific method in testing its strengths and weaknesses.

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Rani ki vav:

Unesco

Archaeological survey of India

Various:

Minimal stepwell mention, but looks useful - Infinity Foundation sponsored new book project titled: "Channeling Nature: Hydraulics, Traditional Knowledge Systems, And Water Resource Management in India – A Historical Perspective" by Rima Hooja, PhD

Ancient origins

Wikipedia - Stepwell

"India's invitation"

Britannica

Your superb reference

Lowish:

Low

UCLA

Atlas obscura

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Somewhat related only:

Cyark home page - just sit and watch

Geghard, Armenia

Answer 2

Sinking a brick shaft is fairly easy technically, but the skills may have been lost a few years back.

1. You dig a hole.
2. Line the hole with mortared bricks from the inside.
3. Drive pins into the sides below the brickwork so that it corbels over the pins and is supported.
4. Dig out under the brickwork, extending the hole downwards somewhat.
5. Build more lining.
6. Remove pins and repeat ...

It's how mine shafts going down 1000 feet were sunk. I don't know your well's ground conditions, but I can speculate that if they where conducive to some self support, the brickwork could be replaced with un mortared stonework.

Like this, but here soft ground conditions (Bolton, England) means that an iron ring is used instead of pins. And the ring is supported from the surface:-

It seems we've forgotten so much stuff these days and have to rely on complex technology or a Dremel. Shame really.

Answer 3

Considering your question about ancient wells, as Russell McMahon has indicated, there does not appear to be much information on ancient construction techniques of this type. So lets conduct a thought experiment.

Currently, modern drilled caisson foundations, say, for example, 3 m diameter shafts to depths of 30 m, may often pass through water bearing strata to reach sound bearing strata, that is either rock or highly consolidated, dense soils.

Typically this is accomplished by advancing a steel casing as the drilling head extends to greater depths. Typically the shaft is filled with a dense drilling mud (sodium bentonite clay slurry) to counterbalance hydrostatic pressures (to stop water from blowing soil back in through the base of the excavation).

Returning to antiquity, consider that knowledge of the application of the wheel, lever and arch were well known at that time, and arch construction typically employed braced timber forms that required precision of design and fabrication (this is the entire basis of the load capacity and performance of an arch - its geometrical precision). It is not beyond the imagination to expect that the interlocking stone or masonry shaft could be constructed, one course at the time, as the shaft was dug by hand. Borrowing ideas from arch construction (applied horizontally rather than vertically), timber bracing/forms could be used to ensure the precision and integrity of the shaft until completed.

As the shaft neared its destination (water bearing strata), if necessary rubble or gravel (or masonry elements for that matter) could be used as ballast to counterbalance the effects of hydrostatic pressure on soils at the bottom. This ballast could be removed or left behind, as the situation required, upon completion.