Semicircular Vault
This vault has been built in the campus of the Auroville Earth Institute. It is used as a precasting shed on the ground floor and as a trainee’s dormitory at the first floor. This semicircular barrel vault had been built also to experiment the optimisation method developed by the Auroville Earth Institute. The vault has been built in 37 days with 4 masons and it presents these features:
• Weight: about 40 tons
• 6 m span, 3 m rise, 11 m long, 36.5 to 7 cm thick
• It has been built free spanning with a combination of horizontal and vertical courses
The condition of safe stability for a barrel semicircular vault of this size requires normally 1.2 m thickness. With our method, the vault has been optimised with a decreasing thickness of only 36.5 cm thickness at the bottom up to 7cm at the top.
 Segmental vault, 10.35m span, 2.25 m rise Built free spanning in 3 weeks |
Note that the vault stability is first calculated without the weight of the waterproofing. The waterproofing of such a vault is done with stabilised earth plaster, which has been researched and developed by the Auroville Earth Institute. The weight of such a waterproofing was around 6 tons and it was spread over the entire vault area. Therefore this load, which was added a few months after completion of the vault, changed the location of the line of thrust in the structure. Therefore, the geometry of the vault was be done in such a way that it is stable with or without load: - When the vault is built, the line of thrust is sometimes at the inside limit of the middle third of the vault. - With the weight of the waterproofing, the line of thrust moves slightly outside in some parts to become limit at the outside of the middle third. |
Starting the horizontal courses
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Laying 3 to 5 mm mortar on the vertical side joint Laying a triangular mortar for the horizontal joint
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Pressing the block on the side
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Pressing the block on the previous course
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The trowel cannot go in the joint if the block is well laid
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Laying the half block outside for the bond pattern
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Filling the joint of the first courses
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Horizontal courses going ahead
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Starting an arch window with a centring used as a guide
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Reversing the centring to build the arch window
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Starting the arch of the window
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Arch of the window being built
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Arch of the window in progress
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Blocks corbelling for the arch of the window
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Building the arch of the window
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Building symmetrically the arch of the window
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Arch of the window near completion
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Corbelling blocks of the window
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Laying the bottom side blocks of the window
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Completing the bottom side of the window
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Window arch completed
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Horizontal courses around the arch window
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Horizontal courses going on above the arch window
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Building symmetrically with horizontal courses till the limit of stability
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Horizontal courses completed
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Limit of stability with horizontal courses
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Starting the vertical courses
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Building vertical courses
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Vertical courses in progress
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Vault near completion
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Competing the vault
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Laying the last blocks of the last course
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Checking the last course
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Vault completed in 37 days
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Vault completed
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Casting the waterproof earth plaster
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