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As we have seen, the mockup or test vault is an excellent tool to train masons and to give the confidence of working with the thin-tile construction technique. But even at this scale, the risk of collapse is evident. The structure must be designed for stability in all phases of construction, and further the proper sequence of construction must be followed for a vault to be stable. Since certain states in the construction sequence are less secure than others, if laborers don’t understand how vaults work, the vault may be loaded in an inappropriate way, causing a collapse to occur which can injure workers.
Thus, the lesson plan for laborers cannot merely be an exercise in the technique of thin-tile masonry construction, but must rather emphasize “skills, structures and safety”, synthesizing construction technique, applied structural principles and concerns of safety. Builders must be familiarized with structural principles and offered tutorials about compressive load paths, so that they begin to get a feel for what makes a vault stand up. They must learn to always work with load paths in the masonry, insuring that any loading of the vault is sufficiently transferred to the supports. Such critical aspects of the behavior of masonry vaults must be taught to laborers for them to understand safe practices on site, e.g. how one may or may not load the vault during construction. For instance, if the scaffolding is entirely under the vault, forcing workers to work directly below the vaulted surface, they are not only more at risk should a collapse occur, but may also precipitate a collapse by accidentally pushing up on the vault from below (inducing tension into a compression-only structure).
Yet, if there is no shared language with laborers, how can they understand lessons for a new construction technique, let alone comprehend applied structural principles and the associated safety implications? Such critical concerns may at times be a tremendous challenge to communicate, but may nevertheless be taught in a very straightforward manner, when demonstration materials (like chains, buckets, etc.) and direct feedback (like loading tests, controlled collapses, etc.) are combined. In Ethiopia, where – again – material is very much constrained, one must be resourceful with teaching tools and modify the tool of choice (or method of instruction) based upon the understanding of the group. One must pay close attention to distinguish when an important point has or has not been understood.
Drawing becomes a very important tool in this context; even the crudest of drawings scratched into the ground, soil masonry surfaces, or drawn on hands are tenfold more descriptive than words.
When language is not shared, a great deal of patience and also a dose of the absurd is sometimes called for to make understanding possible, while alleviating the stress of not understanding experienced on both sides. Language can itself be employed as a learning tool, used in a gaming manner to play on double-meanings or the sound of known words to make a meaning known. When teaching with incomprehensible words… if you can’t make someone laugh, you are in trouble.
The first efforts at the full scale must be carefully observed, anticipating the behavior which compromises either safety of crew or safety of the structure. Ultimately, a balance must be struck between directing, working with laborers, and giving workers space to learn from error and figure it out themselves.
The goal, however, is to transition a crew to teaching each other as rapidly as possible, to reduce teaching interventions (and these only in the case in which safety is compromised). If laborers can effectively train and correct each other, than it is automatically much easier for them to correct themselves. Because the knowledge and transmission of skill is very much language-based, careful hierarchies of training should be established ‘on the ground’. A well organized training schedule can develop into a robust information transfer system.
Once the first phase of training has been accomplished, the training may become more complex. The timing between a mixer and brick layer must be well coordinated with this rapid technique – plaster sets very quickly and must be well-timed to minimize error and reduce waste. Developing a proficiency with the technique and building at an efficient speed are a difficult balance to strike, and one must alternately train the skills of accuracy, speed, and waste minimization to be used at the proper times. Techniques may be introduced to build speed, for instance, yet laborers must identify the critical areas which require reduced speed and accuracy.
Training laborers to auto-correct – or see their own tendencies to error – also means teaching them to be aware of sight-lines, their perception of accuracy based on their position on the scaffolding, and training them to change their position to better identify certain errors. They must learn to recognize the difference between an acceptable/ negligible error and one which has structural consequences; they must learn when it is necessary to remove masonry in order to most efficiently correct a problem and also learn the techniques of knocking bricks off a cantilevering surface without causing a large collapse.
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