Reinstating points of contact between the megaliths of Maltese prehistoric temples

Abstract

The Megalithic temples found across Malta and Gozo are prehistoric monuments dating back to the 3rd Millennium BC. With some being recognised as UNESCO World Heritage Sites, the temples have been recognised as some of the oldest free-standing structures in history, older than both Stonehenge and the Egyptian Pyramids. The temples are a result of a surge in innovative construction in the Early Neolithic Period, comprising a forecourt, typically oval in shape and a number of chambers, or apses which are circular in shape, all surrounded by a layer of backfill and a final external boundary wall. Since their unearthing in the late 18th and early 19th century, the temples have unfortunately suffered deterioration due to weathering, and therefore, points of contact between the individual megaliths has been lost. In arch action, load is transferred to the base by means of thrust or compression via non-vertical routes. The successful transfer of these forces depends on the contact between the individual voussoirs. This same action may be applied to horizontal arches, like those of the individual apses of the prehistoric temples and possibly their facades. However, the deterioration due to weathering has led to a reduced contact area between the megaliths, which may not be capable of resisting the loads they may be subjected to. By replicating the surface of a megalith through the use of a natural rock boulder found in nature, samples were cast, half of which were subjected to a material intervention in the form of lime mortar. These samples then allowed laboratory testing to be conducted, in both shear and compression. A comparison of the results obtained from samples with and without a material intervention showed that the samples containing a lime mortar intervention exhibited significantly improved performance in all aspects, proving that reinstating contact area between interfaces of a highly irregular surface profile would improve load transfer capabilities.