The Conservation of Earthen Architectural Heritage in Seismic Areas

Abstract

The acceleration of climate change and the increasing frequency of natural disasters mean that there is an urgent need to adapt conservation strategies for architectural heritage to the world’s new demands and situations. This is particularly relevant for the most vulnerable constructions, such as earthen structures. Because of the dramatic effect that earthquakes can have on architecture, and especially on historical monuments, they have been studied for the past 50 years. Earthquakes divide the world in two very distinct geographic areas: seismic and non-seismic. The seismic vulnerability of earthen architectural heritage, such as earthen structures and mud mortar masonry, evidences in by how weak they are when compared to structures built using other construction materials (10 to 15 times weaker). Humanity’s past experience in the conservation of architectural heritage allows us to be aware of the need to improve and eventually perfect the existing conservation charters, which were discussed and signed in Europe in the last century. These charters do not make a distinction between heritage conservation in seismic and non-seismic areas. It is imperative to address this particular issue, as seismic forces can be too strong for earthen constructions to resist, which can lead to their irreparable collapse. Inspired by the Venice Charter and China´s principles as well as by more modern documents, such as the Burra, Mexico, Zimbabwe, Lausana Charters, researchers have tried to establish adequate and resistant conservation guidelines, based on achieving the best structural performance using a minimum permanent and reversible reinforcement. Although this involves causing some impact on the architectural heritage, it also means that human lives and buildings can be protected. The paper will provide real examples to illustrate these cases and will attempt to outline the conservation principles required to protect vulnerable structures, such as those earthen constructions or mud mortar brick or stone masonry built in seismic areas.

Preventive Conservation of Vernacular Adobe Heritage Located in Seismic-Prone Regions

“…Usually in the engineering community, the expression conservation of adobe architecture in seismic-prone regions is not commonly used. There are a few references regarding historical earthen buildings in seismic areas with the title of "conservation of earthen architecture heritage" (Montes, Giesen, 2010;Vargas-Neumann, 2012). In Terra Literature Review, "Earthen Material Conservation" (Oliver, 2008) and "Seismic Damage of Earthen Structure" (Webster, 2008) have been embraced separately in different chapters.…”

“…Professionals often study just the physical aspect of earthen architecture (Blondet, Aguilar, 2007;Minke, 2001;Morris, Walker, Drupsteen, 2011;Tolles et al, 2000;Torrealva, Vargas-Neumann, Blondet, 2006;UNIPD, 2012;Webster, 2008). There is very little research that deals with principles addressing conservation of earthen architectural heritage in a seismic region (Correia, Walliman, 2014), and no relevant intervention techniques have been considered (Vargas-Neumann, 2012;Vargas-Neumann, Blondet, Iwaki, 2010). Through the revision of the literature, a few research projects have been identified with a focus on the specified adobe monument or archaeological site in the seismic-prone regions (EERI, 2004;Maïni, 2004;Manafpour, 2003;Vargas-Neumann et al, 2011;.…”

“…In the engineering community, the expression conservation of adobe architecture in seismicprone regions is not of common use. There are only a few references regarding the historical earthen buildings in the seismic area with the title of "conservation of earthen architecture heritage" (Montes, Giesen, 2010;Vargas-Neumann, 2012).…”

Key Issues and Research Progress on the Deterioration Processes and Protection Technology of Earthen Sites under Multi-Field Coupling

“…They have carried out research on the concepts and principles of site protection to form international guidelines for the preservation, protection, and utilization of earthen architectural sites, and such research achievements have been widely applied to immovable cultural heritage sites throughout the world [8]. Furthermore, the structural design and seismic protection of earthen sites were researched to reveal the seismic characteristics and damage behaviors of earthen sites, forming the methods of site assessment and reinforcement [9,10]. The technology of the surface anti-weathering of earthen sites was researched, and soft cover against weathering was promoted [11].…”