BRE EP101 PDF

INTRODUCTION

Earth buildings are perceived by many as simple ‘mud huts', liable to damage, and earth as at the bottom of the list of desirable construction materials. While earth buildings are more liable to damage by water than those constructed from other construction materials, earth is one of the simplest and most sustainable construction materials, and many of the oldest structures in the world are constructed from this material. Around 30% of the UNESCO World Heritage Sites are constructed from earth.

In common with buildings made from all other types of construction materials, historic earth buildings are liable to damage, through lack of maintenance to protect against the weather, changes to the local environment, or damage caused by external factors. This book aims to present the reasons for the occurrence of such damage, and to provide strategies that may be useful in the conservation of historic earth structures. We do this by providing a scientific rationale for the behaviour of earth buildings. By viewing earth buildings in the framework of unsaturated soil mechanics, we are able to better understand their behaviour, and thus the damage that earth buildings may suffer.

The book begins with an introduction into the different types of earth building, and we argue that although the construction techniques are markedly different, there are definite common themes that apply to every type of construction material. In Chapter 2 we briefly describe the history of earth building, using some of the main archaeological and architectural sites worldwide. This serves to allow the reader to place any structure under investigation into an international and chronological context. The principles of general and unsaturated soil mechanics are outlined in Chapter 3. Relatively recent research findings allow for an improved understanding of the mechanical behaviour of earth buildings, and in Chapter 4 we show how this relates to observed damage mechanisms in earth buildings. Finally, in Chapter 5 we present mitigation and repair solutions that may prove useful in the conservation of historic earthen sites.

This book is not a practical guide on earthen construction, nor is it an engineering textbook. Techniques for different types of earthen construction can be learned from numerous sources, both through practical courses and through guides. A history of earth building is provided that focuses on some main sites, although many are not included for brevity, and the history of specific earthen sites is not explored. The principles of unsaturated soil mechanics are explained, but there are many logical steps that are not included, and reference should be made to our journal papers and to other engineering textbooks. As earthen construction is so varied, and as there is a much smaller pool of test data than for other, more conventional construction techniques, specific values for soil testing and mechanical properties are not given. We do not provide information on field or laboratory techniques for the testing of earthen materials. Engineering analysis methods for structures are not explained, and the advice of a competent engineer should always be sought when considering the conservation of historic earth buildings.

Finally, the behaviour of earthen buildings in earthquakes is not specifically discussed. This behaviour is complex, and although the damage mechanisms are similar to those described in this book, we do not deal with these, or with the retrofitting or reconstruction of earth buildings after seismic events.