Draft document for the sole use of the working group. INTRODUCTION
Part I Principles
Part II Guidelines
1 HISTORY OF THE SITE OF ANGKOR 7
2 GENERAL CRITERIA 9
3 ACTIONS ON THE STRUCTURES 12
4 ORGANISATION OF THE PROJECT 14
4.1 INTRODUCTION 14
4.2 PLANNING 14
4.3 ACQUISITION OF DATA 15
4.3.1 The historical research 15
4.3.2 Survey 15
4.3.3 Tests and investigations 16
4.3.4 Monitoring 16
4.4 DIAGNOSIS AND SAFETY EVALUATION 16
4.5 THERAPY 17
4.6 CONTROLS AND MAINTENANCE 17
5 MATERIAL CHARACTERISTICS AND DECAY 18
5.1 INTRODUCTION 18
5.2 CONSTRUCTION MATERIALS 18
5.2.1 brick 18
5.2.2 Sandstone 19
5.2.3 Laterite 20
5.2.4 WOOD 20
5.3 DECORATION MATERIALS 21
5.3.1 Stucco 21
5.3.2 Wall paintings and plaster 21
5.3.3 Polychromy 22
6 MATERIAL CONSERVATION 22
6.1 INTRODUCTION 22
6.2 SYSTEMATIC PLANNING OF CONSERVATION INTERVENTIONS 23
6.3 PRELIMINARY/EMERGENCY CONSOLIDATION 24
6.4 CLEANING 24
6.5 REMOVAL OF MICRO-BIOLOGICAL CONTAMINATION AND BIOCIDE TREATMENT 25
6.6 SALT REDUCTION 25
6.7 CONSOLIDATION 26
6.8 INJECTION OF SCALES AND POINTING 27
6.9 WATER-PROOFING 27
6.10 WASHES AND SACRIFICIAL LAYERS 28
6.11 QUALITY CONTROL AND MAINTENANCE PROGRAMMES 28
7 SOIL, WATER AND ENVIRONMENT 29
7.1 CLIMATIC CONDITIONS 29
7.2 VEGETATION COVER 29
7.3 THE WATER SYSTEM 30
7.4 SOIL 30
7.5 GROUND AND WATER 31
7.6 URBANISATION AND INFRASTRUCTURES 32
7.7 SOIL SETTLEMENTS INDUCED BY LOADS 32
7.8 SUBSIDENCE 33
7.9 Damage and progressive failure 33
7.10 Piping 34
7.11 Erosion 34
7.12 Earth structures and embankments 34
7.13 Drainage 35
7.14 Foundations 35
7.15 Retaining structures 36
7.16 Mountain Temples 36
7.17 Archaeological excavations 37
8 STRUCTURAL BEHAVIOUR AND DAMAGE 37
8.1 STRUCTURAL CHARACTERISTICS 37
8.2 BRICK CONSTRUCTION 37
8.3 SANDSTONE CONSTRUCTION 38
8.4 LATERITE STRUCTURES 39
8.5 STRUCTURAL DAMAGE 39
8.6 DAMAGE PRODUCED BY SOIL MOVEMENTS 40
9 CRITERIA AND TECHNIQUES FOR STRENGTHENING STRUCTURES 41
9.1 GENERAL CRITERIA 41
9.2 UNDERSTANDING THE STRUCTURE 41
9.3 DISMANTLING AND REASSEMBLY 43
9.4 RECOVERING DEFORMATIONS 44
9.5 STRUCTURE INVOLVED BY NOT STABILISED SOIL SETTLEMENTS 46
10 RISK MAP 47
Introduction Recognising the outstanding nature and diversity of heritage at Angkor this document was prepared to assist technicians working in the field to plan and implement conservation interventions using a shared philosophy, while respecting the diversity and specificity of each situation.
For the past 20 years in Angkor, experts have been meeting and discussing the technical intricacies of the conservation at Angkor. A form of consensus has been reached. This document aims at outlining the consensus of opinion on key questions. Thanks to the works implemented and agreement reached among the teams working in Angkor, this Charter will facilitate for new generations of conservators the planning and implementation of rightful conservation interventions by then reducing the risk of choosing a wrong approach as was sometimes the case in the past.
The document is divided into two parts. The first part (Principles) outlines some of the basic principles of conservation that have already been agreed at the international level and can be found in various charters.
The second part (Guidelines) is divided in many chapters which, following extensive debates, broach the problems of: the acquisition of data; diagnosis and safety evaluation; the identification of materials used during the construction of the temples in the Angkor region and, finally, the building techniques used. The causes of the decay and subsequent alterations to the temples are then exposed, as are the major methods of research and evaluation, as well as the systems to record and archive data.
Finally, the recommended criteria and techniques for the conservation of the Khmer monuments at Angkor are detailed. The ultimate chapter of the document deals with issues related to the protection of the monuments and the Risk Map.
RECOMMENDATIONS FOR THE CONSERVATION AND SAFEGUARDING OF THE SITE OF ANGKOR
Conservation, reinforcement and restoration of architectural heritage require a multi-disciplinary approach.
The value and authenticity of architectural heritage cannot be assessed with set criteria as each culture is different and has to be respected as such, and requires its physical heritage be considered within the cultural context it belongs to.
The peculiarity of heritage structures, with their complex histories, requires the organisation of studies and analysis following steps that are similar to those used in medicine. Anamnesis, diagnosis, therapy and controls, respectively correspond to: The condition survey, the identification of the causes of damage and decay, the choice of the measures to remedy these issues and the control of the achievements of the interventions. In order to be cost effective and ensure minimum impact on architectural heritage, it is often appropriate to repeat these steps in an iterative process.
A full understanding of the structural behaviour and of the characteristics of the constituent materials is essential for any conservation and restoration project. Research should be carried out on the original and earlier states of the structures, on the building techniques and construction methods used, on subsequent changes, on the various phenomena that impacted the structure, and finally, on its present state.
Before taking any decision on structural intervention it is indispensable to first determine the causes of damage and decay, and then to evaluate the present level of structural safety.
Adequate maintenance can limit or postpone the need for subsequent intervention.
No actions should be undertaken without demonstrating that they are indispensable.
The design of any intervention should be based on a full understanding of the kinds of action (forces, accelerations, deformations, etc.) or agents that have caused the damage or decay and of those that will act in the future.
The choice between “traditional” and “innovative” techniques should be determined on a case-by-case basis with preference given to those that are least invasive and most compatible with heritage values and consistent with the need for safety and durability, as well as availability of means for its maintenance.
At times, the difficulty of evaluating both the safety levels and the possible benefits of interventions may suggest “an observational method”, i.e. an incremental approach, beginning with a minimum level of intervention, with the possible adoption of subsequent additional or corrective measures.
The characteristics of materials used in restoration work (in particular new materials) and their compatibility with existing materials should be fully established. This must include long-term effects, so that undesirable side effects are avoided.
The distinguishing qualities of the structure and its environment that derive from its original form and any significant subsequent changes should not be destroyed.
Each intervention should, as far as possible, respect the original concept, construction techniques and historical value of the structure and the historical evidence that it provides.
Repair is preferable to replacement.
When imperfections and alterations have become part of the history of the structure, they should be maintained providing they do not compromise safety requirements.
Dismantling and reassembly should only be undertaken when required by the nature of the materials and structure and/or when conservation by other means is more damaging.
Measures that are impossible to control during execution and which efficiency cannot be verified should not be allowed. Any proposal for intervention must be accompanied by a monitoring and control programme to be carried out, as extensively as possible, while work is in progress.
All conservation control and monitoring activities should be documented and retained as part of the history of the structure.