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Zarei H, Nasekhian S, Talebian M H. (2026). Technical Analysis and Stability Measures in Vaulted Structures of Khuzestan from Elamite to Late Sasanian Periods. Parseh J. Archaeol. Stud.. 9(34), 145-183. doi:10.61882/PJAS.1290.902.1
URL: http://journal.richt.ir/mbp/article-1-1290-en.html

Abstract
Khuzestan, a primary center of mudbrick and fired-brick architecture in ancient Iran, witnessed the evolution of vaulted construction from the Elamite to the Late Sasanian periods. Among these, arched vaults served not only as structural elements but also as a demonstration of systematic engineering practices tailored to the region’s warm and semi-humid climate. Despite the abundance of surviving monuments, no comprehensive study has analyzed their technical and structural features to uncover the underlying stability principles. This study aims to examine the structural performance and recurring patterns of stability in arched vaults of Khuzestan. Field surveys, documentation of accessible structures, analysis of 111 identified vaulted buildings, and detailed examination of 21 selected representative examples were conducted. The study focused on the interaction of materials, geometric proportions, construction technology, and human craftsmanship in achieving long-term stability. Results indicate that vault stability depended on: 1) the type and geometry of bricks, consistent mortar thickness, and interlocking strategies; 2) diverse construction techniques, including corbeling, radial arrangements, and combination methods; 3) geometric proportions such as span, rise, and vault thickness; 4) adaptation to climatic conditions; and 5) the skill and experience of the builders. This research highlights the presence of a systematic engineering logic in pre-Islamic vault construction and provides a framework for restoration, conservation, and potential adaptation in contemporary architectural practice. The findings demonstrate that these vaults were not merely empirical or accidental in design but reflect deliberate, replicable, and coherent structural strategies.
Keywords: Structural Stability, Vaulted Architecture, Arched Vaults, Pre-Islamic Iran, Khuzestan.

Introduction
Khuzestan has historically played a pivotal role in the development of vaulted architecture within ancient Iranian civilizations. Vaults represent one of the most sophisticated elements of traditional construction, combining technical mastery, material understanding, and adaptation to environmental conditions. From the Elamite through Late Sasanian periods, vaulted buildings in Khuzestan reveal an evolution in construction techniques, reflecting the accumulation of knowledge and local innovation. Arched vaults, in particular, served as primary structural and functional components in ritual, funerary, administrative, and sometimes military architecture.
The study of these vaults provides insight into the strategies employed by ancient builders to achieve stability over centuries. Stability in traditional architecture encompasses not only physical durability but also cultural, climatic, and technical resilience. Builders utilized local materials, precise geometric proportions, and structured load distribution to respond to environmental and functional challenges. Despite extensive archaeological documentation, there has been limited focus on the technical principles underpinning vault stability, particularly in arched vaults.
This research addresses this gap by systematically analyzing recurring structural features, material properties, construction technology, and geometric patterns that contributed to vault durability. The study examines both historical continuity and the adaptation of techniques over time, demonstrating that pre-Islamic vaulting practices in Khuzestan were informed by deliberate engineering logic rather than trial-and-error. Understanding these principles is critical for bridging knowledge gaps in architectural conservation, informing restoration efforts, and inspiring contemporary applications of traditional construction methods.

Discussion 
Analysis of arched vaults in Khuzestan indicates that their long-term stability resulted from a combination of material selection, construction technology, geometric design, and human skill. Key aspects include:
Materials and Mortar: Builders employed trapezoidal, square, and rectangular bricks, wider and thicker at structural bases to distribute loads effectively. Mortars, including clay, gypsum, and bitumen, were chosen according to moisture conditions, ensuring cohesion and stability.
Construction Techniques: Techniques included inclined corbeling, radial arrangements, and hybrid approaches. Temporary wooden or reed supports facilitated precise execution, while multi-layer vaults with controlled thickness enhanced overall strength. Adjacent vaults were often coordinated to reduce lateral stresses.
Geometric Proportions: Ratios between span, rise, and thickness were carefully maintained across periods. Numerical proportional systems guided vault dimensions, while precise interlocking of bricks ensured efficient load transfer.
Human Skill: Mastery in aligning bricks, controlling mortar thickness, integrating vaults with walls, and designing stress-relief features such as recesses and buttresses reflected high craftsmanship.
The historical evolution from Elamite to Sasanian periods shows gradual refinement. Early Elamite vaults utilized simple rectangular cross-sections and limited brick types, while Late Sasanian vaults displayed sophisticated high-rise arches, modular brick use, and multi-layer arrangements. These developments indicate a cumulative knowledge system that informed construction practices and responded to functional and climatic challenges.
The study highlights that stability was never accidental; rather, it emerged from repeated, rationalized engineering practices. Such findings provide an empirical basis for restoration and reconstruction, enabling the preservation of architectural integrity and informing contemporary design strategies that draw upon historical methods.

Conclusion 
This research demonstrates that arched vaults in Khuzestan were underpinned by systematic engineering principles rather than empirical trial-and-error. Stability resulted from the integrated interaction of materials, construction technology, geometric design, environmental adaptation, and craftsmanship. The study identifies: 
- Strategic use of brick types and mortar selection to optimize structural cohesion.
- Refined construction techniques, including corbeling, radial arrangements, multi-layer vaulting, and controlled thickness.
- Geometric proportionality ensuring balanced distribution of forces.
- Adaptation to climate and environmental constraints.
- High-level craftsmanship in aligning elements and controlling structural behavior.
Historical analysis reveals a continuous technological development, culminating in Late Sasanian vaults that exemplify peak structural refinement. Documenting these features provides a foundation for preservation, restoration, and potential adaptation in modern architectural practice. Future studies may compare these vaults with contemporary structures in neighboring regions or explore the influence on early Islamic architecture in southwestern Iran.
The study confirms that pre-Islamic vault construction in Khuzestan represents a coherent, replicable, and sophisticated engineering tradition, offering valuable lessons for both conservation and contemporary design.