الرئيسية / قسم الدراسات العليا / APPLICATION OF ENGINEERING GEOLOGICAL STUDIES TO THE PROTECTION OF HISTORICAL MONUMENTS OF THE DEIR EL-BAHARI AREA, HATSHEPSUT TEMPLE,EGYPT

APPLICATION OF ENGINEERING GEOLOGICAL STUDIES TO THE PROTECTION OF HISTORICAL MONUMENTS OF THE DEIR EL-BAHARI AREA, HATSHEPSUT TEMPLE,EGYPT

PREFACE

The ancient Egyptians were the first people of antiquity to believe in life after death. They were the first to build in stone and to fashion the arch in stone and brick. They sculpted in stone and decorated the walls of their tombs with naturalistic murals in vibrant colors. The legacy of ancient Egypt is written in stone across the face of the country from the Pyramids of the Old Kingdom to the Upper Egypt Temples to the rock Tombs in the Valley of the Kings and Queens, to the Ptolemaic Temples of Edfu and Dendera, to the Roman Temple of Isis on Phials Island to Hibis Temple of Kharga Oasis in the western desert.
The studied area of the Deir El-Bahari valley is located in the upper Egypt opposite the Luxor city, on the western bank of the Nile, at the Latitude 25 43 09// N and Longitude 32 39 07// E.  Many of the pharaohs and a few of their relatives and retainers had constructed temples and tombs which were cut into the limestone massive and the shale layers beneath it. All of the royal tombs and many of the tombs of the nobles are present in the Valley of the Kings, the Valley of the Queens, the Deir El-Bahari Valley and adjacent valleys. Large, chambers were cut into the limestone and the shale bedrock. The walls, columns and ceilings which were covered and painted with hieroglyphic texts have suffered considerable damage. Many deterioration factors are involved: natural, technical, and uncontrolled human activities have all affected these structures. Conservation of the historical monuments is now being reviewed by many specialists in different fields and a large proportion of new publications concerning the archaeological works now deal with deterioration, conservation, treatment and protection processes even stability problems.
The engineering-geological approach to conservation practice has already demonstrated its worth. The movements of the monument constructions are manifested by a redistribution of the stresses in the structure and in foundation loading, consequently the loading results in upheaval or settlement. Therefore, studies which consider the relationship of surrounding rock-mass to the monument structures should not be undertaken lightly.
The research aims to study the behaviour of the historical monuments and the surrounding expansive rocks, especially in the context of water penetration. However, to obtain a basic understanding of the mechanisms which cause deformation and possibly collapse of the studied monuments, it is useful to postulate some simple mechanisms based on the field observations and measurements as well as on computer modeling. Therefore, the thesis deals with a series of investigations into the observed geotechnical hazards and their causes and possible solutions for minimizing the distress suffered by the monuments.
The first stage of the study was the field mapping of the area of Deir El-Bahari, a field collection of the climatic data and the in situ determination of rock strength using the Schmidt hammer test. Many photographs of selected sites were taken at this stage.
T he rock samples from Deir El-Bahari for laboratory researches were taken then. These were later examined to determine their physical and mechanical properties, especially in terms of their swelling characteristic.

Based on the experimental data, numerical modeling to simulate the observed failure due to swelling phenomena has been performed. The numerical analysis was carried out in respect of the failure of the retaining wall which consisted of massive rock blocks. The wall is used to retain the rock fill between the adjacent rock-mass and the structural elements. The numerical model has also been extended to review the control work which has already been carried out to try to overcome the failure, which is believed to be due to the horizontal movements of the adjacent expansive rock-mass. Following from the various numerical analysis and simulations the various proposals for a method to control the failure of retaining walls have be considered.
This study has also been extended to include an examination several of commercial consolidants which are used in the conservation of the stone structures and for diminishing the swelling phenomena in expansive rock. Two polymer based groups: Aliphatic Isocyanate and Silicon Ester components were included. Laboratory experiments have been carried out on the consolidants in order to evaluate of their efficiency in improving the resistance of treated rock samples to swelling, weakening and disintegration.
The initial results of the tests on the applied commercial consolidants have revealed that these were ineffective, both rock types continuing to be affected by swelling.
Consequently, a new treatment to reduce the hydration reaction of expansive clay minerals and their cation constituents is suggested, which is based on a combination Silicon Esters and Al-pillaring agents.

 

 

SUMMARY

Engineering geological survey has an important role to play in the conservation of ancient monuments. As the movements of the monument constructions related directly to a redistribution of the stresses in the structure and in foundation loading, and as these loads, in turn, influence the upheaval or settlement, it is obvious that studies concerned with conservation should thoroughly consider the nature of surrounding rockmass.

This research concerns the behaviour of the historical monuments on a rock foundation which is liable to expansion on wetting. In order to achieve a reasonable and practical proposal to overcome (or even to minimize) the distress caused by volume change of expansive rocks, it is first necessary to characterize this rock and recognize its behaviour. The object is to collect sufficient information about predicated amounts of swelling and also determine the pressures at which the swelling will be counteracted; thus to propose a convenient support sufficient to overcome the influence of swelling pressure on the retaining walls in the future. This work also seeks to determine the different physical and engineering parameters of the representative rocks. The knowledge of such parameters might eventually enable predictions concerning the deformations in the rockmass surrounding the monumental structures to be made; this knowledge is also useful for stability-analysis using numerical models. In order to try to diminish the swelling action and its destructive impact on monument structures this research also involves a study of the chemical consolidants used in stone conservation; it also includes an evaluation of their characteristics through laboratory testing.

Thus, the thesis may be considered in three main parts. The first part is divided into two chapters, the first dealing in detail with the geological setting of the Deir El-Bahari area of Upper Egypt, on the western bank of the Nile. This chapter includes the historical background of the monuments studied as well as location, topography, regional stratigraphic sequence and geological structure of the study area. The second chapter describes the hazards which menace the Hatshepsut Temple and Montuemhat tomb. This is followed by an observation of the different problems and the decay phenomena related to expansive rocks-water interaction. The decay phenomena such as blistering, exfoliation, cracking, buckling, spalling and salt recrystallization have been documented by photographs. A review of the climatic conditions in the study area has revealed that the sharpest variations of temperature and humidity are recorded when the sun strikes directly on the wall surface at 2 p.m., soon after sunset in the early morning. The changes can be as large as ±75% R.H. and ±25 °C. In situ evaluation of the initial rock strength was made through the use of the Schmidt Hammer test. The results were calculated to be 15.76 MPa for the Esna shales and 26.68 MPa for the interbedding marls in the retaining wall area (az. 110°), whereas, it was 22 MPa for the Esna shales and 21.5 for the interbedding marls at the tomb of Montuemhat (az. 110°). The results of the strength measurements revealed that the greater part of the two rock types considered in this study is of weak to medium strength. This chapter also contains a survey of the deterioration agents and how they attack the ancient monuments; these are analyzed in term of original defects, natural actions and human actions.

The second part reports on the experimental work has been carried out on two expansive rock types; Esna shales and interbedding marls and also the limestone construction materials obtained from the Deir El-Bahari area and the selected salt samples. The second part of this thesis is similarly divided into two main chapters, numbers 3 and 4. In the first section of the third chapter, the laboratory investigation is presented. This deals with analysis of mineralogical components, and their roles in the decay phenomena. The results of mineralogical investigations, using chemical analysis by atomic absorption method, X-ray diffraction and microscopic studies, show that clay minerals such as Smectite, interlayer of Smectite-Illite and kaolinite as well as carbonate minerals such as calcite and dolomite are the main constituents in the representative shale samples, whereas quartz, pyrite, iron oxides and gypsum are minor constituents in the same samples. The interbedding marls samples revealed that dolomite, calcite and clay minerals are the major constituents in addition to quartz, pyrite and iron oxides as minor constituents. The thin-section and scanning electron microscope examinations revealed that both rock types are mostly heterogeneous aggregates. They are sediments which are fairly typical of a marginal marine depositional environment.. The results of microscopic examination of the fills of fractures indicate that a very strong chemical weathering takes place in the presence of infiltrated waters. The second section of third chapter deals with the physical and mechanical properties of the natural (i.e. untreated) rock samples. The parameters which govern the physical and geotechnical properties, such as strength and rock swelling characteristics (which include liquid and plasticity limits, swelling ratio and swelling pressure) are considered here. The results of the geotechnical rock properties for the natural rock samples, as presented in this chapter, have variable values, as follows:

a) the average bulk density (r) is 2.22 T/m3for the Esna shales and 2.07 T/m3for interbedding marls.

 

b) the natural moisture content (w) is 4.9% for the Esna shales and 2.92% for interbedding marls.

c) the total effective porosity (P) is 20% for the Esna shales samples and 21% for interbedding marls.

d) the water absorption coefficient (W) is 16.3% for the Esna shales and 15.6% for interbedding marls.

e) the acoustic wave velocity (Vp^) is 2234 m/s for the Esna shales and 2278 m/s for interbedding marls, whereas (Vp||) is 3477 m/s for the Esna shales and 2886 m/s for interbedding marls.

f) the dynamic modulus of elasticity is 1.11 GPa for the Esna shales and 1.08 GPa for interbedding marls.

g) the liquid limit is 52.4% for the Esna shale and 44.66% for interbedding marls, while the plasticity limit is 30.5% for the Esna shale and 26.33% for interbedding marls.

h) the free swelling ratio (es) is 45.6% for the Esna shales and 20.46% for interbedding marls in a direction perpendicular to bedding, whereas, in the direction parallel to bedding, it is 2.37% for the Esna shale and 3.09% for interbedding marls

i) the swelling pressure is 4.7 MPa for the Esna shale and 3.5 MPa for interbedding marls.

j) the Uniaxial compressive strength (sc) is 27 MPa for the Esna shale and 18.9 MPa for interbedding marls.

k) the Brazilian tensile strength (st) is 3.23 MPa for the Esna shales and 4.37 MPa for interbedding marls.

l) the static modulus of elasticity is 1.21 GPa for the Esna shales and 1.59 GPa for interbedding marls.

The fourth chapter deals with an experimental numerical study to evaluate the characteristic material behaviour according to the data obtained in laboratory tests and in field observations and make a back analysis of the failure phenomena of the monuments at Deir El-Bahari area. Using such a simulation of the natural case as a guide, better understanding of the behaviour and mechanisms which govern the failure phenomena at Deir El-Bahari area is achieved. The numerical judgment is very important in trying to achieve the optimum suitable solution. The numerical simulation considers with three parts of the retaining wall. Two of these exist in reality, one coincides with the original situation of the retaining wall, the second represents the case after stabilization that had been introduced consequent upon collapse of the wall. The third modeled the retaining wall in respect of efforts to stabilize the retaining wall where if is affected by the horizontal pressures due to Esna shales swelling. The results from the numerical model reveal that both of the original retaining wall and that modified by control work are still affected by a critical shearing stresses, and are liable to tension failure. Only the third modeled phase is unaffected by a critical shearing stress and this is only because of the flexible polystyrene blocks which have been inserted between concrete slab and limestone constructing blocks. The polystyrene does not transmit the internal forces which tend to exert pressure on the facing wall.

The third part of the thesis deals with an extensively investigation of the consolidation treatments which carried out to try to diminish the swelling phenomenon, using commercial consolidants. The commercial consolidant selection was restricted to two based-polymer groups: Aliphatic Isocyanate and Silicon Ester components. The preliminary results of investigation concerning the Esna shales and the interbedding marls which had been treated with the Aliphatic Isocyanate and Silicon Esters showed that they are tended to crack and swell as in cycles of wet-dry conditions.

An innovative treatment of Silicon Ester in two variants was applied: either as a mixture with Al-hydroxy oligomers to give SiAl-pillared agents or as a combination of these applied alone at interval.The results show that, out of the 5 applications under investigation, the treatment which combined methyl trimethoxy silane (MTMOS) and Al-13 is the most promising for conservation practice. Only poor results were obtained using the Silicon Ester-based polymer alone (MTMOS & ETEOS); the pure organic polymer (Diisocyanate) gave an unacceptable result, swelling being even greater than in the case of the untreated samples.

During the examination of the physical, swellability and mechanical properties which (including the water absorption coefficient), the swelling ratio for the treated samples was compared with those of the untreated samples. The results for the treated rock samples show that the combined treatments between water-repelling polysiloxanes and Al-13 pillared clay satisfied almost all of the needs; they are stronger and they decrease the water absorption, thus leading to decrease in the swelling ratio. Further no fissuring or increase in volume was noted.

Lastly, it should be noted that, on the basis of the results, it would be well worthwhile to test consolidants which give the best results in a more extensive way, and, in light of the results of the research, when the protection of monuments is being considered, the conservator must be expected to use his or her judgment and common sense. He or she should never rely on the results of laboratory tests alone. A knowledge of the behaviour of previous similar cases must guide judgments as to what is optimum solution to current problem.

 

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