gy~ 3f" BERG.'Sc and AKE DAHLSTROM,t

Transcription

1 qji gar.- gy~ k~u g 4 3f" The two Abu Simbel temples, in their ancient and original position by the Nile By LENNART The two Abu Simbel temples, see above, and their salvage, have been written about in many other connections. Thus, in this article, only a brief description will be given for orientation, special emphasis being accorded to the problems of drainage. Both temples were cut out of the cliff proper about years ago, under the reign of King Rameses, the Great in honour of the King himself, the Small being spouse, dedicated to his favourite Queen Nefertari. The Great consists of an outer facade with four colossal statues of Rameses himself and a number of smaller statues, wall decorations, etc.. and fourteen rooms hewn out in the interior of the cliff. The Small has a facade with six main statues, smaller than those of the Great, and five inner rooms. Aff rooms have richly decorated Chief Consulting Engineer, Vattenbyggnads- byran VBB), Stockholm, Sweden tsenior Engineer, VBB, Malmb, Sweden engineers and VBB acted as consulting for the architects to the UAR Government entire operation temples of salvaging the Abu Simbel BERG.'Sc and AKE DAHLSTROM,t The major operation of salvaging the two famous Abu Simbel temples in southern Egypt in the years involved many different and unusual problems. One problem of the utmost importance was to prevent the Nile water, free or as ground water, from with the friable in touch coming sandstone of the temples. This article gives a short description of the measures taken to deal with this problem, especially the ground water walls, pillars while in some and statues. there are also Both temples were situated near the shore of the Nile, only a few metres above the Nile water level. When, in 1964, raising of the Nile water level was to be started behind the High Dam at Aswan, the Nile water would have flooded the temples had no precautions been taken. Such an inundation would have rapidly destroyed the temples, which consist of a rather friable sandstone with poor cementation. Thus the salvage operation not only MSc meant cutting out and moving the temples to a higher level, but also involved the building of a cofferdam outside the temples, combined with a drainage system, to function until all parts of the temples had been dismantled and reassembled at a safe elevation. sites and cofferdam A plan of the two temple sites and the cofferdam is shown in Fig. 2, with the Great to the south and the Small to the north, the distance between amounting to them about 150m. n order to keep both sites safely dry, the protective cofferdam was given a length of about 350m and a height of more than 20 m above the river bed. t was planned that the removal of the temples should be completed by the middle of As can be seen from the Nile water level diagram in Fig. 3, the cofferdam had to be built for a maximum water level of about SSL m during the winter season of The design of the cofferdam section can be seen in Figs. 3 and 4. The Ground Engineering 13

2 Fig. 1. Progress picture taken during the erection of the cofferdam construction of the cofferdam was started with the placing of a sandfill on the Nile bottom reaching well above the present water level. From the platform thus established, steel sheet piling was sunk by means of vibroflotation through the sandfill and the natural river bed deposits down to the underlying bedrock. The steel sheet piling was then extended upwards, and rockfill was placed on both sides. On the inside, the cofferdam was provided with filters and a drain pipe. As a further precautionary measure, a row of deep well pipes was placed WE inside of the drain pipe. n fact, these deep wells were operated before the filters and the drain pipe of the cofferdam had been completed. Three deep wells in front of the Small were also operated later, as will be referred to later. Previous investigations Before the salvage operation proper was started, extensive investigations had been carried out, dealing among other aspects of the scheme, with the drainage problem being considered here. By means of boring in the river bed and in the shore outside the temples. the composition and the thickness of the natural deposits above the rock ground had been established Figs. 3 and 4). As could be expected, the deposits consisted of sand and silt in layers of varying thickness and distribution. From the foot of the cliff, on the southern side of both temples, vertical pits and sloping galleries tunnels 17 and 18 in Fig 2) were excavated into the sandstone rock down to a depth of about 8 m under the present Nile water. By pumping in these pits and galleries the amount of leakage under various conditions could be calculated. Since the Nile water level was to rise above the ceilings of the temple rooms, exploratory borings were also made in the sandstone rock beside and above the temples. Although the sandstone consisted of layers of varying thickness and grain size, it could be considered fairly homogeneous from the leakage point of view. Tests carried out on sandstone samples gave permeability coefficients varying between 10-'nd 10-'s. On the basis of these values, as well as of the practical pumping tests and the other investigations mentioned above, it was calculated in advance that the total quantity of leakage ought not to exceed about 500 litress Fig. 2. Plan of the temple area with ground water table. mid-march, 1965 FG. 3 W RVER NLE Fe L~ 0 50 o DEEP WELLS 14

3 Fig. 3. Section of cofferdam and Great, with Nile water level variations >SL WO WATER LEVEL OF THE NLE J '31 T'A 1, liu COFFERDAH W U SEL N ~ NWDLE NOT. HS S. NL ESL TS S NDDLE NAOCN HS ~E mt JJJJJJlJ1T1~qMUO WATfO TAOLE N' NDDLf NOU HS $$LRE $$S 1$$5 1$$$ 1$$ SANO ANO SLT DEDOSH OATUOAL NCE LOEDUND WATEO TAELE NOOLE NADCN SSS SSL 1$0 SSL 1$0 SSL LO ~WL SSL 133.$ HDDLE NOV 100$ ~WL SSL 1205 HDDLE HARCH 100$ ~,Q DCK SSL 120 SSL 110 SSL 100 ~ f7t",o a 'ANO F ; '.':. V ''W'AND AND SLT OEPDS TS% COFFERDAM ASSL 13$ ~. 0LL '1 Oo FLTERS X~MAL~QE DEEP WELL -OROVNO WATER TASLE ll llh8 U ~A HDOLE NOV 1005 FLL DRAN 0ROVND WATER TASLE HDDLE HARCH 1005 NATVRAL ROCK Fig. 4. Section of cofferdam and Small t could also be foreseen that water would penetrate into the sandstone during the winter season , when the Nile water level was to reach its maximum during the working period in question. Drainage aims Before the building of the High Dam but after the raising of the Nile behind the Old Aswan Dam, the water level normally reached its maximum during the winter at SSL 120, i.e. practically up to the floor of the Small Fig. 4). As could be seen from marks in the Small facade and walls, the water had reached about one metre higher under exceptional conditions. Above these levels, there was also an effect of capillary water, the height of capillarity, however, seldom exceeding one metre. The condition of the sandstone in the lower parts of the Small was thus comparatively bad. However, it was known that the wet sandstone regained at least some of its original strength when dried again, and it was decided that the ground water level beneath the Small should be kept below SSL 119 from the summer of 1964 until the summer of 1966, when the temple would have been removed. Under the Great, with its floor at about SSL , it was deemed sufficient to keep the ground water table below SSL 121. A further aim of the drainage was, of course, to keep the shore in front of the temples and the whole working area conveniently dry. Drainage arrangements The drainage arrangements had to be designed to meet the following eventualities: 1. Leakage through the cofferdam. 2. Leakage through the rock under the cofferdam. 3. Leakage into the rock outside the abutments of the cofferdam. The upper part of the steel sheet piling in the cofferdam had been specially tightened, and practically no leakage was expected from that quarter. For leakage through and under the lower part of the cofferdam, filters and a drainage pipe had been arranged on the inside of the cofferdam, as previously mentioned. The drainage pipe led to a specially arranged pump pit, which also collected the leakage water from other parts of the site and discharged it back to the Nile. However, even at the beginning it was found that the ground water table in the shore, on the inner side of the drainage pipe, was about 2m higher than at the pipe itself Figs. 3 and 4). Evidently the cofferdam drainage was separated by a layer of silt from underlying, more pervious layers of sand. Therefore it was decided that three deep wells situated in front of the Small, should be maintained for later operation, if necessary. rock outside the abutments of the cofferdam. Thus water could be expected to find its way through the cliff proper and reach the temples from the sides and even from the rear. To prevent this, the investigation tunnels 17 and 18 had also been planned to serve as drainage galleries. t was also prescribed that the contractor should excavate a third tunnel, No. 19, north of the Small, for the same purpose see Fig. 2 as well as Fig. 5). The latter figure shows a longitudinal section through the cofferdam abutments, the drainage galleries and the temples proper, as indicated in plan on Fig. 2. n case some water might follow specially pervious layers, if any, above the galleries, boreholes were drilled upwards from the gallery roofs. Actually only a little water came from these holes, and the galleries very efficiently lowered the ground water table as intended. The eventuality of ground water reaching the temples from the rear was very much a question of time. Since the periods of high water were limited, the risk in this respect could be deemed as small. However, the movements of the ground water table were closely followed by means of a number of observation holes, see Fig. 2, some of them being arranged in the floors of the innermost temple rooms. f found necessary, these holes were planned to be enlarged and used as additional drainage pits. Ground Engineering 15

4 SOUTH ABUTMENT COFFEROAM WL SSL 1334 SS. 13$ SSL HGGLE NOV 1$$$ GREAT TEMPLE Me'~ GROUND WATER TARLE HDDLE NOV 1$$$ SMALL TEMPLE 4 3 HDOLE HARCH 1$$$ ~SS 13$ EO OO GROUND WATER TARLE RDDLE HARCH 1$$ $ SSL SCALE OF LENGTH room Fig. 5. Longitudinal section of the temple site Generally, the leakage of the galleries was pumped to the collecting pump pit, as mentioned above, for final discharge into the Nile. From tunnel 18, however, the leakage was pumped directly to the water plant of the site colony, and served as an excellent raw water for this purpose. The total capacity of the pump installation as measured at the final discharge from the working area amounted to 500 litress, in accordance with the figures mentioned above. The actual figure of the total leakage discharge was recorded continuously. Winter of During the winter season of , the Nile water level reached its maximum, SSL , in the middle of January. The maximum total leakage amounted to about 100 s. The ground water table below the innermost part of the Small reached a maximum level of SSL in the middle of March and maintained this level until the middle of April. Under the innermost part of the Great, the ground water table did not reach its maximum, SSL 118.5, until the middle of April. A compilation of some observed water levels, illustrating the above, is shown in Table below. The position of the ground water table in the middle of March, 1965, can be seen from the vertical sections in Figs. 3, 4 and 5, as well as from the plan in Fig. 2. From the experience thus gained during the winter season , 16 TABLE. WATER LEVELS, SSL, N: Date The Nile The shore valuable conclusions could be drawn as to what could be expected during the winter season , when the Nile water was to be raised a further 5.5 m, to SSL The risk of too high a ground water table under the Great was deemed to be low, although the variations of the water level would be closely followed. As regards the Small, it was foreseen that it might be necessary to make use of the well points in front. n addition, a pump pit was made inside the Small. t could also be estimated that the maximum total leakage would probably be about 150 litress and would certainly not exceed the figure of 250 litress, corresponding to half of the installed pump capacity. Winter of During the winter season of , the Nile water level varied as shown in Fig. 6. t reached a maximum of SSL at the beginning of November, was some decimetres lower in December, but very nearly reached during the whole of January. At the beginning of March it began to fall rapidly. Below the inner part of the Great, the ground water table reached SSL in December and in January Fig. 6). However, the dismantling of the inner rooms of the Great was completed in December. Under the other rooms of the Great, finally dismantled in March, the ground water table was lower. T e inne Pa t of Great The inner part of Small The ground water table under the Small rose continually from SSL at the beginning of September to SSL in the middle of November Fig. 6). At this time pumping in the deep wells in front of the temple was started, to be continued untff the dismantling of this temple was completed at the end of February. This additional measure was enough to keep the ground water table below SSL 119 as prescribed, and it was never necessary to use the pump pit inside the temple. An example of the configuration of the whole ground water table during this season, namely in the middle of November, 1965, is given in the sections of the Figs. 3-5 and in the plan of Fig. 7. During the following three or four months, the ground water table continued to rise behind the temples, but its influence on the water level below the temples proper was dealt with as stated above. The total leakage amounted to 150 litress already at the end of September and it maintained this value until the latter half of November, when it began to decrease slowly. Such successive diminishing of the leakage, in spite of the same or even higher outer water level, had also been observed during the last season, and surely depended on the tightening effect of high flood silt sedimentation over the infiltration area. The maximum leakage was distributed as follows: Cofferdam drainage litress Deepwells in front of Small 15 Tunnel 17, south of Great 55 Tunnel 18, south of Small 25 Tunnel 19, north of Small 15 Total leakage 150 litress Conclusion A description has been given above of one of the many interesting problems associated with the salvage of

5 SSL 133 SSL 125 L NLE WATER LEVEL AT ABU SMBEL TE- DSMANTLNG OF THE NNER ROOMS OF GREAT TEMPLE FNSHED N DEC 1965 SSL 120 GROUND WATER LEVEL AT GREAT TEMPLE SSL 115 rf GROUND WATER LEVEL AT SMALL TEMPLE o DSMANTLNG FNSHED AT SMALL TEMPLE N DEEP WELLS AT SMALL TEMPLE STARTED TO OPERATE SEPT. OCT. NOV. DEC. JAN Fi g. 6. Water levels during the winter season of FESR MARCH the Abu Simbel temples, i.e. the problem of keeping the ground water away from the temples during the last two years in their old location, when the Nile had started to rise, threatening to destroy them, wholly or partly. The problem was solved, and the Great had no contact whatsoever with the ground water, even when the Nile had risen 13 m from its old high flood level. For the Small, conditions were better during the last two years than previously. The ground water table was maintained more than 2 m lower during the second last winter season and about 1.5 m lower during the last winter season, as compared with previous normal high water levels. The temple facade and room walls could be safely cut, down to the desirable level of about SSL 119.8, and removed to their new position without damage. t may be of interest to note that an attempt to dismantle some rock under the facade, down to about SSL 119.0, did not succeed. The sandstone here was still moist from capillary water and disintegrated into small fragments and sand, when the blocking out cutting had been finished and lifting started. j Fig. 7. Plan of the temple area with ground water table, mid-november FG. 3 P RVER NLE FG 4~ 50 o DEEP WELLS Ground Engineering 17