Fixing the Fort: Part 2
The time spent examining, observing, and working around the remarkable Enclosure of Khasekhemwy (the Fort) in December 2004 made us familiar with its details, imperfections, and blemishes. So when we returned at the beginning of February 2005, after a holiday break, it was quickly apparently to us that, even in this short time, gravity had taken its toll. It was only a matter of 4-5 fallen bricks here and perhaps a dozen there, but it was clear that the Fort needed more immediate attention. A look at the archival photographs shows what can happen over a period of exactly 100 years if left uncared for.
The west wall of the Fort in 1905. The north and south corners of the main walls are still intact and the south part of the perimeter wall still stands to near its full height. (Garstang Expedition, Liverpool University Archive Neg. H102)
The west wall in December 2004 prior to repairs. As gravity takes its toll, the holes just get bigger, taller, and deeper. Time is not on our side.
While it may take a trained eye to appreciate the fine details of the Fort, no expert was needed to understand the results of our brick tests. Before we left the site in December, we placed the newly created bricks in a variety of locations around the dig house compound. Examples of each recipe were exposed to wind, direct sun, shade, and combinations thereof. Some withstood these tests better than others. Although the consultants felt that the 1:3 (sand-to-soil) recipe best replicated the specifications they had developed for use at Abydos, these bricks did not stand up to exposure to wind. After just 6 weeks these bricks had lost their surfaces and testing (courtesy of Hassan Allam & Sons, Cairo) showed their dry compression strength to be minimal. The 1:4 and 1:5 mixtures held up better, but their excessive weight is a major consideration. Made without organic additives, they weigh 1.5 to 2 times more than the ancient bricks and their use in large area reconstruction may have serious implications for the foundations and adjoining brickwork.
So it was back to the drawing board for more experiments, but not before we picked up our custom-made brick stamp from the iron workshop at the nearby Coptic Monastery of Saint Pachomius (the ca. A.D. 290-346 founder of Christian cenobitic, or communal, monasticism, whose rule book of observances for monks is the earliest extant).
Not only are good mud bricks harder to make, but apparently good bricks stamps aren't that easy to manufacture either. As Abuna (Monk) Mousa explained to us, getting a metal rod just the right size and weight for the stamp's letters was a challenge. In the end, success was attained only at the expense of the doorknobs throughout the monastery! The rectangular shaft, that part that fits into the socket to release the latch when the knob is turned, turned out to be just perfect. Luckily the monastery was going through some refurbishment at the time. I don't know how the other monks felt about this use of their doorknobs, but we were all delighted with the stamp and its results.
||Father Mousa demonstrates our brick stamp. (Richard Jaeschke)|
While the search for the optimal brick continued, we still had many other questions that had to be answered before we could contemplate large-scale stabilization of the monument. For example, were the new bricks too big? Too small? What type of mortar would work the best? How should we lay the new bricks? Would there be settling or shrinking? While perhaps not the very best, we did have several different batches of adequate bricks ready for use while the new batches dried. In order to investigate these issues and do something to help the Fort, we chose several non-load bearing locations around the monument for repair with these bricks, each area representing a different set of challenges and questions. The work is entirely reversible, if necessary, and the removal of the new brick work, if it is found to be inappropriate for the long term, will have no ill effect on the structure, and whatever the ultimate result, at least for the moment the repairs hold off that inescapable tug of gravity.
We began our work on the interior face of the perimeter wall on the south side of the Fort. Here, a hole, 1.65 long x 1.60 high x 0.88 m deep, had been dug in recent times by robbers to obtain the bricks. This gap was cleared of dust and loose debris and the local mason, Abdullah, began filling the hole with new bricks on February 12, 2005. The last three courses were completed two days later to see if there were any problems with settling or shrinkage. No measurable movement was observed (the foundations here were still intact), so the last of about 200 bricks were put in place to complete our first structural repair. By choosing a gap bounded on all four sides by original brick, we were able to test brick size (they did fit correctly within the ancient courses), mortar composition (not too wet, not too dry), logistics (the realities of following the ancient laying pattern and wall batter), and drying time and settling, Finally, there's appearance--will the color and laying pattern be what we ultimately want? We'll have to wait and see.
Aside from teaching us many things, this repair will prevent further erosion, improve the appearance of the monument and more importantly, make a statement that further mining of the walls will not be tolerated. Guards have been posted to enforce this.
Next we moved eastward along the south wall to the first of the series surviving pilasters along this protected face. Uncovered 100 years ago by Garstang, these pilasters are the Fort's best-preserved examples of original architecture and finishing touches (some still preserve the original mud render and white plaster coating). Although archival photographs from 1934 show that pilasters once appeared all along the south wall, those at the east end have since disappeared leaving only scars in the facade. The lower part of the pilaster in question had fallen away and it was soon going to be joining its neighbors to the east. So in 1998 we constructed a temporary buttress to support its remaining upper masonry. It was satisfying to finally repair it more permanently and interesting to observe just how these decorative pilasters were constructed.
The broken area allows us to see that the raised brickwork was anchored to the wall by a series of header bricks that jutted out from the wall surface for half of their length. These occur in every third course and this course is always laid in stretchers. Thus the size and placement of the pilasters were integral to the design and construction of the walls from the beginning, but the pilasters serve only a decorative purpose. The anchoring bricks provide the only bond as the other masonry of the pilaster only abuts the wall facade and this is part of the problem. If the foundations are compromised or some of the anchoring bricks are lost or damaged, the remaining headers are not strong enough to support the weight of bricks above them. In the case of this pilaster, when the lower part failed because of weakness in the foundations, the anchor bricks were snapped in half. In order to rebuild the pilaster, the broken ends (4 in all) were successfully removed and replaced. Reconstruction then followed the ancient brick pattern.
The appearance of the pilasters in this well visiting location is important for a full appreciation of the monument and this experiment tests the aesthetics and durability of repairs to decorative elements. Now we will consider whether the sharp corners of the new bricks should be shaved down to match the condition of the remaining original brickwork; or whether time, weather, and careless visitors will do that for us.
|Left, the pilaster during repair. The four anchor bricks have been removed (Richard Jaeschke). Right, the pilaster after repair. Will the edges of the new bricks need to be shaved down, or will time and careless visitors do it for us? (Jim Rossiter)
Next it was on to the north face for a different experience. For millennia, the north face of the Fort has been blasted by the prevailing wind. A repair here would be a true test of the weathering capacity of the bricks and mortar, so we decided to try it. Subsidence and corbelling in a long, low undercut 6.3 long by 0.95 m deep threatened the survival of this section of the north wall, which is still full-standing. Prior to repair, the lowered ground surface (30-50 cm below the foundations of the wall) and a hole in the underlying hard silts had to be filling with compacted soil to make a strong and level foundation for the new work. We found that the soil we had collected from the fossil Nile terrace location for brick making compacted well and worked wonderfully for this type of foundation work. Its ultimate utility in brick making remains to be seen, but we have found an excellent use for it now.
Unprotected exposure to the prevailing north winds means that very little original surface survives on the enclosure's north face. In order to stabilize this area, the brick repair was extended out and up only so far as to make it flush with and a support for the best-preserved surface on the upper portion of wall. In the end, that amounted to a repair more than 1.5 m high and has raised further questions regarding appearance and technique, with which we are still grappling. Because we did not build the new brickwork out to the original face of monument since it no longer survives, it was impossible to follow the original laying pattern using whole bricks. Instead of stacked headers, bonded stretchers were laid. In addition, the area in need of filling was relatively shallow and any reconstruction less than one brick thick would be too thin to stand or provide support. There are many locations around the monument where wind erosion has shaved off a row or two of bricks, so this problem is not an isolated one. If we had reconstructed the wall to its original surface (remnants of the mud plaster that had run off of it during some ancient rain storm were still preserved at ground level), where would we stop? Do we make an unsightly "shelf" somewhere or do we continue up the entire 9 m of the wall, encasing it in new construction? Neither option was appealing, as the purpose of our work is stabilization, and not reconstruction. The ultimate appearance also remains a concern and we must wait and see whether the repair bricks should be feathered in or distressed to fit in more naturally with the ancient walls, or whether wind erosion will make this unnecessary.
No one said it would be easy. However, we are quite happy with the ingenious repairs made to the remaining segment of the perimeter wall along the west side. This section of perimeter wall was so badly undercut that light could be seen at the base. This wall was going to collapse at any minute. The ground level on all sides falls away sharply to over 1m below the wall foundations causing active subsidence. Levelling of the full area around this wall would have required a large amount of soil, so we decided to create retaining walls of fired brick, in essence, a box or casemate about 7 x 3.5 m to surround the wall segment on all sides. This box was then filled with compacted soil to create a hard and stable foundation for the repair. Fired brick was chosen so that in future the casemate will not be mistaken for ancient construction. One the foundations were strong, we made repairs to both sides of the wall. On the interior face, the original surface was preserved, but on the exterior this was not the case so again we built up and out only as far as necessary to support remaining ancient brick. Following the repairs, the fired-brick retaining wall was banked with soil both to support it and hide it. The severely lowered ground level all along the western side of the monument will eventually need to be raised (for a distance of over 30 m!!). This initial experiment will test the suitability of the fired-brick casemate construction for this purpose. In the coming season, we will check the fired-brick walls for cracks and shifting. Fingers crossed! If it works, we should be able to make substantial progress in rescuing the Fort quickly and with a minimum of expense.
||Perimeter wall repaired. Now we wait and see...|
As for other parts of the monument, until the optimal brick is devised and created in great quantity (repair of the west wall and its structurally important corners is estimated to require more than 100,000 bricks!), there wasn't much we could in the way of a permanent fix. However, we were able to buy the Fort several more years by revving up the sand-bag machine.
Despite our best efforts, burlap bags just weren't available, so we settled for several 1,000 plastic weave sacks that were hand filled, hand sown, and delivered by donkey cart (the walls are too fragile to withstand vibrations from a pickup truck) to support the southwest (see week 2) and northeast corners.
||Donkey cart delivery to the Northeast corner. Sand bags were delivered by donkey cart because of the fragility of the walls and their sensitivity to vibrations of cars or heavy machinery.|
The loss of the northeast corner was a recent catastrophe. It collapsed in 2002. The corner was already weakened by a deep hole at its base and corbelling at foundation level, but it is suspected that unsupervised geological research in the vicinity was the final straw. The failure of the lower part of the north face revealed the first phase wall to its full height of 2.3 m but created a dangerously unprotected overhang of masonry above. Major cracks were developing in this upper masonry and it was clear that without support, more of this corner was going to collapse very soon. There was no time to waste. First, we had to remove the pile of fallen bricks and, like everywhere else, raise and reinforce the ground surface. On this strengthened surface we began to build a buttress of sandbags 2 m wide and 4 m high to support unstable sections of the upper wall. A slow and laborious task, but it too taught us important lessons in the art of sand-bag buttress construction and a new-found respect for the difficulties faced by all conservation projects throughout the globe.
In fact, all of the repairs are teaching us something as we prepare for the big fixes. The ever-growing gap in the middle of the exterior west wall is one of our biggest worries. About 15 m long, 2.5 m high and growing, but thankfully still only about 1.2 m deep, this giant wound is a major threat to the survival of the Fort. Since the ground surface here is about 1m below the footings of the wall, this gap just gets larger and larger as more bricks succumb to gravity. If the breach gets any deeper, it will meet up with the deep cavity that has been excavated into the wall on the interior. Right now, we have a thickness of about 1.5 m of brick holding it all up--not a lot to balance on--and we can only fix the interior after the exterior has been stabilized. So, we need to raise the ground level, strengthen the foundations, make a lot of good bricks (we estimate we will need more than 14,000), work out the logistics and get busy! We hope to get started in November 2005.
Permanent repair of the major gap in the center of the west wall is estimated to require more than 14,000 bricks.
It's a big job and it will be expensive. We are extremely grateful to the World Monuments Fund for their support of the current work. We also wish to thank ARCHAEOLOGY; the LaSalle Bank, Chicago; Tom and Linda Heagy; David and Crennan Ray; Larry and Renée Stevens; Courtney Taylor; James and Jeanne Manning; Francis Ahearne; Rikki Breem, and our many Friends of Nekhen for their generous donations to the Fix the Fort Fund. You, too, can help us help the Fort by becoming a Friend of Nekhen--see www.hierakonpolis-online.org.
The accomplishments of the first campaign to fix the Fort. View toward the northwest corner. (Jim Rossiter)
It wasn't all sand, bricks, and mortar down at the Fort. Between deliveries from the donkey cart we were able to examine the structure in more detail and use many of the insights gained during the repairs to gather new facts about this neglected monument and begin a preliminary reconstruction of the Fort and the Fort within the Fort. Coming soon in "Fort Facts," we will share some of the new things we have learned and wish to investigate further.