The tunnelling industry’s main source of work involves meeting the challenges of a growing and urbanising population. Metro projects, sewer projects, water supply projects, telecommunications projects and more all come from this ever-increasing need to make our cities more efficient at coping with their denizens.
Now, starting with a pilot project in Israel, there is one more consequence of population growth that can be addressed through tunnelling: the question of what to do with the dead. The burial challenge is most acute in countries that have both very limited surface space, but also a culture that prefers not to cremate the deceased. Although there are some exceptions to the rule. For example some cities in vast Brazil have already constructed mausoleum towers to house their dead, and the country has expressed interest in pursuing a scheme similar to the Israeli project.
Other, more predictable places have also shown interest including Hong Kong, Spain, Italy and Greece. Greece in particular has incredible challenges dealing with its dead, as the Orthodox Church is strongly against cremation. This has led to the exhumation of bodies as little as four years after burial to make way for the newly departed, and the movement of the earlier occupants to mass graves.
ETERNAL REST
Rolzur Eternal Green Solutions, a subsidiary of Israeli contractor Rolzur Tunnelling has taken on full responsibility for design, construction and mechanical and electrical fit out works of what is possibly the first underground burial complex in 1,600 years.
The project was first imagined during a major study carried out nearly 35 years ago by Technion, a leading Israeli technical university. It was recognised that in the future there would be a shortage of burial space in the country and that underground space might offer a solution to the immediate lack.
The study examined geotechnical matters as well as religious issues; although there are many sects within Judaism with varying beliefs, there is one governmental ministry which is responsible, among other things, for burials within Israel. This office delegates its power to municipal burial societies, burial being a constitutional right – and this office gave provisional approval for the plans.
Arik Glazer, general manager for Rolzur, says that on his journey into Jerusalem during his 15 years in the tunnelling sector, he always passed a mountain covered in graves at the city’s entrance and it always bothered him. “When I heard about this study I read it and prepared initial design and went out to meet the burial society of Jerusalem in order to suggested that we go ahead with the project,” says Glazer.
“We agreed to design and construct a pilot project for 400 graves underneath the existing cemetery, and since then as the project was going so well we have signed an agreement for 22,000 plots.” The project is a 10-year scheme, but work will finish in the space of six years. It is spread over the 10 years for funding reasons – money is unlocked through spending on premium burial spaces and is not available in one lump sum. To this end, Rolzur is an investor in the project with the burial society. Delivery of burial spots will start next year and will end four years later.
THE PROJECT
The site requires the excavation of 300,000m3 of the limestone and dolomite of Har Hamenuchot (meaning ‘the mountain of resting in peace’) of which some 220,000m3 had been excavated as of April. The pilot project involved two 50m-long roadheader excavated tunnels that were 10m wide and 6m high. The main project comprises more than 1,500m of tunnels at maximum 14m wide and 16m high, although the finished height will be 14m when the floor is installed with precast burial spots. The project also called for a 55m-deep ventilation and emergency exit shaft with a cross section of 314m2. This shaft was redesigned to 670m2 in order to accommodate 3,000 burial spots in 15 below-ground storeys. The shaft was excavated through a small garden inside the cemetery. Teams excavated a shaft of 5x7m with D&B in a corner, and later worked with hammers to excavated the rest. The shaft was supported with shotcrete and rock bolts. No damage was done to the cemetery, and the team kept a very tight control on the blasts, working mostly at night with the hammers.
The dimensions of the project are all different as it is not one continuous hall. It is set out over three levels and there are three main ‘avenues’ and seven intersecting ‘streets’ that make up the finished tomb. The intersections form the largest spans. The rock is supported by 4m or 6m rockbolts as well as steel fibre reinforced shotcrete, applied in thicknesses typically ranging from 30-40mm and never dropping below 25mm. Where the rock is particularly poor, steel mesh is applied. As far as Glazer is concerned, it is a fairly typical NATM project from a lining point of view with no real surprises. The geology is understood and investigations are continuing constantly just in case.
For waterproofing, Xypex is being used to protect against rainwater inflows through the roof. The product causes the last layer of the concrete to crystallise if it encounters water. Any severe cracks are being grouted. In all cases around the graves, it is important for religious reasons that the plots have a proper connection to the ground (‘dust to dust’), while also being structurally sound.
In terms of equipment, Rolzur uses its own equipment such as Sandvik MT720 roadheaders, with some limited work by Atlas Copco drill and blast rigs. Shotcreting is carried out with a Sika Putzmeister machine.
FAULTS AND GRAVE TYPES
There have been faults to contend with, and these have been filled with extensive grouting from inside the tunnel (to avoid disruption to the existing cemetery with grout shafts). The faults have mostly been concentrated close to the exits of the structure, so it has been simple to mitigate their impact by slightly altering the end-use plans To explain this, there are several types of grave to be delivered for this cemetery, mainly the conventional type that readers will be familiar with that involves a slab over a floor grave (known as field grave), and also a precast type of sarcophagus also very common worldwide. The precast type was intended to constitute all the graves, but now it will only make up a third. These two types of graves combine concrete and expanded polystyrene. The final type, which is of particular interest, is a type of grave that has not been dug for more than 1,600 years.
This type of niche grave is bored directly into the wall, into the rock of the mountain itself with a special rig manufactured by a small Finnish company (Geonex) engaged by Rolzur. The machine is equipped with a 73mm DTH hammer operated by an HP compressor from Ingersol Rand. These graves were not drilled in the fault zones, but only in the more massive rock. Only the conventional types of graves are being used in the risky areas.
BY THE BOOK
Israel makes use of its own tunnelling codes of practice (Israel 54) which are generally based off the UK and German standards, but for the graves themselves the country had to make use of an earlier code. The “Mishnah” is a codified book from the 3rd century that lists the rules of the Oral Torah and is best known for providing guidance for a Jewish way of life. However, it also contains instructions on burial practice. For instance, it describes that an arm-width burial hole should be separated from the next bore by at least an arm’s width of competent rock, or in the case of less competent rock, more than an arm’s width should be provided. According to Glazer, the engineers think it could be considered the oldest tunnelling code of practice in the world. “It is nothing too unusual,” he adds, “the theological aspects came into our planning at the design phase, but they were solved quickly and early on. It is just like having a few additional bits of guidance, nothing more. Often it is not specific, it might just say ‘look at the rock and see what is allowable’, but this is something the Rabbis have looked at and approved.”
SOMBRE SITE
In addition to the religious guidance to construction, the site is unusually sensitive. “We are working inside an area which, well I have to say it is alive,” says Glazer. “We are below an existing cemetery that has visitors and funeral ceremonies. It is a very emotional time for people and this sometimes slows things down and is somewhat restrictive. We minimise the usage of explosives for this reason, and if people are getting in the way of muck trucks, it is not appropriate to use the horn. You have to be respectful.”
VENTILATION AND EGRESS
Ventilation in the final structure will suck air from the tunnels and out of the shaft, it will be carefully controlled so that it can increase flow in certain areas – for example if there is a large funeral ceremony – and leave others at the background rate of suction. Air inflow will happen through the four entrances at the lower floor level and will not be pumped in, as this is not a typical long, airless tunnel structure. CO2 monitoring has been provided as a precaution, but Glazer thinks this is unlikely to be needed. Additionally, for the first time in Israel, a dynamic signing system will be installed. In the event of a fire, signs will form arrows showing mourners the best route out of the cemetery. This is fully computerised and based on an extensive CFD calculation that Rolzur prepared.
FUTURE
In terms of expansion and future work, as mentioned earlier a number of countries have expressed interest. At the precursor site in Israel, it is possible the site will expand, as additional cemetery construction permissions are easier when you are working on a site that is already a cemetery. Only 1/10th of the mountain has been earmarked for burial purposes so far, and demand is never-ending; nearly everyone we know needs to be buried within the next 80 years. A final thought is that this type of interment is something of a forgotten tradition. In ancient times, burial in tunnels or caves was very common in the region. Readers might recognise one famous story involving the temporary entombment of a Galilean carpenter.
