TUNNELS (Part - I)
PART 1:
Introduction
Tunnel Geology
Tunnel Investigations
PART 2:Tunnel Excavation Methods
Tunnel Supports
PART 3:Tunnel Grouting
Tunnel Instrumentation
Tunnel Safety Instructions
Introduction
Pakistan is a mountainous country, and about half of it is covered by mountains. Our northern area is fully covered by low and high hills belonging to mountain ranges, like Haramosh, Hindukush, Nanga Parbat, K2 and Pamirs etc, while in the south there are main mountain ranges like Ras Koh, Kirthar, Koh Sultan and several other mountains around Quetta. Many people live in these mountains and hills.
In the north their huts and houses exist mostly in the valleys along the nalas or water streams wherefrom they get water, and some have made their houses on the top of hills. However in the south the conditions in most areas are desert like and water facilities are only remotely available.
In the north their huts and houses exist mostly in the valleys along the nalas or water streams wherefrom they get water, and some have made their houses on the top of hills. However in the south the conditions in most areas are desert like and water facilities are only remotely available.
Talking of water facility in the desert areas,a passing remark here about the part of life the presenter and the staff experienced at a project. It was by getting the water from a long distance away, from a karez and sometimes when on return the vehicle or the water bowser bogged down in the desert, it remained there for days and the workers went without water, sometimes, for a couple of days. Imagine remaining without water in 59 degrees centigrade temperature in shade, in summer months.
Inside their living areas the people use the tracks for going from one place to another, but they need roads to go out of their areas or living places, may we call their hutments as small or large villages. Any how they require roads for traveling to far off places for bread earning, for serving somewhere or doing business. The requirement of roads therefore is very essential for them. The road building in such areas is very difficult, as hills, nalas and larger water streams, like rivers have to be crossed by building versatile bridges and cutting of steep slopes.
All the rocks and the hill slopes are not friendly to roads as there are numerous weak rock locations, high and sometimes, near vertical slopes. To take better care for such adverse situations a lot of expenditure has to be made to cater for the road construction in these circumstances.
Some arrangements have also to be made to guard against the imminent dangers of landslides. Specially in the north another hazard is created by the slipping of accumulated snow from the steep slopes in winter, in the form of avalanches.
This slipping of snow is triggered by any vibration or even the talking among people crossing the snow on the tracks below can result in the development of an avalanche. The speed of an avalanche is more than 200 kilometers per hour. Many precious lives are lost every year due to these avalanches, especially in our northern area.
Snow galleries with sloping roofs can be constructed above the roads, the snow from the slopes can slip away on these roofs and fall in the nalas along the roads. This is where the avalanches are not serious danger.
In addition to the snow galleries. Half tunnels have also been made on the gilgit – skardu road by which the small landslides can also be negotiated.
But these half tunnels can only be made in stable and good rocks, and should be well supported as required.
There are several places in the hilly areas or these can be located where underground passages can be built to avoid the landslide sites and provide safe journey to people.
Therefore the knowledge of tunneling through the mountains can help to plan safe communication and transportation of stores and human lives
Before Pakistan came into being several underground passages or tunnels had been made for railway trains and a few road tunnels had also been excavated.
The Kohat Tunnel has recently been constructed for ease of traffic in the vicinity of Kohat city.
During the last 40 or 50 years, in Pakistan we have provided and excavated tunnels for several dam and other projects like, Warsak, Malakand, Mangla and Tarbela dams and power plants for conveyance of water to the plants for power generation or to spill extra water from the reservoirs back into the rivers.
This 40 or 50 years comprehensive tunneling experience, gained by the pakistanis is enough to have attained an expertise required for planning and executing tunnel projects, any where and in any type of rocks.
This expertise can be utilized for the development of tunnels and other underground construction works in our country.
In 1973, a large road tunnel project, the Lowari Tunnel, through the Lowari mountain, was taken up for construction, in order to provide safe journey to the inhabitants of Dir and Chitral. Here in this area, for years, men and stores including the transport animals have been engulfed by the avalanches and the planned tunnel could really be a boon for the people, but after the excavation was taken up two years later, the government due to fiscal restraints could not continue with the project, and the work was stopped in 1977
However now after a long lapse of time National Highway Authority has closed in on the preparations of excavation of Lowari Tunnel which has already been started.
The last year’s earthquake disaster of Azad Jammu and Kashmir and part of Hazara, which damaged the personal properties and resulted in the death of thousands of families and their kids also affected the entire road network and therefore, initially the approach for provision of help in the area was delayed. Keeping this situation in view, it is all the more important to acquire the tunneling technique to plan and construct underground passages or tunnels, where required.
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