TUNNEL BYPASS FOR DELHI
Author : Dr. A K Dube
SUMMARY
Delhi, the national capital territory attracts vehicular traffic from neighboring states as well as indigenous one, which is very high as compared to other cities. Such a massive traffic needs to be managed within the city and to be diverted away from the congested areas. A 93-KM long peripheral expressway is under consideration, which may help in easing the traffic congestion within the city and bypassing the interstate traffic. The idea is in the formative state at present. An alternative tunnel by pass is proposed which may serve the intended purpose. It is much shorter and being mostly underground avoids the land acquisition, which may be needed as a right of way for the exoressway. It is competitive price wise and appears to be an alternative worth considering. The tunnel alternative will result huge fuel saving, reducing travel time considerably. Aravali rocks exposed in Delhi may provide good tunnelling media.
INTRODUCTION
The national capital territory of Delhi has a population of over fourteen million and it is growing very fast. Delhi being the capital of the country attracts many people from the neighboring states and the country as a whole, besides visitors from abroad. The people move in the motorised vehicles due to lack of adequate and efficient public transport system. Most persons, therefore, use personal transport and due to this Delhi has a population of three million motorised vehicles, a number equal to all the vehicles plying in Mumbai, Kolkata and Chennai put together. So large a vehicle population, coupled with varieties of slow moving vehicles like tongas, ricksaws, animal drawn carriages, cyclists and the pedestrian in a hurry is a real nightmare for any traffic planner and manager.
The authorities are grappling with the problem and are seriously thinking to have a Delhi by pass to regulate inter state through traffic, which has to pass through Delhi. Further goods traffic is to be provided regulated entry channels to the wholesale market of the city. The heart of the city has whole sale markets, godowns and offices of transporters including the vehicle parking space. The city planners would generally like to regulate interstate traffic so as to have integrated passenger terminals and freight complexes on the periphery of Delhi. This will help in decongesting the interior of Delhi so that the traffic scenario can be improved, besides diverting the interstate through traffic. The peripheral expressway is on the cards, which may meet; the present day traffic needs, reduce congestion, bypass the interstate traffic and finally help in reducing the pollution.
THE EXPRESSWAY UNDER CONSIDERATION
The proposed expressway (a bypass) is now at a very elementary stage of planning. It may possibly be over 90 Km. long and may have a divided carriageway accommodating two to three lane traffic in each direction. The access to the expressway would be controlled and slow and fast moving traffic may be segregated. The expressway may not have any intersection at its grade. This will greatly help in easing the traffic and reducing pollution.
The expressway may be so aligned to avoid any dislocation of built up areas and sensitive defense as well as archaeological monuments. The planners also hope to ensure minimum environmental disturbance.
The express way may also link the towns of Faridabad, Noida and Ghaziabad. This expressway to be a reality must have the blessings of the state Govts. of Delhi, Haryana and U.P. the scheme being a major work of interstate nature. It is currently being examined at various levels and may be approved later if the participating oraganisations converge to the idea. The expressway may need a right of way as wide as 150 metres throughout its length. The land has to be acquired which is a long drawn process involving delays and litigations. Probably this may be the biggest stumbling block and may require an appropriate strategy.
The expressway will need an investment of Rs.2500 crores, and therefore it may be difficult to mobilise so much of resources. The financial institution may provide funds for the scheme, which may have to be undertaken on BOT/BOOT concept. Such finances can only be possible if the scheme becomes a commercial venture. West Bengal, the bastion of socialism, has given a lead in building the Vidyasagar setu as a commercial venture. The recently opened NOIDA Toll bridge is another example. The planners feel that the land around the proposed highway can be put to best commercial use. The truck terminals, bus terminals, godowns and passenger facilities like restaurants and neighborhood-shopping complexes may yield some revenue besides the toll collected from the users. The financing the land acquisition and finally the viability of the venture depend on a very careful study of the financing options.
THE UNDERGROUND OPTION
The over grown metropolises all over the world face immense problems in managing their transport needs. The developed countries adopted under ground mode of development wherever they faced the space crunch. The advent of London tubes in the year 1863 opened a new chapter in the history of man- kind. The years after that started a race for use of underground space for various uses, and today the visionaries of the developed world are planning to have integrated townships below the ground to ease the congestion on surface. People find the underground space safe, economical, environment friendly and affordable.
OUTLINES OF THE SCHEME
Before the idea is actively considered, we may have to answer many questions like the possibilities and opportunities of going underground. What can be the most preferred alignment? From where the entries and exits be made and whether the land is available at these places. Besides this the traffic using the by pass has to be evaluated and a most viable and appropriate plan is to be developed. This is a part of further study, which may have to be undertaken. The entries and exits cannot be made anywhere because we need reasonable space and good rocks for the purpose. Fortunately, Delhi has good exposures of Aravali rocks, which are good for tunnelling. A thorough feasibility study may therefore be needed to conceive several possible alignments with respective exits and entries. A thorough analysis will be done after the study to develop most efficient routing ensuring the proximity of Aravali rocks.
At this stage we can only draw prima facie a probable alignment. This underground traffic bypass will start from Timarpur (See Fig. 1) Having entry and exit for NH1.There will be two 10 metre wide tunnels running parallel to each other. These tunnels will have a 20 metro wide separation of rock. The width of the tunnel is good enough to allow two-lane traffic. The tunnels may pass below Karol Bah area and here it is possible to provide entry and exit for NH 10.Further comes the Dhaulakuan area where entries and exits can be provided. The tunnels further connect R.K.Puram where entries and exits can be provided for in coming and out going traffic. Surface or underground route to NH 8 can also connect the exits and entries here. The tunnel alignment further passes close to Nehru Place area. Here also exits and entries can be established. These can also cater to the traffic generated at Nehru Place and its surroundings. The tunnels finally meet the NH 2 near Sarita Vihar. The total distance traversed by twin tunnel system will be 21 km. The ramps for entry and exit, about 10 to 12 in number may account for another 8 km additional tunnelling. Thus the total length will be 50 km of tunnel work.
The entire alignment has been fixed in such a way that it passes through the good rock formations of Aravali rocks of Delhi systems of rocks. The tunnels must have a minimum rock cover of 20 metres. The entry and exit ramps may be 800 to 900 metres long so as to maintain a grade of at least 1: 30.The entries and exits may have to be made partly by cut and cover method so as to reach the firm rock to sustain tunnelling. For any underground project the most critical area is the entry, as it has to be through long ramps. Once we reach underground there is enough freedom to expand laterally. The expansion may be in the form of parking lots, shopping malls, storages, godowns and underground transit facilities for passenger and freight traffic. These may open up another opportunity for revenue generation for which no land is to be acquired.
DELHI ROCKS
The Delhi region comprises of extensive, almost flat plains interrupted by a long rocky ridge (Delhi Ridge) rising sharply from the plains and tending NNE-SSW (Fig 2). The Delhi Ridge is the northern culmination of Aravali range. Towards the east of the ridge is Yamuna River and on the west lies the natural depression of Najafgarh. The quartzite ridge enters the area from southwest part and expands into rocky land towards the eastern part, finally disappearing below Yamuna alluvium. The land surface on the eastern side of the ridge slope towards river Yamuna with a general gradient of 3.5 metre/km. The greater part of Delhi State lies in alluvium bed. Small hills and ridge in and around New Delhi consist of Alwar quartzites belonging to Delhi system.
The Yamuna River enters the region from north of Delhi at an elevation of about 216 metres and leaves it at 198 metres above the mean sea level. The elevation of the crest of the ridge varies between 213 to 340 metres above mean sea level which is about 15 to 122 metres above the surrounding plains. The alluvium plain in the area is almost flat and interrupted by cluster of sand dunes and quartzites exposures. The quartzites of Delhi system are mostly medium to coarse grained and with the presence of flaky minerals. Few quartzites have foliated appearance. The exposed quartzites are generally weathered near the surface creating a heavily jointed structure, whereas the fresh rocks are comparatively less jointed. The study of isolated exposures in the area revealed that the quartzites are hard and thickly bedded. They are dipping steeply but are variably dipping eastwards in some leading to the conclusion that there is folding of the rocks in the area. The quartzites are white, pale grey or pinkish purple in colour. The weathering of Delhi quartzites is very conspicuous due to the mineral composition and the jointed nature of rock mass. Shear zones are also present and at places pegmatite veins are found intruded locally. The rocks generally strike NE and the angle varies between 5 to 35 degrees.
The rock exposures have been examined at some places and their geological characteristics have been examined. The quartzites are very much jointed with at least three prominent joint sets often leading to sugar cube like structure. Various random joints are also present and at places producing a highly jointed structure. The bedding joint sets are striking approximately NNE -SSW are most dominant and are spaced between 0.6 to 1.0 metres. The other joint sets are at right angles to bedding joint. In the Mehrauli area the geology is similar to the above location except the fact that there is no pegmatite. The quartzites here are massive to blocky with well-developed bedding planes. The quartzites are grayish to brownish in colour having coarse-grained texture with prominent crystals of quartz. In the vicinity of JNU and Nelson Mandela marg the rock exposures are entirely quartzites associated with bands of schists and are intruded by pegmatite bodies along with structural discontinuities, The quartzites are grayish to brown in colour and are fine to medium grained. At the contacts with pegmatites intrusions it is much coarser and friable .The quartzites are generally massive in nature and are hard and crystalline. These rocks are generally unweathered and massive having only bedding joints and some random joints. The bedding joints are spaced at places more than one metre to less than one metre. Joint walls are intact and planer with slight weathering or alteration. The joints generally do not have filling though occasionally quartz veins are found at a few places. The bedding planes in the area revealed that the quartzites have undergone folding and the ridges in the area form the limbs of the folds.
GEOTECHNICAL ASSESSMENT OF ROCK MASS
A limited study of Delhi rocks assure that the rocks are fair to good tunnelling media and may provide fairly competent site for safe and economical construction of the underground bypass. The following rock mechanical characteristics may support the above statement.
1,Rock mass quality (Q) -0.87 to 9.00
2,Estimated rock pressure range- 0.30 to 0.85 kg. Per cm.sq.
3,Rock mass rating -50 to 77
4,Modulus of elasticity of rock mass-10 to 54 Gpa
5,Cohesion- 200 to 400 Kpa
6,Angle of internal friction-25 to 45 degrees
7,Stand up time min. 1 week for 5 m.span and max.1year for 10 m. span
The above values are very general and there may be a need to generate more data during the preparation of detailed feasibility report.
ENVIRONMENTAL ISSUES
It is a major project to be under taken in a city having thickly built up area and conscious citizens. The environmental issues are mainly pertaining to the construction work and some disturbance caused due to land acquisition for portals and service space near them. There may be a fear of some damage caused to the ridge, this being regarded as a very important feature of Delhi considered by environmentalists. This can be allayed by detailed study of environmental impact assessment and evolving appropriate environmental management plan. About four million cubic metre of excavated rock may be generated. The rock material is a very good building and road construction material, which may have a ready market in Delhi and its surrounding areas where lot of construction activities are going on. The excess material if any, can be used for road embankments and making bunds along Yamuna for flood protection.