Precast method of construction is a very useful way of building structures within a short period of time. The technology is used for buildings and engineering structures like highway bridges. For any of these constructions three issues are required - accurate casting, proper lifting, transporting and efficient system of binding all elements.

If the casting is not done properly the whole process goes a waste. As I observed at Cauvery junction and BDA intersection lifting of elements was not done properly. It requires efficiency. A small mistake can cause major damage to the entire structure. I have seen photographs of cracks developed in elements carried in the media.
Binding elements is very important. As I saw elements used at the underpass at Cauvery junction hooks were used to lift them. The same hooks will obstruct perfect alignment of elements. Even a small gap between elements can lead to disaster. Whenever heavy loaded truck passes over the underpass the gap widens. I feel that the Palike should have taken more care in binding and lifting elements.
I dispute BBMP’s argument that precast technology saves lot of money. No matter whether Palike follows conventional method or adopts precast technology, the quantity of steel and concrete required is same. Maybe because of escalation in prices of construction materials during the period of construction may end up causing heavy burden in conventional method. But going by requirements of materials there is no difference. However precast technology can save money only when it is developed as an industry when orders for elements are in large number.

It’s raining ideas

Precast technology is good but requires accuracy, says one expert, while the another terms it a “piece meal”
solution to the traffic woes of Bangalore city. A former people’s representative takes serious exception to the technology and the way it has been adopted for construction of the underpass at the Cauvery junction. An expert in rainwater harvesting has come out with a suggestion to have rainwater harvesting apparatus fixed in underpasses as well. The debate continues...

Features of pre-cast elements

4 Carrying capacity: 70 tonnes
4 Designed for life time of 100 years
4 If elements develop cracks, can be replaced




Just a piece meal!

The use of precast RC boxes to create underpasses in a short period of time is an interesting and innovative approach when compared to the normal tedious way of in-situ construction. The argument that these boxes are structurally weak is not valid since the design of such precast structures is well within the capabilities of Indian engineers. Having said that, there is a need to recognise that an underpass is not just a feat of structural engineering and its geometric design can make or mar the success of the design.

It is, however, necessary to observe that the traffic woes of Bangalore are not amenable to piece meal magical solutions. The problem is essentially multidimensional and needs the synergy of several complementary approaches to arrive at a feasible solution. Any approach which does not penalise the four wheeler, which is the crux of the problem, is not likely to succeed. The Government of India and the Industrial sector gloat over the growth prospects of the economy driven by the four wheeler production. Metropolitan India is, however, at the receiving end of this apparent bonanza.

 The frenzied approach of the Bangalore urban planners to create a signal-free corridor to the new airport is at best myopic. The desire to meet the needs of the jet-setting elite at all costs, ignoring the rest of the road users can be counterproductive. If one route in Bangalore is signal free and the rest of the road network is in a mess we can imagine it getting over crowded by everyone moving in that direction. I only hope Bangalore will come up with a group of administrators who can think of lasting, holistic and long term solutions rather than short term knee jerk palliatives.


K S Jagadish
Professor of PG Studies,
R V College of  Engineering (Formerly Professor of Civil Engg, Indian Institute of Science)


LEADER SPEAKS

Don’t give excuses

I have strong opposition to what BBMP has done at Cauvery junction. BBMP has spoiled the entire locality by constructing an underpass. It does not serve the purpose at all. Palike should have constructed underpass on Bellary Road itself instead of digging T Chowdaiah Road. Officers cited hard rock, water pipeline and non-availability of space on Bellary Road as excuses. But that could have been solved easily.

Hard rock, pipeline are not at all obstacles to take up any work. According to my sources, Palike officers did not make any effort to acquire part of Palace Grounds. If it was done they would have constructed underpass right on Bellary Road and that would have solved the problem. Yes I agree the ownership of Palace Grounds is in court. But by filing an affidavit, land could still have been acquired. That was what I did when land was required for Mekhri Circle fly-over.

BBMP officers went ahead with their projects without proper consultation with those who have worked towards improving infrastructure.  Had they consulted ex-corporators, ex-ministers and other people’s representatives this would not have been the problem. Officialdom in Palike is highly egoistic. Unless officers give up their ego and work with commitment the city will have better future otherwise it is going to be hell on earth!

V Somanna 
Ex-minister

Readers’ Remark

The technology of precast RCC frames is very good and should be used appropriately at all scales. The design of these structures will need to involve experienced traffic engineers at all times so that their appropriateness to the traffic situation and the future movement of traffic is maximum.

There has to be an environmental impact assessment done for all parameters. Critically underpasses disturb the soil profile and affect the porosity, conductivity and specific yield of the shallow aquifer wherever they are put. As we all know water is in short supply in Bangalore and the shallow and deeper aquifers need recharge. A proper management of groundwater and storm water will ensure that they are not simply drained away but recharged in appropriate areas to ensure that the ground water table is not affected and is in fact enhanced. Simply because there is no owner for groundwater - neither the BBMP nor the BWSSB have any management idea for groundwater- does not mean that this precious resource is negatively affected, If we plan our underpasses holistically and carefully we can enhance benefits for not only traffic but also water and the environment.


Srikantaiah
 Vishwanath Rainwater Club,
Bangalore


No hurry, wait

Using precast technology for underpasses is a good technology provided it is implemented with perfection. By excavating earth soil structure has been disturbed. During rainy season the loose soil structure may affect the underpass. To avoid that the base has to be strengthened. There is also possibility of seepage in
retaining walls. The BBMP has to take care of that too.

It seems Palike is in a hurry to adopt the same technology at other junctions. I feel that Palike should wait for some more days and study impact of the underpass constructed at Cauvery junction and then take up work at other junctions. Width of the underpass at Cauvery junction is insufficient. If BBMP is adopting the same technology elsewhere it should increase the width.