A project should be studied keeping in view all aspects such as structural engineering, geotechnical engineering, and building materials

The collapse of a wall in M.J. Colony in Moula Ali, Hyderabad, where six people died, is a classic example of deep excavations done without following the norms of civil engineering. Reasons ranging from rain water seepage to nature of soil contributed to the tragedy which could have been avoided.

During heavy rains, rain water gets into the void space of soil which reduces the sheer strength of soil and increases water pressure.

Due to this, the soil behind the wall gets saturated and develops pore water pressure which increases lateral pressure on the wall in addition to the existing soil pressure, for which the wall might have not been designed.

In this case, height of the earthen back-fill was more than the height of the wall, and the wall itself was constructed with clay or soil mud as binding material, and not cement mortar. The binding material might have lost its strength leading to failure.

Digging of foundations adjacent to existing buildings causes harm to the foundation of the existing structure and the structure may collapse immediately or create distress in future.

Keeping the above in view, a few factors need to be considered and precautions need to be taken while executing the construction work for the immediate and long term safety of the structures.

A project should be comprehensively studied keeping in view all engineering aspects such as structural engineering, geotechnical engineering, and building materials. A complete project report with detailed investigations and phases of execution need to be prepared before initiating the construction.

Rectifying the errors during or after execution is very complicated especially when it comes to foundations, as they will not be available for inspection and repair or rectification. All designs and geotechnical investigations need to be entrusted to a well qualified and experienced team. Alternatively these works can be carried out by available organisations, but the structural design and the geotechnical investigation reports need to be vetted by qualified and experienced organisations for implementation.

It may be noted that failure of foundations is dangerous and there is very little scope for rectification later.

Further, foundation failures may not be observed immediately but they begin to show their ill effects in due course of time. For example, a residential apartment in Kakinada town showed cracks three years after occupancy.

In a number of cases, it was observed that the soil investigations were incorrect or wrongly interpreted. This has to be seriously examined. It is therefore necessary to get soil investigation done by competent body and reviewed by qualified people, before the project gets approved.

Prof. E. Saibaba Reddy

Professor of Civil Engineering,

JNTU, Hyderabad.