‘Metro man’ E. Sreedharan, speaking to The Hindu, said that instances such as the cave-in on Sunday are likely to happen when the soil is allowed to escape.
“I don’t know what happened on Anna Salai. But generally, if the soil is left to escape from the front face of the Tunnel Boring Machine or the machine is defective or adequate protective measures are not taken, cave-ins may occur. Settlements [of soil] should not occur [during tunnelling],” he said.
Such issues can be avoided if accurate soil conditions are known before tunnelling is carried out, he said.
“Meticulous probing of soil conditions has to be carried out. For instance, there are machines in which the soil quality can be checked when it is inside the machine itself. When the soil is sandy, if consolidation of soil is done by grouting, then it can be avoided,” Mr. Sreedharan said
