REASONS FOR DOING MICRO PILING AND NAILING WORK

The construction of new PuttannaKanagal theatre and multi-level parking facilities at Jayanagar 4th block, Bangalore consist of 4 blocks ie., Block-1,2,3 & 4. The site is situated in centre of commercial area with high density of vehicular traffic and also pedestrian. The construction of Block-1 was taken up in first face by dismantling of existing old PuttannaKanagal theatre building and it is a rehabilitation block for the existing vegetable market, Janata Bazar &Canara Bank. The proposed Block-1 building having Lower basement, Upper basement, Ground & 6 floors.The Block-1 has got the following constraints.

a. On the Northern side existing Tower block comprising Ground floor and 12 floors.b. On the Eastern & North western part existing building comprising Ground floor & 2 floors.c. On the Southern & Western side having high density traffic road for 24 hours.d. The depth of excavation for block-1 all-round the building is 11mt with vertical cutting and the working area is constrained.

During excavation, it is observed that the existing tower block on Northern side has independent footings below 1.50mt from floor level. The excavation line of Block-1 on Northern side was 4.00mt from the existing tower block. The block-1 excavation depth was 11.00mt from the ground level and the level of lower basement will be 8.00mt down from the existing tower block floor level. On Eastern side, there exists a 3 storyed building and the distance between the Block-1 foundation line & 3 storyed building is 2.00mt only. Similarly on the westeren side of Block-1, there is another 3 storyed building. The existing building line on the edge of the Block-1 foundation line. That means there is no space between the new building line (of Block 1) and the adjacent 3 storyed building. On Southern side & part of Western side is having the main road with high density traffic flow in 24 hours and the foundation line of the Block-1 is on the boundary line of the road.

The above points were discussed with the then Engineer Member, BDA and he advised to take a technical opinion from Professor. B.R.S.Murthy regarding the safety precautions for existing tower block, since the foundations for the proposed Block-1 & 2 is going deeper and excavation may be required to be done upto 10 to 13.00mt from the ground level of the existing tower block.

As requested by BDA officials, Pro. Dr.B.R.Srinivasa Murthy from Indian Institute of Science visited the site on 07.11.2012 & 01.12.2012. Professor, B.R.S.Murthy gave the technical reasoning that in the ground, as there is no space between the existing tower block and the foundation line of the proposed new block, the new retaining wall construction along the boundary will not serve the purpose and the load distribution factor for existing tower will satisfy only if the foundations (Earth) below the existing tower are strengthened and stabilized locally. The angle of repose arising out of existing tower will fall within the foundation line of the new proposed blocks and may result in tilting and collapse of existing tower. For doing the strengthening and stabilizing of the soil below the existing tower block, the method of Micro Piling with nailing work upto a depth of 10-12 mtrs is essential on both directions.

During the execution of nailing work, the excavation was done in 1.00mt depth in each stage and necessary shoring and strutting was carried out against earth collapse at that point of time during the course of excavation.

The above statement clearly states that the micro piling and nailing work was not done for the safety of excavation or execution. It is done purely for permanent protection of the existing tower block & heavy traffic road and entirely on technical grounds as suggested by Prof. B.R. Srinivas Murthy.

While doing excavation for micro piling and nailing works, the payment for the work of shoring and strutting which was done during stage wise excavation, were not paid because it is included in the earth work excavation item.

The Micro piling and nailing is a specialized work, done after discovery of the foundation level of the existing tower. At the time of estimation and tender the foundation level of the nearby structure was not known either to BDA officials or to the contractor. Hence it is not right to expect contractor to imagine micro piling and nailing at the time of tender. It is work arising as per the site condition discovered after the award of work. Hence it is clearly constitute as extra item and regulated accordingly.

In view of the above facts and reasons, we request you kindly consider the above facts and drop your observations made vide Para No.5 of Audit Enquiry No.10, Dtd.20th Dec2013.

Page 3 of 3