Page 48 - CO April 2017 Full Issue

CASE STUDY COVER STORY Powered by The CC30 package of DMRC is part of the 59 km long Majlis Park to Shiv Vihar Metro Corridor (Pink Line) of Phase III. The scope of work included design and construction of the twin tunnel between Shalimar Bagh and Subhash Place stations by Shield TBM, twin box tunnels by cut and cover method, underground ramp, architectural finishing of Shalimar Bagh station (underground) and Netaji Subhash Place station (semi-underground). Te notice to proceed with the work was transforms it into a fowing material. Tis issued on October 29, 2012 and HCC muck is then stored and is used to provide immediately undertook the detailed support and to balance the pressure at the geo-technical investigation of the project tunnel face during the excavation process. along the alignment of the project. Te Te CC30 package orientation is north- soil was tested by drilling boreholes at nine south with Shalimar Station located on the locations and samples extracted were tested northern end and an underground ramp on in the laboratory. Te detailed investigation the southern end of the project. Te northern revealed that the soil along the project boundary of the project is shared with CEC alignment was sandy silt and silty fine who is working on DMRC’s CC04 package sand primarily. It was medium dense to and on the southern boundary where L&T highly dense at the depth of 30 meters. Te is working on the elevated corridor package ground water was encountered at about 11 of CC28. to 15 meters depth. Te geology along the alignment of the tunnel was of mixed type. the tunnel with the discharge rate of the Construction sequence (graphical representation of the geology). excavated soil. Te Shalimar Station location was the frst Based on the geo-technical study done by Te underlying principle of the EPB method area handed over to HCC for work. It is a DMRC during the tender stage, Earth is that the excavated soil itself is used to complete underground station and goes up Pressure Balance Tunnel Boring Machine provide continuous support to the tunnel to 30 meters deep. Afer barricading the was finalised for the tunnelling. Earth face by balancing earth pressure against the area, underground utilities shifing was the Pressure Balance (EPB) TBMs are used in forward pressure of the machine. Te thrust frst task undertaken before commencing excavation of sof ground or soil condition. force generated from the rear section of the excavation work. First the 1500 mm The EPB method consists of cutting TBM is transferred to the earth in the cutter diameter PSC pipe line and MTNL Lines chamber located behind the cutter head of head chamber so as to prevent uncontrolled were shifed, afer which the electrical lines the TBM. Tis chamber is used to mix the intrusion of excavated materials into the of 11 KV and 33 KV were shifed. Prior to soil with water foam. It is maintained under chamber. When the shield advances at the shifing, the permissions from TATA Power pressure by the mucking system. Te ground face of excavation, the excavated soil is then Delhi Distribution Ltd. were taken. at the cutting face is supported by earth mixed together with a special foam material Shaf location next to the Netaji Subhash pressure by balancing the advancement of which changes its viscosity or thickness and Place station on the southern part of the 50 construction opportunities|aPrIL 2017