Minimal Settlement under 18^th Century Jaipur City Gate

Quelle/credit (2): Robbins

The historic Chandpol Gate of Jaipur, built in 1727, sits directly above the new Jaipur Metro line

Quelle/credit (2): Robbins

Contractor CEC opted to refurbish their two Robbins EPB originally built for the New Delhi Metro (original machine build pictured)

Quelle/credit (2): Robbins

The first EPB was launched using umbilical cables from a small jobsite in May 2015

Quelle/credit (2): Robbins

The tunnel alignment to Chandpol Gate

The overburden at the Chandpol Gate section is only 4,5 m

Quelle/credit (2): Robbins

Muck begins to roll off the TBM conveyor – ground consists of mostly silty sand above the water table

Quelle/credit (2): Robbins

Quelle/credit: Robbins

The Robbins and CEC crew, pictured during the first TBM launch in May 2015

Quelle/credit: Robbins

Jaipur, India’s tenth most populous city, is a cultural melting pot of 6.6 million people. The city’s heart is encircled by a wall six meters high and three meters thick, with seven gated openings. Built in 1727, the walls and many of the old city streets were painted pink and remain so today, giving Jaipur the nickname of the “Pink City”. It is below these delicate and iconic structures that Jaipur’s first Metro, Line 1, will travel. The above-ground Phase 1A runs 9.63 km from Mansarovar to Chandpol Bazaar with nine stations, and was opened to the public in June 2015. Phase 1B is tunneled and consists of 2.3 km and two stations running below the walled center. The completed Line 1 is expected to open to the public in 2018.

Geology and Gate Structures

Chandpol gate, one of the seven, is directly above the bore path for the Line 1 extension, and serves as a historical landmark (Fig. 1). Contractor Continental Engineering Corporation (CEC) was tapped to excavate twin tunnels 2.3 km in length with a 5.8 m inner diameter. The alignment of the tunnels traversed geology that can be generally divided into two types. The first type is composed of a mixture of silty sands and the second type of silty sands with minor quantities of clay and gravels. Based on the observed N-values, which are greater than or equal to N = 41,...