Strategy of Structural Monitoring of Heritage Structures for Phase 1B for Jaipur Metro – An Overview

Abstract

Construction of metro below heritage sites and dense areas of city poses a complex challenge. Metro construction is proposed in Jaipur Walled City below Chandpole Gate, a world heritage site and within the influence zones of 2500 heritage buildings, 2 world heritage sites and a minaret at varying depths from 4.75 m to 22 m. Alluvium soil is mainly found along the stretch of project. In India, little technical data is available about the consequences of soil settlements, caused by tunnels bored in the vicinity of existing heritage buildings. In case of tunnelling in sensitive locality, monitoring plays crucial role in raising alarms. Considering the horizontal and vertical alignment of TBMs, zone of influence is marked from special 3D analysis. Analytical model indicated no appreciable effect beyond 60 m of tunnel line. Detailed building surveys are carried out to classify into three types depending upon the vulnerability. Structures are attended wherever required and monitored before and during tunneling work. Alarm levels, trigger levels are established for different types of structures. Key findings of pre-condition building surveys along with monitoring methods and preventive measures taken before and during construction work of tunnel are discussed. Regular monitoring is done for cracks, settlements, distortion and tilt. Work also involved archaeological exploration of the chaupads and the careful analstylosis and reconstruction of the chaupads. Two tunnels are constructed successfully. Strategy presented will help engineers and professionals to establish the need for repair or the need to reduce the settlement by modify tunnelling process.