The second stage of the TTC Wilson Yard Expansion was undertaken to carry out various site modifications, including the expansion of a future subway box structure and modifications to various site services. The expansion of the box structure involved a caisson wall shoring system installed directly adjacent to an existing, operational subway tunnel. The project also involved jack and bore drilling under existing railways in order to re-route utilities on site.
RWH Monitoring (RWH) was contracted to implement a comprehensive monitoring solution to measure the stability of the existing subway structure, the ground surrounding the future interceptor storm sewer, the shoring system for the proposed box structure as well as the ground and railways overtop of the jack and bore operations. The monitoring system consisted of piezometers, electrolytic levels, vibrating wire strain gauges, push-in pressure sensors, inclinometers, barometric reference and surface settlement points. Complex installation requirements were completed throughout the site, including instrument installation inside the operational subway structure in order to accurately measure the structure’s movements in vertical and horizontal directions. This project demonstrates RWH’s ability to manage complex and stringent monitoring requirements in order to protect sensitive infrastructure on a high profile project site.