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The Shimla Bypass Tunnel Project is being built by the National Highways Authority of India, extending 27.4km around the city of Shimla. It comprises of multiple tunnels, bridges and culverts constructed in geologically sensitive Himalayan terrain, where complex rock formations, fault zones and proximity to inhabited areas demand careful construction planning.
A substantial portion of the tunnelling works has been executed using the conventional drill鈥慳nd鈥慴last method supported by the New Austrian Tunnelling Method (NATM), which allows flexible support measures based on observed ground behaviour. Despite the name, NATM was developed in the late 1950s, and is now well established in tunnelling.
While NATM remains well suited for variable Himalayan geology, restrictions on blasting in certain tunnel sections鈥攑articularly near populated zones鈥攃reated challenges related to vibration control, safety compliance and construction timelines.
Epiroc's equipment was supplied to Bharat 萝莉原创s (India). The equipment manufacturer conducted a detailed technical assessment and recommended the deployment of its HB 3600 DP hydraulic breaker. The breaker was introduced as a controlled, non鈥慹xplosive excavation alternative capable of maintaining excavation progress where blasting was restricted or temporarily suspended.
Several technical adaptations were implemented to ensure suitability for underground operation, including adjustments for tunnel clearances, working cycles and continuous duty conditions. Following commissioning and a short stabilisation period, the breaker delivered consistent and precise rock excavation, supporting steady tunnel advance without compromising safety or regulatory requirements.
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