ABSTRACT:

The 200 m long water carrying canal tunnel was excavated for passing the main canal of lower valley Wardha project across the railway line and nearby the habitants on the surface. The tunnel width during excavation was at 8.5 m with the finished width after lining at 7.3 m. The rock mass classification approaches including Barton's Q and Bieniawski's RMR was used to classify the rock mass. From these obtained parameters, estimation of unsupported span, the tunnel deformation and the tunnel support pressure were estimated. These parameters were then used to classify the tunnel and estimation of the support requirement including lining. The outcome of these study revealed that the entire tunnel needs to be stabilized by the application of fully grouted 4.0 m long rock bolts of 25 mm diameter and by steel ribs spaced at 0.6 -1.0 m and permanently providing concrete lining throughout the tunnel length. In addition to this, design for smooth wall blasting was also suggested to minimize the blast induced damage and over-break in the tunnel wall. Tunnel was classified considering surface features on the surface and suitable support was recommended.

1 INTRODUCTION

The water carrying tunnel of 200 m length was excavated near the district place Wardha of the state Maharashtra in India. The tunnel was proposed for passing the main canal of Lower Wardha Valley Project across the railway line and near the habitants. The broad gauge railway line crosses this tunnel at an angle of 19 degrees. The Left Bank Canal of Lower Wardha Project was crossing the broad gauge railway line and siding at one location. In this reach the canal was passing through deep cuttings of about 11 to 18 m in good compact basaltic rock mass. In this portion a 200 m length long underground tunnel was proposed. The excavation width of the tunnel was 8.5 m while the finished (inner) base width after lining of the tunnel was 7.3 m. The tunnel was D-shaped and the height from base up to springing level and to that crown was 3.75 and 6.15 m, respectively.

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