Tarbela Hydropower Plant Slope Support Project
Project Background
The Tarbela Hydropower Plant is the largest hydropower station in Pakistan. This expansion project involves converting the existing No. 5 irrigation tunnel into a water diversion and power generation tunnel, adding three 470 MW mixed-flow turbine units, increasing installed capacity by 1,410 MW. The total installed capacity of the plant will rise from 4,888 MW to 6,298 MW, which is of great significance in alleviating Pakistan’s electricity shortage.
Challenges
The foundation slopes and surrounding rock of the tunnel are extremely fractured and highly weathered. The main geological structure consists of boulders, gravel, accumulated soil, and flowing sand. Conventional drilling methods frequently caused drill jamming, and borehole quality could not be guaranteed, resulting in poor support effectiveness and high risk of construction delays. Traditional reinforced bars could not form effective boreholes in collapse-prone formations, creating an urgent need for a support technology suitable for loose, easily collapsing ground.
Solution
To address these geological challenges, Sinorock provided R32 self-drilling hollow anchor bolts for support, replacing conventional reinforced bars.
- Rock Bolt Specifications: R32 self-drilling hollow anchor bars, design depths of 6 m and 8 m, connected by couplers. The front end of the rod is equipped with an R32/76 steel cross-cut drill bit, and a 72 mm-diameter centralizer is used to ensure a grout layer thickness of no less than 20 mm.
- Technology: The self-drilling hollow anchor bar integrates the drill rod, grout pipe, and reinforcement material. It is not affected by collapse-prone ground and uses a simultaneous drilling and grouting process. Borehole formation, grouting, and anchoring are completed in a single operation, effectively solving drill jamming and borehole collapse issues.
- Construction Process: Preparation → Borehole positioning → Drilling → Grouting → Mesh installation → Bearing plate and nut installation → Inspection and acceptance
Results
- Increased Construction Efficiency: The self-drilling hollow anchor bolt method is simple and fast. Boreholes are formed and grouted in one operation. After drilling to the design depth, grouting is performed directly, greatly reducing work time.
- Reduced Project Cost: Avoiding repeated drilling and material waste due to borehole collapse effectively lowers overall project costs.
- Effective Temporary Support: After grouting, the grout consolidates with the surrounding loose rock to form a solid anchor body, providing excellent anchoring and greatly improving slope and tunnel safety.
Client Feedback
Project stakeholders unanimously recognized that self-drilling hollow anchor bars are the most efficient, reliable, and economical method for supporting loose and collapse-prone ground. Compared to traditional methods, this approach not only resolves drill jamming and collapse issues but also significantly shortens the construction schedule and reduces costs, providing strong assurance for the safe advancement of the hydropower plant expansion project.
