Compounded by issues associated with aging infrastructure, there is an increasing need for linear conveyances requiring connections to new and existing water sources. Tunnels are increasingly viewed as the most cost effective or least environmentally disruptive means to achieve the required connections.
Whether for raw/potable water transmission or the generation of power, the engineering of water conveyance tunnels requires an appreciation of a range of construction and operational considerations, including these:
- Subsurface tunneling conditions
- Groundwater hydrology
- In-situ ground stresses as related to conveyance leakage
- Hydraulics of confined and unconfined flow
- Transient pressures
- Lining requirements for long-term serviceability and maintainability
- Head losses related to tunnel surface roughness
Meeting the challenges of water conveyance
Mott MacDonald has engineered some of the longest and most challenging water conveyance tunnel projects in the world. We appreciate the significance of these complex issues. The breadth of our world-wide experience is brought to bear on every water conveyance tunnel project, no matter how small or large the assignment.
From the hardest rock to the softest clay conditions, beneath cities, rivers, oceans, or mountains, our extensive experience allows us to effectively identify the most appropriate tunneling technology. Depending on the ground conditions and internal and external hydraulic pressures, our tunneling team will evaluate the need for a tunnel lining, and if so, what type.
We have engineered linings consisting of cast in place concrete, precast concrete, troweled shotcrete, embedded or prestressed concrete cylinder pipe, steel pipe, or no lining at all.
Choosing the right tunnel boring machine
Often, tunnel boring machines (TBMs) are the most efficient means of excavation. Mott MacDonald has extensive experience in the evaluation of the right type of TBM for the project, whether contractor-selected or owner-specified.
Our water conveyance-related capabilities include these:
- Rock mass characterization
- TBM performance assessments
- Lining/round load transfer
- Groundwater modeling
- Hydraulic jacking testing
- Assessment of in-situ stress
- Water leakage assessments
- Lining roughness/headloss evaluations
- Dynamic modeling of transient pressures
- Cavitation evaluations
- Construction schedules and estimates