Low Poisson's Ratio Pile for Underwater Noise Reduction
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Solution Overview
Problem
Pile driving in water generates extremely high sound levels that harm wildlife and delay construction projects, as existing noise mitigation methods like bubble curtains and Temporary Noise Attenuation Piles (TNAP) are not effective in significantly reducing underwater noise due to their inability to address sound transmission through the sediment.
Innovation Solution
A noise-attenuating pile design featuring a driving shoe and an elongate tube with low effective Poisson's ratio and geometric features such as longitudinal slots or grooves, along with a concentric outer tube that isolates the inner tube from water and sediment, and an optional bubble generator to further decouple the pile from the ground, reducing radial expansion and compression wave transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional pile driving is used, then construction productivity is maintained, but underwater noise levels become extremely high causing harm to wildlife and project delays
Solution Approach 1:
The pile is segmented into multiple sections with different structural characteristics. The upper portion uses a solid circular cross-section while the lower portion uses a hollow circular cross-section, allowing each segment to serve different functions in noise reduction and structural integrity during driving
Solution Approach 2:
The pile structure transitions from a solid circular cross-section to a hollow circular cross-section along its length. This parameter change in geometry allows the pile to maintain structural integrity while reducing noise transmission to the surrounding environment
2Object-affected harmful factors
If noise mitigation measures like bubble curtains are implemented, then some noise reduction is achieved, but sound transmission through sediment remains high
Solution Approach 1:
The harmful noise-generating mechanism is extracted from the system by using a hollow pile structure that prevents compression waves from reaching the sediment, eliminating the need for additional noise mitigation devices like bubble curtains
Solution Approach 2:
The hollow pile structure acts as an intermediary between the pile driver and the sediment, blocking the transmission path of compression waves and preventing noise from reaching the surrounding environment
3Object-affected harmful factors
If hollow-walled TNAP pipes are used, then some sound level reduction is achieved, but not all noise reduction criteria are met
Solution Approach 1:
Different portions of the pile have different cross-sectional properties - the upper portion is solid while the lower portion is hollow. This local quality variation optimizes both structural performance during driving and noise reduction in the surrounding environment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed pile design effectively reduces underwater noise by minimizing the transmission of radial expansion and compression waves, achieving significant noise reduction and mitigating the impact on marine life, thereby allowing for more flexible and timely construction.
Implementation Method 1
an elongate tube that is configured to have an low effective Poisson's ratio such that the amplitude of longitudinal radial expansion waves resulting from hammering or driving the pile into the ground are substantially prevented from being transmitted into the ground
Implementation Method 2
a concentric outer tube that isolates the inner tube from water and sediment
Implementation Method 3
an optional bubble generator to further decouple the pile from the ground
Data Source
AI summary
A pile with a low effective Poisson's ratio is disclosed, which greatly reduces the sound coupling to the water and sediment or other ground when driving piles. In some embodiments the pile includes geometric features that reduce the radial amplitude of the compression wave generated during hammering by providing a space for circumferential expansion along the length of the pile. The geometric features may comprise slots and/or grooves. In an embodiment, a driving shoe has a perimeter that extends beyond the pile tube such that the sediment produces less of a binding force on the pile. The pile may be formed as a double-shelled pile with either or both shells having effective low Poisson's ratio properties. A bubble generating plenum may be attached to the shoe to further reduce friction during installation.