Plate armor foundation (PAF) - Innovative for intertidal wind turbines

Abstract

The plate armor foundation (PAF) is an innovative type of foundation for intertidal wind turbines. A PAF consists of a top plate that is made of reinforced concrete and a side wall which is made of Larsen sheet piles. The steel tie rods are used to connect the top plate and the side wall. The Larsen sheet piles are interconnected using the edge locks. This connection mode is generally considered to be hinged connect. The PAF has significant advantages of cost effectiveness and fast installation. Model tests were conducted to investigate the monotonic lateral bearing capacity and its influence factors of the PAF in saturated marine fine sand. 3D numerical modeling was performed to explore the cyclic behavior of the PAF. Results show that the PAF with sheet pile hinged connection can provide higher lateral bearing capacity and effectively limit lateral deflection compared with no connection and welded connection between sheet piles. It was found that when the L'/L (L' is the length of the sheet pile edge lock and L is the height of the side wall) equals 1/3, there is no significant change in the lateral ultimate bearing capacity compared with the L'/L value of 1, while the lateral ultimate bearing capacity decreases by 14.3% when L'/L equals 2/3. Additionally, under a certain length of the sheet pile edge lock (L'/L value of 1/3), the sheet pile edge lock position (at the upper, middle, and lower part of the side wall) has a slight effect on the lateral ultimate bearing capacity. In addition, the lateral bearing capacity increases with increasing the aspect ratio of PAF; however, decreases with the increase of the loading eccentricity. During lateral loading, rotating behavior between neighboring sheet piles occurs. The incremental rate in the rotation angle decreases considerably with increasing the lateral load. Furthermore, the failure mode of the PAF changes from a combination of horizontal translation and rotation to pure rotation during loading. Numerical simulation results show that the PAF's accumulated deflection and accumulated rotation increase with increasing the loading cycle and loading amplitude. The excess pore pressure increases rapidly in the early stage of the cyclic loading.