Bottom boundary layer in situ observation system suitable for shallow water viscous seabed and its deployment method

Abstract

The invention provides a bottom boundary layer in-situ observation system suitable for shallow water sticky seabed and a layout method thereof. The invention establishes a simple and self-made low-cost and easy-to-operate hydraulic pile foundation system, which can not only ensure the piling depth, realize the anti-subsidence and stability functions of the seabed observation system, but also specify the number and position according to the needs when the observation system is laid out piling; adopt the means of free assembly of stainless steel pipes, build the instrument layout area and the undisturbed observation area, realize the integration of various instruments, and avoid the disturbance effect of the instrument frame on the observation space. The instrument layout area can be adjusted and adjusted according to user needs Matching; the foot plate is used to fix the system between the feet of the observation frame and the top of the bottom pile, which is not limited by the weight of the observation system itself, and improves the shortcomings of the settlement plate. The components of the invention are easy to replace or maintain, low in cost, can be widely used, and effectively solve the problems of in-situ observation of the bottom boundary layer in terms of full horizon, multiple parameters, continuous stability, high cost, and the like.

Description

technical field [0001] The invention provides a seabed observation system, which belongs to the technical field of ocean surveying. Background technique [0002] The bottom boundary layer refers to the water layer near the seafloor where the current structure is obviously affected by the seafloor boundary. It is formed by multiple interactions between the bottom non-uniform water flow and the bed bottom, and is characterized by large density and turbidity gradients, turbulent instability, and difficult determination of boundary thickness. In the boundary layer, the energy of the water flow is dissipated due to bottom friction and turbulent movement, and it is manifested in the form of bottom shear stress, causing erosion or resuspension of bed sediments, resulting in vertical stratification of suspended sediment concentration, which in turn This in turn affects the flow structure. The hydrodynamics of the bottom boundary layer and the movement of fine-grained sediments hav...

AI Technical Summary

Problems solved by technology

When the leg-bearing system sits on the seabed, due to the large void ratio of the cohesive seabed sediment, the weight of the observation frame (about 600-1000 kg) and the repeated erosion of the legs by the water flow often lead to its overall settlement, which will affect the observation. The effect, if it is heavy, it will cause the observation frame to be partially buried and cannot be recovered

If the settling plate method is adopted, the size of the settling plate should be determined according to the self-weight of the observation system. If the settling plate’s inward expansion area is too large, it will squeeze the observation space and interfere with the observation of the bottom boundary layer; if it is too small, it will affect the anti-settlement effect (CN201621100512. 6 Observation frame near the bottom boundary layer)

[0004] For the pile bearing system, the observation frame can be placed on the bottom pile to avoid settlement. However, due to the high cost of the drilling rig and relatively clumsy operation, usually only one or two piles are driven for bearing, and the pile itself or the observation system are likely to cause disturbance. flow, the space available for instruments to be fixed is limited, which limits the number and integration methods of instruments

Drilling with high-pressure water guns is relatively cheap and flexible, but the existing technology only considers the scouring effect of high-pressure water flow: that is, by adding additional pressure and reducing the diameter of the water gun, the seabed is washed out of the pit to place the pile tube, Not only can the piling depth be limited (about 3m) because of the inability to break through the consolidation layer, but also the large scour pit will interfere with the observation space, and additional equipment such as GPS, depth sounder, and booster pump are required to ensure the depth and stability of the pile foundation. There are many deficiencies in performance, piling cost, flexibility and operability (CN201720662009.8 A simple deep-sea piling device)

[0005] Observation accuracy of bottom boundary layer, parameter diversification, seabed settlement, pile foundation stability, operation convenience and other technical and economic cost issues have long been obstacles to the observation of shallow water viscous seabed bottom boundary layer. Existing technical solutions cannot meet the economic, Requirements for convenient, stable, modular, multi-parameter in-situ observation of shallow-water viscous seabed bottom boundary layer

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