Ⅰ Breakwater Construction for Small Boat Port

1.Breakwater Selection

1.1   Natural Port: It’s a gift of nature. The wide river can be built with yacht dock, especially the one that can straight in to the estuary of the sea. It is really valuable nature resource without expensive construction of breakwater.

1.2 Inland Lake:Some of vast lake are the best waters for yacht marina construction, such as the five largest freshwater lake in China or the great lakes in north American. However, due to the large scale of water and long fetch length, it will lead the waves’ height more than 2 meters. So, it needs breakwater facilities to protect the harbor running. And also, the breakwater shall be heavy or light floating breakwater as the best choice to block surface waves.

1.3 Marina/Dock/Jetty with Heavy-duty Wave Attenuator: In most cases, if a floating pontoon system was built in an open sea without sheltering area, there needs to cost a huge sum of money to build a wave attenuator to stop high waves. The scale of the wave attenuator should be determined by scientific analysis of mathematical model and physical model referring to the data of nearshore wind, waves and currents. And wave attenuator types such as enrockment breakwater, permeable breakwater combined with high-pile dock and wave baffle, caisson breakwater, precast concrete block breakwater, etc

1.3.3 Permeable Breakwater

1.3.4 Caisson Breakwater

Ⅱ  Floating Pontoon Structures

1 Aluminum Alloy Pontoon VS Steel Pontoon

1.1 Aluminum Alloy Pontoon: In the marine environment, aluminum is usually given priority due to its high corrosion resistance, high aesthetics, easy assembly and other advantages. Aluminum pontoon systems are more suitable for the manufacture of components of different lengths, widths and shapes. and assembly. The aluminum dock system adopts the marine grade of aluminum 6000 series, such as (6061-T6/6065-T6). It is the preferred choice for small boat port with excellent shelter condition to use, the cost is suitable, and the maintenance is convenient.

1.2 Steel Pontoon: The ships, which moored in waters with poor wave condition, is more suitable for applying steel pontoons. In this harsh environment, The steel with better tensile and compression is more suitable for bearing large loads.

1.3 The supporting systems of water surface on aluminum alloy pontoon and steel pontoon are composed of LLHDPE dock floats, which are filled with expanded polystyrene and never sink.

1.4 The service life of aluminum pontoon and steel pontoon can reach more than 25 years.

In a small boat harbor with good shelter conditions or small wave at estuary, the use of aluminum or steel pontoons is very cost-effective. Because of high cost, so concrete pontoons have no advantage in this location.

2 Concrete Pontoon Application

2.1 Concrete Pontoon System

A floating concrete pontoon system is large floating structure composed of a pile holder structure and floating pontoon. Concrete floating structures are usually composed of EPS foam blocks with different thicknesses, steel bars and high-performance concrete. The dock floats are minimum pentagon shape and the bottom side is not protected. The manufacturing specifications of individual concrete units suitable for harsh marine environment are depended on manufacturer, including width of 2.5 meters, 3 meters, or 3.6 meters and even larger units of 12 to 20 meters. And the width can satisfy different design requirements of marina/dock/jetty. Concrete units are jointed to form a water platform for pedestrians or vehicles. The concrete pontoon system usually adopts semi-rigid connection, and flexible connection components are used in accordance with the connection requirements. Larger units from 12 to 20 meters are connected by bolts with high-strength connecting rods and rubber blocks.

2.2 Concrete Pontoon Application Conditions

If a marina/dock/jetty is located in the area with frequent typhoons or hurricanes, and the outside of the marina/dock/jetty faces an open sea, forming a long-wind area, the permeable breakwater shall be the choice, it is very important to choose the type of pontoon under this condition. Because of the possibility of undercurrent within the marina/dock/jetty, the impact of superimposed waves formed in the long-wind area and the windy weather with the main wind above level 12, it is especially important to be cautious in the selection of pontoon in the project site. There are many kinds of waves in that area, such as the undercurrent caused by permeable breakwater, which makes the water surface fluctuate more than 0.5m, the long-wave periodic waves formed by the waves coming in from the entrance, and the reflected waves formed by the waves rushing to the dark wall. The combination of various waves and the poor wave stability conditions in the marina/dock/jetty have a great impact on the ships/yachts/boats moored in the port, and at the same time, it is a severe test for the floating dock system. Therefore, the heavy-duty concrete pontoon bridge is especially preferred in this small boat port, and the flexible connection points should be extremely firm, and special elastic stop bolts should be preferred for component bolts.

Ⅲ Pile Height Design

Due to the increasing frequency of extreme bad weather in recent years, higher requirements are put forward for marina/dock/jetty facilities, such as the height of positioning piles out of the water surface which needs attention.

On August 23, 2017, Typhoon Hato hit Zhuhai, Guangdong Province, which coincided with the astronomical tide, causing serious short-term water increase in the waters within 40km of the typhoon center, leading to the pontoons falling off the piles.

On September 7th, 2018, Typhoon Mangkhut caused the floating pontoons fall off the piles. According to the existing specifications, the pile height was calculated as extremely high water level +2.0 meters. Nowadays, in the southern waters, this standard falls behind, and the extreme weather is constantly appearing, which happens once in 70 years. Therefore, the standard should be increased by at least 1 meter to ensure safety.