1 Underwater geotextile fabric laying construction technology

1.1 Laying program

The foundation should be leveled before laying on the beach, and the debris on the beach such as weeds and fishnets should be removed. Geotextile laying starts When the geotextile fabric starts to be laid, the operating vessel enters the lying position according to the positioning method and then throws The four anchors at the four corners of the ship should be fixed in a figure-of-eight shape. After that, the rolled geotextile roller is fixed on the geotextile laying ship. Then put the geotextile roller into the water slowly, and the starting end of the geotextile is fixed with a small anchor. The beginning of the geotextile is fixed with a small anchor, and the vessel is slowly moved by four hinged anchors on the working vessel. slowly move, drag the drum to lay the geotextile, and throw the ship-loaded gravel as it is laid. The rock will be thrown as it is laid. The same procedure is followed for the next geotextile.

1.2 Construction process and technical points

Construction process: geotextile fabric processing → geotextile fabric transport inspection testing → geotextile roll setting → paving ship loading → paving ship anchoring and positioning →Drum lowering, geotextile laying→Riprap suppression→this geotextile laying is completed.

Technical points:

(1) Measurement control network setting and measurement and sampling. Establish the base station, draw the geotextile release map and import the shipboard navigation chart to form the construction navigation chart. Determine the position of geotextile edge on the drum, adjust the ship so that the ship navigation chart shows two red coordinates for the geotextile edge coordinates, and check the accuracy of the ship coordinates with a mobile station, no error before the cloth can be rolled

(2) Coating surface cleaning. Use two ships towing long wire rope to the construction range of the coated surface to sweep the sea work, towing wire rope to ensure that the wire rope close to the coated surface, back and forth once, two ships are equipped with positioning systems to ensure that the clean-up range is not less than the design laying area.

(3)  Geotextile processing, transportation, testing, and cloth rolling. geotextile processing and storage firstly, geotextile is sewn and spliced on land, single-width 6m geotextile is spliced into width 23m geotextile and cut according to the designed processing length. After the geotextile is tested and qualified, the work of rolling the cloth is carried out.

(4) Stone loading and transportation. After the geotextile is rolled, the laying vessel leans on the loading dock to load stone materials, and after the vessel is loaded, it drives itself to the construction area and anchors at the laying position planned for implementation.

(5) Vessel positioning. Use the positioning device international more advanced GPS real-time differential positioning system.

(6) Geotextile laying. After the geotextile fabric is opened normally underwater, the underwater paving is carried out by controlling the stranded anchor machine according to the set location of the paving area, and four anchor machines must be moved simultaneously, two tensioned and two relaxed, such as not at the same time or go off must be adjusted in time. In the paving process each time move around the distance, backhoe excavator throwing gravel will pave the geotextile pressure so that it can not float up. When paving to the end, appropriately increase the amount of gravel throwing, relax the roller sling, move the paving boat out of the paving area, lift the paving roller, the whole paving process is completed, and then move the paving boat for the next piece of cloth paving.

(7) Gravel throwing and filling. Gravel throwing construction, the main work of loading → transport → positioning → throwing, construction content and requirements and laying the same, construction focus on the control of gravel bedding thickness. Geotextile lap, not repeatedly throwing gravel, in the adjacent block of geotextile is not laid, the distance reserved for the time being not throwing fill, to avoid the completion of gravel throwing, two pieces of geotextile lap quality is not good. Good. After the geotextile laying is completed, lift the roller and put away the positioning anchor. The laying of a single geotextile is completed.

(8) Laying quality and gravel bedding layer quality inspection. The quality inspection of geotextile laying mainly includes steel Pipe probe and underwater feel two kinds. On-water probing is carried out during the construction process. The probing tool is a steel pipe of 4cm in diameter and 3mm in thickness. The length of the steel pipe is more than 2.5~3m meters, and when the water depth is too deep, a 3cm diameter steel pipe is used to prevent the steel pipe from being used. A 3cm diameter steel pipe is used to prevent the steel pipe from over-sinking and causing people to fall into the water. In the process of geotextile laying, the method of probing is to take a trafficking boat At the edge of the geotextile with steel pipe down to the coating surface, through the steel The feeling of the tube touching the bottom to judge whether the geotextile is laid in place, The geotextile has elasticity at the bottom and can not be inserted downward, and there is no elasticity and can continue to be inserted. There is no elasticity and no geotextile if it can continue to be inserted. Gravel bedding layer Check the use of underwater divers feels.

Geotextile Bag

1.3 Underwater laying geotextile construction vessel and positioning method

The positioning system consists of 3 sets of high-precision GPS, computer, printer, and related software. machine and related software, among which one is onshore and two are on the boat. The positioning system is composed of 3 sets of high-precision GPS, computer, printer, and related software. The positioning accuracy is 5cm, and it can realize all-weather operation. Geotextile laying device consists of laying drum, sling, boom, lifting winch, etc. The geotextile laying device is composed of a laying drum, sling, boom, hoisting winch, etc. In geotextile fabric laying, the sling is the rope for lifting the drum. The sling is the rope for lifting the drum. must have sufficient tensile strength to ensure that it will not be damaged. The jib is the cantilever support frame for the drum. The hoist winch is mainly used to lift the drum It is used to adjust the depth of the roller when laying to prevent the roller from pressing the mud coating surface excessively so that the geotextile roller is obstructed by too The force is a too large and rolling difficulty, resulting in geotextile can not be continuously opened.

1.4 Throwing stone material to suppress geotextile with laying cloth at the same time

The method of stone-throwing is, every time the vessel moves, the distance is about 1 meter. The distance is about 1 meter, from one side of the roller to the other side of the stone-throwing, so as not to miss throwing or rethrowing. Do not miss throwing or rethrowing, throwing is completed before the next move The vessel can be moved next time only after it is finished. In terms of gravel suppression, every time 3-5 pieces of geotextile fabric are laid, the gravel bedding and the gravel bedding can be done immediately afterward. immediately followed by gravel bedding and stone-throwing suppression.


2 Dike body stone-throwing construction technology

2.1 Dike body stone-throwing construction technology process

Construction vessel loading → construction vessel transportation → construction vessel positioning → stone-throwing→check throwing section→acceptance→make up throwing position marking The construction vessel is loaded with materials.

2.2 Technical points of construction

The specific placing process is used in the construction of the dike body stone-throwing. Beacon machine with compass positioning, each construction vessel is equipped with a set of beacon positioning systems. The positioning system includes a beacon machine, a computer, and construction positioning software. The positioning system includes a beacon machine, a computer, and construction positioning software. First of all, the surveyor draws the construction layout according to the embankment design. Firstly, the surveyor draws out the construction drawing according to the embankment design and imports it into the construction software. The construction personnel at the site will adjust the direction according to the construction vessel position displayed on the computer desktop in real-time and the compass. The construction personnel at the site will adjust the direction of the ship according to the position of the ship displayed on the computer desktop in real-time and use the compass to direct the rock-throwing ship to The construction personnel on-site will direct the rock-throwing vessel to position and construct according to the position of the construction vessel displayed on the computer desktop in real-time and adjust the direction using the compass.

2.3 Embankment stone-throwing construction control

Dike body throwing stone respectively according to the loading plan step-by-step in layers, each layer throwing filling order transversely first throwing the middle and then throwing the direction of the two sides, that is, first throwing the heart of the dike, and then throwing the inner and outer seaside of the ballast layer.

2.4 Construction control by zone

The construction area was divided according to the construction schedule requirements and the construction working surface on the water, and considering the influence of tide level during construction and the combination of dike body throwing and surface stone construction. The construction vessel considers a shallow water working surface and a deep water working surface to ensure continuous construction even at low tide. The underwater layered casting construction should be well marked at the location of casting, fill in the casting records to avoid missing and overcasting, and record the loading time and loading thickness in detail to control the settling speed of the dam. After all the grid throwing is completed, at low tide, check the filling section of the water throwing part, for the part that still can’t be exposed after the tide, check by the depth gauge or depth rod, for the part that is not filled, mark it well and make up the throwing at the next high tide until it is qualified.

geotextile fabric

3 Embankment settlement observation

3.1 Settlement observation implementation plan

Test purpose: to measure the settlement of the foundation under all levels of loading, to understand the settlement law of the foundation, to judge the consolidation and stability of the foundation, and to control the construction loading rate; test project layout: the seawall surface settlement test is designed with 12 surface settlement observation sections. The surface settlement observation facilities were arranged in the dike axis, the inner seaside, and the outer seaside, and the distance between the monitoring sections along the dike axis was 300m; the monitoring instruments were buried and observed. Since all the measuring points are located in the sea, and only a few sections can be exposed at low tide, so the total station and level are used for measurement.

3.2 Settlement observation analysis

Through the analysis of in-situ observation and its results during construction, we conclude that: in the construction of a seawall, effective measures should be taken to ensure the quality of reinforced geotextile fabric laying, to level the dike surface before laying, to press the dike surface with small size stones in time after laying, and to avoid large stones from being thrown directly onto the reinforced geotextile as far as possible; the flow plasticity of the coastal phase silty soft soil is high, the strength is low, and the horizontal extrusion settlement often accounts for 25% to 35% of the total settlement during pre-pressure; the soft soil has high flow plasticity and low strength, and the horizontal extrusion settlement often accounts for 25% to 35% of the total settlement during pre-pressure. When building embankment on soft ground, the graded filling method can be used to make the soft ground strength gradually adapt to the increase of upper load to ensure the stability of the foundation; the axis of the seawall is generally long, in order to avoid the local low-lying section of a one-time loading is too large, it is necessary to make up for the leveling before loading. In addition, in order to reduce the settlement and uneven settlement after the work, it is necessary to complete the load filling as early as possible, and try to make the amount of load filling as small as possible.


[1] Xu Chengxiang, Yu Yongqiang. An overview of the development of beach polders in Zhejiang Province. Zhejiang Water Conservancy Science and Technology [J].

[2] Chen Xiu-Liang, Wu Wen-Hua. Discussion on the research ideas of polder technology in the polder project. Zhejiang Water Conservancy Science and Technology [J].

[3] Gong Baojun. Construction points of seawall construction. China High-Tech China high-tech enterprise [J].