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The latest underwater installation method for rubber fenders - no loose concrete mortar device
Edit: Jiangsu Ahn Jin Rubber Co., Ltd.Date: 2018-10-16

A military military wharf is a pier-slab beam-slab structure, which is now being reconstructed. The original sinkhole pier base is adhered to, the existing pier I-beam plate is removed, and the cast-in-place C45 reinforced concrete girder plate structure is simply supported on the sinking pier. The original 152 sets of old rubber fenders on the 6 sinking piers were completely removed, and 78 sets of DA300 rubber fenders were reinstalled. There were 52 sets of DA300 fenders in the submarine area, with a total of 312 fender screws and a screw length of 30 cm. The angle plate is 6 cm in diameter. When the water is low, the underwater fender is nearly 3m deep. The removal of the old rubber fender and the new fender screw hole can be cut with water and drilled underwater.

However, the anchoring of the new rubber fender screw, the traditionally selected sulphur mortar or epoxy mortar is difficult to ensure the anchoring quality under water construction. Therefore, in order to ensure the quality of the project, priority is given to creating dry construction conditions and using dry construction methods. The construction principle is the same as that of the cofferdam. The attached structure is processed with a steel structure. The shape is like a center of a case without a top cover. The open side of the box is facing upward, and the other open surface is attached to the pier. The fender is used to separate the fender from the seawater outside the tank, and the seawater in the tank is removed by a water pump to form dry construction conditions. The water stoppage between the box body and the pier body is firstly separated and prevented from leaking by the water-stopping film between the box body and the pier body. The reinforcement of the box is selected by drilling and embedding the expansion bolts on the pier body to connect with the box body. After the processing of the box, the experiment was carried out, and it was found that the water-stopping film could not stop the water. After the diver went to the sea to check, the flatness of the original pier was poor, and the largest place was 5 cm, which was very difficult to stop. The construction period is 90d, 1 box, and a set of fender screws can be buried in about 5d, which is far from satisfactory. If you need to rework the cabinet, you need to add the cost. In view of the above reasons, we began to negate the dry construction method and turned to other construction techniques.

Refer to the method of incorporating the non-dehydration and flocculating agent in the submerged engineering such as the bottom cover of the sinking well, the cofferdam, the underwater connecting wall, etc., and adopt the underwater injection into the screw hole to inject the underwater non-staining cement mixed with the non-dispersive flocculant. The process of submerged the rubber fender of the submerged device after the mortar is embedded in the mortar.

Process: Prepare the work→Remove the old fenders→Finish the dock and the fender touch belt→Locate→Underwater drill fender screw hole→Clear hole→Do not fill the hole in the cement mortar to embed the underwater fender screw→Install the underwater rubber Fender .

Underwater non-scattering cement mortar raw materials and their cooperation ratio

(1) Cement: Island brand 42.5R Pu-Si cement:

(2) Sand: sand in the Tengqiao sand field:

(3) Expansion agent: Aoshan brand AEA expansion agent:

(4) UWB series 砼 flocculant: 渤星牌.

It is concluded by experiment that the cooperation ratio of underwater cement mortar is 1:1.2:0.38 (cement:sand:water), and the consistency is 30mm. In order to ensure the tight combination of mortar and hole wall, AEA expansion agent is involved in the mortar, which accounts for the cement dosage. 8%. Together, in order to improve the workability of the mortar and improve the strength of the mortar, the UWB series of bismuth flocculant produced by the Engineering Research Institute of China National Petroleum Industry Corporation is added to the mortar to make the mortar not disperse in water and the cement is not lost. It can be white and dense under water. In addition, in order to enhance the fluidity of the mortar, a 0.2% HN type superplasticizer with a cement content is added, and the mixture is evenly mixed and then applied.

Primary construction method

4.1 Removal of old rubber fenders

Undercut the equipment underwater, cut off the bolts and nuts on the old fender, and then carry it away by hand hoist. The top of the fender is removed from top to bottom, and the device is constructed from bottom to top.

4.2 Finishing the dock surface and the fender touch belt

The diver stands on a simple well-shaped work frame, and the underwater smashing off the yak legs that are removed from the fender to protrude from the dock surface. The sea otters within the rubber fenders and dock touch belts are eradicated by a blade and leveled within this range.

4.3 positioning and underwater drilling screw hole

The measuring personnel staked the screw positioning plate (Fig. 1) and installed the positioning plate. A T-shaped work frame was machined with medium 20 steel bars, which was fixed firmly on the side of the dock. One diver operated a pneumatic rock drill on the work frame, and one diver supported the drill pipe (drill diameter 7.5 cm) to align the drill hole. After reaching the planned depth, pull out the drill pipe and clear the hole (Figure 2).

4.4 Inside the hole, do not loosen the cement mortar, embed the underwater rubber fender screw

When underwater grouting, the clean water in the screw hole is a condition for full filling. In order to make the device screw full of grouting, we made a grouting cylinder (Fig. 3) with a diameter of 6 cm, which is 2 cm smaller than the screw hole. When grouting, the rubber fender screw is first placed in the hole to fix the position. When grouting, the grouting cylinder extends into the hole and grouts while draining. Slowly exit the grouting drum together and reach the requirement of full grouting. In order to prevent the screw from being misaligned, the positioning plate is used to cover the screw before the mortar is condensed, and the positioning plate is reliably fixed. After 3 days, the positioning plate is removed to ensure that the screw is not biased.

4.5 underwater fender

After the cement mortar is consolidated and the strength is satisfied, the artificial reed is used to support the fender. When using the device, use the hoist to hang the fender and slowly position it. Under the two sides of the water, stand on both sides. With the cooperation of other personnel, hold the rubber fenders in a big position and insert the bolts. If the hole position error is not correct, use small The jack is attached to the fender and the screw nut is tightened to complete a fender.

5 anti-extraction experiment

In order to check the degree of underwater condensation and grouting of non-disintegrating mortar, two experimental tunnels were drilled in the water level change area of the dock. Two rubber fender screws are embedded in the underwater grouting. After 7d, the jack is used to draw the screw. The screw receiving pull force is above 20kN, and the planning unit acknowledges that it can satisfy the use requirements.

6 construction quality control

(1) It is necessary to set a good position when drilling, and it is not allowed to be biased;

(2) When clearing the hole, the pre-buried hole should be cleaned;

(3) The underwater non-discrete mortar should be strictly according to the cooperation ratio and the metering is correct. The diameter of the grouting device should be slightly smaller than the screw hole diameter, so that the air in the screw hole can be discharged during grouting to ensure the filling of the hole is full:

(4) Before the screw is buried, the anti-corrosion operation of the screw should be done.

Conclusion: (1) Due to the limitations of the external conditions of the terminal, it is not possible to use the dry construction method to install the underwater fender. It is feasible to use the underwater non-staining mortar to embed the fender screw to install the underwater fender. The quality of the fender device; (2) If the steel bar is encountered during the drilling process, it may be cut with a water cutting device or replaced with an alloy drill bit; (3) The grouting device used in this project is relatively primitive and needs further improvement. If the hole diameter is properly increased, the rubber fender screw should be better buried.