China Xinxing Construction & Development Corporation Changchun Company encountered some problems such as the difficulty in processing ultra-thick formwork bags and the lack of technical standards for soft sinking of water gabions during the construction of revetment with formwork bags and underwater gabions in Ersong flood control project. After the on-site technical research by the technical department of the company, a set of molding experience was summarized, which was recognized by the quality inspection department and the design unit, which not only met the design requirements, but also ensured the timely delivery of the project and was well received by the construction department. They are introduced as follows:
A, slope protection mould bag
Mould bag slope protection project is an effective engineering measure to prevent bank slope from being damaged by flood and ensure the benefit of flood control project. There is a shortage of sand and gravel resources in the middle and lower reaches of Songhua River in Jilin Province. The best choice of bank slope protection material should be formwork bag concrete, which is made of specially thickened plastic woven cloth and laid on the trimmed slope in turn, and injected with 200# cement mortar. A Ф10-Ф 20 steel bar runs through each bag. After the cement mortar is consolidated, it forms an integral slope protection concrete block, which can prevent the flood from washing the bank slope and ensure the bank slope.
1. 1 Quality requirements and manufacturing requirements of mould bag materials
According to the design requirements, the material of general slope protection formwork bag must be plastic woven cloth, with a general bulk density of 90- 1 10g/㎡, ultimate tensile strength of 750- 1000N/5cm and permeability coefficient of k =1×10-2.
However, due to the design requirements of the second pine project, the plastic woven fabric must be 150g/m2, 0.6mm thick, with a permeability coefficient k = 7×10-3-8×10-3 cm/s, a friction coefficient greater than 0.4 and a breaking strength greater than1. The blasting strength is greater than 600N, the spacing between drainage points is 4 1.5cm, and the row spacing is 44cm. The drainage point needs to be carefully sutured and cannot leak. The actual width of the upper single-layer fabric between two adjacent drainage points of the mold bag is 42.5cm, and the width of the bottom single-layer fabric is 4 1.5cm, that is, the upper and lower layers are tight. Due to the difficulty in processing the mold bag, the processing factory could not be found (inquired through the network). Therefore, the technical department of our company has been approved by Jilin Water Conservancy Engineering Quality Inspection Center and Design Institute through research and test, and has carried out batch processing and production to ensure the normal construction on site.
1.2 mould bag-making technology
1.2. 1 Sketchpad (the standard mold for drawing drainage points) has been made.
The sketchpad is made of plywood, with a length of 1.7 m and a width of 44 cm. According to the design requirements, cross drainage points are chiseled on the drawing board. The drainage point size is 3cm× 14cm× 14cm, with half drainage points at both ends and three drainage points in the middle. The distance between adjacent crossing drainage points is 42.5 cm. This distance refers to the center of two adjacent drainage points.
Unit (cm)
Sketchpad 1.2.2 Draw lines
The sketchpad is placed perpendicular to the long direction of the weaving, with one end of the sketchpad and the long side of the weaving as the first end. Draw the sideline of the drainage point and the sideline of the long side of the drawing board on the fabric with a pencil.
1.2.3 Sewing drainage point
According to the drainage points drawn, sew with a needle that has been ground with nylon skin, starting from the first end of one row and sewing the next row. Sew rope ends as locks at the semi-drainage points at both ends of each row, leaving rope ends. The rope head 15cm to 20cm long (when the rope head is laid, the adjacent mould bags are connected together), and the rope head is sewed up at the three drainage points in the middle as a buckle. The bearing capacity of nylon leather (rope) sewed with drainage points is not less than 17.5kg, and the length of a finished mold bag is 100m, with 5 rows of drainage points and 227 rows. * * Drainage point 1 136, the distance between the row and the upper floor (exposed after grouting). When sewing the drainage point, the upper shuttle cloth overlaps 1cm, and the distance before sewing the drainage point is 4 1.5cm. After sewing a drainage point, sew the next drainage point in the same row. Similarly, before sewing, the upper shuttle cloth overlaps 1cm with a distance of 4 1.5cm. In this way, after sewing one row, start sewing from the first end of the next row.
1.2.4 Edge sealing and extension
Draw a straight line along the semi-drainage point at the end of each row with a sewing machine. The length of each finished mould bag is 100 m, which is less than100 m. Pay attention to the distance between drainage points on both sides of the joint, which is 44cm. The rows should be well aligned and must be in the same straight line, and no burrs are allowed at the joints.
1.2.5 quality inspection
There is a full-time quality inspector to test, and the spacing between adjacent drainage points and the spacing between two rows of drainage points at the expansion joint of the mould bag must meet the size standard, and the drainage points are not allowed to leak, so as to ensure that the products meet the quality standards.
1.2.6 packaging
Each finished mould bag is bound into a bundle with the length of 100m, which is sealed in a packed woven cloth barrel with the words "1.66x100m" written on it.
The above is the whole process of making mould bags in our company. The mould bags produced by our company have been tested by Jilin Water Conservancy and Hydropower Engineering Quality Testing Center. The test results show that all the measured values of the mould bag meet the design standards and the requirements of the specification (GB/T 8946- 1998).
1.3 formwork bag concrete construction procedure
Leveling the slope according to the design requirements, eliminating weeds and hard objects, excavating the foundation trench with the depth of 1.0m, laying the non-woven fabric filter layer, making U-shaped nails with 8# iron wire, fixing the filter layer on the slope protection base according to the design requirements, and quickly laying it on the vertical slope according to the construction workload. Shopping bags should be fixed on the surface of the filter layer of non-woven fabric. At the same time, according to the design requirements, insert Ф Ф12mm steel bars into the bag one by one. When laying the bag, pay attention to the top and bottom of the bag. It is forbidden to put it backwards.
After the above procedures are completed, the mixer can be started after inspection, and water, cement and sand are added according to the designed mixture ratio for mixing. At the same time, assign special personnel to inject water into the mould bag to lubricate the wall of the mould bag, so as to facilitate the concrete flow. The cement mortar number is 200#. After the concrete is evenly mixed, it is injected into the mold bag one by one by mortar pump to make the mold bag full of molding. After the mold bag is formed, the surface will be watered and maintained, usually twice a day. If the water is dry at high temperature, no one is allowed to walk on the surface of the mould bag before the concrete is solidified.
1.4 summary of formwork bag concrete construction
The formwork bag concrete is poured from top to bottom, and the gradient ratio m=2.5-3.5 is appropriate. Gravity pouring process should not be too long. If the length of the slope exceeds 15m, the concrete is easy to separate during the flow. In order to prevent this phenomenon and ensure the construction quality, it is still necessary to equip the mouth of the feeding box with a corresponding length of rubber conveying pipe for bag dumping. In addition, in the process of pouring, if it is found that the concrete pouring is not smooth, the construction personnel will gently touch the wall of the mold bag with a self-made guide rod to make it smooth. Do not use tools or send someone to squeeze the surface of the mold bag.
Second, the soft water surface of gabion sinks and drains
Gabion revetment can effectively prevent the bank from breaking and retreating after being washed and soaked by river flood, and prevent the river from changing and diverting. It is an effective engineering measure to weave the mesh with iron wire (Line 8), place it on the shore according to the design requirements, and seal it with stones to form a gabion. The gabions are connected in rows, covering the bank slopes washed by floods (onshore and underwater) and playing the role of stabilizing the feet of flood control and revetment.
2. 1 barbed wire preparation
There are two ways to manually weave barbed wire on site: one is to weave it on the flat ground, and the other is to weave it on the erected shelf. The latter method can save wires because there are no extra threads. The width of the barbed wire is determined according to the cross-sectional size of the gabion, the length is given by the design according to the bank slope of the revetment, and the mesh size is determined according to the design size. Each piece of barbed wire has a full-time staff to check the mesh size, which must meet the design standard wire width1.6m. During the construction, the mesh size of our company's self-made barbed wire is 15cm× 15cm, the cross-sectional size of the gabion is 40×40cm, and the 8# wire is 2.100 per square meter of barbed wire.
2.2 Underwater gabion soft sinking
Self-made floating boat is used for soft sinking of underwater gabion, which is operated manually. Operators must wear life jackets. After the gabion was sealed, it was manually thrown into the river with a skateboard. The specific operation method is as follows.
2.2. 1 Homemade gondola
The self-made flat buoy is made of sealed empty oil drums, which has excellent balance and stability conditions. Every 4(6) oil drums are connected into a group, and the joints are wrapped with 8# barbed wire and fastened into four groups. Tie a beam to each group, and put two groups of oil drums at both ends of the beam. The beams are paved with planks, and the thickness of planks meets the load-bearing requirements. The length of the beam is determined according to the need, and the boards should be leveled, thus making a self-made flat pontoon bridge.
2.2.2 The soft body on the gabion sinks.
2.2.2. 1 laying composite geotextile at the design position. Determine the length of composite geotextile according to the length of underwater gabion, connect the composite geotextile in the water with the composite geotextile on the shore, cut several holes of 5×5cm on the surface of composite geotextile to facilitate the exhaust and drainage, and tie buoys at the two corners of the end of underwater gabion in Upright as the end marks of underwater gabion. Tie 3 ~ 4 stones to the end edge of underwater composite geotextile, flatten it with a floating boat, and then tie the composite geotextile to the water surface.
Use φ 12m steel bar as 2.2.2.2 mark, and insert two steel bars at the edge of the gabion to be sunk.
2.2.2.3 installed a gabion on the flat pontoon. Before installing the gabion, put a skateboard every 2 meters to throw the gabion. The gabion will be transported to the ship by the stone platform car through the springboard, and the gabion will be filled and sealed. Draw Upright to the mark. Many people will tilt the skateboard and throw it at the mark at the same time. When they reach the shore, the head end will be firmly connected with the land gabion.
2.2.2.4 pulled out the marked reinforcement after throwing a gabion and inserted it into the edge of the next gabion adjacent to the thrown gabion.
The above operation steps are the whole process for our company to complete the soft sinking of gabion in 0-8m water depth in Ersong flood control project. This method is suitable for small-section gabion sinking on water.
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