I. Synopsis

Rubber dam is a kind of low head water retaining buildings, a new type of hydraulic building that appeared in the late 1950s with the development of polymer industry. It uses synthetic high strength fiber canvas as the stress skeleton, the surface water stop layer and the protective layer are made of adhesive tape with neoprene rubber (or other synthetic rubber) or made of whole vulcanized tape. It is anchored to the dam floor according to the design size to form a new type of closed water retaining building. China's rubber dam business formed its own characteristics after more than 30 years of practice, in engineering planning, design, dam bag manufacturing, installation and operation and management, has reached the world's advanced level.

With the increasing pace of construction of rubber dam projects, the promotion of economic and social benefits is increasingly significant, is widely used in flood control, water retention irrigation, urban and rural water supply, hydroelectric power generation, landscaping and many other areas, the reservoir water resources are also occurring in the overflow, seepage, evaporation and other dynamic changes.

 

II. Necessity for suture bonding techniques

The top of the rubber dam can overflow, adjust the dam height according to the need, effectively control the upstream water level and discharge flow, so that the surface water resources can be optimally configured and utilized. In the daily operation and management, Rubber dam project occurred dam bag tear, damage phenomenon every year due to natural or man-made factors such as ultra-high operation, overpressure operation, overflow depth is too large, overflow depth varies, dam bag vibration, the dam bag structure does not meet the requirements of the project operation, the external impact, rubber dam bag local wear and tear, charging and discharging systems failures, freezing damage, man-made damage, rubber dam bottom plate washed down. Due to the rubber dam bag self-importance, once damaged, especially the occurrence of longitudinal large incision and large area of the tear, not only a single maintenance program, long construction period, high cost, and seriously affect the normal play of engineering benefits.

 

According to the design principle of the rubber dam bag, according to the "rubber dam technical specifications" (SL227-98) stipulates the technical requirements for the repair of the dam bag adhesive patching technology, through the longitudinal large incision of the dam bag sewing adhesive patching technology practice and research, the same applies to other cracks. The technology for rubber dam bag longitudinal cracks, in the repair, according to the rubber dam bag force is mainly radial dam bag cloth force, latitudinal dam bag cloth force is very small and other characteristics, the use of the original dam bag radial fiber degree of consistency of the nylon thread, the innovative use of longitudinal fracture stitching, gluing and patching of the new technology. It is an extension on the basis of the original dam bag repair and mending technology, improve productivity, improve production efficiency, so that the dam bag repair and mending technology has made a breakthrough, and its innovation lies in the sewing.

 

III. Sewing and gluing technology construction process

3.1 Sewing and gluing process and principles

The flow chart of the rubber dam bag longitudinal large incision suture adhesive patching process is shown in Fig.1

Taking the 2 cloth 3 rubber dam bag split as an example, the principle diagram of double-sided sewing and gluing mending is shown in Fig.2

3.2 construction process

3.2.1 Preparation work, first remove one side of the rubber dam bag anchorage line, including concrete, bolts, pressure plate, rubber gaskets, dam bag cloth, and after the removal of the dam bag turned over, spreading; the dam bag breakage cleaned, dried, flattened, delineated the scope of repair; according to the same size of the reinforcement used in the dam bag cloth cut to 2 cloth, 3 rubber, for example, lap width of 15 cm.

 

3.2.2 Hairpinning with a grinding wheel or wood file on the longitudinal crack inside and outside the two sides and two pieces of adhesive sheet were hairpinning. When beating the hair, in order, the requirements of uniform, can not hurt the polyamide canvas. Wooden board can be padded in the need to repair parts of the dam bag below, with a wood file or sanding wheel to the dam bag damage and reinforcement of the dam bag cloth respectively, hair, hair surface uniformity, and the bonding surface of the adhesive powder and other debris cleaned, scrubbed with detergent to ensure that the lap surface for the fresh surface, increase the bonding surface surface than the surface area, and enhance the adhesive strength of the lap surface bonding.

 

3.2.3 Sewn nylon series more varieties, but for rubber dam canvas but only nylon 6 and nylon 66 nylon. Nylon 6 by the ring-opening polymerization of ethylene propylene amide, so often called polyethylene propylene amide. Nylon 66 consists of glycolic acid and ethylenediamine. Although these two nylon cord has the same chemical molecular formula, but because of their different molecular stereo structure, the formation of intermolecular ammonia chain and the ability to obtain high crystallinity is different, so that the physical properties of the two show greater differences. Nylon fiber specific gravity of 1.14, strength 8 ~ 10g / d, torn elongation 18% ~ 30%, moisture absorption rate of 4.50%, friction resistance (Mo breaks the number of times) 2500, resistance to curvature and durability in water, nylon canvas can meet the quality requirements as a dam bag force skeleton.

 

Dam bag stitching according to the dam bag model, determine the polyamide canvas used line model, polyamide 6 and polyamide 66 have the physical properties are more in line with the requirements of the rubber dam bag canvas, so our country uses polyamide silk made of canvas to do the rubber dam dam bag force skeleton. But nylon 66 fiber physical and mechanical properties are better than nylon 6 (see table 1 below), better able to avoid the appearance of sewing and mending after the dam deformation is not the same and uneven, the top of the dam overflow depth is not the same as that caused by vibration of the dam bag and other phenomena.

 

 

Sewing should be based on the design of the stitch (≤ 5 cm), the purchase of nylon thread reprocessing, in accordance with its original twisting direction for the combined processing, processing of the wire diameter is generally for the dam bag cloth thickness of 1,3 1/2, after sticking and mending the strength of the dam bag than the original compressive strength of the dam bag to improve 2-3 times. In the rubber dam bag longitudinal cracks on both sides of the hole, in accordance with the design of the stitch, with a special needle tool and processed nylon thread, from the hole through the cracks on both sides of the sewing connection, and then the dam bag line knot at both ends, to increase its strength. When sewing, the seam is required to be tight and flat, neither lengthening the dam bag nor shortening it, and the two or more layers of tape its flatness must be good. If there are wrinkles or wrong corners then the force is not uniform, it greatly reduces the safety factor of the rubber dam bag.

 

3.2.4 Mixing glue slurry will be poured into the original glue slurry mixing basin to see the consistency of the original glue slurry, if the thinning of the thinning of a little less, if the thicker to add a little more thinning of the slurry, the slurry stirred evenly to be used, and so on, and then add a small amount of curing agent when you start to apply the glue slurry.

 

3.2.5 Brush glue slurry brush glue slurry before, with a prepared solvent scrub once, and then test the temperature, humidity, outdoor temperature 18 ~ 25 ℃, humidity below 70%, 2 cloth 3 glue as an example, the pre-prepared glue slurry stirred evenly, with a brush in the bonding surface brush glue slurry 3 times, the interval between each time due to the different temperatures vary, generally 30 ~ 45min after the first brush, and then brush the second time. After the 2nd brush 15 ~ 25min, and then brush the 3rd (depending on the local weather, to the adhesive volatilization in the non-sticky, to stick to the state of fine-grained silk as appropriate). Brush slurry must strictly control the thickness of the glue layer, and to ensure its uniformity. Glue layer <2mm, the bonding effect is reduced, affecting the adhesion between the two layers; glue layer >3mm, the construction cost increases. For a long time for the application of glue, adhesive patch area of large dam bag, glue should be applied by two people in the direction of the opposite direction to ensure that the bonding at the crystallization point of the glue paste is consistent. Avoid sun exposure, strictly prevent dust and dirt debris, can not get up glue bubbles. Reinforcement tape (film) and dam bag tape at the same time the same hair, cleaning, brushing glue.

 

3.2.6 Adhesion will be bonded to the inside of the longitudinal crack and a piece of adhesive tape right fit, from the center to the surrounding gradually compacted, with a hand roller repeatedly compacted lengthwise and crosswise, the discharge of air bubbles, shall not leave gaps and residual bubbles, and tamped with a rubber mallet, to ensure that the bonding surface is dense and solid. Reinforcement of the edge of the adhesive tape affixed to the sealing tape and compaction, and sandbags or other heavy objects flat pressure up to 24h or more (in the natural curing period, the bonded parts of the dam bag is not subject to folding, and to prevent water immersion), and then the bonding of the longitudinal cracks on the outside and the other piece of the bonded adhesive sheet in accordance with the above steps for bonding.

 

3.2.7 Installation to be adhesive strength to meet the requirements of the quality requirements of the dam bag cloth in accordance with the order of installation, compression bolts, lift the dam pressure test, to be no leakage of water after the anchoring line blocking, maintenance work is completed. The above work can be completed 48h after the dam can be lifted to run.

 

IV. Conclusion

The technology through the longitudinal large incision of the dam bag adhesive repair, small impact on the operation of the dam bag, significant benefits, applicability of a wide range of rubber dam dam bag repair work is more economical and efficient, so that the strength of the dam bag after the adhesive repair has been effectively safeguarded, has a strong practicality and operability.