Analysis of the construction method of bentonite waterproof blanket in artificial lake
1. Introduction of Bentonite Waterproof Blanket
Bentonite waterproof blanket is a new type of geosynthetic material. It is made by filling sodium bentonite particles between woven geotextiles and non-woven geotextiles, and connecting the upper layer of non-woven fabric fibers to the lower layer of woven fabrics through bentonite particles, special processes and equipment. completed. The bentonite particles in the waterproof blanket made by this method do not flow in one direction, so a uniform waterproof layer can be formed in the whole range. It is an excellent waterproof and anti-seepage material, and can be widely used in many construction conditions. project.
Second, the scope of application of bentonite waterproof blanket
Bentonite waterproof blanket is suitable for anti-seepage and waterproof treatment of structures with water storage characteristics such as artificial lakes, reservoirs, large swimming pools, fish farms, channels, garbage disposal sites, etc. Anti-seepage and waterproof engineering of buildings in areas with large temperature difference, and anti-seepage, sealing and isolation of subways, pools, water diversion channels, etc.
Three, the outstanding advantages of bentonite anti-seepage blanket
1) Permanent waterproof. It is composed of natural bentonite, which will not age; it is very environmentally friendly, can keep the water body clean, and has no effect on the growth of aquatic animals and plants.
2) The permeability coefficient is extremely low, the permeability coefficient is only 10-9em/s, and the anti-seepage hydrostatic pressure can reach more than 1.0MPa.
3) The construction is simple and not limited by the temperature of the construction environment, and it can be constructed at minus 32~C.
4) The construction is simple, just backfill after laying.
5) The lap joint laying can resist the uneven subsidence and frost heave effect of the geology.
6) No special installation equipment is required.
7) Bentonite waterproof blanket has the characteristics of self-healing, easy to repair, and not afraid of being punctured by small sharp objects. If the waterproof layer is accidentally damaged, it is only necessary to simply repair the damaged part. Reduce annual maintenance engineering costs and reduce engineering costs.
4. Construction method
1. Construction preparation
1) Do the cutting analysis, and draw the laying sequence and cutting diagram of the bentonite waterproof blanket according to the design requirements or engineering conditions (the auxiliary tools are ready). Analyze the terrain conditions to be laid, arrange the sequence, the length and width of the material, predict the allocation of reasonable cutting drawings and plans, and prepare for cutting.
2) Check the appearance quality of the bentonite waterproof blanket, record and repair the found defects such as wounds and voids.
3) Prepare a flat open space of more than 8in×10m for unloading and lofting and cutting.
4) Prepare a small amount of water and a bucket with a diameter of 40cm and a depth of 50em in order to prepare the bentonite paste (colloid).
5) Material stacking: The site where the waterproof blankets are stacked should be selected at a higher terrain. The waterproof blankets should be stored overhead to prevent moisture, and a material shed should be erected if necessary.
5. Basic requirements
The surface of the foundation must be flat, uniform, and the degree of compaction is more than 85%, so as to avoid the damage caused by the sinking of the foundation during the use process, which will bring unfavorable factors to the permanent use. And the slope and elevation are within the allowable error range. The quality of the base surface should meet the design requirements: the bottom surface of the foundation pit, the slope surface and its slope ratio, the reinforced grooves on the slope, and the treatment of the junction between the slope surface and the bottom surface should all strictly meet the design requirements. The yin and yang corners on the base surface should have a smooth transition, and the radius should be >0.5in, and meet the design requirements of the drawings. There should be no obvious accumulation of water on the surface. The construction of bentonite waterproof blanket should be carried out after the acceptance of the foundation project.
6. Construction and laying
The seepage control of artificial lakes mainly includes slope, elevation (or revetment) construction and bottom construction, but it generally requires continuous overall arrangement. The bentonite waterproof blanket shall be laid in sections and blocks in the specified order and direction, starting from the lowest point of the corresponding construction section. Manual laying is used, and multiple people are required to exert even force when laying, and it is not allowed to tear, drag, and spread out. It is strictly forbidden to wear spiked shoes and high heels on the bentonite waterproof blanket. The seams between the blankets should be staggered, and it is not advisable to form a through seam. The overlapping surface of the bentonite waterproof blanket shall not have impurities such as sand, accumulated water (including dew) that affect the quality of the overlapping. The construction of bentonite waterproof blanket should be carried out in the weather without rain and snow. If it rains during construction, the snow should be covered with plastic film to prevent the waterproof blanket from hydrating in advance.
7. Laying construction on the bottom of the lake
When the bottom surface is laid, it should be lapped in parallel, not parallel butt, and it should not be stretched too tightly. It should be relaxed and close to the ground.
1) The laying of the waterproof blanket should be artificially laid.
2) According to the prescribed order and direction, the waterproof blankets are laid in partitions and blocks. The waterproof blanket should be formed into a cloth with the characters, and try to avoid the appearance of cross-shaped overlapping.
3) The geotextiles on both sides of the waterproof blanket are non-woven fabrics and woven fabrics respectively, and the non-woven fabrics are facing upwards when laying. When laying to the reinforcement part, the temporary PE protective film needs to be removed before continuing to lay.
4) The lap width of the waterproof blanket should be 250mm, and the bentonite powder sealant with a width of 50mm should be sprinkled on the edge 150mm of the lapped bottom waterproof blanket, and the weight is 0.5kg/m. In case of strong winds, the powder sealant can be mixed into a paste with the same amount of water, and applied to the blanket according to the above requirements.
5) The waterproof blanket should be naturally relaxed and the support layer should be firmly attached, and should not be folded or suspended in the air.
6) When laying waterproof blankets at the borders of the river bottom, the waterproof blankets should be well overlapped with the waterproof blankets reserved on the slope or bank protection.
7) During the laying process, the appearance of the waterproof blanket should be checked at any time for damage, holes, etc. When holes or damages are found, they should be repaired with bentonite or paste in time, and a waterproof blanket of ~25cm or more around the damaged part should be used to cover and repair locally.
8. Laying construction of facade revetment and slope bank
1) When laying the slope, it should be laid along the top-to-bottom direction of the slope and overlapped in parallel; the overlap should be flat and the overlap length should be ~>300mm. Sprinkle 0.4-0.6kg/m of bentonite powder evenly on the lap joints. The edge laying height is 100mm higher than the design water level.
2) When the waterproof blanket is overlapped in the construction of the underground building facade, the revetment should be made into a circular arc or an obtuse angle at the yin and yang corners of the wall construction, and the 400mm width of the waterproof blanket should be cut out at the inner corner for reinforcement treatment, and then large surface laying. When laying the bentonite waterproof blanket on the facade of the revetment, in order to avoid it being untrue, it can be fixed with 25mm long steel nails and spacers.
3) When laying bentonite waterproof blankets on facades and slopes, in order to prevent them from sliding, they can be fixed with pins and gaskets. In addition to fixing with steel nails at the overlapping parts and edges of the waterproof blankets, the middle of the entire waterproof blanket also needs to be fixed. Depending on the flatness and nails, the waterproof blanket is required to be installed on the wall and the ground firmly and docilely. The laying and overlapping of the bentonite blanket should be parallel to the direction of the slope.
4) The nail holes and overlapping parts should be treated with paste bentonite sealant.
5) The waterproof blanket at the bottom of the revetment should be overlapped and fixed with the waterproof blanket on the bottom surface to form a complete waterproof system.
6) When the waterproof blanket is lapped on the façade, the bentonite powder is mixed with water into a paste and applied to the lap joint.
7) The waterproof blanket should try to avoid overlapping between the facade and the bank. If the waterproof blanket needs to be overlapped between the facade and the slope bank, the waterproof blanket at the high place should be on the outside and the waterproof blanket at the low place should be at the inside (close to the wall) to prevent foreign objects from entering the overlap during backfilling. sew.
8) After the façade and slope bank are laid, leave a waterproof blanket of sufficient length (≥2m) on the bottom surface to facilitate the overlap with the large-surface waterproof blanket at the bottom of the lake, and protect the edge with PE film to avoid the waterproof blanket encountering prematurely. Water expands.
Nine, damage repair
1) The damage of the geotextile on the outer surface of the bentonite waterproof blanket should be covered with a geotextile patch, each side exceeding 300mm, and welded by hot melt method.
2) Check all bentonite waterproof blankets and seams. Defective bentonite waterproof blanket sheets and seams are clearly marked on the bentonite waterproof blanket and repaired in time.
3) If the number of patches in a place is too much, then the whole place is repaired with a whole patch or a bentonite waterproof blanket web.
4) If the bentonite waterproof blanket is damaged during installation (tear, puncture, etc.), it can be repaired by cutting 4 "patches" from a new roll of bentonite blanket and covering the damaged area. The length of the four sides of the patch from the damaged place is >300mm. Before laying the "patch", some granular bentonite or bentonite slurry should be sprinkled around the damage.
10. Construction quality inspection
After the waterproof blanket is laid, its quality should be inspected by the quality inspection and supervision personnel, and the following 9 processes should be paid attention to:
1) Whether all lap joints (seams) meet the requirements.
2) Whether the damaged repaired parts meet the requirements.
3) Whether the parts that were not qualified in the previous inspection and were repaired again meet the requirements.
4) Whether the connection between the waterproof blanket and other equipment, infrastructure, etc. meets the requirements.
5) Whether the parts fixed by the steel nails meet the requirements.
6) Whether the waterproof blanket and its overlapping parts are firmly attached to the base layer, and whether there are folds and suspension.
7) Confirm that the waterproof blanket does not expand in the early stage due to contact with water.
8) Whether the backfill or protective layer meets the requirements.
9) The quality inspection should be carried out with the construction progress. After passing the self-inspection, it should be inspected by the supervisor. After the acceptance is passed, the next process can be carried out.