Construction measures of anti-seepage engineering when open pit is used as tailings pond

Construction Control of Geomembrane

Laying geomembrane on irregular slopes should focus on the following tasks:

1. Base layer treatment: Before laying geomembrane, the base layer should be cleaned up so as to be free of sundries and hard objects, and the construction should be carried out in sections according to the actual situation and construction capacity of the construction site.

2. Do cutting analysis, draw geomembrane laying and cutting drawings, check the appearance quality of geomembrane, record and repair the found mechanical damage and production wounds, holes and breakages and other defects.

3. There shall be no impurities such as dirt, sand, accumulated water (including water leakage) on the overlapping surface of the geomembrane. When laying geomembrane, the amount of expansion and contraction caused by temperature changes should be reserved according to the range of local temperature changes and the requirements of the factory product manual.

4. For the laying of geomembrane on the slope, the direction of the joints should be parallel or perpendicular to the maximum slope line, and should be laid in the order from bottom to top, and the membrane and joints should be properly placed on the slope at the bend of the slope. After the geomembrane is laid, before the protective layer is not covered, a 20-50kg sand bag should be placed at every 2-5m at the corner of the membrane, mainly to prevent its sliding displacement and wind damage. The geomembrane should be naturally relaxed and firmly attached to the support layer, and should not be folded or suspended.

5. When laying the film, pay attention to moderate relaxation, not tight. When the temperature is higher than 27℃, a larger relaxation degree should be reserved. Avoid stress concentration and man-made damage. When laying, the joint surface of the geomembrane and the concrete layer must be consistent and smooth, and there must be no protruding folds in the upstream and downstream directions.

6. When laying, the operator should wear soft-soled shoes and avoid walking on the membrane, so as not to damage the membrane.

7. The lap width of the bonded geomembrane is greater than 150mm, and the adhesive supplied with the geomembrane shall be used for pressure bonding on the connecting surface, and the seam shall be free of dust, grease and water.

8. To prevent the surface water from penetrating into the bottom surface of the geomembrane, the geomembrane should be sealed well, and the method of direct topping of concrete should be adopted according to the actual situation of the site. First, dig a groove with a width of 200mm and a depth of 100mm at the sealing of the geomembrane, fix the geomembrane on the rock in the groove with steel nails, and pour C15 concrete on the upper part to seal it.

Construction control of protective layer

According to the design requirements, the protective layer of the geomembrane is 100mm thick C15 concrete, and its function is to prevent the sun aging and cracking of the geomembrane. Due to the relatively large temperature changes in Northeast China, the temperature difference between winter and summer is more than 70 degrees, especially in the spring and autumn, the freezing and thawing phenomenon will cause the concrete protective layer to fall off; so on the basis of the original design, a layer of steel mesh is added to protect the 100mm thick C15 concrete. The layer is changed to 40mm thick M5 cement mortar protective layer. This prevents the protective layer from falling off due to freezing and thawing. In order to combine the base, geomembrane and protective layer organically, while laying the steel mesh, set up a bead every 3~5m. The bead is made of wood, 25mm wide and 10mm thick. It is to prevent the wire mesh from slipping off during the pouring of the mortar.

Summary: In the project of converting an open pit into a tailings pond, we have successfully achieved successful experience in laying geomembrane on irregular large slopes and preventing the protective layer from falling off.