Geomembrane

HDPE membrane, full name "High-Density Polyethylene Membrane," offers excellent resistance to environmental stress cracking, low-temperature resistance, aging resistance, corrosion resistance, a wide operating temperature range (-60 to +60°C), and a long service life (50 years).

HDPE geomembrane, full name "High-Density Polyethylene Geomembrane," provides excellent resistance to environmental stress cracking, low-temperature resistance, aging resistance, corrosion resistance, a wide operating temperature range (-60 to +60°C), and a long service life of 50 years. It is widely used in anti-seepage projects such as municipal solid waste landfills, solid waste landfill liners, wastewater treatment plants, artificial lakes, and tailings management.

HDPE Geomembrane Installation Design

1. Before laying the HDPE membrane, corresponding qualified acceptance documents for the civil engineering work should be obtained. 2. Before cutting the HDPE membrane, accurately measure the relevant dimensions and cut according to the actual size. It is generally not advisable to cut based on the illustrated dimensions. Each piece should be numbered and recorded in detail on a dedicated form.

3. During the laying of the HDPE membrane, strive to minimize the number of welds. Under the premise of ensuring quality, conserve raw materials as much as possible. This also facilitates quality assurance.

4. The overlap width between membrane seams should generally be no less than 10 cm. Typically, the weld lines should be arranged parallel to the direction of the steepest slope, i.e., along the slope direction.

5. At corners and irregular sections, the seam length should be minimized as much as possible. Unless otherwise specified, avoid placing welds within 1.5 meters of the top slope or stress concentration areas on slopes steeper than 1:6.

6. During the laying of the HDPE membrane, avoid creating artificial wrinkles. At lower temperatures, the membrane should be stretched taut and laid flat.

7. HDPE membrane laying completed

Construction Process

The anti-seepage system for the Zhou Tou Reservoir dam composite geomembrane adopts a cyclic process of excavation, laying, compaction, and protection in sections.

Base Surface Preparation

The base surface must be cleaned according to design requirements, which is crucial for ensuring anti-seepage effectiveness. Particularly, sharp stones, tree roots, and other debris must be thoroughly removed. The base surface should not have localized unevenness. The prepared base should be compacted with a rammer or compactor to achieve density and levelness.

Composite Laying When laying the membrane, it must be installed from the bottom upward. The membrane should be pressed flat and snug against both adjacent membranes and the base surface, but not overly tight. It should generally be slightly loose, without leaving air bubbles underneath. Since geomembranes are thin and lightweight, they can easily be blown by wind before the protective layer is placed. Therefore, the area of membrane laid at one time should not be too large. It is advisable to cover the laid membrane with protective soil material as you go.

According to data provided by Shenzhen Zhonghe, the width of the composite geomembrane is 1.0~1.9m. This project uses a 1.9m width to reduce joint material usage. Joint methods include heat bonding, adhesive bonding, and overlapping. This project design uses adhesive bonding with a seam width of 50mm.

If punctures or tears are found in the geomembrane, they must be patched with geomembrane adhesive covering an area three times the size of the damage.

Protective Layer

The protective soil layer, 10cm thick adjacent to the geomembrane, must be sieved. Particles larger than 6mm are not allowed, as they can puncture the geomembrane. The protective soil must be compacted to ensure a dry density greater than 1.5, with samples taken for inspection. When backfilling the protective layer and laying the riprap armor, handle materials gently to avoid damaging the geomembrane. Beneath the riprap armor, a 100mm thick layer of crushed stone or gravel should be placed to prevent scour of the soil protection layer due to water level changes, waves, etc. Dry-laid riprap should be manually laid with guidance lines, with stones tightly interlocked. The individual weight of surface stones should exceed 48kg, and all gaps filled with smaller stones.

Perimeter Treatment

The requirement for perimeter joint treatment is to tightly connect the composite geomembrane with the surrounding soil, seal potential seepage entry points, cut off lateral seepage paths, and prevent water from entering beneath the geomembrane and forming blisters that could burst the membrane when the reservoir level drops. Therefore, a cutoff trench must be excavated around the perimeter, and the geomembrane buried within it.