HDPE Geomembranes for tailings ponds in Guatemala-N

I、Definition and characteristics of geomembrane

Definition

HDPE geomembranes is an impervious film made of polyethylene, polyvinyl chloride and other high polymer by special process. Its molecular structure is tight, with very low porosity, can effectively prevent the penetration of liquids and gases, in all kinds of civil engineering, especially tailings engineering, shouldering the key mission of seepage prevention and isolation.

Peculiarity

l Excellent impermeability: HDPE geomembranes, its permeability coefficient can reach 10⁻¹²cm/s below, can almost completely block the penetration of liquid. In a large gold mine tailings pond in Guatemala, after using HDPE geomembranes to prevent seepage, the seepage of leachate decreased from about 8000 cubic meters per year to less than 150 cubic meters, and the anti-seepage effect was extremely significant.

l Good chemical stability: HDPE geomembranes has excellent resistance to common chemical substances such as acid and alkali. In the complex chemical environment of the tailings pond, it is difficult for the tailings to be eroded by various chemical agents and heavy metals.

l High mechanical strength: HDPE geomembranes has strong tensile strength and puncture resistance, and can withstand the huge pressure generated by tailings accumulation and mechanical collision during construction.

II. HDPE Geomembranes thickness price list

Thickness (mm)	Price (USD/m2)
0.5	0.7 - 0.9
1	1.4 - 1.6
1.5	2.0 - 2.3
2	2.8 - 3.2

III. Analysis of applicable thickness of HDPE geomembranes and its relationship with environment

0.5mm thickness

The price is relatively low, and it is suitable for small tailings ponds or the initial stage of tailings accumulation. At this time, the pressure of tailings is small, and the causticity of leachate is relatively weak. For example, in the initial tailings stacking site of some small lead and zinc mines in Guatemala, the use of 0.5mm thickness HDPE geomembranes can meet the basic seepage prevention needs in the short term, and the cost is low.

1.0mm thickness

With moderate price and good comprehensive performance, it is widely used in medium-sized tailings ponds. It has reliable barrier ability to common heavy metal ions and general chemical agents. For example, after a medium-sized copper mine tailings reservoir uses 1.0mm thickness HDPE geomembranes, continuous monitoring data show that the heavy metal content in the surrounding soil and groundwater is within the range of safety standards.

1.5mm thickness

Suitable for large tailing ponds or tailings with strong corrosive environment. Its higher strength and impermeability can withstand greater pressure and chemical erosion. In the treatment of tailings containing a large number of acidic tailings, the 1.5mm thickness of HDPE geomembranes can maintain good performance for a long time, effectively prevent leachate leakage, and ensure the safety of the surrounding environment.

2.0mm thickness

It is mainly used for special tailings ponds with high safety and environmental protection requirements, such as treatment sites containing radioactive tailings or highly toxic heavy metal tailings. Its strong anti-puncture, anti-tear and anti-seepage properties provide a reliable protective barrier for such high-risk tailings ponds, which can minimize the risk of environmental pollution.

IV. Preparation before laying

l Preparation before laying

The bottom and slope of the tailings pond are comprehensively cleaned and levelled to ensure that the foundation surface is solid and smooth. Cut the HDPE geomembranes precisely according to the actual size of the tailings pond. At the same time, carefully check the quality of HDPE geomembranes to ensure that there are no defects such as damage and holes.

l Laying process

Starting from the bottom end of the tailings pond, the HDPE geomembranes is gradually laid from low to high. When laying, it is necessary to ensure that the HDPE geomembranes is smooth and avoid folding and hanging. For the part of the slope, special processes need to be used, such as the use of anchoring trenches to fix the edge of the HDPE geomembranes on the slope to ensure that the HDPE geomembranes is closely fitted to the slope.

l Splice processing

HDPE geomembranes splicing mainly adopts welding or bonding method. Welding is a common method, using a special welding machine, welding speed is adjusted according to the thickness of the HDPE geomembranes, to ensure that the weld is firm and sealed. After the welding is completed, the weld quality must be tested, such as using the inflation method to test the tightness of the weld to ensure that there is no leakage at the splice.

V.Comparative effect of HDPE geomembranes before and after use

l Comparison of leakage control

Before the use of HDPE geomembranes,some tailings ponds in Guatemala had serious leakage problems, for example, the lead content in the soil around an old tailings pond was more than 10 times higher than the standard, and the groundwater quality deteriorated. After the use of HDPE geomembranes for seepage prevention, the seepage of leachate has been effectively controlled, the pollution trend of surrounding soil and groundwater has been contained, the heavy metal content in soil has gradually decreased, and the groundwater quality has also been improved.

l Stability comparison

When no HDPE geomembranes is laid, the slope of tailings reservoir is easily destabilized by rain erosion and tailing accumulation pressure. According to statistics, some unprotected tailings ponds in Guatemala need to be repaired several times a year due to slope instability. After the HDPE geomembranes is laid, the stability of the slope is significantly improved. Due to the increased friction between the HDPE geomembranes and the tailings, as well as the protection against rain erosion, the number of slope instability is greatly reduced, reducing the safety risk and maintenance costs.

VI、 Conclusion

The application of HDPE geomembranes in the tailings pond in Guatemala has greatly improved the safety and environmental protection of the tailings pond. Effectively reduce the pollution risk of tailings ponds to the surrounding environment, and provide a solid guarantee for the sustainable development of Guatemala's mining industry. With the continuous development of the mining industry, the application of HDPE geomembranes in the construction of tailings ponds will continue to optimize and expand, and contribute more to the coordinated development of environmental protection and resource development.

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