landfill geomembrane

A landfill geomembrane is a high-performance waterproofing material primarily made from high-density polyethylene (HDPE). Its core function is to create a physical barrier between waste and the surrounding environment, preventing the leakage of leachate and harmful gases, thereby protecting soil and groundwater safety. This type of geomembrane is often referred to as "plastic armor" due to its excellent impermeability, corrosion resistance, and anti-aging properties, playing a critical role in modern environmental protection engineering.

I. Main Features and Application Mechanisms:

• Excellent Impermeability: The permeability coefficient of HDPE geomembrane can be as low as below 1×10⁻¹³ cm/s, equivalent to allowing only one water molecule to pass through every ten years, effectively preventing leachate from penetrating into the groundwater.

• Strong Chemical Stability: Resistant to acidic and alkaline environments within a pH range of 2–11, as well as various organic pollutants; high-quality products can retain more than 85% of their tensile strength even after 10 years of immersion in leachate.

• Resistance to Ultraviolet Radiation and Aging: With the addition of aging inhibitors such as carbon black, the material can be used in outdoor environments for over 50 years, exhibiting strong resistance to UV degradation.

• High Mechanical Strength: Elongation at break can reach up to 700%, providing excellent elasticity and adaptability to deformation, effectively accommodating uneven subsidence of foundations.

• Anti-Slip Design: During installation on slopes, single-sided or double-sided textured structures (textured height ≥0.25 mm) are commonly used, significantly increasing the friction coefficient with geotextiles and reducing the risk of landslides.

II. The following are mainstream selection recommendations based on industry standards and engineering practices:

‌1. Bottom Liner System (Primary Liner)‌

As the core impermeable barrier of a landfill, a HDPE geomembrane with a thickness of ≥1.5 mm is typically required.

· For hazardous waste landfills or projects with high waste piles and significant pressure, a thickness of 2.0 mm or greater is recommended to enhance puncture resistance and long-term stability.

· Applicable standards, such as the Technical Code for Closure of Municipal Solid Waste Landfill Sites (CJJ 112-2007) or municipal construction standard CJ/T 234-2006, explicitly specify that the thickness of the base liner must be no less than 1.5 mm.

‌2. Slope Liner System‌

Due to complex stress conditions and susceptibility to slippage, textured HDPE geomembranes with a thickness of 1.5 mm or 2.0 mm should be used to leverage surface friction and prevent membrane sliding. In steep slope areas, it is advisable to increase the thickness by 0.5 mm or adopt a double-layer structure to enhance safety.

‌3. Final Cover System (Terminal Closure)‌

When implementing permanent closure after landfilling is completed, the HDPE geomembrane serves as the impermeable layer, with a minimum thickness of no less than 1.0 mm.

· Various regulations, such as the Technical Specifications for Sanitary Landfill of Municipal Solid Waste, clearly stipulate that the thickness of HDPE membranes in synthetic material cover systems must not be less than 1 mm.

· In practice, geomembranes with a thickness ranging from 1.0 mm to 1.5 mm are commonly used, combined with protective layers such as geotextiles and drainage nets to function synergistically.

‌4. Temporary Cover Layer‌

For temporary applications during construction—such as localized rain protection or short-term containment—thinner HDPE geomembranes with a thickness >0.5 mm (e.g., 0.75 mm or 1.0 mm) may be selected to balance cost-effectiveness and practicality.