In extreme temperature environments, the thermal expansion and contraction characteristics of HDPE geomembrane significantly affect the stability and durability of anchoring systems. The core mechanism lies in the interaction between material deformation and structural constraints. As a flexible impermeable material, the molecular chain structure of HDPE geomembrane undergoes thermal adjustment with temperature changes, leading to linear expansion or contraction. When the ambient temperature rises sharply, the molecular chain activity of the geomembrane increases, causing the material to elongate along the slope. If the anchoring system design does not allow sufficient deformation space, stress concentration will occur between the membrane and the anchoring structure, potentially causing membrane tearing or anchor loosening. Conversely, in low-temperature environments, material contraction can lead to membrane loosening, even detachment from the anchoring trench, forming leakage channels.
The stability of the anchoring system depends on the frictional resistance between the geomembrane and the foundation interface, and thermal expansion and contraction directly alter this key mechanical parameter. Under high-temperature conditions, the geomembrane softens, increasing the contact area with the slope. While this may temporarily increase frictional resistance, long-term thermal aging leads to a decrease in surface roughness, ultimately weakening frictional performance. For example, during the high temperatures of midday in summer, the geomembrane absorbs heat and becomes more flexible, resulting in a denser contact with the slope and increased frictional resistance. However, if the load within the anchoring trench is insufficient, the membrane may bulge due to localized elongation. In low-temperature environments, the material's embrittlement reduces its ductility. When the membrane shrinks, the anchoring points must withstand greater tensile stress; if the anchors are not strong enough, pull-out or breakage can easily occur.
Extreme temperature cycles also accelerate fatigue damage to the anchoring system. The thermal expansion coefficient of HDPE geomembrane differs from that of foundation materials such as concrete and soil. Under diurnal temperature variations or seasonal temperature fluctuations, periodic relative displacement occurs between the membrane and the anchoring structure. This fretting wear gradually weakens the pull-out resistance of the anchors. Especially in areas with freeze-thaw cycles, soil volume changes further amplify the stress amplitude at the membrane-anchor interface, leading to premature failure at the connection. For example, in cold northern regions, when the geomembrane shrinks in winter, the sidewalls of the anchoring trench may crack due to frost heave, compromising the integrity of the anchoring system.
To address the effects of thermal expansion and contraction, the anchoring system design must employ a strategy combining elastic constraints and rigid fixation. On one hand, buffer platforms or elastic anchors (such as spring-loaded pressure strips) can absorb the deformation energy of the membrane, preventing stress from being directly transferred to the fixed end. On the other hand, the dimensions of the anchoring trench and the loading method need to be optimized to ensure that the membrane maintains a certain preload during temperature changes. For example, adding a buffer platform in the middle of the slope and configuring adjustable anchors allows for dynamic adjustment of the ballast weight based on membrane elongation, maintaining system stability.
The construction process has a decisive impact on the anchoring system's resistance to thermal expansion and contraction. During installation, the principle of "tight during hot, loose during cold" should be followed, meaning the membrane should be appropriately loosened during high-temperature periods and moderately tightened during low-temperature periods, with sufficient allowance (usually 1.5%) to compensate for deformation. Welding processes require strict control of temperature and speed to avoid membrane embrittlement due to excessive melting, and a double-weld structure should be used to enhance joint strength. In addition, the backfill material for the anchoring trench should be well-graded crushed stone or sand to provide uniform frictional resistance and prevent localized stress concentration.
Long-term monitoring and maintenance are crucial for ensuring the reliability of the anchoring system. Regular checks are necessary to ensure anchors are not loose and that the membrane is not wrinkled or detached, especially after extreme temperature events (such as prolonged high temperatures or cold snaps). For anchoring systems that have deformed, their seepage prevention function can be restored through local repairs or the addition of anchor points. For example, patch membranes can be applied at the connection between the membrane and anchors, or chemical adhesives can be injected to enhance interfacial bonding.
The thermal expansion and contraction of HDPE geomembrane affects the anchoring system throughout its entire lifecycle, from design and construction to operation and maintenance. Through material modification (such as adding anti-aging agents to reduce the rate of thermal aging), structural optimization (such as using elastic anchoring technology), and scientific construction management, the system's adaptability to extreme temperature environments can be effectively improved, ensuring the long-term safe operation of the project.
