In severe cold regions, the brittle fracture characteristics of geomembrane should be fully considered. Generally speaking, the geomembrane can withstand a low temperature as high as (- 45 ± 2) ℃, and the average coldest temperature in the north is generally about – 32 ℃. The geomembrane can meet the requirements of low temperature resistance and anti brittle fracture without interference. According to the laboratory test, the plasticity of the geomembrane disappears and the brittleness increases below – 5 ℃. The data shows that the geomembrane is easy to crack after tearing. The following are the precautions and brief construction methods for the winter construction of the geomembrane.
1. The settlement deformation of the foundation shall be avoided to cause brittle fracture of the geomembrane material. Therefore, the foundation shall be compacted layer by layer according to the design standard to ensure that the foundation is filled compactly.
2. The anti-seepage membrane shall be laid smoothly with appropriate tightness, and about 1.5% margin shall be reserved at the top of the slope to avoid tensile damage.
3. Frost heaving damage to the lining is an important problem in the construction of severe cold regions, which directly affects the seepage control effect and the normal operation of the project. To prevent frost damage of lining, comprehensive measures shall be taken from the aspects of planning layout, anti-seepage and drainage, thermal insulation, structural form of section, lining materials, management and maintenance, etc. The research shows that the basic factors of frost heaving damage are soil properties, soil moisture (water content and groundwater level) and negative temperature, which are indispensable. As long as one of these factors is eliminated, frost heaving will not occur.
4. For the geomembrane anti-seepage structure that has long been in contact with water in severe cold areas, thermal insulation lining can also be used, that is, thermal insulation interlayer is set between the geomembrane and the armor. Materials suitable for thermal insulation interlayer include polystyrene rigid foam board, pumice, ceramsite perlite, siliceous shale, etc. Polystyrene foam board has achieved good results as thermal insulation, anti freezing and slope protection of earth rock dam of reservoir and thermal insulation lining of large channel.