Anti-seepage effect of composite geomembrane
Composite geomembrane is developing rapidly in our country and is widely used. Composite geomembrane is a kind of anti-seepage material with fast construction speed, good waterproof effect, and low investment cost. It is especially suitable for the anti-seepage of hilly reservoirs, plain reservoirs, and old dams with small water storage depth.
The curve intersection method is a calculation method of composite geomembrane thickness, which can be used to calculate the geomembrane thickness of the low-head earth-rock dam surface, the geomembrane thickness of the reservoir pool slab, and the geomembrane thickness of the concrete building repaired with the geomembrane. For earth-rock dams with medium and high water heads, after laying the composite geomembrane, the dam body will undergo large deformation, and the finite element stress-strain curve method based on stress-strain calculation should be adopted. This method can be applied to the design of composite geomembrane thickness under various conditions.
The membrane in the composite geomembrane plays a role of impermeability, and the geotextiles on both sides play a role of stretching and protection. The thickness (density) and material of the geotextile have a great influence on stress and strain. Therefore, when selecting materials, the composite geomembrane needs to have an ideal stress-strain curve in addition to a higher ultimate tensile strength.
The stress and strain of the dam foundation are related to the construction sequence and deformation characteristics of the dam material. If the composite geomembrane is laid after the dam is filled, only the strain value caused by water storage is calculated; if the creep deformation of the dam material is large, the strain value caused by creep should be considered.
Considering the construction technology and safety margin, the finite element stress-strain curve method is adopted, that is, the effect of composite geomembrane stiffness is not considered. This is feasible when the stiffness of the asphalt concrete face rockfill dam is much greater than the composite geomembrane. However, when the stiffness of the gravel material is not very high, ignoring the influence of the composite geomembrane stiffness will have a certain impact on the calculation results. The degree of influence is not only related to the real simulation model of the composite geomembrane but also related to the laying relaxation of the composite geomembrane.