How to overlap composite geomembranes?

　　Composite geomembrane, as a new type of polymer material, is widely used in water conservancy engineering and environmental protection engineering. The connection methods between composite geomembranes include overlapping, bonding, welding, and other methods.

　　Due to its fast operation speed and high degree of mechanization, welding construction can greatly reduce the number of on-site personnel, shorten the construction period, and gradually become the main method for on-site installation and construction of composite geomembranes.

　　Welding methods include electric wedge, hot melt extrusion, and high-temperature gas welding.

　　Among them, electric wedge welding is the most widely used, and domestic experts and scholars have conducted in-depth research on hot wedge welding technology, obtaining some regular descriptions and quantitative indicators. According to relevant on-site tests, the tensile strength of composite geomembrane joints is more than 20% of the strength of the base material, and most of the fractures occur at non welded parts of the weld edge.

　　However, there are also some specimens whose tensile failure strength far fails to meet the design requirements or whose fracture directly starts from the weld position. This is related to factors such as the operation on the construction site, the selection of welding process, the responsibility of operators, and proficiency, which directly affect the realization of the anti-seepage effect of the composite geomembrane.

　　Especially in composite geomembrane welding, if welding occurs, the appearance of the weld seam meets the design requirements, but the tensile strength of the weld seam often does not meet the design requirements, and there may not be any problems in the short term. But considering the durability of the project, it will directly affect the realization of the anti-seepage life of the project. If problems occur, the consequences may be even more serious.

　　For this purpose, we conducted a tracking analysis of the welding construction of high-density polyethylene composite geomembrane and classified common problems during the construction process, in order to conduct differentiated research and identify quality improvement measures.

　　The common quality problems in the welding construction of composite geomembrane mainly include excessive welding, excessive welding, missed welding, wrinkling, and local welding of the weld bead.