Generally you just need to weld geomembrane instead of seam. Lower geotextile of composite geomembrane needs seaming.
In principle, it is needed, but mainly depending on site construction requirements.
Yes, but the operation is more troublesome.
In general, it does not need to seam (extending and folding together is ok). You only need to weld the geomembrane and seam the upper geotextile with handheld sewing machine. Geotextile is used as a protective layer of geomembrane to protect the impervious layer from being damaged. In order to reduce the ultraviolet radiation and increase the anti aging performance, you'd better use buried laying method. During construction, first, level cardinal plane with small sand or clay, then pave. Do not stretch too tight when paving. Both ends buried in soil is corrugated. Finally, pave a transition layer of about 10cm with fine sand or clay on two cloths and one membrane and build scour prevention layer with 20-30cm stone (or precast concrete block). In construction, you'd better build the packaging layer while paving membrane edge to try to avoid the stones hit directly on it. The connection between two cloths and one membrane and surrounding structures should be anchored by expansion bolt and steel plate depression bar, painted with emulsified?asphalt (2mm thick) to stick and prevent leakage. Construction joint treatment is a key process, which directly affects the anti-seepage effect. General joint methods are: ① lap: lap width should be larger than 15cm; ② hot?welding: suitable for thicker geomembrane substrates, and lap width of weld should be not less than 5cm.
