Abstract: Provided are a multilayer structure and the like being superior in adhesiveness of an interlayer under high humidity and separability of a barrier layer in water, and even in a case in which the barrier layer is exposed to water in a separating and collecting step, being superior in viscosity stability after separating and collecting a resin that constitutes the barrier layer. The multilayer structure of the present invention is a multilayer structure including a barrier layer (A), a water-soluble layer (B), and an adhesive layer (C), in which: the adhesive layer (C) is laminated via the water-soluble layer (B) on one or both faces of the barrier layer (A); the barrier layer (A) contains a polyamide or an ethylene-vinyl alcohol copolymer (a1) as a principal component; and the water-soluble layer (B) contains an alkali metal ion (b1) at a content of 100 ppm or more and 2,000 ppm or less.

Abstract: The present disclosure provides a multilayer structure in which a layer (A) made of a polyolefin resin composition (a), an oxygen barrier layer (B) and a sealant layer (C) are laminated in this sequence.

Abstract: There is provided a geomembrane consisting of a multilayer structure comprising a barrier layer (A), an adhesive layer (B) made of an acid-modified thermoplastic resin and a thermoplastic resin layer (C), wherein the thermoplastic resin layer (C) is laminated on at least one side of the barrier layer (A) via the adhesive layer (B), and the barrier layer (A) has an ethylene unit content of 18 mol % or more and 55 mol % or less and comprises a modified ethylene-vinyl alcohol copolymer comprising a modifying group having a primary hydroxyl group. The geomembrane exhibits excellent peer strength between the barrier layer and the adhesive layer, exhibits further improved peel strength after prolonged exposure to high temperature and high humidity conditions.