Recently developed geocomposite has sandwiched structure of woven fabric in between both non-woven fabric and has over the tensile strength of geogrids of woven fabrics and also having the drainage effect of non-woven fabrics. However, current design methods of non-woven fabric-reinforced earth fills have considered the drainage function only. Therefore, this paper propose a new design method of earthfill structures considering the reinforcing effect together with strength increase of the volcanic loam caused mainly by drainage.