... highway ,tunnel HDPE double-wall corrugated pipe using HDPE as main material, and adds various plastic additives,then by twin-screw extrusion, a pipe ... in the drainage of railway ,highway ,tunnel , waste landfill, green belts ,sports ground and slopes with high water content, etc ... ≤30×3mm surface should be homogeneous ,and the inner wall should be smooth , no burr. HDPE double-wall corrugated pipe