Drainage board with a special plastic sheet extrusion process will be closed to the protruding cylinder shell to form a bump-like membrane, shell continuous, with a high degree of three-dimensional space and some supports, can resist the long-term high-pressure, no deformation. Shell top cover geotextile filter layer, to ensure that the drainage channel will not be blocked by foreign objects and, as particles or concrete backfill.

Drainage board with a special plastic sheet extrusion process will be closed to the protruding cylinder shell to form a bump-like membrane, shell continuous, with a high degree of three-dimensional space and some supports, can resist the long-term high-pressure, no deformation. Shell top cover geotextile filter layer, to ensure that the drainage channel will not be blocked by foreign objects and, as particles or concrete backfill.

Drainage board with a special plastic sheet extrusion process will be closed to the protruding cylinder shell to form a bump-like membrane, shell continuous, with a high degree of three-dimensional space and some supports, can resist the long-term high-pressure, no deformation. Shell top cover geotextile filter layer, to ensure that the drainage channel will not be blocked by foreign objects and, as particles or concrete backfill.