Introduction

HHD(Harmonica type horizontal drain) is a fully filtered, prefabricated subsoil drainage system widely used around world. It consists of a plastic inner Harmonica core overwrapped withageotextiles filter fabric. HHD is placed under the surcharge to receive the flow from the vertical drains and conduct it laterally to discharge points at the edge of the surcharge. In most cases the installation of HHDR is less expensive than a aggregate or sand drainageblanket.

Shape and type

Comparison of horizontal drainage method

Benefit

Low cost

- Installation and material cost is half than gravel or sands

- Easy to store and transport.

High Drainage efficiency

- Structure of core provides multiple channels for vertical and horizontal water flow.

- Filter fabric permits high volume entry of water into core while restraining soil particles.

Workability

- Lightweight, flexibility easy-to-handle

- No heavy equipments or skilled laborers are required.

Confidence

- Uniform properties and quality assure predictable drain performance.

Application

Substitution for sand mat

Road construction

Method of installation