Three-dimensional composite drainage network

Three-dimensional drainage network is also called drainage board, which is a new type of drainage geotechnical material. Using high-density polyethylene (HDPE) as raw material, it is processed by a special extrusion molding process and has a three-layer special structure. The middle rib has high rigidity and is arranged longitudinally to form a drainage channel. The upper and lower ribs form a support to prevent the geotextile from being embedded in the drainage channel, and can maintain high drainage performance even under high load. Double-sided bonded water-seepage geotextile composite use, with "reverse filtration - drainage - ventilation - protection" comprehensive performance, is currently an ideal drainage material.

Characteristics of 3D Composite Drainage Network

1. When the load is 720kPa and the gradient is 2%, the permeability is 2500m/d and the flow rate is 13pm/m.

2. The creep test retains more than 60% of the thickness after bearing a load of 1200kPa for 10,000 hours.

3. The carbon black content of the three-rib drainage mesh core is not less than 2%, the density is 0.94g/cm3, the tensile strength is not less than 36.5kN/m, the melt index is 1.0 g/10min, and the thickness is 7.6mm.

4. The apparent pore size of the non-woven geotextile is 0.18mm, the water permeability is 0.26 Sec-1, the permeability is 0.2cm/sec, the puncture strength is 580N, the trapezoidal tear strength is 356N, the holding tensile strength is 900N, and the holding extension strength is 50%, burst strength 2750kPa.

Application of 3D Composite Drainage Net

1. It is laid between the foundation and the sub-base to drain the accumulated water between the foundation and the sub-base, block the capillary water and better integrate it into the edge drainage system. This structure automatically shortens the drainage path of the foundation, the drainage time is greatly reduced, and the amount of selected foundation materials can be reduced (that is, materials with more fines and lower permeability can be used). Extend the life of the road.​​

2. Laying a three-dimensional composite drainage net on the sub-base can prevent the fine material of the sub-base from entering the sub-base (that is, it plays a role in isolation). The aggregate base layer will enter the upper part of the geonet to a limited extent. In this way, the composite geotechnical drainage net also has a potential effect of limiting the lateral movement of the aggregate base, in this way, its effect is similar to the reinforcement effect of the geogrid. Generally speaking, the tensile strength and rigidity of composite geodrainage mesh is better than that of many geogrids used for foundation reinforcement, and this restriction will improve the support capacity of the foundation.

3. After the road is aging and cracks are formed, most of the rainwater will enter the section. In this case, the three-dimensional composite drainage net is laid directly under the road surface instead of the drainable foundation. The three-dimensional composite drainage mesh can collect moisture before it enters the foundation/subbase. Moreover, the bottom end of the three-dimensional composite drainage net can be wrapped with a layer of film to further prevent moisture from entering the foundation. For rigid road systems, this structure allows the road to be designed with a higher drainage coefficient Cd. Another advantage of this structure is the possibility of more uniform hydration of the concrete (studies on the extent of this advantage are ongoing). Whether for rigid road or flexible road systems, this structure can extend the service life of the road.

4. In northern climate conditions, laying a three-dimensional composite drainage network can help reduce the impact of frost heave. If the freezing depth is deep, the geonet can be laid at a shallower position in the sub-base to act as a capillary blockage. It is also often necessary to replace it with a granular subbase that is less prone to frost heave, extending down to freezing depths. The backfill soil that is easy to frost heave can be directly filled on the three-dimensional composite drainage network until the ground line. In this case, the system can be connected to a drain outlet so that the water table is at or below this depth. This could potentially limit the development of ice crystals without limiting traffic loads when ice melts in spring in cold regions.

Seams and Overlaps of 3D Composite Drainage Mesh

1. Adjust the direction of the geosynthetic material so that the length direction of the material roll is perpendicular to the road. 2. The composite geotechnical drainage net must be terminated, and the geotextiles on the adjacent geonet cores are overlapped along the material roll.

3. Connect the geonet cores of adjacent geomaterial rolls with white or yellow plastic buckles or polymer tapes to connect the material rolls. Tape every 3 feet along the length of the roll of material.

4. The direction of the overlapped geotextile should be consistent with the direction of the packing. If the geotextile is laid between the foundation/base layer and the sub-base, continuous wedge welding, flat head welding or stitching shall be carried out to fix the overlapping geotextile upper layer. If stitched, a flat stitch or general stitch is recommended to achieve the minimum stitch length.