How does the conical raised structure of a drainage board simultaneously achieve efficient drainage and water storage?
Publish Time: 2026-02-18
In modern green building, underground space development, and ecological landscape engineering, drainage board, as a key geosynthetic composite material, is widely used in roof gardens, underground garage roofs, basement sidewalls, and foundation drainage systems. Its core function is not only to quickly drain excess rainwater, preventing water accumulation from damaging the building structure and waterproofing layer, but also to provide a certain amount of water reserves for vegetation during dry periods.1. Three-dimensional cavity: Constructing a composite space of "drainage channel + water reservoir"Drainage board is typically made of high-density polyethylene or high-impact polystyrene through hot pressing or injection molding, with evenly distributed conical raised sections of 10–30 mm in height on its surface. When the drainage board is laid on top of the waterproofing layer and below the soil cover, the raised sections face downwards, adhering tightly to the waterproofing layer, forming a continuous, interconnected three-dimensional cavity network. These cavities form independent micro-"water storage units" vertically, temporarily storing some of the infiltrated rainwater; horizontally, the gaps between adjacent protrusions or the connecting channels at the bottom create low-resistance lateral drainage paths. Rainwater is initially trapped by the cavities; when the water volume exceeds the cavity capacity or rainfall continues, excess water quickly flows along the bottom plane of the board to the collection ditch or drain pipe, achieving intelligent water management of "storage first, then drainage, dynamic balance."2. Structural Parameter Optimization: Precise Control of Storage and Drainage RatioThe height, density, inclination angle, and top platform area of the conical protrusions directly determine the water storage volume and cross-sectional area of the drainage board. For example, higher protrusions can form larger cavities, increasing the water storage capacity per unit area, suitable for arid regions or roof gardens requiring extended plant irrigation cycles; while densely arranged small protrusions enhance overall compressive strength, suitable for garage roofs bearing thick soil cover or vehicle loads. In addition, some high-end drainage boards feature micropores or drainage channels at the base of the raised sections to guide water flow preferentially in a specific direction, preventing localized water accumulation. By adjusting these geometric parameters, engineers can customize the optimal combination of water storage and drainage performance based on project climate conditions, vegetation water requirements, and load requirements.3. Synergy with Geotextiles: Achieving Integrated "Filtration-Water Storage-Drainage"Drainage boards are typically used in conjunction with non-woven geotextiles. The geotextile covers the top of the raised section, preventing fine soil particles from entering the cavities and causing blockages, maintaining long-term unobstructed drainage. Furthermore, its capillary action slowly transports the water stored in the cavities upwards to the plant root zone, achieving "passive irrigation." This dual-layer structure of "geotextile filtration + drainage board storage and drainage" ensures the durability of the drainage system while improving water resource utilization efficiency. Field tests show that in typical roof gardens, vegetation using this system maintains good growth even after 7-10 days without irrigation, significantly reducing the frequency of artificial irrigation.4. Material and Structural Stability Ensures Long-Term FunctionalityHDPE or HIPS materials possess excellent chemical stability, UV resistance, and high/low temperature resistance, ensuring the drainage board remains undeformed and non-brittle in underground or exposed environments for extended periods. The conical protrusions often incorporate reinforcing ribs or honeycomb support structures, maintaining the cavity's stability even under soil pressure exceeding 200–500 kPa, thus preserving the effectiveness of the water storage space. Even under extreme rainstorm conditions, the system can rapidly drain excess rainwater within 30 minutes, preventing floating or structural damage.In summary, the conical protrusion structure of the drainage board successfully integrates the two major functions of "drainage" and "water storage" through spatial partitioning, parameter optimization, and system integration. It is not only a "safety valve" for building drainage systems but also a crucial carrier for rainwater resource utilization in sponge city construction, truly achieving a balance between ecological benefits and engineering reliability.
