Sponge City Construction and Geosynthetics (2): Types and Mechanism of Geosynthetics
Geosynthetics is an important part of LID (low impact development) facilities in sponge city application. In view of the "seepage and stagnation" measures, geosynthetics should be able to play the functions of infiltration and filtration, ensure that rainwater effectively infiltrates into the soil and minimize the amount of rainfall discharged into the pipeline system. For the "storage and purification" measures, geosynthetics should be able to play the role of water storage and purification. The function ensures that the rainwater can be retained as effectively as possible, and works together with sand and stone to purify the water quality and effectively store rainwater. In view of the "use and drainage" measures, geosynthetics should be able to ensure smooth drainage, good hydraulic conditions and filter conditions to ensure that it is not easy to silt up and achieve the goal of comprehensive utilization of rainwater.
Geosynthetics can play an important role in the construction of sponge cities, including geogrids, geotextiles, geomembranes and rainwater storage modules.
Rainwater Storage Module
Green roof relies on the water conservation and water storage function of roof vegetation and soil matrix to reduce roof runoff and relieve urban drainage pressure. The filter layer of geosynthetics should ensure that the fine particles in the improved soil are not lost in the process of rainwater seepage, and the vertical seepage ability should be guaranteed. The use of drainage plate can quickly remove the seepage rainwater in a planar drainage way to ensure the effect of rainwater transmission. Waterproof layer ensures that excessive rainwater does not damage the structural layer and ensures the safety of green roof. Therefore, geonets, geotextiles and other materials through filtration, seepage, prevention measures to ensure the green roof in the total amount of rainwater runoff control effect. In addition, considering that the roof is more sensitive to load, if using gravel material to filter, it will increase the load of the roof, so geotextiles with small load and convenient laying should be used to filter.
In the construction of sponge city, the rainwater outlet of concave greenbelt (vegetation retention trough) is arranged in the greenbelt. The elevation of rainwater outlet is higher than that of greenbelt but lower than that of road surface, and the orifice edge stone is used to replace the strip edge stone. Between perforated drain pipe and gravel layer, it is necessary to consider wrapping anti-seepage geosynthetics to prevent fine particles from entering drain pipe during rainwater seepage. At the same time, wrapping anti-seepage geosynthetics should also be considered in gravel layer and soil base to ensure the long-term use of perforated drainage pipes without silting up.
In rainwater gardens, geosynthetics are mainly used between aquifer and overburden, perforated pipe and gravel layer. The aquifer and overburden should be equipped with anti-seepage geosynthetics to ensure the effect of water storage. The perforated pipe and sandstone layer should be equipped with filter geosynthetics to ensure smooth drainage. The structure of sunken green space is usually turf + planting soil + gravel + geotextile + plain soil compaction. Geotextiles are mainly used for filtration, which requires long-term drainage infiltration between gravel and plain soil.
Ecological slope protection is often adopted in the slope protection structure of urban water system. In order to ensure the stability of the slope, geosynthetics can be considered to reinforce the slope. In order to avoid rainwater scouring into runoff ditches, geonet cushions and other slope protection materials can be considered. In addition to geonet cushion materials, high-quality polyamide (PA6) as raw material for soil and water conservation blankets can also replace the traditional slope protection structure, which has a good effect on the control of runoff peak.
Geosynthetics, as an important component of low-impact development facilities, is playing an irreplaceable role in promoting the construction of sponge cities in an all-round way. How to make rainwater more effective "natural accumulation, natural infiltration, natural purification"? Geosynthetics technology should start from integration, high efficiency, economic aspects, and further research, play a key role in technological guidance in the change of the concept of rainwater control. Geosynthetics, as an important component of low-impact development facilities, is playing an irreplaceable role in promoting the construction of sponge cities in an all-round way. How to make rainwater more effective "natural accumulation, natural infiltration, natural purification"? Geosynthetics technology should start from integration, high efficiency, economic aspects, and further research, play a key role in technological guidance in the change of the concept of rainwater control. Teandersheng Building Materials Co., Ltd. welcomes your call to consult geosynthetics geogrid, geotextile, geomembrane, tunnel waterproof board and other geotechnical materials.