To fight against the epidemic, every second counts! Modeled on the model of Xiaotangshan Hospital in Beijing, Huoshenshan Hospital and Leishenshan Hospital are specially designed to treat patients with new coronavirus pneumonia. From the beginning to the present, hundreds of machines have resonated, thousands of workers have worked hard, and tens of millions of netizens have cheered. 8 Within days, a hospital with a capacity of 1,000 beds was officially completed – Huoshenshan Hospital. “China Speed” once again created the “Chinese Miracle”.
In this construction process where every minute counts, why do we need to lay a layer of membrane on the foundation first?
This membrane is called HDPE (high-density polyethylene) anti-seepage membrane, also called HDPE geomembrane. It has good chemical resistance and its main function is to control the amount of seepage and delay it. Diffusion of pollutants, it can effectively prevent the wastewater and waste liquid generated by the hospital from penetrating into the surrounding soil and groundwater, causing pollution of the soil and water environment.
Why choose HDPE (high density polyethylene)?
PE has low cost and is easy to stretch. Its chemical properties are greatly affected by density, crystallinity and relative molecular mass. It is divided by density, mainly low-density polyethylene. (LDPE) and high-density polyethylene (HDPE). According to statistics, PE ranks third in usage of geotextiles globally. High-density polyethylene (HDPE) has good temperature resistance, high mechanical strength and creep resistance, and is suitable for the production of geogrids. It is currently one of the main materials for the production of geogrids in my country.
Why choose the “two cloths and one membrane” structure ?
A composite geomembrane can be made by hot-rolling the geomembrane and geotextile through guide rollers. It has the advantages of good anti-seepage effect, high strength, aging resistance, and light weight. According to the composite form, it can be divided into one cloth and one film, two cloths and one film, two films and one cloth, etc. In actual projects, composite geomembranes with two cloths and one membrane are mostly used because the upper and lower fabrics can protect the middle layer of anti-seepage geomembrane from punctures by sharp corners of gravel, and this composite form is different from other composite geomembranes. Compared with, it has greater tensile strength and better anti-seepage performance.
“Two cloths and one film” laying
The construction of Huoshenshan Hospital is based on the standards of landfills. The construction structure is a “two cloth and one membrane” structure, that is, “two layers of geotextile and one layer of HDPE anti-seepage membrane”. On the flat ground, lay sand with a thickness of 20cm and intersperse it with the pipes. Then “two cloths and one membrane” will be laid on it – two layers of geotextile and a layer of HDPE anti-seepage membrane, and then laid 20cm sand has strong anti-seepage effect.
What are the other uses of HDPE film?
Industrial land, gas stations, abandoned warehouses, abandoned residential areas that may contain lead or asbestos, “brownfields” containing chemical waste residues, cities with toxic and hazardous substances Garbage disposal sites and burying sites for waste pollutants require the use of anti-seepage membranes as lining layers to prevent contamination of soil and water bodies.
In the construction of roads and reservoirs, it can be used to reinforce foundations or dams. In parks, parking lots, sidewalks and other places, permeable bricks and anti-seepage membranes can be combined to form a “rainfall The virtuous cycle of “runoff-infiltration-reuse or recycling” can also be made into a special mesh structure for use in green roofs and rainwater recycling systems.
Xuyu HDPE one-way geogrid is used in the reinforced soil retaining wall of Chengdu-Kunming Railway
Geosynthetic structures in green roofs
In addition, there are some special Functional geomembrane –
(1) GRAVEL LOCK, a new product of Italian Tenax Company, is a composite geomembrane, consisting of a pointed HDPE geogrid and PP non-woven fabric (gram weight 200 g/m2) is thermally welded, which is not only easy to lay, but also reduces the amount of gravel filling required by 2/3 compared with traditional geogrids, which can speed up the construction period and reduce project costs.
(2) Evoqua’s geomembrane can automatically capture the smelly hydrogen sulfide, and then combine it with certain channel design and auxiliary systems to sulfide it. Hydrogen removed. When used in sewage treatment plants, it not only blocks the penetration of internal gases, but also well controls the odor of the treatment plant. It has been applied to large wastewater treatment plants (WWTP) in Western Canada.
(3) Permanent monitoring system for anti-seepage membrane: 2015, from ChinaMany scientific research institutions and companies in China, the United States, Germany, Austria and other countries have jointly completed the research and development of the permanent monitoring system for anti-seepage membranes, and achieved the first on-site verification in my country. In 2018, my country’s first permanent leakage monitoring system successfully passed project acceptance at the phosphogypsum yard in Fuquan City, Guizhou Province. This system can issue real-time alarms for leaks from small holes with a diameter of 1cm.
(Picture source: Shanghai Shengyi)
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