By Jingkui Chi
Editor’s note: Part 2 of this 2-part series ran in the October/November issue of Geosynthetics. Following the Abstract, Part 2 concludes with sections 3 and 4 of this manuscript.
This article presents an introduction to the development of China’s geosynthetics production, applications, testing, and research, and discusses the market supply and demand as well as development trends.
1.1 Development of geosynthetics in China
The production and application of geosynthetics in China started in the late 1970s. Those materials used in some small hydraulic engineering projects were mostly made through braiding techniques with narrow widths.
Development was slow through the 1980s. Geosynthetics then were mainly woven fabrics with poor quality and few were considered for engineering applications. By the 1990s, under the development and requirement of national economic construction, geosynthetics witnessed a burgeoning growth. Some advanced equipment and assemblies were imported from Germany, Italy, France, Japan, and Switzerland.
Meanwhile, homemade equipment appeared in the market, which increased product variety, improved product quality, and changed product structure. Braided, woven, nonwoven, synthetic, and composite products appeared and were used in thousands of projects, with an accumulated usage of more than 0.5 billion m2.
China suffered severe flooding disasters in 1998, but the adoption of geosynthetics in flood control, dam repair, and other hydraulic engineering projects moved forward.
In 1999, the Ministry of Water Resources selected 50 hydraulic projects using geosynthetics as models, thus further pushing forward the application and development of geosynthetics in China. Moreover, with the improvement and modification of geosynthetic equipment, designs, processes, measurement, regulations, and theoretical research, China’s geosynthetic materials entered a new era in the past decade.
A “geo-textile collaboration network” had been established in 1984 and grew into the Chinese Technical Association/Geosynthetics by 1995. As a first-class national academic organization, this group attracted more than 600 members. After entering the International Geosynthetics Society in 1990, China established its Chinese Chapter (CCIGS) with more than 100 individual members and four group members. CCIGS has organized and participated in international and regional symposiums and exhibitions in the United States, Austria, France, Singapore, South Korea, Japan, and other countries. This participation worldwide enhanced the academic communication and market education between China and the rest of the world.
1.2 Classification of geosynthetics
Currently, there are no unified classification rules and there is no significant difference in the existing classification methods. According to manufacturing methods, geosynthetics can be classified into four categories:
Wovens: braided (plane-braided and round-braided methods), woven (plain and twill woven), knitted (warp knitted and stitch-bonded).
Nonwovens: mechanical reinforcement (needlepunched), chemical bonded (adhesive spraying), thermal bonded (hot rolling).
Geomembranes (calendering, blow molding)
Polyethylene (PE), polyvinyl chloride (PVC), chlorosulfonated polyethylene (CSPE).
Composite geomembranes, composite geotextiles, plastic drainage belts and drainage pipe, prefabricated drainage.
Geotextile bags, geogrids, geocells, geotechnical bands and tubes, geonets, geosynthetic clay liners (GCLs), extruded polystyrene (EPS), drainage and waterproofing.
1.3 Application of geosynthetic
Woven textile products
Braiding and knitting products are widely used in engineering products. In China, braided products have occupied a large proportion, especially in the application of flood control and rush emergency. The use of large sandbags in the construction of embankments, dams, and marine reclamation land is also considerable.
Woven products are used in mattresses as bottom protection, slope protection, geomembrane bags, and other projects that require a relatively high intensity. As newly developed products, knitting products (mainly made of PET filaments and glass fibers) are of good quality that can be used for reinforcement.
The application of braiding products is mainly in the area of hydraulic engineering projects, such as the Shanghai Chen-Hang Reservoir (above, right), deep-water channel regulation projects in Changjiang Estuary, the Shanghai Pudong international airport project, the Shanghai Waigaoqiao power plant, the Shidongkou ash dam, Tianjin harbor construction, as well as for marine reclamation land and uses for flood control and flood prevention.
In China, needlepunched PET staple fiber products are common, with dozens of large-scale manufacturers. Yet there are more than 10 spunbond PET filament manufacturers, some with imported equipment, others using domestic equipment. Therefore, Chinese nonwoven products are mainly of needlepunched staple fibers, with a width of 4m–6m and mass of 300g/m2 to 400g/m2. The applications for nonwovens grows every year, especially in hydraulic engineering, but also in highway, railway, environmental protection, airport, coastline, and other engineering projects.
Application of synthetic products
In China, the manufacturing of synthetic products started relatively late. Until the 1980s, Britain-imported Netlon equipment was used to produce geogrids.
At that time, geomembranes were only used in agriculture greenhouse films and had few applications in engineering products. In the late 1990s, the development of products such as geogrids and geomembranes had been promoted to meet the demand of engineering construction. Today, with a significant improvement in quality and variety, geogrids are manufactured both uniaxial and biaxial.
For geomembranes, the diameter and thickness of blow molding types has increased, and plastic extrusion and calendering products have been launched. Other synthetic products such as geocells and three-dimensional vegetative netting have also been developed.
The major applications for these synthetic products includes seepage-control materials used in hydraulic engineering and environmental protection, reinforcement of soft slab foundations and retaining walls, and three-dimensional netting for seeding slope stabilization.
Major projects include anti-seepage for the hydro-junction retaining dike in Wangfuzhou, Han River (1.1 million m2 of geomembrane); Shenzhen River harnessing project (216,000m2 of geomembrane); dam reinforcement in the Three Gorges project with a geogrid usage of 530,000m2; geocell reinforcement from Lanzhou Airport to Yinjiazhuang Road (58,000m2). Further, geomembranes are widely used in the landfills of large cities such as Beijing, Shanghai, Tianjin, and Hangzhou. In short, synthetic products have an extensive application range and a large development potential in China.
Application of composite products
Composite products are processed by combining two or more geosynthetic products.
Familiar products include composite geomembranes (one textile with one membrane, two textiles with one membrane, and three textiles with two membranes) used in anti-seepage projects, and in drainage belts used in reinforcement applications. When combined with vacuum pressure to accelerate foundation consolidation, construction time is shortened.
Drainage hoses, which have been widely applied in environmental engineering and municipal construction, are also common in hydraulic projects to solve the problems of interior drainage. GCLs are primarily used as anti-seepage materials in waste-disposal parks. Composite geomembranes are widely used in hydraulic engineering, such as the anti-seepage and bank protection projects on the Yangtze River.
After some years of stagnation, the Chinese geosynthetics industry has recently gained impressive improvements. Development direction of products turns to series type, synthetic type, and composite type. Geosynthetic materials enjoy a promising future, with their contributions in geotechnical engineering growing into a new era.
2. Application prospects of geosynthetics in key construction projects
2.1 Hydropower construction
According to China’s 11th five-year plan (2006–2010), the investment in hydraulic engineering could reach 400 billion yuan ($58.6 billion U.S.).
The basic principle is to vigorously develop hydropower, optimize thermal power, appropriately develop nuclear power plants, and actively develop new energy sources. Hydropower is regarded as a top priority. The Jinsha River, Yalong River, and Upper Yellow River hydropower bases, as well as the Puluo Ferry and Xiangjia Dam hydropower stations, are scheduled for construction. If necessary, pumped storage power stations will also be built.
As the largest hydraulic project in the world, China’s south-to-north water diversion project has an investment of 535.1 billion yuan ($78.4 billion U.S.), in which 63.4 billion yuan ($9.3 billion U.S.) is designated for the eastern line, 167.7 billion yuan ($24.6 billion U.S.) for the midline and 304 billion yuan ($44.5 billion U.S.) for the western line.
For the eastern line project, the length of the main water conveyance trunk is 1,156km (717mi). At the bottom of the Yellow River, there are two circular tunnels with inside diameters of 9.3m (10.2yd), and the whole length of the tunnel reaches 634m (694yd).
The pollution control project of the eastern line has been divided into two phases. The first phase of the project was recently completed, with the second phase under construction from 2009–2013. By that time, the number of sewage treatment plants could total 135.
For the midline project, the length of main water conveyance trunk is 1,267km (786mi). Two circular tunnels 7.2km (4.5mi) long with an inside diameter of 8.5m (7.8yd) have 20m (18.3yd) between the two circle centers.
For the western line project, the length of main water conveyance trunk reaches 289km (179mi), with much of this trunk in tunnels. Three import water projects are involved: the Yalong River line, with a length of 131km (81mi); the Tongtian River line, with a length of 289km (179mi); and the Dadu River line, with a length of 30km (18.6mi), all of which are tunnels. This project is scheduled to start in 2010.
Pumping stations use electric power to pump water from downstream to upstream as storage for the peak periods of electricity consumption. Since the loss of pumped water and anti-seepage concrete previously used needed frequent repair, the results were relatively poor. Currently, 2mm geomembranes are used to prevent seepage.
In the construction of some hydraulic projects, cofferdams are builtfor water closure.
In the past, cofferdam core walls were made of clay. However, some locations have few clay resources and the selection and processing method of clay core walls needs to be strict, which inevitably stalled construction timelines. Therefore, geomembranes have been used as substitutes. With the use of geomembranes in the Three Gorges cofferdam, the Fujian Shuikou power station cofferdam, and in other hydropower stations in China, demand for geomembranes has increased.
China has a large number of conveyance channels, but there are various problems such as weather aging and poor anti-seepage treatments (e.g., 50% of the transported water lost en route). Recently, geomembranes have been used as anti-seepage materials to solve these issues.
In conclusion, Chinese investment in hydropower construction ranks first in the world. Besides major hydropower projects programmed by the central government, local governments also are investing large sums of money in hydropower construction. Hydropower projects remain the biggest market for geosynthetic products, from small, rural plants and reservoirs to large, world-class hydraulic and hydropower projects.
2.2 Applications in environmental engineering
According to the 11th five-year plan, China will direct 1,300 billion yuan ($190 billion U.S.) into environmental engineering projects.
Along with the rapid development of urban construction, serious problems have been caused by the lack of environmental protection infrastructures. For instance, garbage has been stacked in open areas or simply buried, while sewage was often discharged directly into urban water systems, causing water quality deterioration and contamination of rivers, lakes, and groundwater. Not solving this problem as soon as possible threatens our living environment.
Geosynthetics have a long history in environmental construction, especially for landfill projects where an anti-seepage structure has been formed with a variety of geosynthetic products.
Currently, China has more than 800 cities with an urban population totaling 450 million, and the number of landfills has exceeded 800. With the fast progress of urbanization, by 2010 there will be 1,200 cities with an urban population totaling 630 million. By that time, every city should have a landfill, which indicates that the use of geosynthetics would be considerable. The 2010 Expo–Shanghai (May 1–Oct. 31, 2010) should further boost investments in environmental protection.
The largest waste and anaerobic treatment plant has been built in Shanghai with a total investment of 300 million yuan ($44 billion U.S.). Covering an area of 66mu (10.9 acres), the plant has an annual garbage treatment capacity of 280,000 tonnes (308,560 tons) and a daily capacity of 800 tonnes (882 tons), including 680 tonnes (750 tons) of domestic waste and 120 tonnes (132 tons) of organic waste. Furthermore, through the process of anaerobic fermentation, 4.1 million degrees of electricity could be provided to the east China power grid. The plant was built in 2007 and started trial operation in April 2008. Formal operation began in 2009.
The application of geosynthetics in environmental engineering is comparatively strict and complicated. Poisonous solids, liquids, and gases must be regulated. The durability of geosynthetics must be considered, including salinization control, anti-corrosion, anti-microorganism, anti-aging, and other special properties.
In environmental engineering in China, the geosynthetic products are primarily geomembranes, geogrids, geotextiles, and some GCLs and drainage pipes. For big projects, HDPE geomembranes with a width of more than 4m (4.4yd)and thickness from 2–4mm are generally used. For smaller projects, materials could be designed under the requirement of specific conditions, yet thickness is usually less than 0.5mm. One-sided or double-sided composite geomembranes are used to protect membranes from damage during the construction process.
2.3 Applications in railway construction
Under the 11th five-year plan, total investment in railway construction will reach 1,250 billion yuan ($182.8 billion U.S.), with 17,000km (10,540mi) of new railway lines constructed, including 7,000km (4,340mi) of passenger transportation lines. By 2010, national railway transportation operations will total 90,000km (55,800mi).
The main functions of geosynthetics in railway engineering includes anti-filtration, anti-seepage, drainage, protection, and reinforcement. In early stages, needlepunched staple fiber nonwovens were used as filtration for subgrades to solve the frost boiling and mud pumping problems. As techniques and products improved, there has been an increasing amount of geosynthetics in railway projects, which have effectively conquered many technical problems in railway subgrades.
Besides the application of filtration and drainage for soft subgrades, drainage belts can be inserted as reinforcement, geogrids can be used for reinforcement of subgrades and embankments, and vegetative nets can be used for grass seeding and slope protection. Geomembranes and composite geomembranes are used for anti-seepage applications on embankments, retaining walls, and tunnels. Composite geomembranes not only control seepage, but also drain water through the composited nonwovens on the membranes.
Currently, railway construction is mainly occurring in the northwest and southwest areas of China, where applications of anti-seepage materials are used. For this application, geomembranes help produce favorable results. And since it is required that grass be planted on both sides of railway embankments, the application of three-dimensional vegetative nets have also expanded in recent years.
2.4 Applications in road construction
China has invested 1 billion yuan ($146 million U.S.) in the comprehensive reconstruction of Qinghai-Tibet Highway, and ll provinces and most cities have also invested large sums of money in highway construction. Both the scale of highway construction and the amount invested are unprecedented.
The applications of geosynthetics in highway engineering is wide. Some applications are similar to railway engineering, but there are also some differences. Generally, geotextiles fit into highway construction for reversed filtration layers, drainage, and to solve the problems of mud and soil pumping and the reflection cracking of asphalt pavements.
Geogrids and geocells are often used in reinforced subgrades and reinforced retaining walls. Geomembranes and composite geomembranes are mainly used in seepage prevention in tunnels and retaining walls. Bridges, culverts, and retaining walls are the main highway structures and proper geosynthetics selection are required for specific projects.
2.5 Applications at seaports and airports
Port construction includes wharves, port roads, container yards, revetment engineering, and some comprehensive engineering construction such as breakwaters.
If a project is located on soft coastal foundations, reinforcement using geosynthetic products is needed. Geotextiles are used for filtration layers, geotextile bags for slope protection, and geogrids for foundation reinforcement, while a geotextile sucking sand pipe bag is used to reclaim land from the sea. A drainage belt is used to drain water and reinforce foundations, and geomembranes are used as anti-seepage material in buildings and for vacuum preloading sealing material. In short, geosynthetics are absolutely necessary for everything from reclamation of land from the sea to actual port construction.
Airport construction mainly includes aprons, runways, taxiways, buildings in airport terminal areas, and ancillary buildings. Most of the airports in southeast China are built on the coast. Some runways can be built only after reclaiming land from the sea. Therefore, airports can involve comprehensive construction requiring the use of many geosynthetic products.
2.6 Applications in mine construction
Mine construction requires the building of tailings reservoirs, used to pile waste excreted sand aggregate.
It is necessary to solve any anti-filtration and anti-seepage problems to guarantee the security and the stability of the tailings dam. For this reason, the selection of geotextiles—instead of sand and stone—as the filtration layer and the use of geomembranes and composite geomembranes for the anti-seepage material is preferred.
Currently, of the thousands of mines in China, it is estimated that more than 30% use some kind of geosynthetic material.
2.7 Applications in urban construction
Urban construction focuses on traffic and housing construction.
Of course, these projects need to address anti-seepage, especially on the southeast China coast. There the water level is high and the rainy season is long, so the seepage problem becomes even more crucial.
Geomembranes are used to solve the anti-seepage problems for subway tunnels, underground stations, basements, and underground garages.
It is also a good option to use geo-membrane in city roof greening and tri-dimensional forestation.
2.8 Application in western development construction
China currently has a strategic decision to make concerning western development.
It is not only an opportunity for the western part of the country, but also an opportunity for further development of the eastern part. Strengthening the cooperation between the two parts of the country is bound to push common development forward.
The total area of the western region of China is about 6,850,000km2 (2,644,785mi2), making up 71.4% of the total land area of China, including 12 provinces, municipalities, and autonomous regions such as Shaanxi, Gansu, Qinghai, Ningxia, Xinjiang, Sichuan, Chongqing, Yunnan, Guizhou, Tibet, Guangxi, and Inner Mongolia. Every area has its own development advantages and development emphasis areas.
The emphasis of the current infrastructure construction is on water conservancy, railways, highways, airports, and urban construction, as well as preserving the ecological environment. All of these require the use of new materials, new processes, and new technologies to ensure the engineering construction quality, increase the construction pace, and reduce project costs.
Currently, China is in the midst of western development and the implementation of infrastructure construction, with geosynthetics and its application technology the effective and necessary geotechnical engineering material. Geosynthetic materials have been used in tens of thousands of large and small engineering projects in China for many years. They can fully display their excellent characteristics in many applications, such as flood control and emergency, water-saving irrigation by catchment, and environmental protection. This geotechnical engineering material and its application technologies will play a greater role in the western development.
2.9 Major projects
Current projects include: South-to-North Water Diversion Project, West-East Gas Transmission, West-to-East Electricity Transmission, and Qinghai-Tibet Railway—four major projects in the 11th five-year plan, all focusing on western development.
China has published the “Implementation Opinion of Policies and Measures about Western Development” to guarantee it in policy and law.
Water is the lifeline of economic and social development of China’s western region. There is no shortage of electricity and gas, but the lack of water directly affects people’s lives, industrial and agricultural production, as well as the need for drinking water for people and animals.
There are solutions to the water problem. One is water diversion and conveyance. Another is water catchment and storage. Third is water conservation.
It is of utmost importance to solve seepage problems in all construction to ensure that there is no water loss. Using geomembranes is the most economic and effective way, and this has been proven by innumerable construction projects.
Currently, the development of water conservancy construction in western China focuses on water-saving projects in irrigation districts, water-storage projects in the field, drought resistance and water conservation projects, supplementary irrigation, and water supplement projects. All of these projects have to solve the problem of anti-seepage, so the western development needs plenty of geosynthetic materials, especially geomembranes. There is a great market potential here. Other kinds of products should be developed according to the characteristics of the western region, as well.