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1、2023/2/23,1,Geosynthetics Types Functions and Applications,土工合成材料：种类、功能与应用,徐 超,2023/2/23,2,What are geosynthetics?,Geosynthetics,Permeable,Impermeable,Geotextiles,Geomembranes,Synthetic polymer materials that are specifically manufactured to be used in geotechnical and geo-environmental applications
2、,What are geosynthetics?,2023/2/23,3,Geosynthetics Types,Geotextiles(woven,nonwoven)Geogrids Geocells Geodrains Geofoam Geomats Geonets Fibres Geomembranes Geocomposites,2023/2/23,4,Geosynthetic types,2023/2/23,5,Roles/functions of Geosynthetics,Separator,Reinforcement,Drainage,Filter,Energy absorbe
3、r,Container,Barrier,2023/2/23,6,Overview of Functions,Geosynthetics applications can be classified according to primary functionsHowever,it is important to note that geosynthetics may also perform one or more secondary functions,2023/2/23,7,Function vs.Geosynthetic Type,应该加一个“防护”功能，erosion control,2
4、023/2/23,8,Geosynthetics TypesGeotextiles,Nonwoven,Woven,Geotextiles are continuous sheets of woven,nonwoven,knitted or stitch-bonded fibres or yarns.The sheets are flexible and permeable and generally have the appearance of a fabric.Geotextiles are used for separation,filtration,drainage,reinforcem
5、ent and erosion control applications.,2023/2/23,9,Separation-Filtration-Drainage-Protection-Reinforcement,Wovens,Nonwoven,2023/2/23,10,Geotextiles for seperation,2023/2/23,11,Geosynthetics TypesGeogrids,2023/2/23,12,Geosynthetics TypesFibres,Definition:Pieces of fibres or continuous fibres or filame
6、nts mixed to the soil for reinforcement,2023/2/23,13,Geosynthetics TypesGeonets,Geonets are open grid-like materials formed by two sets of coarse,parallel,extruded polymeric strands intersecting at a constant acute angle.The network forms a sheet with in-plane porosity that is used to carry relative
7、ly large fluid or gas flows.,FOTO*,2023/2/23,14,Geocomposites are geosynthetics made from a combination of two or more geosynthetic types.Examples include:geotextile-geonet;geotextile-geogrid;geonet-geomembrane;or a geosynthetic clay liner(GCL).Prefabricated geocomposite drains or prefabricated vert
8、ical drains(PVDs)are formed by a plastic drainage core surrounded by a geotextile filter.,Geosynthetics TypesGeocomposites,2023/2/23,15,Geosynthetics TypesGeocomposites for Drainage,2023/2/23,16,Geosynthetics TypesGeocomposite:Geodrains,Definition:Drainage materials consisting of a plastic core enve
9、lopedby a non woven(resin bonded)geotextile.,2023/2/23,17,Geosynthetic TypesGeocells,Geocells are relatively thick,three-dimensional networks constructed from strips of polymeric sheet.The strips are joined together to form interconnected cells that are infilled with soil and sometimes concrete.In s
10、ome cases 0.5 m-to 1 m-wide strips of polyolefin geogrids have been linked together with vertical polymeric rods used to form deep geocell layers called geomattresses.,2023/2/23,18,Geosynthetics TypesGeomats,Definition:Three dimensional,permeable,polymeric(synthetic or natural)structure,used for soi
11、l protection and to bind roots and small plants for erosion control applications.,2023/2/23,19,Geosynthetics TypesGeofoam/EPS or XPS,Typical Density:12 kg/m3 to 30 kg/m3,Geofoam blocks or slabs are created by expansion of polystyrene foam to form a low-density network of closed,gas-filled cells.Geof
12、oam is used for thermal insulation,as a lightweight fill or as a compressible vertical layer to reduce earth pressures against rigid walls.,2023/2/23,20,Geosynthetics TypesGeomembranes,Geomembranes are continuous flexible sheets manufactured from one or more synthetic materials.They are relatively i
13、mpermeable and are used as liners for fluid or gas containment and as vapour barriers.,2023/2/23,21,Geosynthetics TypesGeomembranes,rough surface,smooth surface,2023/2/23,22,Geosynthetics TypesGeosynthetic Clay Liners-GCL,Geosynthetic clay liners(GCLs)are geocomposites that are prefabricated with a
14、bentonite clay layer typically incorporated between a top and bottom geotextile layer or bonded to a geomembrane or single layer of geotextile.Geotextile-encased GCLs are often stitched or needle-punched through the bentonite core to increase internal shear resistance.When hydrated they are effectiv
15、e as a barrier for liquid or gas and are commonly used in landfill liner applications.,2023/2/23,23,Types of Geosynthetic Clay Liners,(a)Stitch bonded bentonite between upper and lower GTX,Bentonite+Adhesive,Geosynthetics TypesGeosynthetic Clay Liners-GCL,2023/2/23,24,Geosynthetics TypesGeosynthetic
16、 Clay Liners-GCL,Bentonite:Hydraulic conductivity 10-11 m/sGCL combination of geosynthetics and bentonite,Bentonite expansion after hydration,2023/2/23,25,Geosynthetics Applications,Barrier Drainage Filtration Protection Reinforcement Separation Surficial erosion control Multiple functions,2023/2/23
17、,26,Fluid/Gas(barrier)containment:The geosynthetic acts as a relatively impermeable barrier to fluids or gases.For example,geomembranes,thin film geotextile composites,geosynthetic clay liners(GCLs)and field-coated geotextiles are used as fluid barriers to impede flow of liquid or gas.This function
18、is also used in asphalt pavement overlays,encapsulation of swelling soils and waste containment.,Geosynthetics ApplicationsBarriers for Fluids and Gases,The use of a geosynthetic material to prevent the migration of liquids or gases.,2023/2/23,27,Geosynthetics ApplicationsBarriers for Fluids and Gas
19、es,2023/2/23,28,Geosynthetics ApplicationsBarriers for Fluids and Gases,2023/2/23,29,Geosynthetics ApplicationsDrainage and Filtration,Filtration:The geosynthetic acts similar to a sand filter by allowing water to move through the soil while retaining all upstream soil particles.For example,geotexti
20、les are used to prevent soils from migrating into drainage aggregate or pipes while maintaining flow through the system.Geotextiles are also used below rip rap and other armour materials in coastal and river bank protection systems to prevent soil erosion.,Drainage:The geosynthetic acts as a drain t
21、o carry fluid flows through less permeable soils.For example,geotextiles are used to dissipate pore water pressures at the base of roadway embankments.For higher flows,geocomposite drains have been developed.These materials have been used as pavement edge drains,slope interceptor drains,and abutment
22、 and retaining wall drains.Prefabricated vertical drains(PVDs)have been used to accelerate consolidation of soft cohesive foundation soils below embankments and preload fills.,2023/2/23,30,Geosynthetics ApplicationsDrainage and Filtration,Substituting or in combination with natural draining material
23、s,2023/2/23,31,Geosynthetics ApplicationsDrainage and Filtration,Geocomposite behind a retaining wall(Photo:Courtesy J.P.Gourc),2023/2/23,32,Geosynthetics ApplicationsDrainage and Filtration,2023/2/23,33,Geosynthetics ApplicationsProtection,Protection:The geosynthetic material is used as a localised
24、 stress reduction layer to prevent or reduce damage to a given surface or layer.,nonwoven geotextile,geomembrane,2023/2/23,34,Reinforcement:The geosynthetic acts as a reinforcement element within a soil mass or in combination with the soil to produce a composite that has improved strength and deform
25、ation properties over the unreinforced soil.For example,geotextiles and geogrids are used to add tensile strength to a soil mass in order to create vertical or near-vertical changes in grade(reinforced soil walls).Reinforcement enables embankments to be constructed over very soft foundations and to
26、build embankment side slopes at steeper angles than would be possible with unreinforced soil.Geosynthetics(usually geogrids)have also been used to bridge over voids that may develop below load bearing granular layers(roads and railways)or below cover systems in landfill applications.,Geosynthetics A
27、pplicationsReinforcement,2023/2/23,35,Geosynthetics FunctionsReinforcement,Reinforced mass:stronger and stiffer,2023/2/23,36,Geosynthetics ApplicationsReinforcement,Reinforced Walls and Steep Slopes,2023/2/23,37,Geosynthetics ApplicationsReinforcement,Fibre Reinforced Soil,2023/2/23,38,Geosynthetics
28、 ApplicationsReinforcement,Embankments on Soft Soils,2023/2/23,39,Geosynthetics FunctionsReinforcement,2023/2/23,40,Geosynthetics ApplicationsEmbankment Stabilisation,桩承加筋路堤/桩-网路堤：basal reinforced piled embankment,2023/2/23,41,Geosynthetics ApplicationsReinforcement,Reinforced pavements/caps,2023/2/
29、23,42,Geosynthetics ApplicationsReinforcement,Reinforced walls,加筋土挡墙Reinforced steep slopes,加筋土陡坡Reinforced embankment over soft soils,软基上的加筋路堤Basal reinforced piled embankment,桩承加筋路堤Reinforced foundations,加筋地基Other applications in landfill,railroad,hydraulic projects,2023/2/23,43,Geosynthetics Appl
30、icationsMultiple Functions,Pavements:Reflective cracking prevention Prevention of pumping of fines,防治路面反射裂缝和喷砂冒泥,2023/2/23,44,Geosynthetics ApplicationsMultiple Functions,Geogrid application in overlays,2023/2/23,45,Geotextile application in overlays,Rezende(2002),Geosynthetics ApplicationsMultiple
31、Functions,2023/2/23,46,Without geotextile,Geosynthetics ApplicationsMultiple Functions,With geotextile(some cracksbut no pumping of fines,2023/2/23,47,Geosynthetics ApplicationsSeparation,Separation:The geosynthetic acts to separate two layers of soil that have different particle size distributions.
32、For example,geotextiles are used to prevent road base materials from penetrating into soft underlying soft subgrade soils,thus maintaining design thickness and roadway integrity.Separators also help to prevent fine-grained subgrade soils from being pumped into permeable granular road bases.,Without
33、geotextile,With geotextile,2023/2/23,48,Erosion control:Geosynthetics can minimise soil erosion caused by rainfall impact and surface water runoff.For example,temporary geosynthetic blankets and permanent lightweight geosynthetic mats can be placed over exposed slope surfaces.Geotextile silt fences
34、can be used to remove suspended particles from sediment-laden runoff water.Some erosion control mats are manufactured using biodegradable wood fibres.,Geosynthetics ApplicationsErosion Control,2023/2/23,49,Geosynthetics ApplicationsErosion Control,2023/2/23,50,Geosynthetics Other Applications,Geotex
35、tile Tubes:used for containment,erosion control,water andflood control,etc.,土工管，用于滩涂治理。,2023/2/23,51,Geosynthetics Other Applications,Protection Against Falling Stones and Avalanches,2023/2/23,52,Geosynthetics Other Applications,Noise Reduction Barrier,2023/2/23,53,Geosynthetics Emerging Application
36、s,geotextile,sand or gravel,Alexiew et al.(2004),Trunk et al.(2004)Eurogeo04,geogrid,Gniel&Bouazza(2008)Eurogeo08,2023/2/23,54,Conclusions,No standard solutions.Each application asks for individual design.There is no one size to fit them all,2023/2/23,55,questions,List at least 6 types of geosyntheticsPresent more than four geosynthetics functons,and give one application to explane the role which geosynthetic plays.,2023/2/23,56,Next lecture,The new advancement in geosynthetic reinforced soil walls/slopes(GRSW).土工合成材料加筋土挡墙/边坡新进展。,
