Quite widespread in the strengthening of roads received geosynthetic materials, otherwise it is called: "Reinforcement of roads."
The field of application of geosynthetics is very wide, and the use is effective, Geosynthetic materials in Europe have been used for several decades, making almost a revolution in road, civil and special construction. Economic efficiency and a wide range of applications of geosynthetics, including in areas where they are practically indispensable, allow us to talk about them as very promising materials.
The use of geosynthetics in road construction already has a history, although not very long. Abroad geosynthetics in the form of geotextiles used since the late 60s.
The production of these materials in the world has developed rapidly, and now the world market offers a large number of different types of geotextiles, geogrids, geogrids and geosot, geonitey and geoplit used as thermal insulators. All of them differ in their purpose, the composition of raw materials, production technology, polymer consumption, physical and mechanical characteristics, the width of the web, etc. In particular, geotextiles (nonwoven fabrics of needle-punched or adhesive production method) are made of synthetic fibers: polyester (Dacron), polypropylene, polyamide (nylon); geogrids - from polyester or polypropylene threads of high strength, glass fiber; geoplites - based on polystyrene.
1. The history of the development of the use of geosynthetics in the Russian Federation.
The Russian experience in the application of geosynthetics began in the mid-70s, first by purchasing these materials abroad, in particular, in Hungary and Czechoslovakia, then by intensive scientific research at industrial research institutes and own developments of manufacturing enterprises. Currently, about 380 different types of geosynthetic materials are produced in the world. The use of geosynthetics is provided for in projects of more than 100 thousand various structures annually around the world.
The reasons for this are based on two main factors: economic - the use of geosynthetic materials can significantly reduce investment in the construction, repair and maintenance of roads; ecological - the use of geosynthetics is environmentally friendly (the consumption of natural materials is reduced, the volume of preparatory geotechnical work is reduced, etc.).
Additionally, the use of geosynthetics allows:
-increase the durability of the structures of the subgrade and pavement;
-improve the quality of work;
-reduce the volume of alterations (additional work);
-improve the culture of production.
The relevance of the introduction of innovative technologies in road construction and environmental measures in the CIS today is obvious and undeniable. This is the continental nature of the climate of certain regions with a large temperature difference, and the presence of territories with difficult geological conditions, and the condition of the roads, most of which were built 40-60 years ago and are designed for lower loads and traffic intensity. The problem of increasing the shear resistance and crack resistance, and hence the durability of asphalt concrete pavements, is especially relevant for an ever-increasing traffic intensity and a marked tendency for axial loads to increase on highways and city streets. As part of the road network, the vast majority is capable of passing only relatively light vehicles with an axle load of not more than 6 tf. At the same time, the automotive industry is developing the production of heavy machines with an axle load of up to 10 tf. In the traffic stream, even heavier cars are often found. The traffic flow has also increased, reaching in some sections 45-50 thousand cars per day with an estimated rate of 6 thousand units. As a result, the bearing capacity of road pavements of many highways has been exhausted. Hence the need for frequent repairs.
And, finally, the conditions of a market economy and economic independence compel the builders to count money. For example, the use of glass roving geogrids for reinforcing asphalt concrete makes it possible to reduce the thickness of the latter to 20%.
Geosynthetics (geosynthetics) - a group of synthetic materials that are widely used in road and civil engineering, the use of geosynthetics opens up new possibilities for solving a variety of problems in the design and construction of roads, as well as complex engineering structures.
Geosynthetics are polymeric materials designed to change the natural properties of soils. The change, as a rule, concerns the filtration properties of the soil (usually the filtration coefficient of too loose soil is reduced), or its strength characteristics (for example, the strength of soft soils increases with the help of geogrid reinforcement).
Euroisol’s geosynthetics department offers this definition for these materials: “Geosynthetics is a material in which at least one of the constituents is made of synthetic or natural polymer in the form of a web, tape or three-dimensional structure, which is used in contact with soil and other building materials. "The combination of soil with HS should be considered as the formation of a new composite material that combines the functions of both soil and synthetic material."
Qualitative and chemical-physical characteristics of geosynthetics are due to the properties of the polymers used for their production. So, such qualities as water and frost resistance, corrosion resistance, low weight, high tensile strength - the merit of polymers, At the same time, disadvantages polymers (rapid aging under the influence of UV radiation, a drop in strength at a temperature of + 80 -120 ° C, combustibility) are leveled by the specifics of the use of HS. Materials are used in structures, the vast majority of which are soils or loose rocks that protect polymers from light and temperature influences.
Geotextiles are considered the progenitor of geosynthetics. The same foreign standards were originally created for these materials.
Depending on the field of application in soil structures, geosynthetics as a whole can perform such functions:
-reinforcement, to improve the shear resistance of granular materials;
- Division, to maintain the structural integrity of the granular layers;
-filtration, to pass fluid and retain soil particles;
-drainage, to collect and drain fluid outside the structure;
-control of erosion, while preventing soil erosion under the influence of water or wind;
-protection to prevent damage to the structural layer, for example, insulation around artificial structures in the subgrade when they are backfilled;
-insulation, to prevent the migration of liquids and gases.
Biaxial grill GEO DS
The first biaxial geogrid was produced in the 1980s by extruding a sheet of polyethylene or polypropylene, perforated after being stretched by a regular network of pattern holes. Such extruded and oriented geogrids are called inelastic (rigid) geogrids. Biaxial geogrids are widely used in the construction of roads, airfields, container sites, car parks, etc. on weak and heterogeneous soils.
The basic principle of operation of biaxial geogrids consists in eliminating the interpenetration of structural layers and fixation of the aggregate due to wedging of its particles in the geogrid cells. When filling and compacting the geogrid cells with inert material, the particles of material are fixed in the cells and the effect of "mechanical stabilization" is created. The biaxial geogrid has high rigidity, which allows it to withstand high loads at low deformations.
-increasing the bearing capacity of the base of the fortified area;
- Separation of incoherent layers, protection against the penetration of coarse-grained material into the lower layers;
-decrease in the values of deformations from frost heaving;
-allows not to increase the thickness of the ballast on soft soils;
-decrease in the rate of settlement of the bases;
-increase in the high-speed mode of movement (railway base).
SSNP geogrids - geosynthetics made of impregnated glass fiber meshes. They are used in the construction or repair of hard pavement with asphalt concrete pavement. The use of geogrids in road construction allows solving a number of existing problems.
Geographic meshes SSP - Neftegaz geosynthetics intended for reinforcement, stabilization of soft soils, construction of temporary roads, ensuring local stability of slopes and slopes.
Glass geogrid brand SSNP-34BT manufactured by STEKLONiT OJSC (Ufa) is a grid of two layers of roving fastened together with a sewn thread and impregnated with a binder to increase strength and adhesion to asphalt concrete. Consider the mechanism of interaction of the geogrid of the SSNP brand and the asphalt concrete layer. Asphalt concrete is an ideal material for the installation of non-rigid coatings, since due to the high viscosity of the asphalt binder and the roughness of the aggregate grains it has high resistance to short-term loads.
The tests carried out on samples - beams made of two-layer asphalt concrete (top layer 3 cm thick, lower layer 4.5 cm) reinforced with a road mesh located between the layers of asphalt concrete and control - non-reinforced ones showed that reinforcing asphalt concrete with a SSNP brand slightly increases ultimate force and relative bending strain. However, it was also revealed that for the destruction of samples of asphalt concrete with a road mesh, 2.85 times more energy costs are required, and, therefore, the rate of cracking in asphalt concrete slows down by the same amount. Thus, the SSNP grid increases the elastic properties of asphalt concrete, increases its distribution ability, as a result of which the stresses from the wheels of the car are distributed over a large area, which helps to reduce the stress concentration and, therefore, slows down the process of cracking. In addition, the grid increases the resistance to rupture of the roadway with ice, which is important for regions with harsh climatic conditions.
According to their operational characteristics, the road grids of STEKLONiT OJSC are not inferior to the corresponding foreign materials and can significantly increase the transport and operational performance of coatings, increase turnaround times, and generally release material resources for other types of work and objects. SSNP nets proved their exceptional qualities in a number of projects. Glass grids of JSC "STEKLONiT" were used when laying roads in St. Petersburg, Moscow, Astana, during the reconstruction of airports in Nizhnevartovsk and Khanty-Mansiysk.
Geotextile high strength stabitex
Geotextile Stabitex (geotextile) - refers to the section of geosynthetics is a woven fabric of high strength polyamide yarns. It is used for the construction of embankments of increased steepness from bulk materials for the construction of retaining walls; protection of territories from landslide phenomena; separation of soil layers; strengthening the foundations of railways and roads, stabilization of weak soils. Stabitek high-strength geotextile is an analog of the following materials: geolon (geolon), polyfelt (polyfelt), taipar (typar), cortex (kortex).
Geotextile (Dornite) - a geosynthetic material is a needle-punched or spunbond non-woven fabric made from polyester fibers. The excellent physicomechanical characteristics of geotextiles are dornite, as well as the widespread use of it in various fields, suggest that geotextiles are destructive of the leader among geosynthetics in the range of applications both in construction and in everyday life.
The use of geotextiles
- geotextile is used as a separating layer (filter) between the soil and aggregate (sand, gravel, etc.);
- prevents the penetration of soil particles into drainage systems (drainage of basements, flat roofs);
- during the construction of tunnels, geotextiles protect the insulation coating from damage, form a drainage layer, divert ground and storm water to the drainage;
- geotextile dornite acts as a filter under the coastal fortification;
- high-density geotextiles can be used as a reinforcing layer on slightly bearing soils;
-It is used to strengthen the bottom of the settling tanks of treatment facilities, at the same time acting as a filter, replacing a layer of sand;
-applied as heat and sound insulation;
- when laying pipelines as ballast
One of the promising structures for volumetric soil reinforcement is a geotechnical lattice (geogrid). Geogrid - geosynthetics representing a flexible compact module, consisting of plastic tapes fastened together, forming in spatial position a spatial cellular structure with specified geometric combinations and sizes. Geogrids are resistant to ultraviolet radiation, fresh and salt water, the chemical effects of soil and aggressive environments. And the main material is durable, non-toxic and environmentally friendly. The combination of these factors determines the technological effect of using a geogrid.