Geotextiles
What is geotextiles?
Geotextiles are water-permeable geosynthetics, which are made of polymer fibers as raw materials through hot pressing, acupuncture, cementation and weaving. Geotextiles are mainly divided into two types: woven geotextiles and non-woven geotextiles.
In engineering applications, geotextiles can be used alone or in combination with other geosynthetics such as geogrids, geomembranes, and geonets.
What is geotextiles made of？
The raw materials of geotextiles are mainly synthetic fibers currently.
The selection of various synthetic fibers needs to be combined with the actual situation of the project. It is necessary to consider not only the requirements of its physical and chemical properties in the field of use but also the cost of the product. Among them, polyester fiber and polypropylene fiber are the most commonly used, followed by polyamide. fibers and polyvinyl acetal fibers.
Polyester fiber has good physical and mechanical properties, excellent toughness and creep characteristics, high melting point, high-temperature resistance, aging resistance, mature production technology, and high market share. The disadvantages are poor hydrophobicity, easy accumulation of condensed water when used in thermal insulation materials, poor performance at low temperatures, easy vitrification, reduced strength, and poor resistance to acids and alkalis.
Polypropylene fiber has good elasticity and instantaneous elastic recovery better than polyester fiber; excellent acid and alkali resistance, abrasion resistance, mildew resistance, low-temperature resistance; good hydrophobicity and wicking performance, which can make moisture along the fiber axis It is transmitted to the surface of the outer layer; the density is low, only 66% of that of polyester fiber. After repeated drafting, fine denier fibers with compact structure and superior performance can be obtained, and combined with the reinforcement process, the strength can be more superior. The disadvantage is that it is not resistant to high temperature, the softening point is 130 ~ 160 ℃, the light resistance is poor, and it is easy to age and decompose in sunlight, but it can be made to have anti-ultraviolet performance by adding additives such as ultraviolet absorbers.
In addition to the above fibers, the raw materials of non-woven geotextiles can also use jute fibers, polyethylene fibers, polylactic acid (PLA) fibers, etc. Natural fibers and special fibers have gradually entered various application fields of geotextiles, such as natural fibers (jute, coconut husk fiber, bamboo pulp fiber, etc.)
Performance of Geotextiles
Woven geotextiles appeared in the 1960s, which are characterized by high strength, high cost, poor filtration and drainage functions, and have limitations in engineering applications.
Non-woven geotextiles began in the late 1960s. High-performance raw materials endow products with high strength and durability, and advanced production technology endows products with good functions, expanding their application range.
Especially in the past 30 years, with the promotion of needle-punched non-woven and spun-bonded non-woven processes, the application field of non-woven geotextiles is more extensive than that of woven geotextiles and has developed rapidly.
Functions of Geotextiles
Filtration
Since the geotextile has good water permeability and air permeability, placing it in the soil structure can allow the liquid inside the soil to pass through and discharge, and at the same time play a role in soil preservation, which can effectively prevent the upstream soil particles, fine sand and small stones. loss, prevent soil damage, and maintain the safety and stability of the project.
Drainage
As a good water-conducting material, the geotextile itself acts as a drainage channel, which can collect the moisture inside the soil structure in the geotextile and slowly drain the soil along the material.
Anti-seepage effect
The composite geotextile and geomembrane have low water (gas) permeability, which can prevent the flow and diffusion of liquid or gas, and play an anti-seepage or containment role.
Reinforcing effect
The geotextile is arranged inside the soil body as a reinforced material, or the geotextile is combined with the soil to form a composite body. Compared with the unreinforced soil body, the strength and deformation properties of the reinforced composite soil body are significantly improved.
Reinforcing effect
The geotextile is arranged inside the soil body as a reinforced material, or the geotextile is combined with the soil to form a composite body. Compared with the unreinforced soil body, the strength and deformation properties of the reinforced composite soil body are significantly improved.
Isolation
Isolation means that the geotextile can isolate two materials with different properties, so as not to mix with each other and lose the integrity and structural integrity of various materials.
For example, the geotextile laid between the ordinary railway ballast and the subgrade can effectively isolate the gravel ballast and the soil subgrade.
Protective effect
Soil loss caused by rainfall shock and surface water runoff can be reduced by setting up geotextile protection measures.
If the geotextile and geonet are compounded and laid on the surface of the exposed soil of the slope, the erosion of precipitation and surface runoff can be effectively avoided or reduced;
Sediment fences made of geotextiles can filter out suspended soil particles in turbid runoff.