GEO – Textile Woven

Product Details & Usage

Abstract

Geo-textile made of coir are ideally suited for low cost applications because coir is available in our country in abundance at very low price compared to other synthetic geo-textile. These geo-textile can be applied in construction of unpaved roads where can be effectively serving the purpose of reinforcement, separation, filtration and drainage.

Introduction

A large variety of detrimental factors affect the service life of road and pavements including environmental factors, sub grade conditions, traffic road loading, utility cuts, road widening and aging. These factors contribute to an equally wide variety of pavement condition and problems, which must be addressed in the maintenance or rehabilitation of the pavements, if not dealt with during initial construction.

 

Problems of pavement distress are often classified into those attributed to structural deficiencies and those resulting in loss of function of roadway. Structural deficiencies arise by the loss of mechanical properties that govern the load carrying capacity of the roadway or by an increase of load for which the roadway was not designed.

Introduction

In either case, structural deficiencies result in the loss of roadway’s ability to carry vehicular load. The loss of functional capacity of the roadway typically involves the development of excessively rough riding surface that result in discomfort to the road user. Functional problems such as pavement surface cracks, rutting potholes and asphalt bleeding etc. if left uncorrected, can lead to the development of structural problem.

Pavement maintenance treatments are often ineffective and short lived due to their inability to both treat the cause of the problems and renew the existing pavement condition. The main cause of distress in pavements is that they are quite permeable

with 30% to 50% precipitation surface water infiltrating through the pavement, softening and weakening the pavement sub grade and base accelerating pavement degradation. Existing pavement distress such as surface cracks, rocking joints, and sub

grade failures cause the rapid reflection of cracking up through the maintenance treatment. Therefore, the preferred strategy for long-term road and pavement performance is to build in safeguards during initial construction. These performance

safeguards include stabilizing the sub grade against moisture proofing capabilities of selected maintenance treatments. Geo synthetics are proved to be the most cost effective tools for safeguards roads and pavement in these ways. The function of geo synthetics in road fall in to the following categories: sub grade separation and stabilisation, base reinforcement, filtration and drainage, overlay stress absorption and overlay reinforcement.

Sub-grade separation and stabilisation

Temporary roads used for hauling and access roads those are subject to low volumes of traffic are often constructed without asphalt or cement concrete surfacing. In these cases, a layer of aggregate is placed on the prepared sub grade of these roads to

improve their load carrying capacity. As an aggregate layer is loaded, the bottom loosens with tension cracks allowing the underlying fines, under pressure, to migrate up into the aggregate by interfering with the hard, stone to stone contact. As fines infiltrate a portion of the structural section, flexure increases, fines migrate future upwards and the section deteriorates until complete structural section failure occurs.

Sub-grade separation and stabilisation

This process can quickly destroy the effectiveness of several inches (millimeters) of aggregate. Contamination of the base course layer leads to the reduction of strength, stiffness and drainage characteristics. Problems are usually encountered when the sub-grade consists of soft clays, silts and organic soils. This type of sub-grade is often unable to adequately support traffic loads must be improved.

Typical Solutions

Excavating and replacing unsuitable material is costly and time consuming. Other method of sub-grade improvement includes deep compaction, chemical stabilization and preloading. 

Geo-Textile as separator

Geo- textiles are proving to be a cost effective alternative to traditional road construction methods. Geotextiles provide a separation layer between the aggregate and the sub-grade soil, to prevent migration of fines and thus indefinitely preserve the original aggregate structural thickness.

 

The function of separation refers to the ability of the geo-textile to provide physical separation of sub-grade and base materials both during construction and during the operating life of the roadway

 

The function is defined by prevention of mixing, where some type of mechanical action causes mixing Mechanical action causing mixing generally arises from physical forces imposed by construction or operating traffic and may cause the aggregate to be pushed down into the soft sub-grade and /or the sub-grade to be squeezed up into the base aggregate. A properly designed

separator allows the base course aggregate to remain clean which preserve its strength and drainage characteristics.

Here the strength and modulus of Geo- textile is important only to ensure survivability of the material during construction and operation of the roadway. In this the geo-textile separator itself is not viewed to contribute structural support to the roadway whereas it ensures that the base course layer in its entirety will contribute and continue to contribute its intended structural

support of vehicular loads. These viewpoints advocate the use comparatively low strength coir geo-textile in sub- grades.

Geo-textile Benefits

The geo-textile usually costs no more than 2 inches to 3 inches
(50mm to 75mm) of compacted, in place aggregate, but can save
several inches (millimeters) of aggregate. The separate function is more dramatic over weak sub-grade soils, but is economically
practical in the long run to use even on more competent sub-
grades.

Geo-textiles are recommended for this separation function because of their low cost, coefficient of friction, elongation and drape to confirm to any surface, effective filtering even after elongation, abrasion and puncture resistance, and their high coefficient of permeability. 

One extra benefit of using a geo-textile for separation is that almost all the aggregate over the geo-textile can be reclaimed and reused. This is particularly economical in temporary uses such as mine haul or logging roads or anywhere aggregate is expensive and equipment is available to reclaim the uncontaminated stone.

Base Reinforcement

Permanent roads carry larger traffic volume and typically have asphalt or Portland cement concrete surfacing over a base layer of aggregate. The combined surface and base layers act together to support and distribute traffic loading to the sub-grade. Problems are usually encountered when the sub-grade consist of soft clay, silts and organic soils. This type of sub-

grade is often water sensitive and, when wet, unable to adequately support traffic loads. If unimproved, the sub-grade will mix with the road base aggregate – degrading the road structure – whenever the sub-grade gets wet. Poor road often result from poor sub-grades.

Typical Solution

As with unpaved roads, a problematic sub-grade is typically excavated and replaced, or it is improved by the addition of cement, lime or excess aggregate, In any case, the traditional solution is often costly and always time consuming.

Geo- textile Solution

The reinforcement mechanisms, provide by all types of nonwoven and woven geo-textiles, are widely recognized. Geo-textiles are used in reinforcement through mechanisms of restraint or confinement, friction membrane effect and local reinforcement.

Products In roads, lateral restraint also called confinement is considered to be the primary function of the geo-textiles. With the addition of an appropriate geo-textile, the soil geo-textile – aggregate (SGA) system gain stiffness.

The stiffened SGA system is better able to provide the following

structural benefits:

Preventing lateral spreading of the base

Increasing confinement and thus stiffness of the base

Improving vertical stress distribution on the sub-grade

Reducing shear stress in the sub-grade

Drainage / Filtration

The drainage / filtration function of a geo-textile can be critical to structural section performance.

Filtration refers to the ability of geo-synthetics to filter fine soil particles from the sub-grade from intruding into the base when water flows from sub-grade into the base. Water flow is most likely produced by the generation of excess pore water pressures in the sub-grade as a result of repetitive traffic. Fines contained in the sub-grade may become suspended in the pore water as a result of shearing action and can be carried into the base in the absence of a proper filter.

 

The key to this application is the geo-synthetic ability to filter fines without blocking. A suitable geo-textile layer keeps the base clean and allows free drainage without clogging, so that the pores do not grow under pressure and retain their strength. With the need to install a geo-textile filter, geo-textiles with the characteristics required to prevent fine migration can be selected.

The suitability of coir as a geo-textile material

As Reinforcement

Reinforcement is one of the most important functions of geo-textiles in improving the soil properties, whether it is used in slope, embankments, and retaining wall or in pavements. When reinforcement is placed in soil it can develop bond through frictional contact between the soil particles and the reinforcement surface. Deformation in the soil mobilizes tensile

or compressive force in the reinforcement depending on the inclination of the later and is ultimately limited by the available bond between soil and reinforcement. Hence the shear frictional behavior of soil geo-textile interfaces.

As separator

The separator aspects of coir geo-textile have been studied by

performing plate load model tests within a test tank. The tests were conducted by applying static loads on base course through a plate of 200mm diameter. The test was repeated by placing geo-textile at the interface between soil and base course. The test was conducted with woven and non woven coir geo-textile.

Here also placement of a single layer of geo-textile improves the

supporting power of the sub-grade more than two times. Here in

addition to the function of reinforcement, the geo-textile performance as separator also and thereby prevent the mixing of sub grade and the coarse material for the base. These factors increase the carrying capital also.

As a filter / drainage layer

One of the main functions performed by geo-textiles is filtration. Here the water flows through the geotextile. Permeability tests can be performed to estimate the amount of water per unit area passing through the geo-textile. Here, in the case of coir geo-textiles, this property applies only to non-woven mesh with very high permeability. The cross-sectional permeability of the non-bonded geo-textiles tested is approximately 0.025cm / s. Much more than the average five type.

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