Library of Congress Cataloging-in-Publication Data Koerner, Robert M., Designing with geosynthetics / Robert M. Koernerth ed. wm-greece.info Includes. Designing with. Geosynthetics. Second Edition. Robert M. Koerner, Ph. D., P. E.. Bowman Professor of Civil Engineering. Director. Geosynthetic Research. Read "Designing with Geosynthetics - 6Th Edition Vol. 1" by Robert M. Koerner available from Rakuten Kobo. Sign up today and get $5 off your first download.
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Designing with geosynthetics by Robert M. Koerner, April 14, , Prentice Hall edition, Hardcover in English - 5 edition. 1 Geosynthetic Institute, Folsom, PA (e-mail: but also for many new engineering applications and specific designs that were . Koerner (). Designing with Geosynthetics - 6th Edition Vol. 1. By Robert M. Koerner through four individual chapters on geosynthetics, geotextiles, geogrids and geonets.
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Russell Gettis. Design of Cold-formed Steel Structures. Associacao Portuguesa de. Coloring Technology for Plastics. Ronald M. Coatings for Plastics. Guido Wilke. Long-term geotextile degradation mechanisms and exposed lifetime predictions Part III Primary functions of geotextiles Geotextiles used in separation Geotextiles used in filtration Geotextiles used in drainage Geotextiles used in reinforcing paved and unpaved roads and railroads Geotextiles used in reinforcing walls, berms and slopes Geotextiles used in reinforcing embankment and foundations Geotextiles used for cushioning Determine the function s of the geosynthetic 3.
Calculate, estimate, or otherwise determine the required property value for the function s 4. Test or otherwise obtain the allowable property of the candidate geosynthetic material 6. Determine if the resulting factor of safety is significantly high for the site-specific situation under consideration 7. Prepare specifications and construction documents 8.
Observe construction and post-construction performance. For example, a major cause of failure of roadways constructed over soft foundations is contamination of the aggregate base courses with the underlying soft subgrade soils Figure Contamination occurs due to: 1 penetration of the aggregate into the weak subgrade due to localized bearing capacity failure under stresses induced by wheel loads, and 2 inclusion of fine-grained soils into the aggregate because of pumping or subgrade weakening due to excess pore water pressures.
Subgrade contamination results in inadequate structural support, which often leads to premature failure of the system. A geotextile can be placed between the aggregate and the subgrade to act as a separator and prevent the subgrade and aggregate base course from mixing Figure Among the different geosynthetics, geotextiles have been the products generally used in the function of separation.
Examples of separation applications are the use of geotextiles between subgrade and stone base in roads and airfields, and between geomembranes and drainage layers in landfills. In addition to these applications, in which separation is the primary function of the geotextile, it could be said that most geosynthetics generally include separation as a secondary function.
Geosynthetics used as erosion control systems can also be considered as performing a separation function.
In this case, the geosynthetic separates the ground surface from the prevailing atmospheric conditions i. Specialty geocomposites have been developed for the specific purpose of erosion control.
The general goal of these products is to protect soil slopes from both sheet and gully erosion, either permanently or until vegetation is established.
General references on the design of geosynthetics for separation applications can be found in Christopher and Holtz and in Koerner Separation function of a geotextile placed between road aggregate and soft subgrade.
Design and construction of stable slopes and retaining structures within space constraints are aspects of major economical significance in geotechnical engineering projects. For example, when geometry requirements dictate changes of elevation in a highway project, the engineer faces a variety of distinct alternatives for designing the required earth structures.
Traditional solutions have been either a concrete retaining wall or a conventional, relatively flat, unreinforced slope Figure Although simple to design, concrete wall alternatives have generally led to elevated construction and material costs. On the other hand, the construction of unreinforced embankments with flat slope angles dictated by stability considerations is an alternative often precluded in projects where design is controlled by space constraints.
Geosynthetic products typically used as reinforcement elements are nonwoven geotextiles, woven geotextiles, geogrids, and geocells. Reinforced soil vertical walls generally provide vertical grade separations at a lower cost than traditional concrete walls. Reinforced wall systems involve the use of shotcrete facing protection or of facing elements such as precast or cast-in-place concrete panels.
Alternatively, steepened reinforced slopes may eliminate the use of facing elements, thus saving material costs and construction time in relation to vertical reinforced walls. As indicated in Figure The effect of geosynthetic reinforcements on the stability of sand slopes is 12 illustrated in,which shows a reduced scale geotextile-reinforced slope model built using dry sand as backfill material. As indicated in Table Both adequate hydraulic conductivity provided by a geotextile with a relatively open structure and adequate soil retention provided by a geotextile with a relatively tight structure should be offered by the selected product.
In addition, considerations should be made regarding the long-term soil-to-geotextile flow compatibility such that the flow through the geotextile will notreduce excessively by clogging during the lifetime of the system. The geosynthetic-to-soil system should then achieve an equilibrium that allows for adequate liquid flow with limited soil loss across the plane of the geotextile over a service lifetime compatible with the application under consideration. Filtration concepts are well established in the design of soil filters, and similar concepts can beused in the design of geotextile filters.
As the flow of liquid through the geotextile increases, the geotextile voids should be larger. However, large geotextile voids can lead to an unacceptable situation called soil piping, in which the soil particles are continuously carried through the geotextile, leaving large soil voids behind.
The liquid velocity then increases, which accelerates the process and may lead to the collapse of the soil structure. This process can be prevented by selecting a geotextile with voids small enough to retain the soil on the upstream side of the fabric. It is the coarser soil fraction that must be initially retained.
The coarser-sized particles eventually filter the finer-sized particles and build up a stable upstream soil structure Figure The test method used in the United States to determine the geotextile opening size is called the apparent opening size AOS test.
The drainage function of geosynthetics allows for adequate liquid flow with limited soil loss within the plane of the geotextile over a service lifetime compatible with the application under consideration. Thick, needle-punched nonwoven geotextiles have considerable void space in their structure and canconvey large amounts of liquid. Geocomposite drains can transmit one to two orders of magnitude more liquid than geotextiles.
Proper design should dictate what type of geosynthetic drainage material is necessary. Except for the consideration of flow direction, the soil retention and the long-term compatibility considerations regarding the drainage function of geosynthetics are the same as those discussed in Section The geotextile, either when used as a drain itself or when placed onto a core to form geocomposite must fulfill the filtration function. The compatibility of the soil with the geotextile filter must be ensured over the lifetime of the system being built.
General references on design methods for the use of geosynthetics for drainage applications can be found in Holtz et al. As shown in Table Geosynthetic barriers are commonly used as liners for surface impoundments storing hazardous and nonhazardous liquids, as covers above the liquid surface of storage reservoirs, and as liners for canals used to convey water or chemicals.
Geosynthetic barriers are also used as secondary containment for underground storage tanks and in applications related to dams and tunnels. Of particular relevance for groundwater applications is the use of geosynthetic barriers for seepage control HDPE vertical barrier systems. A common application of geosynthetics as infiltration barriers is for base and cover liner systems of landfills.
In landfill applications, infiltration barriers are 14 typically used instead of or in addition to low-hydraulic conductivity soils.
Base liners are placed below the waste to prevent liquids from the landfill leachate from contaminating the underlying ground and the groundwater. Geosynthetic cover liner systems are placed above the final waste configuration to keep precipitation water from entering the waste and generate leachate. If a building or other structure is constructed on a landfill, a geosynthetic barrier may be placed under the building foundation to provide a barrier for vapors such as landfill gas. The use of geosynthetics in infiltration barriers is further described in Koerner 6.
A common example is the use of geotextiles to provide protection against puncture of geomembranes in waste and liquid containment systems. Adequate mechanical protection must be provided to resist both short-term equipment loads and long-term loads imparted by the waste. Experience has shown that geotextiles can play an important role in the successful installation and longerterm performance of geomembranes by acting as a cushion to prevent puncture damage of the geomembrane.
In the case of landfill base liners, geotextiles can be placed 1 below the geomembrane to resist puncture and wear due to abrasion caused by sharp-edged rocks in the subgrade, and 2 above the geomembrane to resist puncture caused either by the drainage aggregate or direct contact with waste materials. Likewise, in the case of landfill cover liners, geotextiles can be placed below the geomembrane to reduce risk of damage by sharp objects in the landfill and above the geomembrane to prevent damage during placement of drainage aggregate or cover soil.
Key characteristics for the geotextile cushions are polymer type, mass density, method of manufacture, and construction survivability. Detailed procedures and methods for conducting these evaluations are described by Holtz et al. The fabrics are used to provide tensile strength in the earth mass in locations where shear stress would be generated.
Moreover, to allow rapid dewatering of the roadbed, the geotextiles need to preserve its permeability without losing its separating functions. Its filtration characteristics must not be significantly altered by the mechanical loading. Railway Works: The development of the railway networks is being greatly boosted by the present state of economy because of their profitability in view of increasing cost of energy and their reliability as a result of the punctuality of trains even in the adverse weather conditions.
The woven fabrics or non-wovens are used to separate the soil from the sub-soil without impeding the ground water circulation where ground is unstable.