Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials

Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials Soil improvement and ground modification methods chapter 18 emerging technologies, trends, and materials

Emerging Technologies, Trends, and Materials

As technology advances, equipment improvements are made, environmen-tal concerns become mainstream, and sustainability becomes ingrained throughout engineering practice, new advancements continue to be made

in soil and ground improvement This final chapter addresses some of the approaches being developed in looking forward to implementing new methods, ideas, and materials into engineering practice The desire for LEED geotechnical construction has also provided an impetus to contractors

to reuse and reduce the carbon footprint from that of more traditional methods

18.1 WHAT’S NEW—WHAT’S AHEAD?

Throughout this text, along with discussion of the various methods of soil improvement, admixtures, inclusions, and so forth, there have been ref-erences to new and emerging technologies, materials, equipment, and prac-tices While this has been noted, it seems appropriate to include one additional chapter devoted to addressing some these subjects

In virtually all ground improvement methods, there continue to be advancements that increase efficiency, lower costs, and address environmen-tal concerns by making use of recycled materials Take, for example, explo-sive replacement, which is a recent advancement for deep densification This technique uses explosives to create voids, which are then filled with crushed stone This method was successfully applied to improve strength and settle-ment characteristics of foundation soils to support highway embanksettle-ments in China (Shuwang et al., 2009) The constantly growing use of geosynthetics and new types of geosynthetic materials make these areas of improvements ever changing

Because these emerging technologies are ongoing, the content of this chapter will undoubtedly be out-of-date by the time of publication With that said, only a few areas of particular note will be addressed here

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18.2 UTILIZATION OF WASTES

As environmental concerns continue to grow worldwide and limitations on available disposal sites become more apparent, there have been tremendous advances in recycling or utilization of waste materials While not all waste

is suitable for geotechnical applications, much of the waste stream has been shown to be useful, often providing cost savings as well as environmental benefits These waste materials range from surplus soil and waste slurry from construction projects, to industrial waste and by-products, to munic-ipal waste A number of federal and state initiatives in the United States have promoted and provided incentives for the use of recycled materials, particularly for transportation projects Use of recycled materials is even required for some federally funded projects Advancements and improve-ments in material processing and field construction techniques have also improved the reliability and cost-effectiveness of these materials for general civil engineering construction (Aydilek and Wartman, 2004)

The waste stream can be divided into three major categories: (1) waste material that can be utilized “as is” without treatment and poses minimal environmental concerns, (2) waste that can be stabilized or treated so that the resulting material will be stable and nonhazardous, and (3) materials such

as waste sludge, waste oil, waste plastics, and so on, the treatment of which are very difficult for various technical and economic reasons (Kamon

et al., 2000)

Large amounts of fly ash are generated annually from the burning of coal

as fuel for electricity production Fly ash has been known for a long time to

be a useful admixture for cement and, with the right composition, has also been demonstrated to improve a number of properties, especially for certain

“poor” soil types The attributes of fly ash were described inChapter 11, but its use continues to increase and, therefore, merits a mention here Municipal solid waste (MSW) ash is generated by combustion of the municipal waste stream This process has been gaining popularity because

it has the advantage of reducing the volume of waste that otherwise would

be placed in limited landfills, as well as providing a complementary power supply fuel source The residual ash has some of the same qualities as other ash by-products, but may also have irregular levels of hazardous components due to the variability of the source materials This variability will be mostly dependent on regional location, but may be fairly uniform locally Studies have shown a number of soil improvement/use attributes for MSW ash, including landfill covers, fill material, and as a soil-stabilizing admixture Its future use will depend on monitoring of hazardous contaminant levels

Waste paper sludge, or fiber-clay, as it is sometimes called when used as a recycled material, has been shown to serve as a cover material for sanitary landfills due to its high residual clay content (Simpson and Zimmie,

2005) It has also been used as a component of secondary roadway materials and as kitty litter

Recycled concrete is now becoming regularly used in new construction, either as aggregate fill, for rammed aggregate piers, as roadway base, as riprap, or as aggregate for new concrete (www.geopier.com; www.en wikipedia.org) This offers environmentally safe and sustainable LEED point enhancement to those using it by reducing the “carbon footprint” associated with cement production At the time of this writing, it is estimated that over

140 million tons of concrete are recycled annually in the United States alone (www.cdrecycling.org)

Ground granulated blast furnace slag (GGBFS) is a by-product from the blast furnaces used to make iron It is used as a “substitute” or filler for cement that allows for water reduction of 3-5% in concrete without any loss in work-ability In the same manner that fly ash is added to cement, GGBFS may also

be a suitable additive when cement is used as a soil improvement admixture

It may aid in the ability to mix cement with certain soil types and may add to the ultimate strength gains for treated soils

Steel slag is a by-product of smelting and refining steel Steel slag fines are produced from the crushing and screening process, where the larger sizes of steel slag are used as aggregate for transportation construction or structural fill as specified in ASTM D5106 Steel slag fines were demonstrated to be a useful additive to stabilize and treat dredged material for use in highway embankments, while immobilizing arsenic (Grubb, 2011; Grubb et al.,

2013) and copper (Ruiz et al., 2013) in contaminated sediments It was further shown that steel slag was potentially beneficial at immobilizing copper-contaminated sediments by capping in place Recent research has also shown that steel slag can successfully immobilize elevated concentra-tions of phosphate, which may cause algal blooms and pfisteria in aquatic environments (Ruiz et al., 2013)

Utilization of crushed glass, either by itself as an aggregate or as an additive, has been studied, but has not yet seen significant application in geotechnical construction Crushed glass, however, has been used as a substitute for sand and fine gravel in asphalt pavements for nearly 20 years Recycled glass has potential applications as fill material and drainage material in road works, although coarse sizes have been found to be unsuitable for most geotechnical applications (Disfani et al., 2011) Preliminary test studies indicate that recycled glass is most suitable when mixed with other materials, such as

natural aggregate or waste rock for base material with up to 30% recycled glass Some concerns have been expressed regarding environmental risk, including handling

18.3 BIOREMEDIATION

Bioremediation includes emerging trends, practices, and research using living plants and organisms to stabilize and make improvements for geotech-nical and geoenvironmental applications

18.3.1 Biostabilization Applications

One application of bioremediation is through the use of vegetation for stabi-lization of slopes, particularly shallow surface materials Added vegetation can have some significant added benefits as well as some adverse effects The benefits include (Abramson et al., 2002):

• Interception of rainfall by foliage (including evaporative losses)

• Reduction of soil moisture and increase of soil suction by uptake from plant root systems and transpiration

• Physical soil reinforcement by root systems

“catchment” by shrubs and trees

• Stabilization by buttressing and arching between adjacent trees

But at the same time, a number of adverse conditions are generated that should be addressed and/or accounted for Because of this, some experts advocate for minimal “heavy” vegetation on slopes and embankments (especially earthen dams and levees) These provide:

• Increased potential for water infiltration into a slope

• Increased seepage paths, especially when root systems biodegrade

• Surcharging slopes with added weight of heavy vegetation

In addition, vegetating slopes provide an aesthetically pleasing environmen-tal attribute and can quickly beautify a constructed, cut, or reworked slope

18.3.2 Contaminant Remediation

Other types of bioremediation being studied utilize microorganisms such

as algae, bacteria, fungi, and other microorganisms to break down organic matter (including hydrocarbons) in efforts to “clean up” environmental con-taminants (ei.cornell.edu; oilandgas.ohiodnr.gov) This may be done by enhancing the growth of pollution-eating microbes to speed up the natural

biodegradation processes, or by introducing specialized microbes to degrade the contaminants

18.3.3 Inorganic Precipitation

DeJong et al (2010) describe “biomediated” treatments to improve soil properties without addition of synthetic materials, by harnessing natural biological processes The premise is that inorganic calcite precipitation facil-itated by biological activity can significantly improve stiffness and strength, while decreasing compressibility and permeability of in situ soil formations Research at the University of Western Australia has analyzed the use of natural and synthesized calcium (calcite) precipitates These studies have also shown promise for strengthening calcareous soils for use with offshore structure foundations in tropical and subtropical regions where coral and calcareous sands and gravels are present (Kucharski et al., 1997)

REFERENCES

Abramson, L.W., Lee, T.H., Sharma, S., Boyce, G.M., 2002 Slope Stability and Stabilization Methods, 2nd ed., John Wiley & Sons, Inc., 717p.

Aydilek, A.H., Wartman, J (Eds.), 2004 Recycled Materials in Geotechnics ASCE, Reston, Virginia, Geotechnical Special Publication No 127, 229 pp.

DeJong, J.T., Mortensen, B.M., Martinez, B.C., Nelson, D.C., 2010 Bio-mediated soil improvement Ecol Eng 36 (2), 197–210.

Disfani, M.M., Arulrajah, A., Bo, M.W., Hankour, R., 2011 Recycled crushed glass in road work applications J Waste Manage 31 (11), 2341–2351, Elsevier.

Grubb, D., 2011 Recycling on the waterfront Geo-Strata March/April, 24–29, ASCE Grubb, D., Wazne, M., Jagupilla, S., Malasavage, N., Bradfield, W., 2013 Aging effects in field-compacted dredged material: steel slag fines blends J Hazard Toxic Radioact Waste 17 (2), 107–119.

Holtz, R.D., Schuster, R.L., 1996 Stabilization of slopes in landslide investigation and mitigation Transportation Research Board special report 247, National Academy Press, Washington, DC, pp 429–473.

Kamon, M., Hartle´n, J., Katsumi, T., 2000 Reuse of waste and its environmental impact In: Proceedings of Geo Eng 2000, Melbourne, Australia, 28 pp.

Kucharski, E., Price, G., Li, H., Joer, H.A., 1997 In: 30th International Geological Congress, Beijing, China Engineering Properties of CIPS Cemented Calcareous Sand, vol 23 International Science, pp 449–460.

Ruiz, C.E., Grubb, D.G., Acevedo-Acevedo, D., 2013 Recycling on the waterfront II Geo-Strata July/August, 40–44, ASCE.

Shuwang, Y., Wei, D., Jin, C., 2009 In: Use of Explosion in Improving Highway Founda-tions ASCE Publications, Reston, VA, pp 290–297, Geotechnical Special Publication 188.

Simpson, P.T., Zimmie, T.F., 2005 In: Waste Paper Sludge—An Update on Current Technology and Use ASCE, Reston, VA, pp 75–90, Geotechnical Special Publication

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