Muskegon dune sand and mortar sand mixed with rubber, reed (natural), and glass (synthetic) fibers
The integration of fiber heavily influenced the stiffness and ultimate strength of the soil due to parameters including aspect ratio and weight fraction of fiber as well as gradation and particle geometry. The addition of fiber, as well as fiber modulus, is linearly proportional to the increase in shear strength. The optimum glass fiber content was 3% (by weight) with lowest fiber aspect ratio () of 60
Woven (polypropylene), nonwoven geotextile, and coir fibers with sand
Coir fiber provided the best performance in terms of liquefaction resistance due to the high soil-fiber interface followed by nonwoven geotextiles due to high stiffness and lastly woven geotextiles. Hence, the liquefaction resistance increases as the stiffness, stress ratio, and interface friction increase. Moreover, the effect of fiber on liquefaction resistance increases as the spacing of reinforcement and relative density decrease. No percentage of fiber content was presented in the study
The presence of fibers in the sand increases the peak shear strength and decreases the loss of postpeak stress. Moreover, the increase in shear strength is directly attributed to the increase in fiber content by up to 2%. The shear strength rises with the increase in fiber aspect ratio while critical confining stress is reduced. The optimum fiber content was 2% (by weight) with fiber aspect ratio ranging between 60 and 90
Woven (polypropylene), nonwoven geotextile, and coir fibers with sand
Woven, nonwoven, and natural coir fibers were added in one and two layers to the soil. The soil-fiber interface, bending stiffness, and compressibility of fiber have a significant impact on the shear mobilization. Moreover, the stiffness of fiber is proportional to the shear mobilization where any increase in the stiffness increases shear mobilization. On the other hand, the compressibility of fiber is inversely proportional to the shear mobilization where any increase in compressibility results in a decrease in the shear mobilization. The best result was seen in the case of coir fiber with one layer where it produced the highest angle of interface friction and stiffness
Hostun RF sand reinforced with nonwoven geotextiles (polyester)
When the stress ratio is lower than the cyclic resistance, the liquefaction resistance rises due to the friction between soil and fiber. In case, the stress ratio is higher than cyclic resistance, the liquefaction resistance increases due to the deformable nature of the fiber. During testing, the sand is subjected to repetitive expansion cycles but the fiber causes a delay in the liquefaction by means of minimizing the interstitial pressure in the sand. No specific optimum fiber content was presented in the study
Fly ash with fiber and mesh (nonwoven polypropylene geogrid sheets) reinforcement
The incorporation of geosynthetic fiber and mesh reinforcement is inversely proportional to the confining stress and relative density where any decrease in confining stress and relative stress results in a rise in liquefaction resistance. However, mesh reinforcement showed better performance compared to fiber reinforcement because mesh reinforcement produces better interlocking and easier pore water pressure dissipation. The optimal fiber/mesh content to increase liquefaction resistance is approximately 2%
Toyoura sand reinforced with (woven, nonwoven) geosynthetics
The addition of fibers to sand resulted in an increase in the liquefaction resistance up to 266% and 258% for one and four layers of woven and nonwoven geotextiles respectively. Furthermore, the type (woven and nonwoven) and arrangement (from one to four layers) of fiber play an important role in the liquefaction resistance of the soil. Woven and nonwoven geotextiles enhanced the liquefaction resistance of reinforced soil because the sand layers are isolated by geotextiles. Soil mixed with nonwoven geotextiles exhibited superior performance in terms of liquefaction resistance due to its dense structure and low elastic modulus in comparison to woven geotextiles. The best performance was exhibited by four layered nonwoven geotextiles at stress ratio of 0.125
Conventional triaxial compression and extension test
Hostun RF sand reinforced with short polypropylene fibers
The modeling method is quietly useful for enabling different fiber orientation functions. The fiber heavily influences the strength in compression but has negligible influence on strength in tension due to orientation in regard to tensile strains. The optimum fiber content was 0.9% (by weight)
Conventional drained and undrained triaxial compression and extension test
Hostun RF sand with Loksand flexible polypropylene crimped fibers
During the drained test, the increase of strength due to the addition of fibers is directly dependent on the content and direction of the arrangement. The volume of the mixture is highly affected by fibers for compression and tension loading since fibers fill the voids in the sand despite the fact that the stress-strain relationship is slightly affected. During undrained, the increase of strength due to the addition of fibers for both compression and tension is clearly noticeable as well as transforming softening of strain into hardening. Finally, the inclusion of fiber resulted in minimization or elimination of static liquefaction for both compression and extension regardless of the fact that liquefaction in extension requires a higher number of fibers. The optimum fiber content was 0.9% (by weight)
The incorporation of fiber into clay limited the crest settlement, maximum shear strains as well as horizontal and vertical displacement of the embankment. In addition to that, fibers intensified the maximum horizontal crest acceleration. No specific optimum fiber content was presented in the study. However, the average efficiency of the used nonwoven geotextile was 0.8. The highest reduction of horizontal and vertical displacements for the dam heights of 15, 25, and 40 m was recorded with 1.5 m geotextile spacing
The addition of polypropylene fiber showed little to no significant effect on the loose reinforced sand regardless the reinforced specimen maintained structural stability whereas the unreinforced one completely failed. Hence, fibers possess the ability to reduce or eliminate the lateral spreading of sand. On the other hand, the addition of fiber showed a noticeable effect on moderately dense and dense reinforced specimens in terms of displaying fluctuations after shear failure, unlike unreinforced samples. In addition to that, moderately dense and dense reinforced specimens as well as dense unreinforced specimens maintained structural stability in comparison to the moderately dense unreinforced specimen which partly failed. Lastly, fiber reinforcement provided partial decrease or entire prevention of the lateral spreading caused by static liquefaction. The optimum fiber content was 0.8% (by weight)
Solani sand reinforced with a geogrid sheet, geosynthetic fiber, and natural coir fiber
The inclusion of coir fiber reflected the best result in terms of liquefaction resistance compared to other reinforcement types. Coir fiber at 0.75% and 0.1 g acceleration provided improvement of liquefaction resistance up to 91% while synthetic fiber at the same fiber percentage and acceleration magnitude provided 88% improvement and geogrid sheets (five layers) at the same acceleration magnitude provided 31% improvement. The addition of fibers is inversely proportional to the acceleration magnitude whereas any reduction in acceleration magnitude (from 0.4 g to 0.1 g) leads to an increase in liquefaction resistance. Lastly, the reinforced sand exhibited a good effect by means of minimizing the settlement. The optimum fiber content was 0.75% (by weight) for coir fiber and geogrid sheets (five layers)
HST95 congleton sand with crimped polypropylene fiber
The presence of fiber in soil enhanced the liquefaction resistance by means of increasing the shear stress cycles to reach the maximum excess pore water pressure. No specific fiber content was presented in the study
Stress-controlled cyclic triaxial test under undrained conditions
Babolsar sand with randomly distributed monofilament polypropylene
Fiber content and length showed a crucial positive effect on the required cycles number to reach liquefaction. 1% fiber content resulted in the highest liquefaction resistance of 280%. Shear modulus improves with the increase of fiber content. Lastly, fibers can be useful in reducing or eliminating the lateral movement of soil due to liquefaction. The optimum fiber content was 1% (by weight)
The inclusion of fiber in the backfill significantly limited the lateral displacement of the quay wall and backfill settlement. The usage of fiber as reinforcement in soil prevented quay wall movement caused by excess pore water pressure. The optimum fiber content was 0.6% (by weight)
Liquefiable silt and silty sand with laponite (synthetic layered silicate nanoparticle)
The integration of laponite in the soil prevents liquefaction by means of soil grain cementation, and pore fluid solidification and limits the initiation of pore pressure. The transition in laponite enhanced the liquefaction resistance. The addition of laponite to the soil slows the formation of pore pressure and reduces the deformation in comparison to unreinforced specimens. Despite the fact that the increase in laponite content or curing period increased the liquefaction resistance, during the first few cycles, the influence of laponite is higher while the influence of the curing period is higher after a few cycles. The optimum laponite content was 3.5% (by weight)
Cyclic triaxial compression test under undrained conditions and hollow cylinder torsional shear test
Fujian standard sand with polypropylene fiber
The inclusion of fiber in soil increased the number of cycles to reach liquefaction and hence, increased the liquefaction resistance. The fiber content and fiber length are linearly proportional to the liquefaction resistance where any increase in these parameters increased the liquefaction resistance. The incorporation of fiber in soil minimized the potential of liquefaction in both tests. The optimum fiber content was 0.8% (by weight) and the optimum fiber length was 12 mm
Babolsar sand with randomly distributed white monofilament polypropylene
The integration of fiber into sand raised the number of cycles to reach liquefaction and hence, the reinforced soil provided higher cumulative dissipation energy needed to initiate liquefaction compared to unreinforced soil. Moreover, the usage of fiber in soil increased the energy absorption capacity and in turn increased the liquefaction resistance. This is attributed to the confining pressure and relative density where the highest increase in energy absorption capacity was recorded at 250% with 1% fiber content and 40% relative density. The fiber content and fiber length are linearly proportional to the energy needed to trigger excess pore water pressure. The optimum fiber content was 1% (by weight) and the optimum fiber length was 18 mm
Stress-controlled cyclic triaxial test under undrained conditions
Loose sands, medium sands, and dense sands monofilament polypropylene fiber
The presence of fiber decreases the possibility of liquefaction. Additionally, the fiber ratio was found to increasingly influence the number of cycles to reach liquefaction. Poorly graded sand is highly affected in terms of liquefaction resistance by the addition of fiber and relative density. Another parameter affecting the soil is fiber length where the increase in fiber length increases the cyclic stress ratio because the soil matrix is linked better with longer fiber. The maximum enhancement in liquefaction resistance was noticed with 1% fiber content, 12 mm fiber length, and 50% relative density
Clean beach sand from the Gallipoli beach with monofilament polypropylene fiber
The combination of fibers in soil notably improved the number of cycles to reach liquefaction and hence, minimized the lateral movement of the soil leading to higher liquefaction resistance. Additionally, the presence of fiber in soil and the increment of fiber percentage, as well as the increment of fiber length all, limited the generation of excess pore water pressure which is attributed to the increment of energy absorption capacity. Moreover, the increment of relative density is linearly proportional to the increment in liquefaction resistance. The influence of fiber percentage on moderately dense sand (50%) was stronger than that on loose sand (30%). Lastly, the increment of fiber percentage showed the most significant effect on sand compared to the increment of fiber length. The optimum fiber content was 1% (by weight) and the optimum fiber length was 19 mm
A pneumatic controlled cyclic triaxial test under undrained conditions
Two types of sand, sand A F161 (Firoozkuh 161) and sand B F141 (Firoozkuh 141) mixed with thermoplastic polymeric microsynthetic fiber
Reinforced and unreinforced soils experience the transition from initial random loose packing (RLP) to random close packing (RCP) with the increase in silt content. In general, the increment of fiber percentage is accompanied by the increment of average contact number per particle, higher excess pore water pressure dissipation, and enhanced liquefaction resistance. The optimum fiber content was 1.5% (by weight)
Sydney sand mixed with crimped polypropylene Loksand fibers
During the drained test, the incorporation of fibers in loose soil exhibited considerable development in the strength of the soil based on the fiber percentage where any increase in fiber percentage produced higher strength. The combination of fibers with soil eliminated the static liquefaction except when the fiber content is low (0.25%) in comparison to unreinforced sand where static liquefaction is presented despite the initial confining pressure. The optimum fiber content for the consolidated drained was 0.5% and the optimum fiber content for the consolidated undrained was 0.75%
