Effect of Soil Reinforcement on Shear Strength by Pennisetum alopecuroides and Miscanthus sinensis Roots on Loamy Sand at River Banks

ABSTRACT Natural sisal fiber is an environment-friendly and efficient material for soil reinforcement. Many studies have reported that the shear strength of soil has been improved by the addition of fiber. However, the mechanical properties of sand can be more effectively improved by the incorporation of water-based polymer and sisal fiber. An extensive laboratory testing program was conducted to determine the effect of water-based polyurethane and sisal fiber reinforcement on sand. Laboratory tests included sieve analysis, X-ray diffraction, conventional triaxial compression, and scanning electron microscopy (SEM) tests. The effects of polymer content (PC), fiber content (FC), fiber length (FL), and sample dry density (ρ) are thoroughly investigated. The results indicate that the increases of PC, FC, and ρ all improve the mechanical properties of sand. For FL, this improvement in shear strength was maintained to FLs of up to 18 mm. Beyond 18 mm, the shear strength decreased with further increase in FL. The mixing of polymer and fiber changes the failure mode from shear faulting to ductile flow. This indicates that the ductility of sand is improved. From the SEM images we found that sisal fibers, binding with colloidal materials formed by polymer, fill the sand voids and join the sand particles. This demonstrates that mixing of fiber and polymer can enhance the bonding of sand particles.

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Mechanical Behaviour of Reinforced Sand with Natural Curauá Fibers through Full Scale Direct Shear Tests

E3S Web of Conferences ◽

10.1051/e3sconf/20199212003 ◽

2019 ◽

Vol 92 ◽

pp. 12003

Author(s):

Leila Maria Coelho de Carvalho ◽

Michelé Dal Toé Casagrande

Keyword(s):

Shear Strength ◽

Sandy Soil ◽

Soil Reinforcement ◽

Direct Shear ◽

Shear Strength Parameters ◽

Shear Tests ◽

Strength Parameters ◽

Direct Shear Tests ◽

Soil Shear Strength ◽

Curaua Fibers

Inclusion of natural fibers (sisal, curauá, coco fiber and others) for soil improvement has been the study object in diverse geotechnical areas and it is a topic of growing interest, within the research area of new geotechnical materials. The state of the art in this subject highlights excellent results as soil strength parameters improve and post-cracking strength (toughness) increase. Soil reinforcement technique with fibers is established in the technology of composite materials, this being a combination of two or more materials presenting properties that the component materials do not possess on their own. The aim of this paper is to study the mechanical behaviour of sand-fiber composite by inserting natural curauá fibers into a sandy matrix, with different fiber contents. The fibers were randomly distributed in the soil mass. The experimental program included physical and mechanical characterization of the composites, using full-scale direct shear tests, with samples measuring 30 x 30 cm and 15 cm high. Direct shear tests were carried out using fibers with 25 mm length and 0.5 and 0.75% fiber content (relative to the soil dry weight). The specimens also presented a relative density of 50% and moisture content of 10%. It was sought to establish a pattern behaviour so that the addition of curauá fiber influence can be explained, thus, comparing with the sandy soil shear strength parameters. Inclusion of natural curauá fibers as soil reinforcement presented satisfactory results, as an increase in the soil shear strength parameters was observed when compared with sandy soil results.

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In situ shear tests of soil blocks with roots

Canadian Geotechnical Journal ◽

10.1139/t98-027 ◽

1998 ◽

Vol 35 (4) ◽

pp. 579-590 ◽

Cited By ~ 64

Author(s):

Tien H Wu ◽

Alex Watson

Keyword(s):

Shear Strength ◽

Root System ◽

Tensile Force ◽

Failure Surface ◽

Soil Reinforcement ◽

Shear Tests ◽

Maximum Displacement ◽

Shearing Resistance ◽

Simplified Procedures

In situ shear tests were performed on soil blocks that contained roots to study the contribution of roots to the shear strength in a case where the shear deformation is not constrained to a thin zone. The shearing resistance of the soil-root system, the tensile force in selected roots, and the deformation of the soil block were measured. The roots were exposed after the test and their positions were determined and used to estimate the initial positions. The root force and the shearing resistance of the soil-root system were estimated with known solutions and compared with measured root force and shearing resistance. None of the roots that passed through the shear zone failed in tension at the maximum displacement. As a consequence, the root resistance is much less than that found in a case where the failure surface is restricted to the boundary between a weak soil and a firm base and where roots are anchored in the firm base and fail in tension. Simplified procedures for estimating root forces are suggested for the case of a thick shear zone.Key words: in situ test, roots, shear strength, slope stability, soil reinforcement, soilroot interaction.

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An approximate method for estimating the stability of geotextile-reinforced embankments

Canadian Geotechnical Journal ◽

10.1139/t85-050 ◽

1985 ◽

Vol 22 (3) ◽

pp. 392-398 ◽

Cited By ~ 43

Author(s):

R. K. Rowe ◽

K. L. Soderman

Keyword(s):

Finite Element ◽

Shear Strength ◽

Limit Equilibrium ◽

Soft Clay ◽

Soil Reinforcement ◽

Short Term ◽

Critical Height ◽

Reinforced Embankments ◽

The Stability ◽

Conventional Limit

A method of estimating the short-term stability of reinforced embankments constructed on a deposit that can be idealized as being uniform and purely cohesive is described. This approach maintains the simplicity of conventional limit equilibrium techniques while incorporating the effect of soil–geotextile interaction in terms of an allowable compatible strain for the geotextile. This allowable compatible strain may be deduced from a design chart and depends on the foundation stiffness, the embankment geometry, the depth of the deposit, and the critical height of an unreinforced embankment. The procedure is checked against finite element results and against one published case history. Key words: embankment, geotextile, analysis, limit equilibrium, finite element, soft clay, shear strength, soil reinforcement.

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Effect of Salt Spray Concentration on Growth and Appearance of ‘Gracillimus’ Maiden Grass and ‘Hamelin’ Fountain Grass

HortTechnology ◽

10.21273/horttech.18.1.34 ◽

2008 ◽

Vol 18 (1) ◽

pp. 34-38 ◽

Cited By ~ 8

Author(s):

S.M. Scheiber ◽

David Sandrock ◽

Erin Alvarez ◽

Meghan M. Brennan

Keyword(s):

Plant Biomass ◽

Salt Spray ◽

Foliar Spray ◽

Coastal Communities ◽

Miscanthus Sinensis ◽

Salt Tolerant ◽

Landscape Plants ◽

Whole Plant ◽

Pennisetum Alopecuroides ◽

Seawater Concentration

Salt-tolerant landscape plants are important to ornamental growers, landscapers, and residents in coastal communities. Ornamental grasses are frequently recommended for low-maintenance landscape situations and may be candidates for coastal plantings after they are evaluated for their salt spray tolerance. ‘Gracillimus’ maiden grass (Miscanthus sinensis) and ‘Hamelin’ fountain grass (Pennisetum alopecuroides) were subjected to four treatments [100% seawater salt spray, 50% seawater salt spray, 25% seawater salt spray, or 0% seawater salt spray (100% deionized water)] applied as a foliar spray. As seawater concentration increased, root, shoot, whole-plant biomass gain, height, inflorescence number, and visual quality decreased for both cultivars; however, fountain grass appears to be slightly more tolerant of salt spray than maiden grass.

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Germination and Early Growth Characteristics of Pennisetum alopecuroides, Phragmites communis, and Miscanthus sinensis According to the Seeding Methods

Journal of the Korea Society of Environmental Restoration Technology ◽

10.13087/kosert.2014.17.1.163 ◽

2014 ◽

Vol 17 (1) ◽

pp. 163-172 ◽

Cited By ~ 3

Author(s):

Yong-Hyeon Cho ◽

Ka-Hyung Lee

Keyword(s):

Early Growth ◽

Growth Characteristics ◽

Miscanthus Sinensis ◽

Phragmites Communis ◽

Pennisetum Alopecuroides

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Small Divisions of Ornamental Grasses Produce the Best Growth Following Direct Potting

HortScience ◽

10.21273/hortsci.34.6.1126 ◽

1999 ◽

Vol 34 (6) ◽

pp. 1126-1128 ◽

Cited By ~ 2

Author(s):

Mark H. Brand

Keyword(s):

Panicum Virgatum ◽

Grass Species ◽

Size Difference ◽

Miscanthus Sinensis ◽

Plant Weight ◽

Simplified Approach ◽

Grass Production ◽

Ornamental Grasses ◽

Pennisetum Alopecuroides ◽

Bare Root

Potting of bare-root spring divisions is a simplified approach to ornamental grass production. Large and small divisions of eight common ornamental grasses were directly potted into 7-L nursery containers and grown outdoors for 20 weeks to determine an appropriate division size for each grass. Response to division size was dependent on the grass species. Large divisions of Calamagrostis ×cutiflora `Karl Foerster' (Schräd.) produced twice as many inflorescences as small divisions. At harvest, large divisions of Miscanthus oligostachyus `Purpurascens' (Stapf.) had twice as many inflorescences and 1.5 times as many tillers as small divisions. However, new tiller production in large divisions was only 50% of that in small division plants. Large divisions of Miscanthus sinensis (Anderss.) cultivars produced more tillers and greater fresh and dry weights than did small divisions, but again, the differences were not proportional to the size difference between the initial divisions. Large divisions of Panicum virgatum (L.) produced 50 more tillers per plant than did small divisions, but plant weight, size, and number of inflorescences were not affected by division size. Plants from large divisions of Pennisetum alopecuroides (L.) Spreng. were 7 cm shorter than small divisions and produced 24% more inflorescences and 27% more tillers, but appeared nutrient and/or water stressed. For most grasses, smaller division size is recommended for direct spring potting.

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Model Tests of Soil Reinforcement Inside the Bucket Foundation with Vacuum Electroosmosis Method

Applied Sciences ◽

10.3390/app9183778 ◽

2019 ◽

Vol 9 (18) ◽

pp. 3778 ◽

Cited By ~ 1

Author(s):

Hanbo Zhai ◽

Hongyan Ding ◽

Puyang Zhang ◽

Conghuan Le

Keyword(s):

Shear Strength ◽

Moisture Content ◽

Bearing Capacity ◽

Soil Moisture Content ◽

Soil Reinforcement ◽

Vacuum Preloading ◽

Bucket Foundation ◽

Capacity Model ◽

Vertical Bearing ◽

Vertical Bearing Capacity

Offshore wind turbine foundations are commonly subjected to large horizontal, vertical, and bending moment loads. Marine soils have high moisture content, high compressibility, high sensitivity, and low strength, resulting in insufficient foundation bearing capacity. In order to improve the bearing capacity of wind turbine foundations and reduce foundation settlement, an internal vacuum preloading method combined with electroosmosis reinforcement is used to reinforce the soil within bucket foundations. The pore water pressure, vertical settlement, pumping quality of the soil during the reinforcement process, soil moisture content before and after the reinforcement, and undrained shear strength were analyzed. Horizontal and vertical bearing capacity model tests were carried out on the reinforced and nonreinforced soil inside the bucket foundation. Results show that vacuum preloading combined with electroosmosis reinforcement reduces soil moisture content inside the bucket foundation by approximately 20%, and the undrained shear strength of the internal soil increases by approximately 20 times. Soil reinforcement has high spatial uniformity. Results of the bucket foundation bearing capacity model show that when the soil inside the bucket foundation is strengthened, horizontal bearing capacity increased by 2.9 times and vertical bearing capacity increased by 2.1 times. Vacuum preloading combined with electroosmosis reinforcement can effectively improve the shear strength of soft soil and enhance the bearing capacity and stability of bucket foundations.

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The Reinforcement of Sand by Fibres with a Non-Uniform Shape

Slovak Journal of Civil Engineering ◽

10.2478/sjce-2021-0013 ◽

2021 ◽

Vol 29 (2) ◽

pp. 49-54

Author(s):

Pavel Koudela ◽

Juraj Chalmovský ◽

Lumír Miča

Keyword(s):

Shear Strength ◽

Fibre Composite ◽

Coarse Sand ◽

Theoretical Background ◽

Soil Reinforcement ◽

Triaxial Tests ◽

Fused Deposition Modelling ◽

Peak Shear Strength ◽

Fused Deposition ◽

Variable Shape

Abstract The reinforcement of soil is used to improve its strength and stiffness. The standard method of soil reinforcement is an application of geosynthetics. Soil reinforcement by distributed discrete fibres represents an alternative to those techniques. Currently used fibres have a straight shape, uniform cross-section, and smooth surface, which is not optimal in terms of the fibre-soil interaction. In this study, fibres with a variable shape were utilized. The fibres were fabricated using a fused deposition modelling technology. Firstly, a brief theoretical background is presented. Then, the proposed shapes of the fibres and their manufacturing process are described. The mechanical properties of the soil-fibre composite were investigated through consolidated drained triaxial tests. Well-graded coarse sand and poorly-graded fine sand were used. A higher peak shear strength was observed in the case of fibres with a variable shape. The effect of the variable shape of the fibres on the peak shear strength was higher in the case of the coarse sand.

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