scholarly journals Root Tensile Resistance of Selected Pennisetum Species and Shear Strength of Root-Permeated Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Afaff Emhemed Ettbeb ◽  
Zulfahmi Ali Rahman ◽  
Wan Mohd Razi Idris ◽  
Jumaat Adam ◽  
S. Abd. Rahim ◽  
...  
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Tensile Force ◽  
Mineral Fertilizer ◽  
Tensile Tests ◽  
Root Diameter ◽  
Slope Instability ◽  
Root Reinforcement ◽  
Significant Relationships ◽  
Peak Shear Stress

It is widely recognized that vegetation plays a significant role in contrasting slope instability through the root reinforcement. The main objectives of this paper are to evaluate the root tensile of selected Pennisetum species, namely, P. pedicellatum (PPd) and P. polystachion (PPl), and to determine the soil shear strength of root-permeated soil from these species. The selected species were initially planted in the polybags using the hydroseeding technique. A mineral fertilizer of NPK ratio 10 : 8 : 10 was adopted in the hydroseeding mixture. Routine watering program was applied twice a day throughout growth observation for six months. Four replications were prepared for each species including a set of control polybags, which contained only soil for reference and comparison. The results of root tensile tests revealed the significant relationships between root diameter and tensile force. In comparison, the PPl was still indicated by higher values of root tensile force than PPd. The presence of roots clearly has contributed to the shear stress of root-permeated soils. The root density based on root biomass measurement attributed to the higher value of peak shear stress as achieved by PPl than PPd. The combined effects of root tensile and the soil shear strengths of this selected species can be used as biological materials in slope protection against erosion.

scholarly journals Contribution of root tensile of Pennisetum polystachion on shear strength of sandy soil in slope bio-engineering technique

2021 ◽  
Vol 42 (3(SI)) ◽  
pp. 857-864
Author(s):  
Z.A. Rahman ◽  
◽  
A.E. Ettbeb ◽  
W.M.R. Idris ◽  
S.N.A. Tarmidzi ◽  
...  
Keyword(s):  
Shear Strength ◽  
Sandy Soil ◽  
Slope Failure ◽  
Tensile Force ◽  
Root Diameter ◽  
Slope Instability ◽  
Strength Parameter ◽  
Experimental Program ◽  
Soil Shear Strength ◽  
Bio Engineering

Aim: In soil bio-engineering, plant has been widely adopted as important material in promoting sustainable ecological function in slope instability measures. Plant canopy provides shelter and at subsurface level, root networking attributes toward stability of soil against erosion and slope failure. To investigate the potential of selected P. polystachion as biological material in soil bio-engineering for improving the soil shear strength of sandy soil planted with P. polystachion. Methodology: The selected species was initially planted using hyroseeding technique on studied plots which facilated with and without fiber netting (made of paddy straw). A control plot was also prepared for reference of this study. The plots were routinely watered twice a day for six months before experimental program was scheduled for determining of root tensile and soil shear strength tests. Results: The root tensile strength of P. polystachion exhibited a positive significant relationship between root tensile force and root diameter. The shear strength of soil was affected by the presence of root if compared to that of soil without root (control). Biomass analysist also agree with the soil water content, ws. High biomass contributed to the increase in the values of soil shear strength parameter of cohesive, c and angle of friction, q for root-permeated soil with P. polystachion. Interpretation: This study has suggested that the potential application of this selected species for slope vegetation in improving the erosion control and slope stability in soil-bioengineering scheme.

Unstable behaviour of sand and its implication for slope instability

2003 ◽  
Vol 40 (5) ◽  
pp. 873-885 ◽  
Author(s):  
J Chu ◽  
S Leroueil ◽  
W K Leong
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Critical State ◽  
Laboratory Tests ◽  
State Parameter ◽  
Slope Instability ◽  
Granular Soil ◽  
Dense Sand ◽  
Soil Slopes ◽  
New Framework

Results of some constant shear-drained (CSD) tests conducted on both loose and dense sand are presented. Using the critical state line and a modified state parameter, a new framework for analysing the instability of granular soil slopes is proposed. The test data were examined and interpreted using the new framework. Instability lines for sand with different void ratios were established within this framework. The conditions for the occurrence of instability in both contractive and dilative granular soil slopes under various shear stress levels were examined using the proposed framework.Key words: deformation, laboratory tests, liquefaction, sands, shear strength, slope stability.

scholarly journals Contribution of Tea Root Reinforcement to Soil Shear Strength on Slope Stability

2018 ◽  
Vol 4 (1) ◽  
pp. 13
Author(s):  
Mukhsin Abubakar
Keyword(s):  
Shear Strength ◽  
Slope Stability ◽  
Tensile Stress ◽  
Soil Condition ◽  
Soil Mass ◽  
Root Diameter ◽  
Root Reinforcement ◽  
Root Branching ◽  
Soil Shear Strength ◽  
Diameter Differentiation

Roots played important role in the process of stabilizing the soil mass. The geo-mechanical and soil-hydrological aspects on the slope are determined by, one of it, the root reinforcement. The role of root branching series with diameter differentiation is greatly determining its tensile stress. The tensile stress from the interaction between the root and the soil, could it contribute to increasing the shear strength of the slope stability. The purpose of this research was to identify the tensile stress on root branching series that interacted with the soil and created additional cohesion as a shear strength contribution to the slope stability. Testing on the root pulling force was conducted on slope prototype with angle 30o to 40o and has been planted with tea vegetation. A tripod that was completed with strain gauge as the recording instrument was used. Testing was conducted on two and three root branching, also on each unit by observing the diameter. This testing method was done in saturated soil condition. The tensile stress result showed that increasing diameter of the tea root, an increase was noticed, and also result in the equation of TFr = 0.089e0.516d. Root diameter increase on two and three root branching to one unit of tea vegetation showed that the stress increase was significant. When observed, in the root diameter differentiation of 4 mm to 6 mm, the stress on two and three root branching and one unit of tea vegetation were respectively 5.94%, 12.30%, and 35.42%. The contribution of additional cohesion caused by root-soil interaction to soil shear strength apparently could increase slope stability.

scholarly journals Exploring the variability in elastic properties of roots in Alpine tree species

2021 ◽  
Vol 67 (No. 7) ◽  
pp. 338-356
Author(s):  
Alessio Cislaghi
Keyword(s):  
Elastic Modulus ◽  
Elastic Properties ◽  
Tree Species ◽  
Tensile Force ◽  
Standard Procedure ◽  
Intraspecific Variability ◽  
Tensile Tests ◽  
Biomechanical Properties ◽  
Root Diameter ◽  
Soil Reinforcement

Quantifying the soil reinforcement provided by roots is essential for assessing the contribution of forests to reducing shallow landslide susceptibility. Many soil-root models were developed in the literature: from standard single root model to fibre bundle model. The input parameters of all models are the geometry of roots (diameter and length) and the biomechanical properties (maximum tensile force and elastic modulus). This study aims to investigate the elastic properties estimated by the stress-strain curves measured during tensile tests. A standard procedure detected two different moduli of elasticity: one due to the root tortuosity, and the other due to the woody fibres of roots. Based on a large dataset of tensile tests on different Alpine tree species, the relationships between elastic modulus and root diameter was estimated for each series. Further, the interspecific and intraspecific variability in such relationships was investigated by a statistical analysis. The results showed more intraspecific differences in the elastic modulus vs. root diameter relationships compared to the interspecific ones. This outcome could be an important criterion of discrimination to explain the variability of the elastic properties and to provide representative biomechanical properties for specific environmental conditions.

scholarly journals Large-Scale Direct Shear Test on Tire Slice Reinforced Crushed Concrete Particles

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Qiang Ma ◽  
Hang Shu ◽  
Jia Mou ◽  
Lihua Li ◽  
Zhenyi Zheng
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Shear Rate ◽  
Volume Content ◽  
Large Scale ◽  
Friction Angle ◽  
Vertical Load ◽  
Reinforcement Effect ◽  
Crushed Concrete ◽  
Peak Shear Stress

In order to study the mechanical properties of tire slices reinforced crushed concrete particles, a series of shear tests were carried out under the conditions of different vertical loads, different tire volume contents, and different shear rates. The test results show that the addition of tire slices can increase the internal friction angle and cohesion of concrete particles, therefore increase the shear strength of crushed concrete particles. The peak shear stress increases with the increase of vertical load. However, with the increase of the tire volume content, the reinforcement effect of the tire slices first increases and then decreases, and the effect is best when the tire volume content is 4%. Under the vertical load of 60 kPa, the reinforcement effect of 4% tire volume content is the best, and the peak shear stress increases by 46.53%. Additionally, the shear rate has a little effect on the peak shear stress. The larger the shear rate is, the smaller the shear displacement is and the faster the shear strength decreases. The smaller the shear rate is, the more gently the shear strength decreases.

Interpretation of undrained creep tests in terms of effective stresses

1995 ◽  
Vol 32 (2) ◽  
pp. 373-379 ◽  
Author(s):  
Thomas C. Sheahan
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Strain Rate ◽  
Creep Behavior ◽  
Creep Rupture ◽  
Peak Shear Stress ◽  
Stress Levels ◽  
Static Yield ◽  
Undrained Shear ◽  
Undrained Creep

The paper provides an effective stress-based interpretation technique for undrained creep behavior in cohesive soils. This technique could ultimately be used to predict whether a particular applied shear stress level will lead to failure or creep rupture. During the primary phase of undrained creep at constant shear stress, the soil's strain rate decreases, which in turn leads to a decrease in the undrained shear strength. However, it has been shown for a number of soils that a minimum undrained strength, or upper yield strength (suy), is eventually reached regardless of further strain rate decreases. It has been postulated that this phenomenon is part of a time-dependent behavior framework in which the yield locus shrinks with decreasing strain rate until some limiting surface, the static yield surface (SYS), is reached. Such a surface has been the basis for a number of constitutive models in which it represents the inviscid, or rate independent, behavior. The peak shear stress on the SYS corresponds to suy. Data from previous experimental programs are presented to show the existence of the surface and its role in undrained creep behavior. Undrained creep shear stress levels above suy lead to creep rupture on the failure envelope; stress levels below suy cause creep to the SYS, where the stress state apparently stabilizes without failure. The value of suy can be used in a number of analyses in creep susceptible soils, and the static yield condition can be used in the field to determine whether measured pore pressures are exceeding predicted nonrupture levels. A method is proposed for simple determination of the SYS using constant strain rate undrained shear tests. Key words : clays, consolidated-undrained tests, creep, rate effects, rheology, shear strength.

scholarly journals Characterization of peak shear strength of rough rock joints using limited displacement multi-stage direct shear (LDMDS) tests

2019 ◽  
Vol 92 ◽  
pp. 13011
Author(s):  
Mary MacLaughlin ◽  
Steve Berry ◽  
Michael Petro ◽  
Katherine Berry ◽  
Anders Bro
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Direct Shear Test ◽  
Shear Test ◽  
Rock Joints ◽  
Direct Shear ◽  
Peak Shear Strength ◽  
Single Specimen ◽  
Peak Shear Stress ◽  
Multistage Test

Current standard direct shear test methods for rock joints do not account for damage to the specimens' asperity profiles; tests require shearing of a single specimen to large displacements under successive normal stresses (the multistage test), or the use of similar specimens in multiple tests. Due to the inherently unique nature of rock joints and corresponding difficulty in obtaining specimens with identical or even similar geometries, multistage tests are more common. A major issue with the multistage test is that successive shearing of the specimen damages the surface asperities and changes its overall roughness profile, reducing the peak shear stress and consequently resulting in underestimation of the friction angle and overestimation of the joint shear intercept (cohesion). The limited displacement multistage direct shear (LDMDS) test method minimizes these testing imperfections by allowing shearing of a single specimen without extensive asperity damage, accomplished by immediately pausing shear displacement once peak shear stress has been reached, then proceeding to shear the specimen under the following normal stress value, and shearing into the post-peak region only after identifying multiple values of peak shear strength. The authors have validated the LDMDS procedure using cement replicates of rock joints, demonstrating that it yields more accurate strength parameters than the standard multistage direct shear test.

Effects of root tensile force and diameter distribution variability on root reinforcement in the Swiss and Italian Alps

2014 ◽  
Vol 44 (11) ◽  
pp. 1426-1440 ◽  
Author(s):  
C. Vergani ◽  
M. Schwarz ◽  
D. Cohen ◽  
J.J. Thormann ◽  
G.B. Bischetti
Keyword(s):  
Mechanical Properties ◽  
Root Distribution ◽  
Dominant Role ◽  
Tensile Force ◽  
Root Diameter ◽  
Diameter Distribution ◽  
Mountain Range ◽  
Data Set ◽  
Root Reinforcement ◽  
Wide Range

Root reinforcement is considered to be one of the most important factors contributing to the stability of vegetated hillslopes; however, its estimation is still challenging because of the spatial variability of root distribution and root mechanical properties. This work uses the root bundle model to assess the sensitivity of root-reinforcement estimation to the variability in both root mechanical properties and root distribution. We used a large data set of root tensile tests and root distributions of an important alpine species, Picea abies (L.) Karst., collected in a wide range of altitudinal and climatic ranges on both north and south sides of the alpine mountain range. The results demonstrate that the site-specific characterization of mechanical properties and root distribution is fundamental for the quantification of root reinforcement at the stand scale. Root diameter distribution plays a dominant role in influencing the root-reinforcement model’s output; however, in contrast with results from other works, differences in root diameter–force functions are significant and cannot be ignored. Model results also show that coarse roots contribute significantly more to the reinforcement of soil than fine roots, underlying the need of additional data for roots with diameters larger than 5 mm.

scholarly journals Chemical and physical interactions of regenerated cellulose yarns and isocyanate-based matrix systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bernhard Ungerer ◽  
Ulrich Müller ◽  
Antje Potthast ◽  
Enrique Herrero Acero ◽  
Stefan Veigel
Keyword(s):  
Mechanical Performance ◽  
Tensile Force ◽  
Tensile Modulus ◽  
Tensile Tests ◽  
Size Exclusion ◽  
Regenerated Cellulose ◽  
Hydrolytic Cleavage ◽  
Yarn Twist ◽  
Exclusion Chromatography ◽  
Physical And Chemical

AbstractIn the development of structural composites based on regenerated cellulose filaments, the physical and chemical interactions at the fibre-matrix interphase need to be fully understood. In the present study, continuous yarns and filaments of viscose (rayon) were treated with either polymeric diphenylmethane diisocyanate (pMDI) or a pMDI-based hardener for polyurethane resins. The effect of isocyanate treatment on mechanical yarn properties was evaluated in tensile tests. A significant decrease in tensile modulus, tensile force and elongation at break was found for treated samples. As revealed by size exclusion chromatography, isocyanate treatment resulted in a significantly reduced molecular weight of cellulose, presumably owing to hydrolytic cleavage caused by hydrochloric acid occurring as an impurity in pMDI. Yarn twist, fibre moisture content and, most significantly, the chemical composition of the isocyanate matrix were identified as critical process parameters strongly affecting the extent of reduction in mechanical performance. To cope with the problem of degradative reactions an additional step using calcium carbonate to trap hydrogen ions is proposed.

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