scholarly journals Shear Strength of Compacted Clays as Affected by Mineral Content and Wet-Dry Cycles

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Frederick Nai Charkley ◽  
Kunyong Zhang ◽  
Guoxiong Mei
Keyword(s):  
Shear Strength ◽  
Clay Minerals ◽  
Mineral Content ◽  
Strength Properties ◽  
High Plasticity ◽  
Wetting And Drying ◽  
Frictional Strength ◽  
Precautionary Measures ◽  
Weather Changes ◽  
Clay Slopes

The behaviors of high-plasticity clays depend largely on the clay mineral content. Recently, it has been observed that sudden slope failures of most clay slopes occur in regions pronounced with repeated rainfall and sunny climate. The reason for this is still unclear. Examining the effect of clay minerals and drastic weather changes on shear strength will be useful in predicting the performance of structures built in such soils and to take precautionary measures to improve the properties before failure. Therefore, a series of quick direct shearing tests were conducted on 11 artificial clay mixtures. The cohesion and frictional strength properties were determined and linked to the proportion of clay minerals and the number of wetting and drying cycles. The results show a significant reduction in shear strength after exposure to wetting and drying. Generally, montmorillonite-dominated mixtures were less susceptible to the changes in cohesion strength than kaolin-dominated mixtures, and the reduction in frictional strength was relatively insignificant.

Undrained shear strength properties of organic harbor mud at low consolidation stress levels

2011 ◽  
Vol 48 (3) ◽  
pp. 388-398 ◽  
Author(s):  
Benjamin Friedrich Schlue ◽  
Tobias Mörz ◽  
Stefan Kreiter
Keyword(s):  
Shear Strength ◽  
Large Scale ◽  
Strength Properties ◽  
Undrained Shear Strength ◽  
Ex Situ ◽  
High Plasticity ◽  
Compression Time ◽  
Stress Levels ◽  
Strong Surface ◽  
Undrained Shear

Dredging operations in European harbors for maintenance of navigable water depth produce vast amounts of harbor mud. Between 2005 and 2007, the second largest harbor construction project in Germany was designed as a pilot study, using dredged harbor mud as backfill material to avoid expensive deposition or ex situ treatment. During this project, strong surface deformations of the backfill highlighted the need for an improved assessment of undrained shear strength of naturally liquid harbor mud. The strength of harbor mud cannot be measured accurately under corresponding low in situ effective stress levels by standard laboratory tests. Therefore, a large-scale oedometer cell with a diameter of 22 cm was designed, providing the opportunity to perform vane shear measurements during consolidation. This study shows that East Harbor mud is a very sensitive, organogenic clay of extremely high plasticity, exhibiting very small undrained shear strength when compared with other cohesive soils. Both the peak and residual undrained shear strengths are shown to increase about 3%–4% per log-cycle increase in secondary compression time (days).

scholarly journals Modelling seasonal ratcheting and progressive failure in clay slopes: a validation

2020 ◽  
Vol 57 (9) ◽  
pp. 1265-1279
Author(s):  
H. Postill ◽  
N. Dixon ◽  
G. Fowmes ◽  
A. El-Hamalawi ◽  
W.A. Take
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Progressive Failure ◽  
High Plasticity ◽  
Wetting And Drying ◽  
Physical Measurements ◽  
Stress Cycles ◽  
High Plasticity Clay ◽  
Clay Slopes

Seasonal wetting and drying stress cycles can lead to long-term deterioration of high-plasticity clay slopes through the accumulation of outward and downward deformations leading to plastic strain accumulation, progressive failure, and first-time failures due to seasonal ratcheting. Using recent advances in hydromechanical coupling for the numerical modelling of unsaturated soil behaviour and development of nonlocal strain-softening regulatory models to reduce mesh dependency of localization problems, the mechanism of seasonal ratcheting has been replicated within a numerical model. Hydrogeological and mechanical behaviours of the numerical model have been compared and validated against physical measurements of seasonal ratcheting from centrifuge experimentation. Following validation, the mechanism of seasonal ratcheting was explored in a parametric study investigating the role of stiffness and long-term behaviour of repeated stress cycling extrapolated to failure. Material stiffness has a controlling influence on the rate of strength deterioration for these slopes; the stiffer the material, the smaller the seasonal movement and therefore the more gradual the accumulation of irrecoverable strains and material softening. The validation presented provides confidence that the numerical modelling approach developed can capture near-surface behaviour of high-plasticity, overconsolidated clay slopes subject to cyclic wetting and drying. The approach provides a tool to further investigate the effects of weather-driven stress cycles and the implication of climate change on high-plasticity clay infrastructure slopes.

scholarly journals Comparative Analysis of Shear Strength Parallel to Fiber of Different Local Bamboo Species in the Philippines

2021 ◽  
Vol 13 (15) ◽  
pp. 8164
Author(s):  
Brian E. Bautista ◽  
Lessandro E. O. Garciano ◽  
Luis F. Lopez
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Comparative Analysis ◽  
Strength Properties ◽  
The Philippines ◽  
Bamboo Species ◽  
Test Protocol ◽  
Future Design ◽  
Average Shear Strength ◽  
Bambusa Vulgaris

There are limited published studies related to the mechanical properties of bamboo species in the Philippines. In this study, the shear strength properties of some economically viable bamboo species in the Philippines were properly characterized based on 220 shear test results. The rationales of selecting this mechanical property are the following: (1) Shear strength, parallel to the fiber, has the highest variability among the mechanical properties; and (2) Shear is one of the governing forces on joint connections, and such connections are the points of failure on bamboo structures when subjected to extreme loading conditions. ISO 22157-1 (2017) test protocol for shear was used for all tests. The results showed that Bambusa blumeana has the highest average shear strength, followed by Gigantochloa apus, Dendrocalamus asper, Bambusa philippinensis, and Bambusa vulgaris. However, comparative analysis, using One-way ANOVA, showed that shear strength values among these bamboo species have significant differences statistically. A linear regression model is also established to estimate the shear strength of bamboo from the physical properties. Characteristic shear strength is also determined using ISO 12122-1 (2014) for future design reference.

scholarly journals Improved strength properties of LVL glued using PVAc adhesives with physical treatment-based Rubberwood (Hevea brasiliensis)

2020 ◽  
Vol 5 (1) ◽  
pp. 711-725
Author(s):  
Sutrisno ◽  
Eka Mulya Alamsyah ◽  
Ginanjar Gumilar ◽  
Takashi Tanaka ◽  
Masaaki Yamada
Keyword(s):  
Shear Strength ◽  
Hevea Brasiliensis ◽  
Formaldehyde Emission ◽  
Strength Properties ◽  
Modulus Of Rupture ◽  
Horizontal Shear ◽  
Physical Treatment ◽  
Cold Pressing ◽  
Laminated Veneer Lumber ◽  
Pressing Time

AbstractThe properties of the laminated veneer lumber (LVL) composed of the boiled veneer of Rubberwood (Hevea brasiliensis) using polyvinyl acetate (PVAc) adhesives in various cold-pressing time and various conditioned time with loaded and unloaded were studied. Five-ply LVL was produced by boiling veneer at 100°C for 90 min as pretreatment and cold-pressing time at 12 kgf cm−2 for 1.5, 6, 18, and 24 h then conditioned at 20°C and 65% relative humidity (RH) with loaded (12 kgf cm−2) and unloaded for 7 days as physical treatment. Especially for the delamination test, the specimens were immersed at 70 ± 3°C for 2 h and dried in the oven at 60 ± 3°C for 24 h; then, the specimens were solidified at room temperature (20°C and 65% RH) with loaded (12 kgf cm−2) and unloaded for 7, 10, 12, and 14 days. To determine the performance of LVL, the density, moisture content (MC), delamination, modulus of elasticity (MOE), modulus of rupture (MOR), horizontal shear strength, and formaldehyde emission tests were conducted according to the Japanese Agricultural Standard (JAS 2008) for structural LVL. The MOE and MOR values were significantly influenced by the physical treatment, however, neither to horizontal shear strength nor to formaldehyde emission. The best performance of LVL has resulted from unloaded LVL with cold-pressed time for 18 h; the MOE and MOR values were 9,345.05 ± 141.61 N mm−2 and 80.67 ± 1.77 N mm−2, respectively. The best value of the horizontal shear strength was obtained from the LVL with 18 h cold-pressing time and conditioned with loaded (13.10 ± 1.47 N mm−2) and unloaded (12.23 ± 1.36 N mm−2). The percentage of delamination values decreased with an increase in the cold-pressing time and conditioning time. The lowest value of delamination (19.06%) was obtained from the LVL with 24 h cold-pressing time and conditioned with loaded for 14 days. Except the delamination test, all other properties fulfilled the JAS.

Shear strength properties of plain and spirally profiled cable bolts

2015 ◽  
Vol 52 (10) ◽  
pp. 1490-1495 ◽  
Author(s):  
Naj Aziz ◽  
Ali Mirzaghorbanali ◽  
Jan Nemcik ◽  
Kay Heemann ◽  
Stefan Mayer
Keyword(s):  
Shear Strength ◽  
Testing Machine ◽  
Peak Load ◽  
Strength Properties ◽  
Shear Displacement ◽  
Vertical Shear ◽  
Cross Sectional ◽  
Cable Bolts ◽  
Strength Capacity ◽  
Cable Bolt

An experimental investigation into the performance of two 22 mm diameter, 60 t tensile strength capacity Hilti cable bolts in shear was conducted using the double-shear testing apparatus at the laboratory of the School of Civil, Mining and Environmental Engineering, Faculty of Engineering and Information Sciences, University of Wollongong. The tested cable bolts were (i) Hilti 19 wire HTT-UXG plain strand and (ii) Hilti 19 wire HTT-IXG spirally profiled (smaller cross-sectional area than the plain one) cable bolt, with indentation only on the surface of the outer strands. These cable bolts are of sealed wire construction type, consisting of an outer 5.5 mm diameter wire layer overlying the middle 3 mm diameter wire strands. Both layers are wrapped around a single solid 7 mm diameter strand wire core. The double-shearing test was carried out in 40 MPa concrete blocks, contained in concrete moulds. Cable bolts were encapsulated in concrete using Orica FB400 pumpable grout. Prior to encapsulation, each cable bolt was pre-tensioned initially to 50 kN axial force. A 500 t capacity servocontrolled compression testing machine was used for both tests, and during each test the vertical shear displacement was limited to 70 mm of travel. The rate of vertical shear displacement was maintained constant at 1 mm/min. The maximum shear load achieved for the plain strand cable was 1024 kN, while the spiral cable peak load was 904 kN, before the cable bolt wires began to individually snap, leading to the cable bolt break-up into two sections. It is apparent that spiral profiles of the outer wires weaken both the tensile and shearing strength. Finally, another set of tests was undertaken using the British Standard single-shear approach, producing lower shear strength values.

Fundamental Shear-Strength Properties of the Lilla Edet Clay

Géotechnique ◽  
1960 ◽  
Vol 10 (3) ◽  
pp. 101-109 ◽  
Author(s):  
Laurits Bjerrum ◽  
Tien-Hsing Wu
Keyword(s):  
Shear Strength ◽  
Strength Properties

scholarly journals Stabilization of Algerian Clayey Soils with Natural Pozzolana and Lime

2017 ◽  
Author(s):  
Khelifa Harichane ◽  
Mohamed Ghrici ◽  
Said Kenai
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Plasticity Index ◽  
Engineering Properties ◽  
High Plasticity ◽  
Expansive Clay ◽  
Clayey Soils ◽  
Natural Pozzolana

Cohesive soils with a high plasticity index present difficulties in construction operations because they usually contain expansive clay minerals. However, the engineering properties of soils can be improved by different techniques. The aim of this paper is to study the effect of using lime, natural pozzolana or a combination of both lime and natural pozzolana on plasticity, compaction and shear strength of two clayey soils classified as CH and CL according to the unified soil classification system (USCS). The obtained results indicated that for CH class clay soil, the plasticity index decreased significantly for samples stabilized with lime. On the other hand, for the soil classified as CL class clay, a high decrease in the plasticity index value was observed for samples stabilized with natural pozzolana compared to those stabilized with lime. Also, both the cohesion and internal friction angle in lime added samples were demonstrated to increase with time. The combination of lime and natural pozzolana exhibits a significant effect on the enhancement of both the cohesion and  internal friction angle at later stages. The lime-natural pozzolana combination appears to produce higher shear strength parameters than lime or natural pozzolana used alone.

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