scholarly journals Effects of Groove Feature on Shear Behavior of Steel-Sand Interface

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Jukun Guo ◽  
Xiaowei Wang ◽  
Shengyou Lei ◽  
Rui Wang ◽  
Hailei Kou ◽  
...  
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Friction Angle ◽  
Groove Width ◽  
Hyperbolic Model ◽  
Shear Direction ◽  
Intersection Angle ◽  
Interface Shear ◽  
Interface Friction ◽  
Peak Shear Stress

Surface groove morphology of structure and particle distribution of soil had a significant effect on the surface friction of structure. In order to investigate the interface shear stress-shear displacement curves, interface model and interface shear strength index when normal stress, groove width, and groove angle change, the interface shear tests of standard sand with steel plates are performed using an improved direct shear apparatus. Test results indicate that the peak shear stress increases with normal stress and the intersection angle between groove direction and shear direction. When the angle increases by 45°, the peak shear stress increases range from 4% to 13%. The peak shear stress increases with groove width, for every 1 mm increase in groove width, and the increasing extent of peak shear stress ranges from 4% to 22%, 3% to 13%, and 1% to 6%, respectively. When the groove angle is 45° and 90°, the increasing extent of peak shear stress decreases with groove width, but when the groove angle is 0°, the decrease regularity of peak shear stress increasing extent is not obvious. The hyperbolic model and Gompertz-C model are used to study the shear stress-shear displacement curves of sand-steel interface. The ratio of the interface peak shear stress of the hyperbolic model and Gompertz-C model to that of the shear test ranges from 0.90 to 1.03 and 0.88 to 0.98, respectively. The interface friction angle at the sand-steel interface ranges from 22° to 29°, and the friction angle of the rough interface is larger than that of the smooth interface. The interface friction angle increases with the intersection angle between the groove direction and the shear direction, the largest at 90°, the second at 45°, and the smallest at 0°. Under the same groove angle, the interface friction angle increases with the groove width, for every 1 mm increase in groove width, and the increasing extent of interface friction angle ranges from 4% to 15%, 4% to 7%, and 2% to 3%, respectively. The increasing extent of interface friction angle decreases with groove width, and this change rule is more obvious at the groove angle of 45° and 90° than at 0°.

scholarly journals Effects of Relative Roughness and Particle Size on the Interface Behavior of Concrete Suction Caisson Foundation for Offshore Wind Turbines

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5866
Author(s):  
Wang-chun Zhang ◽  
Hao Jing ◽  
Hai-lei Kou
Keyword(s):  
Particle Size ◽  
Shear Stress ◽  
Shear Test ◽  
Friction Angle ◽  
Offshore Wind ◽  
Interface Behavior ◽  
Interface Shear ◽  
Interface Friction ◽  
Offshore Wind Turbines ◽  
Relative Roughness

The interface behavior between a caisson and the surrounding soil plays an important role in the installation of suction caissons as foundations for offshore wind turbines. A series of shear tests were carried out using a modified direct shear apparatus to study the interface shear behavior between sand and concrete. Sand samples with three particle size ranges (0.63–1.25 mm, 1.25–2.5 mm, 2.5–5.0 mm) and concrete plates with different relative roughness were used to explore the influence of the relative roughness parameter (Rn) and mean particle size (D50) on shear behavior. The responses from the pure sand shear test are also discussed for comparison. Test results show that the higher the relative roughness (Rn), the greater the maximum shear stress (τmax) appeared. The interface shear stress was weaker than that of the pure sand test. Furthermore, the interface friction angle (φ) of sand–concrete was closely related to the relative roughness of the concrete surface. Under the same conditions, the interface friction angle (φ) increased with relative roughness due to the effect of sand particles breakage and redistribution. By contrast, the effect of the mean particle size (D50) on the interface friction angle (φ) was less significant. However, for the pure sand shear test, the friction angle (φ′) obtained from the traditional shear test apparently increased with D50, indicating that the friction angle was more affected by D50 in the pure sand test than in the interface shear test.

Characterization of Shear Strength and Interface Friction of Organic Soil

2020 ◽  
Vol 857 ◽  
pp. 203-211
Author(s):  
Majid Hamed ◽  
Waleed S. Sidik ◽  
Hanifi Canakci ◽  
Fatih Celik ◽  
Romel N. Georgees
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Internal Friction ◽  
Moisture Content ◽  
Water Content ◽  
Friction Angle ◽  
Structural Materials ◽  
Organic Soil ◽  
Internal Friction Angle ◽  
Interface Friction

This study was undertaken to investigate some specific problems that limit a safe design and construction of structures on problematic soils. An experimental study was carried out to examine the influence of loading rate and moisture content on shear strength of organic soil. Influece of moisture content on interface friction between organic soil and structural materials was also attempted. A commonly used soil in Iraq was prepared at varying moisture contents of 39%, 57% and 75%. The experimental results showed that the increase in water content will decrease the shear stress and the internal friction angle. An increase of the shearing rate was found to decrease the shear stress and internal friction angle for all percetanges of water contents. Further, direct shear tests were carried out to detect the interface shear stress behavior between organic soil and structural materials. The results revealed that the increase in water content was shown to have significant negetavie effects on the interface internal friction and angle shear strength.

Cyclic behavior of gravel–steel interface under varying rotational shear paths

2020 ◽  
pp. 1-12 ◽  
Author(s):  
Zia ur Rehman ◽  
Ga Zhang
Keyword(s):  
Shear Stress ◽  
Soil Structure ◽  
Three Dimensional ◽  
Cyclic Behavior ◽  
Shear Direction ◽  
Cyclic Tests ◽  
Cyclic Shear ◽  
Peak Shear Stress ◽  
Shear Condition ◽  
Rotational Shear

Cyclic rotational behavior of a soil–structure interface is imperative for understanding the three-dimensional behavior; this requires testing the interface under systematically varying rotational shear paths. A series of cyclic tests were conducted on the gravel–steel interface along linear, elliptical, and circular shear paths by systematically varying the orthogonal amplitude shear displacement ratio. The resultant peak shear stress was observed to be independent of the shear direction and dependent on the shear path. The interface demonstrates a coupling response among the orthogonal shear directions during the rotational shear, which governs the three-dimensional shear mechanism. Owing to such coupling, during the cyclic shear, the unloading extent from the resultant peak loading state at different quarters of a shear cycle diminishes as the shear path changes toward a circle; this leads to the monotonous shear proceeding in a circular route with an insignificant change in the shear direction. Significant dilatancy is induced by rotational shear, which can be divided into irreversible and reversible components. The final compression of the irreversible dilatancy increases as the area under the rotational shear path increases. The reversible dilatancy diminishes as the shear path becomes a circle. The interface evenly demonstrates aeolotropy under the rotational shear condition.

Experimental Analysis on Shear Behavior of Sand-Concrete Interface

2012 ◽  
Vol 204-208 ◽  
pp. 893-898
Author(s):  
Chun Feng Zhao ◽  
Bao Lai Yu ◽  
Cheng Zhao
Keyword(s):  
Shear Stress ◽  
Friction Coefficient ◽  
Normal Stress ◽  
Maximum Shear Stress ◽  
Relative Displacement ◽  
Shear Behavior ◽  
Tangential Displacement ◽  
Interface Shear ◽  
Direct Shear Tests ◽  
Concrete Interface

In order to study the shear behavior of sand-concrete structure interface, shear stress and relative displacement curves were obtained through a series of direct shear tests, in the procedure of which the roughness of interfaces was quantified into 3 grades and the stress history can be achieved by loading the sand to an initial normal stress and then unloading to a normal stress to shear. Through analyzing the curves, several conclusions can be obtained as follows: Shear stress increases with the initial normal stress and roughness at the same tangential displacement. The initial shear modulus can be improved in case of the increase of initial normal stress and roughness. The friction coefficient can be obtained by fitting the curve of the maximum shear stress and normal stress corresponded to Mohr-Coulomb Criterion linearly. The friction coefficient of sand-concrete interface increases with roughness as well as its increase range.

scholarly journals Study on Failure Characteristics and Acoustic Emission Characteristics of Sandstone Under Variable Angle Shear

2021 ◽  
Author(s):  
Feng Luo ◽  
Peidong Xu ◽  
Yijun Guo ◽  
Yanglong Diao ◽  
Meng Li
Keyword(s):  
Shear Stress ◽  
Acoustic Emission ◽  
Normal Stress ◽  
Failure Process ◽  
Shear Angle ◽  
Shear Cracks ◽  
Failure Characteristics ◽  
Variable Angle ◽  
Secondary Cracks ◽  
Peak Shear Stress

Abstract To study the shear damage and failure characteristics of red sandstone under different normal stress conditions, the failure process of sandstone under three different shear angles (50°, 55°, 60°) were studied by using variable angle shear test device. The shear stress-deformation curves and failure characteristics of sandstone were obtained, and the relationships between shear cracks and acoustic emission impact times, amplitude, peak frequency were established. With the increase of shear angle, the normal stress, shear stress and peak shear stress decrease gradually. The development of micro-cracks in the shear plane appear more earlier. The high frequency signal decreases significantly, which may have a significant corresponding relationship with the rock friction and shear effect. The failure mode of rock changes from plasticity to brittleness. The amplitude changes are concave, and more acoustic emission energy is released at compaction stage and plastic(failure) stage. The rock spalling mainly occur in the penetrating area of main and secondary cracks surrounding the two ends of specimen. The spalling degree was obviously weakened with the increase of shear angle. The results have important guiding value for judging and predicting the instability mechanism of rock engineering.

Laboratory study of soil–nail interaction in loose, completely decomposed granite

2004 ◽  
Vol 41 (2) ◽  
pp. 274-286 ◽  
Author(s):  
S M Junaideen ◽  
L G Tham ◽  
K T Law ◽  
C F Lee ◽  
Z Q Yue
Keyword(s):  
Normal Stress ◽  
Large Scale ◽  
Sharp Decrease ◽  
Friction Angle ◽  
Interface Friction ◽  
Pullout Force ◽  
Soil Nail ◽  
Arching Effect ◽  
Interface Parameters ◽  
Loose Fill

The technique of soil nailing is seldom used in stabilizing loose fill slopes because there is a lack of understanding of the interaction behaviour of nails in loose fills. A large-scale laboratory apparatus has been built to study the soil–nail interaction in loose fill materials. Pullout tests were performed in a displacement-rate-controlled manner on steel bars embedded in loose, completely decomposed granitic soils. The load–displacement curves have distinct peak values followed by a sharp decrease in the pullout force. The test results also show that the normal stress acting on the nail changes because of the volume-change tendency and arching effect of the soil being sheared around the nail. The post-peak decrease in the pullout force is mainly due to the reduction in the normal stress caused by the arching effect of soil around the nail. The conventional method of analysis tends to give a low interface friction angle and high interface adhesion. The correct interface parameters can be determined by taking the changes in the normal stress acting on the nail into account.Key words: arching effect, interface friction angle, laboratory test, loose fill, pullout resistance, soil–nail interaction.

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.

scholarly journals Numerical Analysis of Shear and Particle Crushing Characteristics in Ring Shear System Using the PFC2D

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 229
Author(s):  
Sueng-Won Jeong ◽  
Kabuyaya Kighuta ◽  
Dong-Eun Lee ◽  
Sung-Sik Park
Keyword(s):  
Shear Stress ◽  
Numerical Analysis ◽  
Normal Stress ◽  
Numerical Results ◽  
Particle Flow Code ◽  
Shear Stresses ◽  
Particle Crushing ◽  
Ring Shear ◽  
Peak Shear Stress ◽  
Residual Shear Stress

The shear and particle crushing characteristics of the failure plane (or shear surface) in catastrophic mass movements are examined with a ring shear apparatus, which is generally employed owing to its suitability for large deformations. Based on results of previous experiments on waste materials from abandoned mine deposits, we employed a simple numerical model based on ring shear testing using the particle flow code (PFC2D). We examined drainage, normal stress, and shear velocity dependent shear characteristics of landslide materials. For shear velocities of 0.1 and 100 mm/s and normal stress (NS) of 25 kPa, the numerical results are in good agreement with those obtained from experimental results. The difference between the experimental and numerical results of the residual shear stress was approximately 0.4 kPa for NS equal to 25 kPa and 0.9 kPa for NS equal to 100 kPa for both drained and undrained condition. In addition, we examined particle crushing effect during shearing using the frictional work concept in PFC. We calculated the work done by friction at both peak and residual shear stresses, and then used the results as crushing criteria in the numerical analysis. The frictional work at peak and the residual shear stresses was ranged from 303 kPa·s to 2579 kPa·s for given drainage and normal stress conditions. These results showed that clump particles were partially crushed at peak shear stress, and further particle crushing with respect to the production of finer in shearing was recorded at residual shear stress at the shearing plane.

scholarly journals Dynamic modulus characteristics of saturated clays under variable confining pressure

2017 ◽  
Vol 54 (5) ◽  
pp. 729-735 ◽  
Author(s):  
Chuan Gu ◽  
Zhiqiang Gu ◽  
Yuanqiang Cai ◽  
Jun Wang ◽  
Daosheng Ling
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Hyperbolic Model ◽  
Cyclic Triaxial Tests ◽  
Cyclic Shear ◽  
Dynamic Loadings ◽  
Actual Field ◽  
Variable Confining Pressure

Dynamic loadings, induced by earthquakes and other causes, will lead to the cyclic variation of both shear stress and normal stress components on the soil elements. A series of cyclic triaxial tests with and without variable confining pressure were carried out to investigate the coupling effects of cyclic shear stress and cyclic normal stress on the normalized shear modulus, G/Gmax, characteristics of saturated clays. Results indicated that both the phase differences and ratios between the cyclic deviatoric stress and cyclic confining pressure exerted a constant and pronounced influence on the G/Gmax, indicating that the G/Gmax properties under combined loadings will be more representative of actual field conditions than from single-loading conditions. A modified hyperbolic model considering the effects of cyclic confining pressure was further proposed.

Effects of stress on failure behaviour of shallow-marine muds from the northern Gulf of Mexico

2018 ◽  
Vol 477 (1) ◽  
pp. 523-536 ◽  
Author(s):  
Brandon Dugan ◽  
Xin Zhao
Keyword(s):  
Shear Stress ◽  
Internal Friction ◽  
Gulf Of Mexico ◽  
Pore Pressure ◽  
Slope Failure ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Failure Behaviour ◽  
Northern Gulf Of Mexico ◽  
Peak Shear Stress

AbstractDirect simple shear experiments on mud samples from 0 to 15 mbsf (metres below seafloor) in the Ursa Basin (northern Gulf of Mexico) document that stress level impacts shear strength and pore pressure during failure. As burial depth increased (from 7.35 to 13.28 mbsf), cohesion decreased (from 12.3 to 6.5 kPa) and the internal friction angle increased (from 18° to 21°). For a specimen from 11.75 mbsf, an increase in maximum consolidation stress (from 45 to 179 kPa) resulted in an increase in the shear-induced pore pressure (from 29 to 150 kPa); however, the normalized peak shear stress decreased (from 0.37 to 0.25). Our results document that consolidation at shallow depths induces a positive feedback on pore-pressure genesis. For resedimented samples, which lack a stress history, cohesion was 3.6 kPa and the internal friction angle was 24°. As the maximum consolidation stress increased (from 40 to 254 kPa) on resedimented samples, the shear-induced pore pressure increased (from 22 to 203 kPa), whereas the normalized peak shear stress decreased (from 0.32 to 0.25). Our experiments showed that resedimented samples have similar strength and failure behaviour to intact samples. By constraining pore pressure, strength and initial stress state, we gain a better insight into slope-failure dynamics. Therefore, our experiments provide constraints on strength and shear-induced pore pressure at the onset of shallow failure that could be included in slope-failure and hazard models.

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