scholarly journals Effect of normal stress and relative compaction on secant friction angle of sands

2014 ◽  
Vol 38 ◽  
pp. 382-391 ◽  
Author(s):  
Seyed Mohammad Reza HOSSEINI ◽  
Mehrab JESMANI
Keyword(s):  
Normal Stress ◽  
Friction Angle ◽  
Relative Compaction

scholarly journals Shear Mechanical Behaviours and Multistrength Parameter Characteristics of Fault Gouge

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Han Bao ◽  
Qun Qi ◽  
Hengxing Lan ◽  
Changgen Yan ◽  
Wei Xu ◽  
...  
Keyword(s):  
Water Content ◽  
Normal Stress ◽  
Clay Minerals ◽  
Residual Strength ◽  
Failure Modes ◽  
Friction Angle ◽  
Strength Properties ◽  
Fault Gouge ◽  
Normal Stresses ◽  
Fault Gouges

Fault gouge has special mechanical properties and remarkable engineering effects. Using a ring shear test, the strength properties of the differently colored remolded fault gouges of the Shendaogou Fault in Yan’an were studied by changing moisture contents and normal stresses. Chlorite and illite are the main clay minerals in fault gouges; differences in mineral composition make fault gouges appear in different colors. Besides clay minerals, the dried fault gouges disintegration in water is also due to the transformation of gypsum. The gradation of green fault gouge and multicolor fault gouge is better than that of the red fault gouge, while the fault gouges’ strain softening properties become weaker as the coarse grain content increases. Affected by water content and normal stress, the shear planes can be divided into three failure modes: peeling failure, grooved failure, and sliding failure. With the increase of water content, there will be a significant weakening on cohesion and friction angle. A new parameter, the “Normal Stress Threshold (NST),” is introduced as a critical value for the emergence of the strain hardening phenomenon, and the NSTs of different fault gouges are significantly different. The functions obtained from the relation of residual strength, peak strength, and normal stress can be used to calculate shear strength parameters under any normal stresses. In addition, the residual strength of fault gouge is obviously different from clay and loess, which can be qualitatively explained by clay particle contents.

An Analysis on Influencing Factors of Interlayer Separation of Complex Roof in Deep Coal Mining

2010 ◽  
Vol 146-147 ◽  
pp. 976-979
Author(s):  
De Yi Wu ◽  
Ai Lang Wang ◽  
Hua Qiang Liang
Keyword(s):  
Numerical Simulation ◽  
Normal Stress ◽  
Coal Mining ◽  
Influencing Factors ◽  
Friction Angle ◽  
Rock Stress ◽  
Roof Collapse ◽  
Tunnel Width ◽  
Original Rock

In order to control construction face instability of complex roof and predict roof collapse in deep coal mining, by numerical simulation, distribution of normal stress and interlayer separation of construction surface were calculated and influencing factors on separation of construction surface were analyzed in different conditions. The conclusions were drawn that original rock stress, rock characters, rock thickness and tunnel width had obvious influence and cohesion and friction angle of construction surface had little influence on separation of construction surface.

Experimental Research on Strength Characteristics of Bulky Rock Material with Different Coarse Grain Content in Waste Pile of Mine

2012 ◽  
Vol 170-173 ◽  
pp. 295-300 ◽  
Author(s):  
Jun Du ◽  
Ke Peng Hou ◽  
Wei Liang
Keyword(s):  
Shear Modulus ◽  
Normal Stress ◽  
Friction Angle ◽  
Rock Material ◽  
Shear Displacement ◽  
Coarse Grain ◽  
Horizontal Loading ◽  
Shear Process ◽  
Main Basis ◽  
Rock And Soil

Bulky rock material of waste pile was composed of discarded rock and soil which was blasted and stripped from stope. It was characterized by dispersibility, complexity and variability. Shear strength index of bulky rock material was the main basis for analyzing slope stability of the waste pile. After the study on bulky rock material with different coarse grain content by indoor direct shear test, the results indicated that there was no obvious peak strength during the shear process, and variation of the shear displacement was slight in initial horizontal loading stage. Horizontal loading increased slowly and shear displacement had obvious change when shear displacement exceeded 5mm. Under the same normal stress, shear modulus G0.01 increased with the increase of coarse grain content when shear strain of specimen is 1/100. Shear modulus G0.01 of the specimen with same coarse grain content increased with the increase of normal stress, varying sensitive of G0.01 reduced when coarse grain content was larger. When the specimens with same coarse grain content were under failure, the shear modulus Gfailure was smaller than G0.01. Cohesive force c of the bulky rock material began to increase and then decrease with the increase of coarse grain content, and reached its maximum of 31.25KPa when the coarse grain content was 70%, internal friction angle increased with the increase of coarse grain content.

Moisture Dependent Dynamic Flow Properties of Coconut Flours

2016 ◽  
Vol 12 (6) ◽  
pp. 577-585 ◽  
Author(s):  
M. R. Manikantan ◽  
R. P. Kingsly Ambrose ◽  
Sajid Alavi
Keyword(s):  
Moisture Content ◽  
Normal Stress ◽  
Flow Characteristics ◽  
Coconut Oil ◽  
Friction Angle ◽  
Wall Friction ◽  
Flow Properties ◽  
Dynamic Flow ◽  
Virgin Coconut Oil ◽  
Air Velocity

Abstract The dynamic flow properties of two important coproducts of virgin coconut oil (VCO) i. e. coconut milk residue flour (MRF) and VCO cake flour (CF) were studied. The basic flowability energy of CF was higher than MRF and increased with moisture content. The change in compressibility and shear stress, with applied normal stress and moisture content, indicated that these powders are highly cohesive. For both flours, the energy required to make the powder flow increased with moisture at all experimental air velocity. Moisture did not significantly influence the cohesion and unconfined yield strength of MRF, whereas for CF there was significant effect due to the presence of moisture. The wall friction angle of both the flours increased significantly with moisture and decreased with applied normal stress. The results from this study indicated that, both CF and MRF at around 4.00 % moisture content had better flow characteristics than at higher moisture levels.

Numerical Simulation for Shear Characteristics of Rock-Mass Structural Plane

2013 ◽  
Vol 734-737 ◽  
pp. 574-578
Author(s):  
Bao Yuan Yuan ◽  
Qi Wang ◽  
Hai Feng Lu
Keyword(s):  
Shear Strength ◽  
Normal Stress ◽  
Friction Angle ◽  
Normal Displacement ◽  
Displacement Curve ◽  
Peak Shear Strength ◽  
Structural Plane ◽  
Linear Feature ◽  
Stress And Deformation ◽  
The Stability

The characteristics of structural plane are very important to the stability of rock mass.In this paper,the stress and deformation characteristics of structural plane under direct shear conditions are analyzed based on FLAC3D code.And the influence of structural plane inhomogeneity to shear test was discussed.The results obtained in this paper indicate that, with the increase of normal stress, the shear strength of structural plane is constantly increasing,and the tow of them presents linear feature significantly. The normal displacement and shear displacement increase with the rise of the normal stress too. The peak shear strength increases gradually on the condition of uneven friction angle in the interface. This situation changes smaller when the discrete degree of friction angle is small. The peak shear strength increases significantly when the discrete degree of friction angle is big,and the stress-displacement curve exhibits a nonlinear characteristics before yield.

scholarly journals The effects of grain size and different multi-stage shearing techniques on shear strength along rock discontinuities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Alina Vattai ◽  
Nikoletta Rozgonyi-Boissinot
Keyword(s):  
Grain Size ◽  
Shear Strength ◽  
Normal Stress ◽  
Friction Angle ◽  
Coarse Grained ◽  
Roughness Coefficient ◽  
Peak Friction Angle ◽  
Grain Sizes ◽  
Multi Stage ◽  
Study Laboratory

AbstractThe effects of grain size and different multi-stage shearing techniques on shear strength along discontinuities were analyzed in this study. Laboratory direct shear tests were carried out on plaster mortar with maximum grain sizes of 0.5 mm and 1.0 mm. All specimen surfaces were essentially similar, copied from the same natural, Hungarian coarse-grained sandstone joint with a low joint roughness coefficient (JRC = 8). Tests within two different normal stress ranges (σn = 0.25–0.5 and 0.5–1.5 MPa) were performed simultaneously. Specimens tested using the technique involving modified shearing with repositioning were sheared three times while being subjected to the same degree of normal stress (shearing sequence n = 1, 2, 3) and those with multi-stage technique without repositioning were subjected to shearing once at three different degrees of normal stress. The changing values of the peak friction angle calculated from the resulting peak shear strength-normal stress data pairs (τp − σn) were examined. Failure curves were estimated using linear regression, according to the Mohr–Coulomb failure criterion. The differences between the various peak friction angles obtained from experiments in which different multi-stage shearing techniques were used tend to increase in significance with the increasing number of shearing sequences. Peak friction angle values vary according to grain size of the material, though further investigations using more grain sizes are required to establish the extent of the effect on shear strength along discontinuities.

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 Analysis of a Methodology for Torsional Test under Normal Stress and Shear Performance for Asphalt Mixtures

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Jun Xie ◽  
Yiqun Zhan ◽  
Yifan Wang
Keyword(s):  
Shear Strength ◽  
Normal Stress ◽  
Shear Test ◽  
Stress Condition ◽  
Asphalt Mixture ◽  
Friction Angle ◽  
Asphalt Mixtures ◽  
Test Method ◽  
Shear Performance ◽  
Torsional Test

Insufficient shear performance in an asphalt mixture is a primary reason for rutting deformation and pavement surface longitudinal cracking. Thus, it is important to choose a suitable shear test method to evaluate shear performance in an asphalt mixture. Current testing methods mainly evaluate the bonding strength between asphalt layers, and the current shear test method for an asphalt mixture is disadvantaged by high equipment cost and complicated procedures. Our study proposes a torsional test method under normal stress condition, and evaluation was done for four types of asphalt mixture under different temperature conditions. Through the mechanical analysis, the calculation formulas for shear strength and shear parameters (cohesion and internal friction angle) for the torsional test under a normal stress condition were obtained. Testing results were also obtained for shear strength, shear modulus, and cohesion and internal friction angle of the asphalt mixtures. Experimental testing indicated that the method was able to provide repeatable results for the shear resistance of asphalt mixtures at different temperatures and also reflected the difference in shear performance of the various asphalt mixtures and the influence of temperature on shear performance. The failure mode of the specimen was the appearance of an oblique crack of about 45° from the vertical axis after the specimen was destroyed, which accorded with shear failure characteristics. A shear fatigue model was obtained considering different shear stress levels. The torsional test method under normal stress formed a compression-shear action on the specimen by applying torque and normal stress and was used to evaluate the shear performance of the asphalt mixtures.

scholarly journals Influence of shearing rate on the residual strength characteristic of three landslides soils in loess area

2018 ◽  
Author(s):  
Baoqin Lian ◽  
Jianbing  Peng ◽  
Xingang Wang ◽  
Qiangbing Huang
Keyword(s):  
Normal Stress ◽  
Friction Angle ◽  
Slip Zone ◽  
Residual Shear Strength ◽  
Friction Coefficients ◽  
Series Ring ◽  
Loess Area ◽  
Shearing Rate ◽  
The Difference ◽  
Slip Zone Soils

Abstract. In order to investigate the effect of the shearing rate on the residual shear strength of slip zone soils, a series ring shear tests were carried out on slip zone soils from three landslides in loess area at the two shearing rates (0.1 mm/min and 1 mm/min). The slip zone soil specimens used in present study were from the northwest of China. Results indicated that the shear displacement to achieve the residual stage for specimens with higher shearing rate is greater than that of the lower rate. Relationship between the residual friction coefficients and normal stress shows that the residual friction coefficients for all specimens under the lower normal stress were greater than that under the higher normal stress at two shearing rate. Furthermore, the difference in the residual friction angle фr at the two shearing rates, фr (1) − фr (0.1), under each normal stress level were either positive or negative values, with the maximum absolute value of фr (1) − фr (0.1) reach up to 2.218°. However, the difference фr (1) − фr (0.1) under all normal stresses was negative, which indicates that the residual shear parameters reduced with the increasing of the shearing rate in loess area.

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