scholarly journals A New Rock Joint Generation Method and Its Verification in PFC2D

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Lielie Li ◽  
Mingli Xiao ◽  
Cai Tan
Keyword(s):  
Shear Stress ◽  
Rock Joint ◽  
Fracture Network ◽  
Jointed Rock ◽  
Normal Direction ◽  
Particle Flow Code ◽  
Direct Shear ◽  
Direct Shear Tests ◽  
Mechanical Behaviours ◽  
Asperity Degradation

The first part of this paper presents the major drawbacks of the traditional methods for generating joints in Particle Flow Code 2D (PFC2D). Violent oscillations in the postpeak shear stress and shear-induced dilation in the normal direction occur in specimens generated by directly removing bonds in joints and using the discrete fracture network (DFN) method. The specimens generated by the additional wall method can be used to simulate realistic shear mechanical properties in the direct shear test, but it is difficult to achieve a uniform initial stress distribution within the specimen due to the constraint of particle motion. The second part of this paper explores an improved method to generate realistic joints based on the particle grouping technique and the smooth joint model, and the validity of this method is verified by a set of numerical direct shear tests. The numerical results show that the proposed joint generation method can effectively eliminate the oscillation of the postpeak shear stress and shear-induced dilation in the normal direction. In addition, the mechanical behaviours of the rough jointed rock mass correspond well with the theoretical results obtained from Patton’s and Barton’s models. The proposed model can also simulate the asperity degradation of rough jointed rock masses.

An Improved Shear Stress Monitoring Method in Numerical Direct Shear Tests by Particle Flow Code

2019 ◽  
Vol 48 (6) ◽  
pp. 20180018 ◽  
Author(s):  
Yaofei Jiang ◽  
Liangqing Wang ◽  
Qiong Wu ◽  
Zihao Sun ◽  
Davide Elmo ◽  
...  
Keyword(s):  
Shear Stress ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Direct Shear ◽  
Stress Monitoring ◽  
Shear Tests ◽  
Monitoring Method ◽  
Direct Shear Tests

scholarly journals Research on the Strength Characteristics and Crack Propagation Law of Noncoplanar Nonthrough Jointed Rock Mass by PFC2D

2021 ◽  
Vol 2021 ◽  
pp. 1-28
Author(s):  
Qingzhi Chen ◽  
Yuanming Liu ◽  
Shilong Mei ◽  
Kai Cao ◽  
Bin Du ◽  
...  
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Strength Characteristics ◽  
Particle Flow Code ◽  
Direct Shear ◽  
Direct Shear Tests ◽  
Relief Angle ◽  
Propagation Law

In this study, five groups of numerical models with different conditions were established by using PFC2D (particle flow code) to simulate the direct shear tests of noncoplanar nonthrough jointed rock mass. It is proved that normal stress and shear rate, as well as the connectivity rate, relief angle, and inclination angle of joints, have significant influence on the strength characteristics, number of cracks, and the stress of the rock mass according to measurement taken at five different measurement circles in the rock mass. Moreover, it is determined that in the process of shearing, no matter which group of tests are conducted, the number of cracks in the rock mass caused by tension is far more than that caused by the shear action. In other words, the failure of rock mass with different planes and discontinuous joints is mainly caused by the tension in the process of the direct shear test.

scholarly journals Using Post-Harvest Waste to Improve Shearing Behaviour of Loess and Its Validation by Multiscale Direct Shear Tests

2019 ◽  
Vol 9 (23) ◽  
pp. 5206 ◽  
Author(s):  
Wen-Chieh Cheng ◽  
Zhong-Fei Xue ◽  
Lin Wang ◽  
Jian Xu
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Strain Hardening ◽  
Gradual Increase ◽  
Small Scale ◽  
Optimal Dosage ◽  
Direct Shear ◽  
Shear Tests ◽  
Post Harvest ◽  
Direct Shear Tests

Loess and PHW (post-harvest waste) are easily accessible in the Chinese Loess Plateau and have been widely applied to construction of residential houses that have been inhabited for decades under the effect of freeze-thaw cycles. Although many researchers have recognised that the addition of fibers to loess soil is effective in preventing soil erosion and stabilising slopes, a consensus on this claim has not been reached yet. This study investigates the shearing behaviour of the loess-PHW mixture using small-scale and large-scale direct shear (SSDS and LSDS) tests. Four typical shear stress versus horizontal displacement curves from the multiscale direct shear tests are recognised where one is featured with strain-softening shape and the other three with a strain-hardening shape. Two out of the three curves with strain-hardening shape show a gradual increase in the shear stress at additional and larger displacements, respectively, in which some factor starts to have an influence on the shearing behaviour. Comparisons of the shear strength measured in SSDS and LSDS are made, indicating that there are differences between SSDS and LSDS. The effect of PHW addition on shear strength is assessed in order to determine the optimal dosage. The improvement of shear strength is attributed to the effect of particle inter-locking, resulting from the addition of PHW to loess specimens, and takes effect as the water content surpassed a threshold, i.e., >14%, that facilitates particle rearrangement. Particle-box interaction behaviour is assessed at the same time, and the findings satisfactorily address the main cause of the gradual increase in shear stress following the curve inflection point. The improved shearing behaviour proves the ability of the loess-PHW mixture to resist the seepage force and consequently stratum erosion.

Waste Paper Application in Geotechnical Project

2012 ◽  
Vol 535-537 ◽  
pp. 2148-2153
Author(s):  
Amin Chegenizadeh ◽  
Hamid Nikraz
Keyword(s):  
Shear Stress ◽  
Kaolin Clay ◽  
Direct Shear ◽  
Reinforcement Effect ◽  
Embankment Dam ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Reinforcement Content ◽  
Strength Behavior ◽  
Clay Kaolin

Composite soils have been widely used in civil engineering applications, especially in slopes, embankment dam and landfills. This paper aims to investigate effect of fiber inclusion on shear stress of composite soil (i.e. clay composite). A series of laboratory direct shear tests carried out to evaluate paper reinforcement effect on strength behavior of composite clay. Kaolin clay was selected as soil part of the composite and paper was used as reinforcement. The paper reinforcement parameters differed from one test to another, the paper length was changed from 10 mm to 30 mm and paper content were varied from 5% to 15%. Normal stress kept constant at 150 kPa. For each test, stress_ displacement graph derived and the results were compared. The results proved that inclusion of paper reinforcement affected strength behaviour of clay composite so that increasing in paper reinforcement content and length caused increasing in shear stress.

scholarly journals Pile Side Resistance in Sands for the Unloading Effect and Modulus Degradation

2019 ◽  
Vol 69 (334) ◽  
pp. 185 ◽  
Author(s):  
C. F. Zhao ◽  
Y. Wu ◽  
C. Zhao ◽  
Q. Z. Zhang ◽  
F. M. Liu ◽  
...  
Keyword(s):  
Shear Stress ◽  
Maximum Amount ◽  
Interface Roughness ◽  
Direct Shear ◽  
Shear Tests ◽  
Interface Shear ◽  
Direct Shear Tests ◽  
Side Resistance ◽  
Unloading Effect ◽  
Concrete Interface

A total of 36 groups of sand-concrete interface loading and unloading direct shear tests were used to analyze the mechanical properties of the pile side-soil interface. The test results show that the interface residual shear stress for the same applied normal stress tends to be constant for the rough sand-concrete interface. The initial shear modulus and peak shear stress of the interface both decrease with the degree of unloading and increase with the interface roughness. The maximum amount of interface shear dilatancy increases with the degree of unloading, and the maximum amount of interface shear shrinkage decreases with unloading for the same interface roughness. A pile side resistance-displacement model is established using the shear displacement method. The proposed function considers both the radial unloading effect and modulus degradation of soil around the pile. The effect of radial unloading and interface roughness on the degradation of the equivalent shear modulus is analyzed using a single fitting parameter b. Good agreement of the proposed model is confirmed by applying the direct shear tests of the 36 groups.

Composite Clayey Sand and Short Fiber

2011 ◽  
Vol 383-390 ◽  
pp. 2764-2769 ◽  
Author(s):  
Amin Chegenizadeh ◽  
Hamid Nikraz
Keyword(s):  
Shear Stress ◽  
Fiber Length ◽  
Short Fiber ◽  
Fiber Content ◽  
Direct Shear ◽  
Embankment Dam ◽  
Shear Tests ◽  
Clayey Sand ◽  
Direct Shear Tests ◽  
Strength Behavior

Composite soils have been widely used in civil engineering applications, especially in slopes, embankment dam and landfills. This paper aims to investigate effect of fiber inclusion on shear stress of composite soil (i.e. sand composite). A series of laboratory direct shear tests carried out to evaluate fiber effect on strength behavior of composite sand. Clayey sand was selected as soil part of the composite and glass fiber was used as reinforcement. The fiber parameters differed from one test to another, as fiber length were changed from 10 mm to 35 mm and fiber content were varied from 0.6% and 3%.Normal stress kept constant at 150 kpa. For each test, stress_ displacement graph derived and the results were compared. The results proved that inclusion of fiber affected strength behaviour of sand composite so that increasing in fiber content and length caused increasing in shear stress.

Evaluation of the anisotropy and directionality of a jointed rock mass under numerical direct shear tests

2017 ◽  
Vol 225 ◽  
pp. 29-41 ◽  
Author(s):  
Peitao Wang ◽  
Fenhua Ren ◽  
Shengjun Miao ◽  
Meifeng Cai ◽  
Tianhong Yang
Keyword(s):  
Rock Mass ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests

Evolution Process of Natural Rock Joint Roughness during Direct Shear Tests

2017 ◽  
Vol 17 (5) ◽  
Author(s):  
Yunfeng Ge ◽  
Huiming Tang ◽  
M. A. M. Ez Eldin ◽  
Liangqing Wang ◽  
Qiong Wu ◽  
...  
Keyword(s):  
Rock Joint ◽  
Evolution Process ◽  
Direct Shear ◽  
Shear Tests ◽  
Joint Roughness ◽  
Direct Shear Tests ◽  
Natural Rock

Investigations on Direct Shear Tests and PFC2D Numerical Simulations of Rock-Like Materials with a Hole and Prefabricated Cracks

2014 ◽  
Vol 627 ◽  
pp. 477-480 ◽  
Author(s):  
Ping Cao ◽  
Yong Fang Zhong ◽  
Ya Jing Li ◽  
Jie Liu
Keyword(s):  
Simulation Models ◽  
Experimental Tests ◽  
Two Dimensions ◽  
Surrounding Rock ◽  
Particle Flow Code ◽  
Mechanical Parameters ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Inclination Angles

Direct shear tests conducted on the samples containing a central hole and prefabricated cracks are performed to make an analysis on the effects of the inclination angle, the number of prefabricated cracks and the normal stress on shearing characteristics. And the particle flow code in two dimensions (PFC2D) based on discrete element is applied to carry on simulations on this tests. The micro mechanical parameters of the simulation models are determined by the calibration processes conducted on the shear stress-stain numerical curves of intact samples and the samples containing a pre-existing hole in both experimental tests and simulation tests. And then the micro mechanical parameters obtained above are applied in the simulation models containing prefabricated cracks with varying inclination angles and numbers. Based on the comparisons conducted on simulation curves and experimental curves, investigations of the initiation, propagation and coalescence mechanisms of the prefabricated cracks in both macro and micro scales are performed. And the results may shed lights on the failure mechanism of the surrounding rock involving holes and cracks.

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