scholarly journals Numerical Investigation on the Evolution of Mechanical Properties of Rock Affected by Micro-Parameters

2020 ◽  
Vol 10 (14) ◽  
pp. 4957
Author(s):  
Haoyu Rong ◽  
Guichen Li ◽  
Dongxu Liang ◽  
Changlun Sun ◽  
Suhui Zhang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Stress Ratio ◽  
Three Dimensional ◽  
Particle Flow Code ◽  
Parameter Calibration ◽  
Failure Characteristics ◽  
Failure Patterns ◽  
Response Characteristics ◽  
Bond Model

Investigating the micro-parameters of rock is vital for understanding the macro-properties of rock, such as the uniaxial compressive strength (UCS), Young’s modulus, failure patterns, etc. In this paper, based on the experimental results of rock material, a parallel-bond model in three-dimensional particle flow code (PFC3D) was applied to investigate the effects of the joint action of bond stiffness ratio and bond stress ratio on macro-properties of rock. The uniaxial compressive strength, stress–strain relationships, and failure characteristics, as well as underlying compression and failure mechanisms, in the process of parameter calibration, were systematically studied. The results indicated that the interaction of several micro-parameters would obviously change the response characteristics of the macro-properties of the model. The mechanism of the effects of various micro-parameters on the macro-properties of the model was further revealed. The change of the micro-parameters would change the strength and stress state of the bond between particles. The research results could promote the understanding of the failure mechanism of rock and improve the efficiency of micro-parameter calibration and the accuracy of calibration results.

Study on Damage of Rock Samples with Single-Hole under Uniaxial Compression Condition

2012 ◽  
Vol 446-449 ◽  
pp. 3810-3813
Author(s):  
Bing Xie ◽  
Huai Feng Tong ◽  
Xiang Xia
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Compression Tests ◽  
Rock Samples ◽  
Single Hole ◽  
Compression Condition

Numerical specimens with single-hole is established by particle flow code PFC2D and uniaxial compression tests are conducted. Studies have shown that uniaxial compressive strength of specimen with single hole is less than complete specimens. As the holes move to the end of specimen, the uniaxial compressive strength first increases and then tends to decrease.

scholarly journals Thermally induced deterioration behaviour of two dolomitic marbles under heating–cooling cycles

2018 ◽  
Vol 5 (10) ◽  
pp. 180779 ◽  
Author(s):  
Zhong-jian Zhang ◽  
Jian-bin Liu ◽  
Biao Li ◽  
Xi-guang Yang
Keyword(s):  
Weight Loss ◽  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Three Dimensional ◽  
Elastic Wave Velocity ◽  
Experimental Investigations ◽  
Seasonal Temperature ◽  
Beijing City ◽  
Dolomitic Marble ◽  
Thermally Induced

Thermally induced deterioration behaviour can cause severe weathering in marbles. Most previous studies focus on the deterioration behaviour of calcitic marbles. Relevant studies of dolomitic marbles are generally carried out under a ‘high temperature and low cycling times' condition. Little attention is focused on the deterioration behaviour in dolomitic marbles when they are subjected to a large quantity of heating–cooling cycles under a ‘low temperature and high cycling times’ condition. This paper presents experimental investigations on the thermally induced deterioration behaviour of two Beijing dolomitic marbles (Qingbaishi Marble (QM) and Hanbaiyu Marble (HM)) under heating–cooling cycles up to 1000 cycling times. The applied temperature range is from –20°C to 60°C which is to simulate the seasonal temperature variations in Beijing city, China. Related properties such as weight loss, three-dimensional microtopography, elastic wave velocity and uniaxial compressive strength were measured at certain cycles. The results indicate that thermally induced deterioration behaviour will result in a continuous weight loss in dolomitic marble samples. Mechanical properties of those two marbles are strongly affected by heating and cooling treatments, which were reflected by the reductions of dynamic Young's modulus and uniaxial compressive strength with an increase of thermal cycles. Compared with QM, HM displays a higher level of thermally induced deterioration which should be due to the abundance of quartz mineral.

Influence of Loading Rate on Uniaxial Compression Test of Rock Specimen with Random Joints

2011 ◽  
Vol 396-398 ◽  
pp. 217-220
Author(s):  
Bing Xie ◽  
Jin Jun Guo ◽  
Xiang Xia
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Compression Test ◽  
Rock Specimen ◽  
Loading Rate ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Uniaxial Compression Test ◽  
Compression Tests

Numerical specimens with ramdom joints is established by particle flow code PFC2D and uniaxial compression tests are conducted under three different loading rate. Studies have shown that strength of uniaxial compression are all increased with the loading rate no matter what specimen is complete or with random joints. The sensitivity of changes of uniaxial compressive strength of specimen with random joints decreases with increasing of the loading rate.

scholarly journals Simulation Study on Strength and Failure Characteristics for Granite with a Set of Cross-Joints of Different Lengths

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Dawei Yin ◽  
Shaojie Chen ◽  
Xingquan Liu ◽  
Hongfa Ma
Keyword(s):  
Compressive Strength ◽  
Crack Propagation ◽  
Uniaxial Compressive Strength ◽  
Shear Failure ◽  
Tensile Failure ◽  
Failure Characteristics ◽  
Included Angle ◽  
Loading Direction ◽  
Joint Plane ◽  
Plane Direction

The strength and failure characteristics for granite specimen with a set of cross-joints of different lengths were studied using PFC2D software. The results show that when the included angle of α between the main joint and loading direction is 30° or 45°, no matter what the included angle of β between main and secondary joints is, the main joint controls crack propagation and failure of granite specimen, which occurs the shear failure propagating from main joint tips, and the corresponding uniaxial compressive strength is low. Meanwhile, the secondary joint is the key joint for crack propagation and failure at α of 0° and 90° except when β is 90°. The granite specimen occurs the shear failure propagating from secondary joint tips. And, the shear failure crossing upper tips of main and secondary joints is found at α of 0° or 90° and β of 90°. Their uniaxial compressive strengths are large. Also, the combined actions of main and secondary joints determine crack propagation and failure at α of 60° except when β is 90°. The granite specimen occurs the hybrid failure, including shear failure propagating from main joint tips and tensile failure propagating from main and secondary joints center or secondary joint tips. And, when α is 60° and β is 90°, the granite specimen occurs the shear failure along secondary joint plane direction, and its uniaxial compressive strength is small. Generally, when α or β is a fixed value, the uniaxial compressive strength firstly decreases and then increases with the increase of β or α. Additionally, when α is 60° and β>45°, the uniaxial compressive strength represents a decreasing trend. The uniaxial compressive strength at α and β between 30° and 60° is generally small. Finally, the microdisplacement field distributions of granite specimen were discussed.

scholarly journals Unloading Response Characteristics of Cross Fault Caverns: Effect of Fault Angles

2021 ◽  
Author(s):  
Yong-Hui Shang ◽  
Lin-Rong Xu ◽  
Yong-Wei Li
Keyword(s):  
Failure Modes ◽  
Research Result ◽  
Great Influence ◽  
Particle Flow Code ◽  
Energy Response ◽  
Response Characteristics ◽  
Bond Model ◽  
Result Show ◽  
Smooth Joint Model ◽  
Weak Structure

Abstract The research of unloading response characteristics of caverns with weak structure has important engineering value for the development and construction of underground space. In this paper, firstly, the cross fault cavity model is established based on particle flow code (PFC) software, considering different fault dip angles. The parallel bond model (PBM) is used in the cavern model and the smooth joint model (SJM) is used in the fault model. Then, the mechanical, acoustic emission (AE), energy response characteristics and failure modes of the cavern model with different fault angles are explored. The research result show that the fault angle has a great influence on the stress distribution and failure modes of surrounding rock.The existence of faults does not change the overall law of AE evolution curve, that is, the number of AE hits increases first and then decreases. However, the existence of faults changes the maximum number of AE hits and the duration of AE. When the cavern is unloaded, the strain energy of the model first decreases and then increases.

scholarly journals A Novel Method of Calibrating Micro-Scale Parameters of PFC Model and Experimental Validation

2020 ◽  
Vol 10 (9) ◽  
pp. 3221 ◽  
Author(s):  
Hao Wu ◽  
Bing Dai ◽  
Guoyan Zhao ◽  
Ying Chen ◽  
Yakun Tian
Keyword(s):  
Compressive Strength ◽  
Young’S Modulus ◽  
Uniaxial Compressive Strength ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Poisson's Ratio ◽  
Particle Flow Code ◽  
Analysis Tool ◽  
Micro Scale ◽  
Scale Parameters

As a powerful numerical analysis tool, PFC (Particle Flow Code) is widely applied to investigate the mechanical behavior of rock specimen or rock engineering under different stress states. To match the macroscopic properties of the PFC model with those of the rock, a set of micro-scale parameters of the model needs to be calibrated. Thus, this paper proposed an optimization method combining Box–Behnken experimental design and desirability function approach to quickly and accurately find the values of the micro-scale parameters. The sensitivity of the main micro-scale parameters (mean value of parallel-bond normal strength σc, ratio of particle normal to shear stiffness Ec, and Young’s modulus at each particle–particle contact kn/ks) and their interactions to the macroscopic responses (uniaxial compressive strength, Young’s modulus, and Poisson’s ratio) were thoroughly analyzed using response surface theory. After that, validation study was conducted on the calibrated model. The results manifest that the uniaxial compressive strength is extremely significantly affected by σc and kn/ks, the Young’s modulus is highly correlated with Ec and kn/ks, and the Poisson’s ratio is most significantly influenced by kn/ks. Additionally, the interaction of micro-scale parameters also has different impact upon the responses. Moreover, the simulated crack behavior around differently shaped openings in rock samples under uniaxial compression is found to be well agreeable with the experimental results, which verifies the reliability of the proposed method.

Numerical Study on Uniaxial Compression Test of Rock Specimen with Random Holes

2011 ◽  
Vol 418-420 ◽  
pp. 848-850
Author(s):  
Bing Xie ◽  
Li Guo ◽  
Xiang Xia
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Compression Test ◽  
Rock Specimen ◽  
Numerical Study ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Uniaxial Compression Test ◽  
Compression Tests

Numerical specimens with ramdom holes is established by particle flow code PFC2D and uniaxial compression tests are conducted. Studies have shown that the uniaxial compressive strength of the specimen accelerated decline while the porosity increasing uniformly. With the increasing of the porosity，the plastic of the specimen increases.

scholarly journals Mechanical and Failure Criteria of Air-Entrained Concrete under Triaxial Compression Load after Rapid Freeze-Thaw Cycles

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Feng-kun Cui ◽  
Huai-shuai Shang ◽  
Tie-jun Zhao ◽  
Guo-xi Fan ◽  
Guo-sheng Ren
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Stress Ratio ◽  
Triaxial Compression ◽  
Complex Stress State ◽  
Experimental Results ◽  
Testing System ◽  
Freeze Thaw ◽  
Triaxial Compressive Strength ◽  
Air Entrained Concrete

The experiment study on the air-entrained concrete of 100 mm cubes under triaxial compression with different intermediate stress ratioα2=σ2D : σ3Dwas carried out using a hydraulic-servo testing system. The influence of rapid freeze-thaw cycles and intermediate stress ratio on the triaxial compressive strengthσ3Dwas analyzed according to the experimental results, respectively. The experimental results of air-entrained concrete obtained from the study in this paper and the triaxial compression experimental results of plain concrete got through the same triaxial-testing-system were compared and analyzed. The conclusion was that the triaxial compressive strength is greater than the biaxial and uniaxial compressive strength after the same rapid freeze-thaw cycles, and the increased percentage of triaxial compressive strength over biaxial compressive strength or uniaxial compressive strength is dependent on the middle stress. The experimental data is useful for precise analysis of concrete member or concrete structure under the action complex stress state.

scholarly journals Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 213
Author(s):  
Hamid Ait Said ◽  
Hassan Noukrati ◽  
Hicham Ben Youcef ◽  
Ayoub Bayoussef ◽  
Hassane Oudadesse ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Compressive Strength ◽  
Mechanical Strength ◽  
Bone Repair ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Processing Parameters ◽  
Composite Effect ◽  
Solid Liquid ◽  
The Impact

Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field.

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