scholarly journals Experiment and Failure Analysis of Rock-Like Material Affected by Different Excavation Depths

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yuan Tian ◽  
Zhende Zhu ◽  
Xinyu Liu ◽  
Yanxin He
Keyword(s):  
Axial Stress ◽  
Peak Stress ◽  
Initial Crack ◽  
Peak Strain ◽  
Compression Tests ◽  
Hole Depth ◽  
Single Hole ◽  
Stress Direction ◽  
Secondary Cracks ◽  
Shaped Crack

In order to increase the understanding of the strength and failure mechanism of rock mass during tunnel excavation, a series of uniaxial compression tests were conducted on mortar specimen with cracks and holes by using a rock mechanics servo-controlled testing system. And by monitoring the experimental process, the initiation, propagation, and coalescence process of cracks were observed and characterized. According to the experimental results, the influences of the excavation depth on the mechanical parameters and fracture characteristics of mortar specimens with single hole and the ones with single-hole crack were analyzed in detail. In the specimens with single hole, the peak strength decreases with the increase of hole depth, but the peak strain and elastic modulus have no obvious linear correlation with the hole depth. And the position and angle of initial crack change differently with the increase of the hole depth. The position of initial crack moves from the side of the hole to the top of the hole. When the hole depth exceeds 50%, the crack initiation angle is no longer inclined to the axial stress direction, but parallel to the axial stress direction. In the specimens with single prefabricated crack, the wing-shaped secondary cracks are generated at the tip of the precrack, and the antiwing-shaped secondary cracks are generated at the tip when approaching the peak stress. However, in the specimens with single-hole crack, no antiwing-shaped crack appears. And when the hole depth reaches 80%, two wing-shaped cracks appear at the precrack tip. One of the new wing-shaped cracks appears in the direction of the extension line of the precrack.

scholarly journals Axial Stress-Strain Performance of Recycled Aggregate Concrete Reinforced with Macro-Polypropylene Fibres

2021 ◽  
Vol 13 (10) ◽  
pp. 5741
Author(s):  
Muhammad Junaid Munir ◽  
Syed Minhaj Saleem Kazmi ◽  
Yu-Fei Wu ◽  
Xiaoshan Lin ◽  
Muhammad Riaz Ahmad
Keyword(s):  
Axial Stress ◽  
Peak Stress ◽  
Polypropylene Fibre ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Peak Strain ◽  
Stress Strain ◽  
Polypropylene Fibres ◽  
Aggregate Concrete

The addition of macro-polypropylene fibres improves the stress-strain performance of natural aggregate concrete (NAC). However, limited studies focus on the stress-strain performance of macro-polypropylene fibre-reinforced recycled aggregate concrete (RAC). Considering the variability of coarse recycled aggregates (CRA), more studies are needed to investigate the stress-strain performance of macro-polypropylene fibre-reinforced RAC. In this study, a new type of 48 mm long BarChip macro-polypropylene fibre with a continuously embossed surface texture is used to produce BarChip fibre-reinforced NAC (BFNAC) and RAC (BFRAC). The stress-strain performance of BFNAC and BFRAC is studied for varying dosages of BarChip fibres. Results show that the increase in energy dissipation capacity (i.e., area under the curve), peak stress, and peak strain of samples is observed with an increase in fibre dosage, indicating the positive effect of fibre addition on the stress-strain performance of concrete. The strength enhancement due to the addition of fibres is higher for BFRAC samples than BFNAC samples. The reduction in peak stress, ultimate strain, toughness and specific toughness of concrete samples due to the utilisation of CRA also reduces with the addition of fibres. Hence, the negative effect of CRA on the properties of concrete samples can be minimised by adding BarChip macro-polypropylene fibres. The applicability of the stress-strain model previously developed for macro-synthetic and steel fibre-reinforced NAC and RAC to BFNAC and BFRAC is also examined.

scholarly journals Permeability Characteristic and Failure Behavior of Filled Cracked Rock in the Triaxial Seepage Experiment

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Xinyu Liu ◽  
Zhende Zhu ◽  
Aihua Liu
Keyword(s):  
Growth Rate ◽  
Rock Mass ◽  
Failure Modes ◽  
Peak Stress ◽  
Confining Pressure ◽  
Strength Characteristics ◽  
Failure Behavior ◽  
Compression Tests ◽  
Secondary Cracks ◽  
Safety And Stability

Filling is commonly found in natural cracked rock mass. As the weakest part of the rock, the filling properties directly affect the rock deformation and strength, permeability, and so on and affect the safety and stability of the rock mass engineering. In this study, a single slit has been preset in sandstones and filled with different physical properties materials. Based on the laboratory triaxial seepage test, the permeability and strength characteristics of filled cracked sandstones are analyzed, and the failure modes are obtained. The main findings of this study are as follows: (1) The permeability coefficient peak value of the filled cracked rock appears before the stress peak. (2) At the same confining pressure growth rate, the peak stress growth rate of the filled cracked rock is generally higher than that of the intact rock and the strength growth rate of the cracked rock increases with the length of the fracture. The strength characteristics of the filling in the uniaxial compression tests and triaxial seepage tests are significantly affected by the hydraulic properties. (3) The strength and permeability coefficients of cracked rock filled with cement mortar are more sensitive to the change of confining pressure, while under the same condition, the ones of cracked rock filled with gypsum mortar are stable. (4) According to the failure mechanism, under the seepage stress, the secondary cracks can be divided into 3 types and the failure modes can be divided into 2 types.

scholarly journals Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Huamin Li ◽  
Huigui Li ◽  
Baobin Gao ◽  
Dongjie Jiang ◽  
Junfa Feng
Keyword(s):  
Acoustic Emission ◽  
Elasticity Modulus ◽  
Loading Rate ◽  
Peak Stress ◽  
Test System ◽  
Strong Impact ◽  
Peak Strain ◽  
Compression Tests ◽  
Loading Rates ◽  
The Relationship

To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples.

Influence of δ Phase Content on Hot Deformation Behavior of Ni-Based Superalloy IN718

2011 ◽  
Vol 314-316 ◽  
pp. 1159-1162
Author(s):  
Hai Yan Zhang ◽  
Shi Hong Zhang ◽  
Ming Cheng
Keyword(s):  
Hot Deformation ◽  
Deformation Behavior ◽  
Peak Stress ◽  
Hot Working ◽  
Peak Strain ◽  
Phase Content ◽  
Compression Tests ◽  
Hot Deformation Behavior ◽  
Deformation Activation Energy ◽  
Δ Phase

The effect of δ phase content on the hot deformation behavior of alloy IN718 has been investigated using isothermal compression tests. The results indicated that the δ phase has a significant effect on the deformation behavior of alloy IN718 during hot working. After the peak stress, the decreasing speed of the stress raises as the increase in the δ phase content. The deformation activation energy for alloy IN718 increases with the raise of the δ phase content. And the peak strain for the alloy decreases with the increase of the δ phase content, which indicates that the δ phase can stimulate the occurrence of dynamic recrystallization during hot working.

The Test of Dynamic Characteristics of Concrete under Biaxial Compression State

2013 ◽  
Vol 859 ◽  
pp. 177-181
Author(s):  
Jin Sheng Lei ◽  
Fei Liu ◽  
Gang Peng ◽  
Min Lei
Keyword(s):  
Stress State ◽  
Dynamic Characteristics ◽  
Dynamic Compression ◽  
Testing Machine ◽  
Peak Stress ◽  
Biaxial Stress ◽  
Biaxial Compression ◽  
Peak Strain ◽  
Compression Tests ◽  
True Triaxial

Concrete structure in reality mostly in complicated stress state, dynamic characteristics and static characteristics under earthquakes and other dynamic loads are very different. For a further understanding of the dynamic characteristics of the concrete, true triaxial testing machine system was used to the C30 concrete at different strain rates and different side of the cube concrete specimens stress biaxial dynamic compression tests. Biaxial stress state concrete elasticity modulus, peak stress, peak strain, was obtained by the experimental study, and carries on the comparative analysis. Results show that: the dynamic characteristics of concrete under biaxial compression state of concrete and uniaxial condition are very different.

scholarly journals Effect of High-Stress Equal Amplitude Cyclic Loading on Mechanical and Deformation Characteristics of Rubber Concrete

2019 ◽  
Vol 3 (5) ◽  
Author(s):  
Xin Huang ◽  
Yu Chen
Keyword(s):  
Cyclic Loading ◽  
High Stress ◽  
Peak Stress ◽  
Repeated Loading ◽  
Peak Strain ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Degradation Degree ◽  
Rubber Concrete ◽  
Equal Amplitude

In order to study the mechanical and deformation characteristics of rubber concrete under repeated loading, 50 cycles of high-stress equal amplitude cyclic loading and uniaxial compression tests were carried out on 30 concrete specimens of 5 groups. The change of uniaxial mechanical properties and the deformation during cyclic loading of normal concrete (NC) and rubber concrete (RC) with 5%, 10%, 15%, and 20% content were analysed. The results show that the peak stress and modulus of elasticity decrease and the peak strain increases with the increase of rubber content. After cyclic loading, the degradation degree of NC peak stress and elastic modulus reached 11.0% and 36.8% respectively. This study can provide a basis for the application of rubber concrete.

Dynamic Recrystallization Behavior of High Carbon Chromium Bearing Steel

2014 ◽  
Vol 584-586 ◽  
pp. 1011-1016
Author(s):  
Xiao Lei Zhang ◽  
Hui Li ◽  
Shi Xin Xu ◽  
Zhi Chao Li ◽  
Zhen Li Mi
Keyword(s):  
Flow Stress ◽  
Dynamic Recrystallization ◽  
Peak Stress ◽  
Bearing Steel ◽  
Peak Strain ◽  
Compression Tests ◽  
Gcr15 Bearing Steel ◽  
Dynamic Recrystallization Behavior ◽  
Gleeble 3500 ◽  
Relationship Of

The effect of process parameters on dynamic recrystallization of GCr15 bearing steel was investigated by a single-pass compression tests using Gleeble-3500 thermal simulator. The results indicate that the flow stress decreases with the increasing of temperature and the decreasing of strain rate. The dynamic recrystallization rate increases with the increasing of deformation temperature. By regression analysis, the mean activation energy and the stress exponent are determined to be 435.1KJ/mol-1and 5.0505 respectively. Meanwhile, the kinetic mathematical model of dynamic recrystallization and constitutive equation are established.The relationship of peak stress, peak strain and Z parameters is founded by using the data of flow stress curves.

scholarly journals An Experimental Study on Cracking Behavior of Precracked Sandstone Specimens under Seepage Pressure

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Qibin Lin ◽  
Ping Cao ◽  
Hua Wang ◽  
Rihong Cao
Keyword(s):  
Shear Failure ◽  
Fractured Rock ◽  
Axial Stress ◽  
Failure Process ◽  
Tensile Failure ◽  
Peak Strain ◽  
Compression Tests ◽  
Cracking Behavior ◽  
Seepage Pressure ◽  
Loading Device

This paper aims to investigate the strength and failure mechanism of fractured rock under seepage pressure. For this purpose, precracked sandstone specimens were prepared with different fissure angles, and a seepage pressure loading device was created. Together with the acoustic emission (AE) system, the loading device was adopted to perform uniaxial compression tests with or without seepage pressure. The main results are as follows. Combined with axial stress-strain curves, photographic monitoring results and the output of AE counts and rock failure process can be generally divided into four stages: microcrack closure, elastic deformation, crack growth and propagation, and final failure. The seepage pressure had a significant effect on the mechanical properties of the specimens: the specimens under seepage pressure lagged far behind those without seepage pressure in peak strength but maintained a comfortable lead in peak strain. Under seepage pressure, the typical failure features of the specimens varied with the fissure angles: the specimens with small fissure angles (i.e., [0°,30°]) mainly underwent tensile failure; those with medium fissure angles (i.e., [30°,60°]) suffered from shear failure; and those with large fissure angles (i.e., [60°,75°]) were prone to tensile-shear failure.

Effects of temperature gradient on the granite’s mechanical properties

2021 ◽  
pp. 1-10
Author(s):  
Jinyong Pei ◽  
Huagang He ◽  
Dongtao Hu ◽  
Shanke Lv ◽  
Jing Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Temperature Gradient ◽  
Strain Curve ◽  
Peak Stress ◽  
Tangent Modulus ◽  
Peak Strain ◽  
Compression Tests ◽  
Different Temperatures ◽  
Effects Of Temperature ◽  
Increasing Temperature

Temperature gradient significantly affects the production of surrounding rock stress in mining engineering. The mechanics and deformation characteristics of the rock will change under the temperature gradient, thereby increasing the probability of accidents in the roadway. This paper conducts uniaxial compression tests on granite at different temperatures from room temperature to 250∘C, and analyzes in detail the changes in the stress-strain curve, peak stress, peak strain and tangent modulus of granite under high temperature and different temperature gradient conditions. The results of this study are as follows: (1) Under high temperature conditions, the granite’s peak stress and tangent elastic modulus increased with temperature from 17 to 100∘C, then decreased from 100∘C to 250∘C, whereas the granite’s peak strain increased steadily with increasing temperature; (2) under temperature gradient, the granite’s peak stress and tangent modulus first decreased and then increased with increasing temperature gradient, while the granite’s peak strain first decreased and then increased at 100∘C, but first increased and then decreased from 150∘C to 250∘C.

Investigation on Constitutive Equations for TA15 during Hot Working

2012 ◽  
Vol 184-185 ◽  
pp. 1492-1496
Author(s):  
Yan Shu Zhang ◽  
Yan Sun
Keyword(s):  
Titanium Alloy ◽  
Strain Rate ◽  
Peak Stress ◽  
Peak Strain ◽  
Compression Tests ◽  
Hollomon Parameter ◽  
Deformation Strain ◽  
Β Phase ◽  
Linear Relationships ◽  
Ta15 Titanium Alloy

Hot compression tests were conducted on Gleeble-1500 thermal simulator for TA15 titanium alloy at temperatures of 750~1050 °C and at strain rate of 0.001 ~ 1 s with a deformation reduction of 60%. The results show that the flow stress of TA15 titanium alloy increases rapidly to a peak with deformation strain, then decreases to a saturation status. The steady and peak stress significantly decreases with deformation temperature increasing and strain rate decreasing. The activation energies (Q) are 619.264kJ/mol in (α+β) phase and 522.58kJ/mol in β phase, respectively. It was found that the parameters, peak stress σp, steady stress σres, peak strain εp and steady strain εres, have linear relationships with Zenner-Hollomon parameter, Z.

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