scholarly journals Experimental Investigation on Deformation and Strength Behavior of Marble with the Complex Loading-Unloading Stress Path

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Chen Chen ◽  
Lipeng Liu ◽  
Yu Cong
Keyword(s):  
Elastic Strain ◽  
Strain Energy ◽  
High Stress ◽  
Elastic Strain Energy ◽  
Complex Loading ◽  
Energy Criterion ◽  
Confining Pressure ◽  
Stress Path ◽  
Surrounding Rock ◽  
Strength Behavior

The excavation of deep tunnel in rock mass undergoes complex loading and unloading stress paths, resulting in rib spalling, flaking, and even severe rockburst disasters. Based on the variation law of the stress path of the surrounding rock, laboratory tests of rock mechanics are designed, and the deformation and strength behavior of marble with different initial confining pressure and unloading rates are systematically studied. By introducing strain increment, the characteristic stress, and the dilatancy index, the rock’s dilatancy and brittleness under different unloading conditions are quantitatively analyzed. During unloading, the energy transformation mechanism of rock is described, and the law of deformation and failure is discussed based on characteristic energy. The rock failure strength fitting formula is given by applying the Mogi–Coulomb criterion and elastic strain energy criterion. The advantages of the elastic strain energy criterion are theoretically explained. This study shows that comprehensive consideration of the complex stress paths, confining pressure levels, and the loading-unloading rates of surrounding rock is an effective way to accurately study unloading rock characteristics. The results can provide theoretical basis for stability analysis of high-stress underground engineering.

scholarly journals Study on Energy Evolution and Damage Constitutive Model of Siltstone

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1271
Author(s):  
Ruihe Zhou ◽  
Longhui Guo ◽  
Rongbao Hong
Keyword(s):  
Elastic Strain ◽  
Strain Energy ◽  
Yield Criterion ◽  
Axial Strain ◽  
Elastic Strain Energy ◽  
Confining Pressure ◽  
Energy Yield ◽  
Input Energy ◽  
Test Results ◽  
Damage Constitutive Model

In order to study the energy evolution characteristics and damage constitutive relationship of siltstone, the conventional triaxial compression tests of siltstone under different confining pressures are performed, and the evolution laws of input energy, elastic strain energy and dissipative energy of siltstone with axial strain and confining pressure are analyzed. According to the test results, the judgment criterion of the rock damage threshold is improved, and an improved three-shear energy yield criterion is proposed., The damage constitutive equation of siltstone is established based on the damage mechanics theory through the principle of minimum energy consumption and by considering the residual strength of rock, and lastly, the rationality of the model is verified by experimental data. The results reveal that (1) both the input energy and dissipative energy gradually increase with the increase of axial strain, and the elastic strain energy first increases and then decreases with the increase of axial strain, and reaches its maximum at the peak. (2) The input energy and dissipation energy increase exponentially with the increase of the confining pressure, and the elastic strain energy increases linearly with the increase of confining pressure. (3) According to the linear relationship between the sum of shear strain energy and hydrostatic pressure, an improved three-shear energy yield criterion is established. (4) The model curve can better describe the strain softening stage and the residual strength characteristics of siltstone. The relative standard deviation between the model results and the test results is only 4.35%, which verifies the rationality and feasibility of the statistical damage constitutive model that is established in this paper.

scholarly journals Experimental Study of Influence of Support Failures on Rockbursts under True-Triaxial Condition

2018 ◽  
Vol 2018 ◽  
pp. 1-20 ◽  
Author(s):  
Guoshao Su ◽  
Tianbin Li ◽  
Jianqing Jiang ◽  
Guoqing Chen ◽  
Jinghai Mo
Keyword(s):  
Kinetic Energy ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Test System ◽  
Surrounding Rock ◽  
Underground Engineering ◽  
True Triaxial ◽  
Static Failure ◽  
Rock Specimens

Supports can effectively reinforce the surrounding rock after excavation in underground engineering. However, a support failure may cause an extremely intense rockburst. Hence, the influences of support failures, including support forces, support failure timings, and support failure rates, on rockbursts were systematically investigated in the present study. Unloading tests on rock specimens, using a true-triaxial rockburst test system, were performed to simulate rockbursts induced by support failure. The experimental results indicate that increasing support forces increased the prepeak accumulated elastic strain energy, the kinetic energy of the ejection fragment, and the ratio between the kinetic energy and release strain energy, whereas the damage to the rock specimens declined. During the testing process, the longer it took to unload the minimum stresses was, which means that the later the support failed, the greater the prepeak accumulated elastic strain energy was, the kinetic energies of the ejection fragments were, and the ratio of the kinetic energy and release strain energy was. Furthermore, as the support failure rate incremented, the kinetic energies of the ejection fragments of the rockbursts linearly increased, the failure mode of the rock changed from static failure to dynamic rockbursts, and the intensities of the rockbursts increased.

scholarly journals Study on the Meso-Energy Damage Evolution Mechanism of Single-Joint Sandstone under Uniaxial and Biaxial Compression

2021 ◽  
Vol 2021 ◽  
pp. 1-27
Author(s):  
Gui-Lin Wang ◽  
Tian-Ci Cao ◽  
Fan Sun ◽  
Xing-Xiang Wen ◽  
Liang Zhang
Keyword(s):  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Confining Pressure ◽  
Biaxial Compression ◽  
Level Energy ◽  
Energy Evolution ◽  
Peak Point ◽  
Joint Inclination ◽  
Joint Length

Energy conversion and release occur through the entire deformation and failure process in jointed rock masses, and the accumulation and dissipation of rock mass energy in engineering can reveal the entire process of deformation and instability. This study uses PFC2D to carry out numerical simulation tests on single-joint sandstone under uniaxial compression and biaxial compression, respectively, and analyse the influence of joint inclination, length, and confining pressure on the meso-energy conversion process and phase evolution of jointed sandstone. Through analysis, it is found that the input meso total strain energy is transformed into meso dissipated energy and meso-elastic strain energy. Macroscopic and microscopic joint sandstone law is consistent with the overall energy evolution; and the difference is reflected in two aspects: (1) the microlevel energy evolution has no initial compaction energy consumption section and (2) the linear energy storage section before the macroenergy evolution peak can be subdivided into two sections in the meso-level energy evolution. Under uniaxial compression, the energy values at the characteristic points of the meso-level energy evolution phases first asymmetrically decrease and then increase with the increase of the joint inclination. The initiation point of jointed sandstone is significantly affected by the length of the joint, and the degradation effect of the meso-energy at the damage point and peak point weakens with the increase of the joint length. Comparing the data obtained from the PFC numerical simulation with the experimental data, it is found that the error is small, which shows the feasibility of the numerical model in this paper. Under biaxial compression, the accumulation rate of meso-elastic strain at the peak point of the jointed sandstone first decreases and then increases with the joint inclination angle. After the peak of jointed sandstone, the rate of sudden change of meso-energy change decreases with the increase of joint length. The conditions of high confining pressure will promote the meso-accumulated damage degree of the jointed sandstone before the peak, while inhibiting the meso-energy and the mutation degree of the damage after the peak. The higher the confining pressure, the more obvious the joint length and inclination effect characteristics of the elastic strain energy at the peak point of the jointed sandstone.

scholarly journals Energy Evolution and Acoustic Emission Characteristics of Sandstone Specimens under Unloading Confining Pressure

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Tao Qin ◽  
Yanwei Duan ◽  
Hongru Sun ◽  
Honglei Liu ◽  
Lei Wang
Keyword(s):  
Acoustic Emission ◽  
Elastic Strain ◽  
Strain Energy ◽  
High Stress ◽  
Confining Pressure ◽  
Emission Characteristics ◽  
Energy Evolution ◽  
Peak Point ◽  
Unloading Confining Pressure ◽  
Rock Specimens

The acoustic emission characteristics of rock specimens under different initial unloading confining pressures were tested to obtain the damage and rupture characteristics of the sandstone unloading confining pressure path. The CT scan and three-dimensional reconstruction of the fractured rock specimens were carried out to study the differences of energy evolution and acoustic emission characteristics during the failure of sandstone under different initial unloading pressures. The results show that the unloading confining pressure has a significant influence on the deformation and failure of the rock. There is a significant yielding platform for the circumferential strain and the bulk strain at the peak of the unloading pressure. The larger the initial unloading pressure is, the greater the axial absorption strain energy, the dissipative energy, and the elastic strain energy are at the peak point. After the stress peak point, the elastic strain can be quickly converted into the dissipative energy for rock damage. The elastic energy released from the moment of rock failure under high confining pressure is more concentrated. The acoustic emission ringing and b value characteristic parameters of the rock have a good correlation with the internal energy evolution of the rock, which better reflects the progressive damage of the rock under low stress and the sudden failure of high-stress unloading.

The elastic-strain energy criterion of phase formation for complex concentrated alloys

Materialia ◽  
2019 ◽  
Vol 5 ◽  
pp. 100222 ◽  
Author(s):  
Angelo F. Andreoli ◽  
Jiri Orava ◽  
Peter K. Liaw ◽  
Hans Weber ◽  
Marcelo F. de Oliveira ◽  
...  
Keyword(s):  
Phase Formation ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Energy Criterion

scholarly journals Discussions on the Complete Strain Energy Characteristics of Deep Granite and Assessment of Rockburst Tendency

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Lu Chen ◽  
Lijie Guo
Keyword(s):  
Time Delay ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Confining Pressure ◽  
Strain Effect ◽  
Peak Strain ◽  
Rockburst Hazard ◽  
Linear Elastic ◽  
Loading And Unloading

In deep mining, the rockburst hazard has become a prominent problem. Rockburst is difficult to be predicted, and it gives a severe threat to mining safety. In this paper, the triaxial compressive tests with an acoustic emission (AE) device and full cyclic loading and unloading tests were carried out, respectively, to present characteristics of linear elastic strain energy and peak strain energy. Also, to consider the time-delay strain characteristics of granite found in the abovementioned tests, a new stage loading and unloading test with dual monitoring systems was designed and performed. Through 20 days’ time-delay strain monitoring, the peak-strength strain energy was further modified. The results showed that the peak strain energy is approximate 1.2-1.3 times than linear elastic strain energy under the same confining pressure, and after considering the time-delay strain effect, the modified maximal strain energy value of the deep granite significantly increased. The peak strain energy values are further enhanced from 1.0 × 104 J/m3 to 1.8 × 104 J/m3, respectively. At last, by taking advantage of the strain energy index model of rockburst, the tendency and intensity of rockburst were assessed contrastively.

scholarly journals Study on the Instability Mechanism and Control Measures of a Roadway in a Mine with Retained Coal Pillars and Close Coal Seams

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Huai-Qian Liu ◽  
Lei Wang ◽  
Lian-Chang Han ◽  
Ping Liu ◽  
Peng Zou
Keyword(s):  
Energy Release ◽  
Elastic Strain ◽  
Strain Energy ◽  
Coal Pillar ◽  
Elastic Strain Energy ◽  
Surrounding Rock ◽  
Burial Depth ◽  
Moderate Pressure ◽  
Pillar Width ◽  
Energy Accumulation

The deformation and instability of roadway surrounding rock reflect the processes of energy accumulation and release. To reveal the instability of roadway surrounding rock, based on the engineering geological conditions of a certain mine, this paper established a nonuniform superimposed stress model of a coal pillar, starting from the energy accumulation and release of the surrounding rock of the floor roadway after coal pillar failure. The essence of the deformation of the lower roadway was revealed, and the following conclusions were drawn: (1) The elastic strain energy accumulated in the lower roadway roof and upper coal pillar is related to not only the physical properties of the coal seam but also the distance between the coal pillar and surrounding rock, the caving height and shape, the burial depth, and the retained pillar width. (2) The elastic strain energy accumulated in the lower roadway roof and the upper coal pillar induced large displacements of the roadway due to the energy release during excavation. (3) It is proposed that the “stress relief degree” and failure morphology are used to identify zones in the rock and coal, and the two zoning modes have a high consistency. (4) The stress distribution in a narrow coal pillar should be calculated in segments. (5) Based on the zoning and energy release characteristics, the following control factors are suggested regarding the coal pillar width and roadway layout: (a) for the coal pillar, avoid the overlap or intersection of the peak values in the limit equilibrium zone and ensure a sufficient elastic zone; (b) arrange the roadway in shear slip Zone B-2 or the moderate pressure relief Zone B-2 to reduce the accumulation of elastic strain energy in the surrounding rock.

scholarly journals A Study of the Anchorage Body Fracture Evolution and the Energy Dissipation Rule: Comparison between Tensioned Rock Bolts and Torqued Rock Bolts

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Bowen Wu ◽  
Xiangyu Wang ◽  
Jianbiao Bai ◽  
Shuaigang Liu ◽  
Guanghui Wang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Energy Dissipation ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Surrounding Rock ◽  
Rock Bolts ◽  
External Work ◽  
Fracture Evolution ◽  
The Stability

Rock bolt support is an effective technique for controlling surrounding rock of deep roadway. The stability of the anchorage body composed of rock bolts and surrounding rock mass is the core in keeping the stability of roadways. In this paper, the UDEC Trigon model was used in simulating uniaxial compressive test on the anchorage body under different pretension loads. The energy equilibrium criterion of the anchorage body under the uniaxial compressive state was proposed. Furthermore, the fracture evolution and the energy dissipation during the failure process of the anchorage body were analyzed. Results showed that before the peak strength, the external work was stored in the anchorage body in the form of the elastic strain energy (Ue). After the peak, energy dissipated through three ways, including the fracture developing friction (Wf), plastic deformation (Wp), and acoustic emission (Ur). Based on the simulation results, the high pretensioned rock bolts can eliminate the continuous tensile fractures in the anchorage body, decreasing the damaging extent of the anchorage body and the energy that was consumed by the following two main approaches: fracture developing friction (Wf) and plastic deformation (Wp). Moreover, the surplus of the elastic strain energy (Ue) and the strength of the anchorage body can be improved. The pretension load had a positive relationship with elastic strain energy and a negative relationship with the anchorage body damage degree. Based on the above research, the transport roadway of the working face 6208 in the Wangzhuang Coal Mine selected tensile rock bolts to establish the high-performance anchorage body. The monitoring data showed that this reinforcement method effectively managed the serious deformation issue of the roadway surrounding the rock masses.

scholarly journals Rockburst Characteristics and Mechanisms during Steeply Inclined Thin Veins Mining: A Case Study in Zhazixi Antimony Mine, China

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Yuanjun Ma ◽  
Changwu Liu ◽  
Fan Wu ◽  
Xiaolong Li
Keyword(s):  
Numerical Simulation ◽  
Elastic Strain ◽  
Strain Energy ◽  
High Stress ◽  
Elastic Strain Energy ◽  
Compression Tests ◽  
High Stress Concentration ◽  
Mining Depth

With the increase of mining depth, rockbursts have become important safety problems in Zhazixi Antimony Mine, where overlying strata exceed 560 m. Due to the small spacing between the steeply inclined veins, mining activities have great influences on rockbursts of adjacent veins. In order to study rockburst characteristics and mechanisms in Zhazixi Antimony Mine, in situ measurement, field geological survey, uniaxial compression tests, and numerical simulation are conducted to analyze rockburst proneness and simulate the elastic strain energy accumulation characteristics. Consequently, rockburst proneness criteria are established on the basis of experimental results to propose the necessary lithologic conditions for rockburst aiming to Zhazixi Antimony Mine. Rockburst dangerous districts are defined based on high stress concentration and elastic strain energy distribution characteristics in mining process obtained by theory analysis and numerical simulation. Accordingly, it is suggested that thrown-type rockbursts mainly occur in massive stibnite of ventilation shafts and stopes where the elastic strain energy exceeds 300 kJ·m−3, spalling-type rockbursts generally appear in slate of roadways where the elastic strain energy exceeds 100 kJ·m−3, and ejection-type rockbursts arise in different rock masses under a certain condition. Last but not the least, prediction results are basically consistent with statistics data of rockburst events after comparative analysis.

Sign in / Sign up

Export Citation Format

Share Document