scholarly journals Strength Weakening Effect of High Prestatically Loaded Marble Subjected to Low-Frequency Dynamic Disturbance under Point Load

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Wuxing Wu ◽  
Fengqiang Gong
Keyword(s):  
Coupling Effect ◽  
Low Frequency ◽  
Point Load ◽  
Load Level ◽  
Strength Characteristics ◽  
Point Load Strength ◽  
Dynamic Disturbance ◽  
Disturbance Frequency ◽  
Strength Change ◽  
Disturbance Loading

The deep high prestatically loaded rock is often subjected to low-frequency dynamic disturbance and exhibits unusual strength characteristics, and thus, it is important to investigate the strength characteristics under the coupling effect of prestatic load and low-frequency dynamic disturbance loading conditions. In this study, a series of point load tests were conducted on the high prestatically loaded marble subjected to low-frequency disturbance by the MTS system, focusing on exploring the role of prestatic load level and low-frequency disturbance frequency in the process of rock strength change. Based on the average static failure load (Fmax) of samples under the static point loading, the high prestatic load levels (Fp) were selected as 70%, 80%, and 90% of Fmax, the corresponding low-frequency dynamic disturbance was loaded by sinusoidal waves with amplitudes of 60%, 40%, and 20% of Fmax, and the low-frequency dynamic disturbance frequencies (f) are 1, 2, 5, and 10 Hz. The change curve of the point load strength with the prestatic load level or the disturbance frequency was analyzed, which indicates that the point load strength under the coupled high prestatic load and low-frequency dynamic disturbance load was significantly lower than that under the pure static loading, presenting a significant point load strength weakening effect. Only when Fp or f reaches a certain level, the point load strength decreases significantly as f or Fp increases. Moreover, the point load strength weakening rate was proposed to characterize the degree of strength weakening. The comprehensive analysis demonstrates that Fp has a greater effect on the point load strength weakening effect than f, which is mainly reflected in the point load strength weakening level dominated by the Fp, and the weakening degree is affected by f.

scholarly journals Experimental Study on Mudstone’s Strength Characteristics in Deep-Buried Coal-Measure Formation: A Case Study of Permian Longtan Formation

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Ke Li ◽  
Weijian Yu ◽  
Youlin Xu ◽  
Long Lai ◽  
Hui Zhang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Rock Mechanics ◽  
Point Load ◽  
Strength Characteristics ◽  
Coal Measure ◽  
Strength Index ◽  
Point Load Strength ◽  
Point Load Strength Index ◽  
Linear Fitting

To investigate the strength characteristics of mudstone in deep-buried coal-measure formation, four types of experiments have been conducted: (i) the X-ray diffraction (XRD) test; (ii) the scanning electron microscope (SEM) scanning test; (iii) the point load strength index test; and (iv) the uniaxial compressive strength test. It was concluded that the mudstone of the deep-buried coal measures in the Longtan Formation is dominated by chlorite, quartz, and albite using the XRD test, of which chlorite is primary, accounting for 74.3%. It was found that the three minerals in the mudstone are unevenly distributed using the SEM scanning test, albite is irregularly distributed in chlorite, and quartz is present in the albite and chlorite. Sixty-five specimens were tested for the point load strength index. After processing the data using the method suggested by the International Society for Rock Mechanics and Rock Engineering(ISRM), it was found that the maximum value of Is(50) was 6.10 MPa, the minimum is 0.14 MPa, and 53% of the specimens’ Is(50) values are below 2.0 MPa. The RMT-150C rock mechanics testing machine was used to conduct uniaxial compression tests on six specimens. The maximum uniaxial compressive strength (UCS) value is 59.26 MPa, the minimum value is 31.77 MPa, and the average is 45.64 MPa. Linear fitting and logarithmic fitting are carried out for the correlation between UCS and Is(50). The goodness of fit R2 of the linear fitting is 0.863, and that of the logarithmic fitting is 0.919, indicating a strong correlation between them. When it is challenging to make standard specimens, Is (50) can be used to estimate UCS.

Spherically isotropic, elastic spheres subject to diametral point load strength test

1999 ◽  
Vol 36 (29) ◽  
pp. 4473-4496 ◽  
Author(s):  
K.T. Chau ◽  
X.X. Wei
Keyword(s):  
Point Load ◽  
Strength Test ◽  
Point Load Strength

The Lightning Electromagnetic Pulse Coupling Effect Inside the Shielding Enclosure With Penetrating Wire

Frequenz ◽  
2017 ◽  
Vol 71 (11-12) ◽  
Author(s):  
Xue Jiao ◽  
Bo Yang
Keyword(s):  
Electromagnetic Pulse ◽  
Coupling Effect ◽  
Fdtd Method ◽  
Current Source ◽  
Low Frequency ◽  
Frequency Component ◽  
Lightning Current ◽  
Proper Size ◽  
Practical Engineering ◽  
Difference Time

AbstractTo study the lightning electromagnetic pulse (LEMP) coupling and protection problems of shielding enclosure with penetrating wire, we adopt the model with proper size which is close to the practical engineering and the two-step finite-difference time-domain (FDTD) method is used for calculation in this paper. It is shown that the coupling voltage on the circuit lead inside the enclosure increases about 34 dB, when add 1.0 m long penetrating wire at the aperture, comparing with the case without penetrating wire. Meanwhile, the waveform, has the same wave outline as the lightning current source, shows that the penetrating wire brings a large number of low frequency component into the enclosure. The coupling effect in the enclosure will reduce greatly when penetrating wire has electrical connection with the enclosure at the aperture and the coupling voltage increase only about 12 dB than the case without penetrating wire. Moreover, the results show that though the waveguide pipe can reduce the coupling effect brought by the penetrating wire, the exposing part of penetrating wire can increase the coupling when the penetrating wire outside the enclosure is longer than the waveguide pipe and the longer the exposing part is, the stronger the coupling is.

The mechanical behavior of the Kettle Point oil shale

1986 ◽  
Vol 23 (1) ◽  
pp. 87-93 ◽  
Author(s):  
Maurice B. Dusseault ◽  
Matthias Loftsson ◽  
David Russell
Keyword(s):  
Oil Shale ◽  
Clay Content ◽  
Organic Content ◽  
Point Load ◽  
Brazilian Test ◽  
Point Load Strength ◽  
Triaxial Strength ◽  
Deformation Properties ◽  
Strength And Deformation ◽  
Oil Shales

Samples of eastern black shale (Kettle Point oil shales, Ontario) were subjected to extensive mineralogical and geomechanical tests. We prove that the mineralogy, as measured by the ratio of quartz to illite, controls strength and deformation properties, and the organic material plays no significant role. The reason is that increasing clay content dilutes the rigid quartz–quartz grain contacts that are responsible for the high strengths and stiff behavior. Tests of temperature effects on point load strength of another low organic content oil shale confirm that organic matter is not important to mechanical properties in matrix-supported shales. Key words: shale, mineralogy, Brazilian test, triaxial strength, organic content, slake durability, thermogravimetry.

scholarly journals Analysis of Shear Characteristics of Deep, Anchored Rock Mass under Creep Fatigue Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xiaofeng Li ◽  
Zhixiang Yin
Keyword(s):  
Rock Mass ◽  
Rock Strength ◽  
Low Frequency ◽  
Fatigue Loading ◽  
Load Level ◽  
Rock Masses ◽  
Sandstone Rock ◽  
Fatigue Model ◽  
Creep Fatigue ◽  
Marble Rock

To study the influence of earthquakes and engineering disturbances on the deformation of deeply buried rock masses, shear tests were carried out on anchored sandstone rock masses, anchored marble rock masses, and anchored granite rock masses under creep fatigue loading, and a new creep fatigue model was established to characterize the deformation characteristics of anchored rock masses under creep fatigue loading. The creep fatigue curves of different lithologies clearly show three stages: creep attenuation, steady-state creep, and accelerated creep. Fatigue loading can increase the creep of anchored specimens, and the lower the rock strength is, the higher the creep variable under fatigue loading is. However, for the same rock strength, with the increase in load level, the creep variable produced by creep fatigue load presents a linear downward trend. Considering the changes in the mechanical properties of the anchored rock mass under creep fatigue loading, the creep fatigue model of anchored rock masses is established by introducing a function of the fatigue shear modulus, and the accuracy and applicability of the model are verified by laboratory creep fatigue test data. The model provides a theoretical basis for the study of anchored rock mass support under low-frequency earthquakes or blasting loads.

Coupling effect of low-frequency electromagnetic pulse on complex electrically large object

2010 ◽  
Vol 22 (11) ◽  
pp. 2679-2683
Author(s):  
黄隽 Huang Jun ◽  
胡云安 Hu Yun’an ◽  
张浩然 Zhang Haoran ◽  
金焱 Jin Yan
Keyword(s):  
Electromagnetic Pulse ◽  
Coupling Effect ◽  
Low Frequency ◽  
Large Object
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