scholarly journals Blast Induced Crack Propagation and Damage Accumulation in Rock Mass Containing Initial Damage

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Yixian Wang ◽  
Siyao Wang ◽  
Yanlin Zhao ◽  
Panpan Guo ◽  
Yan Liu ◽  
...  
Keyword(s):  
Rock Mass ◽  
Crack Propagation ◽  
Damage Accumulation ◽  
Damage Variable ◽  
Initial Damage ◽  
Sonic Wave ◽  
Geological Discontinuities ◽  
Definition Of ◽  
Safety And Stability

Blast induced rock mass damage and crack propagation play important roles in structure safety and stability in mining, quarrying, and civil constructions. This paper focuses on the effect of small blasthole diameter blast on crack propagation and damage accumulation in water-bearing rock mass containing initial damage composed of inherent geological discontinuities and previous multiblast induced damage. To elucidate this effect, theoretical analysis of calculation method for several important blast influencing factors is firstly presented. Secondly, definition of a practical damage variable using ratio of longitudinal wave velocity in rock mass before blast occurrence to that after blast occurrence and derivation of a damage accumulation calculation equation accounting for initial damage and blasting effect are described. Lastly, a detailed description of the conducted in situ blast tests and plan layout of the sonic wave monitoring holes is reported. The results indicate that blast activates and then extends the initial cracks in rock mass, leading to accumulation of rock mass damage. The rock mass damage accumulation can be conveniently quantified using the proposed damage variable. When the damage variable reaches its threshold of 0.19, occurrence of damage in the surrounding rock mass is indicated. It is also found that the blast induced rock mass damage extent and the blast induced vibration velocities decrease nonlinearly with increasing the distance between blast source and monitoring position.

scholarly journals Effects of Unidirectional In Situ Stress on Crack Propagation of a Jointed Rock Mass Subjected to Stress Wave

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhanfeng Fan ◽  
Jianhua Cai
Keyword(s):  
Wave Propagation ◽  
Rock Mass ◽  
Crack Propagation ◽  
Stress Wave ◽  
Large Scale ◽  
Jointed Rock ◽  
In Situ Stress ◽  
Jointed Rock Mass ◽  
Stress Wave Propagation

This paper proposes a large-scale experiment combined with multiple cement mortar blocks to simulate stress wave propagation across a jointed rock mass under unidirectional in situ stress. Two identical mortar block models with smooth, dry, and unfilled joints were poured. The stress waves in Model 1 and Model 2 were generated by an electric spark source and a blast-induced source, respectively. The effects of these two excitation sources on stress wave propagation were compared through crack propagation experiments. The experimental results show that the peak value of the transmitted strain wave decreases as the in situ stress increases. The unidirectional in situ stress has a certain inhibitory effect on the stress wave propagation. It also indicates that for Model 1 with the electric spark source, no cracks on the upper surface, but a Livingstone blasting crater at the bottom is generated. For Model 2 with the blast-induced source, cracks on the upper surface and a blasting crater at the bottom are produced. The results verify the similarity between the electric spark source and the explosive source. The two-dimensional finite element program (ANSYS/LS-DYNA) was applied to further simulate the crack propagation of a jointed rock mass under different in situ stresses. The results of numerical simulation verify that the in situ stress has a clear guiding effect on the crack propagation.

scholarly journals Experimental Evaluation of Shear Behavior of Stone Masonry Wall

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2313
Author(s):  
Maria Luisa Beconcini ◽  
Pietro Croce ◽  
Paolo Formichi ◽  
Filippo Landi ◽  
Benedetta Puccini
Keyword(s):  
Shear Behavior ◽  
Stone Masonry ◽  
Masonry Walls ◽  
Mechanical Parameters ◽  
In Situ Tests ◽  
Capacity Curves ◽  
Historical Structures ◽  
Definition Of

The evaluation of the shear behavior of masonry walls is a first fundamental step for the assessment of existing masonry structures in seismic zones. However, due to the complexity of modelling experimental behavior and the wide variety of masonry types characterizing historical structures, the definition of masonry’s mechanical behavior is still a critical issue. Since the possibility to perform in situ tests is very limited and often conflicting with the needs of preservation, the characterization of shear masonry behavior is generally based on reference values of mechanical properties provided in modern structural codes for recurrent masonry categories. In the paper, a combined test procedure for the experimental characterization of masonry mechanical parameters and the assessment of the shear behavior of masonry walls is presented together with the experimental results obtained on three stone masonry walls. The procedure consists of a combination of three different in situ tests to be performed on the investigated wall. First, a single flat jack test is executed to derive the normal compressive stress acting on the wall. Then a double flat jack test is carried out to estimate the elastic modulus. Finally, the proposed shear test is performed to derive the capacity curve and to estimate the shear modulus and the shear strength. The first results obtained in the experimental campaign carried out by the authors confirm the capability of the proposed methodology to assess the masonry mechanical parameters, reducing the uncertainty affecting the definition of capacity curves of walls and consequently the evaluation of seismic vulnerability of the investigated buildings.

In Situ Tests on Creep Behavior of Rock Mass with Joint or Shearing Zone in Foundation of Large-Scale Hydroelectric Projects

2004 ◽  
Vol 261-263 ◽  
pp. 1097-1102 ◽  
Author(s):  
Jian Liu ◽  
Xia Ting Feng ◽  
Xiu Li Ding ◽  
Huo Ming Zhou
Keyword(s):  
Rock Mass ◽  
Creep Behavior ◽  
Large Scale ◽  
Time Dependent ◽  
Three Gorges Project ◽  
Three Gorges ◽  
The Three Gorges ◽  
The Three Gorges Project

The time-dependent behavior of rock mass, which is generally governed by joints and shearing zones, is of great significance for engineering design and prediction of long-term deformation and stability. In situ creep test is a more effective method than laboratory test in characterizing the creep behavior of rock mass with joint or shearing zone due to the complexity of field conditions. A series of in situ creep tests on granite with joint at the shiplock area of the Three-Gorges Project and basalt with shearing zone at the right abutment of the Xiluodu Project were performed in this study. Based on the test results, the stress-displacement-time responses of the joints and basalt are analyzed, and their time-dependent constitutive model and model coefficients are given, which is crucial for the design to prevent the creep deformations of rock masses from causing the failure of the operation of the shiplock gate at the Three-Gorges Project and long-term stability of the Xiluodu arc dam.

scholarly journals Crack Propagation Behavior of a Ni-Based Single-Crystal Superalloy during In Situ SEM Tensile Test at 1000 °C

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1047
Author(s):  
Wenxiang Jiang ◽  
Xiaoyi Ren ◽  
Jinghao Zhao ◽  
Jianli Zhou ◽  
Jinyao Ma ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Tensile Test ◽  
Single Crystal ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Single Crystal Superalloy ◽  
Propagation Path ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

An in situ scanning electron microscope (SEM) tensile test for Ni-based single-crystal superalloy was carried out at 1000 °C. The stress displacement was obtained, and the yield strength and tensile strength of the superalloy were 699 MPa and 826 MPa, respectively. The crack propagation process, consisting of Model I crack and crystallographic shearing crack, was determined. More interestingly, the crack propagation path and rate affected by eutectics was directly observed and counted. Results show that the coalescence of the primary crack and second microcrack at the interface of a γ/γ′ matrix and eutectics would make the crack propagation rate increase from 0.3 μm/s to 0.4 μm/s. On the other hand, crack deflection decreased the rate to 0.05 μm/s. Moreover, movement of dislocations in front of the crack was also analyzed to explain the different crack propagation behavior in the superalloy.

scholarly journals Fracture in Bulk Amorphous Alloys

1998 ◽  
Vol 554 ◽  
Author(s):  
J. A. Horton ◽  
J. L. Wright ◽  
J. H. Schneibel
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Shear Bands ◽  
Bulk Amorphous Alloy ◽  
In Situ Tem ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Crack Tips ◽  
Temperature Fracture

AbstractThe fracture behavior of a Zr-based bulk amorphous alloy, Zr-10 Al-5 Ti-17.9 Cu-14.6Ni (at.%), was examined by transmission electron microscopy (TEM) and x-ray diffraction forany evidence of crystallization preceding crack propagation. No evidence for crystallizationwas found in shear bands in compression specimens or at the fracture surface in tensile specimens.In- situ TEM deformation experiments were performed to more closely examine actualcrack tip regions. During the in-situ deformation experiment, controlled crack growth occurredto the point where the specimen was approximately 20 μm thick at which point uncontrolledcrack growth occurred. No evidence of any crystallization was found at the crack tips or thecrack flanks. Subsequent scanning microscope examination showed that the uncontrolledcrack growth region exhibited ridges and veins that appeared to have resulted from melting. Performing the deformations, both bulk and in-situ TEM, at liquid nitrogen temperatures (LN2) resulted in an increase in the amount of controlled crack growth. The surface roughness of the bulk regions fractured at LN2 temperatures corresponded with the roughness of the crack propagation observed during the in-situ TEM experiment, suggesting that the smooth-appearing room temperature fracture surfaces may also be a result of localized melting.

Analysis of TBM Tunnel Behavior in Jointed Rock Mass

2011 ◽  
Vol 90-93 ◽  
pp. 2033-2036 ◽  
Author(s):  
Jin Shan Sun ◽  
Hong Jun Guo ◽  
Wen Bo Lu ◽  
Qing Hui Jiang
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Jointed Rock ◽  
In Situ Stress ◽  
Jointed Rock Mass ◽  
Joint Orientation ◽  
Joint Spacing ◽  
Factors Affecting ◽  
Dip Angle

The factors affecting the TBM tunnel behavior in jointed rock mass is investigated. In the numerical models the concrete segment lining of TBM tunnel is concerned, which is simulated as a tube neglecting the segment joint. And the TBM tunnel construction process is simulate considering the excavation and installing of the segment linings. Some cases are analyzed with different joint orientation, joint spacing, joint strength and tunnel depth. The results show that the shape and areas of loosing zones of the tunnel are influenced by the parameters of joint sets and in-situ stress significantly, such as dip angle, spacing, strength, and the in-situ stress statement. And the stress and deformation of the tunnel lining are influenced by the parameters of joint sets and in-situ stress, too.

scholarly journals Timeliness of collinear crack propagation in rock mass

AIP Advances ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 065120
Author(s):  
Min Bao ◽  
Zhonghui Chen ◽  
Zihan Zhou ◽  
Lingfan Zhang ◽  
Jianming Wang
Keyword(s):  
Rock Mass ◽  
Crack Propagation ◽  
Collinear Crack
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