Blast Induced Damage Due to Repeated Vibrations in Jointed Gneiss Rock Formation

2012 ◽  
pp. 135-159
Author(s):  
M. Ramulu ◽  
T. G. Sitharam
Keyword(s):  
Rock Mass ◽  
Dynamic Loading ◽  
Seismic Waves ◽  
Damage Zone ◽  
Research Work ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Rock Blasting ◽  
Hydroelectric Power ◽  
Blast Vibrations

Blasting is the most common method of rock excavation technique in mining and civil construction and infrastructure projects. Rock blasting produces seismic waves similar to those produced by earthquakes, but with relatively high frequency and low amplitude. General blast induced damage was extensively studied by researchers globally, but the studies on damage due to repeated blast vibrations is not yet reported, quantitatively, on underground openings. This paper deals with the research work carried on the effect of repeated dynamic loading imparted on the jointed rock mass from subsequent blasts in the vicinity, on the jointed rock mass at Lohari Nag Pala Hydroelectric Power Construction Project. The blast induced damage was monitored by borehole extensometers, borehole camera inspection surveys and triaxial geophones installed at three test sites of different joint orientations at the Main Access Tunnel of power house. The study reveals that there was extra damage of 60%, exclusively due to repeated blast vibrations. The results of the study indicate that repeated dynamic loading, resulted in damage even at 33% of the conventional damage threshold vibrations (Vc) in case of favorable joint orientations and 23% of Vc in case of unfavorable joints. The paper concludes in quantification of effect of repeated blast loading and the orientation of joints on the extension of damage zone in jointed rock mass of underground excavations.

Blast Induced Damage Due to Repeated Vibrations in Jointed Gneiss Rock Formation

2010 ◽  
Vol 1 (1) ◽  
pp. 110-134 ◽  
Author(s):  
M. Ramulu ◽  
T. G. Sitharam
Keyword(s):  
Rock Mass ◽  
Dynamic Loading ◽  
Seismic Waves ◽  
Damage Zone ◽  
Research Work ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Rock Blasting ◽  
Hydroelectric Power ◽  
Blast Vibrations

Blasting is the most common method of rock excavation technique in mining and civil construction and infrastructure projects. Rock blasting produces seismic waves similar to those produced by earthquakes, but with relatively high frequency and low amplitude. General blast induced damage was extensively studied by researchers globally, but the studies on damage due to repeated blast vibrations is not yet reported, quantitatively, on underground openings. This paper deals with the research work carried on the effect of repeated dynamic loading imparted on the jointed rock mass from subsequent blasts in the vicinity, on the jointed rock mass at Lohari Nag Pala Hydroelectric Power Construction Project. The blast induced damage was monitored by borehole extensometers, borehole camera inspection surveys and triaxial geophones installed at three test sites of different joint orientations at the Main Access Tunnel of power house. The study reveals that there was extra damage of 60%, exclusively due to repeated blast vibrations. The results of the study indicate that repeated dynamic loading, resulted in damage even at 33% of the conventional damage threshold vibrations (Vc) in case of favorable joint orientations and 23% of Vc in case of unfavorable joints. The paper concludes in quantification of effect of repeated blast loading and the orientation of joints on the extension of damage zone in jointed rock mass of underground excavations.

Effect of Repeated Blast Vibrations on Rock Mass Damage in Tunnels

2018 ◽  
pp. 215-244
Author(s):  
Ramulu More ◽  
T. G. Sitharam
Keyword(s):  
Rock Mass ◽  
Dynamic Loading ◽  
Research Work ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Common Method ◽  
Hydroelectric Power ◽  
Power Construction ◽  
Borehole Camera ◽  
Blast Vibrations

Blasting is the most common method of rock excavation technique in mining and civil construction and infrastructure projects. General blast-induced damage was extensively studied globally, but the studies on repeated blast induced damage is not yet reported, quantitatively. This chapter deals with the research work carried on the effect of repeated dynamic loading imparted on the jointed rock mass from subsequent blasts in the vicinity, on the jointed rock mass at Lohari Nag Pala Hydroelectric Power Construction Project. The blast-induced damage was monitored by borehole extensometers, borehole camera inspection surveys and triaxial geophones installed at three test sites of different joint orientations at the Main Access Tunnel of power house. The study reveals that the repeated blast vibrations resulted in extra damage of 60%. The results of the study indicate that repeated vibrations, resulted in inducing damage even at 23-33% of the critical vibrations (Vc) levels.

scholarly journals The Method of Determining Excavation Damaged Zone by Acoustic Test and the Application in Engineering Cases

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Qian-Cheng Sun ◽  
Hao-Sen Guo ◽  
Zhi-Hua Xu ◽  
Yue Liu ◽  
Xiao Xu
Keyword(s):  
Rock Mass ◽  
Damage Evolution ◽  
Hard Rock ◽  
Damage Zone ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Excavation Damaged Zone ◽  
Damaged Zone ◽  
Columnar Jointed Rock Mass

It is very important to accurately determine the depth of excavation damaged zone for underground engineering excavation and surrounding rock stability evaluation, and it can be measured by acoustic test, but there is no quantitative method for analysis of the results, and it relies heavily on the experience of engineers, which leads to the low reliability of the results and also limits the application of the acoustic method. According to substantial field test data and the feedback of surrounding rock support parameters, the boundary method is proposed to determine the depth of excavation damaged zone in surrounding rock based on the relation between the ultrasonic velocity of measured point and the background wave velocity of rock mass. When the method is applied to the columnar jointed rock mass of Baihetan and the deep-buried hard rock of Jinping, the excavation damaged zone was well judged. The results in the Baihetan project show that the proposed method of determining excavation damage zone by the acoustic test can well demonstrate the anisotropy characteristics of the columnar jointed rock mass, and the damage evolution characteristics of jointed rock mass at the same position can also be obtained accurately. Moreover, the method also can accurately reveal the damage evolution process of the deep-buried hard rock under the condition of high ground stress, which proved the applicability of this method in jointed or nonjointed rock masses.

scholarly journals Study of the Failure Mode of a Jointed Rock Mass due to a Stress Wave

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xi Kun Qian ◽  
Cong Cong Li
Keyword(s):  
Rock Mass ◽  
Failure Mode ◽  
Dynamic Loading ◽  
Stress Wave ◽  
Static Loading ◽  
Failure Process ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Dynamic Failure ◽  
Shear Cracks

The mechanical response and failure process of a jointed rock mass subjected to dynamic loading is very important for the safety and stability of rock engineering projects. In this study, we use RFPA2D-Dynamic, a rock dynamic failure process analysis platform, to establish a two-dimensional impact model of a jointed rock mass to analyze the mechanism of crack propagation in a jointed rock mass with preexisting cracks under dynamic loading. We discuss the influence of the stress wavelength and precrack inclination on the dynamic failure process and mode of the rock mass and compare this failure process with the failure model under static loading. The results show that the dynamic failure process and crack initiation type of a jointed rock mass are closely related to the stress wavelength. For a given peak, as the stress wavelength increases, the failure mode changes from local cracking that occurs above the precracks to a global instability caused by wing cracks. Meanwhile, as the wavelength increases, the shear cracks and mixed tensile-shear cracks generated at the two ends of the precracks are replaced by tensile cracks. The precrack inclination on a jointed rock mass mainly affects the strength of the jointed rock mass and the final failure mode. Specifically, when the joint inclination is small, the rock mass is severely damaged in the region above the precracks because the stress wave forms a region of cracks with a concentrated distribution. As the joint inclination increases, the damaged region becomes larger while the rock mass is less prone to failure; the strength of the rock mass gradually increases, and the wing cracks produced at the two ends of precracks propagate toward the upper and lower ends of the rock mass. However, when the stress wavelength is small, the precracks of different inclinations form cracks in the region above the precracks with a length similar to the precracks. For this condition, the propagation of the cracks is mainly controlled by the stress wavelength, while the influence of the inclination of the precracks is not significant. There is a significant difference between the failure modes of a rock specimen under dynamic loading or static loading because the stress wave produces a reflected tension wave in the direction parallel to the wave attack of the joint plane, which leads to spalling, while the wing cracks are more likely to occur under static loading.

scholarly journals Fracture Behavior of Rock with Initial Damage: Theoretical, Experimental, and Numerical Investigations

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Hui Zhang ◽  
Panpan Guo ◽  
Yixian Wang ◽  
Yanlin Zhao ◽  
Hang Lin ◽  
...  
Keyword(s):  
Rock Mass ◽  
Fracture Behavior ◽  
Research Work ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Future Research ◽  
Fracture Characteristics ◽  
Failure Characteristics ◽  
Initial Damage

Geomaterials such as rock mass often have initial damage under the influence of long-term geological action and hydration corrosion environment. The initial damage affects the integrity and stability of the rock mass, resulting in a difference in the mechanical properties of jointed rock mass and intact one. Therefore, the study of the fracture and failure characteristics of the jointed rock mass is of great significance. Most of the previous researches into the fracture behavior of rock with initial damage are based on model testing, theoretical analysis, and numerical simulation of rock mass with preexisting flaws. This review concentrates on the theoretical, experimental, and numerical efforts that have been devoted to the fracture characteristics of rock or rock-like specimens with preexisting flaws under compression. Some suggestions on the future research work in this field are also given.

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