scholarly journals Quality Assessment of Installed Rock Bolts

2021 ◽  
Author(s):  
Andrzej Staniek
Keyword(s):  
Element Model ◽  
Surrounding Rock ◽  
Rock Bolt ◽  
Impact Excitation ◽  
Modal Parameters ◽  
Front Part ◽  
Rock Bolts ◽  
Visible Part ◽  
Additional Equipment ◽  
Non Destructive

The chapter presents a method for non-destructive identification of discontinuity of a resin layer (grout) surrounding rock bolts. The method uses modal analysis procedures and is based on an impact excitation where a response transducer is positioned at a visible part of a rock bolt. Since the installed rock bolt acts as an oscillator, its modal parameters are changed by different lengths and positions of grouting discontinuity. Thanks to proper extraction of these parameters, with a resonant frequency seen as the most valuable, the intended identification is possible. The measurements and analyses were performed in laboratory conditions and subsequently at experimental and working coal mines where the measurement system was verified. The developed finite element model of the system under test, rock bolt - resin - rock mass, may be used as reference data base for investigated rock bolts. The advantages of the method include plausibility of grouting discontinuity assessment at any time after its installation, a non-destructive character of the method and the fact that it is not necessary to install any additional equipment into a roof section. It enables a localization of a grout discontinuity, whether it is the back part or the front part of a rock bolt.

Non-Destructive Testing of Building Objects Positioned in the Area of Coal Exploitation

2012 ◽  
Vol 518 ◽  
pp. 228-237
Author(s):  
Andrzej Staniek
Keyword(s):  
Modal Analysis ◽  
Laser Scanning ◽  
Element Model ◽  
The State ◽  
Point Of View ◽  
Impact Excitation ◽  
Laser Vibrometer ◽  
Building Structures ◽  
Destructive Testing ◽  
Non Destructive

In this paper the results of modal analysis of a four storey building are presented. To excite the investigated structure, impact excitation was applied in two different points located on pillars supporting the building. In order to extract dynamic parameters of the structure, experimental modal analysis was applied. The parameters of vibration resulting from this excitation were measured by a scanning laser vibrometer; additionally piezoelectric accelerometers were utilized. To compare the results and monitor the state of the building a finite element model (FE) was built. It seems that a reliable identification of the state of building structures using a laser scanning vibrometer is feasible and relevant from a practical point of view. To monitor local changes additional piezoelectric accelerometers should be used. Moreover, it is applicable for damage detection to refine theoretical and experimental modal models for each natural frequency and to calculate the stress distribution for each refined model. Consequently, the sum of these particular stresses conveys information for building engineers and enables comparison with their in situ observations. The analysed building is situated on the terrain of underground coal mine exploitation so the aim of the research is not only to observe the state of the building but also to analyse possible changes during the process of excavation and after it was completed.

scholarly journals Studying the performance of fully encapsulated rock bolts with modified structural elements

2021 ◽  
Author(s):  
Jianhang Chen ◽  
Hongbao Zhao ◽  
Fulian He ◽  
Junwen Zhang ◽  
Kangming Tao
Keyword(s):  
Shear Stress ◽  
Load Transfer ◽  
Maximum Shear Stress ◽  
Coupling Model ◽  
Numerical Approach ◽  
Rock Bolt ◽  
Structural Elements ◽  
Rock Bolts ◽  
Two Stage ◽  
Bolt Diameter

AbstractNumerical simulation is a useful tool in investigating the loading performance of rock bolts. The cable structural elements (cableSELs) in FLAC3D are commonly adopted to simulate rock bolts to solve geotechnical issues. In this study, the bonding performance of the interface between the rock bolt and the grout material was simulated with a two-stage shearing coupling model. Furthermore, the FISH language was used to incorporate this two-stage shear coupling model into FLAC3D to modify the current cableSELs. Comparison was performed between numerical and experimental results to confirm that the numerical approach can properly simulate the loading performance of rock bolts. Based on the modified cableSELs, the influence of the bolt diameter on the performance of rock bolts and the shear stress propagation along the interface between the bolt and the grout were studied. The simulation results indicated that the load transfer capacity of rock bolts rose with the rock bolt diameter apparently. With the bolt diameter increasing, the performance of the rock bolting system was likely to change from the ductile behaviour to the brittle behaviour. Moreover, after the rock bolt was loaded, the position where the maximum shear stress occurred was variable. Specifically, with the continuous loading, it shifted from the rock bolt loaded end to the other end.

Weak-Points Diagnosis and Optimization of Shield Machine Cutter Tool Based on Characteristic Parameters

2016 ◽  
Vol 693 ◽  
pp. 1479-1485 ◽  
Author(s):  
Jian Zhao ◽  
Xue Wu Hong ◽  
Ming Yu ◽  
Zhi Peng Gao ◽  
Wen Jin Wang
Keyword(s):  
Finite Element ◽  
Dynamic Characteristics ◽  
Optimization Design ◽  
Weak Link ◽  
Human Life ◽  
Element Model ◽  
Ring Structure ◽  
Modal Parameters ◽  
Underground Engineering ◽  
Shield Machine

Shield machine plays an indispensable role in the mining, transportation, underground engineering, hydraulic engineering and municipal construction. Shield cutters of shield construction process often appears serious deformation, damage that leads to engineering accident, or even a threat to human life and safety. In order to provide high precise data for shield machine cutter tool dynamic modification and to diagnose the shield machine cutter tool fault, the dynamic characteristic of the shield machine cutter tool system, which is the main component of a shield machine cutter tool, has to be obtained precisely. The compute modal parameters identification method base on the finite element method is proposed to identify the modal parameters of the shield machine cutter tool. By means of Solidwords software, the knife ring structure of the shield machine tool and the tool is designed; then build the tool the finite element model, modal analysis, obtained the dynamic characteristics, and find out the weak link, put forward the improvement measures and prolong its life. Therefore, the study on dynamic characteristics of shield machine cutter, for the optimization design of domestic tool, has an important significance improve tool life.

scholarly journals Numerical Study Of The Targeted Energy Transfer Between The Euler-Bernoulli Beam And A Nonlinear Energy Sink

2021 ◽  
Author(s):  
Mohi U. Rahamat Ullah
Keyword(s):  
Energy Transfer ◽  
Primary Structure ◽  
Numerical Study ◽  
Element Model ◽  
Impact Excitation ◽  
Nonlinear Stiffness ◽  
Targeted Energy Transfer ◽  
Stiffness Property ◽  
Energy Sink ◽  
The Impact

Targeted energy transfer (TET) refers to the spatial transfer of energy between a primary structure of interest and isolated oscillators called the energy sink (ES). In this work, the primary structure of interest is a slender beam modeled by the Euler-Bernoulli theory, and the ES is a single-degree-of-freedom oscillator with either linear or cubic nonlinear stiffness property. The objective of this study is to characterize the TET and the effectiveness of ES under impact and periodic excitations. By using the scientific computation package, MATLAB, numerical simulations are carried out based on excitations of various strength and locations. Both time and frequency domain characterizations are used. For the impact excitation, the ES with the cubic nonlinear stiffness property is more superior to the linear oscillator in that larger percentage of the impact energy can be dissipated there. The main energy transfer was found to be due to a 3- to-1 frequency coupling between the first bending mode and the ES. For the periodic excitation, however, both linear and nonlinear ES exhibit generally poorer performance than the case with the impact excitation. Future works should focus on the frequency-energy relationship of the periodic solution of the underlying Hamiltonian, as well as using finite element model to verify the simulation results.

A vibration-based identification of elastic properties of stitched sandwich panels

2018 ◽  
Vol 53 (5) ◽  
pp. 579-592 ◽  
Author(s):  
Nan Li ◽  
Mabrouk Ben Tahar ◽  
Zoheir Aboura ◽  
Kamel Khellil
Keyword(s):  
Elastic Properties ◽  
Transverse Direction ◽  
Sandwich Panel ◽  
Low Cost ◽  
Element Model ◽  
Vibration Test ◽  
Structural Application ◽  
Sensibility Analysis ◽  
The Cost ◽  
Non Destructive

Stitched sandwich becomes popular in structural application owing to its better performance in the transverse direction with respect to classical sandwich structure and relatively low-cost additional stitching process. The identification of its elastic properties is essential for offering a tailored structure for specific applications. A non-destructive identification method based on vibration test is proposed to obtain these parameters. The number of parameters is firstly reduced by a sensibility analysis. The retained parameters are identified by minimizing the cost function which indicates the gap between measured frequencies from vibration test and calculated frequencies from a finite element model. This method is applied to a stitched sandwich panel and its elastic properties are successfully identified.

Finite Element Modeling and Advanced Imaging by Instrumented Tap Testing

1999 ◽  
Author(s):  
V. Dayal ◽  
Tanveer A. Choudhary ◽  
D. K. Hsu ◽  
J. J. Peters ◽  
D. J. Barnard
Keyword(s):  
Finite Element ◽  
Structural Response ◽  
Element Model ◽  
Force Response ◽  
Honeycomb Core ◽  
Advanced Imaging ◽  
Tap Test ◽  
Main Emphasis ◽  
Non Destructive ◽  
Composite Face

Abstract Tap test is a very trusted and well used technique for the non-destructive evaluation of composite materials. Conventionally, a coin has been used for the tapping and the inspector listens to the resulting sound. The more advanced force response provides a number which can be correlated to the damage. A finite element model of the test has been developed with full honeycomb features and a dynamic tap is applied. The goal is to measure the reduction in stiffness of the structure due to simulated defects. This could be useful to both the manufacturer, as well as the user, to know the change in the structural response of the structure for a possible pass/fail criteria. We will also present results of an instrumented tap test with scanner. The main emphasis is on the testing of honeycomb core with composite face sheet panels. The results presented show the sensitivity of the tap test on simulated defects in honeycomb panels.

Fatigue damage in bending of reinforced concrete frames using non-destructive tests for dynamic strength of the cylinder

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Dragan D. Milašinović ◽  
Aleksandar Landović ◽  
Danica Goleš
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Damage ◽  
Cross Section ◽  
Modal Parameters ◽  
The Finite Element Method ◽  
Concrete Frames ◽  
Content Type ◽  
Non Destructive

PurposeThe purpose of this paper is to contribute to the solution of the fatigue damage problem of reinforced concrete frames in bending.Design/methodology/approachThe problem of fatigue damage is formulated based on the rheological–dynamical analogy, including a scalar damage variable to address the reduction of stiffness in strain softening. The modal analysis is used by the finite element method for the determination of modal parameters and resonance stability of the selected frame cross-section. The objectivity of the presented method is verified by numerical examples, predicting the ductility in bending of the frame whose basic mechanical properties were obtained by non-destructive testing systems.FindingsThe modal analysis in the frame of the finite element method is suitable for the determination of modal parameters and resonance stability of the selected frame cross-section. It is recommended that the modulus of elasticity be determined by non-destructive methods, e.g. from the acoustic response.Originality/valueThe paper presents a novel method of solving the ductility in bending taking into account both the creep coefficient and the aging coefficient. The rheological-dynamical analogy (RDA) method uses the resonant method to find material properties. The characterization of the structural damping via the damping ratio is original and effective.

scholarly journals An Improved Numerical Simulation Approach for the Failure of Rock Bolts Subjected to Tensile Load in Deep Roadway

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-21
Author(s):  
Rui Wang ◽  
Jian-biao Bai ◽  
Shuai Yan ◽  
Yuan-ba Song ◽  
Guang-dong Wang
Keyword(s):  
Numerical Simulation ◽  
Tensile Load ◽  
Elongation Rate ◽  
Original Model ◽  
Rock Bolt ◽  
Tensile Failure ◽  
Simulation Approach ◽  
Rock Bolts ◽  
Modified Model ◽  
Free Section

Our goal was to develop an effective research tool for roadways with significant deformations supported by rock bolts. The improved numerical simulation approach is constructed through additional development of FLAC3D. The aim is to modify the shortcoming that the original model in FLAC3D regards the plastic tensile strain of any arbitrary rock bolt element node as the rupture discrimination criterion. The FISH programming language is adopted to conduct the secondary development and to embed the revised model into the main program of FLAC3D. Taking an actual mining roadway as the simulation object, two simulation schemes adopting the newly improved approach and the original method were conducted, respectively. The results show that (1) the PILE element that constitutes the rock bolt-free section with the maximum elongation rate ruptures after modification, while the rock bolt tendon elongation rate reaches beyond the predefined tensile rupture elongation rate; (2) the modified model in which the rock bolt is mainly subjected to tension realises the tensile rupture phenomenon at the end of the rock bolt-free section and the rock bolt at the junction between the free section and the anchoring section; and (3) only four rock bolts that are in the roadway sides showed rupture in the modified model, and all rock bolts showed rupture in the original model. The tensile failure of the rock bolt led that the modified model scheme is closer to the actual. Compared with the modified model, in the original model, deformation of the surrounding rock masses is severe. This is resulted by the rupture of all rock bolts in the original model. The analysis shows that the improved numerical simulation approach is much more reliable for large deformation roadway behavior with rock bolt support.

scholarly journals Primary Investigation on Equivalent Anchoring Method of Jointed Rock Mass Tunnel and Its Engineering Application

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Min Gao ◽  
Shanpo Jia
Keyword(s):  
Rock Mass ◽  
Three Dimensional ◽  
Engineering Application ◽  
Friction Angle ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Rock Masses ◽  
Reinforcement Effect ◽  
Rock Bolts

Rock bolts, one of the main support structures of the tunnel, can improve the stress state and mechanical properties of the surrounding rocks. The rock bolts are simulated by bar or beam elements in present numerical calculations for most 2D tunnel models. However, the methods of simulating rock bolt in three-dimensional models are rarely studied. Moreover, there are too many rock bolts in the long-span tunnel, which are hardly applied in the 3D numerical model. Therefore, an equivalent anchoring method for bolted rock masses needs to be further investigated. First, the jointed material model is modified to simulate the anisotropic properties of surrounding rock masses. Then, based on the theoretical analysis of rock bolts in reinforcing mechanical properties of the surrounding rock masses, the equivalent anchoring method of the jointed rock mass tunnel is numerically studied. The equivalent anchoring method is applied to the stability analysis of a diversion tunnel in Western China. From the calculation results, it could be found that the reinforcement effect of rock bolts could be equivalently simulated by increasing the mechanical parameter value of surrounding rocks. For the jointed rock mass tunnel, the cohesion and internal friction angle of the surrounding rocks are improved as 1.7 times and 1.2 times of the initial value, which can simulate the reinforcement effect of rock bolts. Comparing with analytical results, the improved internal friction angle is nearly consistent with analytical result. The reinforcement effect of rock bolts is simulated obviously when the mechanical parameters of surrounding rocks are increased simultaneously. The engineering application shows that the equivalent anchoring method can reasonably simulate the effect of rock bolts, which can provide reference for stability analysis of three-dimensional tunnel simulations.

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