scholarly journals Numerical Study on the Mechanism and Application of Artificial Free Surfaces in Bedrock Blasting of Shield Tunnels

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Yanjun Qi ◽  
Linming Dou ◽  
Zhaoxing Dong ◽  
Zheng Jiang ◽  
Bo Meng ◽  
...  
Keyword(s):  
Free Surface ◽  
Stress Wave ◽  
Effective Stress ◽  
Peak Velocity ◽  
Stress Waves ◽  
Shield Tunnel ◽  
Reduction Degree ◽  
Free Face ◽  
Surface Particle ◽  
The Impact

During the pretreatment construction of blasting in shield tunnel bedrock, in order to reduce the impact of blasting vibration on the surrounding environment and improve the effect of rock blasting, the method of creating an artificial free surface is proposed. From the point of creating an artificial free surface, this paper numerically studies the function mechanism and parameter optimization of artificial free faces in shield tunnel bedrock blasting construction. The propagation characteristics of explosion stress waves at the interface between the rock and the artificial free face and the effect of the artificial free face on the shield tunnel bedrock blasting were analyzed. The results indicate that, as the explosion stress wave transmits to the artificial free face, a part of the stress wave is reflected back to the bedrock, increasing the energy in the bedrock that needs blasting and improving the blasting effect and utilization rate of the blasting energy. The reduction degree of the peak velocity of the surface particle is more than 50%, and the reduction degree of the peak velocity of the particle near the artificial free face is more than 77%. The existence of the artificial free face reflects the stress wave and superimposes with the original stress waves, increasing the effective stress in the blasting area, and the effective stress can be increased by 5 MPa or more. The peak vibration velocity of the surface particle decreases with an increasing diameter of the empty holes and the distance between the empty holes and the blasting holes. The parameter design value of the artificial free face is put forward: the diameter of the hole is 200 mm, the distance between the empty holes and the center of the blasting holes is 60 cm, and the depth of the empty hole is the same as the blasting hole.

THE REDUCTION OF STRESS WAVE PROPAGATION THROUGH POROUS MATERIALS

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1215-1220
Author(s):  
SOTO AKI KIDA ◽  
KEITA FUKUSHIMA ◽  
MASAYA MATSUMOTO
Keyword(s):  
Porous Medium ◽  
Porous Materials ◽  
Stress Wave ◽  
Acrylic Resin ◽  
Wave Theory ◽  
Stress Waves ◽  
Stress Wave Propagation ◽  
Impact Stress ◽  
The Impact ◽  
Impact Stress Wave

Impact stress wave propagating through porous materials is investigated in order to examine the ability of the shock absorbing effect. The specimens are modeled as the porous medium with different porous diameters made of the acrylic resin plate. When these models are impacted with different impact velocities, the impact stress waves propagating before and after the porous parts are measured using the strain gages in the experiments. As the reduction effect of the impact stress wave propagating in the porous medium, we pay attention to the maximum stresses and the duration times from the histories of the impact stress waves. One-dimensional wave theory and dynamic element method simulated this model are applied in order to explain these phenomena.

scholarly journals Measurement of Stress Waves Propagation in Percussive Drilling

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3677
Author(s):  
Diego Scaccabarozzi ◽  
Bortolino Saggin
Keyword(s):  
Stress Wave ◽  
Axial Stress ◽  
Element Model ◽  
Stress Waves ◽  
Stress Wave Propagation ◽  
Drill Bit ◽  
Torsional Vibrations ◽  
Flexural Stress ◽  
Percussive Drilling ◽  
The Impact

This work describes the results of a test campaign aimed to measure the propagation of longitudinal, torsional, and flexural stress waves on a drill bit during percussive rock drilling. Although the stress wave propagation during percussive drilling has been extensively modeled and studied in the literature, its experimental characterization is poorly documented and generally limited to the detection of the longitudinal stress waves. The activity was performed under continuous drilling while varying three parameters, the type of concrete, the operator feeding force, and the drilling hammer rotational speed. It was found that axial stress wave frequencies and spectral amplitudes depend on the investigated parameters. Moreover, a relevant coupling between axial and torsional vibrations was evidenced, while negligible contribution was found from the bending modes. A finite element model of the drill bit and percussive element was developed to simulate the impact and the coupling between axial and torsional vibrations. A strong correlation was found between computed and measured axial stress spectra, but additional studies are required to achieve a satisfactory agreement between the measured and the simulated torque vibrations.

Impact Load Buffering Method Based on Stress Wave Attenuation Principle

2019 ◽  
Vol 11 (02) ◽  
pp. 1950019 ◽  
Author(s):  
Lin Gan ◽  
He Zhang ◽  
Cheng Zhou ◽  
Lin Liu
Keyword(s):  
Stress Wave ◽  
Wave Attenuation ◽  
Impact Load ◽  
Dynamics Simulation ◽  
Scanning System ◽  
Isolation Method ◽  
Element Analysis ◽  
System A ◽  
High Emission ◽  
The Impact

Rotating scanning motor is the important component of synchronous scanning laser fuze. High emission overload environment in the conventional ammunition has a serious impact on the reliability of the motor. Based on the theory that the buffer pad can attenuate the impact stress wave, a new motor buffering Isolation Method is proposed. The dynamical model of the new buffering isolation structure is established by ANSYS infinite element analysis software to do the nonlinear impact dynamics simulation of rotating scanning motor. The effectiveness of Buffering Isolation using different materials is comparatively analyzed. Finally, the Macht hammer impact experiment is done, the results show that in the experience of the 70,000[Formula: see text]g impact acceleration, the new buffering Isolation method can reduce the impact load about 15 times, which can effectively alleviate the plastic deformation of rotational scanning motor and improve the reliability of synchronization scanning system. A new method and theoretical basis of anti-high overload research for Laser Fuze is presented.

Impact of Double-O-Tube Shield Tunnel Construction on Grillage Beams Foundation Frame Building

2011 ◽  
Vol 71-78 ◽  
pp. 32-36 ◽  
Author(s):  
Xin Jiang Wei ◽  
Jie Hong ◽  
Gang Wei
Keyword(s):  
Principal Stress ◽  
Differential Settlement ◽  
Shield Tunnel ◽  
Tunnel Construction ◽  
Foundation Settlement ◽  
Ground Settlement ◽  
Shield Tunneling ◽  
Frame Building ◽  
Shield Machine ◽  
The Impact

Considering the interaction of building-soil-tunnel, the grillage beams foundation frame building vertical crossed by Double-O-Tube (DOT) shield tunnel was simulated by 3D MIDAS/ GTS software, and the impact of construction on the building was analyzed. The results show that: the ground settlement trough caused by DOT shield tunnel can be fitted by peck formula; during the passage of the shield tunneling through the building, the settlement of the building increased and settlement trough was wilder; the settlement was stable and had a little rebound when shield machine already passed the building; with the increase of driving distance, the first principal stress P1 increased and then was stable; with the increase of L, the shape of foundation settlement curve changed, and the maximum differential settlement between columns increased but was small.

Numerical Investigation of Focused Waves and Their Interaction With a Vertical Cylinder Using REEF3D

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Hans Bihs ◽  
Mayilvahanan Alagan Chella ◽  
Arun Kamath ◽  
Øivind Asgeir Arntsen
Keyword(s):  
Free Surface ◽  
Stokes Equations ◽  
Free Surface Flows ◽  
Surface Elevation ◽  
Numerical Wave Tank ◽  
Free Surface Elevation ◽  
Wave Tank ◽  
Numerical Wave ◽  
Focused Wave ◽  
The Impact

For the stability of offshore structures, such as offshore wind foundations, extreme wave conditions need to be taken into account. Waves from extreme events are critical from the design perspective. In a numerical wave tank, extreme waves can be modeled using focused waves. Here, linear waves are generated from a wave spectrum. The wave crests of the generated waves coincide at a preselected location and time. Focused wave generation is implemented in the numerical wave tank module of REEF3D, which has been extensively and successfully tested for various wave hydrodynamics and wave–structure interaction problems in particular and for free surface flows in general. The open-source computational fluid dynamics (CFD) code REEF3D solves the three-dimensional Navier–Stokes equations on a staggered Cartesian grid. Higher order numerical schemes are used for time and spatial discretization. For the interface capturing, the level set method is selected. In order to test the generated waves, the time series of the free surface elevation are compared with experimental benchmark cases. The numerically simulated free surface elevation shows good agreement with experimental data. In further computations, the impact of the focused waves on a vertical circular cylinder is investigated. A breaking focused wave is simulated and the associated kinematics is investigated. Free surface flow features during the interaction of nonbreaking focused waves with a cylinder and during the breaking process of a focused wave are also investigated along with the numerically captured free surface.

Numerical Simulation of the Impact between the Front-End-Coated Projectile and the Substrate Coated by Ceramic Film

2012 ◽  
Vol 226-228 ◽  
pp. 2198-2202
Author(s):  
Zhi Lin Wu ◽  
Xiao Mei Wang
Keyword(s):  
Normal Stress ◽  
Tangential Stress ◽  
Stress Wave ◽  
Acoustic Impedance ◽  
Axial Direction ◽  
Interfacial Stress ◽  
Ceramic Film ◽  
Front End ◽  
Ceramic Films ◽  
The Impact

The propagation of the stress wave in axial direction during the impact between the front-end-coated projectile and the substrate coated by ceramic films is described by the stress wave theorem. The impact process is numerically simulated by ANSYS/LS-DYNA, where the shell unit is used for precision. The effects of thickness of the front-end coating on the interfacial stress are discussed in detail. Dependence of different ceramic films are also considered. Simulation results show that interfacial normal stress is much greater than tangential stress. The interfacial normal stress is greatest when the thickness of the projectile coating is 0.2 mm. The interfacial tangential stress increases slightly as the thickness of coating increases. Similar stress history in the interface occurs when the acoustic impedance of the films are close. Greater acoustic impedance results in smaller stress.

The Influence of Underpass on Surface Subsidence Caused by Double-Tube Shield Tunneling

2014 ◽  
Vol 915-916 ◽  
pp. 108-113
Author(s):  
Wei Kai Zong
Keyword(s):  
Simulation Method ◽  
Surface Subsidence ◽  
Channel Width ◽  
Ground Movement ◽  
Shield Tunnel ◽  
Underground Structures ◽  
Shield Tunneling ◽  
Underground Channel ◽  
Underground Passage ◽  
The Impact

Shield construction will cause surface subsidence, and the presence of underground structures above the tunnel has an impact on surface subsidence. Based on this, with the engineering of undercross shield tunnel construction on railway station as background, used numerical simulation method to analyze the effect of surface subsidence of underground passage, and studied the influence of depth and width of underpasses on ground movement induced. The results show that: The impact of the underground passage to the wire surface subsidence caused by the shield cannot be ignored. Surface subsidence caused by double shield will be decreased because of the existence of the underground passage, and that related to the channel depth and width. The greater the depth of underground channel, the greater the surface subsidence; greater the underground channel width, the smaller surface subsidence. Meanwhile, the surface subsidence trough width and the largest settlement scope unrelated to the depth of underground tunnels but the underground channel width, and increases with the increasing of the underpass width.

Propagation velocity model of stress waves in larch wood (Larix gmelinii) three-dimensional space with different moisture contents

BioResources ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 6680-6695
Author(s):  
Xiwen Wei ◽  
Liping Sun ◽  
Hongjv Zhou ◽  
Yang Yang ◽  
Yifan Wang ◽  
...  
Keyword(s):  
Moisture Content ◽  
Wave Velocity ◽  
Stress Wave ◽  
Propagation Velocity ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Stress Waves ◽  
Moisture Contents ◽  
Direction Angle ◽  
Stress Wave Velocity

Based on the effects of stress wave propagation in larch (Larix gmelinii) wood, the propagation mechanism of stress wave was explored, and a theoretical model of the propagation velocity of stress waves in the three-dimensional space of wood was developed. The cross and longitudinal propagation velocities of stress wave were measured in larch wood under different moisture contents (46% to 87%, 56% to 96%, 20% to 62%, and 11% to 30%) in a laboratory setting. The relationships between the propagation velocity of stress waves and the direction angle or chord angle with different moisture contents were analyzed, and the three-dimensional regression models among four parameters were established. The analysis results indicated that under the same moisture content, stress wave velocity increased as the direction angle increased and decreased as chord angle increased, and the radial velocity was the largest. Under different moisture contents, stress wave velocity gradually decreased as moisture content increased, and the stress wave velocity was more noticeably affected by moisture content when moisture content was below the fiber saturation point (FSP, 30%). The nonlinear regression models of the direction angle, chord angle, moisture content, and the propagation velocity of stress wave fit the experiment data well (R2 ≥ 0.97).

Rails Deformation Pattern in Frontal Impact

2002 ◽  
Author(s):  
Joseph Hassan ◽  
Guy Nusholtz ◽  
Ke Ding
Keyword(s):  
Wave Propagation ◽  
Real World ◽  
Stress Waves ◽  
Stress Wave Propagation ◽  
Deformation Pattern ◽  
Frontal Impact ◽  
Rigid Barrier ◽  
Final Deformation ◽  
Deformation Patterns ◽  
The Impact

During a vehicle crash stress waves can be generated at the impact point and propagate through the vehicle structure. The generation of these waves is dependent, in general, on the crash type and, in particular, on the impact contact characteristics. This has consequences with respect to different crash barrier interfaces for vehicle evaluation. The two barriers most commonly used to evaluate the response of a vehicle in a frontal impact are the rigid barrier and the offset deformable barrier. They constitute different crash modes, full frontal and offset. Consequently it would be expected that there are different deformation patterns between the two. However, an additional possible contributor to the difference is that an impact into a rigid barrier generates waves of significantly greater stress than impacts with the deformable one. If stress waves are a significant component of real world final deformation patterns then, the choice of barrier interface and its effective stiffness is critical. To evaluate this conjecture, models of two types of rails each undergoing two different types of impacts, are analyzed using an explicit dynamic finite element code. Results show that the energy perturbation along the rail depends on the barrier type and that the early phase of wave propagation has very little effect on the final deformation pattern. This implies that in the real world conditions, the stress wave propagation along the rail has very little effect on the final deformed shape of the rail.

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