It is still a challenge to accurately evaluate the structural safety of tunnel during the process of construction. To address this issue, a safety evaluation approach of tunnel based on the monitoring data during construction is proposed in this study. Firstly, the detailed description of modelling the tunnel excavation, releasing the load acting on the tunnel, and selecting the constitutive relationship of surrounding rock of tunnel is introduced. Secondly, aiming at an actual shallow-buried tunnel with underground excavation, utilizing the analytical results of deformation of tunnel, the structural safety of tunnel is evaluated by using a reliability-based method. Finally, the effectiveness of the proposed method is demonstrated by using the dynamic monitoring data obtained during the construction of an actual tunnel.

Xiaokun Yan

Hu Li

Feng Liu

Yang Liu

Structural Safety Evaluation of Tunnel Based on the Dynamic Monitoring Data during Construction

The High-Luminosity Large Hadron Collider upgrade at CERN will result in an increase in the energy stored in the circulating particle beams, making it necessary to assess the thermomechanical performance of currently used and newly developed materials for use in beam intercepting devices such as collimators and absorbers. This study describes the thermomechanical characterisation of a novel copper diamond grade selected for use in tertiary collimators of the HL-LHC. The data obtained are used to build an elastoplastic material model and implemented in numerical simulations performed to benchmark experimental data obtained from the recently completed MultiMat experiment conducted at CERN&#x2019;s HiRadMat facility, where various materials shaped as slender rods were tested under particle beam impact. The analyses focus on the dynamic longitudinal and flexural response of the material, with results showing that the material model is capable of replicating the material behaviour to a satisfactory level in both thermal and structural domains, accurately matching experimental measurements in terms of temperature, frequency content, and amplitude.

Marcus Portelli

Michele Pasquali

Federico Carra

Alessandro Bertarelli

Pierluigi Mollicone

Nicholas Sammut

&#xd3;scar Sacrist&#xe1;n de Frutos

Jorge Guardia Valenzuela

Erich Neubauer

Michael Kitzmantel

David Grech

Thermomechanical Characterisation of Copper Diamond and Benchmarking with the MultiMat Experiment

To reduce the vibration of a cantilever steel plate in high-temperature environments (25&#xb0;C&#x2013;500&#xb0;C), a new composite structure with entangled metallic wire material (EMWM) core was proposed. The damping performance of the EMWM under different temperatures was investigated. The results show that when the temperature does not exceed 260&#xb0;C, the damping property of the EMWM is not affected by temperature. When the temperature exceeds 260&#xb0;C, the damping property of the EMWM decreases with the increase of temperature. A thermal-vibration joint test system was set up to verify the energy dissipation mechanism of the composite structure with EMWM core and to research the effect of vibration reduction under different temperatures. The displacement deviation between the baseplate (steel plate) and constraining plate was sufficient to cause frictional energy dissipation of the EMWM core. The thermal-vibration joint test results indicated that the EMWM core had a positive impact on the damping properties of the cantilever structure. Adding EMWM core and constraining plate can significantly increase the damping ratio and reduces the vibration of the cantilever structures under different temperatures. This research is helpful to control the structural vibrations of cantilever structures in high-temperature environments.

Di Jia

Fuhao Peng

Tao Zhou

Xueren Wang

Qingliang Lu

Yiwan Wu

Experimental Research on Vibration Reduction of Cantilever Structure in High-Temperature Environments

Inadequate blade angle adjustment or manufacturing errors will cause inconsistencies in the blade angle of an axial-flow pump. In this study, the hydrodynamic characteristics of an axial-flow pump with inconsistent blade angle are investigated by analyzing hydraulic performance and pressure pulsation. The analysis is conducted by performing a numerical simulation combined with a model test. Results show that, relative to the case without blade angle deviation, the case with blade angle deviation exhibits changes in the periodicity of the flow field in the impeller. Such changes result in uneven pressure changes in the impeller passage. The pressure pulsation induced by the blade angle deviation is mainly low-frequency pulsation; that is, it is twice the rotation frequency. The amplitude of the main frequency pulsation is 1.5&#x2013;3 times that of the blade without angle deviation. This low frequency that dominates the whole pump device easily causes the vibration and weakens the safety and stability of the pump. The blade angle deviation exerts great influence on the unsteady characteristics. Hence, blade angle deviation seriously affects the safe and stable operation of axial-flow pumps and pump stations.

Lijian Shi

Jun Zhu

Yao Yuan

Fangping Tang

Penglan Huang

Wenpeng Zhang

Haiyu Liu

Xiaowen Zhang

Numerical Simulation and Experiment of the Effects of Blade Angle Deviation on the Hydraulic Characteristics and Pressure Pulsation of an Axial-Flow Pump

The top coal weakening process is an effective mean to increase the coal output, reduce the coal resource waste, and promote the sustainable development in a mine. The conventional blast weakening process and water injection weakening process are more widely applied in fully mechanized caving mining of hard thick coal seams, but under some special complex geological conditions, no desirable performance has been achieved in top coal weakening by one weakening process alone after substantial investment in capital and equipment. In the context of highly tough top coal with partings at working face 110501 for fully mechanized top coal caving mining in Yushutian Coal Mine, effects of parting band and high toughness on top coal breaking were studied in terms of mechanism and extent, a multifunctional compound drilling field integrating blast weakening, water injection weakening, and gas extraction was purposefully designed, and a cyclic top coal weakening process for highly tough coal seams with partings was proposed. Engineering practice and performance testing show that degree of fragmentation and mobility of top coal was improved, mean top coal recovery ratio at the working face increased by about 35&#x0025;, coal resource waste decreased, and potential risks of gas explosion and mine fire were eliminated, which provides reference for top coal weakening process under similarly complex engineering conditions.

Zhaopeng Wu

Junhui Wang

Zhijun Wan

Jingyi Cheng

Luchang Xiong

Lizhu Zhao

Xiaogang Liu

A Case Study of Cyclic Top Coal Weakening Process Based on Highly Tough Coal Seam with Partings

The purpose of this paper is to study the crack initiation, propagation, and coalescence of the sandy mudstone sample with two sets of prefabricated cross-flaws under uniaxial compression. This study is different from previous studies on single or multiple parallel prefabricated flaws. The prefabricated cross-flaws are characterized by the dip of the rock bridge with the direction of the main flaw (<span class="nowrap"><svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42947pt" id="M1" height="12.7178pt" version="1.1" viewBox="-0.0498162 -9.28833 7.68094 12.7178" width="7.68094pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><path id="g113-224" d="M558 587C558 666 497 712 432 712C379 712 330 691 284 650C212 586 178 508 148 348L71 -65C49 -185 35 -229 23 -235L27 -261C49 -259 101 -251 124 -224C131 -216 138 -178 159 -24C171 66 197 200 227 356C264 550 295 668 393 668C443 668 479 632 479 575C479 516 446 458 383 418C361 404 344 398 318 397L296 350C395 338 460 281 460 192C460 110 411 40 300 40C258 40 215 55 192 69L181 51C191 18 222 -16 266 -16C308 -16 351 1 397 26C471 67 545 142 545 221C545 315 486 365 401 395C469 437 558 498 558 587Z"/></g></svg>)</span> and the angle between the direction of main and minor flaws (<span class="nowrap"><svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42943pt" id="M2" height="9.39034pt" version="1.1" viewBox="-0.0498162 -5.96091 6.63704 9.39034" width="6.63704pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><path id="g113-225" d="M478 372C478 418 458 448 431 448C409 448 389 431 389 410C389 404 391 400 394 395C398 388 406 371 406 348C406 253 308 122 251 51H249C254 122 249 257 231 336C212 421 189 448 159 448C126 448 75 412 23 327L48 306C83 354 103 371 115 371C125 371 134 360 144 334C185 224 192 64 183 -19C146 -100 116 -202 110 -244L125 -261C154 -259 208 -234 222 -220C222 -194 225 -84 235 -23C247 -3 273 36 308 79C379 165 478 288 478 372Z"/></g></svg>).</span> The effects of these two parameters on crack initiation, propagation, coalescence, crack initiation stress, and coalescence stress are analyzed. Moreover, numerical simulation of the uniaxial compression experiments is performed using PFC2D with a flat-joint model, and the simulation results are in good agreement with those from the experiments. The results demonstrate that the dip angle of the rock bridge with the direction of the main flaw (<span class="nowrap"><svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42947pt" id="M3" height="12.7178pt" version="1.1" viewBox="-0.0498162 -9.28833 7.68094 12.7178" width="7.68094pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><use xlink:href="#g113-224"/></g></svg>)</span> has strong effects on the crack initiation and coalescence stresses. The larger the angle between the direction of main and minor flaws <span class="nowrap"><svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42947pt" id="M4" height="12.7178pt" version="1.1" viewBox="-0.0498162 -9.28833 15.6668 12.7178" width="15.6668pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><path id="g113-41" d="M300 -147C201 -63 143 98 143 270S200 602 300 686L282 710C136 610 70 450 70 271V270C70 89 136 -72 282 -170L300 -147Z"/></g><g transform="matrix(.013,0,0,-0.013,4.498,0)"><use xlink:href="#g113-225"/></g><g transform="matrix(.013,0,0,-0.013,11.014,0)"><path id="g113-42" d="M275 270C275 450 212 609 64 710L45 686C145 604 203 442 203 270S147 -63 45 -147L64 -170C213 -68 275 89 275 270Z"/></g></svg>,</span> the greater the crack initiation and coalescence stresses. The crack initiation stress is reduced for the case with cross-flaws compared with that with non-cross-flaws. Meanwhile, the connection type of main flaws and the width of the crack coalescence zone are difficult to observe through the experiments and are discovered from the numerical simulation.

Dongxu Liang

Nong Zhang

Haoyu Rong

Zhe Xiang

Experimental and Numerical Studies on Crack Initiation and Coalescence in Sandy Mudstone with Prefabricated Cross-Flaws Under Uniaxial Compression

The deformation and instability of roadway surrounding rock reflect the processes of energy accumulation and release. To reveal the instability of roadway surrounding rock, based on the engineering geological conditions of a certain mine, this paper established a nonuniform superimposed stress model of a coal pillar, starting from the energy accumulation and release of the surrounding rock of the floor roadway after coal pillar failure. The essence of the deformation of the lower roadway was revealed, and the following conclusions were drawn: (1) The elastic strain energy accumulated in the lower roadway roof and upper coal pillar is related to not only the physical properties of the coal seam but also the distance between the coal pillar and surrounding rock, the caving height and shape, the burial depth, and the retained pillar width. (2) The elastic strain energy accumulated in the lower roadway roof and the upper coal pillar induced large displacements of the roadway due to the energy release during excavation. (3) It is proposed that the &#x201c;stress relief degree&#x201d; and failure morphology are used to identify zones in the rock and coal, and the two zoning modes have a high consistency. (4) The stress distribution in a narrow coal pillar should be calculated in segments. (5) Based on the zoning and energy release characteristics, the following control factors are suggested regarding the coal pillar width and roadway layout: (a) for the coal pillar, avoid the overlap or intersection of the peak values in the limit equilibrium zone and ensure a sufficient elastic zone; (b) arrange the roadway in shear slip Zone B-2 or the moderate pressure relief Zone B-2 to reduce the accumulation of elastic strain energy in the surrounding rock.

Huai-Qian Liu

Lei Wang

Lian-Chang Han

Ping Liu

Peng Zou

Study on the Instability Mechanism and Control Measures of a Roadway in a Mine with Retained Coal Pillars and Close Coal Seams

Based on the particle flow code (PFC<sup>2D</sup>) within the discrete element method (DEM), the rock mass model was established according to the site rock conditions and the rock mass blasting was simulated by the explosive particle expansion method. The influence of various parameters (the peak pressure action coefficient of the borehole wall, explosive particle buried depth, and charge mode) in the explosive particle expansion method on blasting effect was investigated. Furthermore, the relationship between the various parameters and the geometry size of the blasting crater was obtained. By comparing the size of blasting crater in the field blasting test and numerical simulation example, the reliability of rock mass blasting simulated by the explosive particle expansion method using PFC is verified. The result shows that this paper provides a reliable new numerical simulation method for rock mass blasting and can be used to guide field blasting.

Wenle Gao

Zehua Zhang

Baojie Li

Kunpeng Li

Study on Numerical Simulation of Geometric Elements of Blasting Funnel Based on PFC5.0

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<p><em>Shock and Vibration</em> publishes papers on all aspects of shock and vibration, especially in relation to civil, mechanical and aerospace engineering applications, as well as transport, materials and geoscience.&nbsp;</p>


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<p>Chief Editor&nbsp;Dr Tai Thai&nbsp;is based at the University of Melbourne and his current research focuses on high strength materials for sustainable construction of buildings, bridges and other infrastructure.</p>


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Shock and Vibration publishes papers on all aspects of shock and vibration, especially in relation to civil, mechanical and aerospace engineering applications, as well as transport, materials and geoscience. 

Shock and Vibration