Stress Wave Attenuation Research Articles

Development of Dust Emission Prediction Model for Open-Pit Mines Based on SHPB Experiment and Image Recognition Method

Open-pit coal mining offers high resource recovery, excellent safety conditions, and large-scale production. However, the process generates significant dust, leading to occupational diseases such as pneumoconiosis among miners and adversely affecting nearby vegetation through dust deposition, which hinders photosynthesis and causes ecological damage. This limits the transition of open-pit mining to a green, low-carbon model. Among these processes, blasting generates the most dust and has the widest impact range, but the specific amount of dust generated has not yet been thoroughly studied. This study integrates indoor experiments, theoretical analyses, and field tests, employing the Split Hopkinson Pressure Bar (SHPB) system to conduct impact loading tests on coal–rock samples under pressures ranging from 0.13 MPa to 2.0 MPa. The results indicate that as the impact load increases, the proportion of large-sized blocks decreases while smaller fragments and powdered samples increase, signifying intensified sample fragmentation. Using stress wave attenuation theory, this study translates indoor impact loadings to field blast shock waves, revealing the relationship between blasting dust mass fraction and impact pressure. Field tests at the Haerwusu open-pit coal mine validated the formula. Using image recognition technology to analyze post-blast muck-pile fragmentation, the estimated dust production closely matched the calculated values, with an error margin of less than 10%. This formula provides valuable insights for estimating dust production and improving dust control measures during open-pit mine blasting operations.

Experimental investigation on the anti-detonation performance of composite structure containing foam geopolymer backfill material

The compression and energy absorption properties of foam geopolymers increase stress wave attenuation under explosion impacts, reducing the vibration effect on the structure. Explosion tests were conducted using several composite structure models, including a concrete lining structure (CLS) without foam geopolymer and six foam geopolymer composite structures (FGCS) with different backfill parameters, to study the dynamic response and wave dissipation mechanisms of FGCS under explosive loading. Pressure, strain, and vibration responses at different locations were synchronously tested. The damage modes and dynamic responses of different models were compared, and how wave elimination and energy absorption efficiencies were affected by foam geopolymer backfill parameters was analyzed. The results showed that the foam geopolymer absorbed and dissipated the impact energy through continuous compressive deformation under high strain rates and dynamic loading, reducing the strain in the liner structure by 52% and increasing the pressure attenuation rate by 28%. Additionally, the foam geopolymer backfill reduced structural vibration and liner deformation, with the FGCS structure showing 35% less displacement and 70% less acceleration compared to the CLS. The FGCS model with thicker, less dense foam geopolymer backfill, having more pores and higher porosity, demonstrated better compression and energy absorption under dynamic impact, increasing stress wave attenuation efficiency. By analyzing the stress wave propagation and the compression characteristics of the porous medium, it was concluded that the stress transfer ratio of FGCS-ρ-579 was 77% lower than that of CLS, and the transmitted wave energy was 90% lower. The results of this study provide a scientific basis for optimizing underground composite structure interlayer parameters.

Experimental Study on the Boundary Reflection Effect of Stress Wave Propagation Based on the Newly Developed Test Apparatus

There is a ubiquitous boundary reflection effect of stress wave propagation in the indoor experimental studies. It is critical to improve the validity of waveform data by optimizing boundary materials to absorb reflection waves. In the present study, a calculation method for the optimal wave impedance of boundary materials was proposed based on the transmission and reflection principle of one-dimensional stress waves at the interface of different media. By using the calculation method, the optimal wave impedance value of the boundary material was obtained. A one-dimensional stress wave propagation test apparatus was developed for exploring the improvement effect of absorbing materials on the boundary reflection effect. One-dimensional stress wave propagation experimental studies in the complete red sandstone samples were carried out by setting various boundary absorbing materials such as pine pad, rubber pad, and steel pad. The results indicated that the experimental test results were consistent with the theoretical calculation results. In the stress wave propagation tests, the optimal wave impedance value of the boundary material was 1.12 × 106 kg/m2·s. When the pine pads were used as boundary absorbing materials, the suppression effect of boundary reflection effects is relatively the best. The present study provides references for analyzing the characteristics and mechanism of stress wave propagation and attenuation.

Study on the failure effect of aramid reinforced concrete slab under localized blast loading

As a new material with low density, high modulus and high strength, aramid fibers and composite laminates are widely used in protective structures. Aramid reinforced concrete panels as a new type of protective combination of structures, especially in the concrete-aramid laminate composite blast-resistant structure, the optimal thickness combination of reinforced concrete and aramid laminate has not been targeted research. In this paper, three types of scaled down reinforced concrete (RC) slabs, aramid fiber reinforced concrete (AFRC) slabs and aramid fiber reinforced plastic reinforced concrete (AFRPRC) slabs were designed and fabricated to carry out experimental studies under local explosive loading and to compare the blast resistance of different slabs through damage analysis. Based on LS-DYNA software, the damage characteristics of AFRPRC plates were investigated and compared and analysed with the test results to verify the accuracy and applicability of the FEA model. Typical damage patterns of structures under different TNT charges were obtained, and empirical equations between the damage characteristics of reinforced concrete slabs (maximum mid-span displacement, crater diameter, crater depth) and TNT charges were fitted by means of magnitude analysis. The effect of the aramid layer on the structural blast resistance performance was analysed from three perspectives: maximum central displacement, stress wave attenuation rate and internal energy absorption. The results show that AFRC improves the blast resistance of reinforced concrete not significantly relative to ordinary reinforced concrete slabs, while AFRPRC slabs maintain good integrity and show better blast resistance. The best blast resistance performance of AFRPRC panels is achieved when the ratio of reinforced concrete thickness to aramid layer thickness is 50:3. The results of the study can provide theoretical basis and reference for efficient protection of composite structures.

Experimental and Numerical Simulation Study on the Mechanism of Fracture-Increasing and Permeability-Increasing in Granite Pore Walls by the Air DTH Hammer Percussion Drilling

Air DTH (Down-The-Hole) hammer percussion drilling (vibration percussion drilling) has proven to be a highly efficient geothermal drilling technique, and percussion fractures near the wellbore benefit geothermal energy development in many ways (such as hydraulic fracturing, perforation, etc.). However, no research has been done on the mechanism of fracture-increasing and permeation-increasing in granite pore walls by air DTH hammer percussion drilling. This article: (1) using an air drilling test device, an air DTH hammer whole bit impact rock fragmentation test was conducted on granite in an atmospheric environment; (2) dyeing experiments, CT scanning, and 3D reconstruction modeling were used to characterize and identify wellbore cracks; (3) research the strength, porosity, and permeability changes of granite wellbore through mechanical and permeability testing experiments; and (4) numerical simulation of impact stress waves using particle flow code (PFC) 6.0 software to demonstrate the rationality of impact experimental results. The results show that the air DTH hammer impact can induce micro-cracks in the wellbore, and the distribution of cracks is regionalized, mainly due to the attenuation of the impact stress wave. The numerical results are consistent with the experimental results. The average strength of granite decreased by 16.5%, the average porosity increased by 9.5%, the average permeability increased by 63.3%, the porosity increased from 0.0025% to 0.03%, and the porosity increased by about 12 times under the air DTH Hammer percussion drilling. The above results provide the theoretical basis and experimental proof for the ability of air DTH hammer drilling to produce wellbore cracks and improve wellbore permeability. The presented experimental results can be a useful reference for building numerical models.

Stress wave attenuation in ultra-high performance fibre-reinforced concrete during ballistic impact

Depending on material properties and boundary conditions, various waves propagate within the target, during an impact event. Stress wave attenuation during ballistic impact can be expressed in strain profiles regarding time and distance from the impact point. The design of a ballistic-resistant structure thus depends on the stress wave attenuation. This present study focused on stress wave attenuation under projectile impact in ultra-high performance fibre-reinforced concrete (UHPFRC). 3 mm strain gauges were found suitable for such measurements. Two different types (steel fibres) of UHPFRC (Single fibre (S2): 2 % of 6 mm steel fibre and Hybrid fibre combination (S0.5L1.5): 0.5 % of 6 mm + 1.5 % of 13 mm steel fibres) were used for investigation. During the ballistic impact event, strain profiles at specific distances from the point of impact on both the front and rear surfaces of UHPFRC targets were recorded. The scabbing damage due to tension was captured and analysed in this study through stress wave attenuation. The impact performance of hybrid (Short and Long fibres) S0.5L1.5 UHPFRC combinations was much better than S2 (only short fibres) UHPFRC targets. The hybrid steel fibre UHPFRC also shows higher strain attenuation (than short fibre based UHPFRC) in the range of 10-30 µε/mm. It was concluded that the efficiently designed ballistic-resistant UHPFRC should have higher wave attenuation, implying the concrete has enhanced capacity to absorb and localise energy, thereby mitigating the extent of damage inflicted upon the overall concrete slab.

Stress wave attenuation in chocolate

The stress wave attenuation in five types of chocolate (extra dark, dark, milk, white, and ruby) was studied. The main acoustics properties of these chocolates were described in terms of longitudinal and transversal wave velocities. The attenuation of the stress waves was studied using the experimental technique known as the Split Hopkinson Pressure Bar (SHPB). The SHPB set-up consists of a specimen and linear elastic incident and transmission bar. Experimental data have been evaluated both in the time as well as frequency domain. Attenuation of the stress wave was described namely using the frequency dependence of the transmission coefficient of the stress wave. This damping increases with the plastic strain of the tested chocolate specimens. From a technological point of view, the fat content of the chocolate has the highest influence on the reduction of the longitudinal wave propagation velocity. The lowest attenuation was observed for the dark chocolate.

Penetration mechanics of ceramic/metal functionally graded plates under ballistic impact: An experimental perspective

This paper deals with a comprehensive experimental analysis of the penetration mechanics and failure mechanisms of SiC/AA6061 functionally graded plates under ballistic impact. The external, cross-sectional, and high-speed photographic damage and failure assessments of the plates were performed. The novelty of this study is to investigate the ballistic impact behavior of a ceramic/metal functionally graded plate with different compositional gradients in a wide range of impact velocities considering below and above the ballistic limit and to reveal a detailed analysis of the damage and failure mechanisms of the plate. This can provide fundamental insights into the design of ceramic/metal functionally graded armor materials. The results indicate that the metal-dense gradient plate shows localized ductile failures as ductile perforation and plugging, whereas the ceramic-dense gradient plate exhibits brittle failures as comminution and conoidal fracture. Tailoring a relatively continuous compositional gradient instead of an abrupt variation, namely the linear gradient, provides tensile stress wave attenuation and resistance to crack growth and fracture.

Experimental and numerical investigation of badarpur sand subjected to air-blast loading

In the present study, the results of experimental and numerical investigation of Badarpur sand subjected to air-blast loading generated from a laboratory-scale blast simulator are presented. The air-blast loading on the sand specimen is simulated experimentally using a vertical shock tube test facility to investigate the stress wave attenuation and vibrational characteristics of the Badarpur sand. The peak stress wave pressure and peak particle acceleration are recorded using the synchronized pressure transducers and triaxial accelerometers embedded inside the sand specimen. A stress enhancement of about 1.25-2.69 times the peak over-pressure is observed at the top one-third layer of the sand due to its compaction by the stress wave generated upon the blast wave impact. The stress wave intensity first increases and then rapidly decreases with the depth of the sand specimen. The amplitude of the peak particle acceleration is also observed to attenuate with the depth of the sand specimen. Further, based on the experimental results, the empirical equations are developed to predict peak particle velocity against the scaled distance with a power law index of 3.9, 2.5, and 3.0 for dense-coarse, dense-fine, and medium-dense fine sand, respectively. The numerical model of the vertical shock tube and sand specimens are also developed based on the Arbitrary Lagrangian-Eulerian formulation, commercially available in finite element simulation package LS DYNA and the results are validated with the experimental data.

Enhanced the impact resistance by gradient face-sheet design of a sandwich structure

Sandwich structure has been designed to reduce the impact damage of the stress waves. However, the existing work focuses on the optimization of sandwich cores while the face-sheet structure is seldom improved. Here, we used the impedance matching theory to design a negative gradient face-sheet sandwich structure with excellent stress wave attenuation performance. Owing to stress wave attenuation form a high impedance to a low one, the negative gradient face-sheet sandwich structure shows a low peak stress of 5.51 MPa, and the average transmission peak stress is 2.69 MPa. The gradient face-sheet structure changes the compressive deformation behavior; thus, the energy absorption performance of the negative gradient face-sheet sandwich structure increases to be 1311.8 kJ/m3 and the specific energy absorption reaches 1072 J/kg. Finite-element methods further demonstrate the overall sandwich structures can be enhanced through alleviating the failure of sandwich core by a gradient face-sheet structure. This work provides a paradigm for the design of sandwich structures with high energy absorption performance.

Dynamic mechanical mechanism and optimization approach of roadway surrounding coal water infusion for dynamic disaster prevention

Roadway surrounding coal water infusion is a most significant technical means for the dynamic disasters prevention. To evaluate its efficiency in dynamic mechanical environment, the damage distribution and mechanical parameters were analyzed before and after water infusion. And the relationship among damage distribution, dynamic mechanical parameters, and stress wave propagation were established. With the medium of the wave impedance, the stress wave transmission process was characterized, and the dynamic stability criterion was established from the perspectives of energy and stress, respectively. On this basis, the optimization approaches were further proposed and validated in practice. The results demonstrate that water infusion can effectively enlarge the wave impedance difference among each adjacent circumferential coal segment and damage range in the surrounding coal. It will enhances the stress wave attenuation, thereby protecting the roadway from dynamic failure. To better play its role, the optimization approaches should focus on increasing the damage degree and range of the microscopic fracture zone in surrounding coal. These findings provide valuable insights into the design and implementation of surrounding coal water infusion for dynamic disasters prevention.

Empirical formulas for predicting the energy attenuation behavior of primary stress waves in 1D composite chain of viscoelastic spheres

One-dimensional composite chain of viscoelastic spheres are potential candidates for novel impact buffers. Understanding the energy attenuation behavior of primary stress waves in the composite chain of viscoelastic spheres is the premise for high-performance impact buffers design. Although the current research included viscoelasticity into the motion equations of spheres, most of them were limited to homogeneous chains. Moreover, the models of discrete system could not give the explicit expressions of the key factors governing the energy attenuation of primary stress waves. The absence of explicit formulas for the key factors hindered efficient optimization design of impact buffers constructed by one-dimensional composite chain of viscoelastic spheres. In this study, empirical formulas for predicting the input amplitude, the attenuation coefficient of the contact force and the transmission coefficient at the interface were constructed. Multivariate nonlinear regression method and dimensional constraint were applied to ensure that all the empirical formulas only employ the impact velocity and the parameters of the used spheres as independent variables. Intermediate factor was introduced for individual key factor to evaluate the accuracy of the empirical formula. Though the groups of empirical formulas have degraded performance in the low range of the intermediate factors, their accuracy in quantitatively predicting the energy attenuation behavior of the stress waves in one-dimensional composite chain of viscoelastic spheres deserves satisfactory.

Study of stress wave attenuation characteristics of particle ceramic embedded polyurethane composites

In this paper, particle ceramic embedded polyurethane composites were prepared, and the dynamic and static mechanical properties of polyurethane elastomers were tested. Experiment and simulations were used to investigate the effects of different design parameters of polyurethane elastomers and particle ceramic on the stress wave attenuation of the composites. The microscopic morphology, energy absorption, and attenuation capabilities of the composites were analyzed and discussed. The results show that the polyurethane elastomers adheres well to the particle ceramic after impact and exhibits sufficient bonding with stable interfacial strength; As the volume fraction of particle ceramic increases, the energy absorption ratio also increases; The “harder” the polyurethane elastomer, the weaker the composite attenuation ability of stress waves. The function relationship between the composite attenuation ability of stress waves and the particle ceramic area occupy ratio and the number of stacked layers is obtained by fitting, which shows that the composite attenuation ability of stress waves is inversely proportional to the area occupy ratio and positively proportional to the number of stacked layers of particle ceramic.

Burden Effects on Rock Fragmentation and Damage, and Stress Wave Attenuation in Cut Blasting of Large-Diameter Long-Hole Stopes

Burden Effects on Rock Fragmentation and Damage, and Stress Wave Attenuation in Cut Blasting of Large-Diameter Long-Hole Stopes

Propagation and attenuation of stress waves in heterogeneous elastic rods

In this paper, the propagation and attenuation of stress waves induced by an integrable external load in an elastic rod with multiple inclusions are investigated. The traveling wave method is suggested for obtaining the reflection coefficient, transmission coefficient, and attenuation coefficient of the wave propagating from one media to another. Furthermore, the effects of wavelength and the size of inclusion on elastic wave propagation are calculated by the finite element method. The results show that the theoretical solution is fitted well with the finite element numerical results. The attenuation coefficient is influenced by material parameters, wavelength, and the number of inclusions. The smaller wavelength or more inclusions will incur the more obvious attenuation phenomenon. Moreover, the reflection coefficient and transmission coefficient are affected by the acoustic impedance ratio of the matrix and the inclusion. The results of this paper can be served as the theoretical basis for the study of wave propagation in heterogeneous materials.

Experimental and mesoscale analysis on wave propagation induced by impact in dry silica sand

When investigating the propagation of stress waves in sand-like materials, the materials are generally modeled as homogeneous parts despite their complex structures comprising numerous particles of varying sizes and shapes. However, this approach fails to consider the non-continuum nature of sand-like materials. To address this issue, a mesoscale numerical model of silica sand particles with random shapes and three sizes is employed in this study to numerically analyze wave propagation. Experimental data from an upgraded split Hopkinson pressure bar test are utilized to validate the accuracy of the numerical model. Using the validated numerical model, we investigate the impact of relative densities, incident wavelengths, and wave amplitudes on stress wave attenuation in dry silica sand. Empirical equations are derived from summarizing the stress wave attenuation law induced by impact loading. The study shows that relative density and wavelength are critical factors affecting the residual peak stress ratio in silica sand, while the effect of loading wave amplitude is limited.

Fast stress wave attenuation in bioinspired composites with distributed soft particles modulating hard matrices

Fast stress wave attenuation in composites is highly desired in many industry fields. Biological composites such as those in the beak of woodpeckers provide great inspiration for us to develop their synthetic counterparts with similar mechanical functions. Accordingly, bioinspired designs of composites with distributed soft particles are put forward in the paper, and their performance in attenuating stress wave is investigated through FEM simulations. Subjected to projectile impacts, the bioinspired composites not only absorb more impact energy but also delay and attenuate the impact-induced stress wave very efficiently. The simultaneous improvement of the two aspects of impact-resistant performance in a single material design should be highly desired in many industry fields. Further, the influences of the inclusion volume fraction, impedance, shape and distribution pattern are systematically investigated and general principles of design are drawn. The findings and conclusions can not only provide useful guidelines for the design of bioinspired composites with high protection function from impact loading but also help understand the working mechanisms of natural biological composites to resist impact loadings.

Freeze–thaw process of soil between two piles as monitored by piezoelectric ceramic sensor

As the mechanical properties of soil are affected by the moisture content, diameter of soil particles, and the soil temperature, we used piezoelectric ceramic sensors to monitor the freeze–thaw cycle of different soils at different temperatures and different moisture content. By studying the energy attenuation of stress waves propagating in freezing–thawing soil, its mechanical strength was determined. The results showed that the duration of freeze–thaw process was related to soil type and initial water content. For the same water content and larger soil particle size, the received signal amplitude and energy are larger. For the same soil type and higher water content, the received signal amplitude and energy are stronger. This study provides a feasible monitoring method for infrastructure construction in areas with complex geological conditions, such as Qinghai-Tibet frozen soil.

Propagation of stress waves in layered rock mass under the impact of high-pressure gas

High-pressure gas (HPG) blasting is safe and environmentally friendly, and has replaced traditional explosive blasting in some applications. The characteristics of HPG impact load and the propagation law of the stress wave in layered rock mass (LRM) under HPG blasting were investigated experimentally and numerically. Through experimental tests of hole wall pressure, a segmented exponential model of the hole wall pressure under the impact of HPG was developed; it accurately accounted for the time history characteristics of the hole wall load. Experimental tests of stress wave propagation were conducted; the soft rock–hard rock interface was found to have a significant effect on stress wave propagation in the LRM. Based on the experimental results, a specific strain model for 10 MPa HPG impact was fitted for a single-hole LRM. A polynomial exponential model and a specific strain model (20 MPa HPG impact) were found for the double-hole LRM. The stress wave attenuation laws for single-hole and double-hole LRM were characterised well. The propagation characteristics of stress waves in LRM under the impact of HPG were analysed and a numerical model of stress wave propagation was established. The numerical model adopted the Riedel–Hiermater–Thoma (RHT) material model for the test parameters. The proposed segmented exponential models of hole wall pressure were applied to the lower, middle and upper parts of the blasthole. With the feasibility of the numerical model analysed, the stress wave propagation characteristics were studied by numerical simulation of an underground pipe gallery. This study provides theoretical guidance and practical value for improving rock-breaking theory and optimising HPG blasting in LRM.

Model Test Study on the Transmission Law of Explosion Stress Wave in Rock Mass with Filling Joints

In order to study the propagation and attenuation law of explosive stress wave in rock mass with filling joints, and consider the influence of different crustal stress conditions, different strength mortar is used to simulate rock mass and joints, and the multi-functional simulation test device of geotechnical engineering is used to carry out explosive model test research, the influence characteristics of different in-situ stress conditions on the attenuation of explosive stress wave in rock mass with different thickness filling joints are analyzed, and obtain the transmission law of stress wave. The results show that: when the explosion stress wave propagates in the joined rock mass, the thicker the filling joint is, the greater the attenuation range of the stress wave energy and the samller the transmission coefficient; In-situ stress will change the attenuation of explosive stress wave in rock mass. With the increase of in-situ stress, the transmission coefficient of stress wave in intact rock mass and joined rock mass will increase. When the local stress is fixed, the transmission coefficient of stress wave in joined rock mass also increase gradually with the increase of explosion load.