Propagation Law Of Stress Wave Research Articles

Damage evolution law of multi-hole blasting igneous rock and quantitative evaluation model of damage degree based on fractal theory and clustering algorithm

The geological phenomenon of igneous rock invading coal seam is widely distributed, which induces mining risk and affects efficient mining. The pre-splitting blasting method of igneous rock is feasible but difficult to implement accurately, resulting in unnecessary safety and environmental pollution risks. In this paper, the blasting model with penetrating structural plane and the multi-hole blasting model with different hole spacing were established based on the Riedel–Hiermaier–Thoma (RHT) damage constitutive to explore the stress wave propagation law under detonation. The damage cloud diagram and damage degree algorithm were used to quantitatively describe the spatio-temporal evolution of blasting damage. The results show that the explosion stress wave presents a significant reflection stretching effect under the action of the structural plane, which can effectively aggravate the presplitting blasting degree of the rock mass inside the structural plane. The damage range of rock mass is synchronously evolved with the change of blasting hole spacing. The blasting in the igneous rock intrusion area of the 21,914 working face is taken as an application example, and the damage degree of rock mass is reasonably evaluated by the box-counting dimension and K-means clustering method, which proves the effectiveness of the blasting scheme and provides reference value for the implementation of related blasting projects.

Rock-like material under large diameter SHPB dynamic splitting tension: meso-damage mechanical behavior and stress wave propagation model

The mechanical behavior of splitting tensile damage and the law of stress wave propagation of rock-like materials (RLM) are of great significance to further reveal the dynamic disaster mechanism of the deep rock mass. The meso-damage mechanical behavior and stress wave propagation characteristics of RLM disks under impact splitting were studied by using a large diameter split Hopkinson pressure bar (SHPB). In terms of dynamic damage, the splitting tensile stress-compression strain curves of RLM disks obviously showed three stages of mechanical behavior evolution: initial elastic-plastic deformation, pre-peak plastic damage, and post-peak brittle fracture failure. The macro-damage of RLM disks increased with the increase of strain rate. The meso-tensile fracture was the result of both the initial meso-damage and the impact splitting meso-damage. The dynamic splitting damage variable defined based on the damage fracture energy can accurately describe the damage evolution characteristics of impact splitting on RLM disks. In the aspect of stress wave propagation, the peak value of transmission stress showed an advanced effect with the increase of incident stress wave. In the early stage (0–50 μs), the transmission stress wave ratio (σT/σI) increased with the increase of strain rate, while in the later stage (82–200 μs), the transmission stress wave ratio (σT/σI) decreased with the increase of strain rate. The stress wave propagation law in the process of impact splitting on RLM disks was clearly revealed based on the stress wave propagation model established by the one-dimensional elastic stress wave theory. Finally, the dynamic mechanical mechanism of splitting damage and fracture of RLM disks under different strain rates was discussed deeply.

Stress wave propagation law in CFRP under laser impact conditions

The paper analyzes the propagation law of stress waves in CFRP unidirectional plate specimens and adhesive plate specimens under laser shock conditions using a combination of experimentation and simulation. The finite element model is corrected by using the back particle velocity curve obtained from the experiment. Subsequently, the spatiotemporal stress distribution is extracted from the finite element model. The results indicate an overall attenuation trend of the stress wave propagating in the unidirectional plate. In the adhesive plate, the peak value of the stress wave increases first at the adhesive layer position due to the acoustic impedance mismatch and energy absorption characteristics of the adhesive layer material and CFRP. Then it tends to increase after decay. Moreover, the behavior characteristics of the stress wave differ significantly when it propagates from high-impedance material to low-impedance material compared to when it propagates from low-impedance material to high-impedance material.

Experimental Investigation on the Influence of Wave Impedance on Dynamic Mechanical Response of Granites undergone High Temperature.

Wave impedance is an important physical quantity to characterize the dynamic properties of materials. To explore the influence of wave impedance on the dynamic mechanical response of rock, the granite samples with a wave impedance gradient change are obtained by changing the heating temperature, and the impact compression test is carried out by using a split Hopkinson pressure bar (SHPB) device. The stress wave propagation law, dynamic stress-strain relationship, and fracture characteristics of rocks with different wave impedances are studied comparatively, and the influence mechanism of wave impedance on the dynamic mechanical response of rocks is comprehensively analyzed from two aspects of material properties and dynamics. The results show the following: (1) Under the action of the same incident wave, the reflected wave amplitude, transmission wave takeoff time, peak stress, peak strain, and equivalent average size of fragments of granite samples with different wave impedances are significantly different. (2) As the heating temperature increases, the wave impedance of granite continuously decreases and the degree of damage intensifies. Within the high-temperature treatment range of 400 to 600 °C, there is a damage wave impedance threshold between 7854 and 3081 g·cm-3·m·s-1. Below this wave impedance, granite will appear to have significant damage deterioration. (3) Under the same incident wave, the strain rate and loading rate of granite samples show negative correlation and positive correlation with wave impedance, respectively. There is a progressive relationship between rock wave impedance, stress wave propagation, strain rate history/stress history, and dynamic mechanical response.

Effect of dynamic loading orientation on fracture properties of surrounding rocks in twin tunnels

For expedited transportation, vehicular tunnels are often designed as two adjacent tunnels, which frequently experience dynamic stress waves from various orientations during blasting excavation. To analyze the impact of dynamic loading orientation on the stability of the twin-tunnel, a split Hopkinson pressure bar (SHPB) apparatus was used to conduct a dynamic test on the twin-tunnel specimens. The two tunnels were rotated around the specimen’s center to consider the effect of dynamic loading orientation. LS-DYNA software was used for numerical simulation to reveal the failure properties and stress wave propagation law of the twin-tunnel specimens. The findings indicate that, for a twin-tunnel exposed to a dynamic load from different orientations, the crack initiation position appears most often at the tunnel corner, tunnel spandrel, and tunnel floor. As the impact direction is created by a certain angle (30°, 45°, 60°, 120°, 135°, and 150°), the fractures are produced in the middle of the line between the left tunnel corner and the right tunnel spandrel. As the impact loading angle (α) is 90°, the tunnel sustains minimal damage, and only tensile fractures form in the surrounding rocks. The orientation of the impact load could change the stress distribution in the twin-tunnel, and major fractures are more likely to form in areas where the tensile stress is concentrated.

Fractal study on the damage induced by shaped charge blasting with uncoupled eccentric charge

In this study, a dynamic caustic experimental system is used to examine the damage distribution characteristics as well as the crack formation/propagation mechanism in polymethyl methacrylate (PMMA) caused by uncoupled eccentric shaped charge blasting under different decoupling coefficients and charge positions. Using PMMA as the experimental material, the damage variables around the hole are calculated by the digital image processing method. The stress wave propagation law under different charge positions is revealed. Furthermore, based on the fractal theory, the damage values of shaped and unshaped cracks are calculated. The results show that the range of the crushed zone and failure zone on the coupled side around the hole of eccentric uncoupled charge is larger than that on the uncoupled side, which can reduce the damage on the reserved side and break the excavation side more fully. Under the condition of eccentric uncoupled charging, the range of the crack zone and failure zone decreases with the increase in the decoupling coefficient. When the decoupling coefficient is 2, the smoothness of the main crack is the best, and the total and average lengths of the main crack are also maximum. The damage distribution caused by explosive crack conforms to the fractal law, and the fractal dimension can accurately represent the damage degree of PMMA after the explosion.

Experimental study on dynamic compression behavior characteristics and stress wave propagation law of rigid-flexible combinations under cyclic bi-directional impact loading

To explore the dynamic compression behavior and damage evolution characteristics of “rigid-flexible coupling” surrounding rock supporting structure. Split Hopkinson pressure bar (SHPB) was used to carry out constant amplitude cyclic bi-directional impact compression tests on the combination specimens of “rigid-rigid: rock (sandstone)-like material (RLM) - normal cement mortar (NCM)", “rigid-flexible: RLM - rubber cement mortar (RCM)" and “flexible-rigid: RCM - high-performance supporting concrete (HPSC)". The characteristics of stress-strain curve evolution, stress attenuation, strain growth, energy transformation, damage evolution characteristics, and damage state were compared and analyzed. The results show that compared with RLM-NCM, RLM-RCM and RCM-HPSC had remarkable dynamic yield ductility and excellent impact resistance. RCM and HPSC can work together to hinder the dynamic damage development of “rigid-flexible coupling” supporting structure and surrounding rock. Based on the one-dimensional stress wave propagation theory, the stress wave propagation models of rigid-flexible combination specimens under SHPB cyclic bi-directional impact were established, and the corresponding stress wave propagation equations were derived, which profoundly revealed the propagation law and attenuation mechanism of stress waves in SHPB impact rigid-flexible combination tests. Finally, based on the energy drive theory and residual energy theory, the impact instability energy criteria of surrounding rock under the rigid component combined support system and “rigid-flexible coupling” component combined support system were analyzed and discussed.

Study on ballistic mechanism of B4C/Al gradient armor

AbstractIn order to improve the anti‐penetration performance of gradient armor, the constitutive models of B4C/Al composites with different compositions were determined according to the bending curves. The anti‐bullet simulation of B4C/Al gradient armor was carried out by ANSYS‐DYNA finite element software, and the stress state of B4C/Al gradient material under 7.62‐mm bullet penetration was analyzed. Meanwhile, the propagation law of stress wave in armor was studied by Hopkinson bar simulation and the improved internal stress wave model, which further revealed the ballistic mechanism of B4C/Al gradient armor. The simulation results showed that, compared with the traditional laminated armor, the toughness of B4C/Al gradient armor material increased with the change of layer thickness, resulting in the fact that the whole armor could withstand greater stress without breaking, and the anti‐penetration time was prolonged. In addition, the performance difference between the layers of the gradient armor was slight, and the spallation phenomenon of the relative double‐layer armor decreases, which enhanced the multiple hit performance of the armor and the absorption capacity of the stress wave. The performance of B4C/Al gradient armor specimens and double‐layer specimens were tested by drop hammer impact test. The test results were consistent with the simulation results.

Research on Laplace transform of stress wave propagation relaxation function in multi-layer media

There are some difficulties in solving the theory of stress wave propagation in multi-layer media. To solve the problem of stress wave propagation in multi-layer media under the impact load, this paper theoretically makes further derivation and discussion based on viscoelastic analogy method. To further verify the feasibility of the theoretical solution, LS-DYNA is used to simulate the three-layer medium. The simulation results show that comparing the peak stress obtained from the numerical inversion of the Laplace function after the Laplace transform with the simulation results, the maximum error of the peak stress is about 9.5%, and the minimum error is about 1.7%. The results show that the theoretical solution agree with the simulation results, and the theoretical solution has specific feasibility. The theoretical solution method deduced in this paper further develops the viscoelastic analogy method, which has a specific reference value for the rapid calculation of the stress wave propagation law in multi-layer media.

Investigation on the influence mechanism of polyurea material property on the blast resistance of polyurea-steel composite plate

The application of polyurea in the field of anti-blast has attracted extensive attention. To study the influence and mechanism of polyurea with different mechanical properties on the blast resistance of steel plate structure, two types of polyurea with different mechanical properties (high hardness and ductility) were selected and coated on a carbon steel plate. The mechanical properties of two types of polyurea under quasi-static and dynamic conditions were quantitatively compared. A series of field tests of composite plates subjected to blast load were conducted. The macro damage characteristics of targets with different configurations were obtained. Combined with metallographic microscopy and scanning electron microscopy, the micro failure characteristics of the steel plate and polyurea were confirmed. The energy absorption mechanism of different types of polyurea was revealed by Fourier transform infrared. The results show that high hardness polyurea can only slightly improve the blast resistance of the steel plate when it was coated on the front. Coating polyurea on the back face of the steel plate had the best effect on improving the blast resistance, but it would produce backward flying fragments, which may lead to secondary injury. The high ductility polyurea can effectively improve the blast resistance of the steel plate without fragments, no matter coated on the front or back. The response process of polyurea with high hardness was transient. While the response process of polyurea with high ductility was relatively continuous. From the perspective of chemical bonds, the energy absorption mechanisms of different types of polyurea were also different. Finally, the mechanisms of various effects of polyurea with different mechanical property on the blast resistance of steel plate were discussed using the propagation law of stress wave. This study can provide a reference for the application of polyurea spraying technology under the anti-blast protection of metal structure.

Optimization of Pre-Splitting Blasting Hole Network Parameters and Engineering Applications in Open Pit Mine

In order to optimize the parameters of a pre-splitting blasting hole network, taking an open-pit mine in Inner Mongolia as the engineering background, the numerical models of different pore sizes and hole spacing were established by LS-DYNA software. The stress wave propagation law, peak stress change and rock fracture state under various working conditions were analyzed. The optimization formula of a hole network relationship was proposed and verified on site. The results show that the shock wave generated by the explosion propagates rapidly upward from the explosion source and forms a plastic flow zone around the two boreholes. The energy consumption is the largest at this stage. With the propagation of the stress wave, energy dissipates, and its waveform gradually attenuates to a compression wave and seismic wave. In each working condition, a 110 mm aperture first cracked in the stress wave superposition area compared with other working conditions, while a 120 mm aperture delayed evolution to the seismic wave compared with different borehole aperture, and the energy attenuation rate is the slowest. Meanwhile, the fastest energy attenuation rate is with the 130 mm borehole aperture. With the attenuation of the propagation energy of the stress wave, among the four measuring points set at the center of the connection between the two boreholes, the Y-direction stress of the observation points B, C and D is stable between 2.3 and 3.5 MPa, and the Y-direction stress of the observation point A is strenuous between −1.3 and 1.2 MPa. The B, C and D observation points of 90–130 mm aperture conditions showed rock cracking at 7–9 times, 7–9 times, 7–10 times, 7–11 times, and 7–11 times hole spacing, respectively. The cracks of the two boreholes were interconnected. The optimal hole network relationship is obtained by fitting: y = 1.12 + 0.076x, where y is the optimal hole diameter and hole spacing multiple, and x is the hole diameter, which is verified by engineering. After blasting, the slope is smooth and smooth, and the half-hole rate is guaranteed to be above 90%.

Research on the Propagation Law of Stress Wave in Rock Mass Supported by Bolt under Dynamic Load

At present, the development of bolt support technology is in the ascendant period, which is of great significance to promote the development of geotechnical engineering. The numerical simulation software RFPA (Rock Failure Process Analysis) has been used to analyze the reinforcement effect of bolt on deep surrounding rock under dynamic load and conduct a comprehensive research on the force state of bolt. The characteristics of stress and displacement change in rock mass and bolt caused by stress wave are compared when the surrounding rock of underground chamber is supported with bolt or not. Numerical experimental results show that, under the action of dynamic load, the high stress area in surrounding rock can be transferred to the interior of rock mass by adding bolt to the surrounding rock of a high ground stress underground chamber, and the displacement value of each segment of bolt is basically the same. Moreover, the acoustic emission (AE) energy and AE count released by surrounding rock have been able to be reduced, and the force pattern of surrounding rock has been changed.

Propagation velocity model and two-dimensional defect imaging of stress wave in larch (Larix gmelinii) wood

The propagation law of stress wave in larch (Larix gmelinii) wood was studied in this work. External factors affecting the propagation velocity of stress wave in wood cross-section were studied using the orthogonal experiment method. The most influential factors were shown by the experimental results, and the parameters of the propagation velocity model of stress wave in larch wood were optimized. Based on the optimized propagation velocity model, combined with the traditional defect determination method, a twelve-directional stack imaging (TDSI) steps system was developed for larch wood internal defect detection. The analysis results showed that of the three external factors of temperature, moisture content, and illumination duration, temperature had the greatest influence on the propagation velocity model of stress wave in larch wood cross-section. Using TDSI to image the defective larch wood not only can locate the defective area, but also it can achieve a high imaging precision of 95.52%, and the imaging precision is unrelated to the location of the defect, which has a good quantitative defect detection effect.

Loading device of explosive stress wave in high confining pressure and dynamic response of composite structure

This paper presents an equivalent loading device of explosive stress wave to investigate the propagation law of stress wave in high-geo-stress rock mass under explosive disturbance. The loading device was used to simulate the propagation law of explosion stress wave in water and composite structure under high confining pressure. The device can generate plane stress waves, and the stress waveforms measured by sensors arranged on the same plane have good consistency. According to the time sequence relationship of the stress curve, the propagation law of the stress wave between layers was obtained, and the stress wave has no obvious attenuation. Within a certain hydrostatic pressure range, with the increase of pressure, the peak value of the stress wave showed an upward trend, while there was little change in positive pressure holding time. The successful development of the stress wave equivalent loading device makes the explosive disturbance loading under high ground stress safe and controllable. It is a new type of deep geomechanical test method.

Research on propagation law of one-dimensional stress wave in jointed rock mass under in-situ stress

The propagation law of stress wave in jointed rock mass under in-situ stress has important engineering significance on blasting excavation and protection engineering design of deep rock mass. Based on theoretical analysis, the propagation law of stress wave across multiple nonlinear deformation joints under the initial stress is studied. Firstly, the propagation equation of stress wave across multiple nonlinear joints considering the influence of initial stresses is established, through the discontinuous deformation method (DDM) and the recursive analysis method of stress wave in time domain. On this basis, parametric studies are conducted for the effects of stress wave propagation, such as initial stress, the amplitude of stress wave, the distance and the number of joints. The results show that the existence of initial stress will affect the propagation of stress wave, the geometric distribution of joints, such as spacing and number, can also cause the change of stress wave transmission coefficients, and the amplitude of incident wave varies can also lead to the change of stress wave propagation.

Propagation Law of Stress Wave and Cracks in Non-penetrating Jointed Rock Mass: A Numerical Study Based on Particle Flow Code

It is important to study the interaction between stress wave propagation and rock joints to prevent dynamic disasters in rock mass engineering. In this manuscript, the numerical SHPB system and sandstone rock model were established firstly and then considering different joint vertical and horizontal distance analyzed the propagation law of stress wave and cracks. The research results show that the vertical and horizontal distance of the joints affect the waveform, rise time, wave coefficient of the transmitted and reflected stress wave when compared with the intact rock specimens. The crack propagation process can be divided into three stages. Under the influence of the joint vertical distance, the cracks spread like a “circle” and with the increase of the joint vertical distance, the size of the crack “circle” increases. Besides, there are some cracks spread like a “circle” within a certain horizontal distance with the vertical distance fixed. However, with the increase of the horizontal distance, the circle shape of the cracks change into a slanted crack strip when beyond a certain horizontal distance.

Numerical simulation of column charge explosive in rock masses with particle flow code

The detonation of a column charge and the damage process in a rock mass are simulated in this study by the particle flow code method. The expansion loading method and the dynamic boundary treatment method are established according to the discrete element mechanism. Mechanical parameters are calibrated on the basis of the Starfield superposition principle and the dynamic compensation method. Dynamic stiffness and microscopic parameters are used for numerical simulations. Numerical test results are consistent with lab experimental test results. The velocity attenuation law is compared with that of theoretical results, and the blasting crater action index is compared with that of field test results, to verify the rationality of the numerical explosion model of the column charge. The mechanism of the rock breaking process under column charge explosion is analyzed. Stress wave propagation, detonation wave propagation, and crack extension are investigated. The stress wave gradient law is obtained, and the effects of blasting rock breaking, crack extension, and explosion effect outside the blasting crater area are determined with different initiation modes. The research method can explain the blasting stress wave propagation law and describe the dynamical failure process in rock masses. This study can provide a reliable numerical analysis method for follow-up blasting research and offer practical guidance on engineering blasting.

Experimental Research on Directional Blasting in Pre-cutting Hard Coal Seam Roof

Aiming at the problem of impact ground pressure caused by the hard roof of goaf in coal mining face, the research on pre-cutting of hard coal seam roof by directional blasting was carried out. According to the principle of energy accumulation in directional blasting, a similar simulated experiment was designed on the basis of theoretical analysis of stress wave propagation law, crack development law and forced roof caving distance. The experimental results show that the roof is pre-cut by directional blasting, the integrity of the roof in front of the working face is reduced, effective pressure relief effect is obtained, the large area of overhanging roof in goaf is prevented, and the impact ground pressure disaster of the working face is relieved.

Propagation Characteristics of Blasting Stress Waves in Layered and Jointed Rock Caverns

The existence of joint fissures makes explosive actions between rock masses more complex. Therefore, it is of great significance to carry out experiments studying blasting stress waves propagating in jointed rock masses. Based on the Froude Similarity principle, the geological mechanical models of intact rock masses and jointed rocks have been proposed. A blasting vibration experiment was carried out and demonstrated that the propagation of the blasting stress waves and changing structures have an important relationship. A numerical simulation of the blasting stress wave propagation law in a layered jointed rock mass was carried out. This study found that with an increase in the joint angle, the peak velocity of blasting stress wave, transmission coefficient and reflection coefficient all gradually increased, while the attenuation coefficient gradually decreased. With an increase in joint spacing, the attenuation rate of the blasting stress waves increased.

Influence of the connecting condition on the dynamic buckling of longitudinal impact for an elastic rod

The stress wave propagation law and dynamic buckling critical velocity are formulated and solved by considering a general axial connecting boundary for a slender elastic straight rod impacted by a rigid body. The influence of connecting stiffness on the critical velocity is investigated with varied impactor mass and buckling time. The influences of rod length and rod mass on the critical velocity are also discussed. It is found that greater connecting stiffness leads to larger stress amplitude, and further results in lower critical velocity. It is particularly noteworthy that when the connecting stiffness is less than a certain value, dynamic buckling only occurs before stress wave reflects off the connecting end. It is also shown that longer rod with larger slenderness ratio is easier to buckle, and the critical velocity for a larger-mass rod is higher than that for a lighter rod with the same geometry.