Dynamic response analysis of blocks-combined dam under impact load

Landslide barrier structures are a useful mitigation tool for managing debris flow risks, working to slow their momentum or alter their course to avoid damage to downslope inhabitants or infrastructure. Their design is typically governed by the expected impact force, which is predicted using analytical models or numerical simulations. These methods only provide estimates of the peak force and require detailed information about the flow at impact that can be difficult to accurately predict. In this experimental study, we use the large Queen’s University Landslide Flume to explore the relative contributions of the fluid and solid phases of a multi-phase flow on the structural demand on a barrier. Impact forces following dam break experiments of up to 0.4 m3 of material, released from the top of a 6.5 m long slope inclined at 30 degrees are explored for material releases of pure water, dry granular particles (3 mm diameter), and fully saturated water-grain mixtures. Temporal impact behaviour captured using ultrahigh speed imaging (7500 fps) is correlated with the time series of impact load measured at the barrier. The addition of the fluid phase was found to significantly increase the impact force and the maximum run-up height along the barrier. Further tests are performed using single-graded particles ranging in diameter from 3-25 mm. Over this range, the dilatancy of the flow increased with increasing particle size, leading to reduced influence of the fluid phase on the flow dynamics and decreased impact force, despite similar flow velocities (4-5 m/s).To explore the performance of an alternate barrier type, impact tests were conducted using a single-slit barrier with varying slit size (30-240 mm) and grain diameter (3-25 mm), providing a wide range of relative slit sizes. A benefit of the slit barrier design is its ability to ‘self-clean,’ letting material slowly release through the slit following an impact event. This allows the barrier to remain effective in halting a secondary debris flow without maintenance clearing between impacts. To explore the dynamics of this subsequent event, secondary releases were performed for both solid and slit barrier designs. Barrier performance is investigated using load measurement, LiDAR imaging, and PIV analysis. The solid barrier experienced overtopping under the second release. The addition of the slit alters the deposit geometry, generating two slopes on either slide of the slit which act as redirection berms, altering the flow behaviour and reducing the runup height and force of the second impact. The results of this large-scale experimental study provide detailed data on the flow behaviour, impact mechanics, and barrier efficiency for a range of debris flow compositions, particle sizes, and slit sizes under single and sequential impacts, suitable for numerical model benchmark tests that may lead to improved barrier design.

This study focuses on the behavior of a three-dimensional reinforced concrete dapped-end beam subjected to the effects of impact velocity and dapped-end beam cross-section geometry by numerical simulation using ABAQUS (V6.14) software under a constant impact load. The finite element software ABAQUS is utilized to simulate and analyze the drop impact to obtain accurate and detailed results. A sudden drop impact is a short-duration dynamic load that could involve very large deformations and damage to the reinforced concrete dapped-end beam. The finite element analysis has been completed by creating the geometry, material properties, boundary conditions, and loading conditions. In this study, a total of seven analyzes were conducted with different parameters, i.e., the effect of the velocity of the impact load and the geometry of the dapped-end beam cross-section. From the finite element analysis results, it can be concluded that as the impact velocity increases, the impact force and mid-span displacement of the reinforced concrete dapped-end beam also increases. The higher the impact velocity, the greater the amount of damage caused throughout the RC beam. When the recess length increases from 200 mm to 500 mm, the deflection increases by 13%. The depth of the nib has a great influence on the impact response and deflection of the reinforced concrete dapped end beam. The ABAQUS output shows that increasing the dapped end beam nib depth from 260 mm to 450 mm reduces the impact load by 50%, from 22733.6 N to 13640.16 N. On the other hand, the nib depth increased from 260 mm to 450 mm, and the maximum deflection was reduced from 1.10245 mm to 0.6892 mm, i.e., a 46.1% reduction.

Loading rate effects on the responses of simply supported RC beams subjected to the combination of impact and blast loads

To study the particle size distribution and energy variation law of hard coal under a load, an impact compression test of hard coal specimens under different impact loading conditions was carried out using a Φ50 mm diameter Separate Hopkinson Press Bar (SHPB) test system. We implemented the theory of dynamic impact energy of rock to establish the calculation expression of hard coal impact crushing energy dissipation, and we established the Weibull distribution model of a crushing body to analyze the impact velocity in relation to the particle size distribution of hard coal crushing and crushing energy consumption. The results demonstrate that due to the different original states of the specimens, the damage to the specimens under static action is in the mode of conjugate plane shear damage, single bevel shear damage, and tensile damage. The damage process of the specimen under impact load loading is divided into three stages: elastic deformation, elastic–plastic deformation, and plastic softening, while the increase in the strain rate caused the peak stress of the specimen to increase. The Weibull distribution can characterize the impact crushing size distribution of hard coal specimens very well. The parameter of coal rock crushing degree is a power function that is influenced by the impact velocity; the greater the impact velocity, the higher the coal rock crushing degree, but the characteristic index of coal rock crushing fluctuates with the increase in impact velocity. As the impact velocity increases, the incident energy and reflected energy increase linearly, while the transmitted energy increases first and then decreases. The dissipation energy of coal rock crushing also increases linearly with the impact velocity. There is no obvious regular change between the energy dissipation rate of coal rock and impact velocity during impact damage, and the dissipated energy of macroscopic crushing only accounts for 10~20% of the incident energy; most of the energy is used for damping loss and damage loss.

Dynamic crushing behaviors and failure of cylindrical lithium-ion batteries subjected to impact loading

The finite element model of oblique penetration of short-rod projectile into a thin metal target was established and the effectiveness of the model was verified to study the oblique penetration law of short-rod projectile into a thin metal target. The simulation calculation of short-rod projectile penetrating thin metal targets with different obliquities at different impact velocities was carried out. The simulation results show that the critical ricochet velocity of the projectile increased with the increase of the obliquity of the target plate, as well as the increment of the critical ricochet velocity of the projectile. With the increase in the obliquity of the target plate, the ultimate penetration velocity of the projectile increases exponentially, and when the obliquity is large, the ultimate penetration velocity increases sharply. When the projectile ricocheted without invading the target, the velocity attenuation of the projectile increased with the increase of the impact velocity, whereas the mass of the residual projectile decreased. However, when the impact velocity exceeds the ultimate penetration velocity of the projectile to the target plate, the velocity attenuation of the projectile decreased and the mass of the residual projectile increased with the increase of the impact velocity. With the increase of impact velocity, the included angle decreased gradually, and the decreasing trend also slowed down. When the impact velocity was just greater than the ultimate penetration velocity, the included angle was the largest. At the same impact velocity, the greater the obliquity of the target plate, the greater the included angle. This study is of great significance to reveal the critical ricochet and ultimate penetration of projectile, the velocity, mass, and trajectory change in the process of penetration, as well as the damage of projectile to the target plate.

Reinforced concrete members under impact loading stress may be destroyed in a split period. Because of the need to investigate the impact resistance of reinforced concrete members, this issue remains a much-debated topic. This study investigates the response of reinforced concrete (RC) square members under an unequal lateral impact force. The performance of RC members under the effect of impact load is examined using a drop hammer impact test system. The importance of unequal lateral impact load is highlighted and addressed by examining RC members’ failure mode and dynamic response characteristics. Four types of RC members are experimentally investigated in detail. A finite element method (FEM) modeling is proposed to predict the impact responses of the RC members. Moreover, the effects of the impact position, height, and hammer mass on the dynamic response characteristics under an impact force are evaluated. The predictions of the proposed numerical model are validated against experimental results, emphasizing impact force history, deflection time history, and failure modes. Results indicate the viability of the FEM model. The findings from the experimental and numerical studies can improve the impact-resistant performance of reinforced concrete members.

The new-type projectile with the penetration and arson function has been playing an important role in modern warfare increasingly with new technique development. A new-type multiple-function small caliber projectile with a self-powered ignition system was designed. The miniaturization design of the self-powered ignition system greatly reduces the size of projectile. The ignition process, ignition energy, and ignition delay time of the self-powered ignition system were analyzed by experiment and finite element simulation. The effects of impact velocity and the mass of the mass block on ignition energy were analyzed. The results show that the self-powered ignition system can ignite stably when the impact velocity is higher than 51 m/s and the mass block is 4 g. The slope of the output energy curve decreases with the increase of the mass blocks; the output energy increases first and then decreases with the increase of impact velocity. According to the critical ignition experimental curve, the appropriate mass block is selected to make the self-powered ignition system ignite stably, and the ignition delay is related to impact velocity, and the higher the impact velocity is, the shorter the ignition delay is under the condition of given mass block.

With the large-scale construction and long-term operation of underground reservoirs in coal mines, the problem of surrounding rock stability under long-term water immersion has become increasingly prominent. Therefore, clarifying the dynamic response of rocks under long-term immersion and impact loads is of great theoretical significance for ensuring the safe operation of coal mine reservoirs throughout their entire life cycle. In this study, sandstone samples were immersed in water for 0, 3, 30, 90 and 180 days respectively. The microstructure characterization and dynamic tests were carried out by using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), computed tomography (CT), and an improved separated Hopkinson compression bar (SHPB) system. The results show that: (1) The combined results of SEM, NMR and CT tests indicate long-term impregnation reduces the proportion of micropores and increases the proportion of mesopores and macropores. The total dissolved solids (TDS) concentration in the impregnating solution increases with time, and the pH value of the solution first rises and then decreases with the extension of the immersion time. (2) The faster the impact velocity, the greater the frequency and amplitude of the stress wave generated. The water saturation gradually increases with immersion, weakening the discontinuity of acoustic impedance and reducing the reflection coefficient at the interface. (3) The increase in impact velocity intensifies fragmentation and promotes the development of complex fracture networks. With the extension of immersion time, the expansion of clay minerals such as montmorillonite will generate expansion stress, thereby creating micro-cracks, which leads to a higher fractal dimension of the crack network and eventually stabilizes over time. (4) Under the action of impact loads, the proportion of intergranular fractures increases with the extension of immersion time. However, at high impact speeds, the relative strength contrast between the cementing material and quartz particles leads to an increase in transgranular fracture. Overall, this study provides guidance for the safe design and operation of underground reservoirs in coal mines.

Stress waves propagating through multiple parallel fractures are attenuated due to the multiple wave reflections and transmissions at the fractures. The dynamic response of a layered medium under an impact load is systematically studied by a model test in this paper. The effects of the impact energy, number of joints, thickness of the medium and joint layer, material properties of the cementation layer, and other factors of the dynamic stress propagation and attenuation of layered media are analyzed. Studies have shown that Sadovsky’s empirical formula fits the attenuation law of vertical peak velocity well, and the obtained attenuation coefficient k and index b can be used for reflecting the dynamic response characteristics of layered media. The attenuation coefficient k is positively correlated with the impact height and negatively correlated with the plate thickness in a single-layer plate impact test. The thickness of the medium layer is the main factor affecting the vibration response of the layered medium in the impact test of the multi-layer slab. The medium thickness, the number of medium layers, and the number of joints have little influence. The different cementation materials and the change of cementation thickness will have a great influence on the dynamic response of layered media, when the cementation layer is filled with joint surfaces for the impact test of multi-layer plates.

Droplet impact on cylindrical surfaces: Effects of surface wettability, initial impact velocity, and cylinder size

Flume investigation of debris flow entrained boulders with cylindrical baffles and a rigid barrier

Castor is an important oil crop. Impact damage is critical in the process of castor capsule shelling, directly affecting the shelling effect of castor seeds. An experiment was taken to investigate it. To study the damage degree of castor capsule under the impact, water content, impact height, and impact angle were taken as test factors, and the maximum impact force and normal deformation were taken as test indexes. The combination optimization was carried out through the multi-objective genetic algorithm. The results show that the impact height has a significant effect on the maximum deformation (p<=0.01), and the water content and impact angle have a significant impact on the impact force (p<=0.05). The height and angle have a significant impact on the deformation (p<=0.01), and the water content has a significant impact on the deformation (p<=0.05).

In this paper, a discussion is presented about the impact‐induced damage suffered by bridge pier columns during rockfall events through model tests and impact force, column top displacement, stress‐strain response, and other parameters in relation to the process of impact. On this basis, the following conclusions are drawn. Firstly, the impact force, as well as the displacement and strain of the column top, increases rapidly after taking a hit, while the displacement is reduced after reaching its maximum. Secondly, at the same falling height, the higher the impact position, the smaller the peak of impact force and the longer the attenuation period. Thirdly, at the same impact height, the impact energy, the displacement of the column top, and the peak of the impact force increase as the falling height of the pendulum ball is on the rise, but the attenuation period remains unchanged. Fourthly, the failure mode of column impacted by the swing ball conforms to shear‐flexural failure. Fifthly, it is recommended to strengthen the preventative measures for those weak positions like 1/2 height and 1/4 height of bridge pier, so as to minimize the potential damage caused by rockfalls. Besides, a theoretical formula used to estimate the maximum impact force is proposed. Lastly, under the axial load of bridge deck, the performance of the pier in impact resistance under rockfall is better and the damage is less severe than in the experimental impact test. The axial load applied by the deck imposes some constraints on the pier, thus reducing concrete damage. The research results can contribute to the research on addressing the rockfall‐bridge pier collision problem. The experimental research demonstrates its theoretical significance to engineering for the prevention of rockfall.

Debris flow is a huge hazard to downstream lives and property, which must be controlled by engineering. The construction of gravity sand retaining dams (hereinafter referred to as sand retaining dams) from the formation area to the circulation area is one of the quick and effective measures. Prevention and control projects often play a role in controlling the development trend of debris flow and reducing the size and frequency of debris flow. Debris flow will cause erosion and impact damage to the dam foundation of sand retaining dams. For the debris flow impact force, the most dangerous part is usually designed based on the largest impact force, while all parts of the dam body are designed according to the most dangerous part, which wastes materials. It's not economical. In this study, a debris flow gully is selected as the research model. Considering the interaction between debris flow and sand retaining dam, the impact simulation of debris flow on sand retaining dam was carried out. The research results show that the existence of the sand retaining dam hinders the movement process of debris flow, changes its speed and direction of movement, and in addition, the impact force varies at different places of upstream face of sand retaining dam. Research results provide a scientific and reasonable theoretical basis and design reference for the stability of sand retaining dam under debris flow impact impact. This will, to a certain extent, have important social needs and practical significance for disaster reduction to improve the technical level of debris flow prevention projects.