Research on Dynamic Response of Slopes With Weak Interlayers Under Mining Blasting Vibration

As blasting technology starts to be used in a wide range of areas, blast loading has led to an increasing number of geological disasters such as slope deformation, collapses, and soil slippage. Slopes with weak interlayers are more likely to be deformed and damaged under the influence of blast loading. It is of great importance to study the evolution for the deformation of slopes with weak interlayers during blasting excavation. This study constructed a slope model with a weak interlayer to investigate the influence of different factors of blasting, including explosive charge, blast radius, blast origin, and multi-hole blasting, on the internal dynamic response. The deformation mechanism of slopes with weak interlayers under the influence of blast loading was analyzed. Test results show that each layer of the model had a different displacement response (uncoordinated dynamic response) to blasting with various factors. Explosive energy and the pattern of dynamic response of each layer varied depending on different settings of blasting factors such as explosive charge, blast radius, blast origin, and detonation initiation method. When the explosive energy produced under the influence of various factors was small, the change in the uncoordinated dynamic response between layers was significant, and the change gradually became less significant as the explosive energy increased. Therefore, this study has proposed the concept of critical explosive energy, and it is speculated that when the explosive energy produced with various factors is less than critical explosive energy, the dynamic response is mainly affected by the internal structure of the slope (property difference induced geologic layers). In other words, the uncoordinated motion of material’s particles in each layer is caused by different limitations and the degree of movement of the particles, which leads to the uncoordinated dynamic response and uncoordinated deformation of each layer. If the explosive energy is greater than the critical value, the dynamic response of each layer is mainly affected by the explosive energy. The differences in the internal structure of the slope are negligible, and the incoordination of dynamic responses between layers gradually weakens and tends to synchronize.

Generalized graphic-analytical model for evaluation of the fatality / structural collapse production mechanism on a building affected by an explosion

The paper highlights the generalized grapho-analytical model of analysis and evaluation of the mechanism of occurrence of the event scenario for the production of fatality/structural collapse in the case of a building affected by explosion. This mathematical model is based on research results in the field of civil explosives for the technological/occupational risks estimation and assessment, as well as threats to the security of protected areas that may be vulnerable through acts of malice. The process of quantitative risk assessment associated with explosion phenomena as a result of the detonation of an explosive charge, allows estimating result indicators based on the use of algorithms and models specific to associated hazards, in order to model the effects and consequences of event scenarios.

Pulse load on a stationary barrier during an explosion in water

С использованием экспериментальных данных о взрывах в воде найдена аналитическая зависимость распределения удельного импульса взрывной нагрузки по длине балки. Учтены эффекты отражения возмущенного потока воды от поверхности преграды, глубина ее расположения в водоёме, взаимное расположение сферического заряда ВВ и преграды в воде, физические характеристики заряда. Using experimental data on explosions in water, an analytical dependence of the distribution of the specific impulse of the explosive load along the length of the beam is found. The effects of reflection of the disturbed water flow from the barrier surface, the depth of its location in the reservoir, the mutual location of the spherical explosive charge and the barrier in the water, the physical characteristics of the charge are taken into account.

Optimization study of blasting operations in Roşia Poieni open pit mine, Romania

Purpose. Drilling-blasting technology is one of the simplest and most often used techniques in open pit mining. This allows the excavation of a large volume of rock and useful mineral substance. The operation of blasting using the energy of explosives plays an important role in open pit exploitation, being also the key element of the blasting process through which a corresponding granulometry is obtained. This operation is a part of a series of interdependent operations, in the sense that each operation determines a certain result that will be an important element for the next operation that takes place in the working face. Consequently, the blasting operation with explosives should not be considered as an independent act. A global approach to the entire production technological process including blasting is required. Methods. In the optimization study, the basic method consisted in the analysis of the blasting operations performed at the drilling diameter of 250 mm (blasting technology used in Roşia Poieni open pit mining) and simulation of the excavation of the same rock volume, with the optimization of the explosive charge distribution at two other drilling diameters: 200 and 150 mm. Findings. The main problems when shooting 250 mm dia holes are caused by the length of the tamping in the mineralized rock that leads to the appearance of blocks with dimensions which are maximum allowed in the crusher tank (1.2-1.3 m). That is why discontinuous loads with intermediate tamping are used – the method that successfully limits their number. In order to obtain a granulometry corresponding to the primary crushing operation, which will allow to decrease the crushing costs, it is necessary to use smaller drilling diameters, but with productivity high enough to ensure the optimal development of the extraction process. Originality. Based on the performed study, it is recommended to use the discontinuous load, preserving the total length of the explosive charge. In the zones where the rocks have a Protodiakonov coefficient f > 6.5, it is recommended to apply an appropriate drilling diameter (150-200 mm) and use the intermediate tamping at 2-3 m length to limit the upper stemming area to a maximum of 7 m (to limit or eliminate the occurrence of oversized blocks). Practical implications. The research results will enhance the geometric and safety factors of the operation, limiting the explosion effect on the massif and the environment and reducing the total costs of the cutting operation. The cost of explosives and initiating materials can be reduced by using a smaller quantity of explosive gels in a dry environment (12-18 kg/hole), the difference in the explosive charge length being completed with AM 1.

Experimental Study on Ground Vibration Caused by the Blast Loading of an Explosion Vessel

To investigate the ground vibration caused by the internal blast loading of an explosion vessel while evaluating the damage caused by vibration propagation to surrounding buildings, a series of explosion vibration tests were carried out using an explosion vessel. The blasting vibration monitors recorded the vibration parameters, and the vibration velocity frequency distributions were analyzed by the Hilbert–Huang transform (HHT) method. The results show that the explosion vibration velocity is closely related to the explosive charge and propagation distance. The effect of an explosive charge and propagation distance on the vibration amplitude at frequencies of 20–60[Formula: see text]Hz is not apparent, but at frequencies of 5–10[Formula: see text]Hz, low-order frequencies are noticeable. Furthermore, the energy amplitude and vibration action duration increase with increasing explosive charge and decrease with increasing propagation distance. The results provide an essential reference for studying the propagation law and effects on ground vibration waves produced by blast loading in an explosion vessel.

Research on Damage Characteristics of Brick Masonry under Explosion Load

As the main structural component of partition wall or load-bearing wall, brick masonry has been widely used in construction engineering. However, brick and mortar are all brittle materials prone to crack. Nowadays, fireworks, gas stoves, high-pressure vessels, and other military explosives may explode to damage nearby structures. Many explosion casualties had shown that the load-bearing capacity of brick masonry decreased dramatically and cracks or fragments appeared. Previous studies mainly focused on noncontact explosion in which shock wave is the main damage element. In fact, the response and damage effect of brick masonry wall under contact explosion are more complex, which attracts more attention now. In order to explore the damage characteristics of brick masonry under explosion load, a series of simulations and verification experiments are conducted. RHT and MO granular material models are introduced to describe the behaviour of brick and masonry, respectively, in simulation. The combination effect of front compressive wave and back tensile wave are main factors influencing the breakage of masonry wall. The experimental results are well in accordance with the simulation results. The front cross section dimension of crater is closely related to the radius of spherical explosive charge. A power function predictive model is developed to express the relationship between the radius of hole and the radius of explosive. Furthermore, with increasing the quantity of explosive charge, the number and ejection velocity of fragments are all increased. The relationship between maximum ejection velocity and the quantity of explosive also can be expressed as a power function model.

Evaluation of internal blast resistance of bi-directionally prestressed concrete tubular structure according to ANFO explosive charge weight

When extreme loading from an internal is applied to prestressed concrete (PSC) structures, serious property damage and human casualties may occur. However, existing designs for PSC structures such as prestressed concrete containment vessels (PCCV) do not include features to protect the structure from the blasts. Therefore, the internal blast resistance capacity of PSC structures is evaluated by internal blast tests on bi-directional PSC tubular members. The goal of the study was to obtain the structural behavior data from an internal detonation. The ANFO charges were detonated at the center of the mid-span of the tube specimen with a standoff distance of 1,000 mm. The data acquired included blast pressure, deflection, strain, crack pattern, and prestressing loss. The data are used derive the equations to calculate the required internal blast charge weight to fail a real-scale PCCV and to calibrate a commercial simulation program to be used for internal blast simulations.

Influence of Meteorological Parameters on Explosive Charge and Stemming Length Predictions in Clay Soil during Blasting Using Artificial Neural Networks

The influence of the meteorological parameters (precipitation and air temperature) during blasting in clay has a direct impact on the success of blasting. In the case of large amounts of precipitation (rain and snow) recorded in the subject area, blasting in clays cannot be carried out due to the grain of the clay and the inability to access the subject area. Moreover, the air temperature in the subject area affects the blasting performance. The most ideal temperature for blasting in clays is between 15 and 25 °C because then the clay has the best geotechnical characteristics. The research was conducted on the exploitation field Cukavec II, which is located near the city of Varaždin in the Republic of Croatia. Amount of precipitation and air temperature were considered to obtain the best blasting effect. Influence of meteorological parameters on the amount of the explosive charge and stemming length when blasting in clays was demonstrated via models based on Artificial Neural Networks (ANN). The ANN model network consists of a Long Short-term Memory (LSTM) part to process time dependent meteorological data, and fully connected layers to process blasting input data. Two types of explosive charges were compared, Pakaex and Permonex V19.

Experimental Study on the Damage Characteristics of Polymer Slabs Subjected to Air Contact and Close-In Explosions

As a new antiseepage reinforcement material, polyurethane grouting material has been widely studied in terms of its static mechanical properties. However, research on its dynamic mechanical properties is relatively rare. In this research, considering the influence of the explosive charge weight, the air contact and close-in explosion experiments of polymer slabs were carried out. The failure mode and damage spatial distribution characteristics of polymer slabs were explored. Pressure time history curve of air shock wave was obtained using an air shock wave tester. The influence of polymer slabs on the propagation of air explosion shock wave was compared and analyzed. The results show that, under the air contact explosion, the polymer slab mainly suffers local damage, while under close-in explosion, overall damage is the main damage mode. With the increase of the explosive charge weight, the failure mode of the polymer slab transits from surface crack and slight spalling to local and whole crushing.