Study on the Modification of Confining Rock for Protecting Coal Roadways against Impact Loads from a Roof Stratum

Promoting the ability of anti-bursting of the confining rock of a coal roadway is of significant importance to the safe production of a coal mine. In particular, in deep-buried coal mines, highly frequent rock burst occurs due to large earth pressure and complex geological conditions, which needs serious improvement. This paper investigated a type of confining rock modified method, which can modify the physical properties of the surrounding rock and form a crack region and a reinforced region by blasting and grouting reinforcement. Based on a set of physical model experiments and numerical modeling, the results of a comparative analysis between a normal roadway and the modified roadway in the static stress redistribution, dynamic stress, damage evolution, and energy dissipation suggest that the modified confining rock is capable of protecting the coal roadway against rock burst from roof stratum, obviously reducing and transferring the concentered static–dynamic stress out of the cracked region, dissipating the dynamic energy by plastic damage in the cracked region, and keeping the integrity of the reinforced region. In addition, the velocity of the dynamic stress vibration wave at the surface of the modified coal roadway is obviously reduced, which is beneficial for decreasing the movement of cracked rock blocks and protecting the lives and goods in the coal roadway.

Well productivity and reservoir recovery enhancement with using vibration wave impact technology

The use of physical fields of elastic vibrations in methods of increasing well productivity and oil recovery is presented. Borehole hydrodynamic generators of elastic vibrations are the most preferable for performing vibration-wave treatments of the bottom-hole zone. Many generator designs lack reasonable parameters for the generated pressure fluctuations. In this regard, it is necessary a bench and oilfield research practice of hydrodynamic generators various designs with an objective hardware assessment of their operating parameters.

Study on the spectrum characteristics of rock burst and the stability of the surrounding rock of a roadway in mines under dynamic load

This study analyzes the impact pressure in the Yuejin and Qianqiu coal mines in the Yimei mine area, and shows that rock bursts may be caused by damage to the overburden gravel strata caused by coal seam mining and unreasonable mining layout. Rock burst microseismic signals from the Yuejin and Qianqiu mines show that the duration of the vibration waveform is greater than 0.06 s. The fast Fourier transform shows that the low-frequency component of the rock burst accounts for a large proportion, with the main frequency being concentrated in the range between 5 and 50 Hz. A numerical simulation scheme was designed, and the extended D-P strength criterion was adopted to select the distributed load of a sinusoidal pulse in the load waveform as the dynamic load. The plastic strain energy density distribution is used to measure the tendency of the surrounding rock to impact the roadway. By changing the shock position, wave frequency, disturbance intensity, tunnel section shape, and buried depth, it is seen that when a (vibration wave amplitude) = 2.0 m/s2, f (vibration wave frequency) = 40 Hz, H (roadway buried depth) = 1000 m, θ (the angle between the impact position of the seismic wave and the center of the roadway) = 180°, and the roadway section is horseshoe-shaped, the tendency of the surrounding rock to impact the roadway is higher. Under the same conditions, the impact tendency of the surrounding rock on the roadway is the smallest and second smallest when the roadway is circular and straight-wall arched, respectively.

Prediction of Vibration Velocity of Bench Blasting Reflecting Negative Elevation Effect

In the field of mine blasting practice, accurate prediction of blasting vibration is considered as a critical task. In accordance with the theory of elastic wave, the reflection of blasting vibration wave at the interface of negative elevation is analyzed in this paper. The negative elevation effect exerted by blasting vibration is interpreted considering the mechanism, and the formula of the blasting vibration prediction step (negative) V = K Q 1 / 3 / R α ⋅ 1 / H β is derived, reflecting the negative elevation effect. Besides, the formula accuracy is verified by the measured vibration velocity of the mass in the Jinou coal mine. The step (negative) formula acts as a more feasible candidate for the prediction of step blasting vibration.

The Exercise Vibration Wave Principle in Physical Rehabilitation of Children with Musculoskeletal System Disorders

The article describes the methodical and methodological possibilities of the vibration-wave principle of physical exercises in the context of its use in the physical rehabilitation of children with musculoskeletal disorders both in the conditions of the hall for movement therapy and in the aquatic environment using the example of hydrokinesis therapy. The analysis of the well-known healing properties of vibration on the human body, which can be used in the physical rehabilitation of children with musculoskeletal system disorders, is given. The known possibilities of acoustic wave effects on the musculo-fascial and skeletal systems of people are analyzed. The unique possibilities of applying the phenomena of vibration and waves not only on land but also in an aquatic environment, in conditions of hydrokinesis therapy in a pool are considered. The properties of a longitudinal elastic (acoustic) wave and its effect on the musculoskeletal system of children are characterized. The authors proposed a new concept in physical rehabilitation - "correctional acoustic internal field" on land and "correctional hydroacoustic external field" (in water). The methodological aspects of the varieties of using these fields in an autoactive (independent, conscious) version and in an imperative (forced, directing from the outside) version are considered.

Installation for Producing Mechanical Vibrations used in the Finishing of the Welded Joints Structure

The paper presents a constructive version of a mechanical vibration generator designed to be used at stress relieving of welded joints. This installation can be used on all brands of steels and welded joints, whether they have magnetic properties or not. In the generator construction a DC motor was used, in order to be able to adjust the speed more easily. The speed adjustment is made with a potentiometer, and the speed measurement is made with a tachometer. The tachometer measures the speeds based on the pulses given by a four-pointed cam rotating between the plates of a capacitor. The vibration system also contains a piezoelectric accelerograph, which is attached to the welded part subjected to vibration, in order to measure the level of vibration and the parameters of the vibration wave.