N. I. Aleksandrova

Elastic Wave Propagation in Block Medium under Impulse Loading

The waveguide properties of a block medium are studied by an example of a discrete-periodical system of spring-connected rods. As a particular case, a chain of masses is considered. It is shown that in the rod system, impulse loading excites two groups of nonstationary waves. The velocities of their propagation are determined. The asymptotic representation is obtained for low-frequency wave at a great period of time since the process onset. The analytical estimations of excitation spectrum are derived.

The discrete Lamb problem: Elastic lattice waves in a block medium

Abstract We study the propagation of transient waves under the action of a vertical step point load on the surface of a half-space filled by a block medium. The block medium is modeled by a square lattice of masses connected by springs in the directions of the axes x , y , and in the diagonal directions. The problem is solved by two methods. Analytically, we obtain asymptotic solutions in the vicinity of the Rayleigh wave at large time intervals. Numerically, we obtain a solution for any finite time interval. We compare these solutions with each other and with the solution to the Lamb problem for an elastic medium.

Numerical-analytical investigation into impact pipe driving in soil with dry friction. Part I: Nondeformable external medium

The study focuses on propagation of longitudinal waves in an elastic pipe partly embedded in a medium with dry friction. Mathematical formulation of the problem on the impact pipe driving into the soil is based on the model of longitudinal vibration of an elastic rod with taking into account lateral resistance. The lateral resistance of soil is described by the law of the contact dry friction. Numerical and analytical solutions to problems on longitudinal impulse loading of a pipe are compared.

Dynamics of Breaking Zone Development During Explosion of a Concentrated Charge in a Brittle Medium

The deformation and failure of brittle monolithic rocks under the action of confined explosion of a concentrated charge are examined. A calculated scheme is suggested for determining the dynamics of breaking zone development. Features of the increase in radial crack area are considered.

Effect of stemming on rock breaking with explosion of a cylindrical charge

A calculation scheme is developed for the destroying action of explosion of a borehole charge in a brittle medium taking account of the ejection of stemming material and outflow of detonation product gases. The influence of different rock and explosive parameters on the efficiency of stemming application is studied.

Effect of dilation on rock breaking by explosion of a cylindrical charge

A calculation model is suggested for describing the breaking effect of the explosion of a cylindrical charge in a rock mass. It is shown that consideration of dilation of the broken rock and its compressibility in the elastic zone affects essentially the calculated values of breaking parameters.

Seismic waves in a three-dimensional block medium

We study numerically the propagation of seismic waves in a three-dimensional block medium. The medium is modelled by a spatial lattice of masses connected by elastic springs and viscous dampers. We study Lambs problem under a surface point vertical load. The cases of both step and pulse load are considered. The displacements and velocities are calculated for surface masses. The influence of the viscosity of the dampers on the attenuation of perturbations is studied. We compare our numerical results for the block medium with known analytical solutions for the elastic medium.

Crack Development under Pulse Hydraulic Fracturing of Rocks

The calculation scheme is developed for describing the hydraulic fracturing of rocks by explosion of charge in well. The investigation is conducted within the quasi-static approach to the analysis of crack propagation in the productive stratum.

Calculation of Fluid Flow in the Oil Well under the Action of Powder Gas Generator

A numerical algorithm is developed, and the parameters of fluid flow in the oil well under the action of powder charge are calculated. For different combustion conditions, the dependence of gas pressure on the time and the maximum amplitude of fluid rise are found. The value is obtained for decreasing the pressure in the well relative to the hydrostatic pressure in the stratum; the hydrostatic pressure arises in cooling down the gases to the ambient temperature.

Dynamics of Microfailures in Elastic Zone during Explosion of Spherical Charge in Rock

A calculated model is developed for explosion of spherical charge in rock; it takes into account accumulation of damages in the elastic zone under the action of blast wave. The condition, under which the density of generated microcracks reaches the critical value, is used as failure criterion. The microcrack growth rate is determined by exponential function of equivalent stress.