Features of modeling of stress and strain waves in an anisotropic medium on the example of a wooden element

This article describes the hypotheses of the occurrence, propagation, and modification of stress and strain waves caused by external loads in isotropic and anisotropic infinite and finite elastic media. A model of an infinite elastic medium experiencing a point external impulse is presented. The model demonstrates the propagation of a longitudinal plane wave. Compaction and rarefaction of the medium are observed in the plane with wave propagation. A graph of changes in the amplitude of a longitudinal plane wave is presented in the same coordinate system. The problem is posed of expanding the numerical model of a finite elastic medium in the form of an anisotropic wooden rod experiencing a plane external impulse. The model should demonstrate the propagation of longitudinal and transverse waves and describe the volumetric deformation of an anisotropic material. Compaction and rarefaction of the medium are shown in the plane, coinciding with the direction of wave propagation. A graph of the change in the shear wave amplitude is presented in the same coordinate system. The combination of these two graphsreveals the difference in wave propagation velocities and the combination of amplitudes. The model will make it possible to identify the presence of Rayleigh waves and to describe the reflection of waves from the boundary of the medium.

Analyzing methods of determining pre-destruction of blast hole vicinity

The level of deformation of the rock massif of a blasted slab must be planned in advance, depending on the required results of blasting. Thus the energy costs of barren rock overfilling as part of preparing for overburden excavation are inefficient. On the contrary, an increase in the blast energy spent on degrading and breaking the ore mass is an efficient measure of preparing for the excavation of mineral wealth. There are currently two methods used to determine the pre-destruction of a blasted rock massif. The first one is based on determining the number of strain waves passing through locations of borehole charges. However, this method fails to determine the preliminary rock destruction level. The second method is based on determining coefficients of the pre-destruction of a rock massif by these strain waves. The merit of this method is that it allows evaluating the quality pattern of the pre-destruction of a rock massif. The procedure of considering the fraction of energy of the strain waves, reflected by the shielding rock mass to the destructive amount of blasting charges and refracted to this destroyed rock, is proposed.

Tidal Calibration of Multicomponent Borehole Strainmeters and Validation of the Method Using Surface Waves

We conducted in-situ calibration of fifteen multicomponent borehole strainmeters deployed in and around the expected focal zones of the Nankai megathrust earthquake. The in-situ calibration method compares tidal strain observed by the borehole strainmeters with predicted tidal strains from the solid Earth’s tide and oceanic tidal loading. Then we obtained a calibration matrix to transfer observed strain data to the regional strain field. We estimated the oceanic tidal loading accurately using a Green’s function, which takes the depth of deployment into consideration. We calculated four sets of calibration matrices using combinations of any three of a group of four gauges as well as a calibration matrix using all four gauges. The estimated calibration matrix was validated by comparing observed seismic strain waves after applying the calibration matrix with theoretical seismic strain waves excited by the 2010 Chile earthquake (Mw 8.8). The in-situ calibration was found to be appropriate for all eleven Ishii-type borehole strainmeters and for one of the four Gladwin Tensor Strainmeters (GTSMs). It was also effective with respect to two shear strains for two of the other three GTSMs.