The attenuation of stress waves in fluid saturated porous rock

The dynamic mechanical frequency spectrum and temperature spectrum measurements of dry and saturated sandstone with three different porosity are conducted by use of the viscoelastic spectrum instrument in the 0.01～100 Hz frequency region. The frequency responses of the attenuation and modulus at different temperature peaks are obtained. With increase of the porosity and the loss of the complex modulus, the attenuation in the saturated sandstones is increased, and the frequency dispersion is enhanced. The relation between the frequency spectrum and the temperature spectrum are also discussed.

Attenuation of stress wave in sandstone

This article has processed the experimental study of stress wave propagation using Hopkinson Pressure Bar, andmeasured with groups of PVDF stress sensors, obtained the waveform characteristics and the attenuation constant, and got the dynamic constitutive relations using Lagrangian analysis method.

Tomography of the dynamic stress coefficient for stress wave prediction in sedimentary rock layer under the mining additional stress

In this study,the tomography of dynamic stress coefficient(TDSC)was established based on a mechanical model of stress wave propagation in bedding planes and a mathematical model of the stress wave attenuation in rock masses.The reliability of the TDSC was verified by a linear bedding plane model and field monitoring.Generally,the TDSC in the dynamic stress propagation of bedding planes increases with the following conditions:(1)the increase of the normal stiffness of the bedding plane,(2)the increase of the incident angle of the stress wave,(3)the decrease of the incident frequency of the stress wave,or(4)the growth of three ratios(the ratios of rock densities,elastic moduli,and the Poisson’s ratios)of rocks on either side of bedding planes.The additional stress weakens TDSC linearly and slowly during the stress wave propagation in bedding planes,and the weakening effect increases with the growth of the three ratios.Besides,the TDSC decreases exponentially in the rock mass as propagation distance increases.In a field case,the TDSC decreases significantly as vertical and horizontal distances increase and its wave range increases as vertical distance increases in the sedimentary rock layers.

Blast damage zone strength reduction method for deep cavern excavation and its application

The drill and blast(D&B)method is widely used to excavate underground spaces,but explosions generally cause damage to the rock.Still,no blast simulation method can provide computational accuracy and efficiency.In this paper,a blast equivalent simulation method called the blast damage zone strength reduction(BDZSR)method is proposed.This method first calculates the range of the blast-induced damage zone(BDZ)by formulae,then reduces the strength and deformation parameters of the rock within the BDZ ahead of excavation,and finally calculates the excavation damage zone(EDZ)for the D&B method by numerical simulation.This method combines stress wave attenuation,rock damage criteria and stress path variation to derive the BDZ depth calculation formulae.The formulae consider the initial geo-stress,and the reliability is verified by numerical simulations.The calculation of BDZ depth with these formulae allows the corresponding numerical simulation to avoid the time-consuming dynamic calculation process,thus greatly enhancing the calculation efficiency.The method was applied to the excavation in Jinping Class II hydropower station to verify its feasibility.The results show that the BDZSR method can be applied to blast simulation of underground caverns and provide a new way to study blast-induced damage.