VIBRATING VELOCITY RECONSTRUC-TION USING IBEM AND TIKHONOV REGULARIZATION

The inverse problem to determine the vibrating velocity from known exteriorfield measurement pressure, involves the solution of a discrete ill-posed problem. To facilitate thecomputation of a meaningful approximate solution possible, the indirect boundary element method(IBEM) code for investigating vibration velocity reconstruction and Tikhonov regularization methodby means of singular value decomposition (SVD) are used. The amount of regularization is determinedby a regularization parameter. Its optimal value is given by the L-curve approach. Numerical resultsindicate the reconstructed normal surface velocity is a good approximation to the real source.

Vibration velocity and frequency of underwater short-hole blasting

Based on the measuring data of underwater blasting vibration and theregression analysis results of these data, two formulae usually used of blasting vibration velocitywere compared. Factors that can affect blasting vibration and frequency were summarized andanalyzed. It is thought that the effect of the number of freedom face and burden direction onblasting vibration should be considered during blasting design. Based on the relevant researchresults and the regression results of these data, a formula to calculate under water blastingfrequency was put forward.

3D Characteristic Diagram of Acoustically Induced Surface Vibration with Different Landmines Buried

The 3D characteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system for acoustic landmine detection and the method of scanning detection, the 3D characteristic diagrams of surface vibration were measured when different objects were buried underground, including big plastic landmine, small plastic landmine, big metal landmine and bricks. The results show that, under the given conditions, the surface vibration amplitudes of big plastic landmine, big metal landmine, small plastic landmine and bricks decrease in turn. The 3D characteristic diagrams of surface vibration can be used to further identify the locations of buried landmines.

Propagation characteristics of vibration waves induced in surrounding rock by tunneling blasting

The effect of blasting vibration waves on surrounding rock and supporting structures is an important field in underground engineering. In this paper, the separation variable method is used to solve the displacement potential function for the propagation of the blasting vibration waves. In the axis coordinate system, the particle motion and stress change with axial distance, radial distance and time is obtained in surrounding rock. The peak particle velocity law in surrounding rock under different blast loads and surrounding rock parameters is discussed.In addition, the particle vibration characteristics in the surrounding rock are studied using numerical simulations method. The results shows that the peak particle velocity in surrounding rock appears negative exponent attenuation with the increase of axial distance, but it appears positive and negative fluctuations in radial direction. This phenomenon is a new discovery and it has been rarely investigated before. Moreover, the peak particle velocity attenuates more quickly and intensely in the near blasting field,which means that the supporting structure in a shorter distance away from the heading face is vulnerable to the impact of blasting vibration. Theattenuation of blasting vibration velocity is closely related to charge length, blasting load amplitude,attenuation index and rock elastic modulus. The numerical simulation accomplishes the same results and then demonstrates the validity of theoretical results.

Vibration Superposition in Tunnel Blasting with Millisecond Delay

According to explosion dynamics and elastic wave theory, the models of particle vibration velocity for simultaneous blasting and milliseeond blasting are built. In the models, influential factors such as delay interval and charge quantity, are considered. The calculated vibration velocity is compared with the field test results, which shows that the theoretical values are close to the experimental ones. Meanwhile, the particle vibration velocity decreases quickly with time due to the damping of rock mass and has a harmonic motion, and the particle vibration velocity of millisecond blasting has short interval. The superposition of particle vibration velocities may reduce vibration because of wave interference, or magnify the surrounding rock response to the blastinginduced vibration.

RESPONSE CHARACTERISTICS OF WIND EXCITED CABLES WITH ARTIFICIAL RIVULET

A wind tunnel investigation of response characteristics of cables with artificial rivulet is presented. A series of cable section models of different mass and stiffness and damping ratio were. designed with artificial rivulet. They were tested in smooth flow under different wind speed and yaw angle and for different position of artificial rivulet. The measured response of cable models was then analyzed and compared with the experimental results obtained by other researchers and the existing theories for wind-induced cable vibration. The results show that the measured response of horizontal cable models with artificial rivulet could be well predicted by Den Hartog' s galloping theory when wind is normal to the cable axis. For the wind with certain yaw angles, the cable models with artificial rivulet exhibit velocity-restricted response characteristics.