Studium seizmických projevů v okolí ražby mělkých podzemních děl

Abstract

PhD doctoral thesis deals with the study of seismic effects of blasting operations at small distances from the source of vibration, i.e. in the near zone. The thesis summarizes the results of the seismic measurements; the nearest distance of sensors was the first meters. Experimental measurements were carried out during excavation of six tunnels in the Czech Republic, in which blasting operations were used as part of the driving technology. It was a shallow tunnelling performed in different geological conditions. Sensors were placed directly in the workings, or on the surface above excavation. The measurements were realized using three-component sensors and a digital recording apparatuses. Analyses of measured data (vibration velocity) enabled with respect Langefors´ relationship to calculate empirical parameter K (transfer constant) for near zone in those locations. The main result of the research is completion and specification knowledge of the vibration effect generated by blasting operations in small distance from the source of vibration.

Particular attention was paid to the measurement methodology in the near zone. The first experimental measurements showed that the establishment of the sensors has a significant impact on both the value of the measured maximum vibration amplitudes, and frequency range of the records. Comparative measurements were realized to analyse different anchoring of sensors, both in the laboratory and in-situ inside and outside of the underground workings. The results were interpreted in amplitude and frequency domain. These measurements revealed the effectiveness of the hard anchoring the sensor during the measurement in the near zone and a significant influence on set-up of the sensor without anchoring.

In some selected cases, data from experimental measurements were used for confrontation with the results of simplified, two-dimensional mathematical models of dynamic response. All models were created in a programming system PLAXIS 2D with dynamic modulus, working on finite element method. To accept certain simplifications and certain imperfections in two-dimensional model, the applicability of this program for the solution of the dynamic tasks has been demonstrated.