Research Of GMA Vibroseis For Tunnel Seismic Geological Advance Prediction

Tunnel geological advance prediction is of great significance to reduce huge casualties and economic damage resulting from the unknown dangerous geological structures ahead during the tunnel construction. Among the prediction methods, seismic method is used most commonly. Giant Magnetostrictive Actuators (GMA) based on Giant Magnetostrictive Material (GMM) has been widely utilized as vibration source to transmit seismic in seismic prediction. Because the working principle is that GMA produces transient mechanical impact with GMM actuated by the impulse voltage, the method is proved to have severe aftershock and insufficient wave energy. To avoid the above disadvantages, this article utilized GMA as vibroseis, which can output sweep seismic wave with its frequency, phase and amplitude adjustable. Due to the weak aftershock, sufficient energy and high resolution, the GMA vibroseis can obviously extend the prediction length.According to the demand of Tunnel seismic geological advance prediction, the article carried out research on the GMA vibroseis. The research covered the actuator as well as the control-driving system, and the detailed research content is described as below:(1)According to the request of sufficient energy as well as the characteristics of GMM, the size of the GMM rod was well designed first and the form of multi-rod was proposed. Afterwards, to improve the electromagnetic conversion rate and the driving magnetic field uniformity, and increase the magnetic energy, the magnetic loop of the GMA constructed of multi GMM rods was designed, simulated and optimized with the FEM software, ANSYS.(2)Magnetic-mechanics model of multi-rod GMA was established and relationship between mechanical hysteresis and parameters of the mechanical driven part was explored. To decrease the mechanical hysteresis and improve the dynamic behavior of GMA, these parameters were optimized using the method of LinearWeighting optimization. To satisfy the demand of rigidity and allowable strength, structure and size of the spring was designed using the structural FEM software.(3) To satisfy the demand that the frequency and phase of seismic wave GMA vibroseis produces are controllable and the energy is high, circuit of driving and control system was designed and the control program was accomplished using VS2008to realize the control of seismic signal. Mathematic model of driving and control system was established for later research of control scheme.(4)To satisfy the demand that the phase of seismic wave can be controlled precisely, research was carried out on the control scheme. A feedforward method including hysteresis phase compensation and linear transfer function inverse model compensation was proposed to solve the nonlinear hysteresis and realize the precise control of the phase. At last an experiment was conducted and the experimental results verified that the feedforward method was effective.