Application And Study On Gpr And Tem In Tunnel Geological Advanced Prediction

During tunnel excavation, tunnel geological prediction is of great significance in order to guarantee the life safety of construction workers and construction schedule to reduce the construction accidents occur. GPR and TEM as two very promising tunnel forecasting methods in a growing number of works have been widely used, but the only drawback is that still lack a comprehensive interpretation signs. Basis of collecting domestic and foreign GPR and TEM tunnel prediction success cases, compared GPR and TEM forecast results in Cenxi Tunnel, Dongwei tunnel and Lingjiao tunnel with the actual excavation, summed up an interpretaion law of common adverse geological bodies in the result Figure. At the same time using two-dimensional FDTD forward modeling of GPR tunnel prediction, get the common typical adverse geological radar reflectivity waveform, providing strong theoretical support for the establishment of the GPR interpretation signs. Finally, the GPR and TEM tunnel forecast interpretaion signs can be established initially, the main research results are as follows:1. Two-dimensional FDTD numerical simulation of the propagation of electromagnetic waves in the tunnel rock to establish the integrity of surrounding rock and a variety of common typical adverse geological conditions (cave, the rock interface, the combination of cave and rock interface) model, given a particular frequency electromagnetic pulse, select the appropriate parameters and their boundary conditions, calculated time-domain electric field data of a variety of typical adverse geological bodies; based on the MATLAB software to edit script function to get the radar reflection waveforms of typical adverse geological body.2. Through carrying out GPR advanced prediction in Cenxi tunnel, Dongwei tunnel and Lingjiao tunnel, combined with the actual excavation at site,get the different reflection in the GPR figures of the rock changes, cracks contained moisture, broken with caves and other adverse geological bodies.3. Analyzed the actual GPR detect image with the forward modeling results, the waveform, frequency, amplitude and other reflected wave characteristics of post-processing image obtained by the detection data were analyzed and classified, initially established GPR tunnel ahead forecast interpretation signs for the complete rock, fractured dense zone, fracture zone, the water-rich belt, corrosion cracks district, caves (including the empty cave, water-filled cave, cave filled with debris).4. Explore and test the site parameters in TEM tunnel forecasts, spontaneously develop the antenna framework of the TEM instrument and personally participate in Cenxi tunnel, Dongwei tunnel and Lingjiao tunnel forecasting, initially established the interpretation signs of TEM ahead forecast for no adverse geological bodies, caves, faults, karst fissure, cracks and adverse geological Combination.