Abstract
Most of the existing electrical-resistivity-based ahead prospecting methods in tunnel use only the tunnel cavity and tunnel face space to locate the water-bearing structures in front of the tunnel. However, due to the limitation of the narrow available space for arranging electrodes in tunnel, this kind of method is difficult to achieve more accurate image for water-bearing structures. The cross-hole electrical resistivity tomography (CHERT) and borehole-to-surface electrical resistivity tomography (BSERT) methods using borehole space have been proved effective means to achieve better images of deep anomalies on the surface. In this paper, the tunnel-face and borehole ERI (TBERI) method in tunnels was studied. To less affect the construction progress, the pole-pole configuration using a single borehole was studied in this paper. Moreover, the configuration is optimized based on the block weighted CR optimization strategy. After considering the data combination, an effective measurement configuration suitable for TBERI detection was formed. To accelerate calculation, some redundant data are removed from the obtained data after proposed block weighted optimization is conducted. By adopting the proposed configuration, the abnormal objects in the target area in the inversion are more accurate. The effectiveness of proposed configuration is verified by numerical simulation.
Highlights
In the past two decades, tunnel engineering has developed rapidly in the worldwide
For ahead prospecting methods conducting in tunnel environments, the space of ahead drilling borehole can be used for borehole electrical resistivity (BER) detection
This optimization strategy can optimize the observation device based on the sensitivity matrix, which can reduce the number of electrodes and basically ensuring the overall quality of the data set, greatly reduce the amount of data
Summary
In the past two decades, tunnel engineering has developed rapidly in the worldwide. Especially in Southwest China, a large number of roads, railways, and water diversion projects need to rely on tunnels to cross the complex terrains. The balance between detection resolution and the intensity of symmetric artifacts is a key issue in the selection of configurations They optimized the data of the two configurations for joint inversion and used the weighted MOST method to improve the inversion results, effectively solving the problem of symmetric artifacts. In order to solve similar problems in surface ERT, Wilkinson et al proposed the Compare-R (CR) configuration optimization method based on the model resolution matrix of the data set in the surface ERT detection [14] This optimization strategy can optimize the observation device based on the sensitivity matrix, which can reduce the number of electrodes and basically ensuring the overall quality of the data set, greatly reduce the amount of data. The effectiveness of the proposed method is verified by the inversion simulation results of the two anomalies
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