Abstract
Abstract Seismic method is a major approach for detecting the seismic geological features ahead of the tunnel, understanding the distribution of unfavorable geology, and ensuring the safety of tunnel construction. Observation system is the key for seismic detection, many studies have been conducted to optimize the observation system; however, most of them focused on the surface seismic investigation and numerical simulation rather than in tunnel field environment (limited aperture and full space environment). How to obtain better wavefield information with limited observation aperture is a great challenge. In this study numerical simulation and instrumental techniques (GPR, DC, etc.) were implemented to further check the result of seismic detection at the 1# tailrace tunnel at the Wudongde hydropower station. In the field case, observation detectors were arranged spatially in the tunnel and source points were placed in four ways: linearly along a single side, on the tunnel face, in front of the detectors, and behind the detectors. Then, after data acquisition, the data processing is conducted to carry out the migration results. The imaging results indicate that the observation system with sources and detectors in liner arrangement (with equal interval) helps to suppress artifacts, further supporting the advantages of spatial observation system with liner observation line (detectors). Moreover, the study provides suggestions for geological prospecting in similar tunnel projects.
Highlights
The rapid and sustained economic development has increased the requirements for road traffic engineering, water conservation, and hydropower projects
In other words, based on an actual tunnel environment, this study evaluates the observed data and imaging characteristics using different observation system, and estimates the geological conditions ahead of the tunnel face, helping for better understanding the geological conditions
The observation system D helps to get the clear imaging result, which is consistent with the major geological structures
Summary
The rapid and sustained economic development has increased the requirements for road traffic engineering, water conservation, and hydropower projects. This development leads the trend that the country builds more and more constructions in the underground environment [1]. Taking China as an example, in the field of transportation, 16,331 km railway tunnels are in operation, and 7,465 km tunnels are under construction, as well as 15,634 km tunnels are under design or planning by the end of 2018 [2]. In the field of water conservation and hydropower, more than 40 key hydropower projects are planned or under construction as well as dozens of long-distance water transfer projects [3]. Geological disasters such as water inrush and collapses occur during tunnel construction without accurate information of adverse geology in advance [5,6,7]
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