Urban Underground Space Detection
In recent years, the development and utilization of underground space and the safe operation related to underground space have become important issues faced by large and medium-sized cities in China.
At present, domestic urban underground space utilization has reached the depth of 50m,some large projects is about 70m.
In the future, the utilization of urban underground space will be in the direction of integration, deepening, humanity and ecology,therefore,which has higher requirements for the reliability of urban underground space detection.
In addition to drilling, the currently commonly used underground space detection technologies mainly use geophysical methods including ground penetrating radar, shallow seismic prospecting, high-density electrical methods, shallow transient electromagnetic methods, inter-well CT, and fretting.
The traditional geological radar is relatively deficient in the aspects of penetrating target detection and non-metallic target recognition. The effective detection depth of customer's original traditional radar is 5m, which can’t meet this time detection depth requirements . This article takes the “Ultra pulseEKKO” model, a large-depth ground penetrating radar from Sensors & Software as an example, to briefly describe the application of geological radar in urban underground space.
Detection Area Condition
The main Quaternary Lithology in Xi'an city is coarse-grained sediments dominated by sandy gravel and soil-like deposits dominated by loess. The sedimentary thickness increases gradually from southeast to northwest, with an average thickness of 840 meters.
The measurement area is located in Xi'an city, and the detection target is a known subway tunnel section in the urban area, and the tunnel is buried about 10m deep.
Measuring Results
It can be seen from the above figure that the measuring point is located in a parking lot. This time, a 50MHz separate digital antenna is used to detect the underground subway tunnel. It can be seen from the above figure that there is an obvious energy response at a depth of 9m, which is consistent with the actual situation. This plays a very important role in the detection of deep tunnel karst and underground structures.
As can be seen from the above figure that the measuring point is located beside the construction road, with many disturbances and undulating terrain. This time, a 50MHz separate digital antenna is used to detect the underground subway tunnel. From the above figure, it can be seen that there is an obvious energy response at a depth of 9m, which is consistent with the actual situation. This plays a very important role in the detection of deep tunnel karst and underground structures.
Conclusion
From this experiment, it can be seen that ground penetrating radar is very helpful for the detection of urban underground space.The reason why it has been used less before is mainly due to the limitation of detection depth and the limitation of the performance of the radar itself. The Ultra pulseEKKO, a new ground deep penetrating radar launched by Sensors & Software in Canada in 2018, has high transmit power, high stacking times, high signal-to-noise ratio, and environmental noise reduction technology in performance, making the detection range of ground penetrating radar technology in urban underground space is further deepened.
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