Application example of large depth ground penetrating radar ultra PE in road collapse detection in Shanghai
01 detection of road collapse in Shanghai
Ground penetrating radar is a method to judge the shape of underground objects by measuring the time and energy intensity of electromagnetic wave reflected by using the time domain characteristics of electromagnetic wave. However, because the electromagnetic wave is easily absorbed by the water and salt bearing low resistivity stratum, the detection effect of traditional radar in coastal cities (especially the shallow surface of river inlets such as Tianjin, Shanghai, Fuzhou, Xiamen and Shenzhen is often covered by thick silt layer) is not good, and its effective detection depth is generally 2-3m.
On Thursday, our company was invited to conduct large-depth radar detection of pavement collapse in some sections of fasai road and Daduhe road in Shanghai. Obvious signs of collapse can be seen on the site pavement, which is a known collapsed section.
02 field measurement results of fasailu
Construction site
Survey line layout: five survey lines with a spacing of 50cm are arranged in two adjacent lanes.
One section uses ultra PE 100MHz antenna profile gray map
Three dimensional vertical slices 1m apart
Site collapse of fasai Road (it can be seen that there is obvious land subsidence in the middle)
From the above vertical slice diagrams, we can clearly see that there are many abnormal masses with large energy amplitude between 4 ~ 6m underground. The main reason for the abnormal change of amplitude is the rapid change of dielectric constant. 0~8m, 30~34m and 38~40m are collapse areas with strong water content
03 survey results of Daduhe Road
Five survey lines were completed along the one-way lane
One section uses ultra PE 100MHz antenna profile gray map
Three dimensional vertical slices 1.5m apart
From the above drawings, it can be seen that there is an obvious amplitude extreme value area at the depth of 4m between 23 ~ 26m, and its side near the roadside is abnormally expanded. It is speculated that it is caused by leakage of underground metal water pipes and deposition on both sides.
04 conclusion
The ultra PE 100MHz digital antenna of the new large depth ground penetrating radar is in Shanghai. The acquisition parameters are point distance of 0.25m, stacking times of 8192 times and continuous measurement. Its effective detection depth is about 9m. It can be seen that the new radar greatly improves the detection depth and also takes into account the acquisition speed.
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