Abstract
This study investigated the application of the borehole laser scanning technology (BLST) method in the detection of both dry and water-filled karst caves. In order to solve the problem of excessive laser attenuation during the detection, we designed a test for the characteristics of multiwavelength laser attenuation in water-filled karst caves and studied the influence exerted by various factors, including different wavelengths, different laser power levels, different suspended media, and effect of turbidity on the attenuation coefficient. During the test, we discovered the existence of a “blue-green window” with low turbidity and a “near infrared window” with high turbidity in karst cave water environments. Based on the general survey results of drilling and comprehensive geophysical prospecting, a quantitative method using targeted drilling was proposed to detect the spatial morphology of karst caves in complex environments. We also investigated the effects of complex environmental factors such as suspended media and high turbidity on the laser detection distance and accuracy in karst caves, and established a quantitative matching model of laser wavelengths, laser power, and complex environmental parameters. Based on this, we obtained the best acquisition mode for detecting lasers in different karst development environments. A high-precision, three-dimensional visualized model of a real karst cave was established to quantitatively obtain the characteristic parameters, such as accurate position, three-dimensional shape, space volume, and cave filling type, which was applied to the detection of karst caves along the Jinan subway line.
Highlights
As cities develop and urban populations increase rapidly, traffic congestion has become one of the greatest problems facing many cities in China
The VLP-2000 laser power meter was selected in this test to measure the initial laser emission power and the power attenuated through the water simulator
When the laser path remained constant, we filled the transparent box with water, and used the laser power meter to measure the light intensity at the initial stage and after attenuation, which were recorded as I10 and I20, respectively
Summary
As cities develop and urban populations increase rapidly, traffic congestion has become one of the greatest problems facing many cities in China. Drilling and comprehensive geophysical exploration methods cannot accurately detect karst cave boundaries in complex geological environments, rather can only deliver two-dimensional or even one-dimensional qualitative data with poor visualization effects and cannot provide quantitative parameters of karst caves, such as the accurate position and size information. The biggest advantage of this method is that the microlaser probe can adapt to various kinds of narrow channels and boreholes and can be inserted deeply into a cave to obtain the point cloud coordinate data This method has been widely employed in many professional instruments for the exploration of poor geological structures, such as the Cavity. The cavity laser scanning method the following advantages: the ability to realize the quantitative and precise detection of cavehas position, size, filling state, and(1).
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