Buried structure inquiry

As a method of buried structure inquiry, there are underground inquiry radar, TESLAFINDER (three dimensions of magnetic exploration), pin-point locator (instruction electromagnetic method), Rayleigh wave methods, and, by an inquiry target and depth, there is a difference in the inquiry method. We will try to introduce an inquiry method by depth in this section.

An inquiry of depth from 0m to 4.5m
(there is a difference by geological features)

In a general road, gas-pipe, sewer, waterworks, electricity, NTT are laid underground by around 4m deep. In addition, sewer main, trunk line are laid underground by deeper position. On the other hand underground multi-purpose duct and the subway which increased of late years are laid underground by deep position. We show a buried object inquiry method of a comparatively shallow position by an illustration of lower part.

An inquiry result
An inquiry result of a radar and pin-point locator outputs horizontal position. As for the radar, a cavity and looseness and underground water, the other buried object (a trace of solidification materials injection, underdrain, Piling-stones) are possible.

Underground inquiry radar
Underground inquiry radar reflects an electric wave sent from an antenna at each part (soil, a stone, a pipe, cavity, subsoil water) in the ground, and it is machinery investigating buried object, visualizing arrival time and strength of a reflection electric wave.

Pin-point locator (PP)
PP receives a message of electrical signal of the buried object which electrical signal sends it to (an electric wire, phone line, signal line) and investigates it. In case of buried object which does not send electrical signal to (gas-pipe, a water service pipe, a sewage pipe), we put on a receiver on a part cropping out on ground (divergence valve, meter lines) to investigate it. Perhaps we insert a pipe interior dispatch radio sonde and we raise accuracy furthermore and can investigate it. Data of PP do not output it with paper. It is a method to record an analog meter and carrier tone of the main body in field book at the actual place.

The figure of the right side did printout of a result of radar inquiry. Horizontal scale is distance, and vertical scale is depth.

An inquiry of depth from 0m to 40m
(there is a difference according to geological features)

A method to investigate the deep buried object and underground situation is the method how an inquiry by vibration is general. There are several kinds inquiry methods according to kinds of vibration. The method that we enforce is an inquiry method called Rayleigh wave method.

What is Rayleigh wave probe?
Rayleigh wave is the vibration wave which is similar to P wave, which is wave of condensation and rarefaction (P wave) and a shear wave (S wave) and the same kind. We show an example of inquiry by upper diagram. we generate vibration with a vibrator, and we change the vibration frequency successively, (when the number of vibration changes, arrival depth of Rayleigh wave changes.) and it is a method to investigate the quality of soil situation by a difference of vibration propagation time to receiver A and B. A method to investigate from a difference of Rayleigh wave propagation velocity of peripheral materials and buried objects is a basic principle.