In order to do the health check for the strata, Professor Chau-Huei Chen, from the Department of Earth and Environmental Sciences at Chung Cheng University (CCU), develops a \"Three-dimensional Geodetic Tomography System\", which can be used to investigate the underground structures in large public constructions such as reservoirs and nuclear power plants or in transportation infrastructure such as railways, tunnels, and bridges. It is the first time that the system applied on geodetic inspection in Taiwan. Compared with the traditional one-dimensional and two-dimensional drilling methods, seismic prospecting, Electrical Resistivity Tomography (ERT) and other survey methods that will often damage the crustal structures, the system developed by Professor Chen uses three-dimensional ambient noise as the measuring signal, just like a geodetic doctor, to proceed a computer tomographic screening for the land providing a clear view of the crustal layers, without causing any damages on environmental conditions of the ground surface and underground structure.
\"The surfaces of underground strata are not always flat, some parts are bumped up, some caved in, and the geological composition of these strata are also quite different. The more we understand the underground conditions clearly, the more possibilities that the constructions built on top the ground surface can meet the environmental demands due to the underground conditions for the safety requirements.\" Professor Chen said that the geological survey is the necessary step before all construction works start. In particular, those large-scale public projects which regard the safety issue as the priority, such as bridges, tunnels, railway and highway constructions, etc., a detailed site investigation on the types and the structures of rock formations will be a must-done procedure. The investigation will assess the feasibility for the construction and help make sure the safety issues associated with the foundations design of the buildings are fully considered and secured.
\"As the scale of construction projects become larger and larger, therefore more drillings will be on its way to help conduct geologic investigation and analysis, so the higher cost and the longer time will be needed for underground tectonic surveys.\" Professor Chen then explained that at present, according to the regulation, engineering inspections for domestic construction sites must use drilling as the main method to do the job, then possibly along with the use of seismic method, electrical method or ground penetrating radar (GPR) as an assistive measure, if necessary. Drilling method normally makes holes from the ground surface downward into the crustal layers by the drilling devices. Although the information of underground geological structure can be directly obtained by this method, just like seismic method heavily hammering the ground, it can also cause geological damages. In addition, the common disadvantage of these methods is that its application does not meet all the requirements needed in the inspection process. For example, the GPR can only deal with the tasks in a range as far as to one meter down in depth; when conducting the investigation in seismic method and electrical method, the geodetic conditions such as forests, rivers and other uneven surfaces would make them difficult to proceed.
\"When the sea waves hit the coast or the wind blows on the woods, it causes ground motions.\" The CCU team with a professional background in seismology uses the ambient noise generated from earthquake motions that used to be considered as interference, to developed a \"three-dimensional geodetic tomography system.\" Professor Chen claimed that with these micro-motions captured by the system on the site and the seismic wave velocity being analyzed through the computer program, without damaging the environment, the types and structural conditions of the rock formations, whether are they the faults, soil liquefaction or the broken rock layers, all can be screened out by this system. Because this system applies AI and big data process, a lot of resources of manpower and material in use can be saved, further, it provides better accuracy to a more comprehensive scale compared with other methods. It is indeed a revolutionary new technology of exploration engineering.
The geodetic tomography system developed by the CCU team can be applied to the prevention and control of natural disasters, in addition to the safety assessment, inspection and maintenance for the sites of construction projects. Professor Chen also claimed that the risks of hillsides development, debris flows, or any other relevant issues against people\'s safety, as well can use this system to pre-determine the underground conditions to help the government execute disaster prevention. At the moment, Chen has been in the process to negotiate a cooperation deal with some relevant manufacturers. He is looking forwards to making the infrastructure construction site inspection technology a more accurate and safer practice at home and abroad.