Underground Man-made Vacancy Detection From Gravity Gradiometry

Underground man-made vacancy(command posts, bomb shelter, strategic facilities, warstorage and so on) has an advantage on disguise and, which attracts many countries in the world,and some nations have committed themselves to building stable underground man-made vacancyto protect military facilities. Consequently, it’s important to study the technique for detecting theunderground targets.Gravity measurement technology in use for geophysics applications today could beadvanced and integrated into an effective system for locating deeply buried facilities, bymeasuring the tiny change of gravity field. In security area, the advantage of gradiometrytechniques in arms treaty-limited, nuclear investigation, swallow targets detection have beenrealized by experts, and some researchers begin to pay attention to this new technique.Aiming at the problem of underground man-made vacancy detection, the fundamentaltheories and key technical difficulties are mainly studied in this dissertation. The advantage ofgravity gradiometry for detecting swallow targets and investigation ability are analyzed; thedetecting capability of gravity and gradiometry have been concluded with the measurementprecision and environments, experiments have been carried out to estimate the target interestedwith Euler deconvolution method. Then, some suggestions are made for the construction ofunderground facilities to promote the safety. The main work and innovative ideas are listened asfollow:1. The function of gravity measurement in national economy, technology, and security hasbeen recommended. Its application and development have been summed up. The application anddevelopment of gravity gradiometry have been analyzed, research on gravity gradiometrymeasurement in detecting underground targets in western countries has been studied.2. The detecting abilities of gravimetry and gradiometry are compared, which includes:(1) The mathematical and physical meaning of gravity and gradients anomaly are analyzed;(2) Forward calculation of gravity anomaly caused by simple and regular models arestudied;(3) The effects of residual density, mass, depth in gravity and gradient measurements areanalyzed(4) A primary experiment has been carried out with the CG-5gravimeter to identify thedetecting capability of vertical gravity gradient;(5) The detecting abilities of gravimetry and gradiometry are compared. The result shows that gradiometry has a marked advantage over gravimetry on identifying swallow target,discrimination target interested from others, and constraint the naturally-occurring features, suchas topography and geology;3. According to the purpose of underground man-made facilities, three different safeguardshas been simulated, and the design index of safety has been calculated with the forwardcalculation formula: the safety design of command posts, bomb shelters, and tunnels on depthare60m,90m, and40m.4. The research of Euler deconvolution method detecting underground targets includes:(1) The theory and computing process of Euler deconvolution method have beensummarized, and its advantage and disadvantage have been concluded;(2) The computing process of Euler deconvolution method has been modified, whichimproved the excessive solutions and convergence;(3) Every factor affects the Euler solution has been analyzed, and the experiment of Eulerdeconvolution has been designed;(4) With the influence of target feature, measurement style and error, the estimation effectsare analyzed. The result shows that modified Euler deconvolution method is a good inversemethod, which can accurately estimate the position of potential source.From the research, some conclusions can be attained:(1) With high accurate gravityequipment, detecting underground man-made vacancy from small gravity (gradients) anomaly isviable;(2) The advantage of gravity gradiometry relies in: multi-gradient information can reflectthe underground targets more clearly;(3) The union of gravity and gradient data can improve theestimating effects of potential source, which means the gradient data includes more highfrequency information;(4) With parameter and measurement data properly set, Eulerdeconvolution method can estimate the targets more accurately;(5) Gravity gradiometry candetect the underground targets, while the fast and precise search on underground vacancy has todepend on the union of multiple detecting methods.