The Analysis Method of Time Reversal for Defect Diagnosis of Concealed Structure

In this paper, a new method of time reversal for defect diagnosis of concealed structure has been proposed based on the detecting technique of structure acoustic wave and the theory of time reversal. The time reversal recurrence formula for detecting the acoustic wave speed constitution of concealed structures with bilevel asynchronous test has been established. The wave speed constitution can be reconstructed in 2 D graticule form by means of this method. The result of model test shows the method is valid.

Identification of the Concealed Structures in the Beiya Area of Western Yunnan

The interpretation of regional gravity and magnetic data, especially the extracted information about concealed targets and structures, provide important evidence for geological structure research, oil-gas resource assessment, mineral potential forecast and prospective area delineation. Several interpretation methods have been proposed to determine structural boundary, including vertical derivative, horizontal first-order derivative, total horizontal derivative, total gradient modulus, tilt derivative, and theta graph, and each have their advantages and disadvantages. This study used the tilt derivate method to obtain bouguer gravity anomalies in the Beya area, as shown in Fig. 1a.

Application of the High-resolution EM Method in the Investigation of B Tunnel

A successful case history of exploring for concealed structure using the high-resolution EM method in the investigation of the West-East Gas Pipeline Project＇s B Tunnel is presented in this paper. The high frequency electromagnetic image system named STRATAGEM EH4, operating at frequencies ranging from 90KHz to 1Hz, was used for data acquisition. The orthogonal components of the electromagnetic field were measured during the field acquisition and the relevant electromagnetic attributes of the object body were extracted from the electromagnetic data. Hybrid sources, consisting of natural and full tensor-controlled sources, were utilized to produce high-quality electromagnetic field data. B Tunnel lies in the western part of Hubei province, at depths of less than 200m. The geologic setting of B tunnel is very complex. Following an initial geologic investigation, an outcrop considered to be a bedrock interface by investigators, collapsed during tunneling operations. A second investigation applied high-resolution EM and seismic refraction methods to reveal a more complex geologic structure along the tunnel route. The predicted rock classes and fault were encountered during the subsequent tunneling operations.

APPLICATIONS OF SURFACE SPLINE FUNCTIONS TO STRUCTURAL ANALYSIS IN COAL GEOLOGY

A surface spline function is used to fit a coal seam surface in structural anal ysis in coal geology. From the surface spline function, the first and second partial derivatives can also be derived and used to structural analysis, especially for recogni tion of the concealed structures. The detection of structures related to faulting is em phasized.

Deep Duplex Thrust in the Sangzhi-Shimen Tectonic Belt,in the West Hunan and Hubei Areas

Recent studies indicate that there is a large buried body developing in the Sangzhi-Shimen tectonic belt,which is between the Xuefeng intracontinental deformation system and the Xiangexi tectonic belt.In order to explore the tectonic evolution and main deformation-controlling factors of the buried body,we carried out a series of studies and built two new models based on the latest seismic data and fault-related fold theory.These new models show that the deformation of the buried body in the north segment of the study area is different from that in the middle-south segment.After further study,we found the main factors leading to these differences were:(1)the magnitude of the principal stress,(2)the range of tectonic movements,and(3)the morphology and depth of the basement detachment.Subsequently,with the physical simulation experiments,a 3D evolution model of the study area was built.