The induced polarization receiver capable of detecting the intermodulation coupling products caused by the electrically nonlinear ground employing adaptive filters is designed and constructed. The sum of two sine waves is transmitted to the ground. The first adaptive notch filter rejects the received signal at the transmitted frequencies. The second adaptive notch filter is used as a spectrum analyzer to measure the Fourier coefficients at eight discrete intermodulation frequencies. The receiver was tested for its ability to recognized the intermodulation products and calibrated. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

No description available.

The application of spectral induced polarization (SIP) to geohydrologic and geotechnical problems is considered. Some fundamental electrochemical characteristics of sulfides are reviewed. An alternate theory of the underlying cause of IP is presented. A modified field method is proposed. Two field sites are studied. Prevailing electrochemical thought is that most sulfides, especially pyrite and chalcopyrite, have passivating surface coatings. With this thought in mind, existing geophysically-oriented electrochemical measurements may be reinterpreted quite differently than has previously been done. Large impedances at low frequencies have traditionally been attributed by geophysicists to diffusional phenomena related to rapid reactions occurring at the sulfide surface. Large impedances at low frequencies with clays have traditionally been attributed to restrained ionic diffusion between zones of clay particles. Although they appear to be due to quite different mechanisms, both of these low frequency dispersions may be explained by a single rate limiting mechanism. Using fractal geometry, the large low frequency dispersions observed on sulfides may be explained by distributed high charge-transfer resistances on rough surfaces. With high surface resistances sulfides may behave like insulating clay particles and allow charge separation to occur in surface conduction current flow. Although displacement currents may flow in sulfides they are considered to be minimal in comparison to the surface conduction currents. The concept of a common polarization phenomenon allows the previous studies on rock samples containing clay particles and/or sulfides to be equated on the basis of particle size. With clay-coated sand grains it may be possible to estimate intrinsic hydraulic conductivity based on the interpreted polarizable grain size. Aquifers, and partially water saturated zones, may be IP targets if they have small amounts of polarizable clay minerals. Aquifer detection and grain size estimation are demonstrated. Theoretical work and field studies show the advantages of using a modified dipole-dipole array and data presentation methods. The large amounts of data gathered during broad-band SIP surveys are demonstrated to be very useful in layered-earth geohydrologic problems. The higher frequency data contain much earth-structure information, are easily gathered, and allow immediate qualitative structural interpretation. Lower frequency data contain information useful in aquifer characterization.

No description available.

As of September 2007, there were over 67,000 U.S. bridges in the National Bridge Inventory classified as having unknown foundations. The bridges spanning rivers are of critical importance due to the risks of potential scour. In fact, over half of all bridge collapses are due to scour. Not only are these failures costly, they can be deadly for the traveling public. On April 5, 1987, ten people were killed in New York when a pier collapsed on the Schoharie Creek Bridge causing two spans of the deck to fall into the creek. Several other fatal collapses have occurred since the Schoharie Creek Bridge failure. Detecting scour is only part of the assessment that must take place to determine risk of failure and knowing the foundation depth is a critical component of the assessment. While this issue is not new, current techniques are typically invasive or costly. This research explores the feasibility and effectiveness of induced polarization (IP) and electrical resistivity imaging (ERI), near surface geophysical methods, for determining the depth of unknown foundations. In this work, forward models are created to ascertain the effects of the bridge layout on data quality such as varying depths and the impact of adjacent foundations on the foundation in question. Next, an experimental study is conducted at a National Geotechnical Experimentation Site (NGES) to further identify key parameters for the testing design and setup in order to obtain optimal surveys of bridge foundations. The conclusions of the forward modeling and NGES investigations are used to plan the field surveys on four bridges with known foundations. The outcomes of the four bridges show that IP and ERI can be used in concert with one another to estimate the type and depth of bridge foundations. The results of the field surveys are used to create a probability of non-exceedance curve for future predictions of unknown bridge foundations using the methods described in this research.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Vita. / Bibliography: leaves 133-136. / by Frank Dale Oliver Morgan. / Ph.D.

<p>Determination of the subsurface geology is very important for the rock quarry industry. This is primarily done by drilling and mapping of the surface geology. However in Sweden the bedrock is often completely covered by Quaternary sediments making the prediction of subsurface geology quite difficult. Incorrect prediction of the rock-mass quality can lead to economic problems for the quarry. By performing geophysical measurements a more complete understanding of the subsurface geology can be determined. This study shows that by doing 2D-parallel data sampling a 3D inversion of the dataset is possible, which greatly enhances the visualization of the subsurface. Furthermore the electrical resistivity technique together with the induced polarization method proved to be very efficient in detecting fracture frequency, identification of major fracture zones, and variations in rock-mass quality all of which can affect the aggregate quality. With this technique not only the rock-mass quality is determined but also the thickness of the overburden. Implementation of geophysics can be a valuable tool for the quarry industry, resulting in substantial economic benefits.  </p>

Determination of the subsurface geology is very important for the rock quarry industry. This is primarily done by drilling and mapping of the surface geology. However in Sweden the bedrock is often completely covered by Quaternary sediments making the prediction of subsurface geology quite difficult. Incorrect prediction of the rock-mass quality can lead to economic problems for the quarry. By performing geophysical measurements a more complete understanding of the subsurface geology can be determined. This study shows that by doing 2D-parallel data sampling a 3D inversion of the dataset is possible, which greatly enhances the visualization of the subsurface. Furthermore the electrical resistivity technique together with the induced polarization method proved to be very efficient in detecting fracture frequency, identification of major fracture zones, and variations in rock-mass quality all of which can affect the aggregate quality. With this technique not only the rock-mass quality is determined but also the thickness of the overburden. Implementation of geophysics can be a valuable tool for the quarry industry, resulting in substantial economic benefits. / QC 20101118

The object of the thesis is to obtain the apparent- resistivity curves and induced-polarization (IP) effects that are utilized in geophysical exploration. Two different earth geometries, the thin horizontal conductive layer and vertical dike, were studied. The solution for both cases is identical. First, quasi- static electrical conditions were assumed, so that the problem could be solved using potential fields. The exact solution to the problem was obtained by using the Bessel integral formulation. Also, the image method was employed to find the potential fields. We noticed that the image -type series converges best when the dike or layer was thick (ratio of thickness to electrode spacing, b/a, is large) and the reflection coefficient was not near ±1. Otherwise, it is preferable to employ the thin conductive sheet model. The next step was to determine the dilution and distortion factors which are relevant to the induced polarization response. Finally, numerical results were obtained using a Fortran computer program. These calculations were compared with some results taken from the literature and good agreement is seen.