Types Of Geological Features Research Articles

Probabilistic Time Estimation of Tunneling Projects: The Uri Headrace Tunnel

Probabilistic time estimation is an essential part of proper risk management in tunneling projects. In recent decades, several models have been developed for this purpose, one of which was developed by Isaksson and Stille (Rock Mech Rock Eng 38:373–398, 2005). In this paper, Isaksson and Stille’s probabilistic time and cost estimation model was improved and then applied to estimate the total tunneling time of the headrace tunnel in the Uri hydropower project in India. The improvements allow the user to more accurately account for different types of geological features and disruptive events. The result of the estimation is a distribution of tunneling time. The outcome illustrates how a proper understanding of the geological setting of the project and its effect on construction performance can contribute to effective risk management.

Classification and Localization of Naval Mines With Superellipse Active Contours

In this paper, an approach for the classification and localization of geometric shapes, e.g., man-made objects or different types of geological features, in sonar images is presented. It is applied to a concrete application case, namely the detection and classification of naval mines. The approach consists of three steps. In the first step, the sonar image is segmented by a new active contours algorithm. To deal with the significant noise on sonar images, the assumption is used that the segmenting contours of highlight and shadow areas of objects are geometric shapes that can be described by superellipses. It is shown here that this superellipse constraint, which can cover a wide range from box-shaped to round objects, can directly be incorporated into an active contours method without an additional edge framework. In addition to its robustness to noise, our superellipse-driven active contours approach has the advantage that it is adaptable to the intensity distribution properties of sonar images. The second step consists of the actual classification including a pose estimation using a standard naive Bayes classifier on the superellipse parameters that are computed by the segmentation in the first step. Robustness is further boosted in a novel third step in which the classification is verified in a top-down process. Based on the results of the bottom-up processes, i.e., the segmentation in step one and the pose estimation from the superellipse parameters plus the class estimation by the classifier in step two, it is possible to simulate what the input sonar image should look like if the results are correct. If this model-based top-down simulation is similar to the original sensor image, the classification result is accepted; otherwise it is rejected. To this end, different measures are compared to compute the similarity between the real sensor image and the anticipated image generated from the classification and localization hypothesis. Finally, our approach is evaluated with a challenging real-world data set of 213 synthetic aperture sonar sidescan images from sea trials with mock-up mines.

Speciation of dissolved chromium and the mechanisms controlling its concentration in natural water

The circulation of chromium at naturally occurring concentration levels (i.e., 1μgdm−3 or lower) was examined using solid-phase spectrophotometry and inductively coupled plasma-mass spectrophotometry (ICP-MS) to determine the Cr(VI) and Cr(Total) concentrations, respectively. Natural water and stream sediments were collected from areas with various types of geologic features, such as metamorphic rocks, volcanic rocks and limestone in Japan and Indonesia. Cr(VI) was predominant in weakly alkaline natural waters, and the Cr(III) concentration was less than 1μgdm−3, which was considerably lower than that expected based on the solubility of Cr(OH)3. The dissolution of chromium in natural water was described by the leaching of Cr(VI) from Cr(III)-containing minerals under oxic conditions. The Cr(VI) concentration in a solution that was in contact with chromite, FeCr2O4, linearly increased with the reaction time. The results indicated that under oxic conditions at PO2=0.21atm, the leaching rate of Cr(VI) was pseudo zero-order at a fixed pH and was higher in alkaline than in acidic solutions. The removal of Cr from natural waters was due to the reduction of Cr(VI) to Cr(III) by organic matter, such as humic substances, as well as to the adsorption of Cr(III) onto suspended matter and river sediments. The reduction of Cr(VI) to Cr(III) followed the equation −d[Cr(VI)]/dt=[H+]a[Cr(VI)][DOC] with a=0 at pH<4 and a=−1 at pH>4.5. The removal of Cr(III) by river sediments and/or suspended particulate matter was rapid and the adsorbability of Cr(III) was dependent on pH, which suggests that the active species were Cr(OH)2+ and Cr(OH)3. Schematic models of the circulation of dissolved chromium in natural water were proposed under acidic and alkaline conditions.

Fluid-potential patterns and hydrocarbon deposits in groundwater flow-fields induced by gravity and tectonic compression, Hungarian Great Plain, Pannonian Basin

In the course of a petroleum hydrogeological research project in the Pannonian sedimentary basin, spatial coincidence has been observed between dozens of known hydrocarbon pools and mapped fluid-potential anomalies based on more than 16,000 pore-pressure measurements over an area of approx. 40,000 km 2. The anomalies were identified on vertical pressure profiles at 8 sites, 4 hydraulic cross sections totalling 850 km in length, and a stack of 13 tomographic fluid-potential maps reaching to depths of over 3 km. The perturbations have been attributed to hydraulic windows formed by conducting faults and sedimentological discontinuities in a subsurface flow domain comprising a lower, tectonically driven, overpressured regime and an upper, gravity-drive zone. Because these types of geologic features can also be pathways and traps for hydrocarbons, their attendant potentiometric disturbances may be indicative of the presence of petroleum accumulations.

Perception of a geological body using multiple source remotely-sensed data-relative influence of the spectral content and the spatial resolution

Abstract Fracturing maps over a granitic dome (Scaër granite, Brittany, France) have been extracted from the most widely available remotely-sensed data and from aerial photographs. Comparison of the different maps obtained allowed the classification of the mapping potential of the different raw and merged images as well as ranking their ability to point out geological features at different scales. Three different types of geological features were pinpointed: a coarse regional fracturing, kilometric plutonic domes and finer geological structures such as circular features within the granitic dome. The best means of revealing each of these three types of geological features, proved to be radar images, multi-spectral data and aerial photographs, respectively. The data providing the largest range of observation and the greatest amount of information on geological structures and soil types were the merged Landsat-TM and SPOT panchromatic images.

Geologic and seismic velocity structure of the crust/mantle transition in the Bay of Islands Ophiolite Complex

Geological investigations of the Bay of Islands Ophiolite Complex show that while a typical layered ophiolite suite is present, the thickness of major lithologic units is extremely variable from place to place. The composition and internal structure of map‐scale (kilometers across) lithologic units as well as the contacts that bound them are laterally variable. Inferred velocity‐depth functions of the crust/mantle (“Moho”) transition reconstructed for this terrane as oceanic lithosphere suggest an extremely complex internal seismic structure. The crust/mantle transition from mafic to ultramafic lithologies varies across the ophiolite from a sharp geologic and seismic velocity discontinuity to a complexly interlayered transition zone as much as 3 km thick. The mafic/ultramafic transition is characterized by laterally discontinuous lithologic units on the order of hundreds of meters to a few kilometers thick and up to several kilometers long. These units (megalenses) may be composed of lithologies with higher or lower seismic velocities than those of the surrounding units. Solid‐state deformation has produced seismically anisotropic materials in the upper mantle and lower crustal units. Substantial relief and slopes of up to at least 12° over lateral distances of about 10 km occur on the top of the crust/mantle transition zone as well as other geologic unit contacts. Although these types of geological features are striking to the field geologist working in ophiolites and are significant to the understanding of crustal accretion processes, many of them occur on such a small scale that they might go undetected in different types of seismic experiments in contemporary oceanic lithosphere.