Development of a Miniature Electrostatic Accelerometer /MESA/ for low g applications Summary report

Design, fabrication, and testing of miniature digital electrostatic accelerometer for low gravity measurements in spac

Predicting the movements of permanently installed electrodes on an active landslide using time-lapse geoelectrical resistivity data only

If electrodes move during geoelectrical resistivity monitoring and their new positions are not incorporated in the inversion, then the resulting tomographic images exhibit artefacts that can obscure genuine time-lapse resistivity changes in the subsurface. The effects of electrode movements on time-lapse resistivity tomography are investigated using a simple analytical model and real data. The correspondence between the model and the data is sufficiently good to be able to predict the effects of electrode movements with reasonable accuracy. For the linear electrode arrays and 2D inversions under consideration, the data are much more sensitive to longitudinal than transverse or vertical movements. Consequently the model can be used to invert the longitudinal offsets of the electrodes from their known baseline positions using only the time-lapse ratios of the apparent resistivity data. The example datasets are taken from a permanently installed electrode array on an active lobe of a landslide. Using two sets with different levels of noise and subsurface resistivity changes, it is found that the electrode positions can be recovered to an accuracy of 4 % of the baseline electrode spacing. This is sufficient to correct the artefacts in the resistivity images, and provides for the possibility of monitoring the movement of the landslide and its internal hydraulic processes simultaneously using electrical resistivity tomography only

Soil Survey of Iowa, Report No. 73—Crawford County Soils

Crawford County is located in western Iowa in the second tier of counties east of the Missouri River and in the middle tier between the north and south state boundaries. It lies entirely in the Missouri loess soil area and the soils of the county are, therefore, chiefly of loessial origin

Soil Survey of Iowa, Report No. 67—Buchanan County Soils

Buchanan County is located in eastern central Iowa in the third tier of counties west of the Mississippi River. It is chiefly in the Iowan drift soil area and hence most of the soils of the county are of drift origin. There is a small area of loess soils, probably derived from the Mississippi loess deposit

Soil Survey of Iowa, Report No. 70—Butler County Soils

Butler County is located in northeastern Iowa in the third tier of counties south of the Minnesota state line and in the fourth tier of counties west of the Mississippi River. It is mainly in the Iowan drift soil area, and hence most of the soils are of drift origin. There is a small acreage of loess soils undoubtedly derived from the Mississippi loess deposit

Soil Survey of Iowa, Report No. 71—Sac County Soils

Sac County is located in the northwestern part of Iowa, in the fourth tier of counties south of the Minnesota state line and in the third tier east of the Missouri River. It is partly in the Wisconsin drift soil area and partly in the Missouri loess area. The soils of the county are partly of glacial and partly of loessial origin

Soil management on the Carrington silt loam

The Carrington silt loam occurs extensively on the gently rolling uplands throughout northeastern central Iowa and in the eastern central counties. It is one of the more important soil types in the Iowan drift soil area. The map (fig. 1) shows its approximate occurrence. Crop yields are generally quite satisfactory on this soil, but some areas are not producing properly, and in many cases much larger yields per acre may be secured by the adoption of better methods of soil management. Suggestions have been offered in a previous publication* which if adopted will make this soil more productive and insure its permanent fertility. These suggestions have been incorporated in what is known as the Iowa system of soil management

Acoustic emission monitoring of a soil slope: comparisons with continuous deformation measurements

Acoustic emission (AE) has become an established approach to monitor the stability of soil slopes. However, the challenge has been to develop strategies to interpret and quantify deformation behaviour from the measured AE. This paper presents the first comparison of continuous AE (measured using an active waveguide) and continuous subsurface deformation measurements. The active waveguide is installed in a borehole through a slope and comprises a metal waveguide rod or tube with a granular backfill surround. When the host slope deforms, the column of granular backfill also deforms, generating AE that can propagate along the waveguide. This paper presents results from a field trial at a reactivated soil slope in North Yorkshire, UK. The measurements confirm that AE rates generated are directly proportional to the velocity of slope movement (e.g. the AE rate versus velocity relationship determined for a series of slope movement events produced an R 2 value of 0·8) and demonstrate the performance of AE monitoring of active waveguides to provide continuous information on slope displacements and displacement rates with high temporal resolution

Soil Survey of Iowa, Report No. 69—Pocahantas County Soils

Pocahontas County is located in the northwestern part of Iowa, in the third tier of counties south of the Minnesota state line and in the fourth tier east of the Missouri River. It lies entirely in the Wisconsin^ drift soil area, and the soils of the county, are, therefore, all of drift origin

Characterising sand and gravel deposits using electrical resistivity tomography (ERT) : case histories from England and Wales

Electrical Resistivity Tomography (ERT) is a rapidly developing geophysical imaging technique that is now widely used to visualise subsurface geological structure, groundwater and lithological variations. It is being increasingly used in environmental and engineering site investigations, but despite its suitability and potential benefits, ERT has yet to be routinely applied by the minerals industry to sand and gravel deposit assessment and quarry planning. The principal advantages of ERT for this application are that it is a cost-effective non-invasive method, which can provide 2D or 3D spatial models of the subsurface throughout the full region of interest. This complements intrusive sampling methods, which typically provide information only at discrete locations. Provided that suitable resistivity contrasts are present, ERT has the potential to reveal mineral and overburden thickness and quality variations within the body of the deposit. Here we present a number of case studies from the UK illustrating the use of 2D and 3D ERT for sand and gravel deposit investigation in a variety of geological settings. We use these case studies to evaluate the performance of ERT, and to illustrate good practice in the application of ERT to deposit investigation. We propose an integrated approach to site investigation and quarry planning incorporating both conventional intrusive methods and ERT