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The Giesa FL2 Frame and blade component of the Automated Vane Shear (AVS) equipment.


Introduction

The AVS test is used for in situ determination of the undrained strength of intact, fully saturated clays (undrained strengths < 100 kN/m2); the test is not suitable for other types of soil or if the clay contains sand or silt laminations.

A four-bladed vane is inserted into the split core and rotated at a constant rate to determine the torque required to cause a cylindrical surface (with a diameter equal to the overall width of the vane) to be sheared by the vane. This destructive measurement is done in the working half, with the rotation axis parallel to the bedding plane. The torque required to shear the sediment along the vertical and horizontal edges of the vane is a relatively direct measure of the shear strength. Typical sampling rates are one per core section until the sediment becomes too firm for insertion of the vane.

The rate of rotation of the vane should be within the range of 6°–12°/min.

The GeoLab software that controls the AVS calculates shear stress as:

Stress (kN/m2) = torque (Nm) × Vane constant (1/m3) × 1/1000


Procedures

  • Preparing the Instrument

     1. Click on the GeoLab Icon on the Desktop to start the GeoLAB application (Figure 1).




Figure 1. GeoLab Icon.

     2. Start a new project for each site: Project > new > project > Expedition_SiteHole (Figure 2).

     3. Start a new test in the project folder: Project > new > test > CoreTypeSection_Offset or TextID_Offset.

     4. Keep the subdirectory highlighted, and click on EXCEL from within the application (Figure 2).


Figure 2. New Project.


     5. Select the Excel template (e.g., AVS_master_XXXX.xls) (Figure 3). The PP technician will select and save a master file for each particular expedition.

Figure 3. Excel Templates.


     6. Check the rotation speed (1–1.5) and vane type (A, drop-down list) (Figure 4).

Figure 4. Rotation Speed and Vane Type.


  • Making a Measurement

     1. Insert the vane into the sediment, by turning the black handle clockwise, until the top of the wings are even with the sediment surface. Avoid obviously disturbed areas (cracks, gaps, bioturbation, etc.) and note that the test is not suitable for sand or gravel-sized material or for clay that contains sand or silt laminations.
IMPORTANT! If the brass fitting (Figure 5) pushes out of the support beam below the hand crank, the sediment is too hard for this test. Do not attempt to force the vane into the sediment as you may damage the instrument!

Figure 5. Brass fitting


     2. Open the Excel spreadsheet from within GeoLAB by clicking on the Excel icon (Figure 2).

     3. Use the barcode gun to scan the section information into the yellow cell below the graph. Be sure to cut everything past the textID (e.g., TEST-U341PA…) and paste into an adjacent cell (Figure 7).

Figure 6. Monitor Acquisition.                                           


     4. Measure and enter the offset from top of section (blue cap) into the top interval field (light blue box), then click Enter.


Figure 7. Paste Barcode TEXT_ID (make sure to segregate the TEXT_ID and Label_ID so it will upload properly).


     5. Modify this information for each core measured.

     6. With GeoLAB already open, Click on init; set sample-time to 1 or 2 readings/sec (i.e., sampling rate); and click the traffic light icon to start the measurement (Figure 8a). Monitor the test curve on the Excel screen (Figure 6). When the maximum shear strength of the sediment (highest point of the curve) has been reached, stop the test by clicking the STOP sign icon in the GeoLAB application (Figure 8b).

          Figure 8a. Set Acquisition Parameters.               Figure 8b (click stop sign after the measurement).


     7. Save the Excel template with its data as a .CSV (comma delimited) file using Save As…: Path = C:\data\gantry\in; Filename = LabelID_offset_AVS.csv.

     8. Close the EXCEL application, without saving it again, (LIMS will not upload the file if it is in use).

Upload Data to LIMS

     1. Launch MegaUploadaTron (MUT, Applications Folder: IODP) if it is not already running.

     2. Check to see if the AVS file(s) are present on the screen. If not, select the proper Upload Directory in the MUT application under File.

     3. Click on the directory of choice (e.g., C:/gantry/IN) and check the MUT dialog window. The files to be uploaded should be present in this window.

     4. Select the files to be uploaded, or use the Select All checkbox in the lower left corner of MUT.

     5. Click the Upload button to load the data into LIMS. Note: MUT will automatically search the .CSV data file and select the peak shear value.

     6. Users may also check the Automatic Upload checkbox for future uploads without any user intervention required.


  • Retrieve Data from LIMS

     1. Go to LIMS Reports at http://web.ship.iodp.tamu.edu/LORE/.

     2. Under Select Report, choose Physical Properties > Shear Strength Automated Vane (AVS).

     3. Under Select Sample Range, specify Expedition, Site, Hole, and Section data to retrieve.

     4. Click View data or Download data file to view data on screen or download a CSV file.

Credits

This document originated from Word document AVS_QSG_372.docx (see Archived Versions below for a file copy) written by T. Cobb (2017-12-18). Credits for subsequent changes to this document are given in the page history.

All improvements to the Quick Start Guides and User Guides are a communal effort, with honorable mention to the group of LOs, ALOs, and technicians who have helped.

Archived Versions

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1 Comment

  1. Unknown User (lawler)

    Reviewed by Nicolette 6 August 2018