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Author(s):

E. Moortgat

Reviewer(s):

M. Hastedt, D. Houpt, H. Barnes (08/01/16), S. Herrmann; T. Cobb

Management Approval:

David J. Houpt (Supervisor of Analytical Systems)

Audience:

MLSs, RSs, Scientists

Origination Date:

4/16/08

Current Version:

372

Revised:

12/20/2017

Domain:

Physics

System:

Stress and Strength

Keywords:

Torvane, AVS, Penetrometer, compressive strength, shear strength

User Guide Contents

Table of Contents
maxLevel1

Introduction

Shear strength represents the resistance of a soil to failure in shear, a concept required in analysis for the stability of soil masses. If at a point on any plane within a soil mass the shear stress becomes equal to the shear strength of the soil, then failure will occur at that point, where material behavior changes from linearly elastic to perfectly plastic. Since shear stress in a soil can be resisted only by the skeleton of solid particles, shear strength (where the material yields: τf) should be expressed as a function of effective normal stress at failure (σ'f), where c' is the effective cohesion intercept (stress-dependent component) and Φ' is the effective angle of shearing resistance or the internal angle of friction (stress-independent component), respectively:

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  1. Select init on the Giesa GeoLAB main control screen to open a monitoring screen that shows near real-time values of torque and angle of rotation (see Figure 10).
  2. Set the sampling frequency in the sample-time field; a fair estimate is 1 measurement every 2 s.
  3. Click on the traffic light button to begin the test.
  4. Go to the Excel template screen to monitor the test in progress. When the maximum shear strength of the sediment has been reached, stop the test by clicking on the red stop-light button.
  5. Record the maximum torque and angle results on the logsheet.
  6. To save the results, go to the Excel template:
    • Select File > Save As >
    • Save to location: c:\data\strength\in
    • Name: text ID{_}offset_AVS.csv
    • Save as type: CSV (comma delimited)
  7. Close Excel after saving the file.

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All data is moved from the C:/Data/In to C:Data/Archive folder when uploaded correctly. If there is an error with the file it will be moved to the C:/Data/Error folder.
 
Figure 11. Logging into MUT Uploader.


 
Figure 12. MUT upload screen. Green check means file is in correct format for uploading to LIMS.

Giesa Vendor Contact

Giesa mbH, Heinrich-Heine-Straße 16
01723 Wilsdruff
T : +49 (0) 35204 40602, F : +49 (0) 35204 40604
mail@giesa.de, www.giesa.de

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The Torvane shear device (ELE International model 26-2261; Figure 13) enables the user to quickly determine the shear strength of cohesive soils. All that is required is a relatively flat sample area at least 2 inches (50 mm) in diameter. The device has a stress range of 0–2.5 kg/cm2 (tons/ft2), the approximate range of torque that can be easily applied by the fingers. The dial head is equipped with a mechanism to hold the maximum reading after release. The smallest division on the dial is 0.1 kg/cm2, permitting visual interpolation to the nearest 0.05 kg/cm2.
The Torvane is most accurate in fully saturated cohesive soils whose undrained strength is independent of normal pressure. The stress range permits it to be used for very soft to stiff clays. Extensive laboratory testing indicates excellent agreement in homogeneous clays between the unconfined compression test and the Torvane. The shear strength of a cohesive soil is dependent upon many factors, including rate of loading, progressive failure, orientation of the failure plane, and pore water migration during testing. The Torvane does not eliminate the effects of any of the variables.

Figure 13. Torvane Shear Device.


Three sizes of vanes are used with the Torvane:

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Figure 14. Logging into the Application/LIMS Database.
 
Figure 15. Control Screen for Entering Results and Uploading to LIMS.


Anchor_Ref302566011_Ref302566011Figure 16. Entering Torvane Results.

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Pocket Penetrometer

Failure can be defined as the maximum principal stress difference, which is the same as the unconfined compressive strength of the material ¿σ1 – ¿σ3. At a prescribed strain, shear strength ¿τf is related to compressive strength ¿¿Δσf by
¿f ¿¿¿                                                                       τf ≈τmax = (¿σ1 – ¿ – σ3)/2 = ¿¿Δσf/2.

If the compressive strength is read directly off the pocket penetrometer, the value must be divided by 2 to get the calculated shear strength.
The penetrometer is a flat-footed, spring-operated device used to measure compressive strength by pushing a 0.25 inch (6.4 mm) diameter probe 0.25 inch (6.4 mm) deep (to the red marker) below the split-core surface (select test spots with a smooth surface) (Figure 17). The mechanical scale is in units of kilograms per square centimeter, and the data are uploaded to the LIMS database in this form. The force in kg/cm2 can be converted to kPa by the following formula.:
2¿:
                                                                      2τf (kPa) = 98.1 x 2¿2τf (kg/cm2).
The maximum shear strength that can be measured with the pocket penetrometer is 4.5 kg/cm2.
A 1 inch adaptor foot is available for measuring in very soft sediments. This provides a 16 times increase in piston area. An allen wrench is used to loosen and tighten the set screw that holds the foot to the piston. When the foot is used, multiply the scale readings by 1/16 (0.0625).



Anchor_Ref302566055_Ref302566055
Figure 17. Pocket Penetrometer.

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  1. Choose an appropriate test location on the sample.
  2. Measure the offset from the top of the sample section (cm) and record in the logsheet, along with section text ID and whether the adapter foot is being used.
  3. Return the red ring to position against the penetrometer body, making sure that the front edge is at the zero reading.
  4. Grip the handle firmly, holding the penetrometer at a right angle to the soil surface, and insert the shaft into the soil with a smooth constant force to the groove ¼ inch from the tip. If the adapter foot is used on very soft soil, push the foot into the soil the total thickness of the foot.
  5. Read the unconfined compressive strength (kg/cm2) from the scale. The reading is located on the lower side of the red ring; the side closest to the handle.
  6. Record the result on the logsheet.

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Entering Results and Uploading Data to LIMS

All strength results are uploaded to the LIMS database via a Java program. To run the program, double-click on the icon penetration.

  1. Log into the application with your LIMS username/password (Figure 18) to open the main application window (Figure 19).
  2. Select the Penetrometer radio button.
  3. Select Label ID info. (Figure 20). Select the sample from the Sample Table underneath the hierarchy search.
  4. Enter pertinent info (Offset, Adapter ID, Alignment, and Raw Instrument Reading).
  5. Press Save. This uploads the measurement into LIMS.


Anchor_Ref302566076_Ref302566076
Figure 18. Logging in to the Application/LIMS Database. Anchor


RTF36393333383a204669675469RTF36393333383a204669675469 
Anchor_Ref302566084_Ref302566084Figure 19. Control Screen for Entering Results and Uploading to LIMS.
AnchorRTF35363333353a204669675469RTF35363333353a204669675469


Anchor_Ref302566094_Ref302566094

Figure 20. Entering Penetrometer Results.

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LIMS Integration

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Sample and Analysis Attributes and Components


Analysis

Component

Unit

Explanation

VANE_SHEAR

offset

cm

Offset from top of section; location of measurement in section

 

penetration_direction

  • into X
  • into Y
  • into Z
  • into –Z

 

x-, y-, or z-axis measurement

 

rotation_rate

deg/s

Geisa vane rotation rate

 

shear_strength

Pascal

 

 

residual_strength

Pascal

 

 

max_torque_angle

°circ

 

 

residual_torque_angle

°circ

 

 

comment

 

From AVS data entry form

PENETRATE

offset

cm

Offset from top of section; location of measurement in section

 

penetration_direction

  • into X
  • into Y
  • into Z
  • into –Z

 

x-, y-, or z-axis measurement

 

adapter_foot

  • yes (1/16)
  • no (1)

 

Was adapter foot used for very soft sediment?

 

compression_strength

kg/cm2

Converted result

 

comment

 

From PenStrength data entry form

TOR_SHEAR

offset

cm

Offset from top of section; location of measurement in section

 

penetration_direction

  • into X
  • into Y
  • into Z
  • into –Z

 

x-, y-, or z-axis measurement

 

adapter_id

  • regular (1.0)
  • large (0.2)
  • small (2.5)

 

Which blade was used on the device?

 

shear_strength

kg/cm2

Converted result

 

comment

 

From PenStrength data entry form

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  1. Open browser and go to {*}{_}http://ship.iodp.tamu.edu/LORE/_*
  2. Under Select Report, click Physical Properties > Strength, Automated Vane, Torvane, or Penetrometer, as applicable.
  3. Under Select Sample Range, enter Expedition, Site, Hole, etc., as needed to narrow the data search.
  4. Click View data or Download data file to view or download the data.

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Health, Safety, & Environment

–Do not force the blade into sediment that is too hard.
–Do not expose any part of the unit to force >40 N; twisting moment may exceed 4 Nm.

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Maintenance & Troubleshooting

Maintenance

Daily

Thoroughly clean AVS frame, removing dust and material, taking special care with threaded rods and bores.

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Troubleshooting

AVS Status Displays


Status message

Meaning

ready for use

FL2 is not busy; press START to begin a test

attempt runs

Manually initiated test; terminate using the STOP button

equipment disturbed

Error detected; see below

ST attempt runs

PC-initated test; START and STOP buttons are deactivated

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When the AVS controller detects an error, the NET light on the front of the controller flashes and an error message displays.

Error message

Explanation

Action

Storage error

Internal memory error

Requires electronics repair

Maximum strength

At least 1 internal force sensor has reached maximum value; further testing may damage force sensor

Terminate test and restart with a smaller vane

Overflow condition

Vane rotated > 8000°

Add 8000° to final result for this test

Force sensor is missing

–A force sensor is not connected
–Force sensors have been switched

Check cable connections at back of FLSS

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Giesa Installation Information

AVS Hardware

FL2 Frame

  • S/N 745-1, Made in Germany
  • Analog force sensors (load cells):
  • Type: KAB K1. 0,1 Bj.2004, Made in Germany
  • mV/V = 50 N FNr 04-2929
  • IP67
  • A.S.T. GmbH Dresden
  • Mars chnerstrasse 26 D-01287 Dresden
  • Excitation (plus)(+)/SP+ brown
  • Sense (plus)(+)/F+ gray
  • Screen/SCH black
  • Signal (plus)(+)/S+ red
  • Sense (–)/F– blue
  • Excitation (–)/SP– green
  • Signal (–)/F– white
  • Stepper motor with all cable connections
  • Portescap Turbo Disc™ PP 520 00466, ED 0304
  • Made in Switzerland
  • Vane clamping device (uses keyless clamping chuck)

FL2SS Controller

  • S/N 745
  • Made in Germany
  • Control box inputs
    • Left torque : analog force sensor (Nm)
    • Right torque : analog force sensor (Nm)
    • Motor : driving motor
    • IGR : rotational sensor

Step-down Converter

  • SIMRAN SYM-200DE
  • Made in China

Computer Hardware

The Giesa equipment is controlled by a PC running Windows Operating System. The FL2 uses a RS232 interface for automatic control of the entire test process. Remove any other hardware from the serial ports; the data send for port probing might be misinterpreted and cause errors in unsupported devices. RS232 settings are:

  • COM port
  • 9600 baud : 8 data bits : no parity : 1 stop bits : no flow control

Power Requirements

  • Power requirements: 230V AC, 50/60 Hz, 0.3 A
  • Attach this unit to mains socket with a grounded earth.
  • To avoid any potential electrical disturbances, connect the PC and the FL2SS to the same circuit.

Maintenance

  • It is recommended that the force sensors be adjusted/tuned annually by Giesa mbH.
  • Change the fuse on the FL2SS only with the power supply cord unplugged from mains.
  • Make sure the unit is powered off before exchanging cables.
  • Do not expose the unit to forces over 40 N; the twisting movement may exceed 4 Nm.

Software

AVS is controlled by a PC with Windows environment that must have the following software installed to run and upload AVS measurements:

  • GeoLab
  • Giesa license file
  • Microsoft Excel
  • LabVIEW uploader
  • Java

GeoLab

Install the GeoLab software by running the setup.exe file found on the software volume or a backup media CD. For full software functionality, a license must be obtained from Giesa mbH. Without a license, the software is limited to 50 values per measurement.

Geisa License

Install the new GERAETE.DBF file in the installation directory. This file contains the new hardware in an encrypted style. Do not try to edit this file. Any changes might damage or even destroy the file and render the program unusable.

Excel

Microsoft Excel will also need to be installed. The Giesa software uses Excel as an interface. Values are written to, and parameters read from, predefined spreadsheet cells providing full flexibility of Excel functions to the measurements. The Excel parameters take precedence over the Giesa parameters.

RS-232 COM

At startup, the program searches all available serial ports for hardware. All hardware needs to be online at this point. Detected hardware and ports are displayed graphically. A flashing red dot signals a hardware error. Double-click the dot for more details.

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