Adding Equipment Corrections to Clisp Studio

Overview

For some testing, system corrections may need to be applied that are not specific to a particular Instrument (e.g. Volume Change due to Cell and tube expansion in an Unsaturated Test). Alternatively, corrections may need to be applied to apparatus used in a Test that is not declared as an Instrument (e.g. frame deformation of an Oedometer). These corrections can be Added, Viewed and Removed using the ‘Equipment’ pull-down menu on the Main toolbar.

Adding Equipment

To add Equipment to Clisp Studio, click on the ‘Add’ option from the ‘Equipment’ pull-down menu on the Main toolbar. Equipment is grouped into three categories as shown in Figure 1. Clicking on a category will expand the display to show the Equipment available in that group.

Clicking on an Instrument within a category and then selecting the ‘OK’ button will always bring up a panel requesting input of the Instrument name. The name input must be unique and should be meaningful as it is referenced by Clisp Studio, when required during the Tests. Clicking on ‘OK’ will bring up the basic Control Panel for the Instrument.

Once the Equipment is created, it will be available in all Clisp Studio sessions until removed.

Consolidation Apparatus

Figure 2 shows the available Apparatus in this category. Select the required Apparatus and click on ‘OK’, enter the identifying name in the pop-up window and click on ‘OK’ again.

Consolidometer

Adding a Consolidometer as a piece of Equipment (used in one-dimensional Unsaturated Consolidation testing) allows the User to input Load and/or Pressure Calibration Corrections and brings up the basic screen shown in Figure 3 after having input a name.

The Consolidometer deflects due to both changes in cell pressure and axial load, referred to as apparatus compressibility. The apparatus compressibility must be subtracted from the measured deformations in order to correctly compute the specimen axial strain. Corrections are measured for Load and/or Pressure using a Calibration disc. Figure 4 shows the corrections.

Oedometer Frame

Adding an Oedometer Frame as a piece of Equipment allows the User to input Load correction data and brings up the basic screen shown in Figure 5, after having input a name.

The corrections are necessary to add to the cumulative vertical settlement of the specimen to allow for the deformation of the frame under each load increment. Figure 6 gives an example table.

Rowe Cell

Adding a Rowe Cell as a piece of Equipment allows the User to input Diaphragm correction data and brings up the basic screen shown in Figure 7 after having input a name.

The force exerted by the diaphragm on a soil sample may be less than that calculated from the hydraulic pressure and cross-sectional area of the Rowe cell, due to diaphragm stiffness and wall friction. The difference between actual and calculated forces can be determined the both Rowe cell, at various applied pressures.

The diaphragm pressure is controlled by the Back Pressure APC and is measured by the PWP transducer connected at the base of the cell measuring the pore pressure. Ensure that the PWP is calibrated using the Back Pressure APC so they both read the same readings.

Fill the diaphragm and cell with water to ensure there is no air trapped inside. Place soft porous spacers inside the cell to simulate a sample and then close all drainage valves. Increase the vertical pressure gradually to 600 kPa and then release it.

Now ramp the Back Pressure to a desired value (say 800 kPa) in 100 kPa steps reading the PWP sensor at regular intervals. Repeat this process at least three times. The average of the measurements at each Pressure step is calculated and subtracted from the applied Pressure to give the corrections (Figure 8).

Stress and Strength Apparatus

Figure 9 shows the available Equipment in this category. Select the required Apparatus and click on ‘OK’, enter the identifying name in the pop-up window and click on ‘OK’ again.

Permeability Cell

Adding a Permeability Cell as a piece of Equipment allows the User to input Head Loss Correction Data and brings up the basic screen shown in Figure 10.

Permeability Tests require measurement of the Pressure Loss experienced by the cell under a number of common flows. These corrections will then be used by Clisp Studio to compensate the final calculations. An example table and graph are shown in Figure 11.

Shear Box

Adding a Shear Box as a piece of Equipment allows the User to input Shear Box Correction Data and brings up the basic screen shown in Figure 12.

The measured axial displacements during consolidation and shear must be corrected for apparatus compressibility. Axial corrections are measured using a Calibration disc, applying a series of incremental Loads and recording the displacement. Shear corrections allow for the resistance of the lateral confinement and are measured by applying the shear displacement and measuring the shear force as the top platen is displaced relative to the bottom platen. Examples are shown in Figure 13.

Unsaturated Cell

It is assumed that the UNSAT System is set up (see the UNSAT System User Guide). Adding an Unsaturated Cell as Equipment allows the User to input correction data to compensate for Cell and Tube Expansion of the System and brings up the basic screen shown in Figure 14 (L).

From the ‘Instruments→ View’ menu select the appropriate instrument Channel for Volume Change (in this example an MPX3000 is used for logging) Figure 14 (R).

In the UNSAT Configuration screen, input the ambient room temperature as the Calibration temperature in the ‘UNSAT Configuration’ panel.

At the Cell Pressure APC(H), increase the pressure to 100 kPa and allow the Volume Change reading to settle.

In the ‘UNSAT Configuration’ panel, click on the ‘Insert’ button to add another line and input the pressure and associated Volume Change reading displayed.

Repeat this process for a further nine 100 kPa pressure steps so that the last line displays the Volume Change at 1000 kPa.

The UNSAT Configuration will now resemble Figure 15.

Miscellaneous Equipment

Figure 16 shows the available Equipment in this category. Select the required Apparatus and click on ‘OK’, enter the identifying name in the pop-up window and click on ‘OK’ again.

Water Tin

Adding a Water Tin allows the User to input the Weight of the Water Tin and brings up the basic screen shown in Figure 17 where the weight can be input.

About VJ Tech

We manufacture and supply soil, concrete, cement, rock and asphalt testing equipment for laboratories around the world from our base in Reading, UK.