February 10, 2020

The dynamic simple shear with confining pressure system is supplied with sample preparation accessories to enable the user to prepare undisturbed and remoulded test specimens. The system has been designed so that the sample preparation can be conducted outside of the cell of the simple shear system to ease the sample preparation process. It is also possible to prepare the sample inside the apparatus.

Confining Pressure

1.1 Initial Setup

The following is required to prepare a sample:

Figure 1 Sample Preparation Accessories

Setup the base pedestal on a flat stable surface. Or if the sample is to be prepared in the simple shear cell secure the base pedestal into the cell with the 4 screws highlighted in Figure 24.

Figure 2 Porous Disc and Base Pedestal

Place one of the porous discs into the base pedestal.

Figure 3 Porous Disc in Base Pedestal

Next take the membrane and cut it to the required length. For 100mm diameter samples 110mm to 120mm; for 70mm diameter samples 80mm to 90mm in length.

Figure 4 Membrane Cutting

Take the cut membrane and place it over the base pedestal and then using the ‘O’ Ring tool place two of the ‘O’ Rings over the membrane sealing it to the base pedestal (see Figure 5)

Figure 5 Sealing Membrane onto Base Pedestal

Now place the two halves of the sample former together & using the ‘C’ clamp lock the two halves together.

Figure 6 Sample Former Locked Together

Now place the sample former over the base pedestal so that the membrane sticks up through the former (see Figure 7).

Figure 7 Former Placed onto Base Pedestal

Stretch the excess membrane over the top of the sample former.

Figure 8 Stretch Membrane over Sample Former

Attach the suction device to the sample former and apply suction to stretch the membrane.

Figure 9 Attaching Suction Device

Make sure that the membrane has been stretched tight against the sides of the sample former.

Figure 10 Stretched Membrane

1.2 Preparing A Remoulded Specimen

The process described below is designed to produce a specimen to a specific density.

First calculate the volume of the specimen. This can easily be done by entering the dimensions of the sample into the specimen details form in Clisp Studio. In this case enter the sample height and sample diameter, and the initial volume will be calculated.

Figure 11 Entering Sample Dimensions

To calculate the required weight of material to achieve the required density use the following equation:

Weight of material (g) = volume of sample (cm3) * density required (Mg/m3)

In the following example, a density of 1.34Mg/m3 is required for a sample volume of 298.451cm3.

298.451 * 1.34 = 400g

Place a bag or container into which you will weigh your sample onto a balance and tare the weight.

Figure 12 Place container on balance and tare the balance

Next weigh out the required amount of material into your container, in this example 400g is weighed out.

Figure 13 Weighed Material

Next place the extension ring on top of the sample former as per Figure 14.

Figure 14 Extension Ring Placed on to Sample Former

Now carefully fill the sample former with the weighed sample.

Figure 15 Filled Sample Former

Now place the weighted platen on top the material in the sample former. The weighted platen should be moved down until it touches the extension ring to form a sample of the correct height and density (see figure 17). This can be done either by pressing down on the weighted platen or using a vibrating plate (note: this is not supplied with your sample preparation accessories) to vibrate the assembly so that the sample will consolidate and the weighted platen will slowly move down giving a sample of the correct height.

Figure 16 Weighted Plated on top of sample assembly
Figure 17 Weighted Platen Touching the extension ring

Carefully remove the weighted platen and extension ring. Place the second porous disc on top of the prepared sample.

Figure 18 Extension Ring Removed and Porous Disc in Place

Now carefully place the top cap onto the porous disc. Remember the two drainage lead connectors must line up.

Figure 19 Top Cap Placed onto Assembly

Carefully roll up the membrane over the top cap.

Figure 20 Rolled Up Membrane

Fit two ‘O’ Rings over the ‘O’ Ring tool. Carefully place the two ’O’ Rings onto the top cap, sealing the membrane. The ‘O’ Rings should slot into the grooves on the top cap.

Figure 21 O Rings on Top cap
Figure 22 Removed Sample Former
Figure 32 Prepared Sample

If the sample was prepared outside the cell, then the sample needs to be carefully transferred to the cell and the base platen fixed into place using the 4 screws shown in Figure 24.

Figure 24 Location of the 4 securing screws

 The drainage leads (Back Pressure and PWP) should be flushed before fitting to remove any air from the lines.

1.3 Preparing An Undisturbed Specimen

Follow the instructions in section 1.1 – Initial setup.

A sample cutter is provided to cut an undisturbed specimen. This could be cut from a block of soil or other undisturbed sample. The sample should be trimmed and leveled in the cutter.

Figure 25 Undisturbed Specimen

The mould and specimen should be weighed so that a density can be calculated. Place the cutter onto the top of the sample former.

Figure 26 Sample Cutter on sample Former

The sample then needs to be pushed from the cutter into the sample former. This can be partially done using the weighted platen or using a wooden dolly (note this is not supplied with your accessories).

Figure 27 weighted Platen on sample cutter

Once the specimen is in the former, place a porous disc of the correct size on top of the specimen.

Figure 28 Porous Disc on Sample

Place the top cap onto the porous disc, making sure that the drainage line connection on the top cap is in line with drainage line connection on the base pedestal (see Figure 29).

Figure 29 Top cap on Sample

Roll up the membrane over the top cap.

Figure 30 Membrane Rolled Over Top Cap

Using the ‘O’ Ring tool place two ‘O’ Rings over the top cap to seal the membrane, the ‘O’ Rings should sit in the grooves of the top cap.

Figure 31 O Ring Sealing Membrane

Remove the ‘C’ clamp and sample former, and then roll down the excess membrane.

Figure 32 Prepared Sample

If the sample was prepared outside the cell, then the sample needs to be carefully transferred to the cell and the base platen fix into place using the 4 screws shown in figure 24. Before fitting the drainage leads (back pressure and PWP) these should be flushed to remove any air from the lines.

Confining Ring Setup

A confining pressure DSS can be used with a traditional stacked ring confining system. The assembly of this optional assembly is described below.

2.1 Initial Setup

The following items are required to prepare a sample:

Figure 33 Sample Preparation Accessories for Confining Ring Setup

Place the base pedestal on a flat stable surface.

Figure 34 Grooved Base Pedestal

Place the cut 70 mm membrane over the base pedestal. (see section 1.1 step 3 for cutting instructions)

Figure 35 Membrane Over Base Pedestal

Using the ‘O’ Ring tool, place 2 of the 70mm ‘O’ Rings over the base pedestal, so that the membrane is sealed against the pedestal.

Figure 36 O Ring Sealing Membrane onto Pedestal

Now place the metal split base ring over the membrane and pedestal. This ring is held together using a 70mm ‘O’ ring.

Figure 37 Split Ring over Base Pedestal

Place the two halves of the sample former together and secure them using the ‘C’ clamp.

Figure 38 Sample Former with C Clamp

Place the former over the membrane, the inside of the former where it is widest (Figure 39) is placed up, so the narrowest part of the former covers the metal split base ring, so the former rests on the base pedestal as shown in figure 40.

Figure 39 Sample Former Ridge
Figure 40 Sample Former Placed over Base Pedestal

The Teflon coated confining ring stack is made up of 12 standard rings and 2 thicker rings. Take the ring stack and arrange them so that the thicker rings are at the top and bottom of the pile.

Figure 41a Stack of Confining Rings

The confining ring stack should then be carefully place into the sampler former; the membrane will come out through the centre of the ring stack.

Figure 42 Confining Rings in Place

Stretch the excess membrane over the sample former and then place the thick extension ring over the top.

Figure 43 Extension Ring in Place

Place the suction device onto the sample former so that the membrane can be stretched if required.

Figure 44 Suction Device Attached

Remoulded Specimen

Weigh out the material accurately to achieve the required density for the volume of the sample inside the stack of rings. Details of this can be found in this document in section 1.2 steps 1 to 4.

Once weighed out, carefully place the material into the cavity.

Figure 45 Loose Material in Sample Former

Then place the weighted platen onto the sample. The weighted platen needs to be moved down so that it touches the extension ring, this way the material used will be compacted to the correct height. This can be done using a vibrating plate (not supplied) or gentle force applied from above.

Figure 46 Placing of Weighted Platen

Remove the platen and extension ring and carefully place the grooved top cap onto the sample.

Figure 47 Removed extension ring and top cap placed on sample

When placing the top cap on, make sure the connectors for the drainage lines on the top cap for Back Pressure and on the base pedestal to measure Pore Water Pressure line up (see Figure 48).

Figure 48 Aligning Drainage Lead connectors

Roll up the excess membrane and over the top cap and then release the ‘C’ clamp. Now carefully remove the sample former.

Figure 49 Removing Sample Former

Now using the ‘O’ Ring tool place two 70mm ‘O’ Rings over the top cap sealing the membrane; then roll over the excess membrane.

Figure 50 Completed Sample Preparation

 If the sample was prepared outside the cell, then the sample needs to be carefully transferred to the cell and the base platen fixed into place using the 4 screws shown in Figure 24. The drainage leads (Back Pressure and PWP) should be flushed before fitting to remove any air from the lines.

Undisturbed Specimen

Follow the initial setup for a remoulded specimen in section 2.1 until you reach step 8. Note that the extension ring is not required. Then place the suction device onto the sample former.

The undisturbed specimen should be prepared in the provided sample cutter and weighed to determine density. The cutter should be placed onto the top of the stacked rings with care being taken not to damage the membrane (see Figure 51).

Figure 51 Sample Cutter Placed onto Sample Former

The sample should then be pushed out of the cutter into the simple shear assembly using a dolly; the membrane may need to be stretched using the suction device to enable the sample to be pushed in smoothly.

Once the sample is located in place, the instructions in section 2.2 steps 4 to 7 must be followed to complete the assembly of the sample.