Hardware

Shearbase and EMDCSS

Direct Shear Setup for Shearbase and EMDCSS

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Shearbase:

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To prepare a sample for testing, collect together the items shown above and then assemble as described below.

First place the platen and porous plate into the lower sample holder.

Then place the upper sample holder (with swan-neck ram attached) on top and screw it down onto the lower sample holder. Place this assembly into the bath, and then use the adjuster screw on front of the bath to force the assembly towards its back.  

If preparing a cohesive sample use the provided cutting square to cut the correct size. Trim the sample flush with the top of the cutter.  Place the up-turned cutter into the groove on top of the upper sample holder.  Push the sample into the sample holder using a dolly or a porous stone.

If preparing a non-cohesive specimen place this directly into the sample holder as per local test specifications, and then place the porous stone on top.  Place the metal topcap over the porous disk, ensuring it locates correctly within the inner recess of the upper sample holder.

Insert the bath assembly into the Shearbase, note it is easier to have the Shearbase set with the horizontal platen a few mm away from the test starting point (up direction on the horizontal axis) before placing the bath in.  Screw the two bolts through the front of the bath into the platen to secure it in place.  Set the zero offset for force on the horizontal axis controller, and then target a small force (say 0.005kN) to seat the ram up against the rear of the machine.  Tighten the rear knurled ring to hold the upper shear plate in place during the test.

Place the steel ball on top of the topcap.  Extend the ram so there is approximately 1mm gap between the ram and ball using the four screws on the ram clamp.  Set the axial controller force offset to zero, then dock by targeting a small load (eg 0.005kN)

Before commencing a shear test the clamping screws that lock the two halves together must be removed.  The upper half of the box is raised by loosening the rear knurled ring, inserting lifting screws in the opposite holes, turning the lifting screws so that the plates just separate, then re-tightening the rear knurled ring at the new height.  The lifting screws are then retracted completely.  Note: If consolidation is to be performed first, the clamping screws are removed and upper plate is raised after consolidation is completed.

In the direct shear test a specimen can be stopped from drying out by filling the water bath to a point above the top of the specimen. The specimen is allowed to drain (and consolidate under a desired normal force prior to shearing).  Alternatively specimens such as sand may be tested dry.  Note the level of pre saturation of the porous plates will depend on the type of soil test being conducted.

EMDCSS:

Following the procedure for fitting the Direct Shear components into a Shearbase, the swan neck attachment is what differentiates this setup in the two devices.

Rather than fitting the swan neck to the back of the machine, the attachments designed for an EMDCSS will attach across the columns at the front of the machine.

Best practice is to loosely fit the clamps around the columns. This will then allow the bar to slide up into place interlocking with the retaining pin. Once set and level with the system, the clamps can be tightened around the columns.

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