ASTM ASTM-3080 2050 Benutzerhandbuch - Seite 3

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assembly on the slide tracks being careful not to damage the home and limit switches.

SAMPLE

PREPARATION

Once extruded, the samples should be trimmed carefully down to the internal diameter of the direct shear rings, in a similar manner as for

consolidation test samples. The object is to get at least one inch of soil sample sandwiched between a layer of filter paper and a porous

stone on either side of the sample. The porous stones provide drainage and are used to distribute the pressure during the test. Place the

bottom drainage plate and then a porous stone with a filter paper into the locked shear rings. Extrude one inch of soil sample into the shear

rings. Place another piece of filter paper and porous stone on the top of the sample along with the top load pad.

SAMPLE SET-UP IN MACHINE

At this time, the direct shear rings are held together by two (2) bolts and the soil sample would be centered inside the rings. The shear rings

with sample stones are then carefully placed inside the direct shear water chamber being certain the load cell shaft is connected to the

shear rings. The shear ring assembly is placed against the end spacer. Alignment of the load cell connecting rod is required at this time.

Tighten the two (2) shear ring clamping knobs located on the left side of the water chamber. Connect the load cell to the shear ring

connecting rod using the stainless steel knurled nut.

Connect the load cell and adjust the knobs to read "0" on the load cell readout. It may be necessary to use the tare feature to read "0". The

top cross arm is usually removed for placement of the rings into the water chamber. Re-install the cross arm and adjust the height until

there is l/16" space between the arm and the stainless steel ball being certain the arm is level. The upper cross arm has a displacement

indicator pin that is positioned on the load pad ball. Adjust the dial indicator or linear displacement transducer to the top of this pin and allow

for sufficient travel when the soil sample compresses. The vertical dial indicator is positioned and set to read some arbitrary initial reading.

CONSOLIDATION OF THE TEST SAMPLE

The weight of the consolidation load arm with two upright rods lower cross arm and lower weight platform is 11.9 lbs.

The lever arm on the right side of the device has three ratios (9:1, 10:1 & 11:1). Select a consolidation load and apply the required weights.

Refer to ASTM D-3080 for sample preparation and computations.

SAMPLE SIZE

2.5" DIA.

4.0" SQ.

TEST PROCEDURES

The final dial reading after consolidation is noted on the data sheet. Adjust the shear force on the sample by adjusting the two knurled nuts

on the load cell support casting. Allow a small seating load to be exerted on the sample. The horizontal dial indicator is then adjusted to

some convenient zero point. Until this time, the two shear rings have been held together by two (2) screws -- these screws are now

removed. There are also four (4) screws for adjusting the gap between the rings once consolidation has been reached. The gap is

adjusted by turning the screws clockwise from the finger tight position. One full turn will give .031" gap. For sands of a fine to medium size,

1 1/4 of a revolution of the adjusting screw is used. For coarser sands, 1 _ revolution is used. For fine grain soils and clays, ½ revolution is

used. These values are not absolute and can be altered accordingly. Initial readings are taken at this time. The screws should be turned

evenly to prevent tilting the top ring. The test is now started at the prescribed rate of shear by setting the shear rate selector. Unless

automatically recorded, the shear and compression dial indicators will be read at various prescribed horizontal deflection readings such as

every ten divisions of the three place dial until failure. Usually the test is carried out past failure to determine the residual strength which

may be used in design. At this point the test is completed and the shear loading is stopped and the vertical load is removed.

The test is now started at the prescribed rate of shear by setting the shear rate selector. Unless automatically recorded, the shear and

compression dial indicators will be read at various prescribed horizontal deflection readings such as every ten divisions of the three place

dial until failure. Usually the test is carried out past failure to determine the residual strength which may be used in design. At this point the

test is completed and the shear loading is stopped and the vertical load is removed.

SAMPLE REMOVAL AND CLEAN-UP

Put the motor drive in reverse (towards the home position) and stop when zero (0) load is reached on the load cell readout. Remove the

sample at this time and inspect per ASTM D-3080. The vertical load is now reduced to zero (0) by adjusting the pressure regulator to zero

(0) psi. The apparatus is taken down in reverse order as assembled. The sample is extracted and weighted in order to determine the dry

density and water content at failure. The water chamber is returned to the home position by using the drive motor. Cover the roller bearing

slide assembly to prevent dust and dirt from entering the bearings.

LOWER WEIGHT PLATFORM CALCULATIONS

1 LB WEIGHT = 29.3357 LBS/SQ FT

1 KG WEIGHT = 29.3357 KGS/SQ FT

1 LB WEIGHT = 9 LBS/SQ FT

1 KG WEIGHT = 9 KG/SQ FT

MODEL 2050

DEAD WEIGHT SHEAR LOAD CHART

2.5" DIAMETER SAMPLE

AREA = 4.9087 IN²

10:1 LEVER ARM CALCULATIONS

293.357 LBS/SQ FT

293.357 KGS/SQ FT

90 LBS/SQ FT

90 KGS/SQ FT