What are the reference standards for geosynthetics direct shear?

The geosynthetics direct shear instrument determines the frictional characteristics of the sand geotextile interface by performing a direct shear test on the contact surface of the standard sand geotextile.

Detection Criteria:

gb/，astm/d5321，jtge50t1129，sl/t235-1999

Notes:

1.The specimen is tiled on the rigid horizontal pedestal that is positioned in the lower part of the shear box, and the front end is clamped in front of the shear zone, and the specimen is glued between the specimen and the pedestal, and the specimen should be flat, without folding and wrinkling after bonding, and the relative slippage is not allowed between the specimen and the pedestal in the test;

2.Install the upper shear box: fill the upper shear box with standard sand of pre-weighed quality, the filling thickness is 50mm, the thickness of the sand should be uniform, and the dry density after compacting is 1750kg m3;

3.Install a horizontal loader and apply a normal pressure of 50 kPa to the specimen with a reference weight of 50 kPa.

Test Method:

1.The specimen is laid flat on a rigid horizontal base located within the lower part of the shear cassette, with the front end clamped in front of the shear zone. The specimen is glued to the base (if P80 alumina standard friction base is used, it can not be bonded).

After bonding, the specimen should be flat, free of folds and wrinkles. Relative slippage between the specimen and the base is not allowed during the test.

2.Install the upper shear box: fill the upper shear box with standard sand of pre-weighed quality (note: standard sand is provided by the user) with a thickness of 50mm. The thickness of the sand should be uniform, and the dry density after compaction is 1750kg m3

3.Install a horizontal loader and apply a normal pressure of 50 kPa (50 kPa for the reference weight and 3 standard weights, 50 kPa for each additional pressure) to the specimen.

4.A horizontal load is applied so that the corresponding displacement between the upper and lower shear boxes is 1 mm min. Measure the shear force T continuously or indirectly, while recording the corresponding relative displacement δl, at intervals of 12 s, starting with encryption as appropriate, until the end of the test when the length of the shear plane is reached.

5.Steps to operate the LCD watch:

1) Turn on the power switch.

2) Press the function key to open the new test.

3) Enter the speed required for the test and press the confirm button.

On-screen display: "Shear Force", "Shear Stress", "Peak", "Displacement".

4) Press the start button to start the test (i.e., incremental directional stress, the first test normal stress is 50kpa, the result is valid, automatically enter the next 100kpa, 150kpa and 200kpa).

5) The displacement starts to count, when the total contact surface is completed, the test is completed, the machine will be automatically stopped, and the test data result will be displayed on the screen, and the confirmation button can be pressed if the test is correct.

6）.Press the function key to open the result query, and the test result will be displayed on the screen.

7）.Press Confirm to print and the printer starts working.