Praktikum Geoteknik - MODUL 12 UJI KUAT GESER LANGSUNG TANAH (DIRECT SHEAR TEST)

Summary

This video demonstrates a practical laboratory experiment to determine the shear strength and cohesion of soil under different conditions, following Indonesian standards SNI 3420:2016. It provides a step-by-step guide on preparing undisturbed soil samples, using tools like the direct shear apparatus, extruder, proving rings, and loading weights. The video details the process of measuring, molding, and testing soil samples, recording the data systematically, and repeating the procedure for multiple samples. Emphasis is placed on precision, proper use of equipment, and careful observation, offering viewers a comprehensive overview of soil mechanics testing in a clear and methodical manner.

Takeaways

• 😀 The video demonstrates a direct shear test on soil samples following SNI 3420:2016 for unconsolidated-undrained conditions.
• 😀 Two soil conditions are highlighted: consolidated and unconsolidated, with this experiment focusing on the unconsolidated scenario.
• 😀 Essential tools include the shear test set, dasir box, porous stones, loading bench, proving rings (horizontal and vertical), load hanger, connecting pins, extruder, molding ring, calipers, wire saw, scale, filter paper, and stopwatch.
• 😀 Soil samples are prepared by extruding the soil into molding rings, cutting excess with a wire saw, leveling, and weighing before testing.
• 😀 The soil sample is carefully placed in the shear box with porous stones and filter paper at the top and bottom to ensure proper load distribution.
• 😀 Connecting pins are used initially to prevent the shear box from shifting during sample placement and are removed before testing.
• 😀 Proving rings (horizontal and vertical) must be zeroed before starting the test to ensure accurate displacement readings.
• 😀 Loads are applied gradually on the load hanger (starting at 0.8 kg), and displacement readings are recorded at 33-second intervals.
• 😀 Observations from the test allow calculation of soil parameters such as shear strength, cohesion, and internal friction angle.
• 😀 After testing, all equipment should be cleaned and organized to maintain proper lab conditions.
• 😀 The procedure emphasizes precision in sample preparation, instrument setup, and recording data to ensure valid and reliable results.

Q & A

What is the main purpose of the direct shear test in this practical?

The direct shear test is performed to determine the shear strength parameters of soil, including the angle of internal friction and cohesion, under specific consolidation conditions.

Which standards are referenced for conducting the soil shear tests?

The tests reference SNI 2813:2008 for consolidated conditions and SNI 3420:2016 for unconsolidated, undrained conditions. In this practical, SNI 3420:2016 is used.

What types of soil samples are used in this experiment?

Undisturbed soil samples are used, with three samples prepared for testing.

List the main tools and equipment required for this direct shear test.

The main tools are: shear box set, porous stones, loading frame, horizontal and vertical dial gauges, weight hanger, connecting pins, extruder, ring molds, calipers, wire saw, balance, loading weights, filter paper, and stopwatch.

How is the soil sample prepared before placing it in the shear box?

The soil is extruded into a ring mold, trimmed with a wire saw, weighed, and then carefully placed into the shear box with porous stones and filter paper at the top and bottom.

What is the function of the connecting pins during sample preparation?

The connecting pins stabilize the shear box to prevent movement during sample placement and assembly.

Describe the process for conducting the shear test once the sample is in the box.

After placing the sample, the load is applied via the weight hanger, the connecting pins are removed, and readings are taken from the horizontal and vertical dial gauges and proving ring at regular intervals until shear occurs.

What are the key measurements recorded during the test?

The key measurements include horizontal displacement, vertical displacement, and shear force, which are used to calculate shear stress and soil strength parameters.

Why is it important to zero the dial gauges before starting the test?

Zeroing ensures that any initial offsets are removed, providing accurate readings of displacement and force during the test.

How are different load conditions applied to the soil samples?

Different weights, such as 0.8 kg, 1.6 kg, and higher, are hung on the weight hanger to apply varying normal stresses to each sample during testing.

What should be done after completing all shear tests?

All equipment should be cleaned, organized, and returned to its proper place to maintain the lab and ensure safety.

Why is using undisturbed soil critical for this experiment?

Undisturbed soil preserves the natural structure and moisture content, which is essential for accurate measurement of shear strength and realistic engineering analysis.