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In liquid limit test the height of fall of cup is kept as
cm
cm
cm
cm
cm
In the Casagrande's liquid limit apparatus, the standard height of fall of the cup is precisely 1 cm. This standardization is critical to ensure uniformity in the shearing energy imparted to the soil sample during the test across different laboratories.
In the Casagrande's liquid limit apparatus, the standard height of fall of the cup is precisely 1 cm. This standardization is critical to ensure uniformity in the shearing energy imparted to the soil sample during the test across different laboratories.
HfтАЛ=10┬аmm тАФ Standard height of fall defined by IS 2720 (Part 5)
The apparatus uses a hand-operated crank to lift the brass cup, which then drops onto a hard rubber base. The 1 cm drop height ensures that the energy per blow is consistent, allowing the soil to flow under a controlled impact, which is essential to define the moisture content at which 25 blows are required to close a standard groove.
The liquid limit (LL) is defined as the water content at which a groove closes over 12.7 mm after 25 blows.
The apparatus must be calibrated using a gauge block to verify the 1 cm height.
Any variation in the fall height significantly alters the blow count, leading to erroneous LL results.
Ensures consistency across global geotechnical testing
Repeatability of results for soil classification
Human error in manual cranking
Requires frequent calibration of the base hardness and drop height
Determining the consistency limits of fine-grained soils
Classification of soils according to the Unified Soil Classification System (USCS)
The hard rubber base of the apparatus has a Shore D hardness of 90-95.
The tool used for creating the groove is typically the Casagrande grooving tool or ASTM tool.
A is correct тАФ The standard drop height for the brass cup in the liquid limit test is exactly 1 cm (10 mm).
Remember that the liquid limit is defined at 25 blows; if a question asks about the drop height of the falling cone apparatus (used for plastic limit or alternative LL), that value is different (often 20 mm).