Standard Casagrande Mechanical Liquid Limit Device
Brass cup dropping 10.0 ± 0.2 mm onto a calibrated hard ebonite rubber base via hand crank.
Civil Engineering / Casagrande Liquid Limit
FREE TO EXPLORELABORATORY 25 · CIVIL ENGINEERING
Atterberg Consistency Limits & Casagrande Liquid Limit Determination
Determine the Liquid Limit (LL), Plastic Limit (PL), and Plasticity Index (PI) of cohesive soil using the Casagrande mechanical liquid limit cup according to ASTM D4318 / BS 1377-2. Explore interactive structural mechanics, materials simulation, and civil engineering telemetry.
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Your virtual civil engineering laboratory.
MOISTURE CONTENT W—
CIVIL INFRASTRUCTURE TELEMETRY
Ready to sample with Blow Count N = 25.0 blows.
Adjust Blow Count N, then execute civil engineering measurement.
Civil engineering telemetry is evaluated rigorously using 64-bit IEEE 754 precision. Residuals reflect ordinary least-squares regression across successive observations. Continuous data structures support high-fidelity structural mechanics and geotechnical continuum modeling.
Civil engineering assumptions and boundary condition limits
The civil engineering physical models apply within the specified calibrated operational window (15.0 to 40.0 blows). High-plasticity alluvial clay (CH under USCS). Linearized flow curve relates moisture content w directly to log10(N) with flow index slope -14.5000 %/log(blow) and 0-blow intercept 62.00%. Liquid limit LL at N = 25 blows evaluates as w(25) = -14.50 · log10(25) + 62.00 = -14.50(1.39794) + 62.00 = 41.73%.
Laboratory apparatus & testing equipment.
ASTM Flat Grooving Tool (11 mm wide)
Precision brass/plastic grooving tool cutting clean 2.0 mm wide, 8.0 mm deep central channel.
Ground Glass Mixing Plate & Spatulas
Smooth frosted glass plate (450 x 450 mm) and flexible steel spatulas for paste blending.
Drying Oven & Tare Moisture Cans
Electric oven maintaining 110 ± 5 °C and airtight aluminum containers weighing moisture portions.
Drop Height Calibration Gauge
10.0 mm machined step gauge verifying exact cup drop height prior to testing.
Analytical Top-Loading Balance
Weighs soil moisture portions to 0.01 g resolution (capacity 200 g).
FOLLOW THE METHOD
A reason behind every step.
Determine the Liquid Limit (LL), Plastic Limit (PL), and Plasticity Index (PI) of cohesive soil using the Casagrande mechanical liquid limit cup according to ASTM D4318 / BS 1377-2. Standardized parameter settings: 15.0, 20.0, 25.0, 30.0, 35.0, 40.0 blows.
01
Soil Fraction Preparation & Drop Height Calibration
Pass air-dried soil through the 425 μm (No. 40) sieve; take 250 g; calibrate Casagrande cup drop height to exactly 10.0 mm using the thickness gauge on the grooving tool.
02
Initial Moisture Conditioning
Place soil on glass plate; add distilled water gradually, working thoroughly with spatulas for 10 minutes to produce a uniform, smooth plastic paste.
03
Cup Placement & Leveling
Place a portion of paste into the brass cup above the hinge; spread with spatula to maximum depth of 10 mm; level surface parallel to rubber base.
04
Standard Central Grooving
Draw grooving tool firmly along the cup centerline from hinge toward front in a single continuous stroke, dividing soil pat into two symmetrical halves.
05
Cranking & Closure Recording
Turn crank at steady rate of 2 blows per second; count blows until soil halves flow together and close across a continuous bottom length of 12.7 mm; record blow count N.
06
Moisture Sampling & Multi-Point Sweep
Extract a 15 g sample across the closed groove; weigh immediately; dry in oven at 110 °C to determine w; repeat at varying moisture contents between 15 and 40 blows to establish the Flow Curve.
YOUR NOTEBOOK · 0 OBSERVATIONS
Turn measurements into civil engineering insight.
Points are your recorded observations. The solid regression line validates Casagrande Liquid Limit mathematical scaling.
LINEAR REGRESSION FIT · y = mx + b
w = -14.5000 · log10(N) + 62.0000
| # | Casagrande Cup Blow Count N (blows) | Moisture Content w (%) | Common logarithm of blow count log10(N) | Moisture content w (%) | Remove |
|---|
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CHECK YOUR UNDERSTANDING
Explain what the civil engineering metrics mean.
The Liquid Limit is defined as the moisture content corresponding to a Casagrande cup blow count of:
The standard drop height of the Casagrande brass cup is:
The length of groove closure required to terminate the blow count is:
If a soil has a Liquid Limit of 45% and a Plastic Limit of 20%, its Plasticity Index (PI) is:
THEORY AND STRUCTURAL CONTEXT
Civil engineering background & physical principles.
The consistency and physical behavior of cohesive fine-grained soils depend profoundly on moisture content rather than particle size alone. In 1911, Swedish chemist Albert Atterberg defined four fundamental physical states of soil consistency: solid, semi-solid, plastic, and liquid. In 1932, Arthur Casagrande standardized the mechanical boundary between the plastic and liquid states—the Liquid Limit (LL)—using the mechanical cup apparatus (ASTM D4318). The Liquid Limit is defined as that gravimetric moisture content at which a trapezoidal groove cut through a pat of soil in a brass cup closes over a length of exactly 12.7 mm (0.5 inches) upon receiving exactly 25 standard mechanical blows dropped from a height of 10.0 mm at 2 blows per second onto a hard rubber base. At the liquid limit, all fine-grained soils possess an identical, tiny undrained shear strength of approximately 1.7 to 2.4 kPa. Because achieving exactly 25 blows in a single trial is virtually impossible, tests are performed across four to six trials with blow counts spanning 15 to 40 blows. Plotting moisture content w against log10(N) yields a straight line termed the Flow Curve, whose slope defines the Flow Index I_f = -dw / d(log10 N). The moisture content at N = 25 blows interpolated from the flow curve provides the Liquid Limit LL. Combined with the Plastic Limit (PL, moisture where 3.2 mm soil threads crumble), the Plasticity Index PI = LL - PL classifies soils on Casagrande's Plasticity Chart under the Unified Soil Classification System (USCS). In this laboratory, Casagrande tests are performed to evaluate the Flow Index I_f and establish LL.
w = -14.5000 · log10(N) + 62.0000
High-plasticity alluvial clay (CH under USCS). Linearized flow curve relates moisture content w directly to log10(N) with flow index slope -14.5000 %/log(blow) and 0-blow intercept 62.00%. Liquid limit LL at N = 25 blows evaluates as w(25) = -14.50 · log10(25) + 62.00 = -14.50(1.39794) + 62.00 = 41.73%.