Motorized Direct Shear Testing Machine
Applies constant horizontal displacement rates (0.01 to 2.0 mm/min) with electronic load cell monitoring shear force T.
Civil Engineering / Direct Shear Test
FREE TO EXPLORELABORATORY 20 · CIVIL ENGINEERING
Direct Shear Box Test on Cohesionless Sand (Internal Friction Angle & Dilatancy)
Determine the shear strength parameters—angle of internal friction (ϕ) and apparent cohesion (c)—of cohesionless sand under consolidated drained conditions according to ASTM D3080 / BS 1377-7. Explore interactive structural mechanics, materials simulation, and civil engineering telemetry.
STRUCTURAL MATERIALS · MECHANICS · GEOTECHNICAL · HYDRAULICS · HIGHWAYS · SURVEYING
Your virtual civil engineering laboratory.
PEAK SHEAR STRESS AT FAILURE Τ_F—
CIVIL INFRASTRUCTURE TELEMETRY
Ready to sample with Normal Stress = 150.0 kPa.
Adjust Normal Stress, 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 (50.0 to 250.0 kPa). Medium dense quartz river sand (relative density D_r = 65%). Mohr–Coulomb parameters: internal friction angle ϕ = 32.0° (tan ϕ = 0.6249 ≈ 0.6250), apparent cohesion intercept c = 5.0 kPa.
Laboratory apparatus & testing equipment.
Precision Split Shear Box Assembly (60 x 60 mm)
Rigid horizontally split brass box with clamping screws and alignment pins.
Dead-Weight Lever Arm Normal Loading System
10:1 ratio counterbalanced hanger applying vertical normal loads from 50 to 500 kPa.
Dual Linear Displacement Transducers (LVDT)
Monitors horizontal shear displacement Δx and vertical dilatancy deformation Δz to 0.001 mm.
Porous Stones & Perforated Grid Plates
Provides rough frictional boundary gripping and permits free drainage of pore water.
Specimen Tamping Tamper & Funnel
Reconstitutes dry sand to target relative density and unit weight within the shear box.
FOLLOW THE METHOD
A reason behind every step.
Determine the shear strength parameters—angle of internal friction (ϕ) and apparent cohesion (c)—of cohesionless sand under consolidated drained conditions according to ASTM D3080 / BS 1377-7. Standardized parameter settings: 50.0, 100.0, 150.0, 200.0, 250.0 kPa.
01
Shear Box Assembly & Taring
Assemble top and bottom halves of the 60 x 60 mm shear box; secure with vertical alignment pins; place base plate, porous stone, and lower grid plate into box; record initial dimensions.
02
Sand Specimen Placement & Densification
Weigh required dry sand mass to achieve target relative density (D_r = 65%); place sand into box in three layers; tamp gently to achieve exact 20.0 mm specimen height.
03
Upper Grid Plate & Loading Pad Installation
Place upper grid plate, porous stone, and loading pad on top of sand; seat assembly into water carriage on the direct shear machine.
04
Normal Stress Application & Pin Removal
Apply target normal load (50, 100, 150, 200, or 250 kPa) via the lever hanger; remove vertical alignment pins; advance separation screws to create a 0.5 mm gap between box halves to eliminate metal-to-metal friction.
05
Shear Displacement & Data Logging
Start horizontal drive motor at 0.5 mm/min; log shear force T, horizontal displacement Δx, and vertical dilatancy Δz at 15-second intervals until peak load is passed.
06
Envelope Plotting & Parameter Extraction
Repeat tests on fresh identical sand specimens at all normal stresses; plot peak shear stress τ_f versus normal stress σ_n to extract friction angle ϕ and cohesion c.
YOUR NOTEBOOK · 0 OBSERVATIONS
Turn measurements into civil engineering insight.
Points are your recorded observations. The solid regression line validates Direct Shear Test mathematical scaling.
LINEAR REGRESSION FIT · y = mx + b
τ_f = 0.6250 · σ_n + 5.0000
| # | Normal Stress σ_n (kPa) | Peak Shear Stress at Failure τ_f (kPa) | Applied normal stress σ_n (kPa) | Peak shear stress at failure τ_f (kPa) | Remove |
|---|
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CHECK YOUR UNDERSTANDING
Explain what the civil engineering metrics mean.
The Mohr–Coulomb shear strength criterion for soils is expressed as:
For clean dry cohesionless quartz sand, theoretical true cohesion c is:
If normal stress is 100 kPa and peak shear stress is 67.5 kPa with c = 5.0 kPa, tan(ϕ) is:
Dense sand shearing under low normal stress typically exhibits which volumetric behavior?
THEORY AND STRUCTURAL CONTEXT
Civil engineering background & physical principles.
Shear strength is the foundational mechanical property governing the stability of all geotechnical structures, including shallow footings, retaining walls, cut slopes, and earth dams. Unlike cohesive clays, dry cohesionless sands derive their shear resistance purely from inter-particle friction and interlocking dilatancy between mineral grains. Standardized under ASTM D3080, the direct shear test utilizes a horizontally split brass or stainless steel shear box (typically 60 x 60 mm square, 20 to 25 mm depth). A sand specimen reconstituted to target relative density is placed in the box between porous stones and perforated grid plates. A constant normal compressive stress σ_n is applied vertically via a counterbalanced lever arm or pneumatic piston. The lower half of the shear box is driven horizontally at a controlled slow displacement rate (0.2 to 1.0 mm/min) while the upper half is restrained against a calibrated proving ring or load cell that measures shear force T. As horizontal shear displacement proceeds, shear stress τ = T / A increases to a peak failure stress τ_f. According to the classical Mohr–Coulomb failure criterion, peak shear strength relates linearly to normal stress: τ_f = c + σ_n · tan(ϕ), where ϕ is the angle of internal friction and c is cohesion (c ≈ 0 for clean sand). In this laboratory, direct shear tests are performed across normal stresses from 50 to 250 kPa to evaluate the Mohr-Coulomb failure envelope and calibrate friction tangent tan(ϕ).
τ_f = 0.6250 · σ_n + 5.0000
Medium dense quartz river sand (relative density D_r = 65%). Mohr–Coulomb parameters: internal friction angle ϕ = 32.0° (tan ϕ = 0.6249 ≈ 0.6250), apparent cohesion intercept c = 5.0 kPa.