Direct Shear Testing – Soil & Rock
Atlas Engineering and Technology Group delivers accurate, timely and NATA-endorsed Direct Shear Testing for soil and rock specimens across Sydney and regional NSW.
What is Direct Shear Testing?
The shear strength of a soil or rock material is its ability to resist failure and sliding along a plane internally. It determines the shear strength parameters (cohesion $c$ and angle of internal friction $ \\phi $) by applying a horizontal force along a pre-defined failure plane. The results guide design decisions for:
- Shallow and deep foundations
- Retaining walls and basement structures
- Embankments, slopes and earth-dams
- Pavement sub-grade assessments
Applicable Standards
- AS 1289.6.2.2 – Direct Shear Test of a Soil Specimen in a Shear Box
Our Capabilities
- Automated pneumatic and dead-weight shear boxes (60 × 60 mm, 100 × 100 mm, 300 × 300 mm)
- Normal stresses up to 1 MPa (soils) and 5 MPa (rock)
- Consolidated drained (CD), consolidated undrained (CU) and residual strength testing
- Temperature-controlled baths (5 °C – 40 °C) for specialised studies
- Real-time data acquisition at 0.01 kN and 0.001 mm resolutions
Typical Workflow
- Sample receipt & inspection (photographs, logging, moisture determination)
- Sample trimming to target dimensions and density/void ratio checks
- Consolidation under required normal stress until rate of deformation < 0.002 mm/h
- Shearing at constant displacement rate (0.5 % to 1 % strain per minute)
- Plotting shear stress vs horizontal displacement to obtain peak and residual envelopes
- Quality review, NATA sign-off and electronic delivery of the report
Sample Requirements
| Material | Minimum Size | Maximum Particle Size | Moisture Sealing | Preferred Container |
|---|---|---|---|---|
| Cohesive soil | 70 mm Ø, 60 mm high | 6 mm | Double plastic wrap | Screw-cap jar |
| Granular soil | 150 mm Ø, 150 mm high | 19 mm | Heavy-duty zip bag | Bucket with lid |
| Rock core | NX (54 mm Ø), ≥50 mm long | 50 mm | Paraffin dipped | Core tray |
Deliverables
- NATA-endorsed PDF report
- Shear stress–displacement graphs
- Design parameters $c$ and $ \\phi $ at user-specified normal stress range
- Commentary on specimen behaviour, strain compatibility and QA notes