Direct shear apparatus

Product Description

Direct shear apparatus

Description

 

The BTU-DDS-5F Fully Automated Direct/Residual Shear Systemis designed for determining the shear strength and residual shear strength of soils, targeting academic laboratories and research institutions. Compared to traditional systems, it features:

• Reversible stepper motor drive.
• Controllable shear rate (minimum 0.00001 mm/min).
• Power supply: 110–220 V.
• Normal loading via automatic pneumatic or mechanical motor-driven method (eliminates dead weights).
• Built-in thrust reversing mechanism for reciprocating shear.
• Operation via BTU software with pre-set test modules; automatic data acquisition and processing.
• High accuracy, high automation, easy operation.

Test Standards (International)

ASTM D3080(Standard test method for direct shear test of soils)

ASTM D6467(Ring shear residual strength – similar reciprocating shear principle)

ASTM D7608(Residual strength of saturated cohesive soils)

ISO 17892‑10(Direct shear test)

BS 1377‑7(Direct shear test)

 

The reciprocating shear capability for residual strength meets the requirements of these standards regarding shear rate, normal stress, and residual strength determination.

Specification

 

Parameter	Specification
Model	BTU-DDS-5F
Shear box (standard)	Square 100×100 mm, 60×60 mm; Optional round: Ø50, 61.4, 61.8, 63.5, 70, 100 mm
Vertical loading system	Pneumatic, with load cell and displacement transducer
Horizontal loading system	Mechanical, with load cell and displacement transducer
Servo control system	Strain and stress control
Data acquisition	Collects sensor data
Master frame	For mounting components
Software	Data acquisition and system control
Max. vertical load	5 kN
Max. horizontal shear force	5 kN
Vertical load cell	Range 5 kN, resolution 1 N, accuracy ±0.15% FS
Horizontal load cell	Range 5 kN, resolution 1 N, accuracy ±0.15% FS
Vertical displacement	Digital dial indicator, range 12.7 mm, resolution 1 μm, accuracy 3 μm
Horizontal displacement	Motor encoder, resolution 1 μm, accuracy 3 μm
Shear rate	0.00001 – 9.99999 mm/min, stepless
Software modules	Data logging, standard consolidation, standard shearing, fast shear, reciprocating shear
Power voltage	110–240 V
Working temperature	0 ℃ – 45 ℃
Instrument size	820×500×770 mm

Detail

• Reversible stepper motor drive– Enables reciprocating shear automatically for residual strength testing.
• Normal loading– Pneumatic (air pressure regulated) eliminates weights; optional mechanical motor loading also available.
• Shear box design– Standard square boxes (100 mm, 60 mm) with multiple round box options (50–100 mm diameter) for different specimen types.
• Built-in thrust reversing mechanism– Shear box assembly can change direction automatically, allowing multiple forward/backward cycles.
• High‑precision displacement measurement– Vertical: digital dial indicator (1 μm resolution); Horizontal: motor encoder (1 μm resolution).
• Modular software– Pre‑set modules: data logging, consolidation, shearing, fast shear, reciprocating shear. User can pre‑program tests and run automatically.
• Control interface– Front panel with 240×128 LCD and tactile keypads for manual operation (rate setting, fast move, stop). Full computer control also supported.
• Installation and centering– Detailed instructions for levelling, wiring, sensor connection, and centering the vertical loading rod with the shear box indent.

Applicatio

 

• Conventional direct shear tests– Fast shear, consolidated shear, slow shear to obtain peak shear strength parameters (c, φ).
• Residual strength tests– Reciprocating shear to determine residual shear strength (cᵣ, φᵣ) for slope stability analysis (especially slip zone soils).
• Geotechnical investigation– Provides design parameters for foundations, slopes, embankments.
• Research and teaching– Soil mechanics studies in universities and research institutions.
• Cyclic/reciprocating shear studies– Strength degradation, shear stiffness changes under repeated loading.

Advantages

 

• Fully automatic– Computer control from loading to data processing, reducing human error.
• No dead weights– Pneumatic normal loading eliminates cumbersome weight handling, improving efficiency and safety.
• Reciprocating shear capability– Built-in thrust reversal automatically performs forward/backward shearing to obtain residual strength without manual intervention.
• Wide shear rate range– 0.00001–9.99999 mm/min covers creep to fast shearing.
• High‑accuracy sensors– Load cell accuracy ±0.15% FS; displacement resolution 1 μm, meeting stringent research requirements.
• Multiple shear box options– Square and round sizes for various soil types (undisturbed, remoulded).
• Modular software– Users select test modules, preset parameters, and run with one click.
• Flexible operation– Manual front panel control or fully automatic computer control.
• Compact design– 820×500×770 mm, suitable for laboratory benchtops.

What To Choose

 

Select the system or accessories based on testing needs:

 

1. Peak strength only (conventional direct shear) – Use standard shear box (100×100 mm or 60×60 mm) and “standard shearing” or “fast shear” module.

 

2. Residual strength (reciprocating shear)– Core function of this system; select “reciprocating shear” module, set cycles and displacement amplitude.

 

3. Different specimen sizes–

- Fine‑grained soil / standard ring samples: round Ø61.8 mm box.

- Coarse or disturbed soil: square 100×100 mm or 60×60 mm.

- Other sizes (Ø50, Ø70, Ø100, etc.) available on request.

 

4. Normal loading method– Standard pneumatic loading requires compressed air supply. If no air source, choose mechanical motor‑driven loading option.

 

5. Budget– Fully automatic system is more expensive. If budget is limited and reciprocating shear or automatic normal loading is not needed, consider a traditional lever‑type direct shear apparatus.

 

6. Software modules– Standard configuration includes data logging, consolidation, shearing, fast shear, reciprocating shear. Confirm whether additional post‑processing or reporting functions are required.

Process Flow

Example: Consolidated undrained reciprocating shear (residual strength) on saturated clay

 

1. Specimen preparation – Cut or remould specimen (e.g., Ø61.8 mm round or 60×60 mm square). Saturate (vacuum or water immersion), measure initial water content and density.

 

2. Specimen installation – Place specimen in lower shear box, align upper box, install porous stones and loading plate. Mount vertical loading piston, connect vertical load cell and vertical displacement transducer (digital dial indicator). Centre the loading rod with the shear box top indent.

 

3. Apply normal stress – Set target normal stress (e.g., 100 kPa) via pneumatic system. In software, select “standard consolidation module”; record vertical deformation until consolidation is stable.

 

4. Set shear parameters –

- Select “reciprocating shear module”.

- Set shear rate (e.g., 0.5 mm/min).

- Set shear direction: forward to a displacement (e.g., 5 mm), then reverse; define number of cycles.

- Set stop conditions (e.g., total displacement 10 mm or shear stress stabilisation).

 

5. Start shearing– Close drainage valve (undrained) or keep open (drained). Start test. The horizontal stepper motor drives the shear box. Software records shear stress, shear displacement, vertical displacement (volume change), time, etc. Real‑time shear stress‑displacement curve.

 

6. Reciprocating shear– At forward displacement limit, motor automatically reverses. After several cycles, shear stress stabilises – this is the residual strength.

 

7. End and disassembly – Stop shearing, unload normal stress. Remove specimen, observe shear surface, clean shear box and sensors.

 

8. Data processing – Software automatically identifies peak and residual shear stresses for each shear direction. For tests at different normal stresses, plot residual strength envelope, calculate residual friction angle φᵣ and residual cohesion cᵣ. Generate test report (curves, parameters).

 

For fast shear or standard shear (no reciprocation): Select “fast shear module” or “standard shear module”, set shear rate and stop displacement, shear in one direction until failure.

 

 

Summary:The BTU-DDS-5F is a fully automated direct/residual shear system featuring pneumatic normal loading, reciprocating shear, a wide shear rate range, and high‑accuracy sensors. It is suitable for both conventional direct shear and residual strength testing. Selection should consider specimen size, need for reciprocating shear, and availability of compressed air. It is especially valuable for landslide research requiring residual strength of slip zone soils.