AZA 0920 LABORATORY VANE SHEAR APPARATUS (MOTORISED)

Description

AZA 0920 Laboratory Vane Shear Apparatus (Motorised): Precision Soil Strength Measurement by Azalab

The Azalab AZA 0920 Laboratory Vane Shear Apparatus (Motorised) is an advanced and indispensable instrument for modern geotechnical laboratories. It is specifically designed to accurately determine the undrained shear strength ($c\_u$) and sensitivity of cohesive soils, such as clays and silts, directly from undisturbed or remolded soil samples. The motorized operation is a key feature, providing a constant and precise rate of vane rotation, which is crucial for achieving consistent and reliable test results as per international standards. This apparatus is vital for research, quality control, and engineering design related to foundation stability, slope stability, and embankment analysis in India and globally.

The Science Behind the Motorised Laboratory Vane Shear Test

The laboratory vane shear test is a direct shearing method, analogous to its in-situ counterpart, but performed in a controlled laboratory environment on prepared soil samples. The basic principle involves:

1. Sample Preparation: An undisturbed soil specimen, typically obtained from a sampling tube or a block sample, is carefully placed in a sample container. The container dimensions are chosen to accommodate the test.
2. Vane Insertion: A cruciform vane of specific dimensions is gently inserted into the center of the soil specimen. The vane blades are designed to penetrate the soil with minimal disturbance.
3. Motorized Torque Application: The AZA 0920 Motorised Laboratory Vane Shear Apparatus uses an electric motor and a precision gearbox to apply a controlled and constant rate of torque to the vane. This smooth, continuous rotation ensures that the shear failure occurs progressively and consistently.
4. Torque Measurement: As the vane rotates, the torque required to overcome the soil’s resistance to shear is measured. This is typically done via a calibrated torsion spring system connected to a graduated dial, which registers the angle of twist, directly correlating to the applied torque. The peak (maximum) torque is recorded, representing the undisturbed shear strength.
5. Shear Strength Calculation: The measured peak torque is then converted into undrained shear strength ($c\_u$) using a formula that accounts for the vane’s dimensions (diameter and height) and the geometry of the shear surface created in the soil. The general formula for undrained shear strength ($c\_u$) is: c_u=fracT_maxK Where $T\_max$ is the maximum torque and $K$ is a vane constant derived from the vane dimensions ($D$ for diameter, $H$ for height), usually K=piD2left(fracH2+fracD6right) for a standard vane.
6. Sensitivity Determination: After the peak shear strength is determined, the vane is rapidly rotated for several revolutions (e.g., 5 to 10 revolutions) to completely remold the soil. A subsequent test is performed to measure the remolded shear strength. The ratio of the undisturbed strength to the remolded strength gives the sensitivity of the clay, a critical parameter for understanding how much a soil’s strength degrades upon disturbance.

Advantages and Key Features of the AZA 0920 Motorised Laboratory Vane Shear Apparatus

The motorized operation of the AZA 0920 offers distinct advantages over manual systems:

• Precise Control: Ensures a constant and uniform rate of rotation, crucial for obtaining accurate and reproducible shear strength values, especially for time-dependent soil behavior.
• High Accuracy: Eliminates human error and inconsistencies associated with manual torque application.
• Versatility: Capable of testing both undisturbed and remolded samples, allowing for the determination of soil sensitivity.
• Efficiency: Automated operation allows technicians to focus on data recording and other tasks.

Key Features of the Azalab AZA 0920 Motorised Laboratory Vane Shear Apparatus: Azalab’s AZA 0920 apparatus is built with precision engineering and user-friendly features:

• Motorized Drive System: Electrically operated motor with a precision gearbox providing a constant rate of rotation (e.g., 1/60 RPM or 0.1 degrees/second) as required by standards. Suitable for 230 V A.C., Single Phase power supply.
• Accurate Torque Measurement: Features a calibrated torsion spring system with multiple interchangeable springs of varying stiffness (e.g., 2 kgf/cm², 4 kgf/cm², 6 kgf/cm², 8 kgf/cm²), allowing for testing a wide range of soil strengths. A high-resolution graduated dial indicates the angle of torque.
• Vane Head Assembly: Torque head adjustable in height by a lead screw and drive wheel, enabling precise lowering of the vane into the specimen with minimal disturbance.
• Standard Vane Blades: Supplied with a set of standard cruciform vanes (e.g., specific dimensions like 12.7 x 12.7 mm, 12.7 x 19.0 mm, 12.7 x 25.4 mm, 20 x 30 mm, 25.4 x 50.8 mm, 30 x 60 mm, 40 x 80 mm as per standards) fabricated from durable material.
• Sample Container: Includes a container for holding the soil sample. The design often accommodates standard sampling tubes (e.g., 38 mm I.D. x 150 mm long) or other cylindrical samples.
• Robust Construction: Made from durable materials ensuring long-term performance and stability in a laboratory environment.
• Digital Readout (Optional): Some advanced versions may include a digital load cell and display for direct torque readings and data logging capabilities, enhancing precision and ease of use.
• Wooden Carrying Case: Supplied complete in a sturdy wooden carrying case for safe storage and transport.

Applications and Standards Compliance in the Indian Context: The AZA 0920 Motorised Laboratory Vane Shear Apparatus is widely used in:

• Geotechnical Laboratories: For routine testing of soil samples obtained from boreholes or test pits.
• Civil Engineering Projects: Providing essential soil parameters for the design of foundations, earthworks, and stability analysis of slopes and embankments, especially in areas with soft clayey soils.
• Academic & Research Institutions: For studying the shear strength characteristics of various cohesive soils under controlled conditions.
• Quality Control: Ensuring soil properties meet design specifications for construction materials.

The apparatus is designed and manufactured to comply with the most relevant national and international standards, ensuring that test results are accepted globally:

• IS 2720 (Part 30):1980 (Reaffirmed 2021): Indian Standard Methods of Test for Soils – Laboratory Vane Shear Test.
• ASTM D4648/D4648M: Standard Test Methods for Laboratory Miniature Vane Shear Test for Saturated Fine-Grained Clayey Soil.
• BS 1377-7: Methods of test for soils for civil engineering purposes – Shear strength tests (total stress).

Azalab’s Commitment to Laboratory Excellence: Azalab is dedicated to providing state-of-the-art geotechnical testing equipment that meets the rigorous demands of research and industry. The AZA 0920 Laboratory Vane Shear Apparatus (Motorised) embodies our commitment to precision, reliability, and ease of use. By offering an automated solution for a critical soil mechanics test, we empower engineers and researchers across India to obtain accurate soil strength data, facilitating safer and more efficient design and construction practices. Our equipment is built to the highest quality standards, supported by comprehensive technical assistance and after-sales service.

Specifications:

• Model: AZA 0920
• Product Type: Laboratory Vane Shear Apparatus
• Operation: Motorized (Electrically operated)
• Power Supply: 230 V A.C., Single Phase (standard Indian supply)
• Rotation Rate: Constant rate of rotation, typically 1/60 R.P.M. (or 0.1 degrees per second) as per standards.
• Torque Measurement:
  • Method: Calibrated torsion spring system.
  • Springs: Supplied with a set of four calibrated springs (e.g., approx. 2, 4, 6, 8 kgf/cm² or specific ranges in N.m).
  • Readout: Graduated dial indicating angle of torque, with a resettable pointer and a maximum pointer for peak reading.
• Vane Head Assembly: Adjustable height via lead screw and drive wheel for precise lowering of vane.
• Vane Blades: Set of standard cruciform vanes (e.g., specific dimensions like 12.7×12.7mm, 25.4×25.4mm, 50x50mm, or others as per specific standard requirements).
• Sample Container: Supplied with a container for soil samples. Can also accommodate standard sampling tubes (e.g., 38mm I.D. x 150mm long).
• Construction: Robust and durable metal construction, typically steel.
• Standards Compliance: IS 2720 (Part 30):1980 (Reaffirmed 2021), ASTM D4648/D4648M, BS 1377-7.
• Included Accessories: Set of four calibrated springs, set of standard vanes, sample container, calibration chart for springs, wooden carrying case.
• Country of Origin: Made in India.

FREQUENTLY ASKED QUESTIONS (FAQ):

• Q: What is the primary function of the AZA 0920 apparatus?
  • A: It is used in a laboratory setting to determine the undrained shear strength and sensitivity of soft to medium cohesive soils (clays and silts).
• Q: Why is it important that the apparatus is motorized?
  • A: Motorized operation ensures a constant and uniform rate of vane rotation, which is critical for accurate and reproducible test results, as prescribed by international standards.
• Q: What type of soil can be tested with this apparatus?
  • A: It is specifically designed for saturated, fine-grained, cohesive soils such as soft clays and silts. It is not suitable for granular soils (sands, gravels).
• Q: Does it come with different vane sizes?
  • A: Yes, it is typically supplied with a set of standard cruciform vanes of various dimensions to test different soil strengths and comply with standards.
• Q: What standards does this apparatus comply with?
  • A: It complies with IS 2720 (Part 30), ASTM D4648, and BS 1377-7.
• Q: Can it test both undisturbed and remolded samples?
  • A: Yes, it is capable of testing both undisturbed and remolded soil samples, allowing for the determination of soil sensitivity.
• Q: What is “soil sensitivity” and how is it determined?
  • A: Soil sensitivity is the ratio of the undisturbed shear strength to the remolded shear strength. It indicates how much a soil’s strength decreases upon disturbance. It is determined by performing the test twice, once on undisturbed soil and once after remolding the same sample.