AZA 0912 LABORATORY CALIFORNIA BEARING RATIO APPARATUS, MOTORISED

Description

AZA 0912 Laboratory California Bearing Ratio Apparatus, Motorised: Consistent Soil Strength Testing by Azalab

The Azalab AZA 0912 Laboratory California Bearing Ratio Apparatus, Motorised, is a cornerstone instrument in geotechnical and highway engineering laboratories. It is specifically designed for the accurate determination of the California Bearing Ratio (CBR) value of compacted or undisturbed soil specimens, which is a critical parameter for the design of flexible pavements in roads, highways, and airport runways. Unlike purely manual systems, the motorized operation of the AZA 0912 ensures a constant and precise rate of penetration, eliminating operator variability and leading to more consistent and reliable test results—a key requirement for standard compliance and reliable pavement design in India.

The Importance of Motorised Operation in Laboratory CBR Testing

The California Bearing Ratio (CBR) test is an empirical penetration test that measures the resistance of a soil to penetration by a standard plunger. The CBR value is expressed as a percentage of the standard load sustained by a crushed rock. For accurate and comparable results, standards (like IS 2720 Part 16 and ASTM D1883) strictly specify a constant penetration rate, typically 1.25 mm per minute.

While manual, hand-operated CBR apparatus exist, maintaining this constant rate of penetration throughout the test can be challenging and prone to human error, leading to variability in results. The AZA 0912 Laboratory California Bearing Ratio Apparatus, Motorised, addresses this by:

• Ensuring Consistent Penetration Rate: The integrated electric motor and gear system precisely controls the vertical movement of the loading ram, guaranteeing the standard penetration rate. This consistency is vital for accurate load-penetration curve development.
• Reducing Operator Fatigue: Automation of the loading process frees the operator from the tedious task of continuously cranking, allowing them to focus on accurate reading of dial gauges at specified intervals.
• Improving Reproducibility: By standardizing the critical loading rate, the motorized system inherently improves the reproducibility and reliability of the CBR test results, making them more dependable for critical engineering designs.

Working Principle of the AZA 0912 Motorised CBR Apparatus

The operation of the AZA 0912 involves a precise sequence to obtain the CBR value:

1. Sample Preparation: A soil specimen is compacted into a standard CBR mould (150 mm diameter) to a specified density and moisture content, representing field conditions, or an undisturbed sample is placed. Surcharge weights are placed on top of the sample, simulating the weight of the pavement structure.
2. Setup: The CBR mould with the prepared sample and surcharge weights is placed on the base of the motorized loading frame. A penetration piston (50 mm diameter) is seated on the soil surface.
3. Load and Penetration Measurement: A calibrated proving ring is positioned between the loading ram and the penetration piston to measure the resistance offered by the soil. A dial gauge is mounted to the proving ring to indicate its deformation, which correlates to the load. Simultaneously, another dial gauge is mounted on a tripod to measure the penetration depth of the piston into the soil.
4. Motorised Penetration: The electric motor is switched on, which drives the loading ram downwards, forcing the penetration piston into the soil at the constant rate of 1.25 mm per minute.
5. Manual Data Recording: At specific penetration intervals (e.g., 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 4.0 mm, 5.0 mm, 7.5 mm, 10.0 mm, 12.5 mm), the corresponding readings from both the proving ring dial gauge (for load) and the penetration dial gauge are manually recorded.
6. Data Analysis: The recorded load-penetration data is then plotted on a graph. Any initial concavity in the curve is corrected, and the loads corresponding to 2.5 mm and 5.0 mm penetration are determined. These loads are then used to calculate the CBR value.

Key Features of the Azalab AZA 0912 Laboratory California Bearing Ratio Apparatus, Motorised

The AZA 0912 is meticulously designed with high-quality components to ensure robust performance and accurate results:

• Heavy-Duty Motorized Loading Frame: A robust, precision-engineered frame with a powerful electric motor and reduction gearbox ensures a constant penetration rate of 1.25 mm/minute, as specified by standards. Operates on standard 230V AC, 50Hz single-phase power.
• Calibrated Proving Ring: Supplied with a highly accurate proving ring (e.g., 50 kN or 100 kN capacity, with an integral boss) and a high-resolution dial gauge (e.g., 0.002 mm least count). Calibration certificates are provided.
• Precision Penetration Dial Gauge: A standard dial gauge (e.g., 25 mm travel, 0.01 mm least count) with a sturdy tripod attachment for precise measurement of penetration depth.
• Standard CBR Moulds: Compatible with and typically supplied as a set with CBR moulds (150 mm internal diameter x 175 mm height) with a perforated base plate and collar, ensuring compliance with test standards.
• Spacer Disc & Surcharge Weights: Includes a standard spacer disc (148 mm diameter x 47.7 mm high) and a set of slotted surcharge weights (e.g., 2.5 kg, 5 kg, 10 kg) for simulating pavement load.
• Penetration Piston: A standard 50 mm diameter penetration piston made of hardened steel.
• Robust Construction: All components are constructed from high-quality, durable materials suitable for continuous laboratory use.
• Safety Features: Equipped with limit switches to prevent over-travel and overload protection mechanisms.

Applications and Standards Compliance in the Indian Context: The Azalab AZA 0912 Laboratory California Bearing Ratio Apparatus, Motorised, is indispensable for:

• Pavement Design: Providing essential CBR values for the structural design of flexible pavements for roads, highways, and airport runways.
• Quality Control: Ensuring that subgrade, sub-base, and base course materials used in construction meet specified strength requirements.
• Soil Stabilization: Evaluating the effectiveness of various soil stabilization techniques by comparing CBR values before and after treatment.
• Geotechnical Research: Studying the strength characteristics of various compacted and undisturbed soil types under controlled laboratory conditions.

The apparatus is manufactured and tested to fully comply with the leading national and international standards, ensuring the reliability and global acceptance of test results:

• IS 2720 (Part 16):1987 (Reaffirmed 2021): Indian Standard Methods of Test for Soils – Laboratory Determination of California Bearing Ratio.
• ASTM D1883: Standard Test Method for California Bearing Ratio (CBR) of Laboratory-Compacted Soils.
• BS 1377-4: Methods of test for soils for civil engineering purposes – Compaction and CBR tests.

Azalab‘s Commitment to Quality and Reliable Testing: Azalab is dedicated to providing high-quality, precise laboratory equipment that supports the robust infrastructure development in India. The AZA 0912 Laboratory California Bearing Ratio Apparatus, Motorised, reflects our commitment to accuracy, consistency, and durability. By offering a reliable system for a critical soil mechanics test, we empower engineers and technicians to obtain dependable data, leading to the design and construction of safer and more durable pavements. Our equipment is built to the highest quality standards and is backed by comprehensive technical assistance and reliable after-sales service.

Specifications:

• Model: AZA 0912
• Product Type: Laboratory California Bearing Ratio (CBR) Apparatus, Motorised
• Application: Laboratory determination of CBR value for compacted or undisturbed soil specimens.
• Loading Frame:
  • Type: Motorised, Bench-top/Floor-standing.
  • Capacity: Typically 50 kN (5000 kgf) or 100 kN (10000 kgf).
  • Penetration Speed: Fixed at 1.25 mm/minute (as per standards).
  • Motor: Electric motor with precision gearbox.
  • Power Supply: 230V AC, 50 Hz, Single Phase (Standard Indian supply).
• Load Measurement:
  • Device: Calibrated Proving Ring (with integral boss).
  • Capacity: Typically 50 KN (5000 kgf) or 100 KN (10000 kgf).
  • Readout: Dial Gauge (e.g., 0.002 mm least count).
• Penetration Measurement:
  • Device: Dial Gauge with Tripod.
  • Range: 25 mm travel.
  • Least Count: 0.01 mm.
• Penetration Piston: 50 mm diameter, hardened steel.
• CBR Moulds:
  • Inner Diameter: 150 mm.
  • Height: 175 mm (with collar).
  • Base Plate: Perforated.
  • Quantity: Typically 2 or 3 moulds included in the set.
• Spacer Disc: 148 mm diameter x 47.7 mm height.
• Surcharge Weights:
  • Type: Slotted.
  • Set: Various weights (e.g., 2.5 kg, 5 kg, 10 kg).
• Cutting Collar: For levelling specimens.
• Swell Plate (Perforated): For swell test (if applicable, often included with CBR set for saturation/swell test).
• Construction: Robust and durable steel frame and components, finished with corrosion-resistant paint.
• Standards Compliance: IS 2720 (Part 16):1987 (Reaffirmed 2021), ASTM D1883, BS 1377-4.
• Country of Origin: Made in India.

FREQUENTLY ASKED QUESTIONS (FAQ):

• Q: What is the main benefit of a motorised CBR apparatus over a hand-operated one?
  • A: The motorized operation ensures a constant and precise penetration rate (1.25 mm/min), which is critical for consistent and reproducible CBR test results, reducing operator variability.
• Q: What specific data is measured during the test using this apparatus?
  • A: The apparatus measures the load (force) required to penetrate the soil at specific depths (e.g., 2.5 mm and 5.0 mm), using a proving ring and dial gauges.
• Q: Is this apparatus fully automatic for data recording?
  • A: No, while the penetration rate is motorized, the load and penetration readings are typically taken manually from dial gauges. A fully automatic version (e.g., AZA 0913) would use load cells and LVDTs connected to a data acquisition system.
• Q: What types of soil samples can be tested?
  • A: It is used for both laboratory-compacted soil specimens and undisturbed soil samples within standard CBR moulds.
• Q: What standards does this equipment comply with?
  • A: It fully complies with IS 2720 (Part 16), ASTM D1883, and BS 1377-4.
• Q: What are the main components included with the AZA 0912?
  • A: It typically includes a motorized loading frame, a calibrated proving ring with dial gauge, a penetration dial gauge, a penetration piston, CBR moulds, spacer disc, and surcharge weights.
• Q: Why is the CBR test important for construction?
  • A: The CBR test is crucial for pavement design, as it helps determine the required thickness of flexible pavement layers based on the bearing capacity of the subgrade and base course materials.