KO Consolidation Apparatus

Model BTU-STC-KO

Description

This equipment is a KO consolidation apparatus, modelBTU-STC-KO, used to determine thecoefficient of earth pressure at rest (K₀)of soil specimens with a diameter of Ø61.8 mm. The lateral pressure under no lateral strain conditions is measured using a pore pressure meter (or lateral pressure sensor). It is mainly used to study the compression characteristics of soil under lateral restraint, providing K₀ values for settlement calculations and earth pressure analysis.

System overview: The KO consolidation apparatus is used to determine the coefficient of earth pressure at rest for Ø61.8 mm soil specimens. The lateral pressure can be measured by a pore pressure meter.

Test Standards (International)

• ASTM D2435(One‑dimensional consolidation – K₀ conditions can be derived)
• ASTM D4186(CRS consolidation – K₀ measurement possible)
• ASTM D4767(Triaxial compression – K₀ consolidation stage)
• ISO 17892‑5(Consolidation test)
• BS 1377‑6(Consolidation test)
• Chinese GB/T 50123‑2019(Standard for soil test methods – includes K₀ test)

The equipment can meet the requirements of these standards for lateral pressure measurement, axial loading, displacement measurement, etc.

Specification

Note: The screenshot does not specify maximum axial pressure, loading method (lever/servo), lateral pressure sensor range, accuracy, etc. – refer to the product manual.

Detail

• K₀ consolidation principle– Under fully lateral restraint (zero lateral strain), axial pressure is applied to the specimen and the lateral pressure(σ h)is measured. The coefficient of earth pressure at rest is K₀ = σ_h / σ_v.
• Specimen size– Diameter 61.8 mm, height 40 mm (height‑to‑diameter ratio ≈0.65, common for K₀ consolidation tests).
• Axial displacement measurement– Range 12.7 mm, resolution 0.01 mm (10 μm), allowing precise compression recording.
• Pressure cell seal– No leakage at rated pressure, volume change <0.20 ml (very small volumetric change, ensuring lateral rigidity).
• Lateral pressure measurement– Using a pore pressure meter (connected to a lateral pressure sensor or liquid pressure sensor).
• Suitable materials– Fine‑grained soils (clay, silty clay), commonly used for saturated soil K₀ determination.

Application

• Foundation settlement calculation– K₀ values are used for settlement estimation of normally consolidated and overconsolidated soils (e.g., K₀ consolidation test method).
• Earth pressure calculation– K₀ is needed for calculating earth pressure at rest on retaining walls, basement walls, etc.
• Constitutive model parameters– Provides K₀ parameter for models such as Modified Cam Clay.
• Laboratory testing– Research institutions and university soil mechanics laboratories.
• Numerical model validation– Provides laboratory K₀ values for calibrating finite element models.

Advantages

• Specialised K₀ consolidation– Dedicated design for measuring the coefficient of earth pressure at rest, compact structure.
• High‑precision displacement measurement– 0.01 mm resolution, meeting consolidation deformation accuracy requirements.
• Good sealing– Pressure cell volume change <0.20 ml, ensuring lateral restraint (approximate zero lateral strain).
• Easy operation– Lateral pressure can be measured directly with a pore pressure meter.
• Standard specimen size– Ø61.8 mm is a common size, facilitating sample preparation and comparison.
• Compatibility– Can be used with various loading systems (lever, servo, etc., to be supplied separately).

What To Choose

Select this equipment or compare with other configurations based on testing requirements:

Process Flow

Example:Standard K₀ consolidation test (step loading, saturated clay)

• Specimen preparation
  • Cut undisturbed or remoulded clay specimen using a Ø61.8×40 mm ring.
  • Saturate (vacuum or back pressure saturation), measure initial water content and density.

• Specimen installation
  • Place the specimen into the pressure cell of the K₀ consolidometer, with porous stones above and below.
  • Install the axial displacement sensor (zero it).
  • Connect the lateral pressure measurement system (pore pressure meter or lateral pressure sensor) and de‑air the pressure cell.
  • Position the pressure cell in the loading frame (e.g., a separate consolidometer main frame).

• Apply initial seating pressure
  • Apply a small axial pressure (e.g., 5 kPa) and record initial axial displacement and lateral pressure.

• Set test parameters
  • Define the load sequence (e.g., 25, 50, 100, 200, 400, 800 kPa).
  • Duration for each load step is typically 24 hours or until consolidation is stable (displacement change <0.01 mm per hour).
  • Set data acquisition intervals (e.g., 0.1, 1, 10, 60 minutes).

• Start the test
  • Apply the first axial load step.
  • Record axial displacement and lateral pressure in real time.
  • At each load step, after axial displacement stabilises, record the lateral pressure.

• Calculate K₀
  • For each load step, K₀ = lateral pressure(σh)/axial pressure(σv).
  • Plot K₀ vs. σ_v curve.

• End and disassembly
  • After the test, unload, remove the specimen.
  • Clean the pressure cell and sensors.

• Data processing
  • Calculate K₀ values for each load step; take the average or analyse the trend.
  • For normally consolidated soils, K₀ ≈ 1 – sin φ′ (Jaky’s formula) can be used for verification.
  • Generate a test report.

If the equipment is paired with aservo loading system, it can perform CRS or automatic step loading with real‑time lateral pressure acquisition, improving efficiency.

Summary:The BTU-STC-KO is a dedicated K₀ consolidation apparatus for determining the coefficient of earth pressure at rest of Ø61.8×40 mm soil specimens. It features an axial displacement resolution of 0.01 mm and a well‑sealed pressure cell (volume change <0.20 ml). Lateral pressure is measured via a pore pressure meter or lateral pressure sensor. It is suitable for foundation settlement calculations, earth pressure analysis, and constitutive model parameter determination. Note that the loading system (e.g., a consolidometer load frame) must be supplied separately; if high‑precision automatic loading is needed, a servo system can be added. The apparatus is designed for fine‑grained soils only, with a fixed specimen size.

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