Friction & End Bearing Load Test (Caisson Pile)
Plate Load Testing (PLT) is a critical in-situ investigation performed to determine the ultimate bearing capacity and settlement characteristics of soil. By simulating real-world foundation conditions, the test provides empirical data on how the ground will behave under a specific structural load.
While primarily utilized for shallow foundations, PLT is also an essential tool for:
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Verifying subgrade reactions for floor slabs and pavements.
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Assessing the end-bearing capacity of deep foundation systems (such as caissons or large-diameter piles).
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Evaluating the stiffness of stabilized or improved ground.
Friction Load Test (Test Ring)
This test isolates a selected concrete ring within the caisson shaft to evaluate the mobilization of shaft friction along the pile–soil interface under controlled axial loading conditions.
Mechanism
Hydraulic jacks are arranged uniformly on the test ring (top or bottom) to apply axial load, using the completed caisson structure as a reaction system for stability and control.
Instrumentation
LVDTs are installed around the ring to measure axial displacement. All readings are recorded through an automated data acquisition system for accuracy and consistency.
Test Configuration
The number and capacity of hydraulic jacks and LVDTs are determined based on the required test load and caisson diameter to ensure uniform load distribution and reliable measurement.
Purpose
The test quantifies the load–movement response of the shaft segment, enabling verification of design assumptions related to skin friction and pile performance in specific soil strata.
End Bearing (Plate Load) Test at Toe
This test evaluates the bearing capacity and deformation characteristics of the founding layer at the base of the caisson, in accordance with ASTM D1194 and BS 1377 (Part 9).
Mechanism
A steel plate is positioned at the caisson base, and load is applied through a hydraulic jack reacting against a deadweight system or internal reaction arrangement.
Instrumentation
LVDTs are positioned around the plate to measure vertical settlement during incremental loading. All readings are recorded through an automated data acquisition system.
Test Capacity
The test setup is designed to achieve loads typically up to 2–3 times the design bearing capacity, based on project requirements and specified loading criteria.
Analysis
Load–settlement behaviour is monitored at each increment to assess the performance of the founding stratum and confirm that the pile base can sustain the design load without excessive settlement.
