SIST EN ISO 22476-16:2025 PDF

Overview

EN ISO 22476-16:2024 - "Geotechnical investigation and testing - Field testing - Part 16: Borehole shear test" specifies the borehole shear test using the phicometer procedure (commonly called the phicometer test or PBST). The document defines equipment, execution, data acquisition and reporting for in situ determination of shear strength parameters (the in situ cohesion c and the angle of friction φ) in natural, filled or artificial soils to a testing depth of ≤ 30 m. It also sets applicability limits (typical ranges of pressuremeter limit pressure, CPT cone resistance and SPT N) and exclusions (very soft fine soils, very loose coarse soils, medium-very strong rock and soils dominated by cobbles >150 mm).

Key Topics and Requirements

• Scope and applicability: soils and fills (saturated or unsaturated); depth limit 30 m; exclusions and guidance on representativeness when outside typical ranges.
• Equipment: phicometer probe design, connection tubing, pulling rods, surface pulling/volume-control units and measurement devices (pressure, volume, force, axial displacement).
• Test procedure: pre-checks, borehole drilling and probe placement, teeth insertion, staged shearing under controlled pressure holds, and test termination. Minimum spacing and safety requirements are defined.
• Data and analysis: recording of shearing curves (PBST graphs), methods to derive φ and c, associated graphs, and examples of curve adjustment (Annexes provide determination methods).
• Quality and traceability: probe characteristics, calibration and correction procedures, accuracy and uncertainty estimates (normative annexes), and recommendations for reporting.
• Reporting: required field and test report content, test logs and documentation to ensure reproducibility and traceability.

Applications and Users

The phicometer borehole shear test is used to obtain in situ shear strength parameters for:

• Foundation design and verification (shallow and deep foundations)
• Slope stability assessments, earthworks and excavation support design
• Ground improvement validation and subsurface characterization

Primary users include:

• Geotechnical engineers and consultants
• Site investigation contractors and testing laboratories
• Design offices assessing shear strength in situ
• Researchers validating correlations with CPT, SPT and pressuremeter data

Related Standards (if applicable)

• EN ISO 22476 series (other parts cover complementary field tests)
• Common comparative tests: cone penetration test (CPT), standard penetration test (SPT) and pressuremeter testing - often used together with PBST to cross-validate in situ resistance and interpret results.

Keywords: EN ISO 22476-16:2024, borehole shear test, phicometer, PBST, geotechnical investigation, in situ shear strength, cohesion c, angle of friction φ, field testing, probe calibration.