What is ISO 18674‑5 - Geotechnical investigation and testing about?  
ISO 18674 is an International Standard that discusses geotechnical investigation and testing.
ISO 18674‑5 is the fifth part of the multi-series that specifies the measurement of stress changes by means of total pressure cells (TPC).
General rules of performance monitoring of the ground, of structures interacting with the ground, of geotechnical fills, and of geotechnical works are presented in ISO 18674-1.
ISO 18674‑5 is applicable to:
- Monitoring changes of the state of stress in the ground and in geo-engineered structures (e.g. in earth-fill dams or tunnel lining)
- Monitoring contact pressures at the interface between two media (e.g. earth pressure on retaining wall contact pressure at the base of a foundation)
- Checking geotechnical designs and adjustment of construction in connection with the Observational Design procedure
- Evaluating stability during or after construction
Note: ISO 18674‑5 fulfils the requirements for the performance monitoring of the ground, of structures interacting with the ground, and of geotechnical works by the means of total pressure cells as part of the geotechnical investigation and testing according to EN 1997-1[1] and EN 1997-2[2].
Who is ISO 18674‑5 - Geotechnical investigation and testing for? 
ISO 18674‑5 on Stress change measurements by TPC is useful for: 
- Geotechnical investigators and engineers
- Geotechnical consultants
- Soil testing companies
- Civil engineers   
Why should you use ISO 18674‑5 - Geotechnical investigation and testing?  
A geotechnical investigation is used to study the soil and geologic conditions of a property and to make constructive suggestions and design requirements. In this regard, TPC is a field instrument that converts stress or pressure into an electrical unit that can be measured and read.
ISO 18674-5 provides guidance on the deformation and compensation measuring methods and the monitoring features associated with each of the TPC methods. The monitoring features include:
- TPC stiffness
- Long-term stability of sensor signal
- Atmospheric pressure compensation
- Automatic data acquisition
- Logging speed
ISO 18674-5 guides you with the installation of TPC in concrete/shotcrete in a manner that ensures the position and alignment of the TPC compartments are maintained during pouring of concrete.
ISO 18674-5 provides an overview of the various types of total pressure cells in some common geoengineering applications. The classification can assist you in the instrument selection.
If you are a geotechnical investigator, adopting the recommendations of measuring stress changes by means of TPC suggested by ISO 18674-5, can help identify and mitigate induced stress in the underlying strata. Pressure cells and measuring lines shall be robust to survive the harsh environment typical for earth dam construction.
As a result, ISO 18674-5 can play a significant role in maintaining structural integrity of geotechnical or foundation engineering works.
