ASTM D4403-20 PDF Download

ASTM D4403-20 is a standard practice that describes the use of extensometers in the field of rock mechanics. It covers various aspects such as the application, selection, installation, data collection, and data reduction of contact type extensometers. This standard does not cover laser or other non-contact extensometers.

The standard emphasizes the importance of selecting the appropriate extensometer based on the intended use, required measurement precision, anticipated deformation range, and installation details. It highlights that no single instrument is suitable for all applications.

The use of extensometers in tunnel instrumentation is specifically mentioned, where they are used to measure roof and sidewall movements and locate the tension arch zone surrounding the tunnel opening. Extensometers are also extensively used as safety monitoring devices in tunnels, underground cavities, potentially unstable slopes, and for monitoring the performance of rock support systems.

The standard notes that data collection for extensometers can be simple or complex, ranging from manual readings at the instrument location to electronic readings taken at the site and transmitted to a data collection and analysis center. It discusses the pros and cons of each type of data collection method, considering factors such as data quantity, safety, and real-time data analysis.

Additionally, the standard highlights the importance of accurate measurements, particularly in cases where precise measurements are required to determine the tension arch zone around a tunnel opening. It recommends the use of adjustable extensometers in such cases. The accuracy of extensometers should be determined through calibration, and the sensitivity of the transducers should also be provided.

The standard also includes general guidelines for significant digits and rounding of observed and calculated values, in accordance with Practice D6026. It emphasizes that the procedures used in the standard do not consider material variation or specific user objectives.