NR NR/GN/CIV/801 ISSUE 3 PDF

The scope of this Note is limited to the design of remedial works to embankments and soil cuttings. However, the OA could be applied to the design of a new embankment or soil cutting, and some of the advice provided herein may be pertinent to such a design.

The following types of site are unsuited to the application of the OA and are, therefore, not covered by this Note;

• rock cuttings

• slopes that may be subject to scour or flooding

• slopes whose performance is not amenable to monitoring

• slopes where there is insufficient opportunity to implement an Intervention Plan

• slopes susceptible to Sudden Failure

• sites where the application of the OA would produce an unacceptable risk to performance and/or safety

The OA is derived from, but does not implement the full potential of, the Observational Method (OM) which is described in CIRIA Report 185. This restraint is due to (a) the present lack of a simple and dependable method for calculating ground movements to determine Intervention Levels, and (b) the limited experience of defining and applying such Levels to railway earthworks.

Purpose

The purpose of this Guidance Note is to supplement NR/SP/CIV/071: Design of earthworks, earthwork remediations and geotechnical aspects of foundations for structures by providing advice on the application of the Observational Approach (OA) to the design of remedial works to embankments and soil cuttings.