Xdisp – How should I create a set of sub-surface ground movement data to describe the movement around a retained cut or embedded wall excavation?
Xdisp includes a facility to define or calculate sub-surface displacements around retained cuts. The most appropriate use of the program is by users carrying out site specific analysis of a 2 dimensional plane strain cross section of the retained cut excavation and to cut and paste the results directly into Xdisps Ground Movement Curves’ data. Commonly this will be carried out using a finite element analysis. The user is required to enter data from the analysis in the format defined below.
Xdisp then fits a curve to this data by a least squares fit to find a 2D (surface) polynomial function. The program then uses that function to interpolate between input data points to allow displacements to be calculated at any point behind the retaining wall. The program displays the R2 coefficient that indicates the goodness of fit to the actual data in both the x and y directions.
As an example of sub-surface displacements, data is supplied in a sample file with Xdisp. If a typical installation has been performed, then that file will be found at:
C:\Program Files\Oasys\Xdisp xxx\Samples\Sample sub-surface ground movement data.xdd
(where “xxx” is the version of the program).
That data has been obtained from a finite element analysis. Details of the FE model are given in the attachment (Appendix A). Comparisons of the data calculated from the model with sub surface displacements of a deep cast iron tunnel adjacent to the excavation may be found in Devriendt et al (2010).
- Devriendt M, Doughty L, Morrison P, Pillai A (2010). Displacement of cast iron tunnels arising from a deep basement excavation in central London. Accepted for publication in ICE Geotechnical Engineering journal 2010 Geotechnics of tunnelling special issue.