Settlement Monitoring

Document No:  D12#434754
 
Revision:  3
 
Date amended:  16-Jun-2014

The information below is intended to reflect the preferred practice of Main Roads Western Australia ("Main Roads"). Main Roads reserves the right to update this information at any time without notice. If you have any questions or comments please contact  The Senior Engineering Surveyor by e-mail or on (08) 9323 4667.

To the extent permitted by law, Main Roads, its employees, agents, authors and contributors are not liable for any loss resulting from any action taken or reliance made by you on the information herein displayed.
 

 

Revision Register

 

Ed/Version Number Clause Number Description of Revision Date
1 All  Guideline Developed  15-Aug-2009
1A 2.2 Link to Road Reference Marks updated. 25-May-2011
2​ ​All ​Content Cleanup ​5-Feb-2013
​3 ​Header ​Document Number Changed ​16-Jun-2014

Table of Content




1 GENERAL

This document shall be used as a guideline  for the processes involved with and the use of  the Main Roads Survey and Mapping Standard 67-08-108 "Settlement Monitoring".

Settlement Monitoring surveys are performed to determine the degree of horizontal and vertical displacement of structures, pavements and embankments over a defined period. Severe pavement damage and structural failure can be a direct result of settlement and therefore it is critical that movement outside the design tolerances are detected and measured.

The Senior Engineering Surveyor is available to assist with the development and implementation of a monitoring system to suit individual requirements.

2 MONITORING OF SETTLEMENT FOR ROAD PAVEMENTS

2.1 General

This activity is performed on road where experience has shown that pavement could be subject to excessive movement as a result of the road location, its foundations, amount of traffic and other factors which may now be different from those which the road was designed for. The need to monitor pavement may also develop with time, as factors such as climate change, water table variations, traffic density changes, soil compaction, changes in soil foundation type, all take effect. 

2.2 Survey Requirements and Datum

Unless specified, all survey work will be undertaken in accordance with Mainroads Survey and Mapping Standard 67-08-108 "Settlement Monitoring".

All work will be requested to be lodged on a Mainroads approved project grid which is based upon the Geocentric Datum of Australia 1994(GDA 94) and Australian Height Datum 1971 (AHD). A stable control network will be required to be established to Main Roads Survey and Mapping Standard 67-08-36 "Road Reference Marks" such that ongoing (year to year) use of such marks will be possible.

Appropriate survey equipment to enable vertical movements of +/- 3mm to be detected, should be utilised. Sight distances from instrument to measurement points should thus be kept to less than 130 metres. Verification of the monitoring control network(in X,Y,Z) must be undertaken before each epoch of measurements and any destroyed or inaccessible marks should be replaced if required.

Results of the survey undertaken should be presented in Excel spreadsheet format as shown at Appendix C of the Standard such that subsequent epochs can be added and movement trends observed.

3 MONITORING OF SETTLEMENT FOR STRUCTURES

3.1 General

Most high use structures require either initial or ongoing monitoring to determine whether displacements outside design tolerances are occurring. The frequency and type of monitoring will depend upon factors such as structure age, type, location(eg over water), traffic volumes and susceptibility to flooding and inundation or may result from concerns raised during routine maintenance. Thus the survey requirement for each structure will vary but the survey  methods, intent, instrumentation, data presentation will be similar. The Standard 67-08-108 "Settlement Monitoring" sets out the specific requirements for these surveys.

3.2 Survey Requirements and Datum

Unless otherwise specified all work will be requested to be lodged on a Mainroads approved project grid which is based upon the Geocentric Datum of Australia 1994(GDA 94) and Australian Height Datum 1971 (AHD).

A three tiered control network will be necessary to ensure repeatability of accuracy and coordinates for the duration of the monitoring period.  Refer to Appendix B of the Standard. Appropriate calibrated instrumentation and observation techniques must be utilised to ensure that movements of +/- 2mm in X,Y,Z can be detected and recorded. Thus sight lines will be less than 100 metres and multiple rounds of observations are to be recorded using forced centering techniques with interchangeable targets and instuments to minimise plumbing errors.

Verification of the monitoring control network(in X,Y,Z) must be undertaken before each epoch of measurements and any destroyed or inaccessible marks should be replaced if required.

Results of the survey undertaken should be presented in Excel spreadsheet format as shown at Appendix D and E of the Standard such that subsequent epochs can be added and movement trends observed.

4 PRECISION MONITORING OF STRUCTURES

In some situations there may be a requirement to monitor structure components to a higher order of accuracy than that covered by this Standard, 67-08-108 "Settlement Monitoring". Specialised instrumentation, observing techniques, and ground marks are required to ensure that repeatable accuracies of the order of +/- 1 mm or better are achieved. Before this level of monitoring is considered it will be necessary to consult with the Senior Engineering Surveyor at Mainroads WA. Such tasks would be considered on a case by case basis in conjunction with all other project requirements.