11 Earthworks asset management
Any earthworks should be managed by an appropriate asset management system to ensure that acceptable performance is achieved and that the earthworks do not present a risk to users. The nature of the management system may vary to reflect the use of the earthworks and the risks they pose.
The key texts on asset management to which reference should be made are CIRIA C591  and CIRIA C592 . The recommendations of these CIRIA documents are relevant to all owners of earthworks who should manage their assets in accordance with these recommendations and link as appropriate with adjacent land users.
COMMENTARY ON 11.1
Since the 1990s the large infrastructure operators (road, rail, waterways, flood defences) have implemented earthworks asset management systems, and it was these groups that were actively involved in the preparation of the key documents on the asset management of infrastructure earthworks,
Given the significance of the CIRIA documents to this clause, Table 11 is provided to aid cross reference. This clause gives commentary and recommendations on the subject, but the reader is advised to see CIRIA documents for more detail.
|BS 6031 subclause||Aspect||C591, cuttings||C592, embankments|
|11.2||Asset management||2.3 to 2.6||2.3, 2.4,2.6|
|11.3||Inspection||4.1||4.1 to 4.6, Appendix A3|
|11.4||Assessment||4.2 to 4.4||4.7 to 4.10|
|11.7||Maintenance issues||5.8, 7.5 and 7.6||5.8, 7.5, 7.6, Appendix A6|
|11.8||Renewal works||5 and 6||5 and 6|
11.2 Asset management systems
An asset management system should include:
- a) asset catalogues;
- b) specification of performance and required duty;
- c) management and business strategies/plans;
- d) risk registers;
- e) consideration of whole life costs.
For asset management to be successful an accurate catalogue of assets should be established so that all subsequent activities can be planned and correctly referenced.
NOTE GIS database systems with a map-based front end have proved to be a valuable tool to assist in the task of delivering asset management. Systems are set up to suit the asset type and specific owner's requirements such as risk issues that are to be managed.
For an earthworks asset management system to be successfully delivered it is necessary to develop an appropriate earthworks inspection system that should then be routinely implemented. The inspection approach varies between earthwork owners: in all cases it should involve an observation and recording of the site conditions at the time of the inspection. The following factors should be considered in developing an inspection regime:
- inspection frequency;
- types (cyclical or ad hoc);
- data collection techniques;
The frequency of cyclical inspections should be set considering the age and condition of the infrastructure together with the likelihood, mode, consequence and remaining time to failure.
NOTE In all inspection systems there will be a trade off between the cost of undertaking the inspections (i.e. the level of detail required) and the benefit to be gained for managing the asset. The concept of "touch distance" is valuable, where inspections are undertaken within touching distance of the asset the accuracy of the data collected will be greater; however, in some cases data capture at a distance can form a valuable part of an asset management system.
Where touch distance inspections are not carried out the asset maintainer should manage the risks of potentially missing information. The asset maintainer should select a system that suits their requirements and ensures that the data collected is adequately assessed.
Where possible a record should be made of the drainage system as an integral part of the earthworks inspection and assessment. The inspection should also establish the presence and overall condition of any additional stabilizing structures (retaining walls, soil nails etc.) within the earthwork. Some of the stabilizing structures might require inspection by other disciplines and so harmonized inspection programmes should be considered.
The inspection should not only focus on the specific asset being inspected but should be watchful of nearby activities that may adversely affect the asset. The information collected from inspections should be used to identify faults and monitor asset condition and degradation rate.
The assessment process should involve viewing one or more inspection records, considering the significance of the data and assessing the appropriate engineering response.
Assessments should normally be carried out on earthworks where little information is available on the original construction, but they may be applicable to more modern structures where conditions might have changed, e.g. groundwater profiles. They may also be applicable where assets are to be modified or subject to revised usage.
NOTE Geophysical techniques can have benefit in profiling long linear structures or in establishing the scale of damage from burrowing animals. Further information may be obtained from CIRIA C591  and C592 .
11.5 Fault mitigation
If instability or other loss of functionality occurs, the following options may be adopted in increasing order of impact:
- a) increased inspection;
- b) monitoring;
- c) routine maintenance, e.g. unblock drains; that is, minor works (no need for design normally as the works are standard/repeatable activities and there is no change to the earthwork proposed); this is often referred to as "preventative maintenance" as investment in this form of maintenance ought to prevent the onset of slope instability; these activities are ideally undertaken by the maintainer as part of a programme of routine maintenance;
- d) service restriction, either while mitigation is put in place or stabilization is undertaken;
- e) remedial works if significant intervention like an earthworks fix is needed (e.g. stabilization of an embankment); which means a return to the design stage, as illustrated in Figure 1; at this point a designer is needed as the works will be one-off activity designed to suit the particular site; these activities are often referred to as "reactive" (or proactive) maintenance;
- f) withdrawal from service.
11.6 Monitoring of existing earthworks
COMMENTARY ON 11.6
The purpose of monitoring earthworks (see Clause 6 for detail) includes the following:
- a) where movements have occurred, gain design information on the depth area and lateral extent;
- b) determine the rate of movement and establish if it is constant, accelerating or decelerating;
- c) establish in-situ water pressures and any variation over time;
- d) mitigation of risk until repairs are implemented;
- e) to establish the effects of adjacent construction of modification to earthworks both during the construction stage, and in the long term;
- f) obtain quantitative performance data where analytical assessment is believe to have produced conservative results; and
- g) confirm design assumptions.
The designer of the monitoring system should define these aspects in advance of implementation of the scheme:
- 1) objectives;
- 2) techniques;
- 3) required accuracy;
- 4) frequency;
- 5) trigger levels;
- 6) data collection and reporting; and
- 7) action plans.
NOTE There is a vast range of instrumentation available and further guidance can be obtained from . Recent developments in this field include web based, cable free or fibre optic systems which offer remote, real time monitoring that has the potential to be integrated to automatic alert alarms. Owing to the rate of technological development in this field discussion should always be held with specialist instrument manufacturers and installers.
In establishing trigger levels, the likely magnitude of normal background movements should be considered. (For example, seasonal vertical movements of up to 50 mm have been recorded on some London Underground embankments due to effects of vegetation on high plasticity clay.) Therefore the monitoring system should be put in place sufficiently in advance of control periods so that the range and pattern of background movements can be established.
For new or modified construction, monitoring can have a role to play in finalizing design through either the approach recommended in BS EN 1997-1:2004 (see 7.2.4 of this standard) or the observational approach itself (see ).