Principle and application
Surface monuments are control points fixed on the crest and slopes of dams, on hillsides, embankments and structures. Each monument has a reference pin or a forced-centring base, set in a concrete block founded below the surface layer, so that it moves with the ground mass and not with loose surface soil. In each survey, the positions of the monuments are measured from reference pillars installed outside the zone of influence of the works.
Compared with the initial reading, the coordinates reveal the vertical and horizontal displacement of each point, with direction and rate. It is the wide-coverage instrument: inclinometers show in detail what happens at depth at a few points, while the monument network shows how the whole surface behaves.
Typical applications: crests and slopes of earth and tailings dams, unstable hillsides, embankments, waste rock piles, retaining structures and buildings next to excavations.
Installation step by step
Network design
Definition of the control sections and of the reference pillars on stable ground, outside the zone of influence of the works.
Installation
Each monument is set in a concrete block founded below the surface layer, with a stainless steel pin or forced-centring base and protection against damage.
Initial reading
Independent readings set the reference coordinates of each monument.
Surveys
High-precision total station or precise levelling, depending on the required precision, always from the same references.
Analysis
Horizontal and vertical displacement, plan vectors, rates and comparison with the alert levels of the monitoring plan.
Quality controls: reference pillars checked in every survey, instruments with valid calibration, readings in both faces with closure within tolerance, temperature and pressure correction of distance measurements and a photographic record of the condition of each monument.
According to NBR 13133
| Surveying | ABNT NBR 13133 (topographic surveying) |
|---|---|
| Dams | Brazilian Law 12,334/2010 (National Dam Safety Policy), amended by Law 14,066/2020, and ANM Resolution 95/2022 for mining dams |
| Technical reference | Silveira, J. F. A. Instrumentação e Segurança de Barragens de Terra e Enrocamento (Oficina de Textos, 2006); Dunnicliff, J. Geotechnical Instrumentation for Monitoring Field Performance (Wiley, 1993) |
| Measured quantities | Vertical and horizontal displacement (northing, easting and elevation) |
| Reading method | High-precision total station or precise levelling from stable reference pillars |
| Frequency | Set in the monitoring plan; for dams, according to the Dam Safety Plan |
| Deliverable | Network sketch and as-built, coordinate sheets, displacement and rate plots, plan vectors and report |
Carried out to the same QA/QC, HSE and site standards as every Damasco Penna service, described in Quality and field operations.
Frequently asked questions about Surface Monuments
What are surface monuments used for?
To measure surface displacement of dams, slopes, embankments and structures. The series of readings shows whether each point is moving, in which direction and how fast.
How precise are the readings?
Millimetric. The method, high-precision total station or precise levelling, is chosen according to the precision required in the monitoring plan and the distance to the references.
Does a surface monument replace an inclinometer?
No. The monument shows surface movement and the inclinometer shows movement at depth and locates the shear surface. A good monitoring plan combines both.
Can readings be automated?
Yes. With prisms on the monuments and a robotic total station, readings can be automatic and continuous, with alarms. The solution is defined according to the risk of the structure.
Related services
Surface Monuments for your project
Tell us about the project and we will put together the monitoring plan and the quote.