What is DMS?
DMS® (acronym of Differential Monitoring of Stability) is a differential multiparametric monitoring system of the stability of soils, rocks and structures; this particularly innovative system makes it possible to study continuously, automatically and in real time the geotechnical behavior of the soil, rock or structure in 2 - 3 dimensions, and is intended for monitoring stability and settlements also for alert purposes.
How is DMS made?
The DMS® system used in landslide monitoring consists of a modular column, formed by a sequence of sensorized rigid tubular elements connected each other with flexible joints, installed in the ground inside a borehole. The column, which is a sort of "backbone" of the soil/rock mass and which is more than 200 m long, is able to copy the deformations while providing information on piezometry, temperature, acceleration, ...
As regards the monitoring of structures and geotechnical engineering works, it is possible to adopt a particular type of DMS® column to be installed in inclined boreholes (from horizontal to vertical) or on any variable surface. The system is completed by a remote control and data tele-trasmission unit installed on site and by a software suite for data management and processing.
How data are recorded by DMS?
Each module, cable connected with the RS485 digital interface, communicates with the control and tele-transmission unit installed on the surface/top. The control unit queries all the sensors installed in the column, performing a reading/minute and comparing the data recorded with alert thresholds values that user presets.
In case of exceeding alarm thresholds, the control unit sends a notice via sms/direct call to preset telephone numbers of the staff on duty, reporting the id of the column involved, the module or modules (depth) and the alert level. If the threshold value will be not reached, the data of each sensor are kept in memory for a programmable time interval, generally 1 hour, then the value is mediated and saved as a record. Then, at a pre-defined times, data are transferred to the server of the monitoring room.
This process allows to filter potential noise improving data acquisition and limiting false alarms.
How can you manage the data?
The DMS® system is completed by a software suite specifically designed not only for data acquisition (Geomaster and DMS Guardian software) but also for data graphic processing (DMS EW software).
The last one allows to process data automatically through differential and cumulative representation of the whole column in terms of north and east components of movements and total displacement (vertical diagrams) and direction (polar diagram). It also allows to analyze the data time history of all recorded parameters (displacement, velocity, acceleration, groundwater level/s, …) for individual sensors or portions of column interested in specific kinematics and to compare data with alert thresholds.
So-processed data can be easily used for calibration and verification of stability models, as well as being a valid and effective support for technicians during the decision-making phases of the alert.
It is possible to share data also with consultants in a fast and practical way without direct access to the control unit?
The data acquisition software (DMS Guardian), which is installed in monitoring room server, downloads data from control unit in pre-established time interval (normally 1 time per day) and sends the same data via ftp to an internet accessible server (access restricted and protected obviously). Qualified technicians and consultants can access directly to data through pc or by usb key, in which the software DMS EW Client is installed, observe and process the parameters detected, process graphically the columns, variations over time of data of one or more sensors, elaborate graphics of displacement, velocity or acceleration, etc..
This solution is particularly effective because it does not require the presence of staff on duty inside the monitoring room/center and allows more people, at the same time, to share and analyze data recorded.
The same client solution is also suitable specially for rented systems, when the monitoring period is short and it is not necessary to buy hardware and the software suite or to train monitoring technicians. In this case CSG provides a full service management of the system with automatic data acquisition from the company monitoring room.
Is DMS strong enough?
The system has a very strong mechanical construction with rigid stainless steel elements and flexible joints in special armed rubber (tensile strenght according to type from 20 to 50 kN) able to withstand pressure, shearing strain and high deformations and to protect power and data transmission cables that pass inside. The robustness of the instrumentation has been tested in some landslide applications where the system has remained functional also following metric displacements of the ground.
The tensile strength of the system was tested by the official Laboratory of the Polytechnic of Turin - Department of Structural, Building and Geotechnical Engineering.
Until when is it possible to extract the DMS column from the ground?
There is no unequivocal threshold of displacement beyond which extraction is prevented, because it depends on many factors related to the type of deformation (if the sliding plane is net or not), to the depth, to the type of pipe installed and to the position that assumes the column with respect to the main deformation (length of the column below the cutting plane).
In practice it is noted that the interest in continuously monitoring a paroxysmal landslide phase becomes a priority compared to the protection of the column and, therefore, normally in these cases the system is maintained in the landslide body until it is sheared. Then the sheared column can be recovered for the part above the sliding plane.
Where DMS is produced?
The instrumentation is enginered and produced in Italy by C.S.G. company with headquarters in Ricaldone (AL).
C.S.G. produces under own patents and DMS trademark and ensures the distribution and installation of the system, up to the eventual remote management of data through its own monitoring room.