ASE s.r.l. produces and commercializes innovative instrumentations designed for geotechnical and environmental monitoring. Our systems are fully automated and the data management involves the acquisition, storage and elaboration of data along with their representation through a web based platform.
Vertical Array is the instrumentation designed for the automatic monitoring of natural or artificial slopes. The tool is based on MUMS technology. It is possible to customize it according to the required resolution, frequency of measures and geometry of the slide. The array is a modular system of sensors, which are contained inside nodes (links) connected at fixed position along an aramid fibre cable. The sensors can be MEMS, electrolytic cells, piezometers, barometer and thermometers, respectively used to detect the deformations, water level, pore and atmospheric pressure and temperature variation along the vertical. The result is a near-real time 3-dimensional displacement of the slope. System installation is simple, fast and economic.
When a displacement occurs, the node changes its position in order to follow the movement of the slope or structure. After been read, every tilt sensor of the array records the different position (raw data) and sends the information to the control unit. This unit transmits the raw data to the elaboration centre, where a software processes them (ADC point) to return information about the real displacement of the node (physical units). The accelerometer gives information about the rotation of the node, referring to the constant gravity acceleration g. Like every sensor based on gravity measurement, MUMS cannot identify rigid translations. The magnetometer returns information about the direction of the displacement of each node, referring to NED reference system (North-East-Down). This sensor is provided in order to simplify the installation procedure and avoid the nuisance of maintaining the link orientation aligned during the lowering of the array in the borehole. If the monitoring requires a constant azimuth (such in very peculiar cases where the magnetic field is not stable), the elaboration software can use only the data of the 3D accelerometer and the array azimuth must be preserved through a rigid connection and alignment between links. Finally, the on-board thermometer is necessary to correct the thermal effects on the accelerometer, using the calibration values. This sensor also provides the temperature recording along the vertical.
MEMS sensors is located at the centre of each link and measures the three components of the gravitational field in its reference system, starting from an initial configuration (zero reading). When a movement arises, the variation of the different components of gravity gives back the information of the displacement. In this way, it is possible to calculate the underground rotation and the local displacement of each link and finally build a curve of cumulated displacement in the same fashion of the traditional manual inclinometers.
Each link has a segment of relevance, which is assumed as infinitely rigid, that starts from the middle point between the considered and the lower link and ends at the medium distance between the considered and the upper link. The distance between links can be varied according to specific needs. The mentioned hypothesis holds true due to the presence of the filling material, the strength of the aramid fibre cable and the small distance between nodes. Furthermore, at the top of the array there is a spring, which keep the whole system in traction through the aramid fibre cable. Considering each segment fixed at the bottom point of the segment, the displacement is located in the circle above. Every node highlights a displacement referred to the previous one. By integrating the single contributes, it is possible to obtain the cumulate deformation.
The lack of rigid connections guarantees a higher flexibility to the whole system and a consequently higher range of deformations. Due to its flexibility, Vertical Array can be installed inside old inclinometer casing, where the manual probe cannot pass due to excessive displacement, thus allowing the extension of the use of the borehole and a substantial savings of money.
The theoretical length of the array is unlimited, but there is a physical limit in the number of instruments that can be connected along a single line, which is 255 (Tilt link HR 3D V is composed by two sensors and therefore counts as two). It follows that the maximum length depends on the configuration of the array and the distance between the sensors: each array is customizable and the final length is a consequence.
The distances between nodes could vary along the chain: for example, the customer could place sensors every 50 cm near at the most critical depth, with a consequent higher accuracy and definition, and every 1 or 2 m elsewhere. Obviously, array accuracy is greater if nodes are closer.