Horizontal Array

Horizontal Array

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.

 

Horizontal Array is the tool developed to monitor the subsidence and settlement of soil. System is based on MUMS technology and it is customizable according to the required resolution, frequency of readings and geometry of the site.

Sensors

Different kind of multi-parameters sensors (Link) equip the Horizontal Array:

  • Tilt Link H has a 3D MEMS (accelerometer and temperature sensor) able to identify large settlements along the instrumental reference system;
  • Tilt Link HR 3D H follows the same working principle of Tilt Link H. The main improvement refers to the 2D electrolytic cell, which permits to monitor small displacements with a 10 times higher accuracy. The presence of two different type of sensors in the same link gives redundancy to results, which is fundamental to reduce the uncertainties and have a robust interpretation of the phenomenon;
  • Baro Link is an absolute barometer which reads the atmospheric pressure;
  • Therm Link is a high accuracy thermometer, most appropriate for geothermal application when it is necessary to monitor the temperature at different positions with high precision and resolution. The sensitivity is one hundred times better than the regular thermometer contained in the other Links;
  • Analog Link is a node able to convert every kind of traditional instrument with analogic signal into a digital one.

Elaboration

When a displacement occurs, the node changes its position in order to follow the movement of the slope. 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 measure, MUMS cannot identify rigid translations. 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 along the chain.

 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 previous Link and ends at the medium distance between the considered and the following 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. Considering each segment fixed at the starting point of the segment, the displacement is located at the end of the segment. 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, Horizontal Array can be installed along the niche of detachment of the landslide or below the road axis for monitoring the subsidence phenomenon. 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 H 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. It is not necessary to place nodes at fixed distances: for example, the customer could place nodes every 50 cm at the most critical position, with a consequent higher accuracy and definition, and every 1 or 2 m elsewhere. Obviously, array accuracy is greater if nodes are closer.

 

  • Subsidence
  • Landslide