- Who we are, what are we doing?
- ASE Ltd (Advanced Slope Engineering Ltd) is a Spin Off of the University of Parma, Dept. of Civil and Environmental Engineering and Architecture, that was founded in order to produce and sell new technologies for the automated monitoring of subsoil deformation. The key instrument that is engineered and produced by ASE Ltd is the MUMS (Modular Underground Monitoring System) which is a Patent proprietary technology.
- Original Idea
- The instrument is born with the idea of replacing the standard inclinometers by locating appropriate nodes, having known distances from each other along an aramitic rope of the desired length. Each node is able to measure its local orientation form the vertical (gravitational acceleration), by means of a micromechanical 3D digital linear acceleration sensor (MEMS) and a 3D digital magnetic sensor which enables to determine the heading (azimuth) of each node related to the magnetic North. In addition, each node is equipped with a digital thermocouple which controls any eventual temperature variation and allows for measurements corrections. These elements eliminate the uncertainties and the errors due to spiraling and to system assembly imprecisions.
- Accuracy and Calibration
- The accuracy of the measurements is related to the appropriate calibration of each node (carried out at our production laboratory) and to the site specific constants. This measurement is tied to the local orientation of the Earth’s magnetic field, which is accurately modeled by several geomagnetic models (i.e. EMM2010, HDGM, etc.) compiled from satellite, marine, aeromagnetic and ground magnetic surveys around the globe. These models are constantly updated and already in use by the directional drillers as a natural reference frame to orient deep drillings. The calibration procedure, which is carried out before the product leaves the production laboratory, reduces all the instrumental errors due to the sensor technology and their assembly but it is not able to correct (although it recognizes their presence) errors due to local magnetic anomalies that may be present. However this correction can be done once the vertical axis direction is known for accelerometer measurement, since the node is supposed to be still at the time of each reading and the only acceleration measured is the gravitational one.
- Communication and data transfer
- With the increased complexity of each single node, the amount of data to be transferred along the MUMS system increases as well, so an innovative connecting system has been developed. It uses a single cable (4 poles) for the serial querying of each node and data recording. The new apparatus requires an installation procedure that is analogous to the one used for a standard inclinometer, although it has a smaller diameter (nodes are 2.7 cm in diameter).
- Customized Production process
- Each chain is pre-assembled in laboratory during the production processes, according to the specific requirements. The chain is, then, shipped on a reel or in a box, ready to be installed. The apparatus can easily be introduced in small boreholes and/or inside old inclinometer casings that are partially broken (and unusable) due to previous landslide movements. The average lifespan of a standard inclinometer, in fact, ends up with a recorded horizontal displacement of 8 to 15 cm, depending upon the dimension of the shearing surface/band. During the laboratory pre-assembly, all the nodes are installed, connected, tested for a correct response and then moulded along an aramitic cable at a known distance from each other (usually 0.5 m).
- Innovation and technological advances
- The new conception MUMS instrumentation is based on principles that are analogous to those of the standard inclinometer, with few substantial differences:
- It is formed by a series of nodes, which measure and record the absolute orientation of the MUMS axis related to the vertical and to the Earth’s magnetic north; the orientation of the nodes is determined using the flight convention attitude (Tait-Bryan angles), appropriately modified to treat our problem;
- The nodes will remain inside the ground for the whole duration of the monitoring and will be lost at the end of it (unless they need to be recovered because of environmental reasons using a coring technique); they are all connected along a single waterproof and durable 4 poles cable with a proprietary data logger that is installed at the top of the borehole;
- The distance between nodes can be chosen in relation with the precision required for the final output of displacement and, if deemed appropriate, can be varied along the MUMS axis (i.e. to monitor with higher detail the expected shearing surface/band);
- In addition to the determination of the 3D shape and configuration of the MUMS (and therefore of the underground soils/rock surrounding it), the system is also able to provide other measurements, such as pore pressure, temperature and other physical entities of interest, when equipped with appropriate nodes;
- The instrument readings and their recordings are carried out automatically by means of an electronic control unit/data logger which is installed at the surface, preferably at the top of the borehole.
- The MUMS control unit (ASE801) is powered by a battery or, if the local condition are permitting it, by regular electric power; it is managed either locally, using a pre-programmed configuration transferred to the unit by insertion of an SD card, or remotely by GSM, GPRS or radio signals. The duration of a single complete readout of the MUMS depends on his length and the amount of sensors installed on it; the average readout time of each node is variable between 0.2 and 0.6 seconds. Therefore, the readout time of a 20 m long MUMS chain having one node per meter is variable between 4 and 12 seconds. The time interval between single complete readouts of the chain can be chosen by the operator based on the particular needs (expected velocity of the landslide, available memory, data recovery frequency, reason of the monitoring, etc.). It can vary in a range starting from the single complete readout time of the MUMS and ending up to 9999 seconds. Each proprietary data logger can control up to 250 nodes installed along one or two chains. An eye on the future of monitoring for the safety of people and environment.
- Research and upcoming developments
- New upcoming developments of the MUMS systems are:
- Application to control the mechanical behavior and performance of foundations and/or soil or rock supporting structures such as piles and diaphragm walls;
- Application to the automated control of the stability of river embankments, railroad embankments or other infrastructures supports;
- Monitoring of the temperature variation of warm water natural reservoirs and accurate monitoring of the groundwater temperature variation induced by very low enthalpy residential energy systems;
- Integration of high precision 2-axial electrolytic level to increase the angle resolution around specific angles (± 20°);
- Development of new data loggers with web and ftp server capabilities, potentially integrating Smart Mesh WiFi technology, which enables the communication of several dataloggers (or sensors) located at various distances from the connected data logger.
- Segalini A., Carini C. (2011) - Underground Landslide Displacement Monitoring: A new MEMS based device
Proceedings of the Second World Landslide Forum - 3-7/10/2011 - Rome
- Segalini A., Chiapponi L. e Carini C. (2013) - Evaluation of a novel inclinometer device based on MEMS technology through comparison with traditional inclinometers in landslide applications.
Geophysical Research Abstracts. Vol. 15, EGU2013-1993, 2013 EGU General Assembly 2013
- Segalini A., Chiapponi L., Pastarini B. and Carini C. (2014) - Automated inclinometer monitoring based on MEMS technology: applications and verifications
Accepted in the Proceedings of the Third World Landslide Forum - 2-6 June 2014, Beijing - China
- Segalini A., Chiapponi L. and Pastarini B. (2014) - Application of Modular Underground Monitoring System (MUMS) to landslides monitoring: evaluation and new insights
Accepted in the Proceedings of the XII IAEG (International Association of Engineering Geology) Congress – 15-19 September 2014, Turin – Italy