Cost-effective technology of mass-movement EWS

Zurab Chelidze, Nodar Varamashvili, Tamaz Chelidze, Victor Chikhladze

, European Centre “Geodynamical Hazards of High Dams”of the Council of Europe. M. Nodia Institute of Geophysics. 2017

EWS Concept

•       Cost-effectiveness

•       Parameters

•       Sensors

•       Board

•       Low-power source

•       Transmission

•       Analysis/Decision Making

•       Why cost-effective system

The cost of precise enough monitoring/EWS  equipment is as a rule very high (of the order of hundreds of USD) and it  is practically impossible for developing countries to purchase even one system. If we take into account that the number of mass-movement dangerous sources is huge - only in Georgia there are 40000 of potential debris flow/landslide sources - the financial expenses are unaffordable.

Thus, the multitude of dangerous sources, need of covering the source area by many sensors, expensiveness of supporting personnel for a long period at potential mass-movement areas, growing number of  exposed vulnerable objects and limited resources of developing countries, which are most prone to mentioned hazards call for developing cost-effective and the same time accurate automatic monitoring/early warning telemetric systems

 Fusion of these apparently conflicting concepts (cost-effectiveness and accuracy) became possible due to the progress of modern high-tech systems.

The price of our EWS hardware is of the order of 500 USD.

Choice of long- and short-term precursors

The choice of precursory physical field is important: the precursors should be informative for diagnostics and easily measurable. The suggested debris flow/landslide EWS network  includes monitoring  of two main factors, leading to mass-movement: humidity/pore pressure/conductivity of the soil (as a relatively long-term precursor) and displacement/acceleration/acoustics caused by initiation of mechanical motion (as a short-term precursor).

Block scheme of EWS “Watchdog”

   Sensors: micro-accelerometers MEMS

“ Microelectromechanical Systems (MEMS) are miniature devices comprising of integrated mechanical (levers, springs, deformable membranes, vibrating structures, etc.) and electrical (resistors, capacitors, inductors, etc.) components designed to work in concert to sense and report on the physical processes in their environment.

 

Micro-accelerometers with MEMS sensors.          Array of Micro-accelerometers  with MEMS sensors

MEMS – TROMINO records comparison at various extensions

Differentialaccelerometry preliminary test

Both sensors are rigidly connected during motion

                                                                                Differential signal between fixed and moving sensors

Sensors: Humidity

Humidity sensor: HF micro-radar system (2.7 GHz). The emitted by micro-radar HF EM signal is absorbed by the media. The strength of absorption depends on the value of dielectric constant (DC) of the media:  as the DC of the pore water (80) is much larger, than the DC of dry porous rocks (2-5), the micro-radar’s HF EM signal is suppressed in humid rock, i.e. its strength is inversely proportional to humidity of media.

The field intensity I of micro-radar versus                      The yield of the granular medium D, mm versus volumetric water content, W % (horizontal system)     volumetric water content, W %

Note the drastic change in the yield D of the system at 27% volumetric humidity (mark 200)

Sensors: Tilts.

Comparison of precision tiltmeter „Applied Geomechanics” 701-USA (red) and our tiltmeter system (blue)

Simple Processing board- collects signals from sensors and works out short-distance (community) alarm level

Analog Processing Board and in-out terminal

Sensors and Processing Board Box for differential accelerometry

Alarm Box and Siren

Early Warning System “Watchdog”: Field version for remote control

1- Rod post
2- Solar batteries
3 – Processing block
4 - Sensors
5 – Transmitting block with GPS antenna
6 - Server of the  Monitoring system