Geoflex inclinometer instrumentation

GeoFlex Applications

A real-time alternative to the traversing probe type of inclinometer, the GeoFlex system is a string of closely spaced MEMS sensors that employs a chain of sensors and does not require an on-site operator. It is ideal for data logging and real-time, remote monitoring for critical applications such as construction control.

Typical applications include:

Monitoring landslide areas above dams, highways, and railroads to provide early warning of slope failure.
Monitoring ground movements induced by tunnel construction and excavation.
Monitoring deformations of embankments and retaining walls.
Monitoring deformation of deep foundation elements.

Operation

The GeoFlex system consists of a number of sensor nodes in a vertical string installed in either Schedule 40 PVC or in an inclinometer casing. The pipe or casing provides access for subsurface measurements. The joints between each sensor are robust, allowing the system to maintain a consistent orientation of all the nodes, regardless of whether it is installed in PVC pipe or ABS inclinometer casing.

The pipe or casing is typically installed in a vertical borehole that passes through a suspected zone of movement. The nodes are spaced at either 0.5 meters or 2 feet and provide a reading resolution similar to a traversing probe. The system spans the zone of movement and when the ground moves, the pipe/casing moves with it, changing the inclination of the nodes inside.

Inclination measurements from the nodes are processed to provide graphs of the casing profile and changes in the profile. Changes indicate displacement (movement).

The GeoFlex system is connected to a data acquisition system, and readings are transmitted to processing software that can trigger alarms based on displacements or rate of change.

GeoFlex Advantages

Real Time Monitoring -The GeoFlex system is ideal for continuous, unattended monitoring and can deliver readings in near-real time.

Signal Cable Installation - Each sensor is supplied with cable so that it can be connected to the sensors above and below, effectively reducing the number of signal cables to just one. This eases installation, simplifies connections to the logger, eliminates the need for multiplexers, and greatly decreases cable costs.

Convenient Shipping and Transport - GeoFlex systems have joints capable of bending to 90°, allowing for a compact shipping option. Five segments, each 2.5 meters or 10 feet long, can be shipped in a carton measuring approximately 64 x 64 x 64 cm (26 x 26 x 26 in) which weighs less than 22 kilograms (50 pounds). This allows for the system to be shipped via common overnight carrier as well as fit in most standard vehicles.

The GeoFlex system can also be installed with sensorless nodes at the top of the system, allowing the designer to economize by only monitoring the zone of interest and bypassing the upper layers.

Durable Components - Nodes, cables, connectors and gage rods are exceptionally durable, making it practical to remove the systems at the end of the project and redeploy them on other projects.

Data Acquisiton and Reduction - The GeoFlex system is compatible with Campbell Scientific data loggers, including the CR300, CR800, CR1000, CR1000X, and CR6. The GTecLink Wireless Dataloggers are also compatible with the GeoFlex system. Up to 10 nodes can be connected to a Digital Node and, up to 50 nodes can be connected to a GeoFlex node. The system outputs the displacement as engineering units, requiring less computing power and a lighter load on your data acquisition system. The nodes are preloaded with the calibration information, allowing the segments to be installed in any order.

Complete Solution - Durham Geo Slope Indicator offers complete monitoring solutions that include data loggers and software such as Atlas Web-Based Monitoring , which can present profile plots and trend plots of inclinometer data just minutes after the readings are obtained.

GeoFlex Specifications

GEOFLEX SYSTEM CONFIGURATIONS
Casing	Choose 70 mm (2.75 in) or 85mm (3.34 in) diameter inclinometer casing or 38 mm (1.5 in) diameter Schedule 40 PVC pipe
GeoFlex Segments	Choose a number of GeoFlex segments. When ordering, indicate the type of casing being used so that the proper centralizers will be installed on the system
Suspension Kit	Order one suspension kit for each installation. The kit includes the suspension gate and hardware for securing the system
Signal Cable	GeoFlex segments consist of interconnected nodes with a connector at the top and bottom of the segment. A bottom plug is required for the bottom of the system. A jumper cable connects the top of the system to the data logger
Data Logger	A number of Campbell Scientific data loggers are compatible with the GeoFlex system. Two GeoFlex systems can be connected to each CR6 or CR1000X. With an MD485 module per GeoFlex system, the CR1000 can read five systems, the CR800 three systems and the CR300 one system. Up to 10 nodes can be connected to a GTecLink Digital Node and up to 50 Nodes can be connected to a GTecLink GeoFlex Node.
Data Reduction Software	Readings retrieved from the logger can be processed manually by spreadsheet or automatically by the Atlas webbased monitoring system

GEOFLEX NODE SPECIFICATIONS
Sensor Type	MEMS (Micro Electro-Mechanical Systems) tilt sensor for inclination readings
Requirements	Minimum supply voltage of 10 Vdc. Maximum supply voltage of 30 Vdc. Digital RS485 signal requires Campbell Scientific data logger
Calibrated Range	±30 degrees from vertical over a temperature range of -10°C to +40°C
Resolution	9 arc seconds or 0.04 mm/m using the CR1000 data logger
Repeatability	±82 arc seconds or ±0.4 mm/m
Required Casing	Fits 70 mm (2.75") or 85mm (3.34 in) diameter inclinometer casing or 38 mm (1.5") diameter Schedule 40 PVC pipe
Waterproof	Waterproof to 2 MPa (300 psi)
Weight	0.54 kg per 0.6m (1.2 lb per 2 feet) gauge length
Signal Cable	Jumper Cable for connecting the system to the datalogger. Connectors are rated to 70 MPa (10,000 psi)