Inclinometers Types, How They Work, & Functions

1. INCLINOMETER TYPES, HOW THEY WORK & FUNCTIONS

2. 1 What is an inclinometer? 2 Types of inclinometers 3 How do inclinometers work? TABLE OF CONTENT Inclinometer installation Procedure 4 5 Applications of Inclinometer Encardio-Rite’s models of inclinometers 6

3. 1 WHAT IS AN INCLINOMETER? An inclinometer is a sensor used to measure the magnitude of the inclination angle or deformation of any structure in percentage or degrees w.r.t gravity. Inclinometer are used to measure the slope gradient during activities like tunnelling, excavation and de-watering as such activities affect the ground that supports the structure. Each inclinometer system requires a combination of equipment and sensors to mea- sure and collect data.

4. 2 TYPES OF INCLINOMETERS Manual Inclinometer/Digital Inclinometer A manual inclinometer system is composed of the following components:

5. 2 TYPES OF INCLINOMETERS · Traversing Inclinometer Probe The traversing inclinometer probe consists of a couple of gravity-sensing accelerom- eters in a stainless steel carriage. It contains two sets of spring-pressured wheels that guide the probe accurately at any depth in the casing. The spacing between the wheels is usually 0.5m. The measurements are done in the A-axis i.e. in the direction of the wheels and B-axis i.e. perpendicular to the A-axis. The probes for horizontal casing are made differently. The sensors are mounted to measure the vertical displacement while keeping the bottom-tracking wheels fixed.

6. 2 TYPES OF INCLINOMETERS · Inclinometer Casing The inclinometer casing is used to guide the probe within the casing with four longi- tudinal wheel grooves, spaced 90° apart. Out of these, only one set of the opposite grooves in the expected direction of the displacement is used. The casing is generally installed in the ground, within drilled holes and the annular space grouted. However, there are other installations where the casing is embedded in concrete structures. The casing connection seals out soil, grout, and other material while keeping the grooves clean.

7. 2 TYPES OF INCLINOMETERS · Inclinometer Cable Reel The inclinometer cable reel is attached to the slope gauge probe and readout device. It is used to transmit electrical signals during measurements and serve as a precise, repeatable depth control for the probe. The cable has a distinct design and is constructed to provide long-term longitudinal stability. It is made essentially to serve as a measuring tape. In other words, it is made to be durable, waterproof, non-stretch, non-shrink with a high torque resistance

8. 2 TYPES OF INCLINOMETERS · Mobile Readout Unit The mobile readout unit is used to record the data at each depth interval. It is capa- ble of storing multiple data sets and can perform field checks to verify the validity of the measurements.

9. 2 TYPES OF INCLINOMETERS An In-place Inclinometer consists of the following components: • • • • • • • • Bottom wheel assembly In place Inclinometer sensor Spacer tubing (length: need to specify as per the requirement) Placement tubing (Topmost part) Suspension kit Protective cover Junction box Data Logger: ESDL-30

10. 2 TYPES OF INCLINOMETERS In-place inclinometers are further divided into two types - Uniaxial and Bi-axial. The biaxial in-place tilt indicators consist of a couple of MEMS sensors attached at 90°.

11. 3 How do inclinometers work? The inclinometer probes are built using two types of accelerometers: Servo-Accelerometer The force-balanced sensing elements housed in an inclinometer probe detect the change in tilt (from reference). The probe consists of a couple of biaxial servo-accelerometers. It is fitted with two sets of spring-pressured wheels to guide the probe along the longitudinal grooves of the inclinometer casing.

12. 3 How do inclinometers work? MEMS Accelerometer Such clinometers are termed as MEMS Inclinometers. Currently the MEMS (Micro-Electro-Mechanical Systems) technology is being used to build the tilt sensor probe. The MEMS consist of mechanical elements, sensors, actuators and electronics on a common silicon substrate through microfabrication technology. Acceleration causes deflection of the proof mass from its centre position. There are 32 sets of radial fingers around the four sides of the square proof mass. Each finger and pair of fixed plates make up a differential capacitor. The deflection of the proof mass is determined by measuring the differential capacitance.

13. 3 How do inclinometers work? By this method, both dynamic acceleration (i.e. shock or vibration) and static accel- eration (i.e. inclination or rotation) can be sensed. Signal conditioning is carried out within inclinometers so that a simple output signal is obtained. This output can be used in conjunction with a calibration sheet to easily calculate the amount of tilt that has occurred.

14. 4 INCLINOMETER INSTALLATION PROCEDURE Inclinometers can be installed in two ways: Vertically Vertical inclinometers are used for measuring relative horizontal displacements af- fecting the shape of a guide casing, embedded in the ground or structure. A near-vertical gauge well is constructed by installing the clinometer casing in a borehole, embedding in an earth/rockfill or concrete structure during and post-con- struction. The clinometer probe is then passed through the entire length of the gauge well from bottom to top, taking readings at fixed pre-determined intervals. A probe consisting of a couple of precision accelerometers senses the inclination of the access tube 90° to each other.

15. 4 INCLINOMETER INSTALLATION PROCEDURE The bottom end of the guide casing serves as a stable reference (datum) and must be embedded beyond the displacement zone. Relative displacement over time is determined by repeating measurements at the same depths and comparing data sets.

16. 4 INCLINOMETER INSTALLATION PROCEDURE Horizontally Horizontal inclinometers are installed to monitor the profiles of settlement or heave under storage tanks, embankments, dams, and landfills. The horizontal inclinometer probe consists of a force-balanced servo-accelerometer which measures inclination from horizontal in the plane of the probe wheels. A change in tilt angle is noted and this indicates that the movement has occurred. The movement is calculated by finding the difference between the current inclination reading and the initial reading while converting the result to a vertical distance.

17. 5 APPLICATIONS OF INCLINOMETERS Monitoring retaining structure's performance The performance of retaining structures, such as sheet pile walls, soldier pile walls or mechanically stabilized earth (MSE) systems is adversely affected by lateral pres- sures or ground movements. Deformations in retaining structures could occur during and after construction. The inclinometer system is designed to measure the magnitude of tilt and differen- tial deformation behind or within the wall face. The casing can be installed vertically in boreholes, adjacent to the wall face or can be embedded within structural elements. Traversing-type inclinometer probes are usually used to determine the relative shape of the retaining structure and changes in it over a while.

18. 5 APPLICATIONS OF INCLINOMETERS Monitoring slope stability Slopes in cuts or fills embankments can be monitored for stability during and after construction. In such cases, the inclinometer casings are installed inside the bore- holes, similar to landslide monitoring. Monitoring Excavations The impact of excavations is monitored to study its effect on nearby structures, utili- ties, and other critical facilities. In such cases, inclinometer casings are placed inside the vertical boreholes located between the excavation boundary and the nearby facilities. The inclinometer casing can also be installed in the excavation system.

19. 5 APPLICATIONS OF INCLINOMETERS Monitoring during tunnel drilling Inclinometers can be used to monitor stress relief ground movements and possible displacement of rock blocks during the construction of tunnels and shafts. Gradient meters are used to verify the adequacy of ground supports, detect potential flaws in the construction approach, and serve as a warning system for potential ground failure. Monitoring pile and drilled pier performance Inclinometers can be used to measure the deformation of deep foundations subject- ed to large lateral loads. The level meter/tilt sensor casing can be embedded within or attached to structural elements.

20. 6 ENCARDIO-RITE’S MODELS OF INCLINOMETERS Encardio-Rite deals with one of the most advanced MEMS digital inclinometer systems, and in-place clinometers. Model EAN-26M Digital Inclinometer System Encardio-Rite's Model EAN-26M is one of the most advanced MEMS digital inclinom- eter systems. It uses the capability of high computational power and large high-resolution colour display of today’s Android mobile phones.

21. 6 ENCARDIO-RITE’S MODELS OF INCLINOMETERS The mobile phone uses the wireless Bluetooth connection to communicate with the inclinometer reel unit. The EAN-26M Inclinometer system is much lighter in weight and is very much liked by field personnel who have to carry the system from borehole to borehole for log- ging. The digital slope gauge system consists of a traversing type digital tilt sensing probe that is connected to a reel unit kept at borehole top. The reel unit consists of a winding reel that holds the cable and a wireless Bluetooth relay unit that sends the digital probe data to the mobile phone.

22. 6 ENCARDIO-RITE’S MODELS OF INCLINOMETERS Model EAN-26M-2 Vertical Inclinometer Probe System In Model EAN-26M-2 Vertical Inclinometer Probe System, a digital probe of stainless steel construction is fitted with two pairs of pivoted sprung wheels which can rotate freely.

23. 6 ENCARDIO-RITE’S MODELS OF INCLINOMETERS The spring-loaded wheel arms help to position the probe centrally inside the access casing at any required depth. The probe consists of two precision MEMS accelerometers. One accelerometer has its axis in the plane of the wheels and other at 900 to it. The probe senses horizontal deviation between the probe axis and the vertical plane, simultaneously in both the orthogonal axis

24. 6 ENCARDIO-RITE’S MODELS OF INCLINOMETERS Model EAN-51MV, EAN-52MV Vertical In-Place Inclinometer System Encardio-Rite's Model EAN-51M vertical in-place inclinometer is used to measure the lateral movement of earthworks or structures. It provides significant quantitative data on the magnitude of inclination or tilt of a foundation, embankment or slope and its variations with time.

25. 6 ENCARDIO-RITE’S MODELS OF INCLINOMETERS It also provides the pattern of deformation, zones of potential danger and effective- ness of construction control measures undertaken. Its data logging and real-time monitoring feature help to provide early warning in case of failures. It also helps in observing the behaviour of ground movement after construction and indicates potentially dangerous conditions that may adversely affect the stability of the structure, its foundation and appurtenant. A suspension stainless steel wire rope is available to position a single or group of sensors where the profile of entire borehole is not of interest but only a specific por- tion needs monitoring.

26. THANK YOU www.encardio.com