Introduction of fixed inclinometer, principle of inclinometer

The principle of the fixed inclinometer 1 is: gravity accelerometer, which measures the component of the earth's gravitational force in the direction of measurement. The tilt change in the two directions of x y can be measured at the same time, so that the tilt direction and tilt angle of the point can be obtained by calculation; And it can be directly connected to the bus system for automatic data acquisition.

If the measurement range is small, the measurement accuracy is required to be high, and the high-precision electronic inclinometer is high. It is widely used to observe the horizontal change of soil such as mountain slopes, earth-rock dams, seaside embankments and building foundation pits. Changed the way portable inclinometers must be monitored manually; For remote areas, wireless automatic monitoring can be realized; It is a necessary precision measuring instrument for ports, railways, highways, high-rise buildings and other projects.

1) The assembly of the fixed inclinometer is completed before entering the hole, the fixed inclinometer at each point in each hole is connected by a wire rope, and the top fixed inclinometer is connected with the orifice device, and is fixed at the inclinometer nozzle with the orifice device.

2) the distance from the upper wheel frame of the fixed inclinometer to the orifice is the burial depth, and the burial depth of each set of fixed inclinometers at each point is determined according to the number (number of points) of the fixed inclinometer installed in each hole; According to the buried depth of each point, determine the length of the connecting wire rope between each point (including the length of the buckle locking).

3) There is a horizontal hole of the wire rope at the top of the fixed inclinometer, and there is a ring with a wire rope at the bottom (the bottom fixed inclinometer is not equipped with a lifting ring). There shall be no less than two sets of buckles used for each wire rope head locking (as shown in the figure above).

Installation of the inclinometer tube (see Figure 1). There are two kinds of inclinometer tubes, round and square, the domestic mostly use round, the diameter is 50mm, 70mm, etc., each section is generally 2m long, made of steel, aluminum alloy, plastic, etc., the most commonly used is PVC plastic pipe. Before hoisting the reinforcement cage, the inclinometer pipe is extended to the design length, tied to the reinforcement, and placed in the groove (in the pile hole) along with the reinforcement cage.

The bottom and top of the inclinometer tube should be sealed with a lid to prevent mortar, mud and debris from entering the hole.

Fig.1 Schematic diagram of the installation of the inclinometer tube.

2) The working principle of the inclinometer. According to its working principle, the inclinometer has servo acceleration type, resistance strain gauge type, differential capacitance type, steel string type and so on. There are two more commonly used servo acceleration type and resistance strain gauge type, and the servo acceleration inclinometer has high accuracy and is currently used more.

Fig.2 Schematic diagram of the structure of the inclinometer.

There is a pair of pulleys up and down the inclinometer, the upper and lower wheel pitches are 500mm, and its working principle is to use the gravity pendulum to always maintain the property of the lead straight direction, measure the inclination angle between the axis of the instrument and the vertical line of the pendulum, and the change of inclination angle can be obtained by the conversion of electrical signals, so that the displacement change value of the measured structure can be known.

3) Operational points. If the inclinometer tube is buried, it should be kept vertical, and if it is buried in the pile or underground diaphragm wall, the inclinometer pipe and the reinforcement cage should be tied firmly. The inclinometer tube has two pairs of directional grooves perpendicular to each other, one of which should be perpendicular to the edge of the foundation pit.

When measuring, it is necessary to ensure that the temperature of the inclinometer and the tube is basically the same, and the reading of the indicator is stable before starting to measure. Because the inclinometer measures the relative displacement between the two pulleys (500mm), the immobile point in the inclinometer tube must be selected as the reference point, and the bottom end of the pipe is generally taken as the reference point, and the actual displacement of each point is the accumulation of the relative displacement from the measurement point to the reference point. Inclinometer tube buried below the excavation face:

The rock layer is not less than 1m, and the soil layer is not less than 4m.

This instruction for use is only applicable to the VWD-J vibrating wire seam gauge produced by our company, including VWD-20J, VWD-50J VWD-100J and other models.

VWD-J vibrating wire joint gauge is suitable for long-term placement in concrete structures or other material structures and surfaces, measuring the opening and closing degree (displacement) of expansion joints or peripheral joints of structures, and can simultaneously measure the temperature of buried points.

The sensor of the vibrating wire gauge adopts the VWD vibrating wire displacement gauge, which is composed of its supporting accessories, and the vibrating wire gauge has the function of parameter recognition.

Inclinometer tubes are typically installed in vertical boreholes that pass through unstable soil to lower stable formations. The deformation of the inclinometer tube is observed using a digital vertical activity inclinometer probe, control cables, pulley units, and a reader. The first observation can establish an initial cross-section of the displacement of the inclinometer.

Subsequent observations show changes in the displacement of the section as the ground moves. During the observation, the probe moves from the bottom of the inclinometer tube to the top, pauses at a half-meter spacing and performs the measurement tilt. The inclination of the probe is measured by two force-balanced servo accelerometers.

An accelerometer measures the longitudinal position of the groove of the inclinometer tube, i.e., the inclination of the plane on which the gauge wheel is located on the inclinometer probe. The other accelerometer measures the inclination perpendicular to the plane of the wheel. The inclination can be converted to lateral displacement.

Comparing the current and initial observations, the amount of change in lateral shift can be determined, showing the movement displacement of the formation. Plotting the amount of change in the offset yields a high-resolution cross-section of the displacement. This cross-sectional diagram helps to determine the magnitude, depth, direction, and rate of ground motion displacement.

The horizontal solid and pure base inclinometer is an ideal monitoring instrument for data recording and real-time monitoring. Typical applications include: monitoring ground displacement caused by tunnel construction and excavation;

Monitoring of the stability of foundations such as compensation backfill and underpinning;

Monitor the subsidence of oil tanks, landfills, levees and dams. Same as a vertically fixed inclinometer. A horizontally fixed inclinometer is a sensor that monitors the change in vertical displacement.

The fixed inclinometer is divided into a vertical fixed inclinometer and a horizontal fixed differential simple oblique measuring trouser instrument.

Inclinometer is an instrument used to measure the top angle and azimuth angle of engineering structures such as boreholes, foundation pits, foundation foundations, walls and dam slopes1.