Building inclination observation

There are two methods to measure the inclination of buildings: one is to directly measure the inclination of buildings; The other is to determine the inclination of the building by measuring the relative settlement of the building foundation. Here are some examples.

A, circular building tilt observation

As shown in figure 13-5, the center of the bottom of the chimney is O, and two points, A and B, are selected near the chimney to make AO and BO approximately vertical. The distance between AB and the chimney should be greater than 1.5H as far as possible, and H is the height of the chimney.

Figure 13-5 tilt observation of circular buildings

13-6 inclined members of circular buildings

Place the theodolite at point A, and measure the directional values of two points tangent to the bottom of the chimney 1 4 and two points tangent to the top, namely a 1, a2, a3 and a4 by directional observation.

Shang =(a2+a3)/2 (13- 1)

Lower a =(a 1+a4)/2 (13-2)

The component δa of chimney inclination (see figure 13-6) is

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The theodolite is placed at point B, and the other inclination component δA of the chimney is obtained in the same way, as follows

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Where: DA, db —— the distance from two points A and B to the bottom of the chimney;

R—— the radius of the bottom of the chimney, which can be calculated by measuring the circumferential diameter of the circle.

The inclination of the chimney is

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My tendency is

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Suppose the azimuth θ of OO' is

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After finding the magnetic azimuth angle under α with a compass, find the magnetic azimuth angle from point A to the bottom center point O with a compass. Under α-magnetic A, the magnetic azimuth of OO' is a magnetic OO'

A magnetic OO ′ = A magnetic A +θ (13-8)

Second, the general building tilt observation

Before observation, firstly, the upper and lower points or the upper, middle and lower points on the same vertical plane are set as inclined observation points on the two vertical facades of the building (structure), as shown in figure 13-7, with m, n, p and q as observation points. If the building is tilted, MN and PQ will change from vertical to diagonal. During observation, the theodolite is placed at a distance greater than the height of the building, aiming at the observation point M above, and the point is projected downward by the positive and negative mirror method to obtain N'. If n' does not coincide with n, it means that the building is inclined in the vertical direction. δB represents the horizontal distance between N' and n, that is, the oblique displacement component. Similarly, we can observe another oblique displacement component δA in the vertical direction, and the total oblique displacement is

δ=δA+δB( 13-9)

If the height of the building is expressed by H, the inclination is

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The height h of the building can be obtained in real quantity, so the inclination observation is mainly to find the inclination displacement δ.

Because the uneven settlement of buildings will inevitably lead to the inclination of buildings, the inclination displacement δ can also be calculated from the settlement observed. As shown in figure 13-8, if the settlement difference between point A and point B is δ and the spacing is L, then the component of inclined displacement in this direction is

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This formula can be used to calculate the tilt displacement components Δ a and Δ b in two mutually perpendicular directions, and then the total tilt displacement can be obtained.

If the building cracks due to uneven settlement, point A and point B should be selected on the same side of the crack. According to Δ a and Δ b and the chimney height h, the total inclination displacement Δ′ and inclination I can be obtained. If AO is taken as the reference direction, the inclination angle δ is

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Figure 13-7 direct tilt observation

Figure 13-8 Relative tilt observation