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From the preparation of construction to the completion of all projects for a period of time after the completion of high-rise buildings, deformation observations such as settlement, displacement and inclination should be carried out according to the requirements of construction and design.
It is generally divided into two parts: One part of the 100 help plan is to observe the deformation of the surrounding adjacent buildings (structures) and slope protection piles caused by the construction of high-rise buildings, as well as the deformation of the impact of sunshine on the construction of buildings, so as to ensure safety and correct guidance of construction, which is the deformation observation that directly serves the construction;
The other part is to observe the deformation of various parts of the high-rise building during the construction process and after completion, to check the construction quality and the correctness of the engineering design, and to provide feedback information for the foundation and structural design of the foundation.
Today, let's take a look at the settlement observation of high-rise buildings.
1. Observation of the impact of construction on adjacent buildings (structures).
When piling and using well points to lower the water level, adjacent buildings (structures) may experience deformations such as uneven settlement, cracks and displacement. In order to deal with this situation, a reference point should be set up outside the influence range of piling and precipitation at the well point, and a settlement observation point should be set on the building (structure) within a certain range from the foundation pit for settlement observation.
At the same time, in view of these deformations, corresponding safety protection measures should be taken to minimize the impact on adjacent buildings (structures).
2. Observation of the settlement of the base of the construction tower crane
Tower cranes used in the construction of high-rise buildings, due to their large tonnage and arm length, may cause accidents due to the sinking or tilting of the tower base. In order to ensure the safety of the tower crane, it is necessary to observe the settlement of the four corners of the tower base in a timely manner, and check the sinking and tilting conditions of the tower base.
3. Ground-based rebound observation
When the depth of the foundation pit increases, the amount of the original soil on the bottom surface of the foundation pit will also increase after excavation, resulting in the increase of the subsidence after the construction of the building. In order to measure the springback value of the foundation, it is necessary to drill holes in the longitudinal and transverse main axes of the proposed high-rise building. The diameter of the borehole is 100 mm, and the depth reaches 300 500 mm below the bottom surface of the foundation. A special survey mark is placed inside the borehole casing and its elevation is measured. When the casing is lifted, the measurement mark remains in place.
After the pit has been dug to the bottom, the elevation of these signs is measured again. Before pouring the concrete foundation, an elevation measurement is carried out to obtain the springback values of the foundation at each point. These data are important data for the study of foundation soil structure and foundation subsidence of high-rise buildings.
4. Observation of subsidence of foundation stratification and adjacent ground.
The purpose of this observation is to understand the different depths under the foundation, the deformation of different soil layers and the depth of the compressed layer, as well as the different effects of building settlement on the adjacent ground from near to far. The purpose and method of this observation are basically the same as those of ground-based rebound observation.
5. Observation of the settlement of the building itself
This is the main content of settlement observation of high-rise buildings. When the foundation cushion is poured, a temporary observation point is buried at the position specified in the design of the cushion. Generally, every floor of construction is observed until completion. After the completion of the project, it should be measured four times in the first year, twice in the second year, and once a year after the third year, until the subsidence is stable. Generally, the foundation of sandy soil is measured for two years, the foundation of cohesive soil is measured for five years, and the foundation of soft soil is measured for ten years.