Information on deformation monitoring

Deformation monitoring or known as building (structure) deformation measurement, it is one of the important contents of engineering measurement, throughout the construction and operation of the entire process of engineering construction. But with the passage of time, due to the influence of various factors will produce deformation. The main factors are: 1, the cause of the foundation (geological structure is not uniform, the physical properties of the soil is different, the plastic deformation of the soil base); 2, the cause of the environment (changes in the water table, changes in atmospheric temperature); 3, the cause of external forces (building (structure) building itself, wind, vibration, etc.). These factors can lead to the project buildings (structures) over time and settlement, displacement, deflection, tilt, cracks and other phenomena - deformation. I remember the special case in mid-July 2009, Chengdu City, "Campus Spring District," the original distance between the two buildings on the very close actually slightly tilted, leaning together. There is also November 15, 2009, a section of the Hangzhou subway construction site suddenly occurred in a large area of roadway collapse accident, resulting in Xiaoshan Xianghu Style Avenue 75 meters of roadway collapsed, and sank 15 meters. Types are: static deformation: mainly refers to the deformation of the deformed body over time with a slower deformation rate, it takes a longer time to be detected deformation. Dynamic deformation: mainly refers to the deformation of the deformed body under the action of external load, its size and speed are closely related to the load. According to the deformation characteristics: self-deformation: the deformation of the deformed body itself, including: expansion and contraction, misalignment, bending and torsion of four kinds of deformation; rigid body displacement: the deformed body rigid body displacement contains the whole translation, the whole rotation, the whole lifting and tilting of the whole of the four kinds of deformation. According to the deformation rate: long cycle deformation: refers to the cycle of deformation in a longer period of time, such as dams in the operation period by the water pressure/temperature and other effects of the annual cycle of deformation. Short-cycle deformation: refers to the cyclic deformation that occurs over a short period of time, such as the Sunday deformation that occurs in high and large buildings under the action of sunshine. Instantaneous deformation: refers to the instantaneous deformation under the action of short-time loading, such as chimneys/towers and other tall buildings under the action of wind deformation. According to the deformation characteristics: Elastic deformation: when the action of the load in the elastic range of the member and the deformation occurs generally for the elastic deformation, which is characterized by when the load is withdrawn, the deformation will also disappear. Plastic deformation: when the load acts on the inelastic body or the load exceeds the elastic limit of the member, it will produce plastic deformation, which is characterized by when the load is withdrawn, the deformation does not or does not disappear completely. In actual engineering, elastic deformation and plastic deformation will exist at the same time.