Abstract
Hydrostatic levelling system (HLS) is widely used to monitor the settlement of major projects, such as high-speed railways, bridges, tunnels, dams, and nuclear power plants; ambient temperature is the most important influencing factor in the actual engineering settlement detection process. In order to systematically study the influence of ambient temperature TA on the test accuracy of the HLS, a test platform was built in the ambient temperature laboratory, and the influence of factors, including the amount of TA change, the rate of increase/decrease of TA, the expansion coefficient of the connecting pipe, and the distance of the measuring point, on the HLS test accuracy was quantitatively analyzed. The test results show that the elevation of a single HSL case has a linear correlation with the ambient temperature; when the temperature rise rate is greater than 0.1°C/min, the measured data are distorted due to incomplete development of material expansion. The temperature influence coefficient of a single HSL case is linearly related to the expansion coefficient deviation between the refrigerant and pipe; the test error of the double HLS case caused by TA is attributed to the expansion coefficient deviation of the pipe and the refrigerant between the base station and the measuring point. The relative temperature influence coefficient increases as distance measurement increases, and the HLS test error caused by TA will maintain a constant value when the distance measurement exceeds a certain value.
Highlights
Chen Jihua [21] thought that the uneven temperature would lead to uneven liquid density in the hydrostatic levelling system (HLS), which leads to the test error; he proposed a preliminary approach to eliminate temperature impact
A test platform with differential pressure hydrostatic levelling was installed in the ambient temperature laboratory. e high-precision temperature sensors were adopted to collect the temperature of each measurement point of the HLS, and the influence of factors, such as the ambient temperature, the increasing/decreasing rate of the ambient temperature, the expansion coefficient of the connecting pipe, and the distance of the measuring point, on the HLS test accuracy was quantitatively analyzed. e relevant conclusions can be drawn as follows: (1) e elevation of the single HSL measuring point showed a single correlation with the ambient temperature
When the expansion coefficient of the selected pipe was close to the expansion coefficient of the liquid medium, the effect of the temperature on single HSL test accuracy can be ignored
Summary
With the rapid socioeconomic development and urbanization, major national infrastructure projects, such as high-speed railways, large-span bridges, ultralong tunnels, high-rise buildings, integrated pipeline corridors, and dams, are increasing; their uneven settlement, deformation, and foundations are a precursor to the engineering failure [1, 2]. erefore, the accurate measurement for the settlement or deformation is crucial and can provide a scientific reference for the design, construction, and operation of major foundation projects; reliable data for numerical engineering analysis and long-term deformation prediction can be provided [3,4,5]. Settlement monitoring methods include geometric levelling, trigonometric levelling, GPS measurement, CCD optical imaging measurement, laser convergence measurement, hydrostatic levelling, and fibre grating measurement [6, 7]. Xu Shaofeng [22] investigated the influence of temperature and pressure change on the accuracy of HLS testing and proposed a temperature correction model considering the pipe’s expansion coefficient. The existing temperature correction model, based on the water medium, no longer has practical engineering significance, especially in the subzero state; there are certain differences in the HLS measuring point spacing arrangement and pipe materials in the actual project. E high-precision temperature sensor was used to collect the temperature data, the change of TA, the increase/decrease rate of TA, the expansion coefficient of the connecting pipe, and the distance of the measuring point on the HLS testing accuracy which is quantitatively analyzed. An evaluation method for the influence of ambient temperature on the HLS testing accuracy was developed
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