Abstract
Based on a subway station excavation construction project in the soft soil area in Nanjing, an informationized monitoring scheme was conducted during the construction of excavation, and the theories of displacement prediction were introduced into the scheme for the evaluation of the horizontal displacement of the retaining structure and the settlement of the surroundings around the excavation. Based on these theories and the monitoring data, a numerical simulation based on the commercial FEM numerical analysis software, Midas GTS NX, was conducted to simulate the whole construction process. To handle the large displacement of the retaining structure observed during the construction, the actual soil layers’ status discovered by excavating, which can reflect the physical characteristics of the soil, the construction condition, and the variation trend of the monitoring data, was used in the back analysis of the factors that induced the large deformation of the retaining structure, and the analysis result was fed back to the countermeasurement organization and design such as erecting temporary steel strut. The effectiveness of these measurements in the aspect of the reduction of the deformation rate was verified, which can provide reference to the design and construction of a similar project in soft soil area.
Highlights
In recent years, to make full use of underground spaces, the scale of excavations was designed to be deeper and deeper and larger and larger, there are many difficulties and risks in the construction of these excavations, and the demand for the deformation control is more and more strict; it is important to informationize the monitoring scheme of these excavations and predict the deformation of the retaining structure and the surrounding soil in these excavations
To make the informationization of the monitoring scheme come true, the present theories of ground settlement and numerical simulation should be used to predict the deformation of the retaining structure and surroundings around excavations, and the construction scheme should be modified based on the feedback from the real-time monitoring; in other words, the informationization of the excavation scheme requires the combination of present theories, numerical analysis, and real-time feedback from the construction field [1,2,3,4,5,6,7,8]
Based on the monitoring data from seven excavation construction projects, O’Rourke analyzed the ratio relationship of the horizontal displacement of the retaining structure to the Mathematical Problems in Engineering vertical displacement of the surface ground and the influences of different measurements in the whole construction process such as dewatering measurement which was conducted before the excavation construction, the erection of steel strut which was conducted during the construction, and the construction of the overground structure after the excavation construction on the deformation of the soil [17]
Summary
To make full use of underground spaces, the scale of excavations was designed to be deeper and deeper and larger and larger, there are many difficulties and risks in the construction of these excavations, and the demand for the deformation control is more and more strict; it is important to informationize the monitoring scheme of these excavations and predict the deformation of the retaining structure and the surrounding soil in these excavations. Peck proposed an empirical formula to estimate the ground settlement by analyzing a great amount of excavation construction projects in Chicago, Oslo, and many other areas and summarized the horizontal displacement of the retaining structure and ground settlement data in different geological conditions and different retaining structures. In this formula, the soils were divided into three types according to their hardness; the softer the soil is, the larger the settlement and the area influenced will be [16]. Ese works can provide effective feedback to the designers and constructors of the excavation in time and provide important reference to the design, construction, and study of similar projects
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