Abstract
As a large human gathering place, the city directly causes huge property losses and casualties due to the ground collapse accident every year. In order to explore the causes and damage characteristics of urban ground collapse, taking Xining City, Qinghai Province, as an example, this paper analyzes the accidental factors causing ground collapse through on-site geological exploration and then expounds the deformation characteristics of urban ground collapse by using the numerical simulation method of Fluent and PFC. Using the collapsible balance method, it is obtained that the insufficient thickness of the top plate of the Loess Soil Subgrade in the collapse pit area is the inevitable factor causing the final collapse. The results show the following: (1) The failure of water supply pipe is an accidental factor leading to the formation of underground cavity, and the ground collapse accident is hidden, sudden, and of high risk, and its deformation and failure development process is slow. (2) The critical thickness of the roof above the air raid shelter is about 22 m, and the actual thickness is about 11.6 m, which is prone to deformation and uneven settlement, which is also an inevitable factor causing ground collapse. (3) The numerical simulation study shows that the final formation deformation range is about 16 m. At this time, the height of the formed cavity is about 9 m. The plastic zone tends to develop around, and the maximum settlement position appears above the air raid shelter. (4) The collapse process includes four stages: water supply pipeline leakage, underground cavity formation, collapse critical state, and ground collapse. This research and analysis provides theoretical guidance and scientific basis for the investigation, measurement, detection, and monitoring of various underground pipe networks of urban roads.
Highlights
Ground collapse refers to a phenomenon or process caused by the downward collapse of surface rocks and soil under the influence of natural factors or human engineering activities, as well as the formation of collapse pits on the ground
The ground collapse in the urban area will increase the uneven settlement of the surrounding building foundations in the collapsed area and even lead to the collapse of the building [14]. e 2011–2020 National Land Subsidence Prevention and Control Plan, jointly compiled by the Ministry of Land and Resources, the Ministry of Water Resources, the Development and Reform Commission, the Ministry of Finance, and ten other ministries and commissions, points out that there are currently more than 50 cities in the country suffering from land subsidence disasters, distributed in Beijing, Tianjin, and Shanghai
According to the public meteorological data, there is no obvious precipitation process from December 2019 to the afternoon of January 13, 2020. e surface pavement in the surface area is covered by asphalt concrete, and the permeability is poor. erefore, the formation of collapse pit can exclude the influence of groundwater and surface water
Summary
Ground collapse refers to a phenomenon or process caused by the downward collapse of surface rocks and soil under the influence of natural factors or human engineering activities, as well as the formation of collapse pits (holes) on the ground. Ere are many factors that induce pavement collapse in urban areas, and water is usually the main factor, including groundwater action and surface water infiltration. Loess, when it meets water, has collapsibility effect and forms collapse [15]. This paper puts forward reasonable suggestions and measures to reduce the occurrence of such disasters again and do a good job of deformation monitoring between the collapse pit and surrounding buildings to prevent secondary damage [31]. e formation of collapse pit reduces the stability of the inner pit, so the inner wall of collapse pit should be monitored and strengthened in time [32]
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