Research On Anti-floating Effect Of Underground Structure In Hefei Area

The use of urban underground space is a good solution to the problems which encountered in the rapid development of the current city such as traffic pressure,The situation encountered during the underground development process is often more complex than ground engineering.Among them,the most typical one is the problems caused by the buoyancy effect of groundwater on the structure in the soil layer.Therefore,it is of great theoretical significance and practical engineering application value to explore what kind of action mechanism the groundwater exerts on the structure when the structure is located in the soil layer.This paper is aimed at the anti-floating problem of Hefei underground structure.First,determine the basic properties of representative soil samples in Hefei through laboratory tests.Secondly,proposed a new experimental idea based on the previous studies to further explore the mechanism of the application of groundwater buoyancy in the typical clay soil in Hefei to embed the structure,and propose anti-floating theoretical basis for setting the waterproof position of the region;At the same time,linked the results which obtained from the experiment with the actual project case,and the numerical simulation analysis is carried out to further improve the accuracy of the analysis results.At the same time,the theory is linked with the actual situation and the practical availability of the theory is strengthened.The research work in this paper mainly includes the following parts.1.Summarize the previous theory and experimental research on underground anti-floating,put forward the research starting point and experimental ideas for the soil layer in Hefei area,and propose a combination of experiment and simulation.2.A series of basic physical and mechanical properties such as density,natural moisture content,boundary moisture content and specific gravity were tested for the typical clay soil in Hefei area,and the basic parameters were obtained to prepare for the anti-floating of cohesive soil indoors.3.Design and install the indoor test model device,and carry out the pure water test to verify the sealing and accuracy of the device.The test results prove that the difference between the measurement results of the model device and the theoretical calculation result is only 2%?4.Using the device to explore the buoyancy mechanism and variation law of groundwater in clay soil with different compactness,the test results show that the buoyancy of the structure in the clay soil layer will be delayed compared with the pure water state,about 2 The 4 days tend to be stable,and the final value is very different from the theoretical calculation.The reduction rate is below 10%.From the actual complexity of the project,it will not be reduced in the design.5.Using the method of numerical simulation analysis,combined with the theoretical results of the experiment and the actual situation,analyzed the mechanism of buoyancy under different water levels and the stress-strain trend of the structure.The simulation results show that the structural stress and strain increase with the rise of the water level,when the water level approaches At the critical water level,the stress-strain growth rate of the structure increases compared with the initial rise,and the tensile stress in most areas of the state structure exceeds the limit,and some anti-floating measures need to be taken.