Ground settlement, especially the ground surface settlement induced by subway tunneling is an important issue. However, there is no an agreed standard for controlling ground surface settlement during the subway construction at present. The control standard of ground surface settlement was studied using the methods of statistical analysis and numerical simulation based on the running tunnel in Beijing subway. According to the research results, a conclusion could be obtained that the ground surface settlement can be controlled within 40 mm using the general construction measures in Beijing subway running tunnel construction, and furthermore, the settlement of 40mm will not damage the existing nearby structures and utilities including neighboring buildings, bridges and pipelines, etc. So the control valve of 40 mm is rational, which can be adopted as the control standard of ground surface settlement induced by running tunnel construction in Beijing subway.
In order to study the influence of cavity above the tunnel on stratum deformation and failure in urban tunnelling, the model test method was adopted based on the parameters of the stratum and tunnel section size in Beijing subway. The stratum responses were obtained under the conditions without ground cavity and with ground cavity above the tunnel. The responses include the stratum stress distribution, stratum settlement law and stratum failure process. It was concluded that the existence of ground cavity above the tunnel worsened the stratum condition and accelerated the progress of stratum deformation and failure. Furthermore, the failure began from the cavity and the damage scope was bigger than that under the condition without cavity according to the test results. The research results can be referenced for the similar tunnel engineering.
There are more safety risks in subsea tunneling due to the particularity and complexity of its surroundings, so how to control the safety risks effectively has become an urgent problem. Based on the analysis of safety accident cases induced by the subsea tunneling, accident types and corresponding harms are pointed out. By analyzing the engineering characteristics and technical difficulties of the subsea tunnel systematically, the characteristics and occurring mechanism of the safety risk are revealed, and the fact that water inrush is the main safety risk in subsea tunneling is pointed out definitely. Furthermore, the contents of the safety risk control as well as relevant technical system are provided mainly based on water inrush risk, which can be referenced to make control schemes against the safety risk in subsea tunneling.
Using elastoplastic finite element method study the interface stress distribution of Sn3.5Ag0.75Cu lead-free solder at different temperatures and different strain rate. Numerical analysis results show that: when strain-rate is identical, as the temperature rises, the interface stress increased rapidly of Sn3.5Ag0.75Cu lead-free solder and the substrate binding sites, from 11 °C when 2.6MPa rose to 90 °C in 49.7MPa, so the temperature is very large have effects of the interface stress of the lead-free solder and the substrate binding sites; when the temperature is constant, as the strain rate increases, Sn3.5Ag0.75Cu lead-free solder and the substrate binding sites of the interface stress showed a slight increase, from 0.005% / S when the 49.47MPa rose to 0.005% / S when the 50.08MPa, so strain rate on lead-free solder and the substrate binding sites of the interface stress effect is very small, indicating Sn3 .5Ag0.75Cu lead-free solder has strong rate-independent nature.
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