| With the continuous development of our country road traffic, it provides a good platform for tunnel construction technology upgrade. From the past to the present, the development of tunnel construction method is diverse, and pipe-roof pre-construction method as a method of pre-reinforcement of tunnel excavation have been used frequently in the tunnel construction. The biggest characteristic of this method is the construction safety, good adaptability to formation and small impact on the environment etc. Gongbei tunnel pipe roof project of Gangzhuao bridge is located in a place where it has complex geological conditions, important geographical position, using this method can effectively solve such problems. As the pipe-roof pre-reinforcement construction is a plurality of pipe jacking, there might be multiple disturbance formation, so as to make the pipe-roof, buildings and underground pipelines deformation of surrounding soils. However, big deformation of surrounding buildings and pipelines will be destructive, so pipe curtain construction can effectively predict the impact on surface subsidence. It can not only understand pipe roof construction change rule of the construction on the ground surface deformation, but also can take preventive measures in advance, effectively preventing the happening of the disease. In the process of pipe jacking jacking, in order to make long distance pipe jacking smoothly completed, we need to inject lubrication slurry in the process of construction. And lubrication slurry has two main functions in the process of pipe jacking construction:on the one hand, the lubrication slurry play a role of lubrication, changing the friction between pipeline and soil characteristics, making it changed from dry friction to wet rubbing, and decreasing the excavating resistance. On the other hand, lubrication slurry has the function of supporting soil and filling construction clearance. Therefore, in the case of accurately determining the frictional resistance before construction, it will be helpful for us to choose pipe material and pipe jacking machine models. The interaction between sockets is also very complex when pipe jacking constructs. So, understanding the mutual influence through effective way between sockets is helpful for the tube screen design and construction.In view of the above issues, the paper relies Gongbei bored tunnel of Gangzhuao bridge, Based on theory analysis and experience summary of the previous. Through theoretical analysis, finite element simulation, laboratory test and field monitoring of the key problems in construction of pipe roof. Mainly aimed at the effect of drag reduction of the lubrication slurry, research the mechanical behavior of pipe sections and Pipe roof construction on the influence of surface subsidence, etc.The specific contents are as follows:(1) experimental study on friction characteristics of two kinds of common contact state with a simple experimental device for pipe jacking construction:pipe-Lubrication slurry-soil contact state and pipe-soil contact state. Through the range analysis of the experimental results, the bentonite on the drag reduction effect is the most obvious, and according to the basic rules of test and put forward the improvement methods in practical engineering.(2) Combined with multi-body dynamics and the stratum structure method and using ABAQUS finite element software for multi-body model to explore the mechanical behavior of the pipe section of pipe jacking. The study found that the jacking force of pipe section appear certain regularity, and then calculate the total force of cylinder in distance under different jacking jacking force, the results are in good agreement with the monitoring data in Engineering. Research of relative rotation angle and horizontal force, it shows that relative rotation angle of curved pipe is generally relatively small, but that the impact can not be ignored about the horizontal force. it is impact to jacking force that the friction resistance of unit area and the pipe end head resistance. However, the friction is a major factor in the formation of jacking force.(3) Combined with the engineering data of the Gongbei bored tunnel of Gangzhuao bridge. For single pipe jacking and small spacing parallel pipe jacking through three-dimensional finite element simulation by means of finite element software ABAQUS. The results of the study:1) Single pipe jacking, the front surface of the soil excavation does not deformation, the subsidence of soil at the back of the excavation face. It is happened that the greater the distance of jacking the greater subsidence, and the maximum settlement is smaller with the monitoring data.2) Mainly to the settlement deformation of ground surface, and With the continued increase jacking distance, surface deformation continues to sink. The maximum subsidence over the top to the sides of the tube axis diffusion.3) A plurality of pipe-jacking of surface subsidence will have a cascading effect. And the second pipe when the first pipe below the trend of the settling tank to produce impact. the curve showing a phenomenon that the left side of the settling tank "concession" and the right side of the settling tank "skinny". When the third pipe in the first pipe above, the impact of surface subsidence is much smaller, and does not change the trend of settling tank. |
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