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只看楼主倒序阅读使用道具楼主发表于: 2008-06-28

The design of the seismic and shock absorption tunnel

Abstract: Based on the damage to the tunnel structure and the study of the characteristics, the article shows the design of the seismic and shock absorption tunnel. Including the basic calculation method, it shows the specific measures of the seismic tunnels. This paper also describes the shock absorption tunnel, shock absorption design point of view and the specific measures of the basic shock absorption tunnel.
Keywords: Tunnel; Design; Seismic; Shock absorption

The design of the seismic tunnel
At present, earthquake of the tunnel the basic calculation method on the tunnel in earthquake, in accordance with the characteristics of buildings can be divided into two kinds. They are dynamic method and static method. Because static method to calculate the one-lane tunnel seismic resulting with a number of macro damage is close to the investigation. To strengthening its anti-seismic measures and scope of the non-seismic area tunnel lining comparison, it is generally reasonable, and the static method is simple. Given the current pressure on the tunnel theory needs to be further explored, therefore, the use of seismic checking more accurate calculation of methods is little or no practical significance, we still use the past used the static method of the earthquake.
Greatly increased the stiffness of the tunnel structure, which is made of rigid structure, the structure of such a tunnel is close to the ground structure response in earthquake. The deformation of the tunnel structure is subject to the deformation control, and rock is the main role of the shearing deformation. The deformation of the ruler is that upper is big, and lower is small. So when a rigid structure is used, the structure of the tunnel is bound to bear a greater load. In order to increase the rigidity of the tunnel structure, is bound to increase the amount of material, which would increase the quality of the tunnel structure, and seismic load will also increase. Clearly, using a rigid structure is neither economic, and also is in risk of damage.
At present, China's railway tunnel used this method. The tunnel entrance, and bias in shallow lots, lots for seismic fortification, the lining of the structure should be strengthened. When the design strength is 7 degrees, the rock category Ⅳ and Ⅴ of the two-lane tunnel, or when the design of the intensity is 8 degrees and 9 degrees, the four types of single-rock and rock category Ⅲ and Ⅳ of the two-lane tunnel, maximum security are based on the length of the terrain and geological conditions identified. One-lane tunnel of the general security should be less than 15 meters, two-lane tunnel length of maximum security should not be less than 25 meters. Seismic fortification of the tunnel should adopt the structure with the inverted arch-wall lining.
The shallow, biased and broken in the fault zone, and other adverse geological section of the tunnel, should note lining behind cement mortar. This shows that China's anti-seismic measures of the tunnel is mainly through increased stiffness to achieve the lining.

The design of the shock absorption tunnel
In order to reduce the tunnel structure of the earthquake disaster, there are two ways that the seismic and shock absorption. In the past we often used seismic technology, which is by increasing the rigid structure of the tunnel to withstand earthquakes. But the structure of the tunnel follows the earthquake deformation formation of the force, such as improving the rigid structure of the tunnel. When earthquake happens, the tunnel structure will increase the internal force. Therefore, the tunnel structure of seismic design is only a means to solve the problem, but not the only means. Usually in the tunnel structure is set up special structures to reduce earthquake structure of the internal forces of the tunnel, which is also a good method, the so-called shock absorption method.
Seismic changes the performance of the tunnel structure itself (stiffness, quality, strength, damping, etc.), such as reducing the rigidity of the tunnel structure to make it easier to follow the formation of the deformed, thus reduce the response of the tunnel structure; damping at the tunnel structure is set up between the structure and the layer, so that the formation of the deformed is difficult to convey to the tunnel structure, and the tunnel structure of the earthquake response decreases.
The tunnel structure of the shock absorption, in general, has the following three categories:
To set up flexible joints and flexible configuration segment of the structure;
To reduce the shield tunnel joints rigid structure;
To set up the tunnel structure of the week.
Before these two kinds of tectonic earthquake is at the track, when the formation of structural deformation. The rigid structure is smaller to mitigate the earthquake took place in the force, and to structure flexible. At present the shield tunnel, the main use of this method is basically have a practical use. And a final structure, the structure is in the peripheral set and the surrounding formation is smaller rigid than the surrounding bottom of the damping materials. And the earthquake deformation formation is difficult to convey to the tunnel structure, thereby it reduce the impact of the earthquake, which is being constructed research and development.
This shows that the tunnel structure of the shock absorption technology has two kinds of ways. One is the decreasing of the rigid structure, which is able to track earthquake structure deformation, and the other is to stop the formation of the earthquake changes to the structure of transmission. The immersed tube tunnel, the shield tunnel, and other projects, have reduced the practical section of the technology. It is used in almost all installed on rigid body structure of a small device to reduce the rigid structures, so it can track earthquake formation deformation technology. Central flexible joints and reducing the rigid approach to the street, is a manifestation of this technology.
Shock absorption design point of view, in accordance with the basic design of shock absorption spectrum, is carried out. The structure of its major counterparts is the rigid structure, and corresponding to the main shock has high frequency, high acceleration and the short duration of the shock. The main purpose is to ensure the tunnel structure of the internal security personnel and equipment, not to require the use of multiple layers shock absorption, and demand that shock in a layer is in plastic. So this is a one-time shock absorption design. In other words, this is just protective shock absorption, which varies with the seismic shock absorption.
Shock absorption is the general structure of the tunnel to ensure its stiffness in the circumstances. In the tunnel between the rock and the structure is set up damping device, adjustable damping device stiffness, and a damper. When earthquake happens, damping device can consume massive energy of earthquake, so that the transferable energy of the tunnel structure in the earthquake will decrease, and the tunnel structure of the earthquake response will be greatly reduced.

References

1.Shubao Guan,2003, The tunneling design wants the set of points, China Communications Press
2.Dewu Li,2004, Tunnels, China Railway Publishing House
3.Shouping Shang,2003,Structure seismic design, Higher Education Publishing House
4.Qinghuo Zhang,2002,Subway and light rail, People's Transportation Publishing House
5.Shubao Guan,2003,The tunneling construction wants the set of points, China Communications Press
6.Weiming Hong,2004,Underground structural design principle and method, Southwest Jiaotong University Publishing House

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2008-06-28

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