Study On The Seismic Performance Of Tunnel Intersection

With the social economic rapid growth and increasing scale of the city,the limited traffic network on the ground already can not satisfy people’s needs.Therefore people change traffic engineering construction into underground. In the underground traffic network,tunnel engineering interflow with each other, even can form a complex form of "overpass" underground. In the form of various cross,the frequency of tunnel intersection is higher and higher.The intersection’s cross is large,lining stiffness changes a lot,loading is complex.It is the weak part if tunnel stability.In recent years,the world goes into the earthquake period.China is a frequent earthquake country,the earthquake dynamic effects on the intersection can not be ignored.Ensuring the intersection stability in the earthquake is particularly important.But,Chinese current seismic specification about tunnel engineerings working conditions which cross each other is very brief, unable to play the role of guiding the design and construction. The dynamic response analysis of tunnel intersection is great significance.The article selects the tunnel intersection as the research object, using the large finite element software ANSYS,researching and analysing the tunnel intersection’s regularity of dynamic response under seismic action and the influence of lining stiffness on the structure dynamic response. The main contents include:1. In the three kinds of section form lining stress analysis, the horseshoe intersection local appear smaller tensile stress in lining;Circular lining at the waist, spandrel arch tunnel intersection appear larger tension stress;Straight main bifurcation tunnel side wall arch tunnel lining spandrel arch and ramp lining a larger waist and spandrel tensile stress.The cross section of tensile stress area is easy to appear the tensile damage and loss of stability.2. Under the action of static, tunnel intersection adjacent sides of two tunnels’ boundary of the surrounding rock pressure arch within are far away from the tunnel contour, the stability of surrounding rock was poor.3.Under the action of earthquake,horseshoe section tunnel intersection’s dynamic response comes down from the vault to bottom in turn.The spandrel, feet,vault and bottom appear tensile stress.The right side spandrel of the main tunnel and the ramp vault’s tensile stress range is the largest. The spandrel between the main tunnel and the ramp are local tensile failured.The maximum vibration velocity of lining during the Ⅷ earthquake is more than the safety value stipulated in the codes.4. In the dynamic analysis of the tunnel intersection,the results are intuitive by the tunnel surrounding rock pressure arch and the surrounding rock pressure relief area.The theory of tunnel surrounding rock pressure arch can determine surrounding rock’s dynamic stability condition.5.Changing the lining concrete materials, concrete grade, the thickness of the lining as the measures of tunnel resistance and shock absorption,the article suggest that under the premise of the specification requirement the ceramsite concrete can take place of the common concrete.And the vault and spandrel of the lining choose high grade concrete,the bottom and the foot choose lower grade concrete,lining thickness is 70~100cm.