The Study Of The Influence Of Longitudinal Joint Nonlinearity To Seismic Response Of Shield Tunnels

As an important transportation tool in modern cities, underground urbanrail transit plays a very important role in the development of social productionand urban people’s lives. Domestic and foreign historical earthquakes haveshown phenomena many times that underground rail transits might be destroyedunder strong-level temblors. And the event that once underground rail transitsare devastated by an earthquake will cause huge traffic impact and economiclosses. As the most common type of tunnel structures used in underground urbanrail transits, shield tunnels generally utilize bolts as segment joints to connectcomponents in both circumferential and longitudinal directions. It has importanttheoretical significance and highly value in engineering to study mechanicalproperties, the process and characteristics of the nonlinear earthquake responseof pipe pieces and joints.In this paper, to obtain the curve reflects seismic characteristics ofstructural mechanical behaviors, the fiber model is used to simplifybeam-modeling and analyzing shield tunnel segments which considering thelongitudinal joints. And this curve is utilized to analyze the influence of jointsnonlinearity on the overall longitudinal seismic response.The main works of this paper consist of four aspects listed as follows:1. The fiber model is used to simplify beam-modeling tunnels segmentsconsidering longitudinal joints and tensile or compressive spring units which areequivalent to joint bolts and concretes. And the material nonlinearity of concretesegments and steel joint bolts is also taken into account. The curve whichreflects nonlinear seismic characteristics of structural mechanical behaviors isobtained through imposing the axial tension and compression on structures.2. Based on the local modeling of circumferential shield tunnel segmentswith the general purpose finite element software, the analysis of the stress stateof both bolts and concretes in contact areas are carried out. The possibility ofdamage of bolts in the local tension state is discussed.3. Several main methods of the computation of soil parameters inconsideration of the seismic response displacement method are summarized andevaluated. Equivalent spring parameters of the soil around the tunnel arecalculated by taking advantage of three-dimensional modeling in accordancewith the information of relevant soil parameters and considering nonlinearcharacteristics of the soil under the action of a terrible earthquake.4. According to equivalent soil spring parameters, the curve reflects seismiccharacteristics, beam-modeling of the overall tunnel and the longitudinalresponse displacement method, structural reactions of the shield tunnel indifferent seismic loads are deduced after respectively imposing a longitudinalwave and a horizontal transverse wave on structures along the tunnel axis. And the process and nonlinear areas of tunnel segments and bolts in seismic loadsfrom small to a huge level are also summarized.