Abstract
It is necessary to study the problem of seismic wave scattering in composite stratum for tunnel engineering because the existence of composite strata will make the stress of tunnels more complicated during earthquakes. In this thesis, a series solution of the scattering wave field of the composite strata and lining is obtained using the complex function method. According to the stress and displacement boundary conditions between the composite stratum and the lining, a series of equations are established and are solved by means of Fourier transformation and finite term truncation, and the calculation errors are also discussed. Through programming calculations, the dynamic stress concentration factor (DSCF) of circular tunnels in the two types of composite strata, “hard-over-soft” and “soft-over-hard,” is analyzed when SH waves propagate, and certain conclusions on the scattering of SH waves that are distinguished from the case of single homogeneous layers are reached. The research in this article reveals some phenomena. For the Q345 steel lining in the calculation examples, it is found in this paper that increasing the thickness of the lining is effective to reduce the influence of the DSCF. But, for C30 concrete, increasing the thickness of the lining reduces the DSCF of the outer surface while increasing the DSCF of the inner surface.
Highlights
Urban lifeline projects such as subway tunnels, water supply and drainage pipelines, and natural gas and oil pipelines are important components of urban structures and are effective means to solve urban land shortage and relieve traffic pressure
Rock vibration is propagated in the form of elastic waves through the particles of the rock. e destructive consequences of earthquakes are directly or indirectly related to seismic waves. at is why the study of seismic waves has become the basic work of studying and predicting earthquakes
When the composite stratum is “hard-over-soft,” the stability of the lower soft soil is higher because the upper hard soil layer supports the lower soft soil
Summary
Urban lifeline projects such as subway tunnels, water supply and drainage pipelines, and natural gas and oil pipelines are important components of urban structures and are effective means to solve urban land shortage and relieve traffic pressure. E composite strata bring many technical difficulties to the construction of the tunnel and cause great difficulties in the study of seismic waves because the mechanical parameters of the composite strata are variable and the scattered wave fields of the various soil layers interfere with each other. E research on the elastic wave scattering of tunnels lined with composite strata is of important engineering significance. The stress at the edge of the tunnel will suddenly change, resulting in dynamic stress concentration Analytical methods such as wave function expansion method, integral equation method, and asymptotic matching method and numerical methods such as T matrix method, singular boundary method (SBM), and finite element method are all important methods for studying elastic wave scattering problems [15,16,17,18,19,20,21]. On the basis of theoretical derivation, two typical examples—concrete and steel-lined tunnels in composite strata—are analyzed. e frequency of incident waves, soil layer and lining parameters, lining thickness, and other factors affect the dynamics of the lining
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