Seismic Response Of Permeable Tunnel With Ribbed Arch Beam

The permeable tunnel with ribbed arch beam is a semi bright and semi dark,ribbed arch beam shaped tunnel structure that adheres to the concept of "safety,environmental protection,comfort,and harmony",which can avoid large-scale excavation of slopes and has a novel and beautiful structure.However,due to its special terrain conditions,after the excavation of the tunnel near the mountain to form the cavity,it is basically a semi bright and semi dark structure,and due to its shallow burial depth,it is generally located in fully to strongly weathered rock layers,with well-developed joint fissures.Compared with traditional tunnels,it has the characteristics of thin roof cover,steep ground cross slope,low surrounding rock category,and asymmetric bearing capacity of the tunnel body.Moreover,the influence range of tunnel excavation extends to the surface,and the tunnel surrounding rock cannot form a "natural arch".The generated loose pressure of the surrounding rock will directly act on the tunnel structure in the form of gravity,affecting the stability of the tunnel.Based on the near-field wave theory,this article uses numerical simulation methods to study and analyze the seismic response of a fully ribbed arch beam tunnel,in order to obtain the seismic response law of a fully ribbed arch beam tunnel.The main research and achievements are as follows:(1)Through Abaqus finite element software,based on the function of the birth and death element in Abaqus and the automatic crustal stress balance method,the three-dimensional model of the static excavation and support of the slope is completed.The tunnel stress,displacement and slope safety factor under the static state are analyzed.The results are as follows: the maximum pressure stress area of the tunnel is concentrated in the left arch foot,and the maximum stress area gradually decreases to the left arch waist and inverted arch,and the rib arch beam only plays an auxiliary role in the support,The main deformation occurs in the hardened area of the advanced support surrounding rock,while the displacement of the remaining parts is relatively small.(2)Based on Abaqus finite element software,the addition of viscoelastic boundary conditions was achieved by writing Fortran language.Two types of ground motion modes,vibration input and wave input,were analyzed and compared.It was found that the stress and displacement changes under the two input modes were basically the same,but the wave method responded earlier than the vibration method.Therefore,a simpler vibration input method was chosen.On the basis of static analysis,the acceleration,lining stress,displacement time history,and slope safety factor analysis of the fully ribbed arch beam tunnel were completed.It was found that the peak acceleration values of each part were slightly delayed compared to the seismic peak values due to the influence of medium damping and time effects,and the peak acceleration values on the right side were generally higher than those on the left side.The stress of the left lining is generally higher than that of the right side,and tensile stress occurs in all parts except for the left arch foot.The right side is mostly in a state of tensile stress.The various parts of the lining move synchronously,and the displacement time history of all parts is basically the same except for the right arch waist.After reaching the peak,it decreases,and the values are all on the millimeter level.(3)Analysis of the sensitivity of seismic response parameters for through-ribbed arch beam tunnels was conducted,and various influencing factors such as seismic amplitude,frequency spectrum,duration,and surrounding rock lining parameters,lining stiffness,lining thickness,geological conditions,and seismic absorption layer were discussed.The relevant laws of seismic response for through-ribbed arch beam tunnels were summarized as follows:under the influence of seismic amplitude,frequency spectrum,and duration,The slope acceleration is more sensitive to changes in the amplitude spectrum,and only slightly increases compared to the increase in seismic duration.The tunnel lining itself has the characteristic of bias pressure,and the stress and distribution in different parts of the lining exhibit different sensitivities to seismic parameters.For the safety factor of the slope,the failure mode of the slope changes from sliding surface instability under static state to surrounding rock lining dislocation failure instability.After changing the seismic parameters,the displacement response of the slope failure is rapid.