Experimental Study On Shaking Table Of Utility Tunnel Crossing Ground Fissure With 60°

Utility tunnel is a kind of modern,scientific,intelligent and intensive new municipal infrastructure,which is built in urban underground to accommodate two or more types of pipelines and ancillary facilities.Xi’an is located in the subsidence center of Weihe Fault Basin,and the ground fissure disaster is very developed.Up to now,there are as many as 14 ground fissure that have been proved,and they are distributed in the whole urban area in strips.As a kind of linear lifeline engineering,the planning and construction of utility tunnel in Xi’an area are bound to the bad geological condition of crossing the ground fissure.In addition,Xi’an is located in the Fen Wei seismic belt and belongs to the high intensity fortification area,so the seismic fortification of the utility tunnel structure has to be considered.However,the research on the seismic response law of the utility tunnel across the ground fissure section at present is relatively rare,which presents new problems and challenges for the construction of the utility tunnel.In view of this situation,based on the key research and development plan of Shaanxi Province "Research on seismic response and seismic mitigation measures of utility tunnel structure across ground fissure section(2017ZDXM-SF-095)",this paper,taking a double cabin utility tunnel structure in Xi’an urban road as the prototype,carried out a shaking table test of utility tunnel crossing the ground fissure with 60°.The seismic response law of the ground fissure site and the utility tunnel structure was explored.The main research contents and achievements are as follows:1.Based on the three similar theorems and dimensional analysis method,the shaking table test scheme of utility tunnel crossing the ground fissure with 60° is designed,developed and implemented from the aspects of model box and boundary effect,selection and manufacture of test materials,layout of measuring points,loading scheme,etc.2.The seismic response law of ground fissure site was analyzed and summarized from the aspects of surface fissure,deformation characteristics,acceleration response and vertical earth pressure response.The results showed that:(1)There are about 20 fissures with different shapes and lengths on the surface,and the development degree of hanging wall fissures is greater than that of footwall.(2)The vertical deformation of hang wall and footwall on both sides of the ground fissures is the largest and the horizontal displacement is the smallest.(3)The acceleration response characteristics of the surface and the bottom soil are different in the direction parallel to the vibration.However,in the direction perpendicular to the vibration,the acceleration response of the two is similar.With the increase of peak acceleration,the amplification coefficient of acceleration decreases continuously,but the curve reduction characteristics of different seismic waves and the reduction rate in each stage are different;(4)the vertical maximum earth pressure coefficient of soil presents the characteristics of "concave" curve.3.From the aspects of acceleration response,strain response and interaction between soil and utility tunnel structure,the seismic response characteristics of utility tunnel are analyzed and summarized.The results showed that:(1)The acceleration amplification coefficient of the hanging wall structure is always greater than that of the footwall structure,which is irrelevant the type and intensity of seismic waves.(2)The transverse and longitudinal strain responses of the model utility tunnel increase continuously with the increase of load level.The specific performance is that the transverse strain response of the top and bottom plate in sections of the hanging wall and ground fissure is greater than that of the footwall section,while the transverse strain at the top of middle partition wall is larger than that at the footwall section.The longitudinal strain response of the top plate at the hanging wall section is relatively large,but the longitudinal strain response of the bottom plate is larger at both the hanging wall and ground fissure section.And the longitudinal strain response of the footwall structure is smaller as a whole.(3)The closer it is to the ground fissure or the greater the peak acceleration is,the greater the maximum contact pressure coefficient is,and the stronger the interaction between the soilutility tunnel structure is.