Study On Deformation And Force Characteristics Of Deep-buried Large Section Expansive Red Clay Tunnel

Railway is the aorta of the national economy,in recent years,the emergence and large-scale application of high-speed passenger dedicated line has played an important role in economic and social development,tunnel engineering is an important way to cut straight and reduce the expanding coefficient,and the time and space distribution characteristics of the stress mode of lining structure are the important basis for optimizing the structure design of lining.Therefore,the article takes Yinchuan-XI'an high-speed railway qingyang tunnel in 2#work area surrounding rock and lining structure as the research object,through data collection,laboratory test,field test and Abaqus finite element simulation and other means,The time-space distribution characteristics of deformation and stress of tunnel lining structure with large section excavated by three-step method through Pliocene red clay stratum are studied.the following research results are obtained:(1)Tho 3tudy area red cloay belongs to the Neogene red clay(Nerz)the whole fine of the soil particles is the secondary red clay category of wind deposition,the pore is less,the cementing ability between the particles is extremely strong,the soil is extremely hard,because of the consolidation pressure and the long consolidation history,the layered joint characteristics can be observed obviously on the saturated immersion fracture surface It is proved that there is a trend of partial sedimentary diagenesis of red clay in this layer.With the increase of water content,the internal friction angle decreases and the cohesion force decreases.At the same time,the expansion potential is affected by the initial water content,and the lower the initial water content,the greater the expansion potential.(2)The pressure of surrounding rock shows the law of"rapid growth-violent fluulution slow growth-stable",the pressure of horizontol surrounding rock is greater than that of vertical surrounding rock,the internal force of lining structure shows the law of'rapid growth-slow growth-stable",the position of vault and the position of arch foot of both sides of the side wall appear stress concentration The lining structure of the large section tunnel is not an conceptual pressure ring model,but a balanced process between the supported part and the multiple stress redistribution of the surrounding rock,in which the locking bolt has a significant effect on the stress state of the lining structure.Because the pressure of horizontal surrounding rock is greater than that of vertical surrounding rock,the pressure state of surrounding rock is Causes the convergence on both sides to be greater than the vault settlement(3)The lining structure in the unclosed and closed junction position appears a large stress concentration,Consideration should be given to the placement of temporary inverted arch at this location.,the anchor force is small,does not play an ideal restraint role can be considered in the soil tunnel cancellation system anchor;The influence range of excavation on settlement process is approximately 1.5 times of that of Tunnel diameter,and the influence outside the scope is small.The face of the tunnel begins to produce severe deformation 1/2 times of that of the undiscovered part,and the influence amplitude decreases uniformly after the excavation.The measured settlement is roughly 1/2 of the total settlement of surrounding rock Comparing the stress and deformation characteristics of the lining structure of full section two steps,double-guide tunnel and CD method,Considering the construction period and other factors,the two-step excavation method is recommended for this stratum tunnel.