ANALYSIS OF TWO ADJACENT TUNNELS IN SOFT CLAY SOIL

Gouda A. M. Attia, Eman A. M. Elshamey, Hesham M. F awzy, Khaled Abdul - hafez

Abstract


The design of tunnel cross sectiondepends on the values of internal forces and deformations induced in the lining.These values are influenced by many factors such astype of soil, method of construction and dimensions of the tunnelcross section.In the present study, a numerical analysisis proposed using finite element software Adina version 8.5 (Afinite element code for soil and rockanalyses).A numerical model is presented as a plane strain problem with twodimensions element of specific-node to present the soil elements andspecific-node beam element to simulate the liningof thecircular , elliptical ,andhorse shoetunnel. The material of the lining was chosen as a reinforcedconcrete beam.The properties of the selected soil areas constantproperties with an elastic linear model involvetwo elastic stiffnessparameters: Young's modulus(Es) and Poisson's ratio (ν). With this numerical model, the horizontal and verticalboundary dimensions,as well as the interaction between the two tunnelsparallel twins, according to the distancebetween the central lines of the tunnel;was also studythe effect of the change instiffnessofsoftclay soils using thethree valuesof the modulus of elasticity (Es) and the Poisson ratio (ν). The effect ofthe thickness-radius ratio(t/r)onthedisplacementtunnelunder theground surfaceat a depth 6 timestheradiusof thetunnel from the surface of thegrounduntil the center of the tunnel,also obtained the best shape tunnel in soft clay soil with different values for (Es)and(ν).Effect of three types ofsoft claysoil on the values of internal forces anddisplacementinducedin lining hasbeen determined. These typesdepend on values of (Es) and(ν).Comparisons between the values of the bendingmoments as well as thesettlement inducedat the horizontal line of the tunnel cross section with the maximum valueshave beendetermined. Designcharts for the bending moments as well assettlementto predictthe maximum bendingmoments as well as the maximum normal forces induced in the lining have beenintroduced.

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