| With rapid development of China’s urban infrastructure construction,subway brings good social and economic benefits with its environmentallyfriendliness and high efficiency, and is gradually becoming main body formodern urban transportation. Restricted by objective conditions, subwaytunnels commonly adopt two holes parallel tunnel form, with small distancebetween nearby tunnels, and evident inter influences. Hence, a series ofcomplex problems such as surface subsidence, ground housing cracking, andtunnel over-large deformation occur. Given the universality and complexity oftwo holes parallel tunnel digging problem, and superficial research upon it,developing the research on urban subway two holes parallel tunnel interinfluences and surface subsidence impact, is of theoretical significance andengineering application value. The paper adopts various methods ofmathematics, mechanics, numerical analysis, field measurement analysis toconduct research, including the following seven aspects:(1)Utilize analytical continuation of complex variables function, considertunnel support force, deduce the stress value and displacement valueanalytical solution of the underground half space arbitrary shape and arbitrarysetting single hold tunnel in elastic half space at an arbitrary point; take roundtunnel as special case under simplified conditions, calculate the stress valueand displacement value analytical solution concrete explicit formula of anarbitrary point in elastic half space.(2)Utilize complex variables functions Cauchy integral test, combinewith optimized theories, deduce the stress value and displacement valueanalytical solution formula of an arbitrary point in elastic half space of thesingle heart round inverted arch U-shape tunnel at underground half spacesection, and verify the correctness of the formula via finite element method.(3)Utilize analytical continuation of complex variables functions andSchwarz alternating method, solve surrounding rock stress and displacement after half infinite plane arbitrary form two holes tunnel digging, under theinfluence of digging sequence, virgin rock stress, tunnel duct piece normalforce. Simplify to two holes parallel round tunnel in half infinite plane,present surrounding rock stress and displacement concrete formula, and verifyvia finite element method.(4)Utilize double tunnel analytical solution formula obtained from above,conduct parameter sensitivity analysis, and study the influence of tunnelradius, tunnel spacing, virgin rock stress, tunnel duct piece normal support ondouble tunnel surrounding stress and displacement. Analysis shows that thechanges of virgin rock stress have huge influence on tunnel surrounding rockstress value and displacement; next comes the influence of center distancebetween tunnels; and last are the influence of tunnel radius, duct piece normalsupport.(5)Establish three-dimensional numerical model, study the interinfluences of asynchronous syntropy digging and synchronized syntropydigging, and discuss the features of section convergence curve. Results show,different two holes tunnels distributions have different influence distance anddifferent convergence curve features.(6)Establish three-dimensional numerical model, analyze the rulessurface subsidence and soil deformation around the tunnels caused by twoholes tunnel synchronized digging in the three distributions of two holesparallel, vertical overlap, tilted overlap. Analyze the influence of differenttunnels distributions, spacing, depth on two holes tunnel digging. Resultsshow, vertical distribution has the biggest impact on tunnel construction,tilted distribution has less impact, and horizontal distribution has the leastimpact. With the increase in tunnel spacing, the inter influences of the twotunnels become smaller. With the increase in tunnel depth, the impact ontunnel construction grows.(7)Take Shenzhen Line3Subway as project background, establish valuemodel, analyze the impact of tunnel digging sequence on surface subsidence,under the three conditions of two holes vertical overlap (regardless of building load), tilted overlap (regardless of building load), vertical overlap(taking building load into consideration), proposes rigidity correction methodfor two holes subway tunnel surface subsidence, compare calculation valuewith actual measurement value, and analyze rules of urban subway two holestunnel surface subsidence. Results show, for tilted overlap or verticaloverlap distribution two holes tunnels, it is better to adopt digging sequenceof lower cave first, upper cave later so as to reduce surface subsidence.The analytical solution of the paper expands the application of complexvariables function analytic continuation method, promote the development oftunnel mechanics theory, and takes an important step for the successfulresolution to the complex form single hole and two holes tunnel diggingproblem. Numerical simulation analysis compressively studies the influenceof distribution forms, depth, spacing of two holes tunnel on tunnelconstruction, which possesses some engineering guidance significance. Thepaper also proposes rigidity correction method for calculating surfacesubsidence, taking consideration of various factors affecting surfacesubsidence. The calculation is simple and convenient, with engineeringapplicability and practicality. |
PDF Full Text Request