Study Of Image Theory And Application Of Regression Method On Tunnelling Induced Soil Displacements And Stresses

Shield tunneling is a necessary construction method in subway construction,comparing with other methods, shield tunneling has many merits, but inevitableeffects on the soil and buildings around the tunnel will still occur. This paper firstlyintroduce image theory to the 3-D calculation and analysis on the soil displacementsand stresses based on the observed results of TianJin underground railway project.Image method is an elastic analytic method origin from capacity assumption,comparing with finite-element method, image method can avoid the complex modelconstruction process and can be used more portablely;comparing with experimentalmethod, by using image method both qualitative analysis and quantitative calculationcan be proceeded and more complete results can be obtained. Based on image methodresults, the damage level of surface buildings can be predicted and the influencingrules of main damage factors can be acquared. Furthermore, the capacity assumptionpresented by Peck is extended in this paper and it is initiated that researchers canstudy the width parameters of the settlement troughs with different depths throughanalyzing the settlements above the center line of the tunnel, then the practicalequation used to calculate soil settlements above the tunnel is gotten. The contentsinclude:(1) Site measurements, including levelling survey and inclination survey, areproceeded and the first-hand data of soil displacements in TianJin undergroundrailway project are obtained.(2) Image theory is introduced to the 3-D calculation and analysis on the soildisplacements and stresses, the distributions of soil displacements and subsidiarystresses in the procedure of TianJin subway construction are gotten.(3) Image method is used in other national and foreign tunnelling engineerings andit's applicability on calculating tunneling induced surface displacements isverified furthermore.(4) Based on image method results, the damage level of buildings caused bytunneling is predicted and the influencing rules of main damage factors arestudied.(5) The capacity assumption presented by Peck is extended and by using regressionmethod the width parameters of the settlement troughs with different depths arederived from the settlements above the center line of the tunnel, so the practicalequation used to calculate soil settlements above the tunnel is given.The study indicates that the image method results are in good consistence withobserved results of TianJin subway engineering and other national and foreigntunnelling engineerings, the image method provides a new thought and solution to thecalculation and analysis on tunnelling induced soil displacements and stresses. Byusing image method , the damage level of buildings can be predicted and the mostunfavorable locations where the damages occur can be defined. Moreover, theregression method provides a portable solution to the calculation on tunneling inducedsoil settlements, it's reliability is certified by the calculation on the case project andthe comparing with image method results.