Abstract：By in-situ monitoring in Beijing metro，Shenzhen metro，Xiamen subsea tunnel，and Xiamen airport road tunnel etc.，its found that there are big differences between urban shallow-buried tunnel and mountain one both in stratum deformation and rock wall pressure. Upper strata in city tunnels subside as a whole，and the subsidence develops more suddenly and devastatingly. Faced with these complex situations，a new model for stratum slipping and cracking is established，and the deduced results show that stratum slipping angle is 15° higher than traditional one，thus relative slipping surface is steeper，closer to vertical direction. And the slipping angle is a function of rock properties，stress fields，tunnel depth versus span，and rise-span ratio，which to some extend testifies that the deformation and failure of rock wall embody scale effects，thats to say，the geometrical properties of rock wall jointing with mechanical parameters will call for stratum integral subsidence，collapse，and roof fall behavior. Besides，soil below tunnel structure，being disturbed，damaged，and softened，may easily drive under-stratum into subsiding and losing bearing capacity，further bringing integral subsidence of supporting structure，and finally sharpening integral subsidence of upper-stratum. Correspondingly ideal elastoplastic model and modified Cam-Clay numerical model can partially lead to the similar conclusion. Synthetically research shows that its vital necessary to acknowledge urban shallow-buried tunnel from rock wall mechanical behavior and its constitutive law.
