| Pebble stratum can be used as a good bearing stratum,but its cohesion between particles is low and it is very sensitive to deformation.Therefore,when excavating Metro Tunnel in pebble stratum,the prediction of ground settlement and the study of settlement law and mechanism can reduce construction risk and property loss.In this paper,22 representative rock stratum sections in the pebble stratum section of Urumqi Metro Line 1 are selected.The following three aspects are mainly studied:(1)In this paper,the basic principle of probability integral method and the characteristics of pebble stratum of Urumqi Metro Line 1 are studied.The origin,distribution,physical and mechanical properties of pebble stratum are analyzed,and the average value of uniaxial compressive strength of each stratum related to the calculation of parameters of probability integral method is determined.(2)This paper calculates the parameters of probability integral method according to the characteristics of pebble stratum,and uses the software of MATLAB to program the formula of probability integral method.Taking 22 typical sections of pebble stratum of Urumqi Metro Line 1 as the prototype,the surface settlement values caused by single-hole tunnel excavation and double-hole parallel tunnel excavation with spacing of 13 m in pebble stratum are predicted respectively,and the law of surface subsidence of pebble stratum and the variation rule and range of parameters of probability integral method are summarized.(3)Using MIDAS/GTS NX software,this paper establishes the numerical geological model of single-hole tunnel and double-hole parallel tunnel,verifies the operability and simplicity of probability integration method in surface subsidence prediction,and analyses the settlement mechanism of pebble stratum.The above research contents and results can provide an important reference for the ground subsidence and risk control of Metro Construction under similar conditions in Urumqi. |
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