Study On The Calculation Models Of Key Parameters Of The Epb Shield Machine In Sandy Cobble Ground

Based on the sandy cobble ground conditions in Beijing and other shielding casesat home and abroad, the key parameters are analysed by means of theoreticalderivation and numerical simulation, so are established the mechanical model of thekey parameters. The adaptability of EPB in the the sandy cobble ground is analysed.At first, the engineering geological conditions in Beijing are summed up, and thesandy cobble ground is assessed in the physical and mechanical terms of the graindistribution, compactness, permeability and compressive strength, and the types ofshield suited to sandy cobble ground are summarized. From the characteristics of bothgeometry and operating of the shield, the calculation model of earth pressure suitablefor the sandy cobble ground is confirmed, and the mechanical models of the torqueand thrust force of the shield are established, the components and factors of which areexplained; The abrasiveness of the sandy cobble ground is determined from theLCPC,CAI and X-ray diffraction mineral content analysis, and the abrasiveness of thesandy cobble ground is rated from the correlation among the three experimentalresults, and the relation between the LAC value and the tool wear is also determined,which provides theoretical basis for the time determination of tool replacement inoperation; According to the field experiment, it is concluded that the mixture ofbentonite and foam is the best in improving the ground, and the void distributions of the ground after improvement are obtained by CT scanning, and it was found that thevoid ratio is reduced dramatically, which gives proper suggestion to the operation inthe sandy cobble ground.