Study Of Excavation Methods Comparative Selection And Mechanical Equipment Coordination For Large-sectional And Water-bountiful Loess Tunnel

In order to improve the level of economic and social development in the western region, consolidating national defense, our country is carrying out a wide range of infrastructure construction in the Western region. Construction of loess tunnel faces many challenges, traditional excavation methods and equipment have been sufficient to ensure safe and rapid construction of loess tunnel, so it is necessary to optimize construction method of excavation of tunnel in loess to determine loess tunnel equipment scheme.According to Wang Jiagou loess tunnel of passenger dedicated line from Baoji to Lanzhou and Lianhuo highway as 2# of Dingyuan loess tunnel engineering, the main work and results are as follows:(1)The theoretical analysis of moisture content on the influence of loess internal friction angle, cohesion and tensile strength. Moisture content is less than 15%, the rate of angle of internal friction decrease fast, moisture content is 15% ~ 20%, the internal friction angle is not change with moisture content, moisture content is more than 20%, the rate of angle of internal friction decrease more fast; the effect of moisture content on the cohesion close to linear relationship, with the increase of moisture content, the cohesion of the straight line decreased; the effect of moisture content on tensile strength close to inverse curve, moisture content for 11% is the cut-off point of curve.(2)According to Wang Jiagou lo ess in situ sampling for laboratory tests, the results of the analysis on data are as follows: interna l friction angle of 22.33, the cohesion of 29.8kPa, plastic limit ωp of 16.5%, liquid limit ωL of l 31.95%. Plasticity index IP of 15.55, vertical elastic modulus of 160.4MPa,elastic modulus level of 87.5 MPa.(3)Of Wang Jiagou tunnel DK983 + 892 section of site monitoring measurement data is analyzed, from the point of deformation, the main features are: large amount of deformation and initial deformation rate faster in the early time. The maximum pressure of surrounding rock was in the left arch foot, 445.40kPa; the maximum stress for the steel arches appear in the right haunch, 242.46MPa; maximum contact pressure was in the right arch, 944.75kPa; the maximum compressive stress of concrete was in the right haunch, 20.17MPa; Most of the steel bar meter instrument is damaged, the data does not have a reference. Comprehensive analysis of the above results, the maximum monitoring project was right arch waist or right arch foot, Wang Jia Gou tunnel may be in the mountain state bias.(4)According to the results of the deformation characteristics of large section loess tunnel, on deformation control measures for optimization analys is, to Wang Jiagou Tunnel DK983+892~DK983+922 section, on different of excavation construction method, and different of excavation order and the temporary support form, and different lengths of excavation steps, and different lengths of excavation footage for three dimensional numerical simulation optimization analysis, CRD method for excavation is suitable, and excavation order should for left- upper 、left- middle、left- lower 、right-upper 、right- middle 、right- lower. and temporary support form should for arched, and 3 m steps length, and excavation of 0.6m footage.(5)According to the 2# of Dingyuan loess tunnel engineering,based on the studying of the construction machinery and equipment selection,research concluded that the loess equipment selection are: 1.2m~3 shovel digging、3.4 m~3 loader、15t dump truck、CSS3 concrete spraying manipulator、90 m~3/ h of Lining concrete mixing station、full-section hydraulic trolley、27.2m~3/min sul air ventilation equipment type in United States.(6)Through comparative analysis of different forms of excavation, machinery fuel and labor costs account for a large proportion of the cost of excavation, with the increasing mechanization of excavation, mechanical share of fuel cost increases. In order to save resources and reduce costs, we select tunnel equipment by selecting a high degree of mechanization and high utilization of machinery.