| Guiyang metro line three eight blocks is complex in geological conditions,the interval of weak surrounding rock,along the various architectural structures,such as:schools under wear,your yellow road viaduct and under construction in the concert hall,the ground buildings standing,construction difficulty coefficient is big,lead to have stringent requirements on the construction method,this method of excavation engineering require the use of cantilever machine for steps.The cantilever roadheader has the advantages of small damage to surrounding rock,continuous and smooth excavation surface,minimal excavation disturbance and noise,and almost no impact on the residents and buildings on the ground.Based on the three line segments between Huaguo Yuan east to Huaguo Yuan west engineering practice,with the help of three-dimensional large geotechnical calculation software FLAC3 D finite difference for standard double,single line tunnel for cantilever machine and construction method for numerical simulation analysis,it is concluded that the cantilever machine for urban subway construction in weak rock has a good adaptability,the main work and research conclusions are as follows:(1)Based on the actual site of the flower section,the cutting mechanism,cutting mode and applicability of the construction of the cantilever roadheader are analyzed,and the environmental factors that affect the construction efficiency of the cantilever roadheader are analyzed,and the reasons and advantages and disadvantages of the construction of the cantilever roadheader are summarized.(2)The gradient load release method is used to carry out the numerical simulation of the mechanical effect of the cantilever roadheader construction,an d the exponential time lag function is used to carry out the three-dimensional si mulation of the dynamic loading for the FLAC3 D dynamical calculation module blasting method construction.Based on the analysis of the displacement field,str ess field,plastic zone and vibration velocity of surrounding rock in the process of tunnel excavation and support under two kinds of construction methods with different levels of surrounding rock,the mechanical effect of surrounding rock un der cantilever tunneling machine construction is studied.(3)from the theoretical level to explain the concept of loose circle,and introduces the properties and classification of the loose circle,combined with FLAC3 D numerical simulation analysis of the plastic zone of surrounding rock loose circle process are analyzed,and the acoustic logging tool and the geological radar measuring the scope of loose ring,using Mohr-Coulomb theory,unified strength criterion calculating the size of the loose circle,introducing considering disturbance of blasting damage factor D Hoek Brown-criterion in calculating method of surrounding rock loose circle theory.Based on numerical simulation,field measurement and theoretical calculation of the size and formation process of the loose circle,the disturbance range of surrounding rock for cantilever roadhead construction is determined,and the strength criterion applicable to Guiyang area is obtained.(4)Analyze the support mechanism and support objects of the soft rock loose ring based on the support theory of the loose ring,and caculate the theoretical length of the anchor rod with the help of the disturbance range of the surrounding rock in the construction of the cantilever roadheader determined by the suspension theory,using FLAC3 D The software performs numerical simulation on the theoretical bolt length,and compares and analyzes with the on-site support plan,which verifies the feasibility of the optimized plan. |
