| Due to its complex and changeable geological conditions,soft and hard composite strata bring a lot of difficulties for shield tunneling construction,and the force problem is the root of those difficulties.In this paper,the problem of rock breaking by disc cutter in the interface of soft and hard rock is studied by means of experiments,which can provide theoretical reference for the design and construction of shield machine.The main contents of this paper are as follow :(1)Through theoretical study and data collection,the mechanism of rock breaking with disc cutter is analyzed,and the engineering characteristics of soft-hard composite strata are summarized.(2)Based on the theory and technology of rock simulation,the whole process of simulation test,including determination of simulation standard,material selection,mixture ratio design and test,is studied.On the basis of this,a soft and hard composite strata model is made,and its fabrication and testing methods are summarized.(3)According to the working condition of shield cutter head,the linear cutting experiment of rock breaking with disc cutter at the interface of soft and hard strata has been designed and carried out.The experimental results show that in the process of cutting from soft rock to hard rock,there will be an influence zone in the front and rear range of soft and hard interface.In this range,the rock breaking force will fluctuate obviously.The rock breaking force fluctuates in different stages of cutting.(4)In the process of rock breaking repeatedly at the interface of the hard and soft strata,the diversity of peak normal rock breaking force between soft and hark rock remain about30%,at the beginning;when the process comes to crack and breakage,the diversity reaches about 80%,which is close to the strength difference of the soft and hard rock. |
