| This paper takes the shield construction of Yaozhuang station Wenboyuan station section of Xuzhou Metro Line 2 as an example.There are many soft and hard composite strata in the shield section,and the construction is difficult.In the soft and hard composite strata,due to the large strength difference between the rock at the joint of the soft and hard strata and the angle between the hard rock and the tunnel strike,the inclination of the rock at the joint of the soft and hard strata increases in the process of rock breaking by the shield hob And the rock strength will have a significant impact on the rock breaking force of the hob.At the same time,the impact wear of the hob will affect the rock breaking efficiency.In order to study the mechanism of rock breaking and the change characteristics of rock breaking force of shield hob in soft and hard composite stratum,the penetration and cutting tests of hob were carried out with scaled two-dimensional wedge cutter to obtain the change data of rock breaking force of hob,and the numerical simulation of rock breaking by hob was carried out with numerical simulation.(1)Based on the analysis of the force and rock breaking mechanism in the process of rock breaking by hob,according to the action direction and characteristics of normal force and tangential rolling force in the process of rock breaking by hob,twodimensional wedge cutter horizontal cutting and vertical penetration tests are designed.The hydraulic servo pressure and self-made two-dimensional wedge cutter are used as the test device,and the acoustic emission device is used to monitor the rock breaking process.The horizontal cutting and vertical penetration tests of different rock dip angles and various factors are completed,and the relatively complete rock breaking force and acoustic emission response characteristics are obtained.(2)Compared with the cutting and penetration tests at different rates,the normal force is much greater than the tangential force in the process of rock breaking.With the increase of cutting rate,the maximum penetration jump load and cutting load increase continuously.There is a logarithmic function relationship between them and hob speed,but the load drop difference also increases.That is to say,in practical engineering,the speed of cutter head can be appropriately increased to improve the rock breaking efficiency,but it will increase the vibration of hob and cutter head.(3)In the process of hob transition from soft rock to hard rock,the greater the rock strength is,the greater the difference between the maximum jump load and drop load of hob at the soft hard interface is,and the tool vibration is obvious.When the dip angle of hard rock at the soft hard interface changes,the anti invasion coefficient of rock increases continuously.When the dip angle of rock is 15 degrees,the damage area in front of the hob is larger,and the rock breaking efficiency is the best.(4)Matdem software is used to simulate the rock breaking process of hob.The influence of cutter spacing on the rock breaking force of adjacent hobs is discussed and the optimal cutter spacing is determined.The influence of different rock dip angles on rock breaking force and rock breaking efficiency in composite strata is studied.The paper has 86 diagrams,12 tables and 91 references. |
