Application of the hottest hard rock tunneling mac

2022-08-23
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Application of Hard Rock TBM in soft rock tunnel construction

TB880E TBM produced by German Wirth company has been successfully used in the construction of Qinling line I tunnel on Xikang line. Since the value of the equipment is as high as 300 million yuan, in order to give full play to its role, we should actively explore its application in geological tunnels with weak surrounding rocks, so as to improve the utilization rate of the equipment

1. Characteristics of construction in weak surrounding rock zone

weak surrounding rock includes mica quartz schist, altered diorite, diorite porphyrite and fault fracture zone. Among them, the local bad sections of Qinling tunnel are altered diorite, diorite porphyrite and fault fracture zone; The local unfavorable geological sections of Mogouling tunnel are altered diorite, diorite porphyrite and fault fracture zone; The Mogouling tunnel is mainly composed of mica quartz schist and fault fracture zone with lower surrounding rock strength. Although this kind of surrounding rock has little wear on the cutting tools due to its low strength, its integrity is poor, the fault joint fissures are developed, and its self stability is poor, which is easy to cause collapse, thus increasing the difficulty of operation and construction. If the tunneling parameters are not selected properly, the collapse will be aggravated or the tunneling machine will be damaged. A large number of landslides will also affect the passing performance of the roadheader and cannot drive normally. At the same time, the weak surrounding rock is easy to change the heading attitude of the roadheader, and the heading direction is easy to deviate

2. Selection of tunneling parameters

(1) working mode

tb880e roadheader has three working modes: automatic thrust control, automatic torque control and manual control. Automatic thrust control is applied to homogeneous hard rock, and automatic torque control is applied to homogeneous soft rock. However, the unfavorable geological conditions of weak surrounding rocks are complex and changeable, and most of them are heterogeneous surrounding rocks. Therefore, although manual control has increased the requirements for operators, it can adapt to complex and changeable geological conditions. Experienced operators can judge the latest geological conditions in front of the cutterhead through various feedback information, and adjust the tunneling parameters in time to adapt to changeable geological conditions, which has more prominent advantages when accurate and reliable geological prediction has not been carried out, or there is deviation in geological prediction

(2) anti skid and anti break of the belt conveyor

if the surrounding rock in front of the cutter head collapses, the load of the belt conveyor will be very large. When the load exceeds a certain degree, the belt conveyor will slip or stop running. Because the 3 # belt conveyor is much longer than the 1 #, 2 # belt conveyor, the phenomenon of lead-in is more likely to occur. Especially when the 3# belt conveyor is transported to the muck chute, because the horizontal transportation is changed to slope transportation, too much ballast will fall into the inner side of the 3# belt conveyor, which may lead to the accident of belt tearing or breaking of the 3# belt conveyor. This phenomenon may occur when the pressure of 3 × belt conveyor exceeds 12MPa. Due to the sudden collapse of surrounding rock, the running speed of the belt conveyor is 2m/s, and the observation of the main control room monitor on the belt conveyor conveying system is limited to the joint parts of 1 # and 2 # belt conveyors and the joint parts of 2 # and 3 # belt conveyors and the unloading of the muck chute. When the existing belt conveyor has problems and responds, the belt may have been torn for 20 or 30 meters, so it should not be controlled by directly observing the pressure of 3 # belt conveyor, Otherwise, it will lag. When the pressure of 1 #, 3 # belt conveyor, especially when the pressure of 1 # belt conveyor rises from 12MPa to 14MPa, the propulsion speed should be reduced; When the pressure variation range of 1# belt conveyor is large, stop advancing or even retreat, and rotate the cutter head to discharge the slag to ensure the safety of the belt conveyor

(3) selection of cutter head speed

cutter head has two driving modes: electric drive and hydraulic auxiliary drive. Electric drive has two speeds: 5.4r/min and 2.7r/min; The rotation speed of hydraulic auxiliary drive is within the range of 0~1r/min, which can be controlled and adjusted as needed for the cutter head to get rid of difficulties

for the roadheader itself, high speed is more beneficial because: tunneling speed = cutter head speed × Penetration. At the same tunneling speed, the penetration of the cutterhead at high speed is half that at low speed, and the torque and propulsive force of the cutterhead proportional to the penetration are relatively small; Therefore, the working current of the main motor and the bearing load of the cutter are correspondingly small, and the tunneling speed can be increased on the premise that the feedback parameter information of the roadheader allows

however, the rotating speed of the cutterhead will greatly disturb the weak surrounding rock at high speed, which may cause the surrounding rock to collapse due to instability. At the same time, the mucking is fast at high speed, which will increase the working load of the belt conveyor. Therefore, in the geological condition of weak surrounding rock, the cutter head speed is mainly low-speed. However, in order to make the roadheader give full play to its efficiency, high speed should be selected as far as possible when conditions permit, which should be used to judge the driving force of the cutterhead and the mucking condition. Experience shows that under the working condition of low speed and 60% tunneling speed, if the propulsive force rises to 10MN and the slag discharge is stable and uniform, high speed can be used; At high speed, when the propulsive force drops below 5MN or the slag discharge is unstable under the working condition of 60% tunneling speed, the low speed should be used

when the cutter head is stuck or at low speed, the spacing of zigzag support rollers: 30 ~ 600mm; When the amount of mucking is still large due to collapse, the hydraulic auxiliary drive can be selected to adjust its speed within the range of 0~1r/min

(4) selection of cutter head propulsion

the propulsion force is 17.7mn at full load. In order to protect the cutter, it should be controlled below 15mn. At low speed, when the propulsion force exceeds 10MN, high speed can be selected. When the propulsion force of the cutter head is certain, the propulsion pressure of the propulsion cylinder is a certain value, so it is not considered

(5) selection of cutter head torque and main motor current

cutter head torque is generated by the main motor and should be controlled below 80%. The maximum allowable current of the main motor is 410a, so the working current of the main motor should be controlled below 320A

(6) control of shoe pressure

shoe provides support for the cutter head. The higher the shoe pressure, the greater the friction, and the more stable the support. However, in the state of weak surrounding rock, if the shoring pressure is too high, the surrounding rock will collapse and cause poor support, so the shoring pressure is limited by the surrounding rock, but at the same time, the reaction force (i.e. the thrust of the cutterhead) generated by the weak surrounding rock on the cutterhead will not be too large, that is to say, the required shoring pressure does not need to be too high, which is generally MPa. If the conditions of the support shoes are not good, the 8 pairs of support shoes cannot be fully supported. At this time, the pressure of the support shoes cannot be blindly increased. In this case, the thrust of the cutterhead is large, and the thrust can be reduced by reducing the tunneling speed, so that the support shoe will not slip due to exceeding the support reaction provided by the support shoe

(3) control of tunneling direction

because the support reaction provided by soft surrounding rock for cutter head shield and support shoes is small, the posture of the tunneling machine is easy to change during the tunneling process, and its direction control is easy to deviate from that during the construction of hard rock tunnel, which can be controlled by the following methods:

preferred, the support shoes should be avoided from slipping, because the support reaction provided by soft surrounding rock for support shoes itself is not large, Slip of supporting shoes will worsen the opening trend. Large directional changes are often caused by slip of supporting shoes, so slip of supporting shoes should be absolutely avoided. When the conditions of the support shoe position allow, the pressure of the support shoe can be increased to improve the friction; When the conditions of shoring position are not allowed, it can be controlled by reducing the speed of digging drought (mentioned above); In addition, when the surrounding rock at the support shoe position collapses and individual support shoes cannot be supported, spray and pour concrete, and support the support shoes after the concrete solidifies

secondly, since the dead weight of the cutterhead area composed of cutterhead, main bearing, shield, cutter and hydraulic components can reach hundreds of tons, the actual heading direction will tend to be lower than the predicted heading direction, and the direction deviation caused by different surrounding rock strength is also different. For this phenomenon, we adopt the method called "pre correction control", that is to increase the axial elevation according to the deviation shown in the previous several tunneling cycles, so that the main engine has an upward tunneling trend in advance, so as to reduce the direction deviation caused by its self weight

moreover, similar to the above situation, the deviation of the excavation direction X axis (i.e. the left and right directions) is often caused by the weak strength of local surrounding rocks. We can still adopt the "pre correction control method" described in vigorously developing the plastic granulator technology using renewable energy and industrial waste heat, and adjust the corresponding guide angle to control it. It is different here

it should be pointed out that in order to avoid the damage of surrounding rock to the tool, the direction adjustment of the roadheader should not be too large each time, and the axial elevation or guide angle should not be adjusted more than 3 ° each time; Although the overall strength of the soft surrounding rock is weak, because the rock quality of the tunnel face is often heterogeneous, and there are still hard rocks locally, unless special circumstances, the amount of each adjustment should not exceed 3 °. When major adjustments are required, they can be adjusted in several cycles and times

practice has proved that the heading direction can be well controlled as long as it can be controlled and adjusted according to the above principles and methods

(the market value of global advanced polymer composites is expected to grow to US $12.12 billion end)

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