In the process of excavation, first of all, the open caisson shall be measured to investigate the degree of deflection. At the same time, the connecting bars on the top of the well shall be uniformly bent outward to 90 degrees parallel to the top of the well, and the tie bar heads protruding from the inside and outside of the shaft wall shall be cut to reduce the sinking resistance of the open caisson and the damage caused by the steel bar heads to the digging teeth of the bucket. The surface around the open caisson shall be leveled so as to stop the machinery.
2. Docking machinery
According to the characteristics of the excavator, select the appropriate position to stop the machine. The selected position must ensure that the excavator's stick and boom can fully extend vertically in the well hole, and the back wall and the well wall can maintain a certain height to avoid collision.
3. Excavation subsidence
A duty officer shall be arranged at the top of the well to be responsible for the on-site command of the excavator when excavating the bottom of the well. The excavator driver shall operate according to the visual inspection results and the hand gestures of the duty officer. First, tilt the boom forward 15 degrees, so that the bucket digging teeth can vertically sink to the bottom of the well hole, and then according to the resistance of digging down, the bucket digging teeth can vertically sink to the bottom of the well hole, and then according to the resistance of digging down, make the bucket hook back to full,! After lifting the forearm and the stick to make the bucket leave the well hole, rotate the chassis of the main engine to move the bucket to 5 meters away from the open well and fall it. Repeat for 6 times, and then turn to the excavation of another well hole, so that the bottom of the pot at the bottom of the caisson is formed evenly. In the process of excavation, the soil around the shaft wall will collapse to a certain extent, and the sunk shaft will gradually sink.
4. Lower the height of the long arm excavator
When the top of the well is 50cm away from the water level line, the excavation shall be stopped. During this period, the excavation times of each well hole shall be reduced, and the excavation staggered frequency of left and right well holes shall be strengthened to make the open caisson sink evenly. When the underground water level is low, when the bucket of the excavator can not reach the bottom of the well hole, the soil mass on both sides of the open caisson shall be enlarged so as to reduce the main height of the long arm excavator and make full use of the bucket to open caisson Borrow at the bottom.
5. Measurement observation
After excavation! In the first few hours, the horizontal surface in the well bore will show uneven shaking, which is that under the self weight of the open caisson, the soil at the foot of the blade is still gradually squeezed out to the bottom of the pot, and the open caisson is still in the process of sinking. When the horizontal surface is calm, the sinking of the open caisson is basically stable and can be measured and checked. By measuring the elevation of the center point of the caisson, the end point of the horizontal axis and the four sides of the top of the caisson, check the deviation value, inclination and torsion of the caisson center.
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