There are many reasons that can cause damage to the shield tail brush, but the specific analysis can be summarized as follows:

(1) Mud, mortar, etc. entering the grease bin and forming hard blocks can cause damage to the shield tail brush, and even strain the tail brush;

(2) The shield tail brush sealing device loses its elasticity due to plastic deformation caused by excessive compression of the eccentric pipe segment, resulting in a decrease in sealing performance and causing slurry leakage under pressure;

(3) The retreat of the shield machine causes opposite movement of bristles between the shield tail brush and the pipe segment, causing the bristles to roll back and the shield tail brush to deform, resulting in a decrease in sealing performance and leakage;

(4) Insufficient oil injection, insufficient oil filling of the oil tank, insufficient oil pressure to resist soil forces causing harmful substances such as mud to enter the oil tank and accelerate the wear of the shield tail brush;

(5) The hard block enters the grease compartment through the back of the pipe, causing strain on the tail brush of the shield.

The prevention and control measures include:

(1) Strictly control the correction amount of shield tunneling, try to make the gap between the shield tail around the pipe as uniform as possible, and reduce the degree of compression of the shield tail brush by the pipe;

(2) Prevent shield tunneling from retreating;

(3) Daily maintenance of the shield tail grease injection system, timely replenishment of grease in the grease compartment.

(4) Specific measures for protecting the shield tail brush during construction 4.1 Protection of the shield tail brush at start-up Before starting the shield machine, WR90 grease should be applied to the steel wire of the shield tail brush, and the application standard is that each steel wire of the tail brush should be covered with grease. If not applied properly, it will affect the sealing effect of the tail brush, and in severe cases, it may leak grout, causing damage to the shield tail brush. After assembling the first ring of pipe segments, a long period of grease injection should be carried out to ensure that the grease compartment is completely filled with grease before advancing the shield machine. Especially when the shield body completely enters the soil, it must be ensured that the grease compartment is filled with grease and has a certain pressure to prevent harmful substances from entering the grease compartment and causing damage to the tail brush.

Protection for shield tail brushes in special circumstances

(1) When opening and closing the compartment, pay attention to injecting grease when the mud and water pressure continues to increase.

(2) When shutting down for a long time, it is necessary to inject grease at regular intervals.

(3) When performing secondary grouting or polyurethane near the tail of the shield during shutdown, it is necessary to choose whether to add grease based on the injection pressure and the pressure inside the grease compartment to prevent it from entering the grease compartment and protect the tail brush.

(4) When there is a leakage of grout, it is necessary to apply grease locally at the leakage site. If the grout leakage occurs during synchronous grouting, it is best to apply grease locally. And during the subsequent promotion, increase the amount of oil injected until it stabilizes.

(5) When serious leakage or slurry leakage occurs, the method of injecting grease into the entire tank at the tail of the shield is adopted to ensure sufficient grease and pressure in the grease tank. It is recommended to gradually inject from the relatively small leakage area to the larger area. If necessary, block the cotton quilt between the pipe segment and the shield tail before injecting grease. After blocking, stop the machine within 50mm for grease injection to consolidate the effect. The relative position is used to adjust the correction method, making every effort to make the gap between the shield tails uniform and consistent. At the same time, the reasonable selection of K blocks also plays a significant role in protecting the gap between the shield tail and the shield tail brush