What issues should be paid attention to when constructing the hose core pulling method?

The hoses used in the hose core pulling method include 5 to 7 layers of cloth-covered hoses and steel mesh rubber hoses specially used for prestressed concrete. The former must be inflated or filled with water before use; the latter is hard and has a certain elasticity, and can be used like steel pipes when the holes are reserved. The hose is laid in advance at the hole position in the formwork. The hose is fixed with a steel well bracket. The distance between each straight section of the hose is not more than 1.0m, and the distance between each curve section is not more than 0.5m, and it is tied firmly to the steel frame. The following introduces the commonly used methods of leaving holes in cloth-covered hoses. When using a cloth-covered hose to reserve a hole, fill the cloth-covered hose with compressed air or pressurized water before concrete pouring. The working pressure is 500-800KPa. At this time, the diameter of the hose can be increased by about 3mm. After the concrete has initially set, release compressed air or pressure water to reduce the diameter of the pipe and separate it from the concrete. Pull out the cloth-covered hose to form a hole. In order to ensure the quality of the remaining tunnels, the following issues should be paid attention to during construction.

(1) After the hose is laid, care should be taken not to let hard objects such as steel bars pierce the hose. The hose should have good sealing and prevent it from leaking water or air. Before filling the cloth-clamped hose with compressed air or pressurized water, both ends of the hose should be sealed. The sealing method is to cut off 1 to 3 feet of rubber and canvas from one end of the hose, then insert a steel pipe with a thick threaded buckle on the outer surface (one end of the steel pipe is sealed and welded with an iron plate) into the end hole of the hose, and then use No. 20 The iron wire and the outer surface of the hose are tightly wrapped and firmly, and the iron wire head is soldered firmly with tin. The other end of the hose is connected to the valve, and its sealing method is basically the same as the sealing end.

(2) Hose joint processing, the picture shows the hose joint method. The 1mm thick steel pipe in the picture is made of seamless steel pipe, and its inner diameter is equal to or slightly smaller than the outer diameter of the hose so that it can seal after the hardwood plug is driven into it. The outer diameter of the iron casing is equal to or slightly larger than that of the hose (about 0.5mm) to prevent the hose from moving outward due to vibration when vibrating concrete.

(3) Tubing time and sequence. The pumping time is slightly later than that of steel pipes. Generally, when the product of the temperature and the number of hours after pouring reaches about 200°C/h, it is the pipe adaptation time. When the hole is reserved by the hose core pulling method, there is no need to rotate the hose after the concrete is poured. The order of drawing the hose is generally first up and then down, first curved and then straight. When using steel mesh hose to reserve holes, the method of reserving holes is the same as that for steel pipes. Because the steel mesh hose is hard and has a certain degree of elasticity, the diameter of the pipe shrinks under the action of tension when the pipe is pulled out, and the steel mesh hose is separated from the concrete, and the steel mesh hose can be pulled out. The grouting holes and vent holes of the rubber hose core-pulling method are the same as those of the steel pipe core-pulling method.