Pile tip design of the hottest new structure

2022-08-14
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New structure pile tip design

l overview of pile foundation with the development of modern cities, super high-rise buildings. There are more and more long-span plants, and the foundation used to support these giants is also getting larger and deeper. In foundation construction, in order to reduce labor intensity, improve production efficiency, shorten construction period, reduce project cost and improve construction conditions, most of these large foundations are designed as pile foundations with high degree of mechanized construction, great bearing capacity and good seismic resistance. Pile foundation is divided into precast pile and cast-in-place pile according to different construction methods. In order to facilitate construction and reduce noise pollution during construction, cast-in-place piles are often used for pile foundations with large single pile diameter (more than 500mm) and located in downtown areas. The cast-in-place pile is also divided into soil sampling cast-in-place pile and soil compaction cast-in-place pile. The former is mostly used in the northern and unitary areas with low groundwater level in China, and the latter is mostly used in the southern and eastern coastal areas with high groundwater level in China. 2. Proposal of the subject at present, soil compaction is to drill a steel pipe with the same diameter as the pile, and the lower end is equipped with a valve pile tip or a separate concrete pile shoe into the soil to form a hole. The mechanical equipment usually used for squeezing soil into holes is the pile equipped with a vibrating hammer. The vibrating hammer can sink or pull the steel pipe, and the vibration of the vibrating hammer can greatly reduce the front-end resistance and side friction resistance of the steel pipe. Use a 300KN testing machine with a maximum test pressure equipped with a valve pile tip or a split concrete pile shoe. The accuracy of the testing machine is better than ± 1% of the spacing between the pressure plates. The English title main technical parameters function and characteristics of the testing machine's device repair and maintenance instrument operation market price. The hole formed by the steel pipe cannot form an enlarged head at the bottom, as shown in Figure 1a. For large diameter piles with large bearing capacity of a single pile (generally 800mm ~ 1000mm), when the pile hole is deep into the hard soil or rock layer, it is often necessary to dig an enlarged head 1.5 ~ 2 times the pile diameter and 1.5m ~ 2m deep, as shown in Figure 1b. The construction technology of this kind of pile (vibration sinking artificial hole expanding cast-in-place pile) is: ① vibration sinking to hard soil or rock layer; ② Manually chisel and expand the head; ③ Place reinforcement cage; ④ Vibrate and pull out the steel pipe while pouring concrete. Obviously, if the valve pile tip or separated concrete pile shoe is used at the lower end of the steel pipe, it will increase the difficulty of manual excavation, and even it is impossible to carry out manual excavation. Because the collapse proof, water-proof and sediment proof steel pipes cannot be pulled out before pouring concrete, a new type of pile tip that can be taken out of the steel pipe is needed. 3. Design of pile tip structure 3.1 the outer diameter of pile pipe of pile tip structure is d = 800mm (i.e. pile diameter), and the wall thickness is 15mm. The pile tip structure is a combination of welding, pin connection and bolt connection, as shown in Figure 2. The taper of the pile tip is 60 ~ 90 degrees. Its components are: Part 1 lifting ring. The lifting lug made of 15mm thick steel plate is welded on the steel pipe with an outer diameter of 138mm and a wall thickness of 10mm. Three connecting sliders are uniformly welded on the lower circumference of the steel pipe, and the sliders can slide up and down in the guide groove of Part 2. The guide tube of Part 2 has an outer diameter of 160mm and a wall thickness of 10mm. Three guide grooves are evenly distributed on its lower circumference. The guide groove is equipped with a limit block 4. The guide tube is welded to the upper cover plate of the pile tip 8. The connecting rod of Part 3 (3 in total) connects the lifting ring 1 with the sliding block on the sliding plate 6 through the pin. Only after passing the inspection can the product be delivered or sold. The limit block of Part 4 limits the outward movement distance of slide plate 6. The pressing plates of Part 5 (3 pieces in total) are processed from steel plates with a thickness of 60mm, and are uniformly connected to the upper cover plate of pile tip 8 through the circumference of M20 bolts (nuts are welded on the inner side of the upper cover plate). The outer diameter of the three pressing plates after assembly is 760mm, and a distance of 50mm is left between the two pressing plates as the guide groove for connecting the sliding block on the sliding plate 6. Part 6 sliding plate (3 pieces in total) is processed from 30mm thick steel plate. A connecting slider is welded on its radial center line. A pile pipe groove 7 with an outer diameter of 805mm, an inner diameter of 765mm and a depth of 10 is processed near the outer circle. The outer diameter of the three sliding plates is not more than 760mm when retracted. The pile tip of Part 8 is welded by an upper cover plate with an outer diameter of 760mm and a thickness of 30mm, a side plate with a thickness of 20mm and a rib plate. Part 9 rib plate, 15mm ~ 20 thick, and it is required to make mm steel plate with non-magnetic materials into cross welding. Bolt of Part 10, M20, at least 5 on each pressing plate. 3.2 working principle use the attached hook of the pile machine to string through the vibrating hammer and the central hole of the pile pipe to hang the lifting ring of the pile tip, so that the pile tip is located at the pile position directly below the pile pipe, so that the sliding plate of the pile tip extends, put the pile pipe in the groove of the sliding plate, tighten the lifting rope of the pile tip, so that the sliding plate groove clamps the pile pipe tightly, after the pile pipe is in place and touches the ground, the pile can be sunk, and the lifting rope of the pile tip should always be relaxed during the pile sinking process. After the pile is sunk in place, lift the pile pipe by about 50mm, tighten the lifting rope of the pile tip, and the sliding plate of the pile tip retracts under the tension of the lifting rope, so that the whole pile tip can be lifted from the pile pipe. 4. Construction technology of sinking and reaming cast-in-place pile (1) Vibrating Sinking to hard soil or rock layer after the pile tip is installed in place; (2) Lift the pile pipe for 50 mm, and the result shows that the pile tip is hoisted into the pile pipe, and then vibrate the pile pipe into the hard soil layer or rock layer; (3) Remove the pile pipe from the vibratory hammer, lift the pile tip out, and then sink another pile pipe; (4) Drain the muddy water in the sunk pile pipe and excavate the enlarged head manually; (5) After the enlarged head is dug, the pile driver returns to its position, the pile tip is removed, and the reinforcement cage is replaced and hoisted. After the reinforcement cage is in place, start pouring concrete, and pull out the pile pipe while pouring

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