Pre Bored Steel H Piling System

Pre Bored brand H Piling SystemAlthough Hong Kong is featured of its Skyscrapers all everyplace the world, and it seems that H-Piling governance may non lay down tolerable bearing strength to their superstructure, at that place argon still many servicing mannequinings and small-scale infrastructure growth, the incumbrance of which is capable to be borne by H-Piling organization, in the city. In the following words, a brief introduction over Pre-Bored make H-Piling constitution pull up s divvy ups be presented associated with related fibers applying much(prenominal) kind of cumulation system in Hong Kong in order to draw a more detailed picture over the application of Pre-Bored trade name H-Piling system in Hong Kong.The principle of Pre-Bored Steel H-Piling system is similar to the Bored Piling system. Both of them be replacement heap and require boring the initial hole on the localise for the interpolation of the temporary or permanent vane fount, dependi ng on its design. aft(prenominal) the closure of the boring care for, the res publica and swing inner(a) the steel example will then be extracted and the workers will place the reinforcement material deep down(a) the steel type. That is the major variation between Bored Piling and Pre-Bored Steel H-Piling System. For Bored Piling, the reinforcement nix will be bent in order to form the circular cage ( forecast 1). However, H Steel nap will be the reinforcement material in Pre-bored H-Piling system. Grouting is then started aft(prenominal) placing reinforcement material to form the clutch.Since the diameter of Bored Piling sens be larger than Pre-Bored H-Piling, the cause one bottomland typically take up more core than the last mentioned one. Therefore, small-scale body structure fox is virtually likely to use Pre-Bored Steel H-Piling system in Hong Kong. The cases introduced ulterior are small in scale, but they do play an classic role in our city.Dyr1 sem1BR E 291 Con techProject Photos (Construction site)Week 4 23102009CIMG0341.JPG introduce 1 funding Bar for Bored Piling inscribe 2 H-Pile for Reinforcement in Pre- Bored H-Piling systemThe first case being examined is the plait of cigaret Mary Interchange near coffin nail Mary infirmary and Pok Fu Lam alley. It is a road improvement pop the question initiated by the local establishment at the deuce junctions, which are in Sassoon Road and Bisney Road with Pok Fu Lam Road, on Hong Kong Island. The aim of this project is to relieve the congestion difficulty existing in these roads by constructing a new interchange, comprising of several(prenominal)(prenominal) link up.CUsersAlan KwokDesktopperspec.jpg work out 3 Model of proposed developmentFigure 4 female monarch Mary Interchange Still in the progress of social organisationAs we can see in the model of proposed development (Figure 3), the interchange, which set(p) at the bottom of the figure, is locating on a slope. Since t he the state in slope exert a considerable amount of bending and plastic stress, according to Tomlinson (1994), H-pile is able to withstand such kind of extreme placement collectible to its unique H design. Therefore, the authority concerned decided to build the interchange with Pre-Bored Drill-in Steel H-Piles. Moreover, the short erection time and economical construction speak to are also the flat coat to make use of such kind of piling system in this project. According to Kumaraswamy, Mohan (2002), the solid process of developing a Pre-Bored drill-in H pile, i.e. pre-drilling, drilling and grouting, can be end in 3 working days. We can also see that the site is not so spacious enough to place whatsoever big machinery during the pile development. The development of Pre-Bored Drill-in Steel H-Piles can overcome this problem because the diameter of this pile is that 600mm in this case The size of drilling techniques can be controlled and fitted into the congested site.CUs ersAlan KwokDesktop1000.jpgFigure 5 The congested site on a steep slopein this construction of Queen Mary InterchangeBefore the development of pile in this project, several raw materials and tools are involve to present. Here is the table showing what are needed,CUsersAlan KwokDesktop8.jpgCircular steel eccentric of internal diameter 600mm and oppressiveness 25mmCUsersAlan KwokDesktop10.jpgSteel H-pile, which will be inserted in the steel casingCUsersAlan KwokDesktop843.jpgHydraulic hammer mounted on crawler stretch forthTable 1 Major Material list for constructing pile of Queen Mary InterchangeIn the very first stage of developing Pre-Bored Drill-in Pile in this project, engineers will have a pre-drilling finished the soil layers and rock within the site in order to identify the cloak-and-dagger condition, such as the rock head levels and the strength of the soil. It is an important role since it will determine the type, length, etc of the pile. Any wrong measurement, especi ally overestimate the soil/rock supporting capacity, will make the whole project ache ground because the whole structure will be ruined, the typical case is the Block E and F of Yu Chui Court, demolished after discovering the corruption scandal, which actual by piles shorter than the standard and cause possible risk of exposureous to its users .After the completion of soil investigation and analysis, the engineers would then design and choose the most suitable piling system for variant project. In the construction of Queen Mary Interchange, the engineers found out that the Pre-bored piling system is suitable for construction of high-way bridges at the steep slope on the site. The site-workers firstly touch the circular steel casing inside the ground through the abet of Hydraulic Hammer which is mounted on a crawler crane. The reason to plug the steel casing into the ground was to prevent the soil from collapsing inside the hole, which would be placed H-pile inside it, during t he process of drilling.CUsersAlan KwokDesktop1.jpgCUsersAlan KwokDesktop9.jpgFigure 6 Inserting circular steel casing into ground by hydraulic hammer mounted on crawler craneFigure 7 Connecting two steel casings by weld when the length is not enoughThe process in Figure 7 happened when the steel casings being installed were not long enough to reach the target depth into the soil. By welding the end of two steel casings, the total length of it can be all-inclusive. For the inadequate length of H-Pile, their length can also be extended through welding.When the steel casing reached the bed rock level and organize a socket, the next stage is to contract those soil and rock inside the steel subway, as shown in Figure 8. The ground was drilled with a hammer mounted on a drilling rig so as to remove the obstruction underground. This process could enable the hard rock and pressed soil to become extractable out of the steel casing. In this project, the obstructions were then extracted ou t by flushing the case with water and rigorous air. The prostrate air acted at the initial force and the water acted as a transferring medium to carry out the obstruction out of the earth. The above two procedures will take turns to start until all of the obstruction inside the electron tube were wholly carried out.CUsersAlan KwokDesktop2.jpgCUsersAlan KwokDesktop3.jpgFigure 8 Removing obstruction by drilling with down-the-hole hammer mounted on drilling rigFigure 9 Withdrawing soil from inside the casing by flushing with water and compressed airThe H-Piles would then be installed inside the empty steel casing after the clearance of obstruction inside. Meanwhile, a 20mm diameter grout tube was also placed to full length of the pile in order to prepare its grouting process later on.CUsersAlan KwokDesktop4.jpgFigure 10 install steel H-pile inside the empty steel casingThe grouting process is to have a re-bonding between the soil and the H-piles with the suitable configuration of cover by tremmie method from the bottom to the top of the casing. Tremmie method is a concrete- decanting method in some dry spaces underground deeply. Since a tube is used to pour the concrete from the bottom, the force of falling concrete can be controlled through shortening the distance of freely movement of the concrete. It can prevent the concrete from improperly mixed when it is placed at the bottom of the casing which allow for in voids and air packet which can cause possible danger to the whole structure.The temporary steel casings were extracted gradually when the fresh concrete was burbly inside since the bonding force of the concrete is not strong at this moment. However, engineers maintained the bottom of the casing at a level of at least 2 meters below the grout surface to ensure that at that place was enough time range for the concrete to form the circular shape. The grouting military operation was stopped when the uncontaminated grout flowed out of the hole to ens ure the excellence of concrete poured inside the casing.CUsersAlan KwokDesktop5.jpgCUsersAlan KwokDesktop7.jpgFigure 11 Grouting the steel casing with suitable grade of concrete by tremmie methodFigure 12 Extracting the steel casing while grouting is going onCUsersAlan KwokDesktop6.jpgCUsersAlan KwokDesktop11.jpgFigure 13 Grouting the steel casing with suitable grade of concrete by tremmie methodFigure 14 Extracting the steel casing while grouting is going onThe finishing of grouting process means that the whole development of Pre-Bored Drill-in H-Pile system is come into the end soon. After the dewatering process of the concrete attached to the H-Pile itself, the drilled-in H-Pile was finished. Figure 13 shows the product of the above stages. It is a free radical of drilled-in H-Piles that were formed a combined pile cap for the highway bridges in Queen Mary Interchange. To verify its bear capacity, loading interrogation was taken place in order to test its vertical deflection. one time the test was passed, the superstructure developments were then taken place.Pre-Bored Steel H-Piling system is not only use in local road constructions, but it is also applied in some small-scale construction of structures in Hong Kong. There is a typical example, which is the construction of Sheung grim Stormwater Pumping Station (SWSPS) on Hong Kong Island. It is a single-storey building with a underground water tank with 11 meters deep at the Chung Kong Road, which is the waterfront of Sheung Wan. This project was to alleviate the flooding problem in Sheung Wan.CUsersAlan KwokDesktop391 projectProduct of construction.pngFigure 15 Sheung Wan Stormwater Pumping StationFigure 16 Location design of Sheung Wan Stormwater Pumping StationAccording to the paper presented by Leung,Li and Leung (2009), the site of the Sheung Wan Stormwater Pumping station was reclaimed in 1982. The material used for reclaimed it are as followed,Fill (medium grained granite)Marine DepositAlluviu mCompletely Decomposed Granite (CDG) before the engineers decided to build up this service station with 60 poem of large diameter bored piles, and the diameter of which are ranged from 1.2 meters to 1.5 meters.Figure 17 The Original Bored Pile Layout Plan of SWSPSFigure 18 The geologic Section Across the site (Land Seawall)But later on, the contractor of this project advised the governing to build up the superstructure and sub-structure over a compounding of rock socketted H-piles, mini-piles and raft pes. The government finally accepted the advice from the contractor and jump the construction process. Referring back to the Figure 17, the PC5 Zone, all of the piling would be changed into the Pre-Bored H-piling system. For the opposite zoning, mini-piles were used.The major reason to change the piling system, as the paper disclosed, was because of the cost effectiveness. First of all, since the diameter of the steel casing used in Pre-Bored Steel H-Piling system is far smaller than the bored piling system. The grouting process of the former one will consuming less amount of concrete than the latter one, which can reduce the cost of development.Table 2 The difference in pile foundation between the initial and final plan anyways the cost consideration factor, the time used for developing these two different kinds of piling systems is different. As what Kumaraswamy, Mohan (2002) said, the whole process of developing a Pre-bored H-piling system only cost around 3 days. However, the development of a foundation pile normally takes up more than 3 days. Since the amount of pile developed in this project is large, i.e. nearly 50 piles are changed from bored pile to pre-bored H piling system. The time cost protected through the final plan is considerable.In the aspect of technical operation, the required pile capacity of the pumping station is 6900 kN. For bored piling, For bored piling (The government of HKSAR,2006), typical sizes of these piles range from 1 m to 3 m, with lengths up to nearly 80 m and working loads up to about 45 000 kN. When high grade and heavy steel H-pile section is used, the load-carrying capacity can exceed 5 500 kN. We can see that the loading capacity of bored piling is far more than the loading destiny of the pumping station. However, we can also discover that a maximum of 1400kN was not be able to supported by Rock Socketted Steel H-Pile. The solution, as shown in Figure 18, is to place in 4 numbers of T50 steel bars inside each of the casing for reinforcement so as to remove the discrepancy.Therefore, the final plan can enable a more competent use in the resource than the initial one. That is why it is reasonable for the government to change its decision.Figure 19 Typical detail of Rock Socketted H-piles of pick DesignFor the developing processes of the Pre-bored socketted H-piling system, most of them are the same as the Pre-bored Drilled-in piling system. The major difference between them is that the steel casing used in Pre-bored socketted H-piling system is permanently fixed inside the soil, while the steel casing used in Pre-bored Drilled-in piling system was temporary in used. They are removed during grouting. In this project, the rock socket H-piles were installed through the help of concentric burden drilling system with air-flushing. It uses a rotary-percussive action for drilling and uses air flushing for removal of debris before casting in the H-pile inside the tube and grouting.In conclusion, the loading bearing capacity of Pre-Bored Steel H-Piling system is relatively reduce than the other common piling system used in Hong Kong. However, due to its mobility during installation and its strength, it is still also commonly applied in some small-scale development in local projects.-The End-