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<\/p>\nHello, everyone.<\/p>\n
This is Enta.<\/p>\n
I wrote an article a while back called \u201cFor Those of You Who Can\u2019t Sleep Because Your Anchor Is Missing\u201d (what a terrible title, lol)<\/p>\n
Even now, I still occasionally get messages like, \u201cIt came out\u2026 what should I do\u2026?\u201d lol<\/p>\n
I understand exactly how you feel.<\/p>\n
I\u2019ve had anchors come loose many times myself, and it\u2019s even happened at our construction site, lol.<\/p>\n
But it's okay.<\/p>\n
If it comes out, just start over.<\/p>\n
I\u2019m happy to do rework on our own projects, and I\u2019ve also done rework for other companies.<\/p>\n
<\/p>\n
But that's beside the point.<\/p>\n
This time, we\u2019ll tackle the first hurdle in that \u201cdo-over\u201d<\/p>\n
How to Pull Out a Loose Anchor<\/strong>I\u2019ll cover everything in one go\u2014from step-by-step instructions for each tool and safety precautions to determining when to redo the work.<\/p>\n The design and construction standards for ground anchors are basically written with the premise that \u201cthey must not pull out,\u201d so they don\u2019t include any instructions on what to do if they do pull out lol.<\/p>\n In other words, this area is entirely based on oral traditions passed down on-site.<\/p>\n That\u2019s exactly why I think it\u2019s worth writing down.<\/p>\n Before thinking about how to pull it out, there\u2019s one thing you need to check.<\/p>\n Where is the gap?<\/strong><\/p>\n 1. Is it on a slope at a high elevation?<\/p>\n 2. Is this even a place where a backhoe (BH) can operate on unpaved ground?<\/p>\n 3. Can a crane be used?<\/p>\n This determines which tools to use and the procedure to follow.<\/p>\n <\/p>\n For slopes: A jack is the only option.<\/strong><\/p>\n If you need to remove it from a slope, you have no choice but to use a jack to lift it out.<\/p>\n Although the free length of a permanent anchor is covered, if the grout has come loose, only the PC steel strands inside will be exposed.<\/p>\n Repeat the process: \u201cUse the jack to pull out the steel wire \u2192 shift the jack\u2019s head and reinsert the wedge \u2192 use the jack to pull it out again.\u201d It\u2019s a tedious process, but it\u2019s reliable.<\/p>\n However, this is based on the fundamental premise that the PC strands are no longer adhering to the cement slurry.<\/p>\n If this attachment is still intact, do not pull it until it reaches its breaking load! It is extremely dangerous!<\/p>\n If you absolutely can't get it out, you'll have to cut it off.<\/p>\n If you can't pull them all out at once, try pulling them out one by one if that works.<\/p>\n <\/p>\n If BH is involved, it's relatively easy.<\/strong> Grab each PC wire one by one with a wire clip, attach it to the BH, and pull hard\u2014it\u2019ll come out easily.<\/p>\n If a crane is available, you can use the same method as for BH.<\/strong><\/p>\n As a general guideline for the required force, whether using a jack, a BH, or a crane, it is usuallyIt can be pulled out with a force of several hundred kilograms.<\/strong>\u3002<\/p>\n And once it starts moving, it slides right out.<\/p>\n Even when using a jack to remove it little by little, I\u2019ve often found that it slides right out with a load of about 1 metric ton.<\/p>\n By the way, tools that can be used to pull out temporary anchors include:Fujiwara Industries Co., Ltd.<\/a>A product called \u201cUnbond Lock\u201d is available from [Name], which securely locks onto PC steel strands and allows them to be pulled out.<\/p>\n It's convenient because it can be used with either a BH or a crane.<\/p>\n Please check the latest information regarding current sales status and model numbers.<\/p>\n This is where the real action begins.<\/p>\n If it came out easily, there wouldn't be any trouble, but\u2014Most of the time, they get stuck halfway through and can't get out.<\/strong>w (I'll skip the temporary part)<\/p>\n A common issue with temporary anchors is when, for some reason, the sheath surrounding the prestressed steel strands tears, allowing cement slurry to seep in.<\/p>\n Once it gets to this point, it's really hard to get out of it.<\/p>\n It depends on how long it's been stuck there, but based on my experience,It will come out if you apply about 7 metric tons of force.<\/strong>\u3002<\/p>\n However, this 7-metric-ton area is dangerous for cranes and backhoes.<\/p>\n It's not that you can't remove it with a crane, but I don't recommend it because there's a risk of falling due to the recoil when it comes loose.<\/p>\n This is exactly when you need a jack.<\/p>\n If the formwork has already been removed and there is neither a steel base nor any counterforce, then,Install a pressure plate to absorb the reaction force while pulling it out.<\/strong>...and can be done safely.<\/p>\n The job site we actually worked on had an installation angle of about 40 degrees, which made it difficult, but if we pulled straight, it came out easily, and once it started moving, it was fine to remove it with a crane.<\/p>\n <\/p>\n And,There are some anchors that should be deemed \"unremovable\" from the start.<\/strong>\u3002<\/p>\n With tie-back anchors such as SEEE, since a nut is attached to the \u201cmansion\u201d section at the tip, there is a limit to the length of the mansion.<\/p>\n So, it's impossible to remove them all at once. Just cut them off\u2014that's fine!<\/p>\n In addition, since the surrounding poly-based components and other materials remain in place, drilling holes later on becomes quite difficult.<\/p>\n Depending on the type of anchor, it\u2019s probably best to state outright that \u201cit won\u2019t come out,\u201d so don\u2019t try to pull it out by force, and<\/p>\n It's safest to switch to hitting from a different angle right from the start.<\/strong>That's it.<\/p>\n If I absolutely had no choice but to drill in the same spot, I\u2019ve also had experience drilling a hole while cutting the PC steel strand with a metal-cutting drill bit at different angles into the same hole.<\/p>\n The task in the pulling-out process that is most likely to result in an accident is,The Moment It Slips Out<\/strong>That's it. The steel wire snaps with a plunk.<\/p>\n The following applies only when using a crane or a backhoe to remove the object. It does not apply to jacks.<\/p>\n There are three measures we take on-site to prevent splashing.<\/p>\n 1,Hold the steel wire with a rag<\/strong>. If you hold the steel wire with a rag just before it comes out, it won\u2019t bounce around violently. \u201cIsn\u2019t holding it dangerous in the first place?\u201d<\/p>\n People sometimes say that, but it\u2019s really no big deal. (You\u2019ll see once you try it; if people say it\u2019s dangerous, just add one more piece of equipment at the end.)<\/p>\n 2,Operating Direction<\/strong>. At the moment it comes loose, if the crane or BH operator swings the steel wire in the \"return direction,\" it is less likely to bounce.<\/p>\n And the positioning of the crane and BH at the moment of release is also important.<\/p>\n Do not place people or machinery in positions where they could be struck by a bouncing steel wire. This means you should not pull the wire straight from the front.<\/p>\n 3,Anchoring of Pressure-Bearing Structures<\/strong>. In the case of secondary products such as pressure plates, there is a risk of them falling if the anchors come loose. Be sure to secure them before beginning work.<\/p>\n In the case of a jack, it will fall the moment it comes loose, so be sure to secure it.<\/p>\n Just a little tip: toward the end, you can actually pull it by hand (though you'll get covered in grease, lol).<\/p>\n Also, the machine that removes the unbonded material while spinning around with a motor isn't available for rent or anything like that.<\/p>\n I can say this for sure because I've looked for it before lol (Apparently, it used to exist.)<\/p>\n Once the extraction is complete (or if it is determined that the object cannot be removed), it is time to design and plan the reinstallation.<\/p>\n There are four key points to consider.<\/p>\n \u2460 Adjust the angle.<\/strong> Since it\u2019s difficult to pour concrete in exactly the same spot, we vary the position slightly\u2014up, down, left, and right\u2014by about 1 or 2 degrees within the construction tolerance limits.<\/p>\n In my experience, it\u2019s usually a matter of raising or lowering it about three times, or moving it back and forth.<\/p>\n In the troubleshooting article I wrote in 2017, I also mentioned, \u201cIf possible, adjust it downward by 1 to 2 degrees.\u201d<\/p>\n However, there is a limit. If you set the angle too high, the angle during head processing will exceed 5 degrees, so that won't work.<\/p>\n It's okay as long as it's within 5 degrees<\/strong>That's what the book says, lol<\/p>\n If you use a pressure plate designed to adjust the angle of components such as tapered plates, you can achieve a larger angle.<\/p>\n Furthermore, if the angle is increased further, the calculations must be redone (including the structures under compression and the total load).<\/p>\n Please also take into account the effects of the groups above, below, to the left, and to the right.<\/p>\n \u2461 Increase the fixation length.<\/strong> If possible, it would be safer to reorder the material with a length that\u2019s about 1 to 2 meters longer. (Longer than that is also fine.)<\/p>\n The cost of materials is negligible. Once a section has been removed, there\u2019s a chance the surrounding soil has been disturbed, and anchors aren\u2019t a one-size-fits-all solution when it comes to changes in soil conditions.<\/p>\n The idea is to anchor it deeper than the original deepest point of the anchor.<\/p>\n \u2462 Grout is injected into the original hole.<\/strong> Since this could cause loosening, be sure to inject grout into the original hole after removing the bolt.<\/p>\n Even if drilling the free end involves partial overlap, I want to ensure that the anchorage section is located in a spot that is clearly different from the first hole.<\/p>\n \u2463 If the base layer is unstable, consider using a packer as well.<\/strong>\u00a0If you're on a mountain where cement slurry runoff is severe, be sure to consider this option.<\/p>\n <\/p>\n And one thing we mustn't forget is the paperwork.<\/p>\n It\u2019s only proper to officially notify the local government before redoing the work.<\/p>\n It\u2019s not impossible to keep it within the company or the prime contractor, but it\u2019s just kind of easier to just say it, lol.<\/p>\n For public works projects, changes to angles or anchorage lengths require a basis for stability calculations (from an administrative standpoint as well).<\/p>\n Although the fixing length is the same in the illustration, if you are setting up a new one, please move the fixing length further back.<\/p>\n <\/p>\n So far, I have covered everything from the removal procedure to determining whether to redo the work.<\/p>\n As I mentioned at the beginning, this kind of information isn\u2019t included in the ground anchor standards manual. This is purely based on Ent\u2019s experience.<\/p>\n After all, this is a world where staying in place is the bottom line.<\/p>\n But in reality, even if we were to drive 100 piles, there would only be about two test sections, and the soil conditions change the farther we go horizontally.<\/p>\n Even if you thoroughly clean the borehole and inject high-strength grout, it will still leak out when it\u2019s meant to (though of course, it\u2019s better if it doesn\u2019t!).<\/p>\n That\u2019s why I think the true skill of an anchor operator\u2014and the people who manage them\u2014lies in having a plan B so they don\u2019t panic when things go wrong.<\/p>\n Dealing with emergencies is truly a world of oral tradition.<\/p>\n I wish there was something like a \u201cCivil Engineering Failure Manual\u201d lol<\/p>\n To everyone across the country whose anchor came loose today! Let\u2019s steel ourselves and do our best!<\/p>\n <\/p>\n See you later.<\/p>\n Is it easier to understand if you skip the basic exam!?<\/a><\/p><\/blockquote>\nFirst of all, everything depends on \u201cwhere the leak is.\u201d<\/h3>\n
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