{"id":66134,"date":"2026-07-10T08:00:50","date_gmt":"2026-07-09T23:00:50","guid":{"rendered":"https:\/\/norimen.net\/?p=66134"},"modified":"2026-07-07T16:25:41","modified_gmt":"2026-07-07T07:25:41","slug":"set-a-loss-ground-anchor","status":"publish","type":"post","link":"https:\/\/norimen.net\/en\/set-loss-ground-anchor\/","title":{"rendered":"What Is Set Loss? | How Tension Stabilization of Ground Anchors Reduces Load and On-Site Countermeasures"},"content":{"rendered":"

Hello, everyone.<\/p>\n

This is Enta.<\/p>\n

Young engineers often ask me, \u201cIs set loss really necessary?\u201d<\/p>\n

I see. Even though the term \u201cset loss\u201d is thrown around all the time on set, there are actually a lot of people who\u2019ve never had it properly explained to them, huh?<\/p>\n

I\u2019m one of those people who, way back when, read the Ground Anchor Design and Construction Guidelines, tried them out, asked around, and finally got it to click, lol.<\/p>\n

But that's beside the point.<\/p>\n

In this post, I\u2019ll provide a comprehensive explanation of \u201cset loss\u201d\u2014from how it works to practical solutions on the job site, and even my own personal theory.<\/p>\n

It\u2019s no exaggeration to say that the quality of ground anchors depends on proper tensioning, so young construction managers should definitely keep this in mind.<\/p>\n

What Is Set Loss? | The Mechanism Behind the Drop in Load at the Moment of Setting<\/h3>\n

In a nutshell, set loss is...A phenomenon in which the load during the service life falls below the planned level due to stress stabilization<\/strong>That's what it's about.<\/p>\n

There is a diagram illustrating this load reduction on around page 79 of the Design and Construction Standards for Ground Anchors.<\/p>\n

I'll explain what's happening step by step.<\/p>\n

Tighten the jack \u2193 Insert a wedge into the anchor head \u2193 Release the jack \u2193 The wedge gets wedged in (this is set loss)<\/strong> \u2193 The load drops below the specified load by the amount it has sunk \u2193<\/p>\n

Furthermore, the PC strands loosen due to relaxation \u2193 The load drops even lower than the specified value \u2193 It can\u2019t be held at 100% of the intended force (I\u2019m exaggerating a bit, lol)<\/p>\n

Basically, even if you apply a load with the jack that\u2019s \u201cperfect\u2014100 points!\u201d, the moment you drive the wedge in and remove the jack, your score drops by the amount the material has been indented.<\/p>\n

On top of that, there\u2019s also the relaxation caused by the steel wire itself gradually loosening.<\/p>\n

Incidentally, the test method for relaxation is specified by JIS (Test Method for Tensile Relaxation of Metallic Materials), but,<\/p>\n

That\u2019s something you do in a lab using short test specimens, so it\u2019s a whole different world from actual anchors on-site, lol.<\/p>\n

*I'll write more about relaxation in my next post.<\/p>\n

\"Ground<\/p>\n

Basics of Test Preparation | Anticipating Mistakes and Staying Focused: 4 Ways to Master the Material<\/h3>\n

The basic approach to addressing set loss is,I tense up from the start, taking into account the relaxation of the steel wire and set loss.<\/strong>That's the thing.<\/p>\n

It's the idea of adding the amount of the drop in advance, isn't it?<\/p>\n

Let\u2019s consider a specific method for securing a tension connection\u2014for example, in the case of a wedge-type connection (wedge and ring) with a design load of 100 kN.<\/p>\n

 <\/p>\n

Step 1: Apply a load of 100 kN and secure it in place. (This is the most common method.)<\/strong><\/p>\n

Step 2: Calculate the value taking set loss into account, add a margin such as 110 kN, and tension the anchor to set it in place.<\/strong><\/p>\n

Point 3: The anchor will be fully tensioned at approximately 80% of the design load. (Since this will amount to about 80% of the design load even under 100% loading\u2014and given that relaxation also occurs\u2014I think it\u2019s okay to disregard this.)<\/strong><\/p>\n

Step 4: Apply a load of 100 kN, then unload the jack once; reapply a load of 100 kN, and then secure it in place.<\/strong><\/p>\n

I think what\u2019s happening on-site is generally either option 1 or option 2.<\/p>\n

However, what I think is the best isPart 4<\/strong>That's it.<\/p>\n

A method for securing the wedge by first driving it firmly into place to minimize any loss as much as possible.<\/p>\n

The idea is to let it sink in first. (Note: This applies only to models equipped with a wedge and ring.)<\/p>\n

On the other hand, that third figure alone isn't very good. Since it will gradually increase after the service begins, there's a possibility it could fall even below 80%.<\/p>\n

But since the anchor is in a completely passive state, there's plenty of leeway even if the slope starts to slide.<\/p>\n

However, since the tension is weaker, the degree of relaxation is reduced accordingly, so in reality, there may not be much of a difference.<\/p>\n

The template for managing set loss is available in the \"Downloads\" section of our (Shioda Development Co., Ltd.) website, so please feel free to use it if you need it.<\/p>\n

\"Consolidation<\/p>\n

Pitfalls on Site | Without Sufficient Bearing Capacity, the Load-Bearing Slab Will Settle, Leading to Increased Losses<\/h3>\n

Even if you understand how it works and what measures to take, there\u2019s another pitfall to watch out for on the ground.Bearing Capacity<\/strong>That's it.<\/p>\n

If there is no bearing capacity under tension, the structure under compression will settle.<\/p>\n

Since the design concept is for the structural frame to bear the load as a whole, a slight settlement isn't a problem, and the gravity retaining wall basically won't shift at all (it would be a huge problem if it moved here, lol).<\/p>\n

The biggest problem isPressure-receiving plate<\/strong>That's it.<\/p>\n

There are various types of bearing plates, but all of them will inevitably sink if there is no bearing capacity in the ground.<\/p>\n

At a job site with poor surface conditions that I worked on, the ground subsided by more than 10 cm.<\/p>\n

At this point, it was clearly a case of insufficient bearing area, but once we\u2019re in the construction phase, it\u2019s practically impossible to make changes to the load-bearing structure. That\u2019s just how design works, and the materials have already arrived, lol.<\/p>\n

If the pressure plate continues to sink, there is a possibility that the design anchor force will decrease significantly.<\/p>\n

In other words,In addition to settlement loss and relaxation, the load is also dissipated due to settlement of the ground.<\/strong>That\u2019s what makes it a triple whammy.<\/p>\n

To address this type of soil, we use a method in which we fill sandbags with improved soil (soil mixed with a cement-based stabilizer) and stack them around and beneath the load-bearing plate.<\/p>\n

When placed in sandbags, the soil forms a solid mass that is less likely to crumble. If a load-bearing plate is installed on top and tension is applied before the stabilized soil hardens, the sandbags will settle into the natural ground.<\/p>\n

And above all, on ground like this,Take as much time as possible to let it sink in<\/strong>... While waiting for the sinking to subside.<\/p>\n

*The sandbags are UV-resistant, filled with cement-amended material, and should be positioned slightly wider than the load-bearing plate.<\/p>\n

\"Load-bearing<\/p>\n

When it comes to tensioning methods in ground anchor construction, there are many different approaches and ways of thinking among engineers.<\/p>\n

There are so many things you can only understand through experience.<\/p>\n

 <\/p>\n

I\u2019ve been writing about how set loss works and how to deal with it, but finally, here\u2019s my honest opinion lol<\/p>\n

To be honest, there\u2019s a part of me that\u2019s always wondered, \u201cDo we really need to worry about set loss?\u201d lol<\/p>\n

That's because, rather than being extremely tense at 100%, it's better to settle at around 80%, which is the design load, andStandby Type<\/strong>That's because I think it's better to leave it that way\u2014that's how it's supposed to be.<\/p>\n

If the mountain is temporarily displaced by an earthquake or similar event while it is locked in the 100% state, it may become slightly overstretched, similar to the 110% state.<\/p>\n

Excessive tension can lead to uneven load distribution or breakage.<\/p>\n

\"Treatment<\/p>\n

*The head of an anchor that has become overly tight*<\/p>\n

In fact, I\u2019ve seen sites where excessive tension in a landslide-prone area caused deformation in the adjacent anchors, and I\u2019ve also had to relieve the load on an over-tensioned anchor and retension it. (Disconnection followed by reconnection)<\/p>\n

Keep it around 80% to be prepared for emergencies. In the event of an emergency, the mountain will be securely anchored, and even then, it will remain within about 100%.<\/p>\n

So, in my personal opinion,Using the method described in Part 4 (unloading and reloading) to minimize losses, while taking set loss into account, a range of approximately 80% to 90% of the design load is appropriate.<\/strong>That's the idea.<\/p>\n

However, this depends on the installer\u2019s judgment, and there\u2019s no single \u201cright answer\u201d in this field.<\/p>\n

There are also matters to discuss with government agencies and design considerations to balance (and government agencies are highly unlikely to approve anything that falls below the safety factor).<\/p>\n

Consultants don't know about that kind of thing, so they're not too keen on it lol<\/p>\n

The more I learn, the less I understand. Civil engineering is really interesting, isn't it!? lol<\/p>\n

 <\/p>\n

See you later.<\/p>\n

If the ground doesn't have sufficient bearing capacity, the load will be transferred elsewhere.<\/a><\/p><\/blockquote>\n