Resin-Grouted Rebar Bolt vs Mechanical Expansion Shell Anchor

Quick Comparison

Neither system is universally better.

The correct choice depends on geology, support design and installation requirements.

How a Resin-Grouted Rebar Bolt Works

Normally when you install a resin bolt you will.

• Drill your hole.
• Place resin cartridges.
• Screw bolt into the resin.
• Resin is mixed together.
• Allow to set.
• Install plate and nut.

Load is carried through the steel bolt to the resin to the rock.

With resin bolts you can get grout along most of your bolt length.

Because of this ability they are very common when trying to support bedded/fracture rock.

Wanfeng has Mining Resin Anchoring Agent for use with rock bolts.

How does a Mechanical Expansion Shell work?

The expansion-shell bolt will anchor towards the bottom of the hole.

By tightening the bolt it will force the expansion shell outwards.

Allowing the bolt to create an anchorage.

Once the bolt has been tensioned between the anchor and the bearing plate you have a mechanical anchor.

Expansion Shell –> Bolt –> Bearing Plate

Which can be used when pretensioning of the bolt is required and you have good rock at your anchor depth.

Difference between distributed bond and point anchorage.

As mentioned before this is what they differ on most.

Resin Grouted Bolt.

Has the ability to have load distributed over its bonded length.

Some of these are.

• Greater area for load to be transferred.
• Ability to reinforce through a fracture or bedding plane.
• Less reliance on one anchorage point.

Mechanical Expansion Shell.

Transfers load at the point of the anchor.

Some of these are.

• Mechanically engages with rock mass.
• Can be preloaded.
• Quicker install if rock mass allows.

It all depends on what you expect the rock to do.

Installation Differences

Resin Grouted Rebar Bolt.

There are many variables to consider when installing a resin rebar bolt.

• Bore hole size.
• Rebar diameter.
• Size of resin cartridge.
• Length of resin.
• Set time of resin.
• Mix time.
• Temperature.
• Cleanliness of borehole.

If your rebar bolt is not properly mixed or surrounded by resin it will not perform as expected no matter how strong the steel bar is.

Mechanical Expansion Shell.

There are some key variables that should be considered.

• Bore hole size.
• Size of expansion shell.
• Competence of rock.
• Location of anchor.
• Proper tightening.
• Seat of bearing plate.

If your rock mass is not competent enough to allow your anchor to expand properly then it will not hold.

What provides quicker support?

A mechanical expansion shell once it’s properly engaged and tightened can give you support right away.

A resin bolt relies on how quick your resin can set.

Quick set resins can provide fast anchorage as well just depends on the type of resin used.

So mechanical anchors give you instant support and resin bolts give you fast support.

Which one will give you support quicker?

When installed correctly and tightened down a mechanical expansion shell will give you support straight away.

With a resin grouted bolt you have to wait for the resin to set.

Depends what resin your using as some can set very quick. But as stated above it all depends.

I would say it would be.

Mechical will give you support straight away

Resin will give you support quickly once its cured

Which to use in weak rock?

There isn’t a definitive answer to this.

Expansion shells will require good rock around your anchoring area.

If the local rock mass is poor you may find that you cannot rely on the anchor holding.

Using a resin grouted bolt will give you a longer length to hold with which could be beneficial if you don’t want to rely on your anchorage point.

Again if your rock is poor, the bore hole or installation method is not done correctly then you can compromise your resin anchorage.

If you are working in very poor ground you may need to consider a different product ie self drilling anchor.

Read: Self-Drilling Anchor vs Rock Bolt

Problems that can occur when using resin grouted bolts

• Poor mixing of resin
• Not enough resin
•  Hole and bolt diameter not correct
•  Borehole not drilled correctly
•  Poor bond between resin and rock
• Installed too soon

Could be within the bolt, resin or rock.

Problems that can occur when using expansion shell anchors

• Poor rock where anchor is to be installed
• Borehole to large
• Borehole out of round
• Shell not gripping hole
• Anchor slipping while under tension

As there is only a small area being anchored it is important that the rock around the shell is good quality.

Cost Comparison

It is not easy to say what system will be the cheapest.

You have to consider the installed cost which is made up of

Resin Grouted Bolt

• Bolt
• Resin Cartridge
• Drilling
• Time to mix and install
• Quality Assurance

Mechanical Expansion Shell

• Bolt
• Expansion Shell
• Drilling
• Tighten/Tension
• Check that its been installed correctly

So price should be looked at as the cost of each correctly installed system.

دليل الاختيار

When To Use Resin Grouted Bar Bolts

• If you require distributed anchor
• If you want to use full column bars
• Resin can be used as part of your mining cycle
• Rock conditions allow for the use of resin grouted reinforcement

When To Use Mechanical Expansion Shell Anchors

• You have good rock at your point of anchor
• Mechanical pre-tension is desirable
• Instant anchoring is needed
• Point anchoring is suitable

Use Something Else If

• Borehole is collapsing
• You are expecting high deformations
• Dynamic forces are an issue
• You need deeper reinforcement

Other systems to look at may be:

• Friction Bolts
• Self drilling
• Cable bolt
• Yield bolt

See Mining Ground Support Systems for more information on what systems are available.

What You Should Know Before Placing A RFQ For A Resin Bolt Vs Mechanical Anchor

List the following when requesting a quote.

• طلب
• Size of bar
• طول القضيب
• نوع الفولاذ
• Requirements for the bolt
• Size of hole
• Type of resin or expansion shell
• Washer Size
• Nut specification
• الحماية من التآكل
• How much tension you need (if applicable)
• Drawings

By doing this you will minimize the chances of ordering something you can’t use.

View All Wanfeng Rock Bolting & Anchoring Systems.

التعليمات

Q1: Will a resin grouted bolt be stronger than a mechanical bolt?

Its not always going to be stronger. Both use different methods of anchoring so it will depend on the bolt type, rock mass, borehole and how its installed.

Q2: What is the difference?

Resin grouted bolts have a bonded length to help support the rock mass. Where as mechanical bolts mainly rely on one mechanical anchor.

Q3: What supports the roof immediately?

If you have mechanical expansion shells installed correctly they will provide an immediate mechanical anchor. Resin bolts need to cure.

Q4: What should I use if the rock is weak?

Mechical shells need a good rock mass at the anchor point. Grouted bolts will help spread the load out but can also fail in weak rock mass.

Q5: Can you grout a mechanical bolt?

Yes some systems can be designed to use both a mechanical anchor and grout.

Q6: Are resin bolts always fully grouted?

No you can use resin as a point anchor or grouted for part of the length.

Conclusion

There are many factors when choosing what bolt to install but one thing to remember is the difference between a resin grouted rebar and mechanical expansion shell anchor.

Resin grouted bolts will provide a distributed length of bond.

Mechanical expansion shell anchors provide an anchor point and can be preloaded.

They both have their uses.

Ground Condition > Type of Anchor > Borehole Condition > Do you need to preload > How will it be installed > Installed cost.