NZ Geomechanics News

Introducing the clip on-clip off RockAnvil for Scala Penetrometer

The Scala Penetrometer (SP) or Dynamic Cone Penetrometer (DCP) is a tool used to measure the penetration resistance of in-situ soils. It is an arbitrary method of testing soils, but it is used for its cost effectiveness, durability and efficiency in which results can be obtained for a site. The results can also be converted into a California Bearing Ratio (CBR) estimation which is useful for the design of pavements and roading.

The equipment itself was developed by A.J. Scala in 1956 but the concept has been around for generations. Since its development it has been widely used and accepted across New Zealand and Australia and has been incorporated into the Australia Test Method Standard CRB 402.01 and Standards New Zealand NZS 4402 Test 6.5.2:1998.

Scala Overview

The anvil component of the equipment is a standard, hardened steel threaded attachment that connects the ‘Guide Rod’ and ‘Drop Weight’ with the ‘Penetrating Rod’.

It is evident that the process of screwing the anvil onto each penetrating rod is hard work and time consuming. As most people who have used this equipment would agree, the thread can become easily damaged or can become clogged with soil which makes the process significantly harder and more time consuming. The threaded connection can cause repetitive strain injuries (RSI’s) to users as the screwing process requires repetitive movement of the wrist and forearm every time the equipment is screwed on and off each penetrating rod. This threaded connection also allows for one significant misuse of the equipment; ‘reverse scala-ing’. This is the (incorrect) process by which the weight is used to hit the ‘stop’ in order to bring out the penetrated rods. This process significantly increases the chance of equipment breakage and may also cause significant bodily harm.

These disadvantages of the existing anvil led to creation of an innovative product that could solve these issues whilst still providing the necessary specifications to meet the NZ standards.

In 2018 Robert Smith and Jack Farrow embarked on a mission to create a product that would attach to each ‘penetrating rod’ quickly and effectively and that could retro fit to existing equipment across the industry. It also needed to be able to improve the Health and Safety flaws with the original anvil. Thus, the innovative RockAnvil
was developed.

The RockAnvil works by having an elongated neck with a ‘spring steel’ clip near the bottom that locks into the groove on every ‘penetrating rod’. These grooves on each penetrating rod are there to disconnect any rods that may become stuck with spanners. The spring steel clip on the RockAnvil uses this ‘groove’ to connect the anvil onto each rod. Using a lower strength of steel for the clips allows for the anvil to be turned and the clip to be pushed wider in order to easily connect and disconnect the anvil, weight and guide rod.

The RockAnvil solves the primary issues with the original Anvil. The ‘clip & twist’ locking mechanism is a fast and easy method for testing with multiple ‘penetrating rods’. This is because the anvil no longer needs to be screwed and un-screwed onto each rod and is instead simply pushed, twisted and pulled on and off each rod, significantly decreasing the time it takes to use this equipment. This also reduces any RSI’s associated with the threaded connection of the original anvil.

The RockAnvil does not allow the user to ‘reverse scala’ as the ‘spring steel clip’ at the base of the anvil will either break or disconnect from the penetrating rods if significant force is applied to the ‘stop’ on the guide rod. This, in turn, reduces the Health and Safety hazards associated with using the Scala Penetrometer as users can no longer inappropriately use the equipment to ‘reverse scala’.
The ‘spring steel clip’ also reduces breakages as the stress of the hammering weight is no longer applied to the threaded connection.

It has been found that Scala equipment in use across New Zealand often shows minor variations between sets with differences in the diameter of the ‘penetrating rod’, the length of the ‘guide rod’ and other variations. To overcome such fix issues with the differing Scala rod sizing, RockAnvils Limited has developed the Mark II of the Anvil.

Miyamoto, LDE, Rileys and Coffey are among the consultancies that tested the equipment. There was great positive feedback success with many confirming that the RockAnvil helped users in the field.

RockAnvils has provided its product to many more consultancies throughout New Zealand and is looking at further redesigning and improving the product. Other aspects of the equipment are also being investigated to help users quickly and safely use the Scala Penetrometer. RockAnvils Limited is always looking for more companies to try out the equipment and provide feedback and would welcome anyone to get in touch for more information or to order some RockAnvils to try.

Check out the website at and/or contact or for further information.




Tags : #in-situ testing#Scala

NZ Geomechanics News
Jack Farrow, Robert Smith
NZ Geomechanics News>Issue 99 – June 2020

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