A detailed report by Dr Christian Spring, of the world renowned Sports Turf Research Institute, has endorsed the GBGB’s deep harrowing protocol.

The findings are produced in a brief summary below (the full scientific findings and methodology runs to dozens of pages) and offer plenty of useful guidance including:

– the importance of monitoring the speed and depth of harrowing

– the dangers of compaction using heavy vehicles on the surface

– the differing frequency requirement for harrowing, based on sand types

– the benefits of using equipment in monitoring sand compaction

– the importance of correct reconsolidation after harrowing

THE STUDY

The objectives of the research were:

  • To assess the efficacy of decompactive maintenance of removing, or at least reducing, the

influence of hardpans within the profile of greyhound racing tracks.

  • To investigate the effect of sand type on the extent of hardpan formation and the efficacy of

renovation techniques.

  • To evaluate track specific effects on hardpans and decompactive maintenance, including

differences among tracks and variation both around and across tracks.

Six tracks were visited during the summer of 2014 (Track A, Track B, Track C, Track D, Track E and Track

F). Of these tracks Track A, Track B and Track C all used 26D sand, whilst Track D and Track F used

Pegasus sand and Track E used Kings Lynn Fines.

At each venue, the track surface was assessed before and after power harrowing and subsequent repacking

and surface preparation. Data measured before maintenance would have represented the

point when track hardpans would have been at their worst. Data measured afterwards allowed the

relative efficacy of the decompactive maintenance at either removing, or reducing the influence of

any hardpans, within the track profile. At each track, the remedialmaintenance operations carried out

after power harrowing, were based on those normally used at each individual track.

Data were collected at 10 locations along a straight and a bend, giving a total of 20 test plots round

the track. Within each of the 20 test plots, readings were taken across the width of the track, which

corresponded to the inside, middle and outside of the main racing area. These data allowed the

variation both along and across the six tracks to be characterised.

The assessments carried out included the following:

  • Surface hardness – measured with after one and four drops of the 2.25 kg Clegg Impact

Hammer.

  • Penetration depth – measured using the Longchamp Penetrometer to measured compaction

through the profile (the further the penetrometer enters the track the less compact the sand).

  • Hardpan depth – measured by inserting a probe into the track and recording the depth at

which the hardpan was felt.

  • Sand bulk density – measured as the weight of solid material in a known volume from intact

cores taken from the track at two depths (0-40 mm and 40-80 mm).

  • Shear strength – measured with a Geonor Shear Vane fitted the 50 mm long vane, which

measured shear strength as the pressure required to cause the mechanical strength of the

sand to fail.

  • Volumetric water content – measured using a Delta-T devices Theta Probe.

Conclusions

Extent of hardpan formation

  • There was variation in the depth of hardpan among the six tracks.
  • Track C, Track A and Track D tended to have the greatest levels of compaction and shallowest

hardpans, as compared to the other tracks.

  • There were a number of factors that would be likely to effect the extent of hardpan formation

and include, frequency of power harrowing, depth at which power harrowing was carried out,

forward speedwhen power harrowing and re-packing the sand, levels of track usage/vehicular

traffic and the level and type of post power harrowing maintenance.

Effects of maintenance

  • Power harrowing reduced compaction at each track and increased the depth of uncompacted

sand over the hardpan.

  • The equipment now used in track preparation (particularly the power harrow) and

methodologies followed for decompactive maintenance seems to be appropriate for dealing

with hardpan formation, both from data collected during the study and based on

understanding historical track preparation techniques.

  • There was some variation in effect among the six tracks, with the maintenance operations at

Track F, Track B and Track E seeming to have the greatest decompactive effect.

  • Care should be taken when carrying out track decompaction that the hardpan has effectively

been broken up to a sufficient depth with the power harrow and that the track is carefully

reconsolidated according to the methodologies set out in the GBGB track maintenance

manual. This is to ensure that the necessary consolidation of the surface after power

harrowing is effective and even both around and across the track.

  • The frequency of power harrowing at tracks should be determined entirely by the rate at

which the sand becomes compacted. The depth to the hardpan should be routinely monitored

at tracks using a standard procedure and tool (such as a penetrometer or standardised probe).

This will then provide objective information to indicate when power harrowing is required.

  • The speed at which equipment travels around the track needs to be carefully monitored to

ensure that the operations being carried out are as effective as possible. It is possible that if

the forward speed of a vehicle is too fast, the efficacy of the operation could be affected. This

would certainly affect power harrowing, where if the power harrow was being pulled too

quickly, it would be unlikely to fully decompact the surface. This would be due to either it

riding over the hardpan or not completely breaking up the chunks of hardpan that had been

broken off.

  • There was evidence that the amount of re-packing work should be carefully monitored. There

were sections of certain tracks, mainly in the middle of the track width, where compaction

levels had starting to increase again as a result of the double tyre traffic in this area.

  • It appears that one of the main causes for the formation of the hardpan is the movement of

heavy vehicular traffic around the track. Care should be taken to a) minimise traffic on the

racing surface and b) ensure appropriate mitigation procedures are in place to prevent over

compaction of the surface, such as using light weight equipment and tractors with the low

pressure/wide profile tyres.

Greyhound Board of Great Britain IN103883/3 4

  • It is important for tracks to continuously monitor maintenance equipment, especially power

harrows, to ensure that tine wear is not excessive and that the tines can actually reach the

hardpan layers.

Effect of sand type

  • Sand type did appear to affect the overall level of compaction on tracks.
  • Those tracks constructedwith 26D tended to have greater levels of compaction, in comparison

to the other sand types tested.

  • The 26D did appear to pack more densely than some of the other sand types, particularly in

comparison to the Kings Lynn Fines at Track E.

Variation in compaction around and across the tracks

  • There was significant variation in the extent of hardpan formation and the effect of

maintenance around and across tracks.

  • Whilst there were no consistent differences between straights and bends among all six tracks,

there was an indication the compaction tended to be more severe on bends.

  • The inside of tracks tended to suffer the least compaction, whilst some tracks tended to have

the most compaction in the middle and/or the outside of the racing area.

  • It would be advisable for groundstaff to closely monitor compaction in the middle of tracks,

as it will be these areas where the hardpan will be closer to the surface, as a result of double

the amount of tyre traffic when carrying out maintenance.