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.