Tony Geldart

[Tony Geldart]

Would anyone know the worst ground condition in Melbourne and the kPa rating that would be required from a trench shield at say 6000mm depth.  I require the information for our trench shoring system LITE guard.  With this information we can state that anywhere in Melbourne at up to  6000mm depth the worst case scenario would be 50kPa or 80kPa and supply shoring to suit. Over 6000mm we would then recommend a soil report and engineering for a suitable shoring system. This knowledge would make it much easier for contractors to ensure they get suitable shoring every time  if they cover for this depth and WLL.

Any information would be appreciated.

[Rahsn]

Tony,

Sounds like you need an engineer.

Say a 40 kPa box at 6 m in loose sand if there is no surcharge loading.

Rahsn

[Tony Geldart]

Thanks Rahsn , you are correct, we used to have an in house engineer, but unfortunately we no longer have full time work for an engineer.  

I would have thought that Coode island silt wet ground would be higher than 40kPa

Thanks Tony

[Barnabas Ilko]

@Tony Geldart, just a few other items you might want to consider:

• You will need to consider time and how long the shoring box is going to be used in a particular location
• You will need to allow for potential water pressure or saturated material
• you will also need to consider nominal surcharge loads around the trench (this might be stockpiled material, vehicular loading or other)
• The best would probably be to use a K0 value for the calculation of the pressure (this might lead to higher than 40kPa pressure though)

All in all the best option might be to have a table of certain load cases for various depths and have 2, 3 or 4 types of shoring boxes. This might be more economical, easier and compacter to transport and easier to handle on site.

[Tony Geldart]

Thanks Barnabas,

I was hoping that someone could say the worst ground in Melbourne would be ( say Coode Island silt) and that would be 50kPa, on top of that we always allow minimum 10kPa for machinery and some times up to 20kPa.  Short term shoring in the ground is up to two weeks.  Most jobs are pipe laying, manholes or small pre cast pump stations, which would all fall into the two week program.

 

In the USA they have tabulated data in PSF, which is used up to 6000mm in depth any where in the USA, over 6000mm they require Temporary works designs. I was hoping for something similar, as this would make life safer and easier for contractors.

 

We have shields  from 1200mm, 2400, 3000, 3600, 4000,5000,6000,6600 to 7200mm long with WLL  from 20kPa to 120kPa (on the 4000mm box)

Anyone else got any thoughts on this for me?

Appreciate you help.

 

Tony