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Enquiry Title: REDR liasion

Enquirer: paulineregan

Status: Mailed-out

Skills: Geotechnical, Geology, Environmental, Construction, Civil, Building Services, Architecture, Agricultural, Maintenance, Mechanical, Project Management, Structural, Water & Wastewater Process.

Volunteers: 2 Volunteered, 0 Requested.


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Dear Engineeraid,
I am a member volunteer for REDR, and I believe a year or so ago we colaborated to support MSF. We have another request for design work that I hope you can help us with.
I hope we can relink in time to provide timely support for a camp in Sudan, requiring geatechnical design to support a water tank.
UNHCR, together with an implementing partner, is designing a water supply for a refugee camp in South Sudan. The camp is located in Pariang County, Unity State. The GPS coordinates of the middle of the camp are:
Lat 9.970540 Long 30.278130
The design of the system involves raising water storage tanks above ground level in order for the gravity system network of pipes to perform as required.
The type of tank being proposed is referred to as an Oxfam T95. This kind of tank has a 95m3 capacity and consists of corrugated steel sheets for walls and is lined with a rubber lining. The Oxfam code for the steel is T95S/2. The tank is 6.3m in diameter and 3m high.
The hydraulic design requires that the earth platform is raised a minimum of 3m above ground after any settlement. Therefore the design height needs to be greater than 3m.
Oxfam also provide an 8.23m diameter Tank Plinth (Code TP/1) but this can only raise a tank a maximum of 1.5m above ground level.
The area being set aside for tank storage is equal to a Family Plot which 20 x 20m. The final design must fit inside a 20 x 20 m square plot and leave a minimum of 1m path around the platform for access.
Some designs have been done using earth to make an earth platform. A Tank Platform can then be placed on the earth platform for the water storage tank to sit on. The earth proposed for the earth platform is widely available near the camp is a laterite. No tests have been done to date but the laterite is clay like and consists of very fine uniform particles. When moist it can be formed into a tube.

Technical Input Required
Technical calculations are needed to show the proposed (or amended) design has a suitable Safety Factor and is stable. From some initial rough estimates it is thought that geomembrane or a geogrid could improve the stability of the design. Product Data Sheets have been received from a supplier of geomembranes. However it been possible for the supplier to provide the calculations to show how the stability of the earth platform will improve with the use of their products.
We require a geotechnical expert to propose a design supported with the necessary engineering calculations that demonstrate that the design is stable enough for the intended use.

I trust the 2 number attachments have uploaded.

Many Thanks
Volunteer member REDR
Additional information :
Regarding the soil type we have not had the chance to do any tests on it. We don't have such a service here. I will ask our office in Nairobi again if it's possible there. It might be easier to send a sample back to the UK. Like I wrote in the brief the soil is a laterite. I'm attaching a borehole log from the site to give you details. They call it "marrum" put I believe it is a kind of laterite. This is not my field of expertise at all but to me it's consists of very fine uniform particles. When sightly wet it can be rolled into a tube which indicates it is very much clay like. The colour of this laterite it dark orange/red. It is not the dreaded 'black cotton soil'.

Please let me know if the support team known how best we can test this soil. Perhaps they know of a lab?
Latest info from enquiry:Please find attached a technical document I found relating the design of reinforced slopes. I believe this is the kind of analysis we are in need of. For example there is a section showing the calculations without reinforcement and another using reinforcement.

thanks and best wishes.

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