Week one 21/05/13

Today I went to Quedgeley for my first day at the Geotechnical Academy. I was met by Amanda who was absolutely lovely and really helpful. I met lots of people: Jade who currently works for geotechnical and is really nice, Gareth who works for Hydrock in Plymouth and was friendly, Michael who works for Amey inGlasgow and who was also really friendly and discovered David from Plymouth was there too! There was also Alex, Will, Steve and Ramin, who I didn't really speak to.

Pete, who was the lecturer from Equipe was also very friendly and very chatty. He went through a series of topics which included Eurocode (the standard of work for the Geotechnical industry - a topic that came up frequently!) and also the below (taken from my notes of the morning):

- The factor of safety (I think this is the numerical margin of error) has been changed from 3 to 1.4. This means that the eventual number is higher meaning a wider error margin is given (I think).
- Try to avoid drilling waterlogged sand lenses in glacial till as the mixture floods out leaving a hole which can cause unstability if there is a building above. This can be dealt with using either compressed air or grouting. Both methods 'plug' the sand, however the former has health and safety considerations.
- Ensure walls are built for purpose (if they are to stop landslides they need to be designed appropriately otherwise they will fracture under the pressure.
- Shrinkage/swelling of a clay foundation can cause wall cracks. This is not an issue uless you can see through the crack.
- Foundation failure is when the load exceeds the ability of the soil to support it.
- Differential settlement of the foundation soil can cause instability in buildings.
- A good site investigation is vital as a lot of extra costs are incurred because the initial investigation/interpretation was poor. Although an example was given of a driller who drilled into the above sand lense, didn't realise the severity of the situation and caused instability to some guy's house which was eventually demolished. This was because he did not read the report.
- Jobs are often a case of budget allowance vs quality.
- The aims for the site investigation are: 1) supply information for design, construction, temporary working (the actal construction process which can involve adequate support for any machinery) and contamination and 2) to avoid later issues.
- Mineshafts are not always mapped (especially when coal is close to the surface: people saw this as an easy way to get fuel).
- Mines are not always coal. There can be flint, salt, mineral mines etc. If the local buildings appear to be made of flint there is likely a local mine.
- Looking at the local stone/building materials (if possible) gives an indication of the area.
- The reports you write are the responsibility of the writer and not the company (to an extent: the company has to make sure you are competent.)
- Samples are classed with a rating of 1 - 5 where 1 is as undisturbed as possible. This is easiest if the sample is taken close to the surface.
- Investigations are made up of three stages: 1) the desk study and site survey, 2) the detailed investigation of the ground, topographic/hydrographic survey and site specific details and 3) a focussed investigation of the site.
- Things to note when doing a site investigationL drainage, access, seasonal issues and the moisture content of the ground. This usually peaks approximately 2/3m below the surface and then decreases uniformly from about 5/6m downward.
- When taking measurements etc. a change in the climate is important. Ensure a note of the weather on the day of the investigation and also in the past week or so as this can impact the results.
- A wet foundation can make the sediment soft which later causes instability and cracking.
- Some methods of investigation: window sampling, dynamite probing, trial pitting, geophysics, cable percussion (shell and auger) boring and rotary drilling (core/non core).
- Old reports may not be accurate.
- The minimum boring depth should be 1.5-2m from the base of the foundation x the width of the foundation.

After we went on a tour of the building and then had another talk, although I do not have notes for this later session as it mostly consisted of a discussion between Pete and Liz about frustrating things that happen at sites, such as asbestos and other contaminants, things that are not expected (Gareth had a good example of a suprise petrol and paraffin tank on a builidng that was being destroyed) and other such things.

Overall I think it was an interesting day and tiring. I wish that Pete was a bit more consistant on his powerpoint as it seemed to hop around the topic rather but I really appreciated the anecdotes.