New School foundations

Yesterday we had a visitor - Ed, Max's dad. He was here to have a look at a new drilling method.
There are lots of machines and people digging holes in our field. They are trying out new testing methods of foundations.
Ed told us -

• they are looking for the hardest layer in the ground to put the foundations on   
• this is so if there is another big earthquake the liquefaction wont come up through the concrete
• they are going to make the foundations thicker so hopefully the concrete wont crack during an earthquake
• cement is made out of limestone, you have to stir it up in a machine
• some of the men testing the ground were looking at graphs about how hard the ground was and how many large shakes it would take to move it
• School foundations are harder than house foundations
• they are mixing the cement with the dirt from in the ground
• the holes are 5 m deep
• they are using a rotary mixing head 
• when they were using the rotary mixing head mixer water and silt was bubbling up
• steam was coming off the rotary mixer because it was going so fast 
•