Topic 2a Flashcards
types of foundation
shallow and deep
types of settlement
uniform and differential
describe excessive uniform settlement
damages services like pipes, cables entering buildings and pavements
describe excessive differential settlement
damage to structural elements such as beams and columns, more dangerous than uniform settlement and limited to only 25mm
describe shallow foundation
transfers vertical loads by direct bearing on soil close to bottom of the supported structure and a short distance below ground surface
types of shallow foundation
continuous strip wall footing, isolated footing, combined footing, raft or mat foundation
describe continuous strip wall footing
used for walls, resist sliding/overturning and spans over uneven ground
why does isolated footing have to be reinforced
footing must be reinforced in 2 directions as there is a cantilever effect from the concentrated column loading at the center
types of forces acting on isolated footing
column load, weight of backfill, weight of column stump
where is combined footing used
for closely spaced columns supported by a single column and occurs where columns are close to other construction
describe raft or mat foundation
large footing supporting several columns on 2 or more rows and has one big pad for the whole structure
where is raft or mat foundation used
where soil has low bearing capacity
describe the method of constructing footing
- mark out position of footing
- excavate soil to RL of the bottom of footing using backactor
- lay a layer of lean concrete at the bottom for a good working platform
- fabricate and install formwork and steel cage for footing
- after inspection for formwork sturdiness and correct no. of rebars, casting of concrete can proceed
m/e for surveying
automatic level, theodoline, plumb line
manpower for surveying
surveyor, surveying assistant
