In: Civil Engineering
Answer:
given that
A corner of a five-story commercial building resting on a raft foundation settled down a few inches
1) Under pinning is technique to repair/strengthen the existing foundation of structure. Selection of under pinning method depend upon foundation type.
For current problem, under pinning using "Hicropies" will serve the issue of ground improvement.and reduce the settlement.Since "Hicropies" will transfer building loads to bearing layer.
2) Step by step procedure:-
Firstly problem of ecentricity causing settlement due to vertical loads need to check.Total expected vertical load is calculated & corresponding stress points are marked & location of Hicropies are located.
Step 1:-
Step 2:-
Step 3:-
(or)
step 3 may same times proceed by lowering of reinforcement lage & than grounding.
Step 4:-
Step 5:-
3) Advantage:-
1) Reduction is settlement, increase in bearing capacity of foundation due to increased soil structure interation & transfer of stress to bearable strata.
2) Micropile under pinning can be used in retricted headroom access.
Dis advantage:-
1) less lateral capacity when used without casing.
2) potential buckling at seismic condition.
3) costly method.
4) Inclusion of steel casings at micropiles periphery increases the cost which otherwise, if used only with steel case or steel bar at middle of micropile with grount can be economic.