Its a multi-floor block of 8 flats built 6 years ago but on a wrong foundation type for such building and soil type. I will give a brief description of every aspect of the building before the reconstruction works:

CONTRACTOR: KDI Structures Ltd.
CLIENT: Can't disclose for want of Security.
PROJECT TITLE: Reconstruction of the failed section of a multi-floor 3 bedroom block of 8 flats.
LOCATION: Umuahia, Abia State.
PROJECT COST: N16.7million
DURATION: 4 months (This is because the works will be done in stages to ensure the curing duration for every concrete work is met before any other work is carried out).
BUILDING SIZE: 26.7m X 11.2m.
NATURE OF THE SITE: Sloppy with very shallow ground water level.

Geotechnical analysis has been done on the site and below are the results:
Ground water level: 1m at BH2 & 1.5m at BH1.
Particle size distribution: Sandy-clay to Pure shale seen between 0.5m - 4m at BH1 and Sandy-clay to shale seen between 0.5m - 3.2m at BH2. the top soil showed a high level of moisture at 0.2m - 0.5m at BH2.
Soil Load Bearing Capacity: 32kN/m2 - 310kN/m2

Structural Engineering Analysis carried out on the building revealed that the total Load from the building is 200kN/m2 which is within the laod bearing capacity range of the Soil.

FOUNDATION TYPE: Strip foundation with varying depth of 5ft - 6.7ft at different points because of the slope but the mistake was the chaining beam wasn't anchored to the columns and the foundation beam wasn't reinforced. The entire building foundation is immersed in ground water to a depth level of 1.5m - 2.2m from the north elevation to the south elevation. due to this reasons, DIFFERENTIAL SETTLEMENT took place shown by multiple structural failures and massive cracks, entire failure of the front section of the foundation, slight tilting of the entire building, failure of the DPC section at the sitting and dinning room for the 2 ground floor flats.

To avert further failure, Anchor bars has been place at a spacing not greater that 450mm at the every point in the ground floor and to also serve as a means of artificial support system to permit for reconstruction works.

More Pictures...

Going Further, after an indepth analysis, we've decided to to tackle the project headlong but in stages as listed below:

First Stage: Insert massive columns with a large base. The Columns measure: 500mm x 225mm with a total length of 15ft and the column base measuring: 1500mm x 1500mm x 300mm sitting on a concrete blinding of 50mm and a Sharp Sand base of 200mm to resist movement.

Second Stage: Construct and Place 3000mm x 1200mm x 300mm massive Sub-surface retaining drain like wall 5m from the north elevation of the building. This Sub-Surface retaining drain like wall will span a total of 50m, this is to prevent the ground water moving from the top of the slope to make contact with the building foundation.

Third Stage: Tear down the existing front foundation with the ground floor super-structure only at the front and Rework the entire front foundation measuring 26.7m to the both sides measuring 2.7m each. Raise the super-structure again, Under-pin some section of the partitioning walls in the ground floor, unearth the foundation filling at some points and refill, compact and cast the DPC. Reinforce 10 existing columns in the building and finally, finish the ground floor.

We Quickly re-drew the architectural drawing of the house so as to produce the structural drawing and as well insert our supporting columns.

We have longed mobilized to site with the needed materials having arrived as required. Me and some of my team analyzing the building and taking measurement.

What a mistake at the initial stage?

good job

umuokezie:
good job

Thank you Sir

PeoplesArmy:
What a mistake at the initial stage?

Terrible Construction mistake.

Will post more later as work is currently on-going at site...

Starting the first face of reinforcing and strengthening the house with double size columns, the Fitter and the Carpenter gets to work bending the reinforcement rods according to the bending schedule and the carpenter forming the wood-works.

The columns thickness are meant to flush with the existing walls so as not to deface the house. Our action are to present the building as new building at the end without anyone suspecting that it was worked on.

More....

Notice:
For the Column Base, we are using Y12 and for the Column, we are using Y16. For strength, the bending schedule for the base shows Y12 returned as a capped basked totaling 24nos at 1500mm spaced at 125mm...the weight is tremendous when carried.

For the column, the bending schedule is 12 nos Y16 at 8inches spacing bound by a Y8 ring. The column was designed to withstand load stress and the column base to withstand downward movement.

This is the scenario we want to create: Imagine a rigid flat Tray sitting on 10 packets of match box erected vertically & loaded, supporting this tray carrying 15 cans of Coca Cola Drink.

Since the foundation is considered weak, we are supporting the building with these massive columns. The total number of columns to be put in place is 14. 6nos in front, 4nos at the back and 2nos at each side.

princechigzy:
We Quickly re-drew the architectural drawing of the house so as to produce the structural drawing and as well insert our supporting columns.

Well...this significantly defaces the building. However, better standing and defaced than "looked good but collapsed". Another basic lessons for would be landlords. Don't be shy of initial expenses to be sure you have a structurally sound building. Finishing is secondary to structural integrity.

TLAX:


Well...this significantly defaces the building. However, better standing and defaced than "looked good but collapsed". Another basic lessons for would be landlords. Don't be shy of initial expenses to be sure you have a structurally sound building. Finishing is secondary to structural integrity.

The initial redesign defaced the building but we have redesigned again, burying the supporting columns between the walls that's why the columns' dimensions are 500mm x 225mm (block size).

Am so sorry for not have posted developments on project. I have been busy at site but i will make posts tomorrow as an update on what has happened and is happening.

princechigzy:
Going Further, after an indepth analysis, we've decided to to tackle the project headlong but in stages as listed below:

First Stage: Insert massive columns with a large base. The Columns measure: 500mm x 225mm with a total length of 15ft and the column base measuring: 1500mm x 1500mm x 300mm sitting on a concrete blinding of 50mm and a Sharp Sand base of 200mm to resist movement.

Second Stage: Construct and Place 3000mm x 1200mm x 300mm massive Sub-surface retaining drain like wall 5m from the north elevation of the building. This Sub-Surface retaining drain like wall will span a total of 50m, this is to prevent the ground water moving from the top of the slope to make contact with the building foundation.

Third Stage: Tear down the existing front foundation with the ground floor super-structure only at the front and Rework the entire front foundation measuring 26.7m to the both sides measuring 2.7m each. Raise the super-structure again, Under-pin some section of the partitioning walls in the ground floor, unearth the foundation filling at some points and refill, compact and cast the DPC. Reinforce 10 existing columns in the building and finally, finish the ground floor.

Good job eng chigezie

May I know why exactly the foundation was wrong and how much did it cost to fix it all?