Great information.

Barselonia:

Nice one..

Thanks. Are you a practicing structural engineer?

frank043:


Thanks. Are you a practicing structural engineer?

Practice as a site engineer not as a structural engineer ......... .
And am on my own.. .no company recruiting.. .
Search search tired.. ..

Barselonia:

Practice as a site engineer not as a structural engineer ......... .
And am on my own.. .no company recruiting.. .
Search search tired.. ..

That's good... You are doing something, and growing professionally.

Aventures:
Here is another thread of a job done on sandy soil. The Geo-technical investigation informed us that the upper part of the soil is loosed and the bearing capacity is low, we were also informed that the bearing capacity that can withstand the pressure of the proposed build is at 900mm down and so we took the excavation down their. Geotecnical-investigation is very key in foundation design. https://www.nairaland.com/2522848/construction-medium-high-rise-multi/2

In a place where filling was done on the top soil, Engineer Aventure can the structure go on it...?

Chekitaut:
In a place where filling was done on the top soil, Engineer Aventure can the structure go on it...?

Filling in a top soil can cause a differential settlement, it is better to first evacuate the top soil and vegetations, also to ensure that there is no peat lying beneath. when there is no top soil, vegetation and peat, you are good to go ahead with the filling and after proper compaction and consolidation a geotechnical test is highly advisable before commencing your foundation design and construction.

What if you are building on a reclaimed land (like a swamp) that was sand filled? Are you telling me you will excavate foundation trenches? Secondly, what if the land has been sand filled and its way way lower than than your reference ground level, will you also excavate?
How many people can afford a pre-survey/ soil test on a privately owned property? My take on this as an experienced professional is make sure your filling is properly compacted and preferably been filled with sharp sand, get a perfect structural work on your building to accomodate the soil defects in case of differential settlement by introducing columns and ground beams of high yield value as it pertains the type of super structure (eg. 20mm rebar @ spacing of 150mm for a storey building for the ground beam and columns) , use rich concrete preferably grade 25 with adequate concrete cover, have a minimum of 100mm blinding cover, proper soil stabilization and proper backfilling of the substructure..
All the same, this in a way is bye-cutting the professional standard...normally a soil test ought to be carried out which will determine the retensive strength/capacity of the soil thereby advising you on the type of foundation that befits the soil type..

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jeftalene:
Engr. Osaz' Enobakhare (Lagos, Nigeria)

As construction cost rises due to attendant rise in prices of building materials, the trend of building houses directly on sand has been observed to be on the increase especially by unscrupulous developers and contractors. Having carried out an independent monitoring of construction activities in some areas in the Ajah axis of Lagos lately, it became obvious that in order to save cost people have resorted to constructing buildings directly on sand.

The awkward idea been adopted in most of the cases under study is to sand-fill the land, level and compact it with the use of machines and the construct a reinforced concrete strip foundation directly over it without recourse to minimum construction/engineering standards. They do so very quickly so that before any of the regulatory bodies saddled with the responsibility of building control gets wind of their ill act, they are already on super-structure level at which point it is burdensome to ascertain how the foundation was actually built.

On a particular site, using this vague method the entire foundation including the ground floor slab was put up in one week and by the next week, they were already building up the walls and frame. Dishonest developers thrive in such indecent acts and sell or lease these buildings to unsuspecting prospective buyers who in-turn occupy them or cause others to do so by way of lease/rent too. There is no consideration for lives and properties put at risk of an imminent collapse even as some of the buildings observed are already exhibiting symptoms of instability and sick building syndrome pre-occupancy.

Five years post-occupancy, the building over-settles (or sink) and then tilt in a particular direction. When asked, some of these developers claim that before there will be any major issue with the building they would have recouped the returns on their investment and its left to the new owner to do a repair by way of underpinning as the need arises. To know that some greedy professionals have joined the bandwagon of quacks in delivering such poor structures is condemnable. This act should not be encouraged in any form.

Here are some structural considerations; normally after leveling and compacting operation has been carried out on a sand-filled land it still remains a made-up ground. Although the land becomes stiff at sub-surface levels, this doesn’t in anyway erase the fact that the underlying bad soil (or peat) remains intact and retains its poor attributes. Peats are highly compressible soils and will naturally compress upon the impact of load. As this happen, the building will settle indifferentially, especially during seasonal changes and mass movement of the earth; which occurs at various times of the year. Such structural anomaly often leads to poor stability of the building and eventually a collapse if unable to bear the load, especially for single or multi-storied structures.

Rising cost of building materials should not be a yardstick to adopt poor construction methods in the construction of buildings and estate infrastructure anywhere. The authorities should not turn a blind eye to such activities that jeopardizes or threatens the lives of people as well as the overall health of the built environment. Project owners and developers should not connive with contractors or builders to manipulate well established engineering prinicples. It is important to select a good contractor for your projects. Yes, there is room for adopting cost-saving methodologies like the use of dry construction methods, cold brick construction, etc but bad construction methods is never the way to go.


Source: http://engineerosaz..com/2017/03/why-it-is-structurally-wrong-to-build.html

Lovely writeup

Hmmm