Barselonia:

The argument here is not which is d best
But situation u cast a ground beam on Sand with digging is possible..

I understand perfectly sir.
This is just an inference. I've worked on a Sandy ground without no excavation. The only thing we implemented was raft starting from NGL, the raft was left to settle under it's own weight.

Barselonia:
Well it depends on type of foundation you are using
If u are doing a raft foundation ,u don't need to dig down ,just make ur form work, reinforced it ,you are good to go, since d surrounding Is still going to be fill with sharp sand.

But in situations of hollow block.. ..dont try it

God bless u
I thought i was the only one, because the picture attached to the writeup is raft foundation.
I really do not see anything wrong if it is raft foundation. & only an insane person will start setting block without excavation.

swazpedro:
lol Engr. indeed the land is filled and is almost like digging down.. this buildings are structurally fit. the funny thing with Nigerians is anything other than the norm is bad... with out proper research u conclude.. this houses are not built with stripped concrete it continuous beams foundation but are most times chained with rafts for even settlements and this buildings are not high rises with much dead load but just duplexes.. so as an engr op, u should do d maths well and know if it is possible not saying because of what u believe dat is wrong some Nigerian structural engineer have analyzed this and deemed it fit and economically suitable.. its usually used in water logged areas like lekki ajah phases.. please don't spread wrong messages that breed fear

I will have to agree with you here sir.
In Nigeria, anything different from the norm is deemed not suitable. you don't have to necessarily dig down place your foundation and depth of excavation depend on the position where you have a safe bearing capacity that will carry the building.

Raft foundation can be built on a sand filled site provided adequate measures have been taking to dewater, removal of vegetable top soil and very week soil strata at the top and adequate compaction (either through mechanical means using a roller in layers or by allowing the soil to consolidate under its own weight over a number of months or years.

COOLDK:


Even on a land that seems stable and hard enough. You can't conclude until u carry out soil investigation. What is lying 500mm to 1000mm below NGL might surprise you during excavation.
Perhaps, short piles of about 4-5m have been introduced where considered fit economically

U can't just sit down concluded u want to use a pile of 4-5 m for residential building of 2 to 4 floor.. .
It depends on d load that's coming on d foundation that means u use pile.
Bridges Self dey use pile of 5m ,now talking of our common House.. .wetin he wan carry. ..pile of 1.2 m is okay if necessary

abdulwastecx:


I will have to agree with you here sir.
In Nigeria, anything different from the norm is deemed not suitable. you don't have to necessarily dig down place your foundation and depth of excavation depend on the position where you have a safe bearing capacity that will carry the building.

Raft foundation can be built on a sand filled site provided adequate measures have been taking to dewater, removal of vegetable top soil and very week soil strata at the top and adequate compaction (either through mechanical means using a roller in layers or by allowing the soil to consolidate under its own weight over a number of months or years.

Gracia

this is as a result of the undermining of geotechnical and envigineering geophysics disciplines. The only solution is to enact laws which mandates a simple foundation or soil test on every site earmarked for construction throughout the country then you will begin to see miracles.

abdulwastecx:


I will have to agree with you here sir.
In Nigeria, anything different from the norm is deemed not suitable. you don't have to necessarily dig down place your foundation and depth of excavation depend on the position where you have a safe bearing capacity that will carry the building.

Raft foundation can be built on a sand filled site provided adequate measures have been taking to dewater, removal of vegetable top soil and very week soil strata at the top and adequate compaction (either through mechanical means using a roller in layers or by allowing the soil to consolidate under its own weight over a number of months or years.

thank u

swazpedro:


soil test... have u ever built before? did u study construction economics.. there are codes and assumptions made wen building.. foundation foundation foundation... I don't work with structural engineers dat don't visit the site... and the op is saying this method is bad, not knowing that this method with a surrounding retaining wall as d fence with a depth of 1m can stand as any other building, Nigeria is where it is because u don't know what u read and u don't experiment and test different construction methodology other than what ur lecturers of 1980 taught u.. every building, site is unique and need different method of construction. this design is not bad soil test or not. its is a method of construction.. I am not talking of the soil

every building, site is unique and need different method of construction, i agree but "this design is not bad soil test or not" i don't understand.

emi14:
Oga try biuld on sand and see .

it is build not biuld. just passing by

toxxnoni:


every building, site is unique and need different method of construction, i agree but "this design is not bad soil test or not" i don't understand.

method sorry

swazpedro:


soil test... have u ever built before? did u study construction economics.. there are codes and assumptions made wen building.. foundation foundation foundation... I don't work with structural engineers dat don't visit the site... and the op is saying this method is bad, not knowing that this method with a surrounding retaining wall as d fence with a depth of 1m can stand as any other building, Nigeria is where it is because u don't know what u read and u don't experiment and test different construction methodology other than what ur lecturers of 1980 taught u.. every building, site is unique and need different method of construction. this design is not bad soil test or not. its is a method of construction.. I am not talking of the soil

I'm a COREN Registered Civil Engineer to cap it all.

I'm not saying you've gat no point but it's very appalling seeing buildings collapse here n there.

We the professionals need to rise to the occasion of kicking out quacks from the system.

In Abuja, before any major concrete work is done, the Development control agency will visit the site and give an approval in written form but this is not the case in other part of the country.

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

There's absolutely nothing wrong with building on sand or made ground!!! If you are referring to the picture as a reinforced concrete strip foundation, you are most definitely wrong and ill-informed. The picture shows a raft (ground beam and slab system) foundation on well blinded and stabilised level. Sand is a very friendly material, which consolidates almost immediately, and does not settle or heave. On the contrary, clay, silty clay, peat and others are very poor materials that are often removed and replaced with sand.
In designing foundations (solid slab raft, beam and slab raft, cellular and buoyancy raft etc) on made ground, the governing parameters are settlement, differential settlement, bearing pressure, punching shear etc. These are most of the time not considered by engineers, due to lack of proper understanding of soil-foundation-superstructure interaction. Settlement is never a problem, the real and most dangerous challenge is excessive and differential settlement! These can undermine the structural integrity of a building or structure, and consequently result to failure.
Due to the level of corruption in Nigeria, developers, building professionals, quacks and government officials etc, in fact, all hands are seriously on deck, encouraging sharp practices in the industry and the country at large. Collapse of buildings will continue to occur until such a time where it is passed and a criminal offence with capital punishment. Certain people in certain quarters ought to be jailed or summarily executed.

sabama007:


I'm a COREN Registered Civil Engineer to cap it all.

I'm not saying you've gat no point but it's very appalling seeing buildings collapse here n there.

We the professionals need to rise to the occasion of kicking out quacks from the system.

In Abuja, before any major concrete work is done, the Development control agency will visit the site and give an approval in written form but this is not the case in other part of the country.

it's very appalling seeing buildings collapse here n there.

We the professionals need to rise to the occasion of kicking out quacks from the system.

In Abuja, before any major concrete work is done, the Development control agency will visit the site and give an approval in written form but this is not the case in other part of the country

I stand with you on this.

Barselonia:
Well it depends on type of foundation you are using
If u are doing a raft foundation ,u don't need to dig down ,just make ur form work, reinforced it ,you are good to go, since d surrounding Is still going to be fill with sharp sand.

But in situations of hollow block.. ..dont try it

What do you mean by... 'you don't need to dig down'?

shine12:


I enjoyed reading your post. CFA piling is a potential solution to overcoming a weak soil with poor subgrade reaction and bearing pressure. The problem with construction in Nigeria is there are no strong Building Controls,Health and Safety Executive and Construction regulations that punishes poor construction. People are more concerned with getting the building up irrespective of the ground conditions and the construction methodology adopted.

Piling is NOT the last resort to overcoming a weak subgrade.

frank043:


Piling is NOT the last resort to overcoming a weak subgrade.

I said potential solution and not last resort.If you see my other comments you will see I said reinforced raft founded on a more stable soil layer.

frank043:


What do you mean by... 'you don't need to dig down'?

Excavation. ....
Layman word...
Don't want to go engineering

Barselonia:

Excavation. ....
Layman word...
Don't want to go engineering

Really... You sounded more like a layman to me.

frank043:


Really... You sounded more like a layman to me.

But u still understand the message am passing

Barselonia:

But u still understand the message am passing

Fair enough... But depth of excavation is a function of geotechnical report, which informs the engineer on the profiles of various soil bearing capacities with depth. One doesn't just choose to excavate or not. By the way, are you a structural or geo-structural engineer?

frank043:


Fair enough... But depth of excavation is a function of geotechnical report, which informs the engineer on the profiles of various soil bearing capacities with depth. One doesn't just choose to excavate or not. By the way, are you a structural or geo-structural engineer?

Structural engineer and you

@OP I will like to call your attention and other readers to the blog site where you shared this info from. The blog owner is nothing but a liar who sat at he corner of his room and fabricated this write up that has no engineering basis, he claimed he went round to observed the trend of building process and people are building directly on sand (is that actually wrong? i will talk about that later) i expected him to have a loads of pictures to back his investigation up but nope! Alas only a pictures he stole from my thread (https://www.nairaland.com/1584575/construction-2-storey-building-osapa-lekki) this pictures was a picture of a foundation i did about five years ago. I am a trained civil/structural Engineer and i did this project under a well grounded civil engineer with abt 30 years of experience and 25 yrs of registration with COREN this same engineer is the structural consultant for Property Mart (property Mart is the owner Greenadines Estate, chevy view etc and to those who know property mart well you will agree with me that they have partnership with foreign investors who brings in their expatriate in during construction process). This very site was in Osapa London on a sandfilled land left for several years for natural compaction and a test was carried out prior to construction and the test result gave adequate soil bearing capacity almost at the top level, mind you the site level was lower to the road level, so why do we need to go down and spent so huge amount in bringing the foundation out higher to be higher than the road. Please check out the completed carcass of the build and some finishing on this thread https://www.nairaland.com/2265534/construction-duplex-attached-flats-osapa/2

frank043:



There's absolutely nothing wrong with building on sand or made ground!!! If you are referring to the picture as a reinforced concrete strip foundation, you are most definitely wrong and ill-informed. The picture shows a raft (ground beam and slab system) foundation on well blinded and stabilised level. Sand is a very friendly material, which consolidates almost immediately, and does not settle or heave. On the contrary, clay, silty clay, peat and others are very poor materials that are often removed and replaced with sand.
In designing foundations (solid slab raft, beam and slab raft, cellular and buoyancy raft etc) on made ground, the governing parameters are settlement, differential settlement, bearing pressure, punching shear etc. These are most of the time not considered by engineers, due to lack of proper understanding of soil-foundation-superstructure interaction. Settlement is never a problem, the real and most dangerous challenge is excessive and differential settlement! These can undermine the structural integrity of a building or structure, and consequently result to failure.
Due to the level of corruption in Nigeria, developers, building professionals, quacks and government officials etc, in fact, all hands are seriously on deck, encouraging sharp practices in the industry and the country at large. Collapse of buildings will continue to occur until such a time where it is passed and a criminal offence with capital punishment. Certain people in certain quarters ought to be jailed or summarily executed.

God bless people like this who has a good and deep knowledge of their profession. Thumbs up.

Horlawoomey:
If from your soil investigation, raft foundation is recommended for your building (mostly when it's not more than a storey building) and if the soil type is a sandy soil like that of Lekki axis, you can go ahead to construct your foundation beams after proper remover of vegetative cover, sand filling with sharp sandand proper compaction.

But in a situation where we have loamy or clayey soil, it is recommended to dig to a point where the soil is compact enough as required by the structural engineer before the foundation work, either raft or strip foundation.

What I know quite well is that settlement is very minimal in a well compacted sandy soil especially when raft foundation is adopted.

Oga abdulwastecx and
Aventures can shed more light on this

i have shed the light oo (LOL) the picture was even stolen from my thread, please can i sue for copy right? Just joking.

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

Barselonia:

Structural engineer and you

I'm a Civil, Structural and Geo-structural Engineer... I'm working towards being an expert in these areas.

Barselonia:
Well it depends on type of foundation you are using
If u are doing a raft foundation ,u don't need to dig down ,just make ur form work, reinforced it ,you are good to go, since d surrounding Is still going to be fill with sharp sand.

But in situations of hollow block.. ..dont try it

Excavation of the foundation trench cannot be over emphasized, no matter the method you adopt. Sometimes the clients too will tell the contractor to try and manage. I remember a renovation job I got 2011 when I've not had much years of working experience. It was a massive structure with swimming pool on a watter logged plots of land. After some years, there was a differential settlement even the walls of the pool collapsed due to the passive earth pressure, I was able to make a good retaining wall for the pool and hired a more experienced structural engineer to underpin the existing structure, yet the client was complaining about my bills but I treathened to quit before he later sucumbed. From my experience, I've seen that Clients also contribute to some of the structural failures.
Long live Naija
Long live COREN.

Aventures:
God bless people like this who has a good and deep knowledge of their profession. Thumbs up.

Thanks for the words and thumbs up Bro... I'm just a simple Nigerian, saddened by the decayed state of the nation.

frank043:


I'm a Civil, Structural and Geo-structural Engineer... I'm working towards being an expert in these areas.

Nice one..

Topman0001:

Excavation of the foundation trench cannot be over emphasized, no matter the method you adopt. Sometimes the clients too will tell the contractor to try and manage. I remember a renovation job I got 2011 when I've not had much years of working experience. It was a massive structure with swimming pool on a watter logged plots of land. After some years, there was a differential settlement even the walls of the pool collapsed due to the passive earth pressure, I was able to make a good retaining wall for the pool and hired a more experienced structural engineer to underpin the existing structure, yet the client was complaining about my bills but I treathened to quit before he later sucumbed. From my experience, I've seen that Clients also contribute to some of the structural failures.
Long live Naija
Long live COREN.

U speak it all