Task: In my capacity as a building consultant I have been asked to carry out a site investigation on two specified sites that a client is keen to develop.
Introduction: In this assignment I have been asked to carry out a site investigation as a building consultant, on two specified sites that a client is keen to develop, Therefore I am going to show how each site investigation is constructed on both areas, as one site is at the north of Peterborough (Eye Village) and the other at the south (Hampton) Both landscapes may differ however this should not affect the way each site investigation is carried out. Currently Hampton has been under redevelopment for the past 15 years, as it was previously used as a quarry to store unused rocks and bricks for the brick industry, where as the site in Eye Village is a standard brown field site that is just run down and disused.

Task 1:
A site investigation describes the process of carrying out investigations on land to determine whether there is contamination present and to collect sufficient, suitable data for the purpose of risk assessment. Moreover it is a study of a sites state of affairs to determine their probable influence of the external and internal design and structure If a site investigation was not taken place, for landscape, drainage or vegetation such as tree preservation order (TPO) reasons, the build may not physically be able to commence, Also a huge risk of health and safety issues can take place if this investigation was ignored. The investigation is normally carried out in several stages. These stages range from a desk study and simple visual inspection to a full intrusive investigation using trial pits and boreholes etc and the sampling and analysis of materials.

The first is a desk top survey this is completed by collating as much information about the site as possible whether it is the structure, ground level etc. A walk over survey is used to provide valuable information that can’t be acquired in any other way but by simply walking over the site and collecting it yourself, making sure there is no soft ground, hidden ditches etc. The main object of this survey is to check and make additions to the information already obtained during the desk top study. Trial pits or boreholes are used when doing a groundwork investigation, this is within the desk top study, and these are holes in the ground dug mechanically or by hand to give us a detailed examination of the ground such as soil type and soil conditions. Ground work investigations are divided into 6 sections

 Topography
 Soils and rocks
 Vegetation
 Surface water and Ground water
 Structural Information
 Local Information

Topography is discovering whether there are any unexpected changes in slopes or excavations at the Bottom of a ditch/slope, In addition it is the checking of any depressions or valley bottoms that may be filled causing instability, this will need to be extracted before new soil is placed, ensuring the ground is secure. Also when carrying out a Topography it is key to note if there are any signs of Landslip, such as sloping walls or tilted trees, as well as watching out for any signs of subsidence, or areas where it could occur.

When checking the soil and rocks of a site, the first thing to do is to find out what the main type of groundwork is, whilst finding gathering any evidence of peat, silt or any other highly compressible materials, and whether there are any sudden changes in these materials. It is also very important to look out for any surface cracking or stickiness which might indicate shrinkable clay is present.

Within the groundwork investigation you must check whether the Vegetation is spares, basically is it dead or alive, as well as also checking the type of vegetation that is adjoining the land. Recording the species, height and condition of the trees is essential, making sure they are healthy and stable, unable to cause any damage, also looking for signs of any tree removal is necessary if you are looking to enhance the possible building area.

To overlook the surface and ground water, you must check for any signs of flooding that may have taken place on the site, or ditches that can cause flooding as well as any natural or manmade ponds present, whilst looking for floods etc it is important to take notice of the water in case of any discolouring, if this happens finding out the source is vital as part of a health and safety check.

Before any construction can begin Structural and local information must be collected, this includes finding evidence of any damage to buildings on, or near the site, whilst looking for any signs of movement. Finding out whether there is any other evidence of buildings or service underground, whilst discovering knowledge regarding any past use of the site, searching for any local road names or area’s that help find the location of the site is important as it will enhance the finding of the site.

Foundation design

Foundation design is said to be the most vulnerable part of the build and especially the most costly to repair, I am going to start by fully defining the functions and main principles of foundation, whilst discussing what types of foundations there are. The function of a foundation is to transfer the imposed loads of a structure or dwelling on a suitable rock layer/bedrock. They spread the weight of the building, and hence the load, to an acceptable level of force exerted on the ground, in order to do this the safe loading of the edifice will have to be determined by calculating the capacity of the soil to carry the load. They must be designed so that settlement is sufficiently controlled to keep any distortion (and possibly cracking) to within acceptable limits

There are three main types of loads that need to be considered which consist of a foundation, the first is a dead load, this is the stationary or constant weight of the structure made up from the walls, floors and roofs etc, further more there are forces called live loads (also known as imposed loads) such as your tables, chairs, goods and people.

Then there is a Live load, this load may either be static or dynamic. The Magnitude and direction of a live load may change frequently due to its temporary nature; live load is calculated with less certainty than dead load. Examples of live loads include: rain load, snow load, seismic load, this is related to or caused by earthquakes or tremors. In addition human load and furniture within the edifice is another example that best describes live loads.

A wind load can be positive or negative and are not constant loads but can vary both in velocity and direction. Wind exerts three types of forces onto an Edifice/dwelling; the first is an uplift force this is Wind flow pressures that creates a strong lifting effect, much like the effect on airplane wings. The Wind flow under a roof pushes upward; wind flow over a roof pulls upward.
The next is a shear load; this is a horizontal wind pressure that causes racking of walls, causing the building to tilt. The third force is similar to that of a wind load, however this is horizontal pushing and pulling pressure on walls that could make a house slide of the foundation or overturn.

Substrata bearing capacity

When starting a foundation you must make sure that there is an acceptable substrata bearing capacity generally it is called a SBC (safe bearing capacity). It indicates how much load the substrata can bear without settlement the unit for this are metric tonnes per square meter T/sqm. For any structure to be stable the force bearing down must be opposed to an equal force acting upwards. When both forces are equal, better known as having the same magnitude, they are said to be in equilibrium to each other. When a structures downward and upward forces do not contain the same magnitude i.e. the force acting down is greater than the upward force, then the Building will be in danger of sinking or subsidence.

Impact on foundation design:

The whole process of a foundation design is very complex; therefore there are many following factors that will need to be considered in order to select the correct and appropriate foundation. You must understand the full loading of a build before a foundation is placed; this includes the imposed load from the building, which consists of the dead load of the structure and any excess live loads, exerted from Furniture within the building and wind pressures acting on the building. Moreover if any water is found inside the excavations, due to high water table, the usual choice is to remove it as a temporary solution or to install land drains and remove the water on a permanent basis, It is also very important to make sure none of the water in the ground or soil is contaminated, this can cause heavy erosion over a long period of time, this is due to the water and nitrates within the ground to combine and produce an acid that is very effective on the concrete resulting in it eroding. An alternative to this is sulphate-resistant concrete specified for these purposes, however time and care is required both in its handling and placement ensuring it reaches its compressive strength in an appropriate time.

Key: the selection of a foundation always depends on the type of building structure, soil conditions, External or internal constraints also the types of foundations available due to cost budget.

Introduction to foundation types:

In the paragraphs below I will provide a brief but descriptive introduction to the three main types of foundation used mainly in the UK but World wild also. The strip foundation is by far the most common and, in most cases, the cheapest. It has been used, in one form or another, for hundreds of years and, for low rise housing, is suitable for the majority of ground conditions likely to be found. The other two foundation types are more likely to be used where sites and ground conditions are more complex.

Forms of low-rise construction:

A low rise building is defined as any occupiable building; it must be placed on solid ground and fabricated along its full height through deliberate process as opposed to naturally-occurring formations having at least one floor above ground. An individual building in this category is generally defined as those with connected interior spaces, any low-rise building with more than one disconnected interior spaces may only count as a single building if it was built as a single unit.

There are two types of low-rise construction the first is a low-rise residential building, these include the smallest of edifices produced in large quantities, single-family detached houses, for example, are in the walk-up range of one to three stories and typically meet there users needs from 90 up to 180 square meters of enclosed floor space. Other examples include the urban row house and walk-up apartment buildings, typically these forms have relatively low unit costs because of the limited purchasing power of their owners.

The size of buildings in the commercial, institutional, and industrial market segment ranges from a few hundred to as much as 45,000 square metres. All of these buildings have public access and exit requirements, although their populations may differ considerably in density. The unit costs are generally higher than those for dwellings and this type includes buildings with the highest unit cost, such as hospitals and laboratories and schools etc. Residential buildings are fairly static in their function, changing only at long intervals.

Strip foundation:

The strip foundation is basically a strip, or ribbon, of insitu concrete running under the entire load bearing walls. This will normally include all the external walls and possibly some, or all, of the internal walls this will generally allow line loads from the walls to be distributed to the earth below. The depth and width of the strip depends on the building load and the nature of the ground. They are mainly used on low-rise buildings such as most common houses or domestic dwellings up to four stories high. In many cases these foundations do not need specialist design; the foundation size can be determined by referring to the Building Regulations.

A typical house from the 1900s or so would have a thin strip of concrete under all the load bearing walls. Prior to this, walls were often built directly onto the levelled ground; sometimes there might be a bed of stone or ashes to provide an even surface. Nowadays, the design of foundations is controlled by national Building Regulations. Strip foundations can either be 'traditional' or trench-fill they usually 500 to 700mm wide and as deep as necessary for the type of ground. In clays for example they are usually at least 1 metre deep to avoid problems of ground movement caused by seasonable change in moisture content. In very dry conditions, for example, clays will shrink slightly as the clay loses water. In very wet conditions the clay will swell. In weaker ground the foundation has to be wider than 700mm to spread the building load over an adequate area of ground. (Diagrams on next page)

Pile Foundation:

Piled foundations can be of various types. They can be used to transmit the loads from the foundations through weak, compressible, or unstable strata, to firmer ground beneath (end bearing piles). In clay and other cohesive soils, piles can be used to distribute the loads into the ground through the friction forces along the length of the pile sides. Piles are usually made from insitu or precast concrete but can also be steel and timber. In housing built from load bearing brickwork, a reinforced concrete beam bridges the piles and directly supports the building.

There are a number of different piling systems. Some such as replacement piles bore out the ground and then replace the void with concrete. A reinforcement cage is lowered into the wet concrete to resist any lateral forces in the ground which might fracture the pile, and to provide a connection for the ground beam which will support the walls. Others like displacement piles are forced into the ground, pushing it out of the way as the piles are driven home.

Raft Foundation:

Rafts are an expensive form of construction, probably the most expensive of the three, and are used where only a very low load can be applied, for example, on soft or variable ground. They are also used where differential settlement is likely or where there is a risk of subsidence (they are common in mining areas). The raft is a rigid slab of concrete, reinforced with steel, which spreads the building load over the whole ground floor area.

In the 1940s and 1950s raft foundations were quite common, particularly beneath the thousands of
Prefabricated pre-cast concrete or steel buildings erected during the years following the Second World War. Most of these houses were built on good quality farm land where the soil was generally of modest to high bearing capacity. Rafts (or foundation slabs as they were sometimes called) were often used because they were relatively cheap, easy to construct and did not require extensive excavation (trenches were often dug by hand).

In 1965 national Building Regulations were introduced for the first time, but these did not contain any 'deemed to satisfy' provisions for raft foundations (as they did for strip foundations) - consequently each had to be engineer designed. As a result they quickly fell out of favour. In modern construction rafts tend to be used where the soil has low load bearing capacity and varying compressibility. This might include, loose sand, soft clays, fill, and alluvial soils (soils comprising particles suspended in water and deposited over a flood plain or river bed). In addition they are also used where pad or strip foundations would cover more than 50% of the ground area below the building and where differential movements are expected.

Site Two: Eye Village
Before any construction Can begin there are stages needed to be completed to ensure that the build is constructed successfully and is sustainable for its due amount of time, this specific site chosen east of Eye village is Known as a Green field site, this is a site that has not been constructed on before, However this does not effect how I carry out the site investigation, I should continue thoroughly, making sure all land area, slopes, in filled areas, and environmental issues of the site are seen and handled with properly
Topography of Eye village:
When I evaluated the topography it concluded that again there were very little contour lines in this particular site, only this time the contour lines where spread around 40m apart from each other, with a height distance of 8 meters, in this case closer together than the Hampton site, making the plot of land at a greater slope, still I could see that there is very little altitude in the ground, which again indicates a fairly flat lay of land, this is a good start to the build as it shows that the building can be constructed with ease.

Site investigation:

On the Eye village site I again used An OS map when collecting information about the area, this allowed me to pin point the site, and obtain accurate grid references of its location, this allowed much more accurate references on the geological maps. When looking into the history of the site I discovered that the village was rather historic, however this particular area has not been used for over 300 years, and has kept in good condition during that period of time, the vegetation of the site has reduced however the land itself can come of good use.

To your advantage, there were no sign of landslides around the area and the rocks and soil found on site was of good condition, the soil was of very highly compressible material. Although the lad was fairly flat, when looking over the ground works of the site I happened to come across a rather large ditch towards the back of the area, which became a problem as this could likely cause flooding in the near future, fortunately there seemed to be no evidence of discolouring in the water that lay to the centre of the ditch, which indicates the water is not contaminated
Ground investigation:
A direct ground investigation is the third stage in the site investigation; as far as low rise housing is concerned its main objective is to determine whether a strip foundation will be suitable for this design. As the groundwork of this site is made up of highly compressible soil material it is likely that any other foundation type is needed, therefore there is no need to restore/replace any of the soil. I would advise you to use Bore holes to inspect the soil further.
Foundation Type for Eye Village:
For this site this site the most reasonable Foundation method, proven method, that most builders are familiar with is the tradition Strip foundation, the reason behind this is that the building due for construction again is not too high in density, and will consist of less than four stories high also the groundwork is rather stable, consisting of good compatible soil, which will happily hold the foundation type without any subsidence, A strip foundation is very cost effective, and one of the cheapest, Also if mistakes occur (e.g. setting out) this type of foundation is not too expensive to rectify once concrete is poured. This build and the laying of foundation should go smoothly as The area is reasonable and quite clean.

Eye Village report table:

Feature: Location: Comment:
Structures On site

Adjacent This land is a clean green field site that consists of no present or previous Structures,
Towards the back of the site, North, there is an newly built estate that runs away from the site.
Slope angles On site

Adjacent
There are no current slopes in the ground , however there is a rather vast ditch around 1m in depth that is currently collecting rain water.
There is a slight hill as you exit the entrance/drive of the location that slopes towards the leading road, although it is found to be quite safe.
Made ground Hard standing
On site The sites area is around 90ft by 30ft and is made up 100% of old but good ground soil and grass vegetation.