Site Investigation

Purpose of Site Investigation

To determine the site's suitability for building and the nature and the extent of preliminary work that will be needed

Why it is important ?
It will shows the detailed to many physical aspect such as subsoil composition, demolition and the legal aspect such as planning permission,right of access and preservation order

Objectives

• To assess the general suitability of the site with the proposed works
• To help produce a design which is adequate and economic
• To help overcome possible difficulties & delays that may arise during construction period due to ground and other local conditions
• To predict possible changes changes that may occur/cause of all changes in site condition 
• To maximize potential of the site

Description 

A combination process which range form looking at published information such as maps to arrange laboratory test on the soil

Information required from a site investigation:

1. Information affecting the design of the structure: shear strength and compressibility of the soil 
2. Information affecting the construction of the work: the extent and properties of material to be excavated, or to be used for fill or for road bases or concrete aggregates
3. Information on ground water conditions: the level and seasonal variation of the water table, the pressures in the soil water, and the permeability of the soil.

Planning and investigation:

•  In the earlier stages of an investigation, the information available is often inadequate to allow a detailed plan to be made.
• The investigation must therefore proceed in 3 stages:

1.  Desk study 
2. Site reconnaissance 
3. Detail Examination of tests and programs

Information /Issues to check .

1. Site location 

• Nearest town and city 
• School,Emergency services,entertainment, recreation,Shops, Transport and employment 
• Distance from head office (client & builders) & traveling time
• Distance from nearest railway station to the site

      2. Accessibility

• Approach and site access roads, width, bends, sharp corners, condition and construction relative to transport heavy plant and equipment
• Bridges, strength, width and clearance height
• Temporary road,rolled metaled tracts or consider preparing sub base for new roads temporary access

      3. Availability of space

• Site offices, canteen, stores and compound
• Material storage areas and handling 
• Construction area and assembly areas
• Plant location 

      4. Services

• Water,drainage, electricity, gas & telephone
• Location will be determined from maps by construction with the appropriate local authorities
• An estimate of building usage is also for ascertaining the demand on sewers and drains

      5. Ground composition 

          Boreholes are required to determine.

• Change in strata 
• Strength of subsoil
• Toxicity of subsoil
• Stability of excavation
• Water table (depth below surface)

      6. Site clearance and demolition 

          A plan of the site should indicate trees, shrubs and existing building and a site survey           will reveal the extent of necessary leveling Demolition and excavation 

• Method and cost 
• Effect of trees and structural prevention orders
• Reuse of materials
• Protection of adjacent building 
• Special insurance requirement 
• Compensation payment and liability for damage 
• Distance to spoil tips and charge

In General

• Dealt with local planning authority to ascertain whether there are special/significant restriction which could adversely affect the development of site building line position 
• Survey should include details of neighboring development,future development and the position with regard to facilities in the area
• Should inquire the existence of any restrictive covenants such as right of way, light & drainage which may restrict the development 

The Process

• Desk study
• Site Reconnaissance /Walk over survey
• Preliminary report or feasibility study 
• Preliminary Ground Investigation
• Main Ground Investigation 
• Laboratory testing 
• Financial Report (Return of Investment)
• Final report 

Desk Studies

• It is important to collect all available information about the site before starting work
• A desk study is the collation and review of information already available about a site, and is carried out at an early stage the remainder of the site investigation.
• Collect as much material as possible about the site such as

                               * Maps (geological, ordinance survey, etc)

                               * Air photograph

                               * Geological books & journal

                               * Mining records & reports of previous site investigation 

                               * Library, news paper, adjacent building etc.

Site reconnaissance / Walk over survey

• The initial document search should be followed by a walk-over survey of the site and its surrounding.
• This should be a methodical examination of the site, based on defined class of information, which complements the desk study and typically provides valuable information on matters such as 

                               * Topography: indication of slope instability, spoil heaps or signs of                                          ground subsidence resulting from mining.

                               * Geology: Exposures of soils and rocks which can be examined and                                                        sampled.

                               * Surface water and ground water: signs of flooding; springs; water                                        logging

                               * Vegetation: signs of vegetation die-back or restricted vegetation as a                                    result of contamination of the ground; presence of invasive species                                        such as Japanese Knotweed; trees which may caus shrinkage and                                        swelling of clay soil.

The invasive root system and strong growth can damage foundations, buildings,flood defenses, roads, paving, retaining walls and architectural sites. It can also reduce the capacity of channel in flood defenses to carry water

• Ecology: indicators of protected species newts, badgers, bats, nesting birds.
• Contamination: indication of spills disturbed ground, areas of fill or spoil heaps, old fuel or oil tanks.
• Structures: settlement of existing structures or the use of asbestos; indicators of archaeological value.
• Local Knowledge: anecdotal information on past uses of the site or past problems in the area.
• Access & Services: Information such as access for site equipment and location of buried or overhead services

Detail examination of tests and programs/ Detailed exploration

The principle objectives of the detailed soil test / investigation are as follows:

1. to determine in detail the geological structure of the site, including the thickness,sequence, and extent of the strata.
2. To determine the ground water conditions
3. To obtain disturbed and undisturbed samples for identification and laboratory testing 
4. To carry out test to determine the mechanical properties of the soil insitu

There are two principle method of investigation the ground conditions,trial pits and boreholes

Ground Investigation

      Trial Pits 

•   Trial pits are shallow excavations going down to a depth not greater 6m.
• The trial pit as suh is used extensively at the surface for block sampling and detection of service prior to borehole excavation.
• Can be dug hand or mechanical excavator 
• Only suitable in dry area as they allow hand cut sample to be taken which minimize the disturbance of sample
• Most suitable use in exploring back filled area and sites overlain by variable natural deposits 

Boreholes

• A borehole is used to determine the nature of the ground (usually below 6m depth) in a qualitative manner
• Recover undisturbed samples for quantitative examination. where this is not possible, for in-situ testing methods are used.
• Obviously the information gained from a borehole id an extremely limited picture of the subsurface structure. It is therefore essential to compare the results obtained with those that could have been expected from the desk study. The greater the number of borehole the more certain it is possible to be of the correlation and thus to trust in the result.
• The two principle types of boring machine used for site investigation which is light percussive and drilling machines.

Determine the site's suitability for good construction work.....