Soil exploration obtains information about the subsurface parameters and conditions at the proposed Soil exploration as part of site investigation. In general, it deals with determining the suitability of the site for proposed construction. This consists of determining the profile of the soil deposits at and near the site. It mainly consists of taking the soil samples and checking the engineering properties of the soil and testing it in Situ. It then gets to be used as a construction and supporting material for the foundation to carry its weight.
The function of a well laid foundation is to support the loads resting on it without exerting excessive stress on the soil masses beneath it. Stress is considered excessive if a person witnesses complete rupture of the soil mass or when results of soil exploration obtain information about the subsurface parameters and conditions as part of site investigation. In general, it deals with determining the suitability of the site for the proposed construction.
This consists of determining the profile of the soil deposits at and near the site. It mainly consists of taking the soil samples and checking the engineering properties of the soil while testing it in Situ as stated earlier.
Therefore, this becomes apparent that one of the most vital things and steps to consider in the solution of foundation problems is determining the underground conditions of the soil that would affect the design. Field and lab investigations are required to obtain the necessary information about hydrology, geology, and soil conditions.
This means verifying the Geotechnology properties of the soil before any construction can take place and the performance of various soil types encountered when acted upon by a structural weight, temperature, and water. They should consist of sub-surface investigation or better known as soil exploration
methods. Soil exploration programs get affected by a number of factors including the general look of the soil around the work area, size of the project, time available for complete exploration, and the degree of risk and safety. Tall buildings and heavy industrial structures built over fairly homogeneous clay require an extensive exploration program. An erratic soil mass has a non uniform soil strata, consistence in elevation properties, thickness, and extent. In this case of erratic structure, it becomes exceedingly difficult to determine the full picture of the subsurface as this require a lot of boring and tests. In such cases, only the location and the extent of the weaker lenses, strata, and the property of the weak soil get determined. The degree of safety and risk involved will be another factor that will govern the tough roughness and the extent of the soil survey.
To a lesser degree, a dam which would take a lot of lives and course virtually irreparable damage if it collapsed would be a tall building. The soil condition of these mammoth structures must be thoroughly investigated. It must however be warranted before the design and construction of any structure no matter how minor the construction would be. Accurate and adequate sub-surface data must be collected to enable the architects and engineers to design the foundation economically and safe at the same time. Saving of money and time will offer more than offset on the general cost of exploration as illustrated below.
There are different classes in the sub surface exploration.
a) Foundation investigation meant to investigate the sites for new structures. b) Stability and failure investigations to identify the causes of failure or distress c) Earthwork investigation to test the suitability of natural minerals for construction processes. The procedure of exploration
This procedure can be classified into the following processes.
ii) Data collection.
iii) Geologic study.
iv) Site inspection
It determines the nature of the site and estimates the types of rock and soil to be encountered. This must be done by means of geological examination and inspection of soil around the construction areas. The results of this finding are extremely valuable in planning of the sub surface exploration. The study also indicates the origin of the site such as a flooded area, buried preleases valley, former glacier deposits, or deposits made by wind. The possibilities of such defects on the bedrock can be collected from geological maps, agronomy maps, and the area photographs (Kreis 167).
2) Preliminary Exploration Includes:
i) Composition of soil strata, depth, and extent
ii) Ground water fluctuation
iii) Bedrock depth
iv) Selection of foundation
3) Detailed Exploration Includes:
i) Boring additional tests
ii) Undisturbed sampling
iii) Laboratory/ Field Tests
4) Analysis of the results on exploration should consist of:
i) Evaluation of settlement characteristic of the different soil layers.
ii) Evaluation of the bearing capacity of soil layers.
iii) Foundation design.
5) Economy Studies
This study estimates the cost of possible foundation. The site inspection includes the study of open cuts, topographic features, and existing structures. Groundwater conditions may be obtained from the surface drainage pattern or the location of springs. Another phase in this program includes investigating the types of foundations used around in the already set up foundations and buildings as well as settlement records and their depths. Inspections should also be carried out around the buildings to note the structural conditions and the presence of cracks. Before sub-surface investigations get outlined, establishment of any water or sewer lines and other utilities that may be laid across the proposed site should be conducted.
It can be of two types: Shallow exploration used for highways and railways, and deep exploration used for dams, tall building, and bridges. Exploration Methods
i) Probing /Sounding Methods
This method determines the consistency of cohesive soils or the relative density of cohesion deposits. An encased rod must be forced into the soil, and the penetration resistance observed. The resistance variation shows similar or dissimilar soil layers and the values of resistance numerically. Soil sounding has some advantages and disadvantages:
i) Sounding is much cheaper and faster to conduct than boring
2) Thin and weak soil strata may pass unnoticed in boring
3) Sounding can be used in erratic soil conditions.
4) It gives the consistency of cohesive soils and the compactness.
5) Sounding can estimate the bearing capacity.
6) Sounding also gives no ideas in settlement characteristics, and gives misleading results when soil has boulders. Dynamic penetration tests get performed in soils with low cohesion and static tests in cohesive materials. It can be done in three ways.
a) Dynamic Penetration of Rods
Older ways of sounding consisted of driving the rod down into the ground using repeated blows. Its penetration for a given number of blows of constant weight get recorded per foot and the information used as the index of the penetration experience. Skin friction acts on the rod which is cumulative with the depth.
b) Penetration by Rotation
This method consisted of a sounding rod forced into the ground by static load and rotational movement. The penetration must be recorded for static successive loads, and the penetration recorded for each turn. The method is inexpensive and fast but not suitable on coarse soils.
c) Cone Penetrometer
It is used in shallow explorations and on relatively soft deposits. The pressure slowly increases at the desired depth at which the penetration is known until there is a perceptible slow and uniform downward movement of the cone. Also, the corresponding pressure is noted down by means of the proving ring.
ii) Auger Borings
This is a soil exploration method made of cohesive or non cohesive soil above the ground water table. The soil sample obtained through this method is highly disturbed. There are different types of this equipment like hand operated or motor driven augers which can reach the depth of up to 30ft. They are the most common and can be used for greater heights.
iii) Test Pits.
This method also known as the open pit method permits direct inspection of the soil profiles in place and an undisturbed state. Test pits are satisfactory in disclosing the soil strata conditions. The cost of this pits increases with depth, and they are practically impossible when there is underground water.
iv) Deep Boring.
This method of soil exploration majorly involves in heavy structures, industrial buildings and dams. For deep borings, they use power drilling. There are two equipments used for making this boring.
a) Cable tool drilling rigs.
Cable tool drilling is the most commonly used methods of advancing a hole in the ground. It is advanced by the casing, which should be used to prevent the hole from caving in. Water must be pumped in at high pressure and exit at high speed through the holes in the bit. The water then finds its way up between the rod and the casing, carrying suspended soil particles and overflowing at the top into the joined container. From this point, the mixture returns back through the drill rod which advances by rising and dropping the bit at the lower end. The method is rapid and good for advancing holes but not recommended for extremely hard soil strata.
b)The Rotary Drill
This is a method of advancing test holes in soil experimentation. It makes use of a rotating drill bit while applying pressure to advance the hole. This may be considered as the fastest way of advancing holes in rocky areas. The drilling mud used gets forced into the sides of the hole by the rotary drill which provides enough strength to the soil to maintain the hole. The mud also seals off the water flow into the hole from the permeable water.
Seismic and electrical resistivity methods conduct preliminary exploration of highways and dam sites. This method works on sound principle which states that sound travels faster through denser materials than loose materials. 18,000 fps got recorded in dense rocks and lows of 600fps in loose soil. The electrical method involves measuring the electrical resistance of the soil. Soft and saturated soil has low resistance while dense rock has an extremely high electrical sensitivity.
a) Spacing of Borings
No known rules can be established in boring spacing. Usually, this depends on the nature and soil condition, the shape, loads, and sensitivity of the profile. However, it should be well spaced to detect the various soil profiles in sequence number, type, and to determine their extent dip and course (Sidney 14).
The boring can be classified into:
i) Primary boring: this consists of deep borings serving to disclose the stratification and the nature of the soil. ii) Main boring: they are the observation holes that check ground water table fluctuation. iii) Supplementary boring: in order to position the soil strata in clay beds, third immediate boring should be done. iv) Depth of boring: these holes should pass the required zone of the strata. The geological and topographical conditions and the foundation needed govern the depth. Reporting the results is extremely crucial. The report should be submitted in the form of a boring log and should contain:
i) The depth
ii) The elevation of soil layers
ii)The groundwater table
iv)Thickness of the layers
v) Geographical state of soil
vi) Description of the soil
vii) Position of the sample and the sample number
viii) Natural m.c, and S.T. Persistence
A boring report should contain:
i) Location plan of the project
ii) Location plan borings
iii) Description of borings
iv) Surface drainage conditions
v) Probable source of free water
vii) Drawn log
viii) Information on difficulties experienced during exploration. ix) Soil identification and classification tests results.
Disturbed soil samples include natural conditions such as texture, density, and stress conditions that have been tampered with. They can be obtained easily by using a shovel that is majorly used for compaction and classification tests
These consist of soil samples obtained with minimum disturbance of the natural state, such as texture, density, natural moisture, structure, and stress conditions.
Different types of Samples
a)Split spoon samplers
b)Walled Shelby tubes
Construction sites can be information extensive environments. In the construction industry, each project involves participants collaborating for a short time in the development of the final building. The traditional approach to construction procedures applies a laid down approach to the development of a project. Architects tend to complete their work before the structural engineers start working in order to complete their part before the actual construction phase begins. The involvement of different professionals and the traditional procurement has made clear separation between the construction organization, the design involved in the project, and the clear separation between construction phase and the design of the building process. The design provides a link between the client requirements and the actual realization of the client ideas into a constructed facility. At the design stage, the client inputs the requirements into information for actual construction.
In order to ensure the client is satisfied by the final results, the design stage must also have information about the construction operations and maintenance of that facility upon completion (Kamara1996, p.14). The integrated model and construction then represents a stage in the integration process and a good response to the client’s demands. The production environment sometimes can be far from the offices that make communication between design teams and the contractors difficult. This principal of integrated construction and design requires effective links at the task level between the design team and the working point. Waiting for design instruction has been over the years the biggest problems in terms of delays on-site.
The use of computers in construction engineering and management of the operations ranging from spreadsheets to full automation of remotely operated robots that assist the human labor, is extremely evident in modern construction. The realistic goals for construction automation however, is to make possible for the engineer to control the construction facility at any remote place in the world. This is done by use of remote tracking of materials and equipments, managing the construction site, and augmented simulation of the construction. Remote operations help the construction managers to see the progress and add the ability to plan and test construction sequence as they get executed.
This adopted technology links database and schedules in design review programs. The construction of security in modern times has also considerably improved. Loss of construction equipment from theft makes projects expensive. Contractors get hit with losses which they incorporate into their cost of doing business. In a bid to prevent this, public entity representatives who oversee the contractors include utilities directors, project coordinators, project managers, and city engineers. These representatives are responsible for ensuring that all security and loss-control measures are properly implemented during the construction period.
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