Constructing a motorway (civil engineering project) - Essay Example

? CONSTRUCTING A MOTORWAY (CIVIL ENGINEERING PROJECT) Introduction A motorway can be defined roughly as a main road or highway, with two or more lanes on opposite direction, and where fast motor traffic occurs. A motorway has to be well constructed with all the required plans, materials and skilful engineering needed to provide a long-lasting use for motorists. As the Junior Site Manager of a 30-mile motorway, my job is to provide the plan and the necessary activities to have a smooth flow of construction, maintenance and completing of this motorway. But before going on an analysis of the construction parameters, I deemed it necessary or compulsory on my part to study history and the great accomplishments of the engineers and architects who made the British Motorway System, on how it was visualised, planned, and made to action to provide the future generation with a quality highway for the vast land transportation that we have today. First, the planners used geographic and topographic maps. Although technology and computers were not yet very effective at that time, the information the planners had was enough to make them achieve their great objective. Present planners and engineers have all the information from computers and databases before they embark on such a gargantuan task. The vision that the planners had is mastery itself, considering that in the nineteenth century, motor vehicles were just beginning to be invented. Engineers and builders of motorways are faced with multiple and complicated tasks. In the initial steps, they are concerned particularly of the volumes of earth to be moved during embankments and cuttings. There is also the concern of the cost of moving those volumes of earth. Present engineers try to balance these two activities – the cut and fill. The aim is to avoid borrow or spoil, which adds costs to construction. Formation of cutting and embankments Cuts and embankments are needed in constructing a motorway or an elevated highway. In doing this, there are excavations and earthworks involved. Earth movement will involve a lot of activities in road construction. The first job of a builder of a motorway is to balance the cut and fill by calculating quantities to be moved. Calculating the volumes to be moved will involve measuring the horizontal and vertical sections using a planimeter, and in order to be accurate about this step, it has to be done at least three times. (Gallagher, 2004, p. 415) The principle in calculation is analogous to measuring the volume of a ship, which is measuring the displacement and tonnage. To do this means to measure the area of vertical cross section in successive lateral points. This technique of measurement was first introduced by Matthew Baker when he applied it in a cross section of a ship in 1586. The series of measurements were then compiled by George Parker Bidder in a paper titled “Table of Cutting and Embankments” on the construction of the London and Birmingham Railway in 1836. (Gallagher, 2004, p. 415) An important factor to be considered in earth work or excavation is to determine the material a junior site engineer like me will be working with. I will have a lot of site investigation and analysis of the materials. A lot of information from our databases regarding the site, the materials and equipment that we will be using, will help a lot in the success of the motorway project. A common way of classifying the soil to determine its ease of excavation is known as the Ease of Digging scale. This is common in the United Kingdom. According to this theory, the soil is classified into four categories: E – for Easy digging, e.g. sands, fine gravels, etc. M – for Medium, example is cohesive soil like clay, gravel, etc. M-H – for Medium to Hard – refers to rock broken to pieces, heavy clay, gravel with boulders, etc. H – Hard refers to hard materials that require blasting. (Durham. Ac.uk.) Foundations Foundation engineering involves an analysis of the soil mechanics and judgment on the part of the engineer on the complex blend of the soil composition and the environment. Foundations can be considered shallow and deep depending on the depth where the load is transmitted to the soil. Shallow Foundation Examples of shallow foundations are continuous wall footing, spread footing, raft or mat foundation, etc. The compositions of shallow and deep foundations are illustrated in the figure below. Deep Foundation Deep and shallow foundations are almost similar when it comes to building to support a structure but there is a slight difference in that in deep foundations the transfer of load is transferred to the soil vertically. (Kameswara Rao, 2011, p. 4) The following are guidelines for foundation design and construction as recommended by Kameswara Rao (2011, p. 4): 1. The depth of footings should be adequate below ground level to avoid heaving of the adjacent soil. 2. The footing depth should also be below the zone of seasons changes to avoid freezing, thawing, ground water, etc. 3. Precautions should be undertaken in adapting expansive soil because this will cause upward pressure. 4. Protection against corrosion should be part of the design. 5. Flexibility should also be undertaken that should give way for future modifications. (Kameswara Rao, 2011, p. 4) Figure1 Diagram of shallow and deep foundations SOURCE: Adapted from: Foundation design: theory and practice, by Kameswara Rao, N. (2011, p. 10) Slope stabilization using bolts, nails and anchors The world dilemma on climate change and global warming has put cities and towns in many densely populated areas of the world, particularly in tropical countries, in great danger during heavy rainfall. These places should have adequate slope risk reduction to minimize the risk of landslides and floods during major weather disturbances. Also, in road construction, slope stabilization must be effectively done to minimize landslides, particularly if the place is subject to heavy rainfall. Stabilisation work on rocks and residual soils should be introduced and adapted. In so doing, planners and engineers have to act fast and conduct engineering activities and measures such as slope stabilization using bolts, nails and anchors. Figure 2 Example of un-stabilized slopes. SOURCE: Handbook of slope stabilisation, by Ortigao, J. and Sayao, A. (2004, p. 2) Geological features have a strong effect on road construct ion. These geological features can be observed during on-the-spot surveys or inspections and also in topographic maps and aerial photographs. An engineer can acquire an accurate knowledge of the area by comparing geologic and topographic maps and more studies and analysis on site. Most engineers take their attention on the drainage and surface protection in applying stabilisation method. Applications include efficient and durable drainage structures and easy-to-maintain drainage systems. But stronger structures are applied with anchors, bolts and nails which are inserted into the ground to counter tension forces. There are two factors that influence slope stability and these are: slope gradient and groundwater. It is said that when there is great slope gradient and more groundwater present, the slope will definitely be less stable regardless of the soil type and material present. Therefore, engineers should first take into consideration the slope gradient and the groundwater in constructing and maintaining motorways. (Tomlinson and Woodward, 2008, p. 12) Anchors Anchors are installed to resist tension forces and therefore they have to be durable and made of quality materials; manufacturing should follow standards according to specifications from different countries. (Ortigao and Brito, 2004, p. 311) Anchors have elements which are the: Head – this is the part of the anchor which protrudes outside the ground; Bonded length – the length of the anchor that exerts strength to control the tension; Free length – this is known as the frictionless length, situated between the head and the bonded length, which carries tension load from what is considered the bonded length to the head. (Ortigao and Brito, 2004, p. 311) Anchors have their own characteristics and the recommended characteristics are those that provide the required strength and can be installed permanently. Anchors, bolts and nails, as mentioned, should be made of quality materials. Usually, they are made of concrete reinforcement steel bars or special steel bars. Various countries that have experienced extreme weather condition apply durable and quality special steel bars in their construction. Piling Works Piles are columns in a foundation which function as support load from a superstructure through weak elements by way of water onto a stronger soil composition or rock. Piles are used to carry uplift loads in supporting tall structures which are constructed under pressure by natural forces such as winds or waves. Sometimes piles are used to carry horizontal and vertical loads in supporting retaining walls, bridge piers and abutments. (Tomlinson and Woodward, 2008, p. 1) Using piles to support structures is one of the earliest methods used by engineers in the early periods of civil engineering. The Romans were the pioneers of timber piling which they used in Britain to support bridge works and riverside settlements. In medieval times, timber piling was popular and much in use, especially in the constructions of great monasteries. In China, bridge builders made use of it during the time of the Han Dynasty (200 BC to AD 200). Timber piling was popular and in use during those times, but the application and resistance was limited. (Tomlinson and Woodward, 2008, p. 1) Types of pile A. Displacement Pile A displacement pile for a marine structure will utilize a solid precast or prestressed concrete pile for construction in shallow water. In deep water, the engineer should use a steel tubular pile or tubular precast pile. Timber piles can be used in shallow water but for exposed marine conditions, steel tubular piles are recommended. For a structure on land, there are a few choices. One is the bored and cast-in-place pile (or augered pile) which is the cheapest type used where lined or unlined holes are drilled. This type can withstand high working loads. Augered piles are designed in places where heave, noise and vibration put pressure on the structure. This type is also economical for light and moderate loads. (Tomlinson and Woodward, 2008, p. 12) Another type is the timber pile, also designed for light and moderate loads and used in countries where timber use is tolerated. Timber pile is believed ideal because it has strength to weight ratio, can easily be cut, handled and trimmed according to specifications. Timber of durable species lasts for a very long time. (Tomlinson and Woodward, 2008, p. 14) Quite expensive are the precast concrete-driven piles. There are also piles used for foundations that withstand seismic situations and these are regulated under the Eurocode 8 ENV 1998-5: 1994. B. Pre-cast Concrete Piles These types of piles are basically useful in marine and river structures; these are situations wherein cast-in piles are impractical to use. Trenching and Deep Excavations Deep excavations should be planned and executed with some long-term gains in mind but also taking into consideration safety and avoidance of damage. The engineer should make adequate steps not to allow collapse during the life of the motorway as it should be a permanent structure. Construction standards require that the area should not lose ground in the excavation which might cause collapse. (Puller, 2003, p. 2) Failures in deep excavations Failures in deep excavations are sometimes caused by excessive deformation of the soil and the support structure, groundwater not adequately dealt with, and lack of quality in the soil support structure. Other causes of failure in deep excavations are: Inadequate planning and design due to lack of site investigation; Lack of information regarding soil, rock strength and groundwater conditions; Lack of knowledge and expertise on the part of the designer regarding the construction of the structure and other adjacent structures; Lack of consideration regarding the effects of ‘weathering and time on soil strength’. (Puller, 2003, p. 5) Engineers and designers have noted that there are soil deformations and movements (horizontal and vertical) in and around excavations. Design and performance of excavations should be properly studied especially when the soil involves soft clay. Burland et al. (cited in Puller, 2003, p. 6) conducted a study on movements near excavations into London clay. They found that the magnitude of ground movement depends largely on the method of construction, but that they also said that construction engineers should be able to estimate the upper and lower limits of movement. Engineers should use their calculation formulas and expertise in predicting deformation by calculating soil deformation parameters. (Puller, 2003, p. 6) Clough and Davidson (cited in Puller, 2003, p. 6) argued that the amount of ground movement depends on the strength or weakness of the retained soil and not on the strength of the supporting wall. But Goldberg et al. (cited in Puller, 2003) countered that stiffness or strength of the structure plays an important role in soil deformation. Risk Management Risk management is an important aspect of construction, especially in constructing a motorway. Procurement methods can influence what is called geotechnical risk management. Geotechnical risk management refers to the process of sharing this particular type of risk between client and contractor. The sharing of activities as contained in the contract has great influence in risk management. Risk management in construction amidst intense globalisation has to be well planned and well studied. Experience can help in the process of planning to minimise risks. Hazards in Construction The environment is at stake in the construction industry. Climate change will have its worse if no drastic action is enforced to construction projects. There is a poor record of safety and health promotions for construction workers and the community population where construction is on-going. Workers are at greater risk than the people in the community o sicknesses like cancer. The industry is one of the most risk-related sectors. Global programme on climate change, health and well-being of construction workers should be prime importance. How does the government do it? How can we wel in the ongoing fight against environmental abuse by construction firms? The ultimate problem is disposal of construction wastes. The construction industry produces hundreds of tonnes of waste and pollutants which form part of the environment and the atmosphere. It is a major generator of waste, accounting for 50% of the waste deposited in a typical landfill. (Institution of Civil Engineers, 1995, p. 1) Construction and demolition wastes contribute to environmental abuse more than any other sector. Reports of accidents are among the highest with fatalities ranked the third of all industries. Studies have shown that there is a link between attitudes of employees to safety to attitudes and behaviours of management. Management should play a role in promoting the health of workers in construction sites. (Pritchard, 2004, p. 172) Most construction firms do not have the required waste management programme. The system has been too risky to the environment, to the workers and to the community where construction is located. Companies should know how to identify risks and the keys towards a successful implementation of their strategic plan. Conclusion There are various problems that a Junior Site Engineer has to deal with in the construction of a motorway. But all these could be easily dealt with adequate preparation and management of the necessary activities on site. First, preparations involve on-site inspection or investigation. Theory is not enough; there has to be a coordinated effort among the contractors, engineers and the various stakeholders of the project. A vast amount of information will come from our databases regarding the soil classification, the construction site, manpower, equipment and a daily routine of on-site inspection in order to be prepared and to deal whatever problem what will come along the way. To summarise it, preparations, studies, analyses should be incorporated in the entire plan of building this motorway. References Durham.ac.uk. Road design – earthworks. Available from: http://www.dur.ac.uk/~des0www4/cal/roads/earthwk/mainear.htm [Accessed 28 January 2012] Gallagher, W., 2004. Geometric design issues and the development of computing practice so as to affect policy. In: P. Baldwin and R. Baldwin, eds. 2004. The motorway achievement: the British motorway system: visualisation, policy and administration. London: Telford Publishing. Ch. 10. Institution of Civil Engineers, 1995. Managing and minimizing construction waste: a practical guide. London: Thomas Telford Publications. Kameswara Rao, N., 2011. Foundation design: theory and practice. Singapore: John Wiley & Sons, Ltd. Ortigao, J. and Brito, H., 2004. Achors, bolts and nails. In: Ortigao, J. and A. Sayao, eds. 2004. Handbook of slope stabilisation. New York: Springer. Ortigao, J. and Sayao, A., 2004. Introduction. In: Ortigao, J. and A. Sayao, eds. 2004. Handbook of slope stabilisation. New York: Springer. Pritchard, C., 2004. Building for health? The construction managers of tomorrow. The Journal of the Royal Society for the Promotion of Health, 2004; 124. DOI: 10.1177/146642400412400409. p. 172. Puller, M., 2003. Deep excavations: a practical manual (2nd edition). London: Thomas Telford Publishing Ltd. Tomlinson, M. and Woodward, J., 2008. Pile design and construction practice (fifth ed.). New York: Taylor & Francis. Read More