Infrastructure Development: Road Pavement - Coursework Example

Abdulaziz Alkheraiji number/S0057202 Introduction Road pavement refers to a hard and durable surface built in order to withstand high loads of motors, cycles and foot traffic. Due to their hardness they help auto mobiles move without tumbling into the surface. Paved road surfaces facilitate the carriage of this weight, and then distributes it down evenly, so that the ground beneath supports the weight without any damages. In more developed countries, roads are always maintained properly thereby making them even more durable, but in most of developing countries road sometimes become pathetic due to poor maintenance. This leads to them being damaged compromising their life span. Roads structures are always of two major types that are rigid and flexible; (Rigid and flexible pavement design and rehabilitation.1993)1. Which are mainly divided into, open granular flexible pavement which may contain one or more tailored layers, Bound granular flexible pavement, Segmental block pavements and Rigid pavements (concrete). Rigid structure always requires a lot of skills with special type of equipment to construct. During construction of the latter in many parts of the world, the construction companies starting from the engineers have often compromised the recommended composition of the materials used in construction. This mainly occurs either because of corruption, lack of enough funds to implement the paved road and lack of appropriate skills requisite for building of structure. Currently, there are few genuine engineers who specialize in the sector of civil engineering. Most people who claim this profession do not have the knowledge it takes to carry out a road construction job, yet they are always engaged in this process. This has hampered efforts by genuine engineers to come up with appropriate plan and implement them in the pursuit of real durable and sustainable structures. Road Pavement Composition and Functions Usually, when a road is being constructed, the ground is excavated to a required depth, which will depend upon topography of land, firmness of the soil and the level of the road required above the ground (Saeed& Hall, 2001 p33)2. The road will consist of the following layers. Sub-grade This is the bottom layer is exposed to the ground which has been excavated. Its uppermost level is referred to as the formation. The main function of this layer is to connect other road layers to the ground. The capping layer It is a granular type layer constructed immediately above the sub grade layer to provide a good working platform for subsequent constructions. Low cost materials are recommended for its construction. Sub base This layer is laid in order to prevent rain and sun which cause cracking to the surface. It is also necessary in road pavement construction as it underlines the significance of proper backfilling excavations which help in preventing moisture from attacking roads which have been excavated for use. The materials used here called the type 1 consist of rubbles or crushed concrete generally of different sizes of particles which helps with withstanding vehicles loads thereby preventing sinking. Bituminous materials can also be used for capping and sub-base layers which are part of foundation class 2 are designed according to HD25 (DMRB 7.2.2). Base This is the main load bearing layer in pavement road. Its thickness usually ranges from 100mm to 225mm depending on the types of load that will be subjected to it or depending on the nature of the land. In some cases lands which are sunken needs to be raised to reasonable heights. The materials used are bituminous bound i.e. dense bitumen macadam, rolled asphalt, cement and concrete base materials which are laid and compacted properly. Surfacing Consist of two courses namely, binder course and surface course which are sometimes laid as one course. Binder course are significant for even load distribution onto the base course. It provides a plane upon which the surface course is laid. Its thickness is usually within the continuum of 40mm to 110mm for fresh roads, and varies for the already existing roads. Materials that are in this course include open graded macadamized and rolled asphalt Surface course Its width ranges between 20 to 40 mm with the materials used chosen based on the load to be sustained by the road. There is also wide use of bituminous materials like hot rolled asphalt compost of high fines and asphaltic cement with boulders of rather smaller size (ballast form). A thickness of 40mm with 20mm coated chips applied onto the surface help maximize friction thereby preventing sliding. For cement bound and hydraulic bound layers refer to chapter 3, of DRMB. Factors to Consider When Designing a Highway The way a highway is designed plays is vital for its general management. The design a pavement haves great impacts on its operations. Safety of highway relies entirely on the alignment of the highway (Robinson, 1976 p 24)3. For instance, a smooth and wider highway may allow motorists to over speed. In the event of road construction a number of factors may be considered as discussed below. Highway geometry This refers to physical features of the like its surface, width among others. These features greatly influence the use and happenings of the highway. Road geometry principles for better designs are further outlined in TA91 (DMRB) Road surface This the area on the road used mostly by motorists. When the road surface is in good condition it positively impact on the operation of the motorists by allowing smooth flow of traffic. In contrary, smooth road surface may impress the motorists to over speed thereby leading to crushes. When the road surface is rough it may lead to vibrations in the vehicles leading to mechanical breakdown, rough roads also function to check the drivers speed as the diver may attempt to slow down in order to minimize the noise made due to vibrations. On the other hand, potholes may lead to accidents, especially when they are negotiated, the vehicle may hit a pedestrian who is by the road side. Therefore the road surface should be maintained in good condition for the benefit of all the road users. Width Properly maintained highways are always divided into lanes, wide lanes increase the driver’s usable area and this would promote speeding thus high chances of crashes. Narrowing of these lanes help to some extent by checking the motorists’ speeds, but it is not always recommended since head on collisions are always common. In many parts of the world yellow lines have been used to demarcate lanes for cyclist and motorists due to their reflector ability. Guidance on climbing lane are outlined in DMRB volume 15, part 7, paragraphs 2:11 and 2:12 for single carriageways and paragraph 3:11 for dual carriageways. Other road geometry include curvature both vertical and horizontal curvature. Road side environment This refers to the surrounding of the road especially the adjacent areas and their impacts on the road’s operations. For instance objects such as post and vegetation may to some extent check the speed of the vehicles as the driver would be keen not to hit them. In the contrary they may reduce the clarity of the highway thus accident cases may occur. Therefore the adjacent areas to the road should be clear with very little vegetation so as to minimize accidents. Communication The highway should have sufficient information to guide the users. These ought to be expressed in simple terms that are readable to everyone. Road signs are used here with relevant pictures to help in interpretation. Lighting conditions Proper lighting is recommended especially in the dark alleys of towns. Since designs of many roads do not always include lighting due to cost. Adequate lighting should be installed along streets in towns and cities to enable safe night operations for motorist, cyclist and pedestrians. Design of Flexible Pavement Site survey This involves a physical site investigation of the proposed development site by conducting a comprehensive survey usually a topographical map that contain site orientation, site boundaries and location of watercourses and rock outcrops (Washlaski, 1979 p61)4. A baseline report is then produced for the professional involved in developing the pavement. Geotechnical reports are also availed to the architect and the structural engineer. The engineers would again re-inspect the site to take soil samples for analysis. Pavement thickness Set the pavement thickness depending on the amount of load anticipated for the pavement to withstand. This is clearly is done by a clearly outlined American Association of State Highways Officials (AASHO) (Kersten, 1968 p 112)5. The model help development improved pavement performance in terms of vehicle loadings, strength of the roadbed soil and the pavement general structure. The pavement layout thickness is calculated as; log10W18 = ZR*SO +9.36*log10 (SN+1) - 0.20 + Log10 PSI 4.2-1.5 0.40 + 1094 (SN+1) 5.19 + 2.32*log10 (MR)-8. Where by SNR is structural Number required inches. W18 = Accumulated 18-kip Equivalent Single Axle Loads over the life of the project (18-kip) ESAL. ZR = Standard Normal Deviate. MR = Resilient Modulus psi SO = Standard Deviation. ΔPSI = Change In Serviceability. The design periods The design period for a flexible pavement is speculated to be 4 to 20 years depending with the type of the construction work at hand. However, alterations can be made depending on the project specification document. Friction policy In pavement construction, there are two types of frictions namely dense graded and open graded. Friction is treated with a lot of concern since it boosts stability of traffic and other road users. Friction courses details are provided in the plan and are implemented according to the specification of the project. The flexible Pavement Design Engineer should closely work together with The District Design Engineer office (Statistical methods in transportation and safety data analysis for highway geometry, design, and operations, 1999)6. This engineer is responsible for providing the proposed pavement typical section sheets for relevant specification on pavement broadening, design speed, estimated speed, a change in design speed occurring within project limits and work to be carried out on the roadside. In order to come up with the durable and efficient flexible pavements the facts discussed above must be observed with great care and implemented as specified in the design standards. Designers are always urged to use HD 42 (DMRB5.2.5) that gives the procedure for designs which take care of the non-motorists road users (NMU). Requirements for Maintaining Infrastructure in Urban Settings Funds This includes the necessary funds allocated for the maintenance of the infrastructure. The funds should be made available by the relevant authority so to enable purchase of equipment and other resources to be used in the maintenance exercise. Remember delay in availing funds will halt any operations since funds lubricate any construction projects. Skilled labor In a wider perspective skilled labor may include the services offered by the professionals in the civil engineering sector. Technical knowhow is necessary for this exercise since it require insight of the infrastructure (Fox, 1994 p57)7. For instance, when a fault was made unknowingly during the original construction process, only an engineer who specializes in that field will detect it and how it is supposed to be rectified. Someone with little understanding may not stand a good chance to identify slight mistakes. Special equipment and application of relevant technology Requisite equipments that are capable of accomplishing the maintenance task at hand should be available (Brockenbrough & Boedecker, 2003 p36)8. For example in maintaining slight deteriorations say a blocked culvert, simple tools for scraping the silt out of the culvert will be needed while for maintaining damaged roads an excavator may be necessary. Similarly relevant technology depending on the modern design trends should be put into consideration. A structure of an outdated design may renovate to keep up to modern designs. Infrastructure assessment Assessment study should be carried out very frequently to establish the short term maintenance as these light maintenance may turn out to cause great dangers to life and properties if neglected. Assessment records should be kept for future reference. These records could also be helpful in the event of a general failure to trace the source of the failure. Monitoring and evaluation Monitoring is performed while the construction of the infrastructure is being executed. Its main objective is to improve the construction design and function while in action. It can be initiated as an internal construction activity to provide constant feedback on the progress of the construction. Evaluation studies the outcome of the construction in order to advice on the designs of future constructions. Conclusions From my observations, there are various challenges that are associated with the highways. They are traceable from highway design, implementation and use. Other challenges like the environmental factors have grave impacts especially when they combine with the artificial ones, which are mainly as a result of negligence and other bad human practices. Some of them are: Design problems Poor designs may be as a result of inadequate training or pretence. In places where pavements are not designed appropriately problems such as congestion of vehicles and pedestrians may be experienced. This is observed in major cities with older pavement designs. Wear factor This occurs mainly where the pavements are overused due to the large number of vehicles in cities. When the flow rate of vehicles at a particular part of the pavement exceeds the recommended number, the pavement stand higher chances of tearing down before its estimated life span expires. This is also experienced on the pavements which used wrongly. For instance, a pavement meant for light weight vehicle is used by a heavy commercial vehicle. Technology and accommodation Due to large number of vehicles in many cities of the world currently, engineers are working day and night to develop more advanced designs that can comfortably accommodate these vehicles. It still remains a challenge since none has come up with one and vehicles are currently locked out of the CBD of many cities due to congestion. Methods of Implementing Solutions Use of Continuously Reinforced Concrete This helps to hold the cracks that are developed by concrete soon after the concrete is further cracking is usual after the road has been used for a given period of time. Increased thickness of the pavements This will ensure that a pavement once constructed can support both light and heavy commercial vehicles. Among the ingredients that should be increased include the asphalt and cement and bituminous bound materials. Joint pavements These include use of contraction, expansion and warping joints. Contraction joints allow the slab to shorten when there is decrease in temperature and expand equally when the temperature. Expansion joints are in charge of stretching of the slab when temperature rises while Warpingjoints which hold the slabs together. Bibliography Brockenbrough, R. L., &Boedecker, K. J. (2003). Highway engineering handbook: building and rehabilitating the infrastructure (2nd ed.). New York: McGraw-Hill. Fox, W. F. (1994). Strategic options for urban infrastructure management. Washington, D.C.: Urban Management Programme, World Bank. Kersten, M. S. (1968). Application of AASHO road test results to design of flexible pavements in Minnesota. St. Paul: Minnesota Dept. of Highways. Rigid and flexible pavement design and rehabilitation. (1993). Washington, D.C.: National Academy Press. Robinson, R. (1976). The development of a computer method for designing the vertical alignment of a highway: Program VENUS. Crowthorne, Berkshire, [Eng.: Transport and Road Research Laboratory. Saeed, A., & Hall, J. W. (2001). Performance-related tests of aggregates for use in unbound pavement layers. Washington, D.C.: National Academy Press. Statistical methods in transportation and safety data analysis for highway geometry, design, and operations. (1999). Washington, D.C.: National Academy Press. Washlaski, R. A. (1979). How to do an archaeological site survey: a handbook on the preparation of the site survey form. New Alexandria, Pa.: Washlaski& Co.. Read More