GIS based road classification system for low volume roads

Highway Engineering becomes prominent towards the latter half of the 20th Century after World War 2. Standards of highway engineering are continuously being improved. Highway Engineers must take into account future traffic flows, design of highway intersections/interchanges, geometric alignment and design, highway pavement materials and design, structural design of pavement thickness, and pavement maintenance. Network analysis in geographical information system (GIS) provides strong decision support for users in searching optimal route, finding the nearest facility and determining the service area. Searching optimal path is an important advanced analysis function in GIS. In present GIS route finding modules, heuristic algorithms have been used to carry out its search strategy. Due to the lack of global sampling in the feasible solution space, these algorithms have considerable possibility of being trapped into local optima. This study presents a methodology of categorizing a low volume road in a network which will be useful for future planning, using the addressed features in GIS application and capability of customizing features through programming language like visual basic 6.0. This also presents a model for classifying low volume road network system using multiple parameters. The Kesbewa DS Division was taken as the study area for this research and first main parameter considered was the shortest distance and adjusted shortest distance. The Map of the selected area is adopted and regenerated in to feature solution of ArcGIS 9.3 and network analysis component of ArcGIS 9.3 is used to obtain the routes of each goal nodes and other nodes by selecting different parameters. The Network Analysis component has been implemented by Digistra Algorithm. The customization capability with programming language like VB 6.0 is used to develop a customized software component to gather all the possible links between each of two goal nodes and other nodes. The proposed software model presents the capability of finding the minimum path of any two nodes for each of factors, and also it is possible to compare two routes for particular two nodes relevant to the factors. The final outcome lists out all list of the nodes with number of link usage at each route

Towards a proper road classification system for economic development of Sri Lanka

Road transport is vital to economic development, since conveyance of both people and goods are vital for a country's growth. Within this context Sri Lanka too has been investing heavily on road networks during last few years. To sustain a a good road network, having a systematic road management system is essential. In such systems, roads are classified and recorded along with its attributes and all maintenance and planning is done using this system. Therefore road classification is the key and having a well defined procedure to classify roads is a must. However, at present, in Sri Lanka, majority of the roads are unclassified. In Sri Lanka, vast amounts of road infrastructure facilities have been built in the past and is still continuing, but ironically a proper classification system is yet to be implemented. Based on the current classification system, roads are categorized as "A" , "B" , "AB""C" , "D" and E class . Class A , B and AB roads are managed by Road Development Authority and are considered as national roads. The national road network consists of nearly 12,000km of roads. Class C and D roads are managed by Provincial Road Development Authorities and total length of class C & D roads is about 16,000 km. Over and above these roads there are many more miles of roads that have been built, yet not categorized under any of these classes and .. remained for years without a classification. Most of these roads are low volume roads and total approximated length is around 70,000 km. Majority of those roads are managed by Municipal councils, and Pradesiya Sabhas. The National Road Master Plan (2007- 20 17) has categorized them as E class roads. T'he : proper classification of all roads are important because it ensures that National, provincial and local government funds are spent on the appropriate road based on user needs and accountability is assured. Accessibility depends on many factors including the availability of roads, their condition, design and the means by which people can reach them and travel on them. Roads have two key functions which may not be compatible with each other, firstly, to enhance the mobility of vehicle users and secondly, to increase accessibility to locations where people want to travel to and from. Thus, high speed roads have fewer entry or exit points so that vehicles can better maintain their higher speeds whilst local roads have many points of access to residences, businesses and intersections which mean that traffic must move more slowly

Review the guidelines of overlay design for flexible pavements

This primary objective of this research is to compare the overlay design guidelines and verify the feasibility of them on Sri Lankan road network. This is focus on overlay design procedures for the flexible pavements. The study included the collection of required traffic and deflection data in several categories of Sri Lankan road network. Deflection data is needed to obtain the remaining structural capacity (Effective Structural Number- SNeff) of the pavement and can be collected through the related departments in Sri Lanka. Sub-grade strength parameters were found using the field and lab CBR (California Bearing Ratio) experiment. The main advantage of this comparison is to identify the most suitable design procedure of required structural overlay thickness according to the several traffic categories of traffic in Sri Lankan road network

Evaluation of the effect of superpave aggregate gradations on marshall mix design parameters of wearing course

The purpose of this study was to evaluate the effect of the Superpave specified aggregate gradation on Marshall mix design parameters. Twenty eight (28) asphalt concrete mixtures were prepared in three types of gradations such that the gradations were above, through and below the Superpave restricted zone. Samples were prepared for Marshal mix design and tested in the laboratory to evaluate the Marshall stability, flow and volumetric properties. Statistical analysis showed that all three types of mixtures, above, through and below the restricted zone, did not have any significant difference on Marshall stability and void in mineral aggregate (VMA). The mixtures with gradation passing below the restricted zone showed higher air voids (Va ) and lower flow values than gradation passing above and through the restricted zone. The results indicated that Superpave specified aggregate gradation could be used as a guide to select aggregate gradations for wearing courses. Aggregate gradation below the restricted zone requires 0.5 % less bitumen than typical mix designs and has a lower binder tolerance limit. Keywords: Aggregate gradation, Marshall parameters, restricted zone, Superpave gradation, wearing course

Review on flexible pavement design guidelines

The primary objective of this research is to identify the proper design guideline in terms of strength of the structure that enable to last longer life span. Field testing was conducted to check performance of selected pavement design using AASHTO and TRL Road Note 31 guidelines. Finite Element Model was developed and validated with field data to analyze the performance of different pavement designs. Validated model was used to evaluate the structural performance of AASHTO and RN 31 Designs for different ESAL and Subgrade support conditions

Failure analysis of a semi structural pavement using a mechanistic tool – case study for a provincial road

Pavement design is a vital part in new road construction and in rehabilitation projects. Conventional flexible pavements are layered systems with high stress intensity on top and low intensity at the bottom. AASHTO method is widely used by most of the road agencies to design pavements while the Transport Research Laboratory (U.K) Road Note 31 (TRL RN-31) specifies for the tropical countries. Both these design guidelines are based on empirical formula or experimental studies conducted in extreme weather condition. Road Note 31 specifies the layer thicknesses of specific materials. It does not specify a method to adopt the materials that does not fit the specifications, which is the commonly encountered problem due to the varying site condition and availability of materials. Empirical design methods do not have any provision for analysing road failures and propose most suitable rehabilitation method. Therefore this research focused on evaluating the suitability of a mechanistic empirical pavement design tool to investigate a pavement failure. In this study, failure of a Sri Lankan rural road which is failed immediately after completing the construction was selected for the analysis. This road was designed according to the Overseas Road Note 31(ORN 31) as a Double Bitumen Surface Treatment (DBST) road and it has shown longitudinal cracking on the surface followed by the depression and the settlement, approximately after six months from the completion. Heavy axle load applied on the pavement due to transporting of construction materials to a new project has increased the propagation of cracks and potholes. Soil samples collected from the critically damaged locations were tested and the results showed that the inadequate strength of the pavement structure as the cause to the failure. Failure investigations were done using a mechanistic tool called CIRCLY and reliable reclamation method was proposed

Ditermination of optimum nominal aggregate size for single surface dressings

Surface dressings can be used as a successful road maintenance activity if carried out properly. One of the main decisions to be taken in designing a surface dressing in road maintenance is the selection of appropriate aggregate size. Improper selection could tarnish the performance of a surface dressing. The aim of this study is to find the optimum size of aggregate for a single surface dressing, especially in Sri Lankan Macadam roads. General size of aggregate for a particular surface dressing could be found using two parameters, commercial traffic volume on road and surface hardness of the road based on many available highway literature. But the aggregate sizes selected in above simple method have shown inconsistent results in Sri Lankan roads. Therefore tests were carried out to find the most appropriate aggregate size for the surface dressings in medium to low traffic Macadam roads in maintenance operations. Three most suitable nominal sizes of aggregates were selected using commercial traffic volume and the road surface hardness to begin the tests. These three sizes of aggregates were used to carry out three different surface dressings in the same road but in different stretches. Binder type were kept constant and binder rate was changed according to the aggregate size. The performances of these three surface dressings were evaluated by measuring aggregate removal rate and skid resistance. Digital photographs of demarcated locations in surface dressings of different aggregate sizes were taken at pre determined time intervals. .The numbers of aggregate were counted in each photo after certain time intervals up to 12 weeks and using this data, the behavior of each surface dressing over a period of time was studied. The aggregate size that could keep most of aggregate intact in its dressing after a certain time period would be a more durable chip size. The next aspect of checking performance of the dressing is the skid resistance. The techniques utilized to measure this value are Locked wheel test and Sand patch method. These tests were done after 12 weeks since the operation a sufficient enough to stabilize the dressing. The comparison of aggregate retention on road surface and the skid resistance after 12 weeks will give the short term performance of three aggregate sizes. It was found that 9.5mm aggregate size has better performance in aggregate retention and the 12.5mm size has better skid resistance

Development of guidelines for low volume concrete road construction in Sri Lanka

The purpose of the study was to develop guidelines for construction of low volume concrete roads in Sri Lanka. A survey was carried out to study current concrete road construction practices and knowledge of the contractors involved in concrete road construction. Survey results show that good practices have not been adopted in low volume road construction in Sri Lanka. The authors have introduced best practices which can be easily adopted by the local road construction industry. Incorrect joints construction was observed in concrete roads during the site visit and the Authors have introduced a new device for contraction joint construction. A modification to the available method was proposed to measure surface undulation on local concrete pavements and allowable undulation was determined through field investigation. A comparison of various kinds of concrete producing and curing methods and their performance were studied. The authors have evaluated the effectiveness of rebound hammer method which has been used for quality control by some consultants. Rebound hammer reading was compared with compressive strength which was found out from core cutter samples. Double beam vibrator with inbuilt camber was introduced to consolidate and form the camber of the surface layer. Check lists for subgrade /subbase, shoulder, formwork and concrete placing and finishing have been introduced to address weakness and enhance the quality of the pavement construction. Quality and Cost control techniques in the field of low volume concrete road construction in Sri Lanka are also described. Further, the proposed guideline describes the most appropriate methods for preparation of subgrade, subbase and shoulder, and mixing, placing and finishing of concrete

Improved concrete mix design for interlocking concrete block pavers incorporation industrial application aspects

Particle packing optimization is a process of selecting optimum aggregate proportions that result in minimum voids and maximum density thus requirement of cement and water can be minimized. The concept of particle packing is adopted to determine sustainable concrete mix for interlocking concrete block pavers (ICBP). Typically the aggregates used for the ICBP are 12mm coarse aggregates with manufactured sand and natural sand as fine aggregates. Fresh concrete is poured into the mold and both vibration and compaction is applied to cast the block. The mold is removed soon after the block is cast. Hence a low water cement ratio and high green strength needs to prevent edge falling and cracking of freshly cast ICBP. Present industrial practice seems to be far less economical due to the use of high amount of cement, wastage of aggregates, and high energy consumption of machines due to improper mix proportions. Hence high strength variations within the same batch is visible. Theoretical packing models such as Toufar, De-Larrad, CPM, LPDM, Powers, Shilstone chart were analysed to determine the most suitable packing model. This study proposes improved sustainable mix design using packing density method by optimization of parameters such as water-cement ratio, coarse to fine aggregate ratio, quarry dust to natural sand ratio, cement content and compaction effort. Trial mixes were tested increasing excessive cement content from 20% to 40% in 5% intervals. The water cement ratio of 0.32-0.36 is suitable with 65-70% of fine aggregates. Further, 65-70% of manufactured sand (as a percentage of total fine aggregate) should be used to maintain green strength of the mix. Optimum vibration time should be 5-7 seconds with an optimum compression of 1.7 -2.0 MPa. The study reveals that optimization of mixture design parameters can reduce the cement content by 30% while maintaining the same concrete strength

Engineering properties of cement and lime stabilized silty sand in pavement sub bases

Chemical stabilization of soils is a widely used practice for improving engineering properties of soil. This technology is used very effectively in developed countries with standard and appropriate machinery specific to them. This study is focused on sensitivity analysis of important parameters of soil stabilization and the effect of nonstandard machinery on improving of medium plastic silty sand soil which is abundantly available in Sri Lanka. Three soil samples of silty sand with medium plasticity which do not meet the specified requirements for subbases were studied. Laboratory test results indicate that both stabilizers improve spil properties up to a considerable degree. Comparison of Unconfined compressive strength (UCS), degree of p^0m verization (DOP) and mixing time for drum mixing and rotary mixing were made and it was found that the rotary mixing provides higher UCS and DOP with a minimum number of mixing cycles. It was observed that the DOP and UCS reduce with extended mixing time in drum mixing and values slightly increase after achieving the maximum in rotary mixer. Two possible compaction scenarios (under prevailing moisture content and ojry timum moisture content relevant to the compaction time) were evaluated for both cement and lime stabilization. Furthermore, variation of the optimum moisture content (OMC) with the time was studied for cement stabilized and lime stabilized soil. Test results show that compaction time (delayed compaction), moisture content at the mixing time and moisture content at the compaction time are crucial factors that must be considered in soil stabilization with cement and lime