Premature Failure Of Road Network

Premature Failure Of pass NetworkBahria town ltd started its get upment deeds in 1996 as a joint partner with Bahria foundation ab initio British Columbia were the consultants on the barf. The extraordinary progress rate and mellowed quality consultancy work of British Columbia (pvt) ltd was thought to be a big hurdle in the progress rate, even sotu ally the agreement with the consultants complete and Bahria Town (pvt) Ltd formed its own consultant wing. Unfortunately the consultancy wing failed to generate be mystify of incompetent individuals who burn really invest their heart and souls to address magnetic core issues .Site management and technical / top supervision issues were ignored .Today Bahria Town is cladding problem of premature nonstarter in its driveway mesh topology.Most of the road profit has not been under projected duty for which it has been numbered even then road failures be prominent .Most common land failures depictive be settlement of road, flexural press studing, weathering of the road network. The mechanism of road failure is quite interlinking and it is tedious to identify the root cause of failure.The approach adopted was to give way road network truly depictive of premature pavage failures, the instance sections were selected from the road network under study .Various field and laboratory mental test were performed on each section to determine the cause of premature pavage failures.The investigation revealed that ripple produced from mineral pitch plant fails to meet specifications. The crunch of HMA and incidental road set outs is not adequate. The source class for totald base is unlawful .The Plasticity of fines is not in tolerance diverge. paving structural job example depths were not executed on site besides pitiful guile and indecent patching procedures.Keywords Premature Failure, Flexural scissure, Weathering, Source gradation.UndertakingI establish that enquiry work titled To inve stigate the causes of Premature Failure of avenue Network of Bahria Town to direct its Remedial Measuresis my own work. The work has not been presented elsewhere for assessment. Where bodily has been employ from other sources it has been properly acknowl coastd/ referred.Tehseen Ellahi2k9-MSc-Trans-05AcknowledgementsThis research work is obviously a answer of the initial encouragement and documentation in admission to the MS Transportation (Taxila) by Ehsan ul Haq, the theatre director global Planning and Design, Bahria Town (pvt) Ltd. Extraordinary help and support form genus Rana Zulfikar Ahmed Khan , Site Manager Bahria Town (pvt) Ltd.Continuous encouragement, and valuable input from Dr. M. A. Kamal, Director Taxila Institute of Transportation engineering science (TITE) and Dean, Faculty of Civil and Environmental Engineering, University of Engineering and Technology (UET) Taxila. There guidance, comments and suggestions from beat to time, argon gratefully acknowledged .1.2.2 Rigid PavementsIn rigid pavages the stress is transmitted to the turn over out- drift through beam/slab effect. Rigid sidewalks crack sufficient beam effectiveness to be able to bridge oer the topical anaestheticized gunman- human body failures and studys of inadequate support.Factors effecting Pavement PerformanceThere ar legion(predicate) factors influencing the performance of a sidewalk, the sideline five atomic number 18 considered the or so authoritative (Transportation research board, England April 1985)1.3.1 dealingTraffic is the most important factor bear upon pavage performance. The performance of sidewalks is mostly affected by the make full scale, parade and the number of load repetitions. The damage caused per pass to a pavage by an axle is arranged relative to the damage per pass of a step axle load, which is defined as a 80 kN single axle load (E80). Thus a paving material is throwed to withstand a certain number of standard axle load rep etitions that leave result in a certain c relapse causality of deterioration.(Kamal M.A. et al., 2009)1.3.2 MoistureMoisture operatively reduces the supporting ability of posture materials, especially the pigboatmarine sandwich spirit level. Moisture enters the pavement structure through capillary vessel action. The resulting action is the wet climb up of particles, excessive movement of particles and dislodgment which ultimately results in pavement failures. (Terrel 1990)1.3.3 Sub trampThe sub grade is the move mold of soil that supports the bike loads. If the sub grade is not bulletproof enough the pavement depart show flexibility and finally the pavement will fail. Pavement will fail to perform ideally if the novelty in particles behavior is not catered for in the objective.1.3.4 Construction qualityPavement performance is affected by poor quality turn, inaccurate pavement burden or sonesses, and adverse moisture conditions. These conditions stress the nee d for skilled staff and the magnificence of good inspection and quality control procedures during spin.Pavement performance is parasitical on where, when and how maintenance is applied. No matter how good the pavement is built, it will deteriorate with time based upon the menti angiotensin-converting enzymed factors. The timing of maintenance is very important, if a pavement is allowed to deteriorate to a very poor condition, as illustrated by microscope stage B, then the added life comp ared with point A, is typically ab pop 2 to 3 yrs. This added life is about 10 percent of the total life. The appeal of repairing the road at B is four times of the cost involve at A. The delay of maintenance hold implications, in that for the cost of repairing one poorly weathered road (Point B), four roadstead at point A would go through to be postponed, which would mean that in a a few(prenominal) years the re organic law cost could be 16 times as much. Thus, differing maintenance becau se of budget constraints will result in a significant financial penalty within a few years.(www.nra.co.za/live/capacity.php) news reportBahria town is a modern township aforethought(ip) on an transport drawn from the home of American Society of cultivated engineers i.e the city of Reston, Virginia. The invention of its town ship is based on the most modern and unbending criterion.It is located between the GT road and Islamabad Bahria town borders Safari commonality on the northern side and is abuted to the south and west by Soan river and the Korang respectively.Town planning for Bahria Town has been done taking full reinforcement of the layout of the natural ground. routes stir been foundinged gibe to the art gaudiness rush hours. They have been standardized as 30, 40, 50, 60, 80 and Main Boulevards with the manakin of Pavement sidewalks and green areas.(www.bahriatown.com/index.php)Problem StatementBahria Town (pvt) Ltd fortifyment represents a unique mark of disti nction for Pakistan. Over a period of ten Bahria Town has emerged as Asias largest private property developers.The dilemma is that the capital problematical is huge and to meet market demands common Engineering enforces quality assurances are being ignored on account of time savings.One of the major(ip) problem , that Bahria Town that face today is related to premature failure of road network.ObjectivesThe main objective of the study was to highlight the causes of pavement failures and to propose the remedial measures.MethodologyReconnaissance survey in study area to identify problems.Selection of test sections based upon road classification and distresses for wakeless testing analysis.Extraction of samples from the test sections for different laboratory testing.Comparison of various parameters between damaged and undamaged portions of test sections.Recommendations on the basis of investigation.Chapter 3Chapter 3Introduction to Study AreaPavement Evaluation attend toPavement evaluation is the first step in the development of pavement rehabilitation alternatives for the project .It is the process of learning the existing pavement remains to understand the extent and the cause of problems prior to developing a rehabilitation plan.(www.pavementinteractive.org)Evaluation at Road Network LevelMonitoring of the network is carried out at on a network level to define the status of an entire pavement network as part of the pavement management system .To achieve the said objective the road network of Bahria Town was divided in different zones .Preliminary reconnaissance survey was carried out to access the pavement condition of road network .The object was to intimidate the study and help prioritize and select the evaluation at the project levels. The road network under study is Safari valley. (Design report on Bahria Town, ESS.I.AAR Consultants)The justification behind selecting this study zone is that this zone is fully true and in the possession of the resi dents therefore it is more naturalistic to study the road network performance of this zone.HistoryThe idea of Safari valley was conceptualized in 2000 confirming to planning parameters of the cities of Ruston, Virginia, USA. Ruston being the American society of civil engineers has been planned in the most beautiful manner, the next year Safari Valley lunched some other house project. One of the aims of lunching this scheme was to add a modern housing scheme with all the amenities for the general globe at an affordable cost. Any middle class person devouring(prenominal) of buying a plot in Islamabad/Rawalpindi could not do so as the price in Islamabad/Rawalpindi is beyond the make believe of the common man.. This scheme is planned and designed for the low-income people of the country to provide them affordable housing.(www.bahriatown.com/index.php)LocationThe Safari Valley is located in southerly part of Rawalpindi City, adjacent to Takht Pari forest on Japan Road. This site travel in Mauza Gali. The main access to this scheme is through Japan Road from G.T. Road, 3 Km from High Court to shelters Lahore. great hundred immense newly constructed Bahria freeway along River Soan is another access to this project which is completed a year ago.(www.bahriatown.com/index.php)UntitledFigure 3 Study area Location in road networkRoad NetworkThe proposed colony has been planned according to the contemporary principles of planning and design criteria of Tehsil Municipal Administration (TMA) for private housing schemes. pastime three types of roads has been proposed.Primary Roads 120 Feet wide 80 Feet wideCollector Roads 65 Feet wideStreets 40 Feet wideThe safari valley has 37.880 km of 40 wide roads, 6.083km of 65 wide roads, 1.23 km of 80 wide roads and 4.0 km of 120 wide roads.General ConsiderationsIt is desired by the consultant to provide the sub grade strength of the area in general for the verbalism of the knowledgeable roads. The purpose of the structura l design is to limit the stresses generate in the sub grade by the relations to a safe level at which the sub grade deformation is insignificant whilst at the said(prenominal) time ensuring that the road pavement layers themselves do not fail in both way within a specified period of time .In most design manners it is assumed that the routine and periodic maintenance is carried out during the design period of the road and that at the end of the design period , comparatively low level of detoriation has occurred.(Structural design of Pavement at Safari valley, SS nation explore Consultants)For the design of the flexible pavement the following factors should be unplowed in mind for guidanceEconomic ConsiderationsEffect of modality variant in the material PropertiesConstruction ControlUncertainty in traffic forecastingVariability in material properties and construction control is mostly much greater than desired by the engineer and must be taken into account explicitly in the de sign process. In practice only it is actually the variability of the sub grade strength that is considered and all other factors are controlled by setting out minimum welcome pass judgments for the key properties by means of the specifications.Nevertheless, it is the task of the designer to auspicate the likely variations in layer thickness and material strengths so that the realistic target nurses and tolerances can be set in the specifications to go everywhere the satisfactory road performances can be guaranteed as far as possible.Design basisThe purpose of the structural design is to limit the stresses induced in the sub grade by the traffic. Estimating the amount of traffic and the accumulative number of combining weight standard axles that will use the road oer the selected design life assessing the strength of the sub grade soil everyplace which the road is built by selecting the most economical combination of the pavement materials and layer thickness that will provid e the satisfactory service over the design life of the pavement when appropriate maintenance is carried out.In following paragraphs the component layers of a flexible pavement are referred in these termsSurfacingThis is the upper most layer of the pavement and will commonly consist of bituminous summon dressing or a premixed bituminous material .When premixed materials are laid in two layers these are cognize as wearing logical argument and base course (or binder course)Road BaseThis is the main load spreading layer of the pavement .It will normally consist of crushed stone or gravel ,or a gravelly soil ,decomposed rocks, sand and sandy clays stabilized with cement , linden tree or bitumen.Sub BaseThis is the secondary load spreading layer key the road base .It will normally consist of material of frown quality than that used in the road base such as un processed natural gravels ,gravel-sand or gravel-sand-clay. This layer also serves as a spreading layer preventing contamina tion of the road base by the sub grade materialCapping LayerWhere very weak soils are encountered capping layer is sometimes necessary. This may consist of better quality sub grade material imported from elsewhere or existing sub grade material improved by mechanical and lime stabilization.Sub browseThis is the upper layer of the natural soil, which may be undisturbed local materials or may be soil excavated elsewhere and placed as fill. In either grammatical case it is compacted during the construction to give it adequate stability.TrafficIn the present case no definite traffic pattern can be estimated as the construction period extends to a interminable span .During the construction stage, the maximum traffic even over rigorous trucks carrying mostly the construction material would apply. After the construction phase .the upcountry roads of the proposed project are subjected only to the light car traffic, which have very junior-grade destructive effect.The Sub grade Conditio nFollowing is the recommendations for the structural design of the bituminous come ond roads for the proposed project. The existing sub grade at the site comprises of A 4 soil with PI range of 5 to 8.Determining the sub grade strength is necessary for the road construction and required by the design engineer for the internal light traffic roads, which are required to carry up to (assumed traffic) 0.5 million cumulative equivalent standard axles in one direction for the design life of 10 Years.Field investigation and SamplingAll the field tests necessary for the design of the flexible pavements have been carried out .Test pit locations were selected so that overall attend of the sub surface can be examined .To do this samples from the different locations imperturbable for the classification and calcium bearing ratio (cosmic background radiation) .Following field and laboratory tests have been carried out in the detailField density and moisture essenceGradation analysisSieve anal ysis gravimetric analysisHydrometric analysisAASHTO Soil Classification science lab compaction testLaboratory CBR on soaked conditionsAppreciation of the sub grade conditionThe strength of the sub grade is commonly assessed in the form of California bearing ratio of the sub grade soil and is dependent on the type of the soil, its density and its moisture meansThe likely in situ strength of the sub grade is difficult to assess directly but its entertain can be obtained from the relationship between CBR, density and moisture content which must be measured in the laboratory for the soil in question, and form the knowledge of in situ density and equilibrium moisture content of the soil under the road. The density of the sub grade soil can be controlled under the road within limits by compaction at suitable moisture content at the time of the construction. The equilibrium moisture content of the sub grade soil is governed by the local climate and the depth of the water table below the road surfaces.For designing the thickness of the road pavement, the strength of the sub grade should be taken as that of the sub grade soil at the moisture content tolerable to the wettest moisture condition likely to occur in the sub grade later the road is opened to traffic.In the present case, field as well as the laboratory testing of different locations was carried out for gradation index and strength parameters and soaked CBR etc. The result of these tests are attached at the end of the reportThe CBR test shows the value of 3.5% having the representative design value of 90% and 95% modified by the AASHTO density .CBR value is considered to be unsatisfactory for the design of the flexible pavement .Therefore it is strongly recommended to provide capping layer over the existing sub grade soil to provide structural support and improve drainage conditions at the site. The thickness comes out to be 8 inches.Design RecommendationsThe pavement design of the internal roads of safari valley was figure using the AASHTO stave guide .Details of which are belowMethod 01Out of the different methods on tap(predicate) for calculating the road design, which cater for the repetition of the standard axle loads during the design life of the various traffic configurations expected on the road .This method caters for the site conditions and type of traffic likely to use the roads after the construction. The pavement design has been worked out as per Overseas Road argument No 31 (Transport and road research Laboratory, TRRL Road note 31)The topical anesthetic soil is moderately plastic for which average soaked CBR value was calculated to be 3.5 % and the same has been incorporated in the design calculations .In case of borrow /selected fill material is to be used for the making of the roads .The Laboratory CBR for that soil should not be less than 3.5 % against 96 hrs soaking.Method 02The pavement design of the internal roads of different categories is calculated usin g the simplified method as given in civil engineering handbook by Leonard Church Urquhart of which is given below.Design mapUsing the graph (annexure A) against the clayey silt conforming to A-4 Soil and CBR of 3.5 % the total thickness of pavement above sub base is 15 inches. Keeping a minimum thickness of 8 inches for the base course and the wearing surface the sub base is required to be 7 inches.Since method 1 gave higher values method 1 was adopted. malleable Pavement DistressesRoads have become important in our lives as a sole mean of communication. Modern roads are smooth, so people can travel easily from one place to another. support of road network is very important to ensure its continued aptitude and reliability. Normally roads are damaged due to environment affects, vehicular loadings and moisture.(Asphalt Institute , MS 16)Asphalt pavement distresses can in general be classified as one of the following typeCracking torturingDisintegrationSkid hazard surface treatment distressesDistresses caused can be related toWheel loadsEnvironmentPoor drainage substantial deficienciesConstruction related deficienciesExternal causes(Utilities)CrackingCracking takes many forms .To make proper repairs, it is first necessary to determine the cause of cracking .Maintenance procedures generally depend upon the cause of distress, the crack width and the amount of cracking in the affected area.Reflective cracksThese are cracks in mineral pitch overlays that reflect the crack pattern in the pavement structure underneath. The pattern may be longitudinal, transverse, diagonal or block. Reflective cracks are caused by vertical and crosswise movements in the pavement beneath the overlay, induced by expansion and capsule with temperature or moisture changes. They can also be caused by traffic or earth movement or by want of moisture in sub grade by high clay content. butt on cracksThese are longitudinal cracks 30 cm or so .They are caused due to lose of lateral suppor t, settlement or yielding of the material beneath the cracked area .This may be the result of poor drainage ,frost heave or shrinkage from drying of the adjoining earth. They may be accelerated by concentration of to a great extent traffic coterminous the edge of the pavement as well as heavy vegetation near the pavement edge.Block CrackingThey are series of interconnected cracks forming the series of large blocks, 1 to 3 m. Frequently they are caused by volume change of the fine aggregate asphalt mix that have a high content of low penetration asphalt and adsorptive aggregate ,daily temperature cycles and aged asphalt. Block cracking is not load related.Alligator CrackingThey are cracks that constitute to form series of blocks .They can be caused by various reasons such as excess deflection, sub surface moisture conditions, thin asphalt surface, excessive overloading, in adequate pavement design. If the asphalt surface is thin alligator cracking can quickly develop into potholi ng.Slippage CrackThey are crescent shaped cracks resulting from the horizontal forces induced by the traffic. They result from the miss of link up between the surface layer and the courses beneath. The insufficiency of bond may be due to dust, oil, rubber, dirt water or other non adhesive materials between the two courses. The Slippage cracks may result from the mixtures having a high sand content, as well as due to improper compaction.Linear CrackingThis category includes categories such as joint cracks, construction joints, shoulder joint cracks and diagonal cracks. Transverse and diagonal cracks can result from low temperature contraction of the pavement or from the shrinkage of the cement bound base or sub grade soils .longitudinal cracks in the wheel lane may be fatigue related and eventually progress into alligator and a random occurring Longitudinal crack can be indicatory of the sideways yielding sub grade or fill area. The cause of joint cracks (thermal and longitudina l) can be related to the thermal stresses or wanting(p) compaction. They can also be caused by a weak bond in the joint. aberrationPavement distortion is the result of asphalt layer instability or granular base and sub base weakness. Distortion takes a number of forms rutting, shoving, corrugation, falloff and up heave.RuttingRuts are channelized depressions in the wheel tracks of the pavement surface. Rutting results from consolidation, lateral movement of the sub grade, aggregate base or asphalt layers under traffic load. Rutting may occur in the sub grade and sub base due to insufficient design thickness, lack of compaction or weakness caused by moisture infiltration, down ward and lateral movement of the weak asphalt mixture under heavy wheel loads.Corrugations and shovingCorrugations and shoving are form of plastic movement typified by ripples crosswise the asphalt pavement surface. They occur in the asphalt mixes that lack mix stability. It may also be caused due to excessiv e moisture in the granular base, contamination due to oil spillage or lack of aeration when placing mixes using emulsified and cut back asphalts.Settlement or grade depressionDepressions are low areas of limited size that may be attended by cracking. They may be caused by traffic over loading or by consolidation, settlement or failure of the lower pavement layers.Up heave or swellUp heave is the localize upward displacement of the pavement due to the swelling of the sub grade. Up heave is most commonly caused by the expansion of ice in the lower courses of the pavement or sub grade. It may also be caused by the swelling effect of the moisture on the expansive soil. return cut or patch failureThis is the failure of the utility evocation or of a repaired area in the existing pavement. They usually are caused by lack of adequate compaction of the back fill, base or asphalt patch materials. Patch failures may also result from poor installation techniques, inferior materials or failure of the surrounding materials or under lying pavement.DisintegrationDisintegration is the breaking up of the pavement into small, liberal fragments. If the problem is not addressed the pavement disintegrates further until rehabilitation is required. disentangle/WeatheringThis is the progressive separation of the aggregate particles from the pavement surface downwards and from the surface inwards. Raveling usually occurs in wheel paths while weathering is found in non traffic zones and it extends over all surface.Raveling is caused by lack of HMA compaction, construction of thin lift during the cold weather, dirty or disintegrating aggregates, too little asphalt in the mix or over heating of the asphalt mix. Raveling almost always requires the presence of both water and traffic to occur.PotholesPotholes are bowl shaped holes resulting from the localized disintegration. Most potholes occur in the pavements having thin asphalt concrete surface on an untreated aggregate base. Thin surf aces showing severe alligator cracking begin to lose the pieces of the asphalt out of the cracked area creating potholes.Skid HazardsOne of the most common cause of the skid hazards in the asphalt pavement is a thin film of water on the pavement surface another is the thick film of water on the pavement surface that causes a high speed vehicle to hydro plane. Slipperiness may also develop from the surface contamination such as from oil spillage or certain type of clay etc. discharge or flushingBleeding or flushing is the upward movement in the asphalt pavement. This results in the formation of film of asphalt on the surface. Bleeding is identified by the pavement surface with a stick, glassy appearance that may be embarrassing to touch and usually occurs in hot weather .The most common cause of bleeding is excess asphalt in one or more of the pavement courses .Also traffic may cause the over compaction of the asphalt layers, forcing the binder to the surface.Polished aggregateThese are the aggregate particles on the surface of the pavement that have been polished smooth. nearly aggregates, particularly lime stone become polished rather quickly under traffic. Some type of gravel are naturally polished and if they are used in the pavement surface without crushing they will be a skid hazard. These polished aggregates are quite slippery when they are wet.Surface Treatment DistressesBecause of the construction procedures being used, surface treatments may develop some defects that dont occur in other type of pavement surfaces. These include loss of aggregate covert and streaking. Some of the asphalt pavement distresses such as corrugations, depressions, up heave, potholes and raveling occur most frequently in the pavement constructed with surface treatments.Loss of cover aggregateThis distress is identified by the whipping off of aggregate by traffic from a surface treated pavement. several(prenominal) things can cause loss of aggregate cover including weather to o cool, fast traffic permitted on the new surface treatment too soon, a surface absorbing part of the asphalt, aggregates that are too dusty or too dry etc.Longitudinal / Transverse StreakingLongitudinal streaking is alternate lean and heavy lines of asphalt and/or aggregate running parallel to the center line of the road .Transverse streaking is the same phenomenon except that the direction is running transverse across the road way. Several things can cause longitudinal streaking including improper height of the scatter bar, awry(p) asphalt handle speed, asphalt too cold, incorrect pump jam etc. Transverse cracking is caused by spurts in the asphalt spray from the distributor spray bar. These spurs may be produced by improper pump speed, pulsation of the asphalt pump etc.