analysis of failure of pavement

8/2/2019 Analysis of Failure of Pavement

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Analysis of Failure of Pavement

Section: (Super Highway N-5) Nooriabad - HyderabadKM: 101- KM:148

Introduction:

The vehicular traffic on our road network has grown manifold and most of the traffic load has been absorbed by the National Highway N-5 which today carries almost 55% of all inter urbantraffic of the country though its length is less than 1% of total road network of the country.

N-5 also serves all kinds of local traffic since it passes through cities and towns including pedestrians, rickshaws and other transport. Mixed traffic and road side friction due to ribbondevelopment along the N-5 prevents smooth flow of traffic and posses serious safety hazards.This has resulted in the high road transport cost presently being borne unnecessarily by thenational economy.

In the view of above, improvement of the National Highway N-5 is essential which in turn willcause substantial transport cost savings in the national exchanger.

The Government of Pakistan through NHA, with the assistance of World Bank has taken up therehabilitation of existing track N-5 under the improvement program NHIP (National HighwayImprovement Program).

In order to assess the existing condition of the NHA network, National Highway ImprovementProgram is started to address the increasing degradation of Pakistan's national highway system.This program is divided into three groups over a period of ten years. Group I is divide into two

phases. As part of this program in Group-I 11 selected sections of N-5 and a 48 km section of Karachi- Hyderabad super Highway (M9) will be upgraded. The improvement of highwaysincludes the rehabilitation and maintenance projects involve major reconstruction work,including the construction of additional carriageways, substantial earthworks, extensive drainage

provision and intersection remodeling

Details of Project:

Name of Project: National Highway Improvement Project launched under National Highway Improvement Program .

Funded by: World Bank.Section: Nooriabad - Hyderabad (Super Highway) KM 101- KM 148Length: 48 Km


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Cost (In Million): 575Client: NHAContractor: Sultan MehmoodConsultant: SMEC / Engineering Associates.Date of Commencement: 24 October, 2004

Date of Completion: 30 April, 2007

Failure of Pavement

The failure in the particular section was the development of ruts in the pavement. This increasein rutting has been due to the increase in truck tire pressure, axle loads or volume of traffic. As aresult of higher loads, more attention must be given to selecting high quality materials, indesigning the asphalt mixtures and in quality control during construction.

Concern for increased rutting led to the rehabilitation of this section (Nooriabad Karachi) sothat free flow of traffic can be continued.

Objective

The objective of this document is to analyze the type of pavement failure (Rutting) and find outthe causes of this failure of the section. Also, the other causes of rutting will be explored later on.

Rutting

Rutting is generally defined as Surface depression in the wheel path.Pavement uplift (shearing) may occur along the sides of the rut. Ruts are particularly evidentafter a rain when they are filled with water.

Types of RuttingThere are two types of rutting.

1. Mixed Rutting2. Sub grade Rutting.

Mixed Rutting occurs when the subgrade does not rut yet the pavement surface exhibits wheel path depressions as a result of compaction/mix design problems.

Subgrade Rutting occurs when the subgrade exhibits wheel path depressions due to loading. Inthis case, the pavement settles into the subgrade ruts causing surface depressions in the wheel

path.

Ruts are not only developed on highways or heavily trafficked roads as is gradullaythought. It is common phenomenon which everybody may have an opportunity to look at


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Type of Bitumen Axle Load and traffic volume.

All these causes resulted in fair depth of rutting. All these causes are inter-related.

The bitumen grade initially used in this section was 60-70 grade which was later on changed to40-50 grade during the rehabilitation of project. This 40-50 grade was introduced on trial basis.The bitumen grade was changed to meet the temperature requirements of the surrounding.

Similarly, the type of bitumen, axle load and traffic volume has serious effect on thedevelopment of rutting. The axle load on this section used is 12.5 tons (standard in Pakistan).But the trucks and other heavy trawlers exceeded the given load which resulted in the pavementfailure.

analysis of failure of pavement

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