Unit:5 Highway Mainteenance And Repair Note (Highway Engineering -II)

 5.1 Introduction

 Road maintenance is defined as preserving & keeping each component at the highway such as roadway, roadside, highway furniture, structure & other components as far as possible in their original condition & provide such additional work which is necessary to keep the traffic moving safely. 

► Importance of road maintenance:  

  ̶  It contributes to reliable transport at reduced operating cost. 

  ̶   It can slow the rate of deterioration & extent the service life of road.

  ̶ It can produce major benefits by reducing user costs as well as conserving the large capital investments.             

 5.2 Types of maintenance activities 

In general the following types are classified as road maintenance. 

a)  Routine Maintenance: Maintenance operations of localized nature required continually on any road whatever its engineering characteristics or traffic volume may be. The works are generally done by labor and can be contracted out (petty contractors). It covers the activities such as grass and bush cutting, grading and reshaping of unpaved shoulders, clearing of ditches and culverts, road sweeping, road sign maintenance, repair of road side structures etc.  

b) Recurrent Maintenance: Maintenance operations of localized nature and of limited extent carried out at more or less regular intervals of six months to two years with a frequency that depends on traffic volume. The works in general need to be done by the use of minor equipment. Activities for paved road within this category are such as sealing cracks, local surface treatment, repair of depressions, holes and ruts, pothole patching, edge repair, local reconstruction etc.  

c) Preventive Maintenance: Maintenance operation of road surface, geological and geotechnical nature to protect the road way. The activities within this category are sealing of raveling/stripping and meandering cracking, sealing of longitudinal and transverse cracks, laying of net on the slopes, trimming of loose materials including stones on slope, installation of subsurface drains. The construction of the masonry retaining wall/cascade/check dam/gabion wall, river training structures, river bank protection, slope protection with bioengineering etc.  

d) Periodic Maintenance: Maintenance operations of large extent required only at intervals of several years (generally at interval of 6years in case of black top & 4years in case of gravel road). Examples of activities within this category for a paved road are such as resealing (surface treatment, slurry sealing), resurfacing (thin overlay), repairing earth retaining wall, repairing parapet wall & railings at bridges & culvert etc. 

e)  Emergency Maintenance: Maintenance operations of highway generally done after 10 years or any unfavorable conditions are known as emergency maintenance.  Example:- Reconstruction of pavement, widening of roads, emergency maintenance by flood, landslide etc. 

 5.3 Maintenance of earth roads, gravel roads, WBM roads 

1) Maintenance of Earthen roads:  

Usual damages caused in the earthen road invites requirement of frequent maintenance which are the formation of dust in dry weather & formation of longitudinal & cross ruts along the road. 

  Remedial measures are:  

i) Frequent sprinkling of water, use of dust palliatives, spreading of moist soil.

ii) Reshaping of the road way during and after monsoon. 

iii) A surface treatment or provide a stabilized layer on the top.  

iv) Treatment with calcium chloride.

2) Maintenance of Gravel roads:

The usual damages are the formation of longitudinal ruts along wheel paths of vehicles & formation of cross ruts along the surface due to surface water. 

Remedial measures are:  

i)  Dust nuisance can be reduced sprinkling of water. 
ii)   Gravel should be spread over the gravel surface. For this reason, additional  material should be staked along the road on the berms before the onset of  monsoon. 
iii)  The volume of gravel staked should be sufficient to be spread over the full  width of road. 

* Maintenance of Water Bound Macadam Roads:  

WBM roads are damaged rapidly due to heavy mixed traffic & adverse climatic conditions. Due to fast moving vehicles the formation of dust during dry season and mud formation during rainy seasons, binding material of the pavement layers get loose and deteriorate soon developing ruts and potholes on the road surfaces. 

Remedial measures are:  

i)  To wet the road surface, water should be sprinkled periodically so that the clay & sand bind the stones properly

 ii) Spreading of thin layer of moist soil binder periodically usually after monsoon.  

iii) Use of dust palliatives. 

iv) Providing a bituminous surface dressing over WBM.

 v) Patch repair works on rut and potholes.   

vi) Resurfacing after the period of useful life.   

 5.4 Maintenance of bituminous roads (pot hole, patch repair   works, crack sealing, edge repairing, resurfacing) 

 The remedial measures of different types of defects in bituminous roads are given below:  

a) Pot hole:- pot holes are cut to rectangular shape & the affected area material in the section is removed. The excavated patches are cleaned, painted with bituminous binder, premixed materials are placed & compacted with 1cm above the general pavement. 

b) Patch repair:- patch repairs are carried out on the damaged or improper read surface. 

c) Surface treatment (crack sealing & edge repairing) 

The surfacing course is corrugated due to bleeding. The binders in the black top surfaces also get oxidized due to ageing.  

Remedies:-  

- Blotting material such as aggregate chips (10mm) or coarse sand are spread with small thickness of seal coat over the bitumen. 

d) Resurfacing:

- Resurfacing consists of the following sequence of operations:  

i) Cleaning the existing damaged surface by brooming.  

ii) Trimming the road surface & making a rough surface.

iii) Cleaned all loose aggregate, dust & applied water. 

iv) Apply binding material i.e. tar & spread chips.   

v) Rolling with the help of roller.  

vi) If the depth of a newly constructed road is more than 7.5cm the compaction  should be done in two or more layers. 

5.5 Maintenance of drainage structures                         

Road Drainage   

a. For long life of pavement and other components of a highway system, the subgrade should be kept at optimum moisture level and avoided to be over wetted.  b. Water should be drained away from the road and ground surface as well as under the surface by a system of surface and subsurface drainage. 

surface Drainage  

Water is drained from the road surface with adequate camber of both the carriageway and the shoulder. 

Road side drains are provided in all cut sections to remove water in the longitudinal direction.  

Toe-of-slope road side drains are constructed in low fill (<0.8m filling height) sections to convey water away to water courses  

Intercepting or catching water drains are placed on the back of the top of cut slopes to intercept surface water. Distance of these drains from the edge of the cutting should not be less than 5m.  

Flumes are provided to carry collected water down deep cuts or high fill slopes.   Drains should be provided with minimum 0.5% longitudinal grade. Trapezoidal shape of drains is preferred.  

Subsurface Drainage  

Subsurface water tables should always be kept 1 to 1.2 m below the subgrade level to protect pavement layers from excessive moisture.  

If it is difficult to achieve the above difference in levels, subsurface drains need to be provided.   

To save road subgrade from detrimental effects of moisture from the capillary rise of water a layer of granular materials is provided between the subgrade and the highest level of subsurface water.   

Sometimes geotextiles are laid over the subgrade soil to stop migration of small clay particles upwards that increase the capillary rise of water to the pavement.  

Subsurface drains are constructed with 150mm-200mm dia perforated pipes with well designed filter material around them and subsequently wrapped by geotextile with adequate longitudinal slopes. Numbers and spacing of subsurface drains should be decided by the design.  

The maintenance operation are followed under the following unit of drainage:-  

  i) Surface drainage maintenance:-   

a)  First of all detailed inspection of surface drainage & finding the problems.  

b) Cleaning the silt in side drain 

c)  Remove vegetations.  

d)  Regular inspection of drainage. 

(ii) Sub-surface drainage:-  

a)  Sub-surface drainage such as catch basin, Manholes, culverts, storm sewer etc are inspected regularly.  
b)   Used filter media for cleaning.  
c)    Remove the silt in the pipe of drainage etc.

5.6 Maintenance of miscellaneous road structures (shoulder, slope, retaining     structures, road furniture) 

a) Shoulder maintenance : shoulder give the lateral support to the pavement & also provide rooms for wheel I when crossing & overtaking on narrow pavement.so I proper maintenance is done on shoulder which may be I done by following:- 

i) Turfing:- Turfing is done to increase stability of . Shoulders. Light cutting of the grass should be done for good performance. The turfed shoulder should be immediately required.  

ii)  Soil stabilization: The stability of soil is increased by bituminous treatment used on the shoulder. 

b) Slope maintenance:- The maintenance activities are:-  

i) Cleaning of the road surface from time to time. 

ii) Control of erosion by seeding & Plantation.  

iii) Care of trees & Shrubs.  

c) Retaining structures;- Weep holes are checked regularly & cleaned. Otherwise retaining walls collapse due to the presence of water.  www.bibek00.com

i) Disintegration of the complete wall should be repaired by the presence of grouting method. 

ii) Mortar Joint in masonry should be refilled. 

d) Road furniture:- Road furniture can be maintained by applying single coat & double coat onto carriageway for separating lane, sign post etc should be lane periodically. 

► Measures to be taken for land slide stabilization:- 

Landslides may become an obstruction in the flow of traffic and roadway and hence it should be controlled at the proximity zones. Various measures that can be applied:  

a.Retaining structure 

During the construction of roads following the creation of straight alignment. In case of hill road the soil slope above the roadway is unstable due to toe under cutting. In such areas the soil mass can be retained by constructing suitable retraining structures like retaining wall, breast wall, gabion wall etc.   

 * Drainage Structure  

Drainage is the main problem and causes slope failure. The water penetrates through the earth surface and looses or reduces the strength of soil causing landslides. So it should be interrupted before it reaches the critical zone. For this intercepting drain may be provided to catch up the mater which may be surface or subsurface water. Adequate cross drainage structures should be provided at required places like aqueduct, syphon aqueduct, super passage etc. 

b.Slope protection measures  

For the slope protection measures, the following controlled measures should apply:  

    ̶ Revetment 
    ̶ Vegetation Riprap  
    ̶ Turfing etc.    

c. Use of Bio-engineering 

The protection of slope by application of vegetation systems with small engineering structure is called Bio-engineering. Bio-engineering system are:  

•  Grass planting 
•  Shrub planting 
•   Bamboo planting etc 

Measures to be taken for gully control works:- Preventive measures of gully control works are as follows:

i.) Provision of effective drainage system  

- diversion of surface water above the gully area.

-  surface water must not be diverted over unprotected areas will cause new gullies.   

- The basis aim of diversions it to reduce the surface mater entering into the gulley through gully heads and along gully edges, and to protect critical planted areas from being washed away small diversion ditches constructed either alone or with other structures.   

ii. Structural measures  

* Provision of check dams   
* Retaining wall   
* Breast wall  Revetment walls   

iii. Bio-engineering methods  

-   to control the gully formation by application of vegetation system with small civil engineering structure is called vegetation structure. 
 - It is the long term solution.   

-    Bio-engineering methods are mainly divided into three techniques.   

a.Seeding (Broadcasting, direct sowing in holes.)  
b.Seeding (Tree and shrub planting)   
c.Live cutting (Tree and shrubs) 

Road Lighting  

Rural highways should be designed with an open cross section & horizontal & vertical alignment of a fairly high type. Accordingly, they offer an opportunity for near  maximum use of vehicle headlights, resulting in reduced justification for fixed highway lighting. Provision of artificial lighting should be made on all roads near populated areas, on major bridges, bus stops, roads and railroads intersections (up to a distance of 250m from the point of intersections), tunnels and approaches to them and toll plazas.  Light mounting poles should be at least 9m high (but mounting heights of 10 to 15 m are usually preferable). They should be located outside the edge of the roadway or on wide central medians.   

Level of illumination should be 30 lux on important high speed roads and 15 lux on other main roads.   

The ratio of minimum to average illuminations should be about 0.4.