Suggestions for improvement in construction
Roads are the most important component of infrastructure development of any society. Roads have vital importance in AJK as the area of AJK is generally hilly and the population is scattered, so one of the most important infrastructure requirements of population is road for easy and comfortable communication. So, for better roads construction following right up is prepared for discussion and loud thinking towards quality roads infrastructure development. I shall be great full for healthy and positive critics and comments on my article to help me correct my concepts or it may be help full towards the beginning of quality construction of roads in AJK.
There are following two main types of metalled roads:
- Flexible Pavement Roads:-
Flexible pavement has further two major classifications
- Water Bound Macadam Roads:-
Roads having top surface of stone, size less than 3” inches (i.e. macadam) bounded by clay and silt under optimum moisture content due to force of cohesion of clay in moist environment.
- Bituminous Bound Macadam Roads:-
Roads having top surface of stone, size less than 3” inches (i.e. macadam) bounded by bitumen (Bitumen is a substance extracted as byproduct of petroleum i.e. ethane or methane).
- Rigid Pavement Roads:-
Roads having top riding surface of P.C.C. (Plain Cement Concrete) or R.C.C. (Reinforced Cement Concrete) i.e. Top riding surface of rigid concrete.
The Roads of AJK have mainly following types and specifications.
- Earthen Roads:-
Roads extracted generally by earth cutting only having very little or nil retaining walls and constructed without addressing the issue of drainages (i.e. Longitudinal or Cross drainages), such roads generally have very less width and steep gradients i.e. lowest specifications.
Construction of such low cost roads is simply wastage of resources regarding communication sector of AJK, as it results in construction of roads having following serious flaws.
- i) Less width.
- ii) Steep grades.
iii) Sharp turns.
- iv) Without Longitudinal Drain.
- v) Without Cross Drainages.
- vi) Without proper retaining and breast walls.
Such roads are generally unsafe and unsustainable. Construction of such poor quality roads are being directed because of lack of funds, non availability of land as per required design and specifications, also usually the project leaders nominated by the notables are inexperienced ones (i.e. such roads are the result of political, socioeconomic, geological and funding constraints). If these roads are properly maintained, then these can only be used by small sized powerful 4×4 vehicles also such roads are highly risky and dangerous to travel on, even life threatening. Only highly experienced and alert kind of drivers with very good condition of vehicle can drive on such roads, so such roads are simply threat to lives of its users.
Also such roads are major sources of silting to dams because of steep grades and almost nil drainage facility the rain water (surface runoff) flows through the formation of roads with very high velocity resulting in scouring of surface and damage to existing retaining walls.
- Fair Weather Roads: –
Roads having better earth work of about 18 feet width, consisting of following specifications.
- i) 14 feet carriage way.
- ii) Low cost retaining structures i.e. generally R.R. dry walls.
iii) Longitudinal drains by only earth excavation generally having trapezoidal section.
- iv) Cross drainages.
General flaws in fair weather roads constructed in AJK are as follows.
- i) Such roads also have steep gradients in general.
- ii) Less widths on U-turns.
iii) Almost nil overtaking points.
- iv) Side earth cuttings in vertical profile.
- v) Some where the retaining walls do not justify the site requirement.
- vi) Nil breast walls even in sliding areas are observed.
vii) Almost nil parapet walls.
These roads are generally use able in only fair-weather conditions and needing regular maintenance by the beneficiary community or by the Department. In hilly areas such roads are generally being used by 4×4 vehicles and some where by powerful 2×4 vehicles too.
As these roads are not all-weather roads so such roads can not be comfortably used in rainy days. These kinds of roads may also be dangerous for travelers, so only experienced drivers along with reliable vehicles can travel through these roads. Such roads are also lives threatening.
- Stone Soled Fair Weather Roads (All Weather Rough Roads):-
Any well constructed Fair-Weather Road having stone soling of 6 inches thickness over its formation sub grade turns into all weather road, also by placing stone soling an impermeable layer is provided which reduces scouring and erosion because of water surface runoff during rainy season. Stone soling reduces water infiltration into formation soil of road causing reduction in fluid pressure and soil pressure behind the retaining walls (As soil itself behaves like fluid by water infiltration into the soil during rainy season) and results in failure of retaining structures.
Stone soling also provides a metal surface over the formation to reduce wheel load pressure to formation (sub grade) and results in reduction of excessive sub grade settlement by spreading wheel load over wider area, also stone soling never gets wasted for more than 1% (on the average) in years to serve and for any further construction towards metalling by either Flexible Pavement or Rigid Pavement and for further pavement it does not need to lay another sub base course but the laid stone soling performs best for sub base course, so it only needs grabbing of the overlying mud and dust before further metalling and surfacing.
Stone soled fair-weather road makes travel a little cumbersome due to its hard, uneven and rough surface. So, these kinds of roads are good for tough vehicles like jeeps, tractors and trucks to travel on. It may cause a little damage to vehicles caused by vibration and hammering effect of traveling through such rough riding surfaces which are not mend for delicate vehicles, but the road in result becomes safe to travel, less scouring, all weather, durable and requiring less maintenance. Also, such roads are good for Bituminous Bound Macadam Road or for Rigid Pavement in future, preferably after possibly best compaction and consolidation of sub grade and such stone soling as sub base, also it does not need any repeated laying of sub base course as the previously laid stone soling performs best for sub base course.
Causes of road failure / damages: –
General causes of failure of roads are as follows:
1- Absence of quality consultancy in designing of projects prior to construction: –
Generally, the schemes of projects proposed for construction are not very well worked and designed according to site and requirement prior to its sanctions, so for every project proper consultancy must be engaged.
Similarly, for all important projects of roads, there should be a compulsion of consultancy for qualitative preparation of schemes; hence to every constructional project the cost of consultancy must be incorporated to have better quality projects resulting in a lot saving by reducing the wastages because of poor quality proposals. This will result in long term economy by the construction of well and properly designed projects.
2- Poor construction due to lack of quality supervision:-
The departments responsible for execution of projects should be fixed to deliver quality projects as per well worked and planned quality prepared by the consultants.
So to improve the quality of construction the capacity building of concerned departments is the prime issue to be addressed thoroughly and for the capacity building, also time to time seen and unseen factors effecting the efficiency and quality should be addressed on very rational and logical grounds but after detailed consultation with every tear and level of such concerned departments.
Also a rational and logical system of incentives and accountability right according to justice is required to be introduced, so by increased quality of planning and monitoring on rational and logical grounds the quality of projects can be improved.
3- Quality Operation and Maintenance: –
The constructed projects must be operated as per system and ethics and for this the beneficiaries and inhabitants need to be educated. Similarly, permanent mechanism of quality maintenance of projects to keep the projects serving best for longer period is important to be focused on.
General observations about the flaws in construction of road projects.
- A) – Too Steep Gradients in roads: –
Steep gradients in roads cause difficulty to climb vehicles, resulting damages due to wheels slipping and scratching of road surface, also steep gradients cause high velocity surface runoff during rainy season and results in scouring and erosion of roads. Scouring of roads during rainy season promotes silting in dams too.
Steep gradients usually causes accidents of vehicles too which results in life losses as for many vehicles some times it becomes difficult to climb such high gradients which causes serious accidents and loss of precious lives occur and it generally happens on steep and defective turns, which can easily be judged by traveling through AJK that usually road turns and bends are marked by the names of people who lost their precious lives on those turns.
- B) – Vertical or Near To Vertical, Side Earth Cuttings: –
Generally the earth cutting on sides of roads are steeper than the soil friction angle or angle of repose of soil which causes frequent land sliding during rainy as well as in dry season, hence it results in frequent blockage of roads due to slides, so it is important to take good care about the soil cutting angle according to friction angle of soil (i.e. angle of repose of soil) or it will be further better that the side earths be cut in steps/slices, which can be more helpful for plantation to grow on and will keep the roads safe from sliding as well as it will help to produce wood for future and will also beautify the traveling and area too.
- C) – Absence of Longitudinal Drains: –
Generally either the longitudinal drains are non existent or not being constructed properly or because of non maintenance of the section of longitudinal drains, the water during rainy season crosses over the formation of roads resulting in scouring and erosion of soil and surface of roads along with failure of retaining walls. Hence very serious focus over longitudinal drains is required and its right designing according to its technical need of the site.
- D) – Absence or Improper Design of Cross Drainages: –
Cross drainages are either nonexistent or not designed according to the requirements of sites i.e. without under standing the fluid mechanics according to site geography. Hence proves to be nonfunctional or nonperforming. Hence qualitative and well-designed cross drainages are compulsory for quality projects of roads.
- E) – Poor Quality Retaining Structures: –
The classes of retaining walls being constructed in AJK are as follows:
- i) – R.R. Dry Walls: –
R.R. Dry walls means Random Rubble Walls laid Dry i.e. without the use of mortar, meaning the use of stone rubble in the shape it is extracted without being dressed, constructed without any cementing material. R.R. dry walls are good if laid properly and it economizes the cost of projects too. The Phenomenon of such walls is based on following fundamentals.
- All retaining walls must have enough excavated foundation depth to achieve well consolidated soil providing enough soil bearing to uphold the above coming load of wall without any excessive homogeneous or differential settlement, along with to provide sufficient passive earth pressure to retaining and breast walls.
As the soil retained behind the retaining walls causes pressure on retaining structure to push or move away outwards, this earth pressure is known as active earth pressure and it has affectivity of 30%.
Where as the soil which resists and does not let the retaining wall to move or slide in the direction the fill is forcing to move is called passive earth pressure which we achieve by enough deeper foundations in consolidated soil. This passive earth pressure has effectiveness of about 70% so a foundation depth of just few feet can hold a wall from sliding which is having high raised retained material on other side of wall towards the retained material.
Hence enough deep foundations are compulsory, to provide stability against sliding of retaining walls in outwards direction. But as per experience of field generally the walls laid on sites are not having enough depths.
- For R.R. dry walls it is better to have width at base of wall as (0.4 to 0.5)h preferably 5h (to have better safety factor) and should not be less than 2.5 feet for low heights of wall having value of 0.5h less than 2.5 feet, where as “h” is the height of wall by keeping this formula we achieve sufficient breadth of foundation as well as it provides sufficient slope on outer surface of retaining walls to keep the net weight (Center of Gravity) on the side of retained material and provides more length of moment arm to the mass of retaining wall against the toe of wall, which makes the wall to provide sufficient counter moment to retaining wall against the moment caused by the retained soil with reference to toe. The formula of 0.5h is valid for walls having height more than 5 feet, where as for walls having height less than 5 feet may be fixed to 2.5 feet width of its foundation. The top of wall is generally fixed to a width of 2 feet. These kinds of walls are good for maximum heights of about 16 feet (5metters), and not for very high raised retaining wall. R.R. dry stone masonry walls should be constructed vertical from inner side of wall towards the retained material and must have slope on outer exposed side i.e. from outer side to keep the net weight away from the over turning point of toe and to keep the net weight (Center of gravity of wall) near to the retained material resulting in counter moment against the toe of wall, which will protect wall from over turning around the toe.
As per field experience the breadth of walls are not being constructed according to any formula, which needs to be addressed with care by the supervisory staff of the executing departments.
- In foundations of retaining walls lying of lean P.C.C. pad can improve purposeful ness and sustainability, as it will help to distribute the above coming load in uniform and homogeneous manner to the sub soil, also to improve and strengthen the behavior of retaining wall as homogeneous and well integrated structure. To lay P.C.C. on soil in excavated trenches, the use of Polythene Sheet of heavy gauge can further improve the quality of P.C.C. to avoid direct contact of concrete with soil, which will improve quality and strength of concrete. The use of polythene sheet will provide underneath curing by utilizing water of mix for curing from bottom of P.C.C. pad, it will also prevent concrete from intermixing with soil causing weakening of cement bond and it will be serving as sealed shuttering hence the concrete will prove to be strong and durable by not losing either water or cement. Also after placing of P.C.C. in foundation it must be properly cured for at least one week before further construction for its better strength. Where as since now there is no use of P.C.C. base under the walls is adopted in general as practice in AJK and that is why heterogeneous load is placed over soil causing differential settlement and results in failure of walls.
- For R.R. dry stone masonry possibly, bigger sized stones must be used as the only bond in R.R. dry masonry wall is the weight of stone which causes to have friction bond between the stones of consecutive horizontal surfaces where weight of stone matters, which results the walls into a strong homogeneously bonded structure to retain material if constructed properly. The stone masonry must be of pattern that it should prove to be possibly uni-mass, so the courses of stone masonry must be laid in proper manner. Also, interim “through stones” must be provided to nail the R.R. Dry retaining walls structure and to cause it to have integration between consecutive vertical surfaces. A through stone is a stone having one dimension long enough to cover the whole or maximum breadth of wall.
But generally as per field observations usually the R.R. dry stone masonry walls which experiences failure have apparent good masonry on outer most visible course, where as inside the outer layer inferior quality stones are placed not in the form of courses but in the form of almost filling which instead of strengthening the retaining structures, causes load and hence results in failure of walls. Also it has been observed that the contractors cheat by making walls as stone pitching i.e. having same section width from top to bottom just the stones laid on sloping outer surface of earth to be retained, causing easy failure of retaining walls.
- The top of retaining walls for R.R. dry stone masonry is generally kept 2 feet wide and for the top layer bigger sized stones having more mass and at least one dimension of 2 feet laid in a manner that the 2 feet dimension of stones should be in 2 feet width direction of wall, to have firm top of wall to be capable enough to resist spilling water flow over the retaining walls during rainfall.
But generally small sized stones are used in walls and at top of walls, which easily moves due to over flowing of water during rains causing complete failure of retaining walls.
- It’s again good to have at least 3 inches thick (1:2:4) P.C.C. topping on top of all R.R. dry walls along with extra 33% to fill the gaps of R.R. dry masonry and smoothening of surface also for higher retaining walls it will be further good to have P.C.C. bands on different heights and levels of walls as per requirement of site, having thickness of 3 inches with 50% extra for filling the gaps between masonry and to level the surface of P.C.C. band.
- In sliding areas the roads must be provided with breast walls according to the need of site to reduce sliding. As sliding cause’s big damages to road sections and retaining walls.
- After rainy seasons timely repair of damaged walls can protect structures from major or total failures.
Summarized causes of failure of R.R. Dry Stone Masonry Retaining Walls
The summarized causes of failure of R.R. Dry stone masonry retaining walls are as follows.
- Shallow foundations of retaining walls.
- Less base width of retaining walls.
- Absence of sufficient outer slopes in construction of retaining walls.
- Absence or poor quality laying mechanism of P.C.C. in foundation of retaining walls.
- Use of small sized stones in masonry of R.R. Dry retaining walls.
- Wrong courses of laid stones. Especially from inner side of retaining walls.
- Absence of interim concrete bands in high elevated R.R. Dry retaining walls.
- Absence of P.C.C. toping on top of retaining walls.
- Absence or insufficient use of through stones in R.R. Dry stone masonry retaining walls.
- Roads without metalled surfaces.
- Improper or absence of drainage mechanisms of roads i.e. improper or absence of longitudinal and cross drainages.
- Absence or improper protection against land sliding.
- Absence of timely repair works.
- ii) – C.R. Dry Walls:-
It means that course rubble stone laid dry (i.e. dressed rubble masonry without cement mortar). It also has the same phenomenon as R.R. Dry walls, but it has better appearance than R.R. Dry walls. The stones used are course rubble, having dressed surfaces. But as per experience the stones are dressed for only outer most surfaces where as inner surfaces have same rough and quality less stone fillings inside the wall, instead of course rubble proper and qualitative inside masonry courses. C.R. Dry walls are even worst than the R.R. Dry walls as to have appearance of dressed surfaces the stones are broken down to smaller sizes, resulting in lesser weight stones and that is why the friction bond weakens. So such walls proves to be expansive than R.R. dry walls but less stable and durable than the R.R. Dry walls. So C.R. Dry walls should be discouraged.
iii) – C.R. Wet Walls: –
These kinds of walls have course rubbles i.e. dressed stones bonded with cement mortar. But as per experience the outer surfaces are just pointed by the mortar but generally no mortar exists inside the walls, also only outer stones are found dressed where as inner stones are generally observed as random rubble having cavities and hollow spaces, eventually walls from inner side are constructed without mortar.
One of the major reasons of construction of such poor-quality structures is due to lack of monitoring staff available in departments and are insufficient according to the number of projects, so due to insufficient supervisory technical staff and many other reasons it results in poor quality constructions. Also, absence of weep holes is another important reason of failure of C.R. Wet Masonry Walls.
- iv) – Wire Crate or Gabion Walls: –
These are the best retaining structures having bond of wire crates rapped around the well arranged bulk of stones and it can afford deformity and even then remains stable, wire crates or gabion walls keep on performing before the ultimate failure so such retaining structures are more sustaining and performing as retaining walls. Preferably heavy gauge wires of not less than “18 gauge” (i.e. 1/18 inches thickness) should be used having net of 4 x 4 inches also preferably bigger sized stones should be used and placed in proper manner of courses. In case of wire crates generally failures are due to use of less gauged wires, bigger sized meshes (i.e. 6 x 6 inches or more), use of small stones and not placed properly inside the wire crate boxes.
- v) – Plum Concrete Walls: –
These are the walls generally laid in (1:3:6) concrete with mass of concrete replaced by either 30% stone or 40% stone having different ratios as per suitability. These kind of retaining walls are good in general if laid properly can resist a lot and can provide more stable retaining structure but it proves to be expansive and it can not face deformity, as by having deformity it generally results in total failure as compare to wire crate walls. Causes of failure are improper concrete, excess usage of stone to theft concrete, less elimination of voids by not using any vibrator to achieve denser mass, absence of proper curing, less quality material usage i.e. usage of inferior quality sand or crush. Improper mixes and water cement ratios along with absence of proper curing. For plum concrete walls it is very necessary to provide weep holes at regular vertical and horizontal distances to let the water weep out and protect the retaining structure from hydraulic pressure.
- F) – Absence of Arboriculture (Plantation)
Roads must have arboriculture (plantation) on both sides of roads to provide soil stabilization and compensation to unnatural activity of road construction work. So every road estimate must include the cost of arboriculture as well as the up brining and protection cost of plants, at least for the period of initial maturity growth. Arboriculture may help in reduction of site soil scouring, silting to rivers and dams, also will reduce soil erosion and sliding, will also help to improve environment as well as wood generation for future needs. So a proper mechanism needs to be evolved for plantation as well as after words protection and facilitation towards the growth of plants on both sides of roads, so it will stabilize the soil causing protection to roads, also will reduce maintenance and will protect against scouring of soil resulting lesser silting to dams. Along with, it will improve weather environment and will produce wood to boost economy as well. This will beautify the traveling through roads and environment too.
- G) – Absence of Camber and super elevation
Camber and super elevation is compulsory for road quality as it helps in controlled driving of vehicle, rapid water drainage from the formation of roads, thus prevents the road formation from being damaged. As per general experience camber and super elevation are not observed during construction. So to ensure camber and super elevation in roads the contractors should be given additional incentive for its construction according to design, the incentive must be devised after consultation with senior field engineers to ensure camber and supper elevation.
- H) – Absence of required breast walls
Road sections passing through sliding areas must be provided with breast walls to cater or at least reduce sliding, but the breast walls must be designed according to the site requirements, best judged by professional engineers. For the terrain of AJK good quality gabion wire crates are better for breast walls but as per need good quality plum concrete walls and C.R. wet walls can also be used.
- I) – Providing of Impermeable stone metal layer (Stone soling / sub base course) on the surface of properly constructed Fair Weather Roads
The top surface of all fair-weather roads must be provided with a layer of stone metal as sub base course (6” inch thick stone soling). So, after at least one year of proper construction of fair weather road, as in duration of about one year at least the formation and sub grade almost gets sufficiently consolidated then stone soling (sub base course) preferably be laid over it. As the stone soling provides an impermeable metalled surface layer to the top surface of road which will not only make the roads all weather, but it will provide protection against erosion and scouring. It will support the wheel load by reduction of pressure to sub grade and resulting in less settlement of sub grade. Also, by having such impermeable layer the water infiltration inside roads formation during rainy season will also be reduced, causing reduction in fluidity of soil which is retained behind retaining walls, which results in less failure of retaining walls. So absence of stone soling over the surface of road formation (sub grade) generally causes failure to roads. Any further metalling over the stone soling should be delayed for at least further one year to let it be settled and consolidated to its maximum, which may result in durable road after words. Also after sufficient period the stone soling sub base gets settled to its limit and then after maximum consolidation of road surface if metalled by base course and bituminous wearing surface or as rigid pavement proves to be more durable than the roads which have all fresh metalled surfaces. Only a few more percentage of base course be given to cover the ditches, corrugation and ruts appeared on sub base course (stone soled surface) also extra percentage of base course against camber and super elevations may also be given to contractor to ensure the construction of camber and super elevation.
- J) – Never to Use filler material in base and sub base courses for Bituminous Bounded Macadam Roads
For metalling of roads, as flexible pavement (Bituminous Bound Macadam Road) or rigid paved roads the use of filler material in sub base course and base course should be avoided as it is the basic cause of failure of any metalled road there is no concept of any water bound macadam course in bituminous bond macadam roads, both of these are entirely different classes and should never be mixed up because of poor concepts. Presence of filler material causes capillary action due to reduction in void sizes and makes water surface tension effective for capillary action from sub grade. Moisture and water get trapped in filler material for longer durations after rainfall and does not let it to be drained down after rain, causing failure of bituminous surface, as bitumen loses its bond with stone in continuous presence of moisture for longer durations.
In almost every kind of filler material especially in soil passing through sieve # 200 a substance named “Mont Merlinoite /Bentonite” is used to be present which absorbs water and swells causing heave formation and again failure to the bituminous surfaces. Also by having filler material it does not let bitumen to have better bond with underlying base course, even after possible cleaning of base course compacted with filler material, only for about 10% to 15% stone of base course can hardly be naked to make just adhesive bond to some extent, which remains insufficient to have proper mechanical bond between base course and black topping, so the bitumen rests over surface just by its own weight without any logical bond which results in appearance of patches in very short period of service. So for sub base course the stone of size 3 to 7 inches and for base course stones of size less than 3” inch i.e. 1 ½ to 2 ½ inches should only be used, and no filler material be used at all, especially material passing sieve # 200 as it is clay and silt which has plastic and liquid behavior along with may posses Montmorillonite/Bentonite, also it facilitates to grow weeds and plants. Hence the items of filler material for sub base and base courses from S.C.R. item No. (21-13) & (21-14) should be eliminated as this item is authenticating filling in Sub base & Base course which is highly non technical item. The schedule of rates of 1979 and 1998 were according to AASHTO that’s why in both of these schedules against base course only 1 ½ to 2 ½ inches stone laying was mentioned and there was no any kind of filler material mentioned, as if filler material is to be used according to AASHTO specifications then its sieves no. passing and retaining along with percentages must have been mentioned to under stand its grading and proportion accordingly, which was never mentioned there. Also, for sub base and base course the compaction in form of relative dry density according to AASHTO is 100% in field, which is possible if there is no use of filler material, but if the soil is well graded then it is merely impossible to achieve 100% AASHTO compaction, as it is relative dry density. For compaction of sub base course and base course the terminology of mechanical compaction is used which is achieved by mechanical inter locking of stones and not by compaction of voids with the help of filler material in it, as that is not termed as mechanically inter locked compaction, presence of voids in well compacted base course and sub base course is good for its durability and purposefulness. Just because of the use of filler material there is always saving of Bitumen and crush stone for any thickness as compared to the standard consumption mentioned in books for any thickness per 100 sft.. If no filler material is used, the over all cost of construction reduces although more bitumen and crushed aggregate is used just because of cost of filler material its laying, watering, then cleaning and for the whole process and duration costing rent of machinery and cost of labor. The use of filler material is not logically convinced but is adopted in sub continent just by thoughtless practice or blind following. Sciences believe in logic and Engineering is purely based on logic.
- K) – Use of items named as bed run and pit run in place of sub base course and base course should be avoided in Southern Region of AJK.
In last few years items of bed run and pit run are introduced in southern region of AJK in place of sub base course and may be even for base course too. Where as the material used as bed run and pit run is good for embankment raising and should only be used as better material of sub grade embankment and filling in floors of civil structures but in no case, it is a better replacement of sub base course or base course.
Instead of bed run and pit run the bigger pebbles/rounded stones available in river beds and deltas of Mirpur and Bhimber are good igneous stones which became sedimentary by the transportation of water and have been grounded from its outer surface all around by the flowing water of rivers in millions of years resulting almost rounded shaped stones available in large quantity. So the stones having at least one dimension of 7 inches is good for sub base course if laid properly and its crushed stuff of size 1½ to 2½ inches is good enough for base course. Hence this locally available stone should be used for metalling, instead of bed run and pit run. The only reservation about these stones is for its outer smooth surface that it may not provide good bond but it doesn’t matter at all, and this stone can confidently be used as sub base course, base course and for crush to be used in bituminous wearing surface or crushed to size can also be used in cement concrete. As the stone will hopefully fulfill all the specifications, of AASHTO standards for the stones required in sub base course, base course and for bituminous wearing surface along with for concrete too. So it is requested to eliminate item No. 21-15(b) from C.S.R.
- L) – Laying of bitumen in hot and dry weather in hot form for its all layers of premix or T.S.T. and its compaction procedure to be improved.
Bituminous wearing surfaces must always be laid in hot and dry seasons, so for this the annual periods must be defined with conditions and should be followed strictly by the departments. Also, all the layers from tack coat to finished surface of bitumen courses must be laid hot and dry in consecutive courses.
For compaction of bituminous surface pneumatic tires rollers having three consecutive axes should be introduced to avoid linear corrugations and to produce smooth riding surfaces. As in AJK generally steel tire rollers are used to compact sub grade, sub base, base and wearing bitumen surfaces. Also, during compaction of bituminous wearing surface, the steel tires are kept wet by water to keep bitumen from sticking to steel wheels of rollers. Where as by watering over bituminous surface and to steel wheels the temperature of bitumen is immediately dropped down, resulting the bitumen to resist compaction and hence bitumen remains un compacted and porous, also the bond between different layers of bitumen weakens. The best laying of wearing surface is to lay hot bitumen using premix pavers and then compaction by pneumatic tired rollers without the use of water for better quality compacted premix.
- M) – For resurfacing the previous surfaces should never be demolished
If there be no problem with the raising of road surface, then it is preferred to never demolish the previously existing surfaces of existing metalled roads. And if only bituminous surface is to be placed then the previous bituminous surface should only be cleaned and dried and thus over it hot tack coat be laid before the new bituminous surface, as the previously existing surface will make the new surface more safe and durable.
Similarly, if further base course is required than over the previous surface simply lay the base course of required thickness directly without scratching or dismantling the previous structure, just compact the additional base course and lay a new surface of bituminous wearing surface over it. As the previously existing road is best to prove under load because of its possible best consolidation over span of time also by being firm and having previous bituminous surface it helps to stop capillary action of water from sub grade to road top layer of wearing surface.
- N) – Providing of stone curbs on either sides i.e. on edges of roads around sub base and base course inside the shoulder / berms:-
To keep the sub base and base course confine during compaction and to restrain the stone of sub base course and base course from lateral movement during compaction and under repeated loads of traffic, side stone curbs should be introduced between the stone metal and berms. Hence an item of curb on edge of metal should be introduced in roads construction. Providing of stone curb may also be helpful to protect road formation after the shoulder/berms gets eroded during rainy seasons.
- O) – Good quality construction material available in AJK:-
AJK is enriched with almost every kind of construction materials. There are three major classes of rocks:
- Igneous Rocks
- Metamorphic Rocks
- Sedimentary Rocks
1- Igneous Rocks
AJK has plenty of best quality igneous rocks which have following properties:.
- High crushing strength
- Very low porosity i.e. very less water absorbent.
- Very good to resist weather effects.
- Very good texture to provide good bond.
So such stones are very good for load bearing civil structures.
General properties of such stones are as follows.
- Good quality igneous rocks present in AJK provides stone having C.B.R. value of more than 80%.
- A.A. (Loss Angels Abrasion test) value < 20% after 500 revolutions, which is good for bituminous surfaces and stones with L.A.A. < 40% are good for base course.
- I. (Flakiness Index) < 25%
- Water absorption <1% → 2%.
- % loss in soundness test <12%
So, the stones which qualify the above properties should be adopted for road construction as per specifications.
2- Metamorphic Rocks
AJK has enough metamorphic material from where sand and good quality stones for road construction can be achieved.
3- Sedimentary Rocks
AJK has very good sedimentary rocks which can be help full to produce very good quality construction materials as at many places of AJK lime stone, clay and shale are available which are enough to have cement factories in AJK. So, a lot of cement industry can be established at many sites of AJK to produce cement. Hence the rocks of AJK are full of useful substances and minerals which can be helpful for construction and other industries.
But for easy and immediate extraction and use of all good quality construction materials which are available in AJK, proper legislations are required for its easy, un-hurdled extraction. So where ever the good quality material is available should be taken up as asset and property of AJK, so it should be available to all who need it un hurdled and without any litigation.
Thus, by having local materials of construction it will save a lot of cost of construction and will help to generate local employment and enterprises. Hence after detailed analysis the quarries are needed to be marked and the Government of AJK has to legislate to make it possible for easy and speedy extraction. A lot work is required to explore such valuable available construction material to be adopted and used.
Summarized Suggestions for good and sustainable roads in AJK
- Every project, especially road must first be designed by concerned professional consultant engineers according to site requirements prior to execution. Hence consultancy charges must become compulsory part of every project’s initial cost for qualitative planning of projects.
- Roads must be designed to have standard grade and for this matter Long Section must be prepared and finalized according to standard norms and then based on designed L-Section, cross sections be prepared, so in every development department there must be posts of surveyors with every Assistant Engineer/Sub Divisional Officer.
- The linear grade in straight part of road must not exceed from 5% to 7% and for unavoidable circumstances the limiting gradient for a length not more than 100 feet should not exceed by 10%. Similarly, the gradient on U-turns should not exceed from 3% but in unavoidable circumstances it should not exceed by 5% (limiting gradient for U-turns).
- Roads for Rural sector should not be of gross formation width less than 26 feet having carriage way of 22 feet to facilitate two way traffic on all the length of roads and having 2 feet wide shoulders on both sides of the carriage way, with 2 feet wide top of retaining wall on one side and 2 feet wide longitudinal drain on other side, so the total width should not be less than 30 feet. Similarly urban roads must not be less than 43 feet i.e. having 33 feet carriage way to facilitate two way traffic with comfortable and safe over taking margin with 3 feet wide shoulders on both sides of the roads (i.e. gross carriage way of 39 feet) and than having 2 feet wide top width of retaining walls on one side and 2 feet longitudinal drain on other side. As AJK is almost hilly area and road width should be sufficient enough to have safe traveling as in this hilly area at many places there is no margin of crossing of vehicles traveling in opposite directions hence it results in accidents causing damage and loss of precious lives. Safety of the travelers should be the top priority.
Instead of dealing with greater lengths of roads the priority should be given to quality of the roads. Quality communication is one important component which will give boost to tourism in AJK resulting in socio-economic change of the area. Good quality communication will result in boost to numerous kinds of local enterprises as it is one of the fundamental facilities for local enterprises to nourish.
- The entire earth work cutting should be according to the friction angle or angle of repose of soil i.e. less than 70 degree especially in non rocky soils or cut into slices or steps in a way to provide places for arboriculture having gross tangential profile of less than 70 degree.
- The longitudinal side drains may have “V” shape, instead of trapezoidal to facilitate self cleaning during rain fall, as well as to easy hosting of the wheel of vehicle thus providing extra margin of travel in case of no option. Also the wheel of vehicle will be able to easily go in and come out of the trench of longitudinal drain without harming vehicle or to travelers, so it can provide extra passage margin in case of emergency.
- Where ever there is threat of sliding, it must be provided with breast walls, which should be properly designed and best constructed by gabion wire crates to be able to afford deformity due to being malleable (flexible).
- Every road which is by compulsion to be constructed with minimum gross width of 18 feet, must have at least six over taking points per kilometer of gross width not less than 30 feet wide, having carriage way of 22 feet along with 2 feet wide shoulder/berms on each side and the length of crossing point not less than 50 feet. All U-turns must be treated as over taking points and than the remaining numbers of over taking points per kilometer be placed at regular distances in the remaining parts of narrow road lengths to facilitate over taking, parking or easy return of vehicles.
- All the U-turns must have outer radius of not less than 45 feet for rural roads and minimum 60 feet for all the urban hilly terrain roads.
- Roads must be provided with camber and super elevation as per design and standards.
- All the retaining walls must be of good quality and the methods to be adopted may preferably be gabion wire crates, plum concrete, R.R. Dry stone masonry or C.R. Wet walls as per requirement of site. But closely monitored during construction to ensure quality, so a lot of supervisory staff will be required to ensure better monitoring and better quality of projects.
- Roads must have arboriculture on both sides of roads to stabilize the soil and for many other benefits mentioned earlier.
- All the rural roads must at least be provided by a layer of 6-inch-thick stone soling to make it all weather, minimum after one year of construction of fair-weather road to let the fair weather road surface consolidated to its maximum. Also, by providing layer of 6-inch-thick stone soling the surface of the road becomes impermeable, non-scouring and will be able to resist excessive settlement of sub grade, as well as the failure of retaining walls will also be reduced.
- Parapets at regular distance of about 50ft must be provided on top of all retaining walls in hilly areas to increase traffic safety and at closer distance of about 25ft (maximum) on turns to protect the driver from being misguided.
- The humps and jumps in longitudinal directions of roads must be reduced to make the trafficking comfortable as well as to improve the safety for travelers by keeping the view clear to drivers instead of blind moves due to big humps jumps, corrugation and ditches. So additional cost to reduce humps and jumps be given to projects of roads but the quality must not be compromised in any case.
- Undue bends must be avoided, and the roads alignment must be designed to keep it straight to possible limit. To make traveling more comfortable in all respect.
- q) For metalling of roads, as flexible pavement (Bituminous Bound Macadam Road) or rigid paved road the use of filler material in sub base course and base course should be avoided as it is the basic cause of failure of any metalled road there is no concept of any water bound macadam course in bituminous bond macadam roads, both of these are entirely different classes and should never be mixed up because of poor concepts. Presence of filler material causes capillary action due to reduction in void sizes and makes water surface tension effective for capillary action from sub grade. Moisture and water gets trapped in filler material for longer durations after rainfall and does not let it to be drained down after rain, causing failure of bituminous surface, as bitumen looses its bond with stone in continuous presence of moisture for longer durations.
In almost every kind of filler material especially in soil passing through sieve # 200 a substance named “Montmorillonite /Bentonite” is use to be present which absorbs water and swells causing heave formation and again failure to the bituminous surfaces. Also by having filler material it does not let bitumen to have better bond with underlying base course, even after possible cleaning of base course compacted with filler material, only for about 10% to 15% stone of base course can hardly be naked to make just adhesive bond to some extent, which remains insufficient to have proper mechanical bond between base course and black topping, so the bitumen rests over surface just by its own weight without any logical bond which results in appearance of patches in very short period of service. So for sub base course the stone of size 3 to 7 inches and for base course stones of size less than 3” inch i.e. 1 ½ to 2 ½ inches should only be used, and no filler material be used at all, especially material passing sieve # 200 as it is clay and silt which has plastic and liquid behavior along with may posses Montmorillonite/Bentonite, also it facilitates to grow weeds and plants. Hence the items of filler material for sub base and base courses from S.C.R. should be eliminated as this item is authenticating and highly non technical item. The schedule of rates of 1979 and 1998 were according to AASHTO that’s why in both of these schedules against base course only 1 ½ to 2 ½ inches stone laying was mentioned and there was no any kind of filler material mentioned, as if filler material is to be used according to AASHTO specifications then its sieves no. passing and retaining along with percentages must have been mentioned to under stand its grading and proportion accordingly, which was never mentioned there. Also, for sub base and base course the compaction in form of relative dry density according to AASHTO is 100% in field, which is possible if there is no use of filler material, but if the soil is well graded then it is merely impossible to achieve 100% AASHTO compaction, as it is relative dry density. For compaction of sub base course and base course the terminology of mechanical compaction is used which is achieved by mechanical inter locking of stones and not by compaction of voids with the help of filler material in it, as that is not termed as mechanically inter locked compaction, presence of voids in well compacted base course and sub base course is good for its durability and purposefulness, Just because of the use of filler material there is always saving of Bitumen and crush stone for any thickness as compared to the standard consumption mentioned in books for any thickness per 100 sft.. If no filler material is used, the over all cost of construction reduces although more bitumen and crushed aggregate is used just because of cost of filler material its laying, watering, then cleaning and for the whole process and duration costing rent of machinery and cost of labor. The use of filler material is not logically convinced but is adopted in sub continent just by thoughtless practice or blind following. Sciences believe in logic and Engineering is purely based on logic.
- r) Regular maintenance must be maintained to keep the structures to serve best and for timely proper maintenance enough allocations of funds should always be available with the concerned departments.
- s) Toll system may be introduced in AJK to generate funds for O&M of roads along with generation of funds to deal with communication sector of AJK for improvement, up gradation and construction of new projects according to need and requirement.
- t) Projects must never be compromised to reduce initial cost of projects on the cost of poor specifications and quality.
- u) Instead of construction and up gradation of more lengths of roads every year, it is much more important to have quality projects against the available resources to have sustainable development, which may result in lesser length of roads dealt every year. Quality is more important than to have quantity
- For all high altitude areas which are in snow zones, mild longitudinal grades but broader rigid pavements should be preferred having 6 inches thick stone soling laid over well cambered and super elevated compacted sub grade, than laying of lean concrete of minimum 3” inches thickness with 50% to 100% extra lean concrete quantity to fill the voids of stone soling depending the nature and quality of lade stone soling, and after lean concrete a minimum layer of 4 inches thick (1:2:4) concrete divided in panels should be preferred, instead of having bituminous roads. As bitumen gets spoiled in presence of long-term moisture causing damage to roads but for rigid pavement very controlled grade of road is compulsory to keep the traffic travel in all seasons of year.
- Drainages of required design and quality must be provided in roads.
- For quality roads according to proper design the required land must be provided by the beneficiary community according to the design without any litigation or hurdle to ensure quality of road. Hence legislation for acquiring of land according to design of professional engineer is compulsory, to avoid wastage of resources and to achieve sustainable and qualitative development. Hence the projects should only be initiated if the beneficiary community is completely supportive to quality project construction. For the availability of land as per design, the revenue department of AJK should also perform responsibility.
- Good quality local materials which prove the standards required by specifications should be utilized to reduce the cost of constructions. But to mark the quarries and easy extraction of material legislation by the Government of AJK will be required. So that there should not be any litigation for its extraction.