Road Construction Methods PDF

ROAD CONSTRUCTION METHODS I. Introduction Road - is a structure that link barangays and cities in the country, and serve as medium in transporting goods and Aggregate subbase course commodities from one place to another, and as communication - an upper layer of...

ROAD CONSTRUCTION METHODS I. Introduction Road - is a structure that link barangays and cities in the country, and serve as medium in transporting goods and Aggregate subbase course commodities from one place to another, and as communication - an upper layer of natural soil which may be the undisturbed link which brings economic development to a nation. local materials, or soil excavated elsewhere placed as fill. Classifications of Road In either case, it is compacted during construction for road stability. According to usage Aggregate Subbase and Base Courses - are individual According to national importance stabilizing layers of selected material and designed thickness According to its surface course placed on top of the subgrade to distribute the load transmitted According to traffic volume from the surface course. Surface Course - is the uppermost structural component of the Types of Roads According to Usage roadway, which provides resistance to wear and shearing stress due to traffic load. National Road It also provides an even skid resistance surface with Primary National Road - the main highway trunk comfortable durability and is appropriately crowned to prevent line system that is continuous in extent that goes from rain water from penetrating into the subgrade. province to province and region to region. Shoulders - are located beside the carriage way which is the Secondary National Road - connects a provincial or total width available for passing vehicles, and is used to receive national road to a public wharf or railway station. lateral clearance to protect major structures on the roadside, to Provincial Road - connects two municipalities or cities within a province secure safety and comfort of both motorists and pedestrians and City Road-street within the urban area of the city. for emergency stopping purposes. Municipal Road- street within the poblacion area of a municipality. Drainage Structures/Slope protection/retaining structures Barangay Road– street located outside the población area Miscellaneous structures of a municipality or urban area of a city and those outside industrial, commercial areas or residential Drainage Structures - are located beneath or alongside the subdivisions. roadway used in collecting, transporting and disposing of surface water originating in or near the road right-of-way. Types of Roads According to National Importance Types of Drainage - can be lateral drainage such as a U- shaped, V-shaped lined canal (side ditch) or perforated drain Major roads are those roads of national importance. They are canal. frequently used by traffic and leads to vital areas such as major It can also be transverse or cross drainage such as a box culvert cities and installations. or a pipe culvert. Example of major roads are those roads classified as National Slope Protection Structures - are constructed along the side of Roads or those which are part of the highway system. the roadway to stabilize the slopes. Retaining Walls - are constructed along the side of the Minor roads are roads which is local in nature as it serves only roadway if there are space constrictions. the interest of the locality such as a street. Minor roads are less Erosion and sediment controls are constructed to prevent frequently used by traffic. detrimental effects. Difference between a Street and a Highway II. PREPARATORY WORK Highway - can accommodate greater traffic volume. Street or road - serves service area connecting to highways. Preconstruction Conference /Preliminary preparations As-stake survey Types of Roads According to Surface Course Temporary facilities Earth Road Access and detour roads (Traffic Management) Gravel Road Preconstruction Conference Asphalt Road A preconstruction conference between the Contractor’s Concrete Road representative on the project and the Project Engineer and his Types of Roads According to Traffic Volume staff is required. For heavy traffic load A discussion of the project, specifications, unusual conditions, For medium traffic load Contractor’s plan and schedule of operation, and other pertinent For light traffic load items is conducive to better job understanding. All such facilities must be approved by the Administration. Main Road Components Any controversy between the Contractor and the Project Subgrade Engineer that cannot be resolved at the field level, in Aggregate sub-base course accordance with the controlling Contract Documents and Aggregate base course established policies, should be referred to the District Engineer Surface course in written form. Drainage structures All important instructions from the Project Engineer to the Slope protection/retaining structures Contractor must be either given in writing or confirmed in Miscellaneous Works writing. These instructions will be made part of the official project file. Preliminary Preparations Maintenance of Traffic Before beginning work on any contract, the Project Engineer -The Contract normally, will include a TCP developed by the should make certain that all of the following items applicable Contractor. to the contract are on site. -When implemented, this plan (TCP) assures the safety or Complete contract drawings, including any revisions that motorists, pedestrians, and construction workers during the have been authorized. highway construction project. Cross-sections. -It must be submitted to the District Engineer at least 20 days Standard Specifications, Supplemental Specifications, before starting any work that will affect vehicular or pedestrian and Invitation for Bids traffic who must approve the Contractor’s TCP in writing Reference materials. before it can be implemented. Right-of-Way plans, options, entry agreements, entry -The Contractor shall assign to the project an employee rights obtained under the immediate possession law, and experienced in all aspects of traffic control that will serve as a record of properties under condemnation. Traffic Manager (TM) whose name and emergency home Plans for adjustments to, or relocations of, any utilities telephone number must be submitted to the Project Engineer that may be affected. for approval 10 days before starting any work on the project Notice to Proceed. and they should be displayed in plain view in the field office Material test equipment. window. Material test reports and approved sources of supply. -Significant changes to the TCP, as required by field conditions, Sketchbook, report forms, office supplies and field books. will be submitted by either the TM or the Project Engineer or Surveying notes and equipment. both to the District Engineer for approval before they are put Pertinent correspondence. into practice. -The Inspector is responsible to monitor the Contractor’s As - Stake Survey surveillance and maintenance of traffic control devices and -Determines the actual position of the road structure based on safety through the work area. the plans -The lump sum price for the item, Maintenance of Traffic, -Helps in determining what necessary deviation should be covers the cost of providing for safe passage of traffic over Undertaken temporary construction as well as through the area of the Plans That Govern an Infrastructure Project construction work or around it on detour roads. Original Plans As-Stake Plans As-Built Plans III. ROAD BASE PREPARATION ❖ Clearing and grubbing Temporary Facilities and Equipment -It means removing and disposing all surface objects including Client's Side: (Facilities for the Engineer) vegetation, trees and other protruding objects not Office, Quarters and Laboratory for the Engineer designated to remain along the roadway. Vehicle for the Engineer Assistance to the Engineer -It is necessary as a preliminary move in shaping the ground Progress photographs prior to the start of any excavation or placing of embankment Contractor’s Side: as any growth makes earth difficult to handle and its decay will Office cause future settlement of fill Equipment yard Fabrication Area/Shop Equipment and Labor Requirement Workmen’s quarters Removal of Trees Storage/warehouse Disposal of Debris Access and Detour Roads ❖ Removal of Existing Obstructions In planning the construction work, care must be taken Prior to actual construction work, obstructions are to see that alternative routes or temporary deviations removed in order not to hamper the work. are provided for traffic using the route. Access to properties along the road must be Typical Obstructions are: maintained at all times and the works must be barricaded where necessary to protect any passing Existing pavements traffic from accident. Existing drainage structures Detour Roads Underground waterline Becomes necessary to divert traffic from any existing Electrical post and lines roadway whenever the construction operations block Cable and telephone lines the flow of traffic. Residential houses and buildings Are to be planned and maintained so that they will Fences have sufficient durability to remain in good condition IV. FORMATION OF SUBGRADE and carry the required traffic at any weather condition Subgrade - is the upper layer of natural soil which may be for the entire period that the detour is the undisturbed local materials or soil excavated elsewhere required. placed as fill. Access Roads In forming the road subgrade, excess suitable material A road by which a job is connected to the highway located along the upper part of the designed road profile is system and is generally used in connection with excavated and taken as fill to low lying areas along the road borrow pits. traverse. Are also built for each isolated piece of job it services.  Roads in rolling hills are often engineered to balance the Unsuitable excavation - is the removal and disposal of cuts and fills so that all the material cut out in high spots is saturated or unsaturated mixtures of soils and organic matter just enough to build up all the low spots. not suitable for foundation materials. If the material is not enough, borrow materials are quarried Rock excavation - consists of igneous, sedimentary and and taken along as fill in order to obtain the design metamorphic rocks which cannot be excavated without blasting elevation of the subgrade along the road project. or the use of rippers. The two components in forming the subgrade therefore are: Unclassified excavation - excavation and disposal of materials regardless of its nature which were not classified and included -Roadway excavation in the bill of quantities under other pay items. -Embankment fill Surplus excavation - are suitable materials excavated along Earthwork Terminology: the road traverse which are disposed as excess in the formation of embankment subgrade. Embankment–earth fill below the pavement necessary to raise the road above flood levels. EMBANKMENT FILL Borrow- suitable material from sources outside the -Are suitable materials which can be common or rock which are roadway prism, used for embankments. brought and compacted together to a specified degree to form a stable embankment to bring the road to a desired grade or to Slope-the angle of constructed soil plane usually elevate it above flood level expressed in proportion of length and depth. The most desirable fill is a mixture of two or more simple type Fill-the average depth of embankment material needed and varying proportion of clay, silt, sand, gravel and stones. to be placed on top of the natural ground at any Sand and gravel are most desirable as embankment designated location along the roadway to satisfy the fill when mixed with enough clay or silt to bind them together. designed grade. Quarrying and Hauling Cut–the average depth needed in excavating the natural found at a specific location along the road Fill may be obtained by quarrying with bulldozer from borrow traverse to satisfy the designed grade. pits opened just to obtain the fill and loading/hauling same using a loader and dump trucks. Excavation–removing earth from its original position in a cut and transporting it to a fill or to waste deposit. Spreading of Embankment Compaction – the pressing of soil particles to expel air A stable embankment is attained by spreading the materials into from the mass and filling the voids to make the a thin layer then compacted at moisture content close to material moredense. The factors influencing amount optimum. of compaction obtainable are material gradation, soil Compaction shape, moisture content and amount of compactive effort. Compaction trial of not less than 500 sq.m. is done to determine the actual capability of the compaction equipment Soil Stabilization- a tool for economic road building, and the compatibility of the material to be used. material conservation, investment protection and roadway upgrading. The number of passes for the compaction equipment to attain the specified degree of compaction is recorded for use as Selected Borrow - suitable native material obtained reference in the subsequent layering works using the same from roadway cuts or borrow areas or other similar material and compaction equipment. material used for subbase, roadbed material, shoulder surfacing slope cover or other specific purposes. FDT is Field Density Test - which is conducted on site in order to determine if the required compaction specification has been Leveling Course - The layer of material placed on an attained to a specific layer. existing surface to eliminate irregularities prior to placing an overlaying course. Road Widening - Required degree of compaction in road widening is attained by benching the material for the heavy ROADWAY EXCAVATION equipment to gain access -It is the process of loosening and removing earth from its Blue Tops - are painted sticks placed along the side of the road original position and transporting same for fill or to a waste traverse as guide and reference in the elevation of the different deposit. layering requirements of the road project -Excavation operation should be conducted so that material V. STABILIZING LAYERS outside the limits of slope will not be disturbed. Types of Roadway Excavation Common excavation -involves excavation of common materials used as embankment fill which results from Subbase course - is a structural layer which accepts greater excavation along the road traverse. compressive stress than the subgrade and thus reduces the deformation of the pavement under traffic loading. Base course - reduces the vertical compressive stress induced Contraction Joint - Also called weakened-plane by traffic in the subbase course and the subgrade. joint. Are provided to relieve the tensile stresses due to temperature, moisture, and friction, thereby In Asphalt Pavements….. controlling cracking. If not installed, random cracking -the base and subbase courses serve to provide would occur on the surface of the pavement. structural capacity to bituminous concrete slabs. -they carry the load and distribute it to the soil under the Longitudinal Joint - If the lanes are concreted layers of asphalt concrete. separately, a longitudinal construction joints in the In PCC Pavements…. form of a key and keyway is used. Deformed steel tie -the subbase and base courses spreads the load over the bars of specified length, size and spacing are placed foundation. perpendicular to this joint. - the base course prevents pavement pumping and provides drainage for PCCP slabs. The spacing between longitudinal joints is dictated by What Other Purpose of Putting These Layers Below the the pavement thickness. Surface Course? Expansion Joint - Provide space for the expansion of Aside from being stabilizing layers, it also serve for draining the pavement, thereby preventing the development of purposes compressive stresses which can cause the pavement to What Is the Difference Between the Two Stabilizing buckle. Layers? Are usually from 19 to 25 mm wide and extend the -Material Requirement (Grading, CBR, Plastic Limit full depth of the slab. Liquid Limit) The joint space is filled with expansion joint fillers. -Balance of Mechanics and Economy Stockpile Along the Roadway Side Dowel bars are normally used in expansion joints, and Spreading their diameter, spacing, and length would generally be The subbase/base materials shall be spread to the required similar to that indicated for contraction joints. thickness for compaction. If the required thickness is 150 mm or less, the material may be spread and compacted in Types of Re-bar Used in PCCP Joints one layer. Dowels - Are load transfer devices in joints to transfer wheel loads from one slab to another and thus, prevent Compaction Each layer shall be compacted to the full width. excessive deflection at the ends of the slabs. Required degree of compaction is 100% Are plain round steel bars generally coated with a thin VI. CONCRETE PAVEMENTS file of bitumen to protect them against corrosion and -Portland Cement Concrete Pavement (PCCP) to facilitate sliding in concrete. -Asphalt Concrete Pavement Their installation midway in the slab should be carried Purpose of Concrete Pavement out accurately so as to have the dowels run parallel to the surface of the pavement and the center line of the Being the uppermost component of the roadway, it road. should provide long lasting, smooth, clean surface Tie bars - Are deformed bars used in construction and and should spread the load sufficiently so that the base longitudinal joints together with keys to tie two slabs material can support them. together. It protects the base against damage by traffic and Like the dowels, its installation must be midway in the weather. slab so that it runs parallel to the surface or centerline of the pavement. PCCP Terminology Methodology Workability - concrete ability to be placed in a Setting of forms prepared form without honeycomb. Batching of concrete Consistency - measure of fluidity of concrete. Concrete pouring Water-cement ratio – describes the compressive Use of concrete vibrator strength of concrete mix. Screeding Admixture - are substances other than aggregates Concrete finishing water and Portland cement that can be added to Concrete curing concrete to improve its properties and fulfill other Removal of forms and concrete cutting special purposes. Pavement protection Curing agent - is the treatment or protection applied to Sealing of joints concrete during hardening period to protect against Setting of Forms early shrinkage due to lose of moisture or abrupt -Forms should be made of steel of an approved section and changes in temperature. depth equal to the thickness of pavement. Types of Joint in PCCP -The base of the forms should be of sufficient width to provide Construction Joint - Also called cold joint. Is necessary stability in all directions. constructed when there is an interruption of more -It should be installed firmly in contact with foundation w/ than 30 minutes in the concreting operation which is no deviation from true lines by more than one (1) cm. placed not within 1.50 m. of an expansion joint or -The alignment and grade elevations of forms should be contraction joint checked prior to placing of concrete. Batching of Concrete Against Rain- To protect newly poured concrete pavements For large jobs, a Concrete Batching Plant is necessary to against rain it is required to have available at all times provide a smooth flow of continues supply and transport of materials for protection or covering materials such as burlap or materials to the work. cotton mats, curing paper or plastic sheeting materials. Periodic calibration of the plant is needed to ensure that only the approved concrete mix is used for the project. Against Traffic- To protect concrete pavement at its early age, Concrete Pouring it should be protected from passing traffic. This includes the -Concrete unloaded from truck mixers in a movable chute for posting of watchman to direct traffic and the posting and proper distribution into the prepared forms. maintenance of warning signs, lights, pavement bridges and -Workers are not allowed to walk on the freshly mixed concrete crossovers, etc. with boots or shoes coated with earth or foreign substances. Sealing of Joints -Placing should be continuous and necessary hand spreading should be done using shovels not rakes. Sealing of joints should be undertaken after the curing period Use of Concrete Vibrator and before the pavement is opened to traffic. -Concrete should be thoroughly consolidated along the faces of Each joint should be clean and dry when the seal is applied. all forms by means of vibrators inserted into concrete. Spilling of seal on the surface of the pavement is not allowed. - Vibrators are not allowed to be operated longer than 15 seconds in any single location. Asphalt Concrete Pavement Continued…. Screeding Prime Coat - Is an application of thin bituminous material to a A screeder is used to grade concrete in such manner as to porous base before putting on a surface course. prevent segregation. -It serves to stabilize the base and bind it to the paving The screed is moved forward on top of the forms with combined material. longitudinal and transversal shearing motion. -It also serves to plug the capillary voids in the pavement in Concrete Finishing order to stop the upward movement of moisture and to improve Floating- after the concrete has been struck off and the adhesion between the base and the surface course. Tack Coat - It ensure the adhesion of the surface consolidated it is further smoothened by means of a course to the binder course. longitudinal float. Any excess water or soupy material is wasted over the side forms on each pass Before applying tack coat, the surface must be swept or flushed. The rate of application of either the rapid curing cutback or the Brooming - is executed by producing a uniform appearance emulsified asphalt is within the range of 0.2 to 0.7 liter per of corrugations produced in the surface not more than 1.5 mm. sq.m. in depth. The tack coat is sprayed in advance on the surface course to permit it to dry into a tacky condition. Concrete Curing Is necessary for the hydration to take place so that the Binder Course - It is a bituminous layer below the surface or concrete may harden properly and prevent abrupt loss wearing course. of moisture during the curing period. -The mix is designed primarily for stability as it is not Curing Methods exposed to weather and traffic. -Its aggregates are almost always larger than that of the Earth or straw may be spread over the surface of the wearing course. pavement and kept constantly wet during the curing Wearing Course – period. -It is the climax of the whole operation. Burlap or cotton mats are spread over the surface. The -The only part apparent to those who use the highway. -It should be smooth yet skid resistant, quiet, in contact with mats are sprinkled and kept constantly wet. tires, cohesive and durable enough to resist traffic stresses and Waterproof paper or polytelene sheets may be placed sufficiently impermeable to water and air to resist weathering. over the slab to retain the moisture. Curing compound - the most popular method which VII. DRAINAGE STRUCTURES involves the spray application of light-colored fluid to -Are installed beneath or alongside the roadway for collecting, the entire area of the wet concrete. The fluid forms a transporting and disposing surface water originating in or near film over the pavement that prevents moisture loss. the road right-of-way. Removal of Forms and Concrete Cutting Forms for concrete shall remain in place undisturbed within -A well located, properly bedded, accurately assembled and 24 hours after pouring. carefully backfilled drainage structure will function properly and efficiently for a long period of time. Crowbars are used in removing forms pulling out of nails and Culvert Excavation pins but cares should be exercised not to break the pavement edges. A bachhoe is suitable for this type of work especially if it is a Concrete sawing is done within 24 hours after concrete pipe culvert or a segmental type box culvert as it can be utilized pouring water using cooled diamond edge saw blade for drainage excavation as well as in the lifting of each culvert Weakened Plane Joint Using a Template segment during installation.. An alternative to concrete sawing is the use of a thin When excavating is done by hand method, lines should be steel template strung to limit the boundaries of the excavation and at least one string set parallel to the grade line to assist in maintaining the Pavement Protection lines and grades. The trench or streambed must be shaped to fit the bottom of the After backfilling, pipe culverts are protected by providing extra culvert. fill as cover before any heavy equipment is permitted to cross during the construction of the roadway to protect the job from Foundation Fill possible damage by excessive loads. If the underlying soil at the designed bottom grade of the VIII. Slope Protection/Retaining Structures culvert is composed of unsuitable material, it should be -are constructed along the side of the road as protection removed and substituted with granular fill composed of sand or from erosion or if there are space constrictions. sandy soil. This foundation fill is meant to stabilize the foundation bed to Some of the Types of Slope Protection Structures Are: avoid any possible settlement that might impair the function of the drainage structure and also to serve as a uniform cushion to Grouted Riprap, Stone Masonry the culvert. Gabions, Plain or Reinforced Concrete Its normal thickness of 20 cm. may be spread manually using Grouted Riprap rakes and shovel until the whole foundation bed is covered, as required. Excavation of Foundation- A backhoe is an ideal equipment -For box culverts, the layers are of uniform flat thickness. to use in the excavation of foundation for grouted riprap. -For circular pipes, the bedding is shaped so that the bottom of the pipe will be in contact throughout its full length. Use of Batterboards As Guide -Compaction can be done with hand or mechanical equipment -Good workmanship requires a reliable reference to guide the carefully done to ensure a thoroughly tamped foundation fill. work up to completion. -The unevenness of the embankment slopes is then trimmed R.C. Box Culvert Construction Phases using shovels and rakes. Culvert base The high areas are removed and patched and compacted Side and inner walls Laying of Boulders and Grout Culvert slab -Boulders and grout are placed layer by layer alternately. Methodology -Each stone is laid with its longest axis perpendicular to the Installation of Side Walls slope in close contact with the adjacent stone. Installation of Forms -The riprap is thoroughly rammed into place and the finished Installation of Rebars stone are laid to an even tight surface. -Spaces between stones are filed with cement mortar Concreting/Screeding sufficient enough to fill completely all the voids. Finishing Finishing Work Cement grout is placed starting from the bottom to the top of Installation of RC Box Culvert the surface and then swept with a stiff broom. Installation of Pipe After grouting, the surface is cured for a period of at least 3 Collaring of RC Pipes days from the date of installation. Backfilling Measurement of Thickness Installation of RC Pipes Importance of Weep Holes Pipes are installed in the original streambed with their grades Weep holes- are opening provided to permit draining and flow line conforming to the natural channel or canal. of water in filter layer or soil layer from behind the structure. If no or insufficient weep holes are installed, this will Laying begins at downstream end of the culvert line to use cause oversaturation of the embankment and the subsequent gravity in properly installing the pipes. failure of the road structure. Groove ends are placed such that the pipe ends fit at its nearest ends. Stone Masonry Specifications Lower segment of each pipe should be in contact with the shape Boulders - thickness of not less than 150 mm, and of the bedding throughout its full length. widths of not less than one and one-half times their Collaring of RC Pipes respective thickness, and lengths of not less than one and one-half times their respective widths. Mortar proportion is 1:2 with enough water to obtain the desired consistency. Mortar - composed of one part of Portland Cement and two parts of fine aggregate by volume and The collar is to form a continuous bead around the outside of sufficient water to make the mortar such consistency the pipe. that it can be handled easily and spread with a trowel. The inside of pipe is finished smooth. Excavating Stone Masonry Foundation Backfilling The foundation bed where the masonry is to be placed should be firm and normal to the face of the wall. Backfill are placed and compacted in layers not exceeding 15 cm. on both sides up to an elevation of 30 cm above the top of The bed that will receive the stone should be clean and the culvert. moistened before the mortar is spread. Spreading maybe done manually using rakes and shovels at a Use of Batter boards Essential to Produce Good thin layer which is most ideal to produce easy compaction of Workmanship material done using hand tampers to insure a thoroughly tamped backfill. As in grouted riprap, batter boards are necessary to keep the Post may be concrete, steel or aluminum lines and grades of the finished stone masonry structure in accordance to the lines and grades of the plans. Installation Specifications Laying of Boulders and Grout Location lay-out Large stones are used in the corners. Post installation Bunching of small stones of the same size is not Beam assembly allowed. Backfilling of drilled/dug holes Stones are laid with their longest face horizontal in full Location lay-out beds of mortar. Joints are flushed with mortar. The proper location of guardrail is as shown in the The exposed face of the individual stone should be plans. parallel to the face of the wall in which stones are set. But most often, its location is left to the discretion of The stones are handled carefully so as not to jar or the Engineer. displace the stones already set. In general, the rail should be located near the shoulder Finishing Works line to give a maximum width of roadway and Immediately after laying and while the mortar is still shoulder. fresh, all face should be thoroughly cleaned of mortar However, the distance forms the back of the post line stains and should be kept clean until the work is to the slope should to be less than 0.6 meter in order completed. to give adequate support against overturning. Gabion Mattress Post Installation Wire mesh in varying thickness and width which Spacing of posts should be done with accuracy and is filled with boulders in placed to form a slope care. protection structure. Holes are pre-drilled depending on the kind of soil or Boulders should be hard and durable rock pieces that presence of rock or boulders. will not deteriorate when submerged in water or Appropriate drilling equipment or hand tools should exposed to severe weather conditions. be adequate to handle any condition encountered. Boulder size should be uniformly graded generally Beam Assembly ranging from 10 to 20 cm. Assembly begins at the end farthest from approaching Filled gabions should have a minimum density of traffic placing one panel of the rail at a time on the 1,400 kg/cum and voids distributed evenly. posts. Installation Procedure Without putting the nut on the long bolt on the post Only simple tools are needed to assemble this wire until the next panel is in place, the two corrugation basket such as long nosed fencing pliers and crowbars. crests is placed always towards traffic. Before closing of lids, gabions mattress should be Then the short splice bolts are inserted and the nuts overfilled by about 25mm to allow for settlement. left loose. Tightening of all bolts is done during the The lids are then stretched over the stone fill and laced final aligning process. down. The end piece is installed just like any other panel and Corners are secured first to make sure the lid can be always with the end flared back. laced down without overstretching the mesh. The lap at all posts should be such that a vehicle does The lids are then laced down securely. not strike the end of the metal. IX. MISCELLANEOUS STRUCTURE/WORKS For curved installation, flex-beam guardrail may be Curb and Gutter obtained shop curved to any desired radius 6 meters or It is the raised rim of concrete which forms the edge greater. of the sidewalk while the gutter is the horizontal paved Backfilling of Drilled/Dug Holes portion slightly inclined. Backfilling of dug or drilled holes should not be Both forms the road surface drainage system used to completed until the rail is in place and lined up. collect surface run-off water. Backfill should consist of dry earth or granular Concrete Sidewalk material well tamped. Posts need not be set in concrete unless unusually soft It is for use of pedestrians materials require it. It provides safety also to motorists as a good clearance so that the roadway can be fully utilized. Concrete Parapet Wall….. It must be wide enough and skid resistant -An economical alternative road protection. Types of Sidewalk Concrete paved Road Signs Asphalt paved Are traffic signs installed along the roadway Guardrails for the following purposes : They are installed to mark the limit of safe travel and For traffic safety warn of danger beyond. To remind particular traffic rules It is used to restrain and guide out-of-control vehicle To inform drivers how to use the roadway in a manner that will cause the least damage and not Types of Road Signs create undue hazard to other vehicles. Warning sign Material Req’s Regulatory sign Standard beam type are either galvanized or Informatory sign aluminum