Unit PART 1 CONSTRUCTION OF ROADS AND BRIDGES ROAD/HIGHWAY CONSTRUCTION VOCABULARY BUILDING Highway Surveys In pairs, guess the meaning of the following terms Benchma rk Aggrega te A man standing at the benchmark point Soil boring sample Surveyors take soil boring sample using a drill rig or a hand auger cL 6’ Front cL’ Back 78+00 Right-of-way and centerline stakes F 60 Centerline Stakes cL 26.0 16.0 6.0 4.0 4.0 Front’ Marking and setting slope stakes C 40 260 cL 78+00 Slope stake Back 1:1 Marking and placement of slope stakes Red top (Grade stake) Blue top (Grade stake) In construction grade staking: - blue tops (2x2x6 to 12 inch stakes) mark the level of finish grade; - red tops (2x2x6 to 12 inch stakes) mark the level of subgrade; CL 1+00 0+00 CL Typical arrangement of various stakes on a road section (final grading) Match the terms with definitions  indicate required grade elevations to the construction  crews During the final grading stage of construction, hubs called “blue tops” are used in lieu of stakes Soil boring  samples Stone and gravel of various sizes which compose the major  portion of the surfacing material The sand or pebbles added to cement in making concrete Centerline stakes  are used to indicate the inside edge of the roadway  shoulders These stakes are set opposite each center-line stake Shoulder stakes  a fixed reference point that is used in the surveying process  to accurately measure elevations Slope stakes  mark the intersection offside slopes with the natural  ground surface They indicate the earthwork limits on each side of the center line Right-of-way stakes    are taken by drilling down into the ground to determine the  soil composition before or during construction   Benchmark Grade stakes Aggregate indicate the exact center of the roadway construction indicate the legal right of passage or corridor and outmost bounds of construction 2 READING a Have you ever visited a highway construction site? What can you see on a highway construction site? Highway Construction Procedures By Amanda Holden Two words can cause sighs of defeat and exasperation among travelers: road construction Yet, while road construction seems inconvenient and troublesome, in truth it benefits the public By building and repairing roadways, people may travel long distances with relative ease, a feat that would become near impossible without passable roads Road construction in the U.S follows a standard set of procedures for longevity and usability of the future roadway b Read the text and order the paragraphs 1-6 A Levelling and Paving Workers place blue stakes every 10-20 meters and begin to level the ground to meet the pre-mapped elevation benchmarks With the "blue tops" on the surface, contractors perform a final touch to the earth or dirt road Then workers begin to lay an aggregate, or a rocky, densely-packed substance, to the levelled ground as a base, followed later by asphalt and other surface dressing materials B Ground Assessment Once the surveyors have completed mapping the area, they must next assess the ground for road suitability Workers take soil samples from boreholes using a drill rig or hand auger, with a minimum of 15 samples (borings) every kilometer These samples stretch out to 30 meters on either side of the new highway and once analyzed, lead to a classification of the area's soil profile Swamps, lakes, rivers and other wetlands require more surveys and assessments, not only to determine the ecological impact of a new roadway but also to determine suitability C Maintenance Over time, the new road will experience damage due to weather and use Chips will develop in the pavement from freezing water, encroaching plants, snow chains and more Sometimes existing roadways need expansion to handle an increasing amount of traffic Roads undergo repaving, repainting and more to stay in operation D Mapping and Surveying Before construction ever begins, extensive mapping and topographic survey takes place Surveyors map the entire area to pinpoint where the new road will sit Once complete, adjacent homes are mapped and if necessary, bought out through the government's right of eminent domain, which occurs if the property falls within the new road's right-of-way Surveyors note the topography of the surrounding area, such as mountains, streams and lakes, and place the new road accordingly Benchmarks are mapped every 250-300 meters for the entire length, referencing elevation in comparison to sea level and signifying the future preferred elevation of the road E Finishing Touches Workers apply paint to the finished road and begin work on slopes and ditch bottoms to try and prevent erosion They place stakes for various erosion control materials, such as straw and rock Workers apply paint to the new road to guide the users and identify traveledway lanes Final measurements will determine the quality of the road construction job, as well as whether the road meets legally-required standards These factors play into the contractor's final pay F Earthwork Once the government has completed all the mapping, property acquisition and soil studies, actual groundwork can begin Workers place survey posts every 25-30 meters on the new road's centerline and at the right of way limits and removal of trees and bush begins After workers have cleared the trees and bush, they place construction stakes on the centerline, slope stakes, stakes for culverts, storm drains and curbs c Put the following words into the six correct categories above mapping survey alignment survey topography paving construction stakes erosion control painting soil benchmarks corners repaving cross sections property swamp soundings right of way acquisition repainting tree and bush removal centerline reestablishment Mapping and Surveying Mapping survey d Read again and answer the questions What surveyors before construction begins? How far is it between two benchmarks? How many soil samples are taken every kilometer? Why wetlands require more surveys and assessments? What workers after tree and bush removal? PAVING When constructorsASPHALT perform the final touch to the INSPECTION dirt road? Compaction What the workers before paving asphalt? - Compaction makes the pavement dense - Rolling must achieve the desired (1) , smoothness and surface texture - 3dophases in rolling: Breakdown, intermediate, (2) Why the roads require maintenance? - Typical arrangement of vehicles: LISTENING + Steel wheel vibratory roller in breakdown + Pneumatic roller in (3) Watch a video about Pavingrolling Inspection and complete the + Static rollerAsphalt in final/finish following note tips Inspecting - Watch each roller at (4) direction - Rollers should process in a (5) _line - Rollers should work at (6) speed - On super-elevation, rolling should start at (7) _ side - Longitude (8) _ should always roll first What workers in the finishing touches? SPEAKING In groups of four, discuss the characteristics of asphalt pavement and PCC (Portland Cement Concrete) pavement using comparative adjectives Students A: List advantages of Asphalt Pavement over PCC Pavement Students B: List advantages of PCC Pavement over Asphalt Pavement Characteristics of Asphalt Pavement and PCC Pavement (Source: Guidelines on Expressways in Japan – Kosoku Doro Chosaika) Items Asphalt Concrete Pavement PCC Pavement Design Period 10 years Resistance to Deformation and Abrasion Less resistant against Deformation such as rutting is deformation, causing rutting hardly observed Noise Vibration 20 years Less resistant to abrasive Highly resistant to abrasion in forces generated with studded general tires and Less noise and vibration Vibration caused at joints, and noise due to harsh or rough texture are sometimes problems Brightness Surface of Reflectance of the surface is Lighter after dark or inside lower than PCC, which causes tunnels difficulty in driving through tunnels Evenness Surface of Normally better than PCC Restrictive Conditions in Construction Fewer restrictive conditions during construction work, and production rate is normally higher Large number of construction equipment items, which inevitably tends to produce restriction as below Production rate is also lower - Subgrade preparation should be successively done - Structures like bridges and culverts should be fewer in number Pavement usually provided with asphalt wearing course Maintenance and Rehabilitation Possible and easy with simple Comparatively large scale methods methods should be employed, so that PCC on soft ground should be avoided Cost Analysis Initial cost is cheaper, but Initial cost frequent repair is required and Reconstruction total cost over 20 years or so is expensive sometimes higher is is higher more [...]... over Asphalt Pavement Characteristics of Asphalt Pavement and PCC Pavement (Source: Guidelines on Expressways in Japan – Kosoku Doro Chosaika) Items Asphalt Concrete Pavement PCC Pavement Design Period 10 years Resistance to Deformation and Abrasion Less resistant against Deformation such as rutting is deformation, causing rutting hardly observed Noise Vibration 20 years Less resistant to abrasive Highly