Soil investigation is always a good way to start before proceeding on a project. Analysis of the soil will identify the structural integrity of ground. This will give the designer a clear picture upon which they may select a design that insures pavement failure does not occur.
A full depth repair involves removing all the blacktop in a given area down to the gravel sub base. The new pavement is then replaced generally in two lifts of asphalt – a coarser base coat and a finer top coat.
Milling involves removing an asphalt surface, usually a roadway or parking lot with very large machinery. The machinery literally grinds the pavement into a fine aggregate that can be added back to new hot mix asphalt.
LEED stands for Leadership in Energy and Environmentally Friendly Design. It is a way of rating a design’s “green qualities” and insuring that a project is incorporating favorable qualities that reduce energy consumption and minimize harm to the environment.
Porous pavement is a material that is processed devoid of fine aggregates (stone dust and/or sand) that allows water to run directly through to the surface below. Porous pavement has several environmentally friendly qualities and is being used increasing in new construction designs.
RAP stands for Recycled Asphalt Pavement. This is usually produced from a milling operation that grinds the surface in to a fine aggregate product.
While there are many good types of sub base generally the best have a higher content of crushed stone. This said it is the native soil upon which the design is to be constructed that determines the usability of a particular sub base. Sandy gravel may be perfectly fine in dry soils but not acceptable in moist clay soils.
In the 1980s, many state transportation departments were experiencing widespread premature deterioration of asphalt pavements. To address this problem the Strategic Highway Research Program (SHRP) undertook a program of asphalt research that eventually led to a new asphalt mixture design and analysis system called Super pave. Super pave stands for Superior Performing Asphalt Pavements.
The Super pave system includes a performance-based asphalt binder specification, a mix design analysis system, many new test procedures, and new equipment. The Strategic Highway Research Program was established by Congress in 1987 as a five(5) year, $150-million research program to improve the performance and durability of our highway system.
In 1991, Congress authorized The Federal Highway Administration (FHWA) to initiate full-scale implementation of Superpave and other SHRP research results. This process began in 1993 when SHRP delivered its final research findings. States, FHWA, and industry all took advantage of techniques such as state pooled-fund equipment buys, expert task groups, mobile laboratories, user-producer group, the American Association of State Highway and Transportation Officials (AASHTO) Lead States Program, and Super pave Centers to implement the research results.
Super pave is a comprehensive system for the design of paving mixes that are tailored to the unique performance requirements dictated by the traffic, environment (climate), and structural section at a pavement site. It enhances pavement performance through the selection and combination of the most suitable asphalt binder and aggregate.
Super pave represents the integration of several products of the SHRP asphalt research program into a single system for the design and analysis of paving mixes. It encompasses new material specifications, test methods, equipment, software, and mixture design method.
Catch basin collect surface water runoff and direct that water to storm drains and retention basins where the water may recharge back in to the earth.
Usually under drain is required when the soils upon which the lot is built are not stable enough to support the traffic loads. Especially susceptible are clay soils that can retain moisture. and then heavy during the freeze/thaw cycles.
Construction workers make up only 6 percent of the total workforce, but they are involved in more than 20 percent of all work-related fatalities. Trenching accidents directly related to excavation work account for almost 200 deaths annually. Construction workers are buried, and they die from suffocation. It is almost impossible to escape once a cave-in occurs because soil weighs about 100 pounds per cubic foot.
Investigations indicate that improper planning, failure to recognize potential safety problems, and/or the lack of a formal excavation plan are the primary accident causes. Unsafe placement of spoil pile, operating equipment too close to the edge of a trench, improper shoring, failure to provide safe access and egress to the work area, and lack of adequate emergency rescue equipment are major contributing factors. In many cases, workers are not aware of the hazard potential or are not properly trained to identify safety issues.
- Protect Yourself
Do not enter an unprotected trench! Trenches 5 feet (1.5 meters) deep or greater require a protective system unless the excavation is made entirely in stable rock. Trenches 20 feet (6.1 meters) deep or greater require that the protective system be designed by a registered professional engineer or be based on tabulated data prepared and/ or approved by a registered professional engineer.
- Protective Systems
There are different types of protective systems. Sloping involves cutting back the trench wall at an angle inclined away from the excavation. Shoring requires installing aluminum hydraulic or other types of supports to prevent soil movement and cave-ins. Shielding protects workers by using trench boxes or other types of supports to prevent soil cave-ins. Designing a protective system can be complex because you must consider many factors: soil classification, depth of cut, water content of soil, changes due to weather or climate, surcharge loads (for example: spoil, other materials to be used in the trench) and other operations in the vicinity.
- Access and Egress
OSHA requires safe access and egress to all excavations, including ladders, steps, ramps, or other safe means of exit for employees working in trench excavations 4 feet (1.22 meters) or deeper. These devices must be located within 25 feet (7.6 meters) of all workers.
Work inside open trenches is seldom regarded as work in a confined space until emergency escape is necessary. Potential safety hazards must be more readily recognized before work begins, and all workers must know the precautions needed to prevent accidents.