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A trench drain consists of drain wrapped in geotextile, see Figs. 13.13-13.15. The drain is made of a mineral material such as a rounded or crushed aggregate. Origi­nally either no carrier pipes orun-jointed pottery pipes were employed at the bottom of such drains. Nowadays, several materials are used for this type of pipe, from perforated […]

13.4.1 Lateral Drains In order to stop water getting into a pavement foundation and to avoid the con­sequent reduction of its support capability, the construction of ditches or trenches is a common procedure. They are usually filled with highly permeable material, wrapped in geotextile and with a perforated tube or porous material near the bottom. […]

From a pavement point of view, it is desirable to keep the aggregates in the pavement as dry as reasonably possible — so as to promote strength, stiffness and resistance to deterioration (see Chapters 8-10) — but the pervious pavement concept is directly in opposition to the general principle. Therefore other strategies have to be […]

The slow percolation of contaminated runoff into the pavement through a porous aggregate layer to an outlet substantially slows water movements, provides the possibility of filtration and allows water to pass by a large surface area of stone. By these means the water drops the suspended, fine, solids that it is carrying into the pore […]

Normally, rain falling on impermeable surfaces, such as a road surface, quickly enters the drainage system, arriving at the outfall to river or stream very soon after falling from the sky. It is estimated (Interpave, 2005) that in a fully forested, lowland catchment only 5% of rainfall will flow across the ground surface, the remainder […]

A book on Water in Road Structures would not be complete without a brief descrip­tion on the use of the pavement as a water store. Pervious pavements (see Chapter 5, Section 5.7) can be taken one step further and not only used to convey water away from the surface, but can also be used to […]

Aggregates and geotextiles employed in drainage systems have to operate next to soil or aggregate that surrounds them. To achieve good performance, they must re­main permeable, retain the surrounding ground or aggregate in place and not clog. These requirements are met by defining specific performance criteria. The first of these is the non-sedimentation criteria, which […]

Where there are environmentally sensitive areas or high traffic flows, increasing the risks of accidents and generating contamination from wear, water flowing over the surface of the road and the embankment should be collected before it can soak into the ground in an uncontrolled manner. Water seeping through the earthworks and collected by a drainage […]

It is a design objective that snowmelt and rainfall should have fast access to the side of the road and the drainage system. This avoids surface ice formation and skidding, but also protects the structure so that as little water as possible filters through to the pavement. Edges, kerbs, channels and runoff barriers must be […]

According to Huang (2003) the placement of a drainage layer directly under the asphalt or concrete pavement surface is preferable, because the water in the pavement, either percolating through cracks or entering from the sides, is quickly allowed to move to a lower level from where it can easily be drained. No pore pressures can […]