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Drainability

Posted by on 13/ 11/ 15

Broadly graded aggregates, as typically used in granular base and sub-base layers of the road construction have relatively small pores as the large pores between the coarser particles are mostly filled with smaller particles. This means that coefficient of permeability values, as characterised by the Darcy coefficient, K, are relatively low. Laboratory testing of typical sub-base aggregates has revealed hydraulic con­ductivity values that are usually less than 10-3 m/s in the unlikely even of saturation (Jones and Jones, 1989) and as low as an effective value of 10-6 m/s when, more normally, in a partially saturated state.

Подпись: Fig. 2.12 Typical moisture profile with height for a compacted column specimen with water provision at the base (adapted from Jessep, 1998)
Drainability

A second implication is that the pores will have a measurable suction ability...

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STEP4 Attach the Sills

Posted by on 13/ 11/ 15

Some important carpentry work is about to begin. Whether you are building on a concrete slab, over a crawl space, or over a full base­ment, the first wooden member that is laid down is called a sill, mudsill, or sole plate.

T his sill is commonly a pressure-treated 2×4 or 2×6 attached directly to the foundation with anchor bolts embedded in the concrete. Occasionally, it is attached with hardened concrete nails or steel pins shot through the sill and into the concrete by a powder – actuated nailer.

Подпись: SNAP CHALKLINES TO LAY OUT THE SILL. The line shows where the sill's inside edge rests. If the foundation isn't perfectly square, adjust the line's position so that the sills will be. [Photo by Roe A. Osborn, courtesy Fine Homebuilding magazine, The Taunton Press, Inc.] STEP4 Attach the SillsMost codes require that anchor bolts be located I ft. from each corner of the founda­tion, 1 ft. from the ends of each sill plate, and a maximum of 6 ft. o. c. everywhere else. These are minimum requirements. Builders living in earthquake or high-wind areas often use %-in.-dia...

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30-20-10 rule

Posted by on 13/ 11/ 15

The 30-20-10 rule suggests that proper stone-to-stone contact is created if the per­centages of aggregate passing sieves of 0.075 mm, 2.36 mm, and 4.75 mm equal 10%, 20%, and 30%, respectively, which should provide for the appropriate discontinuity in the gradation. After comparing this rule with the data of Table 6.4, one can see that the proportion of grains larger than 4.75 mm from this rule (70%, or 30% passing the

TABLE 6.4

Approximate Contents of Aggregate Fractions for Zichner’s Mastimac and Mastiphalt

Filler Fraction

sand Fraction

Aggregate

Aggregate

Aggregate

mixture

< 0.09 mm

0.09-2.0 mm

2/5.6 mm

5.6/8 mm

8/12.5 mm

MASTIMAC

12-13%

11-12%

15%

60%

—

(SMA 0/8) MASTIPHALT

12-13%

11-12%

10%

27%

38%

(SMA 0/12.5)

Source: Bas...

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How an MSDS Can Be a Useful Tool

Posted by on 13/ 11/ 15

Although the MSDS has shortcomings, it is still an important tool for people involved in construction. If you are not working with a physician/architect team knowledgeable about chemicals, the MSDS can be confusing to interpret. However, the MSDS may provide useful information when used in conjunc­tion with other tools. The National Institutes of Healths National Library of Medicine has developed a searchable database for a wide variety of household product information.5 The database can be searched by product, in­gredients, and MSDS. By comparing MSDS chemical lists with the information available through the library, it is possible to gain a bet­ter understanding of recognized potential hazards for the listed chemicals.

Certain rules of thumb can also be used to evaluate a chemical lis...

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Roof Flashing

Posted by on 13/ 11/ 15

Because underlayment directs water away from sheathing, it’s technically flashing, too. More often, however, roof flashing refers to sheet metal that protects building seams or edges from water penetration or diverts water around pipes, chim­neys, dormers, and so on. Metal flashing is widely used because it’s durable and relatively easy to cut and shape. Always replace old flashing when installing a new roof.

MATERIALS

Various sheet materials are suitable for flashing. Unformed, they come in sheets 10 ft. long or in rolls of varying lengths, widths, and gauges. Copper is the longest lasting and most expensive. Lead is the most malleable but is also the most vulnerable to tears and punctures...

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Establishing Access Control

Posted by on 13/ 11/ 15

Access control may be exercised and established by statute—through zoning ordinances, driveway controls, and turning and parking regulations—and by geometric design. Control by statute is used where full access control or a high degree of access control is required. Direct driveway connections may be prohibited, and at-grade intersections may be allowed only with major crossroads. This may be employed for a major urban arterial.

Zoning can control the type of property development adjacent to the roadway, and thereby influence the amount and type of traffic generated in the area. Property uses can be limited to those that attract very few people, excluding those that would generate significant volumes of traffic during hours of peak movement...

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ACCESS TO PUBLIC ROADS

Posted by on 13/ 11/ 15

2.9.1 Defining Access Control

Control of access is the condition where the right of owners or occupants of abutting land to access a highway is fully or partially controlled by public authority. Access control is usually defined by regulations of the authority having jurisdiction over the roadway. The purpose of establishing access control is to provide for the safe and expeditious movement of vehicles on the street or highway, while upgrading the level of service and safety to those living near and using the facility. Regulations may be categorized as full control of access, partial control of access, and driveway and approach regulations.

Full control of access is the means by which preference is given to through traffic by providing access connections only at selected public roads and b...

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Permeability in Unsaturated Soil

Posted by on 13/ 11/ 15

Water flow in unsaturated soils is primarily dependent on the volumetric water con­tent, matric suction and on the gravitational potential. Due to the presence of air within part of the pores, water movements are obstructed and flow is only achieved through the finer pores or in films around the soil particles. The permeability (or “hydraulic conductivity”) of unsaturated soils is, therefore, reduced compared with fully saturated soils due to the presence of air in the porous media. Usually the permeability of unsaturated soils is given as the water-relative permeability defined as the ratio of the permeability at a specific water content to its permeability under fully saturated conditions, thus:

K w (в)

krw (в) = – W (2.35)

K

where krw (в) is the water-relative permeability, Kw (в...

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UNDERLAYMENT

Posted by on 13/ 11/ 15

Once limited to building paper, underlayment now includes self-adhering rubberized sheets that replace metal flashing in some cases. Thus you can base your choice of underlayment on climate, composition, and position on the roof.

Weather-resistant underlayment. Traditionally, underlayment has been 36-in.-wide, 15-lb. or 30-lb. felt paper used as a weather-resistant layer with several purposes. It keeps sheathing dry till shingles are installed, serves as a backup layer when water gets under shingles or flashing, and separates sheathing and shingles and so prolongs shingle life. (Without underlayment, shingle asphalt can leech into wood sheathing, or resins in sheathing can degrade the shingle.) Heavy – duty, 30-lb...

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SERVICE ROADS

Posted by on 13/ 11/ 15

Service roads, or frontage roads, as they are sometimes called, are used to enhance capacity on the mainline, control access, serve adjacent properties, or maintain traffic circulation. They permit development of adjacent properties while preserving the through character of the mainline roadway. Service roads may be either one-way or two-way, depending on where they are located and the purpose they are intended to serve.

Although the alignment and profile of the mainline may have an influence, service roads are generally designed to meet specific criteria based on functional classification (usually “local”), traffic volumes, terrain or locale, and design speed. Two features, however, are unique to service roads and are further discussed below...

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