Blog Archives

Drainage Layers

Posted by on 24/ 11/ 15

13.3.6.1 Drainage Layers in the Pavement

The sub-surface drainage system often includes a (permeable) drainage layer in the pavement. Its function is to quickly remove water entering the pavement layers, either through infiltration to the groundwater or to a sub-surface drainage system, before any damage to the road can be initiated. It is common practice to include drainage layers where the groundwater level is high compared to the location of the road, where the subgrade soil has low permeability and on high class roads (Summary of replies to the WATMOVE questionnaire, www. watmove. org).

There are situations where a drainage layer is not considered necessary...

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Other projects of the early Han

Posted by on 24/ 11/ 15

Other canals are constructed in the north in 113 BC. The purpose was to try to bring the region of the grand loop of the Yellow River into cultivation, and thus to settle this area that had served as an ideal corridor for the invasions of the Xiongnu barbarians.[412] These irrigation canals are built on either side of the Yellow River in the region of the present – day Yinchuan. Their construction had in fact been begun around 215 BC under the reign of the first emperor, and saw further new development under the Ming. In the end, they attained a length of about 180 km.

Between 38 and 34 BC a dam-reservoir called the Maren dam was built near the city of Nanyang on one of the principle north tributaries of the Han river. The project is attributed to Zhao Xincheng, who was prefect of Yanyang...

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Reliability design with redundancy

Posted by on 24/ 11/ 15

Consider the design of a hydrosystem consisting of n subsystems that are ar­ranged in series so that the failure of one subsystem will cause the failure of the entire system. In this case, reliability of the hydrosystem can be improved by installing standby units in each subsystem (see Fig. 8.7). Figure 8.7 consists of a series-parallel configuration that is called unit redundancy. Suppose that each subsystem can install up to K standby units and that the total capital available for the hydrosystem is C. Furthermore, the cost functions are known, with Ci (ki) being the cost associated with installing ki standby units on the ith subsystem.

Suppose that the engineer is interested in determining the number ofstandby units for each subsystem to maximize the system reliability asys without

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Structure Dimensions and External Stability

Posted by on 24/ 11/ 15

Flexible cantilevered walls should be dimensioned to ensure stability against passive fail­ure of embedded vertical elements using a factor of safety of 1.5 based on unfactored loads. Vertical elements must be designed to support the full design earth, surcharge, and water pressures between the elements. In determining the depth of embedment to mobi­lize passive resistance, consideration should be given to planes of weakness (such as “slickensides,” bedding planes, and joint sets) that could reduce the strength of the soil or rock from that determined by field or laboratory tests...

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Renting a Paint Sprayer

Posted by on 24/ 11/ 15

Don’t rent spraying equipment that isn’t well maintained. A first-rate rental company will size the pump to your job, recommend spray tips, and explain how everything works. For good measure, ask for an operator’s manual, too.

Finally, get satisfactory answers to these questions: (1) Is the equipment clean? Rental companies charge extra if equipment is returned uncleaned. (2) Was the last paint used in the sprayer oil-based paint or latex? (3) Can you show me how to use this model?

The last question is especially helpful if you’re a bit macho and don’t want to admit that you’ve never operated any sprayer before. Another face-saver is, "Say, run a little water and show me how to pressurize this, would you?" Don’t leave the rental yard without understanding how the equipment works.

Подпись: Amateurs mistakenly paint from a 1-gal. paint can instead of a painter's pail. Consequently, they dip into too much paint, which they then scrape off on the can lip. Better to dip into less paint and with two flicks of the wrist, Dip-tap-tap the brush on both sides of a pail. This removes excess paint that might drip, but leaves most of the paint on the brush, letting you paint farther.Подпись: 1111Подпись: PAINT FUMES AND OPEN FLAME: AN Explosive COMBINATION Volatile paint fumes build up quickly, especially during spray painting. Minimize the risk of explosion by choosing latex paint, increasing ventilation, and using electric heaters to maintain a 60°F drying temperature. (Forced hot-air systems will kick up dust.) Open-flame heaters are not acceptable because they can ignite concentrated fumes. Likewise, appliances with pilot lights can cause an explosion, so turn off the fuel to such appliances until paint fumes have dispersed. And, of course, never smoke in such a situation. (Theoretically, even a light switch spark could cause an explosion, if fumes were concentrated enough.)

Paintin...

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THIN SMA COURSES

Posted by on 24/ 11/ 15

Considering the technology of thin SMA layers, but not only gradation of the aggre­gate blend, but the quantity and type of binder as well, must provide a mix that can be placed by mechanical spreading of a layer up to approximately 4 cm (usually less than 3 cm) thick using a standard paver. Furthermore, the component materials and the final mix itself have to produce a layer that has the following qualities (Sybilski and Styk, 1996):

• Is impervious to water and deicers (excluding porous asphalt)

• Has a suitably high coefficient of friction

• Is resistant to permanent deformation

• Is resistant to low-temperature cracking

• Is resistant to fatigue

• Has the potential to reduce traffic noise

It is also worth remembering that, despite their many strengths, thin courses neither...

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SPRAY-PAINTING EQUIPMENT

Posted by on 24/ 11/ 15

In recent years, spray-painting equipment has become much easier to operate and maintain. Spraying is most appropriate where you’ve gota whole house to paint or where surfaces are ornate (gingerbread trim), multifaceted (shin­gles), textured (stucco), or otherwise difficult to cover with a brush or roller. Spraying is also smarter when you need to apply numerous thin, even applications, as on cabinet doors. The key to successful spray-painting, as with any painting, is thorough prep work. That is, begin by correcting moisture problems, removing loose paint and dirt, caulking and filling holes and gaps, and priming unfinished substrates.

Spray-painting safety begins with a respirator mask with two replaceable organic-vapor filters...

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Development of the historic heart of China

Posted by on 24/ 11/ 15

Development of the Wei basin is actively pursued under the early Han and, particularly under the long reign of the grand Emperor Wudi (141 to 87 BC). This is the region of the capital Chang’an (Figure 8.8). Major extensions to the Zhengguo canal are made in 111 BC, then again in 95 BC. The marshy nature of much of the land led to the devel­opment of a special technology for digging a canal deep into very unstable soil. This is the technique called canals with wells. The first of such works is the canal of the drag­on s head. Let us listen again to Sima Qian:

“The emperor called up a labour force of over 10,000 men and set them to work digging a canal leading off from the Luo River at Zheng and extending to the foot of Mt Shangyan...

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Organizing Tools &amp

Posted by on 24/ 11/ 15

In addition to organizing and teaching the crew, you will have to organize your tools and materials. Each crew and job will require a different type of organization. To give you an idea of how to go about this, we will discuss three aspects: tool organization, material storage, and material protection.

Tool Organization

Following is an example of how the crew’s tools might be organized using a job site tool truck.

Clear descriptions are important on pick­up lists. If you don’t have a detailed pick­up list, you can count on returning to the job to fix at least one task.

General

Put tools away, in their designated place, after using them.

• Hang safety harnesses and lines on hooks.

• Stand sledge hammers and metal bars in corner.

• Place saws on saw table.

• Place nail guns in ...

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Water Pressure and Drainage

Posted by on 24/ 11/ 15

Flexible cantilevered walls must be designed to resist the maximum anticipated water pressure. For a horizontal static groundwater table, the total hydrostatic water pressure can be determined from the hydrostatic head by the traditional method. For differing groundwater levels on opposite sides of the wall, the water pressure and seepage forces can be determined by net flow procedures or other methods. Seepage can be controlled by installation of a drainage medium. Preformed drainage panels, sand or gravel drains, or wick drains can be placed behind the facing with outlets at the base of the wall. It is important that drainage panels maintain their function under design earth pressures and surcharge loadings...

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