FAILURE OF 2 METRE DEEP EXCAVATION FOR PILE CAP

Type of building work

This involves construction of a 4-storey flatted factory (with no basement) located

between two existing single-storey terrace houses which were founded on small diameter

bored piles.

What went wrong

Timber planks were used to support a 2m deep excavation to construct a pilecap adjacent

to an existing single-storey house. The ground condition was poor, comprising of soft

marine clay and the timber planks to support the excavation was shoddily done.

Figure 1: Shoddy timber planks to support excavation for

pile cap

The timber planks were not effective in resisting the earth pressure and gave way,

resulting in movement of the marine clay beneath the adjacent house. The ground

movement cracked the small diameter bored pile supporting the adjacent house causing

the entire front section of the adjacent house to collapse.

Figure 2: Cracking and collapse of adjacent single-storey house .

Learning points

a) Every construction project, whether big or small should be given due attention.

b) Properly designed temporary earth-retaining structures should be provided to

protect the sides of the excavation, even for shallow excavation. The design

should take into consideration the effects of inclement weather and presence of

foundation of existing buildings.

c) Extra precautionary measures should be taken when working close to existing

building.

Contaminants that may be found in drinking water

There is no such thing as naturally pure water. People are increasingly concerned about the safety of their drinking water. As improvements in analytical methods allow us to detect impurities at very low concentrations in water, water supplies once considered pure are found to have contaminants. We cannot expect pure water, but we want safe water. The health effects of some contaminants in drinking water are not well understood, but the presence of contaminants does not mean that your health will be harmed.

Drinking water can become contaminated at the original water source, during treatment, or during distribution to the home.

• If your water comes from surface water (river or lake), it can be exposed to acid rain, storm water runoff, pesticide runoff, and industrial waste. This water is cleansed somewhat by exposure to sunlight, aeration, and micro-organisms in the water.
• If your water comes from groundwater (private wells and some public water supplies), it generally takes longer to become contaminated but the natural cleansing process also may take much longer. Groundwater moves slowly and is not exposed to sunlight, aeration, or aerobic (requiring oxygen) micro-organisms. Groundwater can be contaminated by disease-producing pathogens, leachate from landfills and septic systems, careless disposal of hazardous household products, agricultural chemicals, and leaking underground storage tanks.

In general all water contains some impurities

· Erosion of natural rock formations

· Substances discharged from factories

· Discharged from farmlands

· used by consumers in their homes and yards

The origin of drinking water to your taps

Our Drinking water comes from the water in lakes or rivers (surface water), or from water that comes from wells (groundwater) and some times the sky (rain water). Many people who live in large cities or towns get their water for drinking from lakes and rivers.

Figure 1 : The Water Cycle

How Web Servers Work

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How Ethernet Works

by Nick Pidgeon
In today's business world, reliable and efficient access to information has become an important asset in the quest to achieve a competitive advantage. File cabinets and mountains of papers have given way to computers that store and manage information electronically. Coworkers thousands of miles apart can share information instantaneously, just as hundreds of workers in a single location can simultaneously review research data maintained online.

Computer networking technologies are the glue that binds these elements together. The public Internet allows businesses around the world to share information with each other and their customers. The global computer network known as the World Wide Web provides services that let consumers buy books, clothes, and even cars online, or auction those same items off when no longer wanted.

Networking allows one computer to send information to and receive information from another. We may not always be aware of the numerous times we access information on computer networks. Certainly the Internet is the most conspicuous example of computer networking, linking millions of computers around the world, but smaller networks play a roll in information access on a daily basis. Many public libraries have replaced their card catalogs with computer terminals that allow patrons to search for books far more quickly and easily. Airports have numerous screens displaying information regarding arriving and departing flights. Many retail stores feature specialized computers that handle point-of-sale transactions. In each of these cases, networking allows many different devices in multiple locations to access a shared repository of data.

In this edition of HowStuffWorks, we will take a very close look at networking, and in particular the Ethernet networking standard, so you can understand the actual mechanics of how all of these computers connect to one another. Before getting into the details of a networking standard, we must first understand some basic terms and classifications that describe and differentiate network technologies -- so let's get started!

How Banner Ads Work

If you've spent any time surfing the Internet, you've seen more than your fair share of banner ads. These small rectangular advertisements appear on all sorts of Web pages and vary considerably in appearance and subject matter, but they all share a basic function: if you click on them, your Internet browser will take you to the advertiser's Web site. But how do they work and why are they there?

Banner ads are usually relatively simple pieces of HTML code, but their presence on the Web and their importance in Internet-based business is immense. In this edition of How Stuff Works, we'll examine banner ads and their place on the Internet. We'll see how they work, how advertisers rate their effectiveness, and how you can use them to advertise your site or bring in revenue. We'll also examine the technology behind them and look at some of the different forms they can take. By the end of this article, you will be a banner ad expert!

What is a Banner Ad?
Over the past few years, most of us have heard about all the money being made on the Internet. This new medium of education and entertainment has revolutionized the economy and brought many people and many companies a great deal of success. But where is all this money coming from? There are a lot of ways Web sites make money, but one of the main sources of revenue is advertising. And one of the most popular forms of Internet advertising is the banner ad.

A banner ad is simply a special sort of hypertext link. If you've read the How Stuff Works article "How Web Pages Work", then you know how a basic text link works. A bit of HTML code instructs a Web server to bring up a particular Web page when a user clicks on a certain piece of text. Banner ads are essentially the same thing, except that instead of text, the link is displayed as a box containing graphics (usually with textual elements) and sometimes animation.
Because of its graphic element, a banner ad is somewhat similar to a traditional ad you would see in a printed publication such as a newspaper or magazine, but it has the added ability to bring a potential customer directly to the advertiser's Web site. This is something like touching a printed ad and being immediately teleported to the advertiser's store! A banner ad also differs from a print ad in its dynamic capability. It stays in one place on a page, like a magazine ad, but it can present multiple images, include animation and change appearance in a number of other ways.
Types of Banner Ads Like print ads, banner ads come in a variety of shapes and sizes. The Internet Advertising Bureau(IAB) specifies eight different banner sizes, according to pixel dimensions. A pixel is the smallest unit of color used to make up images on a computer or television screen. The IAB's standard banner sizes are:
The full banner (468 x 60) is by far the most popular, but you will see all these variations all over the Web. These are not the only banner ad shapes and sizes, either, but they are a good representation of the range of common banner ads. There is no universal file-size constraint for banner ads, but most Web sites impose their own limits on memory size, usually something like 12K to 16K. This is because banner ads add to the total file size of the page they appear on, therefore increasing the time it takes for a browser to load that page.

As you've probably noticed while surfing the Web, actual graphic content, or creative, varies considerably among banner ads. The simplest banner ads feature only one, static GIF or JPEG image, which is linked to the advertiser's home page. More common is the GIF-animated banner ad, which displays several different images in succession, sometimes to create the effect of animated motion. Then there are rich media banner ads --ads that use audio, video, or Java and Shockwave programming. These banner ads, which usually have larger file sizes, are often
interactive beyond their simple linking function.