Pile Driver Usefulness Through History
July 23, 2010
In today's massive commercial construction projects,pile drivers and proper pile driving techniques are critical to the establishment of a sound and reliable foundation. Although modern technology has produced fascinatingly efficient machines to insert a variety of pile types into the earth, pile driving techniques and methods have been around for thousands of years.
Likely since the dawn of time man has desired a way to make life easier through the construction of objects designed to overcome natural barriers. Builders of modern marvels such as the Burj Dubai (now the tallest structure in the world) have had the fortune of leveraging the experience and intelligence of architects, designers, and contractors that came before them.
A construction feat that often bewilders individuals that do not work in the construction field is the ability of construction crews to establish foundations for bridges and other structures in water. One of the most fascinating examples of man's ingenuity is the formation of a cofferdam for foundation development in water.
A cofferdam is essentially a damn that holds back water while construction crews develop the foundation of the structure to be built; bridge foundations are an example. Cofferdams are not new to construction; however, the machines by which they are constructed have changed over the centuries. One of the earliest uses of cofferdams dates back to around 103 A.D.
In the Iron Gates Museum in the city of Turnu Severin, Romania is a model of a bridge built during the height of the Roman Empire in honor of Trajan, the thirteenth Roman Emperor. Trajan ordered that a bridge be built across the Danube River (which today would connect Romania and Serbia). The bridge was constructed of wood and the structure's foundation was created out of huge stone piers, according to historians.
To erect the stone piers the Romans utilized a cofferdam made of oak or alder pilings. The piles, which were sharpened on the end, were driven into the riverbed by a rudimentary pile driver. The driving force for the pile driver was a large stone that was hoisted into the air through the use of a pulley and manual labor and then released. Piles were driven side by side into the river in a horseshoe shaped pattern from the shore. Historians state that the Romans often erected double-walled cofferdams for stronger support against the water on the outside.
Today's cofferdams are established much more easily. In a typical installation a vibratory pile driver/extractor can insert specially designed sheet piles into the earth under the water. Vibratory pile drivers utilize eccentric weights to vibrate the sheet pile as it is driven into the ground. The vibration of the pile allows it to move easily into the riverbed, seabed, or lakebed. Some of these piles are designed to interlock to create a water barrier; others require welding operations to secure them fully. As with the Roman methodology, once the perimeter is established the water inside of the cofferdam is then removed to create a dry project site.
Pile Driver Versatility
July 9, 2010
Pile driving techniques have never been more numerous than they are today. The construction boom of the new millennium brought forth an unbelievable need for crews to work smarter and more efficiently than they likely had seen in the previous 20 years. Due to the utility and technological advancements in pile driving machinery, engineers and architects were “breaking new ground” in the development of foundations. This is also due in large part to the abilities and intelligence that has been gained over the years by the workmen who guide and operate these astonishing machines.
Pile drivers have been around since the Roman Empire, when Caesar used a rudimentary version of them to build bridges across the Rhine River; which allowed him to create a perception that Rome’s power was superior and any invasion by outside forces would likely be highly unsuccessful. The evolution of modern day pile driving machinery has been advanced in parallel with the development of “tools” than have made the simple process much more efficient and effective. A few of these beneficial inventions include the steam engine, the internal combustion machine, and the highly refined workings of hydraulics.
Engineers now have at their command, the knowledge that most any structure can become a reality as long as they adhere to the principles of engineering for their basis. There is almost no limit to the projects that can be created, regardless of its size or location.
The Aldar HQ building in Abu Dhabi in the United Arab Emirates is a fascinating example of the marvels that can be achieved when utilizing all of the capabilities known to man. The structure is truly one of a kind in its design; a coin shaped building that is roughly 15 times as long as it is wide. This structure created a multitude of questions during its design and construction simply because there is not another structure like it in the world.
Most super structures adhere to a rectangular or square shape, allowing engineers to develop a foundation that takes into consideration the “tried and true” expectations of foundation construction. Data on wind impact is plentiful for buildings that fall within the traditional composition. The design of the Aldar HQ building brought forth a structure that was unlike any other building, and therefore there was no existing benchmarking data available to the engineers to understand what affects the local winds would have upon the structure, and ultimately the foundation that supports it.
Test returned information that illustrated how the wind would have a tendency to twist the structure. Foundation contractors had to ensure that the structure would be sound and therefore overbuilt the foundation to prevent failure.
Before construction on the foundation itself could begin, a diaphragm wall comprised of interlocking steel sheets was constructed in the earth around the perimeter of the project. The Aldar HQ’s location was closer to the sea than the engineers would have liked due to the limited land available in the area. The steel sheets were driven in with a pile driver and then over 400 concrete piles were utilized to secure the deep foundation to the bedrock. Countless pile driving machines were busy on location during the process. These machines included vibratory pile driver/extractors, diesel hammer pile drivers, and drill rigs. The Aldar HQ building finished construction on time due to the tremendous efforts of the workmen on site and the advanced machines that make up today’s available
Micropile Processes
July 16, 2010
Utilizing the micropile process in the formation of proper foundational support establishment in the field of commercial construction has become a dependable manner for construction firms to ensure consistent structural integrity.
Micropiles (often referred to as minipiles, root piles, pipe piles, and needle piles) have become a viable alternative when challenges arise on a jobsite that restrict the use of conventional pile driving techniques for traditional deep foundation system applications. Micropiles are drilled and grouted piles capable of handling weight loads up to 500 tons, depending upon the type of micropile utilized.
Often micropiles are the only alternative when physical limitations do not allow the use of massive pile driving rigs or vibratory driver/extractor systems. Examples of limitations include a job site being too close to an existing structure or an underground cavity; such as a river. Crews working in congested areas in metropolitan settings also present challenges that do not permit overhead clearance; which is necessary for standard piling driving techniques.
Typical minipiles are a combination of steel reinforcement and grout (a cement based product that cures to an extremely hard end state, allowing it to withstand pressure not allowable by typical concrete products). The relationship of the elements creates a structurally sound bond with amazing resilience
Micropiles have proven to be the application of choice when existing buildings need reinforcement. Micorpiles are used to replace deteriorating foundations, as well as to provide additional support during the renovation of existing structures; they are considered to be a welcomed method when compared to most traditional underpinning processes.
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