Drilling mud

Drilling mud is a product which is used in the process of drilling deep boreholes. Usually these holes may be drilled for civil constructions, oil, coal, water, etc.. One of the most critical roles of drilling mud is as a lubricant. Drilling generates tremendous friction, which can damage the drill or the formation being drilled. Drilling mud cuts down on the friction, lowering the heat of drilling and reducing the risk of friction-related complications. The mud also acts as a carrier for the materials being drilled, with material becoming suspended in the mud and then being carried up the drill to the surface.

Using drilling mud protects the stability of a borehole by controlling variables such as friction and pressure. Different muds are needed for different circumstances, and the selection and formulation of mud is managed by a mud engineer. This engineer determines the correct viscosity level for the drilling mud, and adjusts factors such as density of the mud as well. Water, oil, and gas-based muds can all be used, with products ranging from true muds made with materials like bentonite clays to synthetic drilling fluid.

Types od frilling

The common classification for types of drilling is by the most distinctive feature of the type:

• ROTARY DRILLS – rotary cutting action
• DIAMOND DRILLS – diamond bits
• CABLE TOOL DRILLS – cable percussion operation

Diagram from http://darshanwadikar.blogspot.com.es

Grout Driven Pile

The method Grout Driven Pile has worldwide applications. Traditionally, this is accomplished by attaching an oversized, closed ended bottom shoe to a steel casing and driving it to bearing. The driving shoe is then released and grout is pumped through the mandrel to the bottom as it is extracted. Some installation methods pump grout through side ports in the mandrel during driving as well. After grout has been pumped to the top of the pile and the steel casing has been removed, a rebar cage and centralizer bar is installed back down the pile column through the fluid grout. Grout Driven Pile have traditionally been used for axial working loads in the 50-100 ton range, but working loads as high as 200 tons have been recorded.

Grout Driven Pile are a very economical method. Their low material costs in relation to traditional steel or precast piling provide a very low cost pile in relation to their capacity. This method normally provide superior uplift resistance to traditional steel, precast or even to augercast pile. They will also normally achieve both end bearing and uplift design loads earlier than traditional steel, precast, or augercast pile. The removable steel mandrel works as a casing for installation below the water table. Since the soil is displaced laterally during driving, little to no spoil is generated at the top of the hole. This makes for a cleaner foundation than augercast pile, and is especially beneficial in contaminated soil conditions.

Continuous Flight Auger (CFA) or augercast piles System

CFA process

Since their introduction some fifty years ago in North America, continuous flight auger (CFA) piles, also known as augercast piles, have become increasingly popular, as they can be considerably cheaper than alternative pile types. With proper planning and design, efficient equipment and experienced personnel, high production rates can be achieved.

The CFA equipment comprisesa base machine with a fixed,swinging or hanging lead, an auger drive unit (hydraulic or mechanic) and a continuous flight auger equipped with auger cutting heads. For more info about the installation process, placing of reinforcement, etc, please, clic here:

– Installation process
– Casting of pile base and shaft
– Placing of reinforcement
– Advantages
– Limitations
– Soil decompression during augering

Source: Pile info

Mud desanders and desilters

A centrifugal device for removing sand from drilling fluid to prevent abrasion of the pumps. It may be operated mechanically or by a fast-moving stream of fluid inside a special cone-shaped vessel, in which case it is sometimes called a hydrocyclone.

Desander and desilter is the second and third phase equipments for horizontal dirrectional drilling (HDD). Desanding hydrocyclones remove abrasive coarse solids and sized particles downs. The desander can be moved vertically or on an incline and be either skid-based or mounted on top of a drying shaker/ mud cleaner. Directional drilling (or slant drilling) is the practice of drilling non-vertical wells. It can be broken down into three main groups: Oilfield Directional Drilling, Utility Installation Directional Drilling ( or HDD., Horizontal Directional Drilling, Directional boring) and in-seam directional drilling (Coal-Bed methane). All of the HDD need mud system and many of them needs mud desanders to be mounted on the mud tank.

Drilling mud cleaner is also called Desander and Desilter assembly,which is the combination of desander,desilter and an underflow screen. Namely, mud cleaners consists of a two-stage separation process using a combination of hydrocyclones mounted over a shale shaker to operate as a single unit. Designed to handle the entire circulating volume, Drilling cuttings cleaners are effective on both weighted and unweighted drilling-fluid systems in removing and drying solids while retaining the expensive liquid.

Installation of retaining wall, diaphragm wall diagram

Diagram of diaphragm wall construction (using mechanical grabs digging in rocky soil). The following pictoral guide illustrates the construction sequence of a typical diaphragm wall. This type of retaining wall was used for the construction of Kovan station the North East Line (NEL).

More info | http://www.docstoc.com/docs/39878651/INSTALLATION-OF-RETAINING-WALL—DIAPHRAGM-WALL

Hydrofraise

Bored piles of square section can be installed using the Hydrofraise or similar drilling techniques. The bore hole is stabilised by drilling mud. The “Hydrofraise” is a drilling machine powered by three down-the-hole motors, operating with reverse circulation.

Construction sequences of a Hydrofraise panel

1. Excavation of the pre-trench
2. Start of drilling of a primary panel, 1st element
3. Continuation of drilling of a primary panel, 2nd element
4. End of drilling of primary panel, 3rd element
5. Pouring the concrete of a primary panel
6. Construction of the next primary panel
7. Drilling of an intermediate secondary panel
8. Pouring the concrete of the secondary panel
9. Continuation of the excavation of the pre-trench

More info from GeoForum

Franki Piles (Pressure Injected Footings – PIFs)

The Franki pile, known and used world wide, was developed at the turn of the century by the Belgian engineer Frankignoul. It is a cast-in-situ concrete pile with an enlarged base and a cylindrical shaft which, due to its powerful driving method during installation, can penetrate stiff soils and reach large depths. By expulsion of a dry concrete plug, the soil surrounding the pile base is improved and thus the initial soil bearing capacity can be increased significantly. In North America, the Franki system is known as “pressure injected footing”. Although the application of the Franki system has decreased due to cost and environmental considerations, this system is still competitive and widely used when site conditions are suitable. The finished foundation element resists compressive, uplift and lateral loads. The technique has been used to support buildings, tanks, towers and bridges.

Execution of Franki piles

1. A charge of zero-slump concrete is poured into the bottom of a steel driving pipe that is placed vertically on the ground. A diesel-operated drop hammer is then driven on the concrete, forming a watertight concrete plug.
2. The concrete plug is driven into the ground by the drop hammer. The pipe is also dragged into the ground due to friction developed between the steel and the concrete.
3. When the desired depth is reached, the pipe is held in position by leads. The hammer is then applied to the concrete, driving it outwards through the bottom of the pile and forming a mushroom-shaped base.
4. At this point, a cylindrical rebar cage can be driven into the concrete if supplementary reinforcement is desired.
5. Additional charges of concrete are added and driven while the steel casing is simultaneously pulled up until the shaft of the pile is formed.

More info from GeoForum and Wikipedia

Using Drill Muds

Drilling fluids or muds are used in engineering foundations to:

• Lift soil/rock cuttings from the bottom of the borehole and carry them to a settling pit;
• Allow cuttings to drop out in the mud pit so that they are not re-circulated (influenced by mud thickness, flow rate in the settling pits and shape/size of the pits);
• Prevent cuttings from rapidly settling while another length of drill pipe is being added (if cuttings drop too fast, they can build-up on top of the bit and seize it in the hole);
• Create a film of small particles on the borehole wall to prevent caving and to ensure that the upward-flowing stream of drilling fluid does not erode the adjacent formation;
• Seal the borehole wall to reduce fluid loss (minimizing volumes of drilling fluid is especially important in dry areas where water must be carried from far away);
• Cool and clean the drill bit; and
• Lubricate the bit, bearings, mud pump and drill pipe (Driscoll, 1986).

More info here.

Drilled piles: Augercast pile CFA

An augercast pile, often known as a CFA pile, is formed by drilling into the ground with a hollow stemmed continuous flight auger to the required depth or degree of resistance. No casing is required. A cement grout mix is then pumped down the stem of the auger. While the cement grout is pumped, the auger is slowly withdrawn, conveying the soil upward along the flights. A shaft of fluid cement grout is formed to ground level. Reinforcement can be installed. Recent innovations in addition to stringent quality control allows reinforcing cages to be placed up to the full length of a pile when required. A typical reinforcing cage will consist of 4 to 8 bars from #5 to #8 bars typically 1/3 the length of the pile with longitudinal circular ties spaced along the length of the cage. Where tension loads are present it is typical to see a single full length bar placed at the center of each pile.

Augercast piles cause minimal disturbance, and are often used for noise and environmentally sensitive sites. Augercast piles are not generally suited for use in contaminated soils, due to expensive waste disposal costs. In cases such as these however a displacement pile may provide the cost efficiency of an augercast pile and minimal environmental impact. In ground containing obstructions or cobbles and boulders, augercast piles are less suitable as refusal above the design pile tip elevation may be encountered. In certain cases drill motors that produce more torque and horsepower may be able to mitigate these events.

Auger Cast Piles can be used :

• As friction piles – the superstructure load is transferred to the soil through friction between the pile surface and the soil.

• As an end-bearing pile – the superstructure load is transferred through the pile tip into a hard stratum of soil or rock.

• As an anchor pile – hydrostatic or other uplift forces are resisted though a full length tendon embedded in the grout column.

• As a vertical component of a continuous auger cast curtain wall in temporary or permanent shoring systems and below grade walls.

• As a temporary or permanent diagonal tie-back in auger cast curtain walls, beam and lagging walls, and sheet pile walls.

Source: Wikipedia and clic here.

ADSC, what is it?

Founded in the State of Texas in 1972, ADSC: The International Association of Foundation Drilling (ADSC) is a professional, international, not-for-profit trade association. The membership represents those who work in the foundation drilling industry and related heavy civil construction/design industries, and includes companies that perform work as specialty subcontractors, manufacturers and suppliers, academicians and engineers in both the private and public sectors.

Through its technical committees, the ADSC-IAFD

• conducts technical conferences and industry trade shows,
• conducts design, construction, inspection and testing seminars,
• establishes standards and specifications,
• funds pertinent research,
• offers field and management training programs including OSHA Certification,
• funds academic scholarships,
• provides project review services to government agencies and owners at all levels,
• publishes and distributes technical materials, and
• publishes and offers subscriptions to its flagship periodical, FOUNDATION DRILLING Magazine

More info here http://www.adsc-iafd.com