site exploration methods

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SITE EXPLORATION METHODS : 

SITE EXPLORATION METHODS PRESENTED BY: (GROUP 1)Hafiz Muhammad Mukhtar (2007-MS-Geo-17) Muhammad Kashif (2007-MS-Geo-01)Muhammad Farhan Arif (2007-MS-Geo-16) Muhammad Farooq (2007-MS-Geo-21) Muhammad Hussnain (2007-MS-Geo-01)

Contents : 

Contents Direct Methods Light Percussion Augers Rotary Drilling Direct Rotary Reverse Rotary Air Rotary

Light/Heavy Percussion Drilling : 

Light/Heavy Percussion Drilling The cable and tool boring is used for investigating soils The hole is sunk by repeatedly dropping one of the tools (Bailer) in to the ground. A power winch is used to lift the tool, suspended on a wire cable, and by releasing the clutch of the winch the tool drops and cuts in to the soil. Once a hole is established it is lined with casing, the drop tool is operating within the casing. Usually Water is used as Drilling Fluid. Both Light and Heavy percussion is used depending upon the site conditions and requirements.

A setup of Light percussion Rig; D/s of Emergency Spillway, Mangla Dam Raising Project : 

A setup of Light percussion Rig; D/s of Emergency Spillway, Mangla Dam Raising Project

Different Types of Bailers Used : 

Different Types of Bailers Used

Steel Casing And Driving Cap : 

Steel Casing And Driving Cap This material is available in different lengths, but is most useful in 1.5m (5-foot) lengths for by light cable percussion rigs but may be more for heavy percussion especially in case of gravels. The casing is flush jointed inside and out. The threads butt to one another, allowing heavy driving if necessary. A leading shoe is used, which may be either the same size as the casing outer diameter, or oversized.

Drive shoe of Casing : 

Drive shoe of Casing A drive shoe is attached to the bottom of the first length of casing to be driven. The drive shoe is manufactured with a hardened cutting surface at then leading edge. When fully driven into a consolidated formation a seal is created between the drive shoe and the formation.

Drilling Fluid : 

Drilling Fluid Water, either from the formation or added by the driller, mixes the crushed or loosened particles into slurry at the bottom of the borehole. An experienced cable tool driller feels when the accumulated slurry has reached the point where it is reducing bit penetration to an unacceptably slow level. At this point slurry is removed from the borehole by a bailer. Once the slurry is removed, the bit is reinserted into the hole and drilling continues.

Retrieving of Samples : 

Retrieving of Samples

Storing of Samples : 

Storing of Samples

Advantages of Percussion Drilling : 

Advantages of Percussion Drilling Highly suitable for remote settings. The cable tools low fuel consumption, small needs for water and other materials and reliability make it an excellent choice for remote site locations. Low capital investment and cheap maintenance. Capital costs of new cable tool rigs are generally significantly less than the cost of rotary of same capacity. Efficient use of personnel is there. Cable tool rigs are often operated by a single person.

Disadvantages of Percussion Drilling : 

Disadvantages of Percussion Drilling Productivity measured in hole produced per day is low compared to other drilling methods in similar formations. Hard Rock penetration rates very low.

Precautions : 

Precautions When there is a danger of caving in of the borehole. The wall of the borehole is stabilized by the hydrostatic force created by the addition of slurry.

AUGER DRILLING : 

AUGER DRILLING Often used for site investigation, environmental and geotechnical drilling and sampling, and boreholes for construction purposes, Auger drilling can be an efficient drilling method.

Hand Auger : 

Hand Auger The cutting tool (known as the auger head) is rotated to cut into the ground, and then withdrawn to remove excavated material. The procedure is repeated until the required depth is reached. Note: This method is only suitable for unconsolidated deposits.

Hand Auger Drilling Near to Lahore Lake City Project : 

Hand Auger Drilling Near to Lahore Lake City Project

Auger Drilling : 

Auger Drilling Advantages of hand-auger drilling: Inexpensive. Simple to operate and maintain. Disadvantages of hand-auger drilling: Slow, compared with other methods. Equipment can be heavy. Problems can occur with unstable rock formations. Water is needed for dry holes.

CONTINUOUS AUGER DRILLING : 

CONTINUOUS AUGER DRILLING Continuous flight augers driven by top head rotary machines carry their cuttings to the surface on helical flights. Continuous flight augers with hollow stems are often used for sample recovery in environmental, geotechnical operations.

Continuous Flight Auger Drilling : 

Continuous Flight Auger Drilling

Solid Stem Augers : 

Solid Stem Augers In use on drill rig, Finger and fishtail bits, (c) Sizes of solid stem auger flights, (d) Different assemblies of bits and auger flights. (All pictures in the above format are courtesy of DeJong and Boulanger, 2000)

Hollow Stem Augers : 

Hollow Stem Augers (a) Comparison with solid stem auger; (b) Typical drilling configuration

Direct Rotary Method : 

Direct Rotary Method In direct rotary drilling, fluid (water or water with additives-mud) is pumped down the drill pipe which then comes out from the jets in the drill bits. The fluid then flows up the annular space between the hole and the drill pipe carrying cuttings in suspension to the surface. Bentonite slurry having high specific gravity may also be used for this purpose.

Schematic Sketch : 

Schematic Sketch

Mechanism/Operation : 

Mechanism/Operation In direct circulation drilling the circulating system consists of a starting point, the mud pit, where the drilling fluid ingredients are stored.

Mechanism/Operation : 

Mechanism/Operation After mixing or the addition of additives the fluid is forced through the pumps up to the swivel and down all the way through drill pipe, emerging through the drill bit itself. From there, the drilling fluid circulates through the bit, picking up debris and drill cuttings, to be circulated back up the well, traveling between the drill string and the walls of the well (also called the annular space. At the surface, the fluid is channeled into setting pits or tanks where most of the cuttings settle out. Clean fluid is picked up from the opposite end of the setting area. The drilling fluid is re-circulated down the hole. The process continues until the drilling is concluded.

Tricon Carbide Bit : 

Tricon Carbide Bit

Diamond Studded Drill Bits : 

Diamond Studded Drill Bits

Performing of SPT During Rotary Drilling : 

Performing of SPT During Rotary Drilling

Extraction of Sample from Split Spoon. : 

Extraction of Sample from Split Spoon.

Solid Steel Drag Head Bits : 

Solid Steel Drag Head Bits

Various sizes of Drilling Rods : 

Various sizes of Drilling Rods

Reverse Rotary : 

Reverse Rotary Reverse circulation rotary drilling is a variant of the mud rotary method in which drilling fluid flows from the mud pit down the borehole outside the drill rods and passes upward through the bit. Cuttings are carried into the drill rods and discharged back into the mud pit. Reverse mud is a cost effective method for drilling bore holes of 24” and greater. This method is most successful in unconsolidated formations.

Schematic Sketch of Reverse Rotary : 

Schematic Sketch of Reverse Rotary

Air Rotary : 

Air Rotary In air rotary drilling, air alone lifts the cuttings from the borehole. A large compressor provides air that is piped to the swivel hose connected to the top of the Kelly or drill pipe. The air, forced down the drill pipe, escapes through small ports at the bottom of the drill bit, thereby lifting the cuttings and cooling the bit. The cuttings are blown out the top of the hole and collect at the surface around the borehole.

Schematic Sketch of Air Rotary Method : 

Schematic Sketch of Air Rotary Method

Limitations of Air Rotary : 

Limitations of Air Rotary Air drilling can be done only in semi-consolidated or consolidated materials. In rigs equipped with both mud pumps and air-drilling capacity compressors, drillers may switch to air drilling once the consolidated formation is reached.

Air Rotary Drilling for Anchor Holes at Emergency Spillway, Mangla Dam Raising Project : 

Air Rotary Drilling for Anchor Holes at Emergency Spillway, Mangla Dam Raising Project

Advantages of Air Rotary Driling : 

Advantages of Air Rotary Driling Good hole cleaning Excellent information on what’s happening down the hole. fast penetration high bit life Air is readily available.

References : 

References Method Statement of Drilling Reports for Instrumentation Boreholes Mangla Dam Raising Project www.geotechlinks.com Lahore Lake City Project Pictures (Taken from NESPAK)

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