An Overview Of Boring Methods Being Used For Subsurface Investigation

By Daniel Murphy


A geotechnical investigation is one process in which several tests and methods are performed in order to obtain information on rocks and soils physical properties. The methods are done in some particular sites for the design of foundations and the earthworks of proposed structures and of distress repair for structures and for earthworks which are caused by specific conditions. The people conducting the investigations are engineering geologists or geotechnical engineers.

The subsurface information that they need to get must be both accurate and complete because this information is important for projects in civil engineering. The most common cause of failure for structures is due to a misleading and an inadequate data of subsurface. One method that is used for subsurface investigation is auguring. This involves putting down some holes in to a soft sediment. Penetrating greater depths are made through making bore holes.

Percussion drilling. In this method, the bit will be suspended from rods or cables and will be jumped both up and down to break the rocks. For the bit to remain cool and to make slurry, the hole is added with water. The debris are also removed through a bailer. For chips to be recovered for its identification, pounded rocks are mixed in water from the slurry. Drilling progress rate and cost are varied from hardness.

Rotary drilling. From the previous method, there is an involved rotating of bits and attaching them to rods from where a fluid mud is pumped. While in the rotary process, this fluid mud is returned into a surface through annular spaces between the rods and the holes. Next is to add successively the rods to assembly during the process of lowering holes.

Core drilling. The tabular bits having lower cutting edges will be utilized and are rotated in the holes. The bits are made available in various forms. These are available in diamonds or hard abrasives for penetrating hard rocks. Types which are used very commonly are the diamonds drills and are used for sampling and for exploratory bore.

Core barrels. Structural drilling aims on recovering an undisturbed core in which the structural feature measurements are being made. The process may be achieved through the use of either multiple tube core or large diameter barrels. Geophysical methods. This will help in locating, mapping, and characterizing the subsurface features through making some measurements in the surface for responding to electrical, chemical, and physical properties.

Seismic methods. The seismic measurements include on measuring seismic waves which are traveling in the surfaces. Sometimes, some properties like material, stratigraphy, and structure are assessed in these methods. Electrical resistivity. Measuring the electrical resistivity is done by putting 4 electrodes that are in contact to the rock and the soil.

Magnetic. This method is using two primary applications including the location and mapping for buried ferrous materials and also mapping structures in geology. Micro gravity. A survey in micro gravity can provide some change measures on subsurface density. Natural variations in a density include faults, large fractures, dissolution, buried channels, and lateral changes.

Ground penetrating radar. The GPR uses electromagnetic waves in high frequency for acquiring subsurface information. The energy will be radiated downward to the ground coming from the transmitter then reflected back into receiving antenna. Reflected signals are then recorded, producing shallow subsurfaces conditions.




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