Friday, 16 December 2016

Subsurface Investigation And Its Involved Boring Methods

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. The first method involves the rotation of bits and are attached to the rods and where in the pumping of fluid mud occurs. The mud will then be returned into the surface by annular space in between rods and holes. The rods are added successively in the assembly while lowering the holes.

Core drilling. A tabular bit having a lower cutting edge is being used and rotated in a hole. A bit is consist of different available forms and the two most common forms are diamonds and hard abrasives in which rocks are penetrated. A diamond drill is considered as the most common form being used in exploratory bore and in sampling.

Core barrels. A structural drilling is aiming on recovering the undisturbed core where in structural features are being measured. Achieving the process is either done through using large diameter or multiple tube core barrels. Geophysical methods. The process helps in the location, mapping, and characterization of subsurface features by measuring the surface in order to respond to chemical, physical, and electrical 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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