Sunday, December 18, 2016

An Overview About The Boring Methods Involved In A Subsurface Investigation

By Daniel Murphy


Geotechnical investigations are processes which involve performing some methods or tests so that soils and rocks physical properties information will be obtained. The methods will take place in a particular site where in designs for earthworks and foundations are made for proposed structures and for distress repair of earthworks and structures that are caused by unnecessary conditions. Geotechnical engineers or engineering geologists are those that will conduct the investigations.

The completeness and accuracy of a subsurface information must be considered importantly since this is very important in the civil engineering projects. Inadequate and misleading subsurface data are the two main reasons for structure failures. Auguring is a method in subsurface investigation wherein holes are placed down into soft sediment. Bore holes are created for greater depth to be penetrated.

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. Tabular bits with lower cutting edges are being used here. These are rotated in holes. Bits are composed of many different forms, some have diamonds while some are hard abrasives to penetrate the hard rocks. Diamond drills are the most commonly used types in sampling and in an exploratory bore.

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. Measuring of a seismic would involve the measurement of seismic waves that will travel through subsurfaces. The assessment of structure, stratigraphy, and material properties may be done in a seismic method. Electrical resistivity. An electrical resistivity measurement is made by placing 4 electrodes as contact to the soil and rock.

Magnetic. Two primary applications are being used in this method and these would include mapping the structures of geology and mapping and locating buried ferrous materials. Micro gravity. In micro gravity surveys, measure changes are provided to the subsurface density. Density natural variations include large fractures, buried channels, lateral changes, faults, and dissolution.

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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