mardi 13 décembre 2016

Subsurface Investigation And Its Involved Boring Methods

By Daniel Murphy


Geotechnical investigation is the process of performing several methods and tests for obtaining information about the physical properties of the rocks and soil. The tests are being done in particular sites for designing foundations and earthworks for the proposed structures and also for the distress repair structures and earthworks that are being caused by some specific conditions. Persons who will conduct these investigations are the geotechnical engineers or the engineering geologists.

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. With this method, a bit is going to be suspended from the cables or rods and is also jumped up and jumped down for breaking the rocks. Keeping the bit cooled and making slurry is done by adding water into hole. Debris are removed by the use of bailer. Recovering chips for identification is made by mixing pounded rocks into water from a slurry. The rates and costs of a drilling process are varied on the 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. 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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