Wednesday, December 14, 2016

Subsurface Investigation And Its Involved Boring Methods

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 accuracy and the completeness of subsurface information can be considered as very necessary to all the projects related to civil engineering. Usually, the cause of failure of structures is the misleading and inadequate subsurface data. Auguring is one method which is being used in subsurface investigation. This is done to put down holes in the soft sediment. And for the penetration of greater depths, bore holes are made.

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. 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. Seismic measurements would involve the seismic waves measurement that are traveling through subsurfaces. Some properties such as structure, material, and stratigraphy may sometimes be assessed with this method. Electrical resistivity. The measurements of electrical resistivity can be made through the placement of 4 electrodes which are in contact with the rock and 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 or GPR. This utilizes high frequencies of electromagnetic waves for acquiring a subsurface information. The radiation of energy is directed downwards from transmitters and reflected back into the receiving antenna. The reflected signals will be recorded, producing some shallow subsurfaces conditions.

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