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What are the methods of Surveying and mapping?

From: PT BUKITMAS INDONESIA  Date:2017-11-16 10:23:22  Hits:1411  Belong to:Industry Trends
Use visual, pacing, compass or flat instrument rendezvous, the control points available for theodolite. Since 70s, remote sensing techniques have been used in large scale sites and engineering geological mapping of roads. The first geological elements in interior using aerial or satellite photos of the preliminary interpretation; then to the field for the key, doubts were observed, and the revised preliminary verification and interpretation of the results, finally using special equipment to convert to a variety of specialized or comprehensive engineering geological map.
Engineering geological exploration is to explore the geological conditions of the underground. Conventional exploration methods are available:
Pit exploration. Exposing strata by means of artificial or mechanical excavation for observation and sampling. According to the shape and depth of the excavated section, the pit detection can be divided into the pit, the exploratory well and the trench. The advantage of pit exploration is that it can directly observe lithology, bedding, various joints and fissures, weathering zones, as well as contact zones of different lithologies, fault fracture zones, etc.. The sketch can be drawn in the pit, the undisturbed sample can be collected, and various in-situ tests can be carried out. Pit exploration should not be too deep, usually above the ground water level.
Exploration of cave. Usually used in rock formations. The size of section to tolerate in observation for the degree, the length and inclination of strata and visual characters. Hole exploration is used to understand the nature of deep rock mass, to identify the strata and their weak interlayer, as well as the fracture condition, the type and nature of fault structural plane, the degree of rock weathering, etc., and also to test the in-situ mechanical properties of rock mass in the cave. Hole exploration is expensive, but it can provide in situ status and data, and is used for large rock mass projects, such as dams, tunnels and so on.
Drilling. Vertical, horizontal and inclined borehole exploration is carried out in various types of drilling rigs. The disturbed or undisturbed rock and soil samples are taken out to understand the stratum distribution and the engineering properties of each layer of rock and soil. In addition, water pressure, pumping and in-situ tests can be carried out in the hole (the latter, such as standard penetration test, side pressure test, etc.). The type of drilling rig and drilling method should be selected according to drilling depth, technical requirements and formation conditions (see hydrogeological drilling).
Penetration test. A method of in situ testing and prospecting. A cone metal probe or a cylindrical penetrator is used for penetration into the soil, and its penetration index is also measured to reflect the engineering properties of the rock or the change of the stratum. There are two kinds of penetration methods: static penetration test called static penetration test, usually characterized by penetration resistance or friction force; the hammer penetration is called dynamic penetration test; usually it is characterized by the number of hammering at certain penetration depth. The latter is divided into cone dynamic penetration test and standard penetration test (see soil test and field prototype observation).
Geophysical prospecting. Geophysical prospecting (for engineering geophysics).
In order to determine the engineering properties of rock and soil, sampling techniques are used to collect rock samples with natural structure and consistency in exploratory wells or boreholes. When taking the undisturbed cohesive soil and sandy soil sample in the borehole, different soil sampling methods and soil sampler should be adopted according to the formation properties and technical requirements. In the core drilling, a special core tube and core sampling technology are needed to take full core and to determine the fracture surface. In the sampling technique, the drilling method, sampling method and the structure of the sampler are the three keys. During sampling, press in or hit at a constant speed. When the soil is hard, the method of rotary engraving is adopted. The structural design of the original sampler should be treated differently according to different soil qualities, and the appropriate technical parameters (area ratio, inner and outer gap ratio, blade angle, length, etc.) should be selected. Commonly used are open soil sampler, piston type thin walled soil sampler (fixed piston or free piston) and double pipe rotary soil sampler. In recent years, a continuous sampling technique in soft soil has been developed, and a sampling tube with a metal foil belt has been used to continuously take undisturbed soil samples of more than 10 meters in length. This technique has been used to solve the seabed soil sampling in offshore engineering.