![]() ![]() The popularity in Hong Kong is primarily caused by the population distribution and the rapid development in the area, where any delays or accidents during construction can give severe consequences. There are many reasons for this, but in Norway it is mainly due to all the fjord crossings with sub-sea tunnels requiring careful geological investigations. Detroit Upper Rouge Tunnelĭuring the last years, directional coring has been used most frequently in Norway and in Hong Kong. As a result, the construction can be performed in a more secure manner and the stabilization can be better adapted to the geological properties. Among them are borehole radars for structural analysis, probes and tools for determination of water inflow or outflow, fracturing devices for rock stress measurements, etc.Īfter the core and borehole have been analyzed, it forms a good basis to estimate the amount of grouting and stabilization necessary, as well as production rates and material properties. A variety of probes and cameras have been specially designed for use in boreholes. The borehole itself may also be used to reveal information about the ground conditions. Since the direction of the hole and the tunnel is nearly identical, the magnitude and the properties of the various ground structures seen in the core will be similar during excavation. can easily be determined with high accuracy, while mechanical properties can be tested directly on the core. As seen in Figure 2, the location and orientation of geological anomalies, fractures, fault zones, etc. The greatest benefit with directional coring is the rock samples that is collected from the complete borehole trajectory, and lets the tunnel engineers get a visible impression of the ground conditions. Since the hole can be kept within a short distance from the centerline of the tunnel, the properties of the collected core are highly relevant for describing the ground properties that will be encountered during construction. When the borehole is controlled with directional coring, the start position and start direction is of less importance, as the borehole quickly can be guided toward and along the planned tunnel alignment. The rate of change is kept to approximately 9 degrees per 100 ft, which means that a borehole starting 20 degrees off the tunnel alignment will be parallel after about 215 ft of directional drilling. This is achieved by slowly changing the direction of the borehole. The core barrel is operated under the same parameters as a standard core barrel and requires no additional equipment or adjustments to the drill rig or drill string.īy the use of the Devico equipment, a borehole may be started at high angles from the tunnel alignment before it is guided to follow parallel with the alignment, as illustrated in Figure 1. The equipment consists of an 18-ft long wireline operated core barrel that replaces the standard core barrel when directional control is necessary. The technology has been used in the mining and tunneling industry all over the world the last 20 years. The directional core drilling technology was developed by the Norwegian company Devico AS and is provided by Tech Directional Services and International Directional Services in the United States and Canada. Our largest Drilling rig has a proven capability of a single installation of 1.2km in length.// ** Advertisement ** // Directional Core Drilling Our rigs are capable of trenchless installations of pipelines and conduit ranging in from 32mm to 1.2m in diameter. The technology also allows for installations under rivers, structures, swamps, protected trees and at depths unachievable using traditional open-cut methods.ĬDS New Zealand Limited operate a fleet of DitchWitch® directional drilling rigs that range from 120KN to 358KN of pullback capability. ![]() Through the use of trenchless equipment and methods, environmental and social impacts of infrastructure installations can be kept to an absolute minimum. The pipeline or conduit (usually a PE or PVC material) can then be directly connected behind the hole opener via a swivel.ĭuring both the guidance and hole opening process the native ground material is cut into fine particles and suspended in a drilling slurry for transportation out of the borehole. ![]() The drill string is guided along a predetermined borepath from the drilling rig to an exit pit excavation, where the steering head is removed and a hole opener (reamer) attached. The procedure is carried via a surface mounted directional drilling rig capable of pushing, rotating and pulling a string of steel drilling rods. Directional drilling is the process of installing underground conduit and pipelines while keeping excavations to an absolute minimum. ![]()
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