Page 2 of 11 First Next Previous Last

DIAMOND DRILLING FOR FOUNDATION EXPLORATION-Moye

Diamond Drilling Equipment

Good results cannot be obtained without suitable equipment. By far the greatest amount of diamond drilling carried out in Australia is for mineral exploration, but the equipment which may be suitable for this purpose is not necessarily suitable for engineering investigations. Also diamond drilling equipment has evolved considerably during the past fifteen years but there is still much technically obsolete equipment in use.

The ideal requirement for engineering investigations is the complete recovery of undisturbed, oriented cores.

In practice some core losses appear to be unavoidable, and it is a major disadvantage inherent in diamond drilling that these losses are most likely to occur in the weakest parts of the rock mass. In other words there is a tendency for the most important material not to be recovered as core. Excavation of ground, in which core losses occurred, has shown that the losses are usually, but not invariably, due to some important weakness such as crushed rock, clay along a fault, a zone of extreme weathering or hydrothermal alteration.

However, it is possible to come close to complete recovery of undisturbed cores in many types of ground, by using the following equipment.

Drilling machine equipped with hydraulic feed mechanism.— The hydraulic rams tend to maintain a constant pressure on the rock face and the speed of advance of the bit is automatically adjusted to the resistance of the rock.

In particular the bit tends to move forward rapidly through soft seams and this action greatly increases the chances of their recovery. Screw-feed, the other common type of feed mechanism, is quite unsuitable since the speed of advance of the bit is controlled by the motor speed through sets of gears, and has to be changed by the driller who has only very indirect indications of the changes occurring at the face of the bit.

Drilling machine as large as practicable.—In general the larger and heavier drills give better results because there is less vibration in the drilling string than with smaller and lighter drills.

The largest standard size core barrels and bits.—The greater the diameter of the core the greater the resistance to damage by vibration and torsion. The Authority has standardised on coring equipment of N-size, this being the largest standard size readily available. This produces cores from 2 1/8 to 1 7/8 inches in diameter, depending on the type of core barrel and bit.

N-type core barrels with bottom discharge bits.—This combination practically eliminates the two chief causes of core loss, namely grinding which occurs when a loose piece of core rotates on top of stationary core and erosion of weak rock by the circulating drilling water.

Triple-tube core barreI.—This barrel permits the core to be extracted from the barrel without the disturbance which inevitably occurs when it is shaken out of the end of the conventional NM barrel. The third tube fitting inside the stationary inner tube, is either a steel tube which can be opened lengthwise, or is made of transparent plastic.

Details for this article:

Diamond Drilling for Foundation Exploration

X

Author: Moye, D.G. (1967)

Article Title: Diamond drilling for foundation exploration. Paper 2150 presented at I. E. Aust. Site Investigation Symposium, September 1966.

From: Civil Engineering Transactions, April, 1967

Other Available Articles

Engineering geology for the Snowy Mountains Scheme

Moye, D.G. (1955)

Engineering geology for the Snowy Mountains Scheme.

J.I.E.Aust., Vol. 27 No.10 pp287–298

Rock Mechanics in the Investigation and Construction of T.1 Underground Power Station, Snowy Mountains, Australia

Moye, D.G. (1958)

Rock Mechanics in the Investigation and Construction of T.1 Underground Power Station, Snowy Mountains, Australia

In Engineering Geology Case Histories No.3 123–54 Geological Society of America 69 (12) p.1617

Existence of high horizontal rock stresses in rock masses.

Moye, D.G. (1962)

Existence of high horizontal rock stresses in rock masses.

Proc. Third Australia-New Zealand Conference on Soil Mechanics and Foundation Engineering. pp 19–22

Seismic Activity in the Snowy Mountains Region and its Relationship to Geological Structures

J. R. Cleary, H. A. Doyle, D. G. Moye (1964)

SEISMIC ACTIVITY IN THE SNOWY MOUNTAINS REGION AND ITS RELATIONSHIP TO GEOLOGICAL STRUCTURES

Journal of the Geological Society of Australia

Unstable rock and its treatment in the Snowy Mountains Scheme.

Moye, D.G. (1965)

Unstable rock and its treatment in the Snowy Mountains Scheme.

Proc. 8th Commonwealth Mining and Metallurgical Congress, Australia & New Zealand. Vol. 6, p. 423–441.

Diamond drilling for foundation exploration

Moye, D.G. (1967)

Diamond drilling for foundation exploration.

Paper 2150 presented at I.E.Aust. Site Investigation Symposium, September 1966. In Civil Engineering Transactions, with Discussion, April 1967.

Geology in Practice

Moye, D.G. (1970)

Geology in Practice. Presidential Address Section 3, Geology, ANZAAS Meeting.

Australian Journal of Science, 32 (12) June, p454–461.

* This paper was presented when Dan had been Director of Exploration of BHP for 3 years.

Field and Laboratory Tests in Rock Mechanics

Alexander, L. G (1960)

Field and Laboratory Tests in Rock Mechanics

Proceedings, 3rd Australian-New Zealand Conference on Soil Mechanics and Foundation Engineering, Sydney Australia, 1960, pp. 161–168.

Discussion at Technical Session No. 9—Rock Mechanics

Alexander, L. G. Moye, D. G. (1960)

Discussion at Technical Session No. 9—Rock Mechanics

Proceedings, 3rd Australian-New Zealand Conference on Soil Mechanics and Foundation Engineering, Sydney Australia, 1960, pp. 254–250