When located, a length of 2-in. pipe was placed in position and forced down by hand to start, and then the hammer rig, 3/4-in. pipe, etc., fitted on, and hammering commenced; two men being sufficient to raise the hammer by means of a 7/8-in. diameter rope carried over block above. When the 2-in. pipe refused to go any farther, the water was forced into the 3/4-in. pipe which was raised and dropped to cut away the material inside the large pipe. The wastewater and cuttings were discharged through the tee, and could be collected and examined. When the outfit neared the water-level, the head was unrigged, additional lengths of pipe inserted, and the operation continued. When hard, material was reached and the 2-in. pipe refused to go any farther, the whole length was pulled up; and if the end of the 2-in. pipe was burred-up, it was simply cut off smooth and used again for future holes.

CORE DRILLING WITH
DIAMOND DRILLS

The following description of diamond drilling machines and methods, and their

applications, together with the accompanying cuts, is taken, by permission, from the catalog of the Sullivan Machinery Co., of Chicago, Ill., etc.

The diamond drill consists of a line of hollow rods screwed together in 5 or 10-ft sections, rotated by an engine through a shaft and gearing, and fed forward by either a hydraulic cylinder and piston or by a screw feed. At the

lower end of the rods is placed a bit, in which pieces of "black diamond" or carbon are set, and which, as the rods are rotated, cuts an annular hole in the rock, leaving a center piece or "core" undisturbed. Water is forced through the rods to keep the diamonds cool and to wash away the cuttings from the bit. The essential feature of this method is the core or section of rock, which is formed by the hollow bit and rod as the drill advances. At intervals, usually after drilling 10 ft., the rods are withdrawn by means of hoisting mechanism, bringing with them the rock core, which is caught and held by a self-locking "core lifter." The core is then re

moved, the rods again lowered, and the process repeated until the mineral body sought is found, or the desired depth reached.

This method indicates to the prospector the exact depth of the ore body from the surface, and the thickness and character of the vein when found, as well as the nature of the material penetrated before reaching the vein. It is thus possible to estimate very closely the cost of development work, while the core of mineral furnishes accurate samples for assaying purposes. Of almost equal importance, if the mineral ore body is absent, the diamond drill indicates the fact, thus saving the cost of an exploratory shaft. The core may be preserved as a record, in boxes prepared for the purpose, each piece in its proper position as to depth. Such a record is one of the best arguments that may be used to induce capitalists to invest in mining enterprises.

FIG. 9.-Sullivan class "M" hand power diamond drill.
Capacity, 300 feet; diameter of core, 15/16 inch.

In recent years the diamond drill has been used more and more generally by engineers and contractors in testing foundations for buildings, dams, heavy bridges, dry docks, etc., and for determining the materials to be encountered in the boring of tunnels for railway work, for sewers, and for water supplies. Owing to the fact that they may be operated as well through water as through the ground, they have been used extensively for the testing of materials for sub-marine foundations, and for borings along the lines of proposed subaqueous tunnels.

Diamond drill test borings have come to be considered almost indispensable in verifying the location of solid bed rock, suitable for such structures and undertakings; since the utmost reliance is accorded the evidence which their cores provide.

Drilling outfits are now available for operation by hand power, horse-power, by belt or gearing from a gasoline or oil engine or electric motor, or by steam or air power. Over thirty different styles and sizes of Sullivan drills are actually manufactured, in capacities ranging from 300 to 6,000 ft. in depth. Cores of various sizes may be extracted, although the capacity of the drill in depth

varies with the size of the core and of the hole bored. For ordinary prospecting work in hard mineral formations, up to a depth of 1,000 ft. a core 15/16 in. to 1 3/8 in. in diameter is sufficient for all purposes, while in coal, salt, and similar friable substances, the 1-in. core gives a perfect record.

The successful operation of the diamond drill and the results secured, naturally depend on the proper handling of the machine. The diamond drill, as a piece of mechanism, is simple enough, and any stationary engineer can operate it, as far as the work above ground is concerned. It is the knowledge of the action of the bit in varying formations which is so important, and this knowledge can be gained only by experience. This is a class of work in which the difference in the results obtained by trained and by inexperienced operators is very manifest. The formations often change suddenly from soft to hard, or from solid to loose and caving

ground, and when the bit is at work hundreds of feet below the surface, the operator should be able to tell at all times what the drill is doing. A skillful operator can avoid undue wear and breakage to his carbon, prevent the occurrence of costly delays, and main

ting of diamonds in the
bits also requires practice,
and a knowledge of the
best arrangement of the
stones for various forma-
tions. It is, therefore,
strongly recommended
that when a drill is to be
used by men unfamiliar
with its
its operation, a
skilled man be engaged,
for a few weeks at least,
to instruct the regular
operators in the setting
of bits and the care and
handling of the drill.

The company's experience in conducting engineers' test borings, upon the proposed locations of bridges, dams, etc., has been particularly extensive during the last few years. Engineers have come to appreciate, with increasing force, the necessity of learning the exact location, nature and extent of foundation ma

FIG. 12. Sullivan "H-2" diamond core drill. Capacity, 1,000 feet. Diameter of core, 1 1/8 inches. This is the improved "H" drill, with internally geared hoisting drum.

terials. This tendency has been fostered by notable failures, due to incomplete earlier data, so that the diamond drill, with its solid-core evidence, is often indispensable.

METHODS OF TESTING FOR BRIDGE FOUNDATIONS

The following discussion of this subject is taken from. an article in "Engineering-Contracting" for Nov. 25, 1908, therein reprinted from "Mine and Quarry." The author is Mr. F. H. Bainbridge, Resident Engineer, Chicago and Northwestern Ry., Clinton, Iowa.

This article is confined to bridge foundations, although much of what follows is also applicable to foundations for buildings and hydraulic structures and preliminary examination for tunnel construction.

General Considerations. Two methods of testing only are effective, an open pit or well for shallow foundations and the core drill for deep foundations. Sounding with gas-pipe rods in shallow foundations and the common well drill in deep foundations are not satisfactory. Fig. 13 shows two cross-sections of a stream at the same point, the dotted line being the line of supposed ledge rock as determined by a well drill operating a chopping bit; and the full line, the correct location of the ledge rock, determined with a Sullivan "HN" diamond core drill.

In general two sets of borings should be made for an important bridge crossing; the first set, a number of borings on the center line of the proposed location, to determine whether the site is a favorable one, and, if favorable, to determine by approximate estimate the most economical location of the piers and the length

FIG. 13. Two cross sections of stream at the same point.

of the spans. In a general way it may be assumed that the economical relation is reached when the cost of the substructure equals the cost of the superstructure; but inasmuch as the cost of the superstructure can be determined with considerable accuracy, while the cost of the substructure is involved in great uncertainty, the length of the spans selected should exceed that of the apparent economical relation. The length of spans chosen may also be influenced by other than economical considerations, such as government requirements, or the liability of ice to gorge against the bridge.

Having made a tentative location of the piers, borings should be made at each pier, and in the case of pneumatic or open dredged caisson foundations, one boring should be put down at each of the four corners of the caisson.

The preliminary borings may often be dispensed with when there are well records on both sides of the river in the vicinity. These well records can almost always be found in the various state geological reports, which can be had at any public library in the state. In case of the borings at Pierre, South Dakota, to be described later, the well records were so good that borings to determine the length of the spans were not necessary.