Drilling And Cutting Submarine Rocks

Abstract

A flame jet produced by the combustion of a kerosene-oxygen mixture in a combustion chamber is projected against an underwater rock thereby to drill or cut the rock by spalling or melting. The flame jet is projected at a pressure of at least 10 atmospheres higher than the water pressure at the rock being drilled or cut. Cooling water is supplied to cool the combustion chamber walls and the parts of the rock in the vicinity of the flame jet.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to techniques in drilling and cutting rocks and more particularly to a drilling and cutting method and apparatus applied to drilling and cutting various rocks under water.

For excavating sea-bottom rock beds, the method of using impact-type breakers utilizing hydraulic pressure or compressed air, the weight dropping method wherein a heavy weight is dropped to accomplish crushing of rocks, the adhering blast charge method, and other methods have heretofore been used.

However, while the first-named method is effective for seabottom rock beds of low compressive strength, its effectiveness for hard seabed rocks of high compressive strengths of 1,400 kg/cm.sup.2 or more is low. Moreover, excavation in shallow places by this method is limited, and, at the same time, divers carrying out this method are subjected to intense impact.

In the weight dropping method, a support column is erected on land or on a ship and used to drop a weight from above the water onto a rock bed to be broken up, whereby large-scale and expensive equipment must be used. Despite this, it is ordinarily very difficult to drop the weight onto the rocks aimed at. Particularly in the case of rocks which project sharply, it is almost impossible to break these rocks with the weight, and this method in such cases is inefficient. Furthermore, when the rock bed is at a great depth, the water resistance reduces the acceleration of the weight. For this reason, an even heavier weight becomes necessary, whereby the equipment including parts such as the support column also becomes increasingly large and expensive.

The third method, i.e., the adhering blast charge method, is resorted to unavoidably in cases where it is difficult to drill holes in the underwater rock bed and to implant therein blast charges. In this method, a blast explosive is stuck onto the surface of the rock bed. For this reason, the destructive power of the resulting explosion with respect to the rock bed is very feeble, but, unfortunately, this explosion is highly destructive to the fish, mollusks, fish roe, and other marine life. Therefore, this method cannot be resorted to in actual practice from the standpoint of protecting marine resources.

On one hand, if a rock drill or rock borer for use on dry land were to be used for drilling and cutting submarine rocks, it would require provisions for preserving water tightness of its vital parts. Even with such provisions, however, such a rock drill would be very inefficient with respect to hard rocks because the drilling rate would drop remarkably particularly for large-diameter holes, whereby the efficiency of the entire operation would drop remarkably.

SUMMARY OF THE INVENTION

In view of the present state of the art of excavating sea-bottom rock beds as described above, it is an object of this invention to provide a method and device for drilling and cutting various kinds of rocks under water at a rapid rate, with high work efficiency, and in an economical manner. This object has been achieved by this invention, which is based on a completely new and original concept and principle of accomplishing drilling and cutting of underwater rocks by means of a high-pressure flame.

According to this invention in one aspect thereof, briefly summarized, there is provided a method for drilling and cutting a submarine rock by causing spalling or melting thereof by a flame jet projected at a high jet pressure against the rock through a nozzle at the forward end of a combustion chamber, into which a fuel and oxygen are injected under high pressure, and in which they are mixed and undergo combustion to generate the flame jet.

According to this invention in another aspect thereof, there is provided a device for practicing the above stated method. The device comprises, essentially, the combustion chamber, the nozzle, means for injecting the fuel under high pressure into the combustion chamber, and means for injecting the oxygen under high pressure into the combustion chamber.

The nature, principle, and utility of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings, in which like parts are designated by like reference numerals, and which are briefly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a side view, with a part cut away for foreshortening and essential parts in longitudinal section, showing one example of a flame-jet device in the apparatus according to this invention;

FIGS. 2(A), 2(B), and 2(C) are diagrammatic side views, partly in section, respectively indicating progressive states of drilling and cutting of a submarine rock in accordance with this invention;

FIG. 3 is a side view, in longitudinal section, showing the essential parts of another example of flame-jet device according to the invention;

FIG. 4 is a side view, partly in section, showing the device of FIG. 3 in a state of use; and

FIGS. 5(D) and 5(E) are sectional side views respectively showing drilled holes.

DETAILED DESCRIPTION

In one example of the invention as illustrated in FIG. 1, the flame-jet device has an outer cylinder 1 of required length accommodating near and within its forward or working end a combustion chamber 3, the forward end of which is gradually contracted into a nozzle 2 opened and directed toward the outside.

This combustion chamber 3 contains therewithin a built-in injector 6 provided with a fuel injection orifice 4 for ejecting under high pressure a fuel such as kerosene and an oxygen injection orifice 5 for ejecting oxygen under high pressure. In the instant example, these injection orifices 4 and 5 comprise minute holes arranged as follows. The minute holes of the fuel injection orifice 4 are formed in the peripheral wall of a projecting part 7 in the front central part of the injector 6 and are directed radially from the axis of the injector 6 with a forward inclination of approximately 75.degree. relative to the injector axis. The minute holes of the oxygen injection orifice are formed on a common circle around the projecting part 7 through the front face of the injector 6.

A passageway 8 communicating at one end thereof to the fuel injection orifice 4 is connected at the other end to a fuel supply tube 9. A passageway 10 communicating at one end thereof to the oxygen injection orifice 5 is connected at the other end to an oxygen supply tube 11 disposed coaxially around the fuel supply tube 9. These supply tubes 9 and 11 extend rearward to the rear part of the outer cylinder 1 and are there connected to pipes respectively connecting them to fuel and oxygen supply sources (not shown).

In the instant example, a water flow path 12 is formed around the combustion chamber 3 and is continually supplied with cooling water thereby to carry out cooling of the parts surrounding the combustion chamber.

In the case where the fuel is supplied through the fuel injection orifice 4 at a supply pressure of 15 kg/cm.sup.2 or more, and the oxygen is supplied through the oxygen injection orifice 5 at a supply pressure of 15 kg/cm.sup.2 or more, the pressure of the flame ejected from the nozzle 2 will be approximately 10 kg/cm.sup.2.

Accordingly, the fuel and oxygen thus ejected out from the fuel injection orifice 4 and the oxygen injection orifice 5 of the injector 6 are mixed at the time of their ejection and undergo combustion within the combustion chamber 3 at approximately 3,200.degree.K. The flame resulting from this combustion is ejected through the nozzle 2 as a flame jet of a high pressure of not less than 10 atmospheres.

For drilling and cutting a submarine rock through the use of this flame jet, the flame-jet device or drill is placed on the rock with the nozzle 2 directed toward the surface of the rock, and the flame is caused to be jetted as described above, whereupon the part of the rock thus subjected to the flame jet undergoes thermal disintegration or spalling due to the jet pressure and to the high temperature, and drilling through the rock is accomplished as indicated in FIG. 2. Cutting of a submarine rock can also be carried out readily by continuously drilling a row of contiguoug holes according to the above described procedure.

In certain cases, in the process of drilling a rock under water, the diameter of the hole thus formed in the rock becomes of an order somewhat greater than the outer diameter of the flame because of the water pressure and cooling effect around the nozzle 2, that is, when a flame-jet drill as in this example is used, the drilled hole diameter becomes substantially the same as the outer diameter of the outer cylinder 1 of the drill, whereby the insertion of the outer cylinder 1 into the drilled hole as the drilling operation progresses is obstructed.

In such a case, in accordance with this invention, a shroud or hood 13 of larger diameter than the outer cylinder 1 is slidably and coaxially mounted on the working end part of the outer cylinder. Then, at the time of drilling, this hood 13 is placed in abutting contact with the surface of the rock thereby to form an enclosure around the surrounding region of the nozzle 2. Then, when the flame jet is projected toward the rock as the effect of the water is thus avoided, the above mentioned difficulty is readily overcome.

In another embodiment of this invention as illustrated in FIG. 3, the flame-jet device has an outer cylinder 1 of a specific length (the rear part of which is not shown) to the front or working end of which a cylindrical cap 14 of substantially the same outer diameter as the outer cylinder is coaxially connected by fastening means such as a screw joint. The forward end of this cap 14 is provided with an opening 15, and the cylindrical wall of this cap near its forward end is provided with a suitable number of holes 16 for ejection of cooling water.

A cooling water conducting tube 17 for forming a water passageway 12 is disposed coaxially within the outer cylinder 1, its front end being separated by a specific distance from the inner part of the front end of the cap 14. The inner and outer sides of this conducting tube 17 are communicative around the end rim thereof. The cooling water supplied by this cooling water conducting tube 17 surrounds the outer surface of a combustion chamber 3 to cool this combustion chamber and then is ejected out through the cooling water ejection holes 16.

Within this cooling water conducting tube 17, there is coaxially disposed an oxygen supply tube 11, the forward end of which is connected to the rear end of the combustion chamber 3 by way of an injector holder 18 interposed and connected therebetween. The forward end of this combustion chamber 3 is contracted into a nozzle 2 opening into and terminating at the aforementioned opening 15 of the cap 14. The nozzle 2 has a throat section 3a of minimum cross-sectional area and, from this throat toward its outlet, it expands in cross-sectional area. At its extreme forward end, the nozzle 2 is provided with a flange 3b, the outer rim part of which fits against the inner surface of an inner rim part of the cap 14 surrounding the opening 15. The part of this flange 3b not contacting the cap 14 is also provided with cooling water ejection holes 16 disposed on a common circle with a center lying on the nozzle axis.

Within the oxygen supply tube 11, there is coaxially disposed a fuel supply tube 9 connected at its forward end to the rear end of a central hole 18a of the above mentioned injector holder 18. An injector 6 is connected to the injector holder 18 at the front end of this central hole 18a. This injector 6 is of substantially the same construction as that in the preceding example illustrated in FIG. 1, and therefore detailed description thereof will be not be repeated.

In the operation of the drilling and cutting device of the above described construction, a fuel such as kerosene is supplied under pressure to and through the fuel supply tube 9 and is injected through the fuel injection orifice 4 into the combustion chamber 3. As the same time oxygen is supplied under pressure to and through the oxygen supply tube 11 and is injected through the oxygen injection orifice 5 into the same combustion chamber 3. The fuel and oxygen thus injected are mixed and then undergo combustion at approximately 3,200.degree.K within the combustion chamber 3. The resulting product of combustion is ejected out through the nozzle 2 as a high-pressure jet flame.

In utilizing this flame to drill and cut a submarine rock, the device is so disposed so that the front end surface of the cap 14 is pushed against the rock, and the device is operated to project the flame jet against the rock surface, whereupon the ejection pressure and high temperature of the flame cause spalling or fusion of the part of rock thus subjected to the action of the flame. Thus, in the case of drilling, a hole as shown in FIG. 5 is formed. In the case of cutting, a row of contiguous holes are drilled in the above described manner.

During the above described drilling or cutting operation, cooling water is ejected simultaneously through the cooling water ejection holes 16 around the end part of the cap 14 and the ejection holes 16 in the end flange part of the nozzle 2 thereby to cool the parts in the vicinity of the front end periphery of the cap 14. Accordingly, even in the case of rocks such as andesite and basalt whichare not spalled by the flame but are melted, the melted rock is prevented from sticking to the nozzle. At the same time, the cooling water prevents damage to the cap 14 and nozzle 2 due to high temperature.

The cooling water ejected through the above mentioned cooling water ejection holes may be introduced through a route separate from that of the cooling water for cooling the combustion chamber 3, and a supply path exclusively for cooling water for ejection may be provided.

By drilling a rock in the above described manner, a hole of a diameter which is somewhat greater than the outer diameter of the flame can be formed as indicated in FIG. 5 as result of the water pressure around the cap 14 and the cooling effect of the water. That is, through the use of a device as illustrated by the instant example, a hole of a diameter which is substantially equal to the outer diameter of the outer cylinder 1 is formed, and the insertion of the device into the hole as the drilling progresses is not obstructed.

When a hole is being drilled in a rock for a purpose such as anchoring, the advance of the device into the rock is halted at a suitable point while the flame jet ejection is continued. As a result, a bulbous region of large diameter in the hole as indicated in FIG. 5 (E) is formed at a depth corresponding to the depth of insertion of the device and can be utilized for filling with an anchoring material or structure, which will thereupon be securely anchored and prevented from being pulled out.

While the cooling water ejection holes 16 have been described as being provided in near the forward end of the cap 14 and in the forward end flange 3b of the combustion chamber 3, the positions, orientations, and other particulars of these holes may be suitably modified or selected as necessary for maximum effectiveness in specific applications.

In accordance with the method and device according to this invention, a flame jet ejected from a nozzle is utilized to accomplish drilling and cutting of underwater rocks. Accordingly, drilling and cutting of rocks in water, where such work is difficult, can be carried out with high efficiency. Since the region around the flame is continually cooled with cooling water simultaneously with the projection of the flame, there is no possibility of damage due to heat to the forward tip of the nozzle when the drilling or cutting is carried out with the nozzle tip pressed against the rock surface. That is, it is not necessary to maintain the nozzle tip separated from the rock surface. Therefore, the underwater work is made even easier, whereby the work efficiency can be increased even further.

Even when the device of this invention is used for rocks which may be melted and distintegrated by the flame, there is no possibility of adhesion of the rock thus melted to the nozzle to damage the nozzle tip. Accordingly, the device can be applied to any kind of rock, and there is no necessity of using an expensive heat-resistant material for the forward end part of the outer cylinder, for example, and an inexpensive and easily fabricated material can be used. At the same time, the nozzle itself can be fabricated at low cost. Thus, the present invention affords practical economy and facility in submarine rock drilling and cutting operations.

EXAMPLE OF EXPERIMENTAL RESULTS

A submarine drilling test relative to granite of a compressive strength of 2,400 kg/cm.sup.2 was carried out with a flame-jet drilling device according to the invention, in which the combustion chamber pressure was maintained constant at 20 kg/cm.sup.2, whereupon the following results were obtained.

______________________________________ Water Average drilling Average depth rate diameter (meter) (cm/min.) (cm) ______________________________________ 2 80 10 10 50 9.0 20 40 8.5 30 30 8.5 ______________________________________

Claims

We claim:

1. A device for drilling and cutting submarine rocks comprising:

an outer cylinder having an opening at the forward end thereof;

a fuel supply tube within said outer cylinder;

an oxygen supply tube within said outer cylinder;

a combustion chamber within said outer cylinder and having a nozzle formed at the forward end thereof and facing out through said opening of said outer cylinder;

means for supplying under high pressure fuel and oxygen respectively through said fuel and oxygen supply tubes;

an injector connected separately to said fuel supply tube and said oxygen supply tube and having fuel injection orifices and oxygen injection orifices respectively for injecting fuel and oxygen under high pressure from said fuel and oxygen supply tubes into said combustion chamber, said fuel injection orifices being radially inclined relative to the injector axis for crossing of the fuel stream and oxygen stream ejected from said injection orifices for mixing and combustion of the fuel and oxygen to produce a flame jet ejected forward and out through said nozzle under jet pressure of the order of at least 10 atmospheres higher than the water pressure at the water depth of said submarine rocks, the flame jet being projected against said submarine rock for drilling and cutting by spalling or melting thereof; and

water-cooling means for supplying cooling water to cool said combustion chamber and nozzle and regions surrounding the flame jet.