US3704966A

US3704966A - Method and apparatus for rock excavation

Info

Publication number: US3704966A
Application number: US179736A
Authority: US
Inventors: Earl J Beck Jr
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1971-09-13
Filing date: 1971-09-13
Publication date: 1972-12-05
Anticipated expiration: 1989-12-05

Abstract

An apparatus and method for producing a slug of water to be delivered at high impact velocity against a surface to be eroded. It includes a cylinder containing a reciprocable ram having a shaped end. Introduction of fluid tangentially into the cylinder forms a stable annulus of fluid and reciprocation of the ram rapidly expels the fluid as a jet out an end opening of the cylinder into contact with the work to be eroded.

Description

United States Patent Beck, Jr.

[54] METHOD AND APPARATUS FOR ROCK EXCAVATION [72] Inventor: Earl .1. Beck, Jr., Ventura, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy [22] Filed: Sept. 13, 1971 [21] Appl. No.: 179,736

[52] U.S. Cl. ..4l7/490, 166/177, 239/101,

1 1 417/241 [51] Int. Cl. .F04b 7/04, F04f 7/00, B05b 1/08 [58] FieldofSarch ..417/240,241,490;175/56; 166/223, 177, 308; 239/10l, 468

[56] References Cited UNITED STATES PATENTS 3,251,424 5/1966 Brooks ..175/56 145] Dec. 5; 1972 Voitsekhousky ..239/ l 01 3 ,490,696 1/1970 Cooley 2,866,509 12/1958 Brandon ..l66/177 FOREIGN PATENTS OR APPLICATIONS 18,817 11/1893 England ..4l7/557 Primary Examiner-William L. Freeh Assistant Examiner-Leonard Smith Att0rney-Richard S. Sciascia et'a'l.

[57 ABSTRACT An apparatus and method for producing a slug of water to be delivered at high impact velocity against a surface to be eroded. It includes a cylinder containing 7 a reciprocable ram having a shaped end. Introduction of fluid tangentially into the cylinder forms a stable annulus of fluid and reciprocation of the ram rapidly .expels the fluid as a jet out an end opening of the cylinder into contact with the work to be eroded.

8 Claims, 3 Drawing Figures PATENTEDIIEB 5 I972 BAR REL -METHOD AND APPARATUS FOR ROCK EXCAVATION BACKGROUND OF THE INVENTION Avoiding the use of a high static force or lowfrequency dynamic force and the attendant heavy machines is especially attractive for deep-ocean rock fragmentation because of the difficulties in reacting large forces on unstable ocean bottoms and in lowering heavy machinery from the surface. An ideal drilling machine should be lightin weight, should react against the ocean water, and should have cutters capable of effectively destroying competent rock without a high force normal to the work face. An additional desirable if not required feature in a large drilling machine for subbottom rock drilling is the elimination of the need for a cutter which requires replacement or sharpening;

Major efforts have been made to develop systems which do not depend upon a cutter to disintegrate strong rock and thus avoid the problem of cutter replacement. Recent work has made electron-beam heating of rock practicable in a one-atmosphere situation, with the further ability to work under a small (few inches) water head. Since the beam of electrons is rapidly scattered and absorbed except in a vacuum, the

devicemust be close to the rock. The vacuum is maintained by a series of chambers, each of increasing pressure as the electrons approach the outlet. An over-pressure of air in the final stage prevents the ingestion of gas and dust into thevacuum system and allows submergence in water. This method, however, is not currently applicable to working under high pressures in the ocean. v t

It is a generally known fact that the most massive of structures is potentially subjectto destruction if it can be excited at or near its natural frequency of vibration and if its inherent damping is small. The spectacular failure of the main span of the Tacoma Narrows Bridge in the State of Washington in the early 1940s when excited by wind gusts is'a case in point. At the other end of the size scale onecould destroy rock with highfrequency excitation at the natural frequency of the verysmall rock particles as isolated, for instance, by

the Griffiths cracks. A system using .broad'band random vibration with an upper frequency cutoff such that all rock would be disintegrated to very fine particles is desirable.

Identical forces applied statically and dynamically result in stresses that differ for elastic materials by a factor of two, with the higher values resulting from high dynamic load rates. Thus a 100 percent increase in efficiency can be anticipated in a mechanism which will capitalize on this difference in resulting stresses. It is important that the load be applied significantly faster than the propagating mechanism can removethe energy within the rock. The velocity of the indentor must exceed the critical value of velocity for each rock.

So far as rock excavation is concerned, many of the methods applicable in a one-atmosphere environment will not be feasible in the high-pressure environment. Systems which generate large amounts of dust or noxious fumes cannot be used because air will not be readily available to purge the excavation. Necessity for changing bits will make the use of conventional cutters on large moles undesirable.

A rock fragmenting system which would, for exam ple, destroy the surface by the application of highfrequency vibration or a series of high-velocity water jets illustrates the ideal. In such a system neither rotational torque nor penetration force would be large, and the system would probably be small in dimension normal to the rock face, allowingeasier access and more space for particle removal, pumps, etc.

Two important methods of jet .forrnationxa re recognized. First, the straight jet with a'velocity V 2gb)", a well known hydraulic relationship; This type of jet has beenjeffective in drilling rock with pressure heads of 8,000 to 16,000 psi. Presumably even more effective are single-shot machines using a. formed capsule of gelatin, and sometimes lead. In .jets of this type, aconical impactor reacts kinetically to. accelerate the shaped gelatin in what might be called a shaped jet, which is free standing and not subject to the usual limitations of hydraulics, including wall friction. Stagnation pressures are reportedly achievable of about a million pounds per square inch. Losses in the velocity of the jet can be established by equating the momentum of the impacting conical ram and the initially stationary cylinder of gelatin, which acts as a liquid at high flow rates. In its present state of development, this system is limited by the single-shot aspect and the requirement for a shaped annular cylinder of gelatin which must be replaced after each shot. i

A method, which is feasible in both the one-atmosphere situation of the subbottom cavity and the full pressure of the ocean, is a high-velocity water jet which will erode very hard rock if sufficiently high velocity (high water-nozzle pressure) is achieved. For deepocean rock excavation, this method is especially advantageous in that power can convenientlybe transmitted as high-pressure hydraulic power in a hose. The formercan then be locally intensified by use of variable-area piston pumps with pressureintensification at approximately the ratio of the piston areas.

SUMMARY OF THE INVENTION The present invention provides a means for forming a very high velocity free standing jet of liquid rapidly and repeatedly for spalling hard rock. The rock destruction technique of the present invention reduces the rotation, torque, thrust and atmosphere contamination common to large boring machines employing cutter bits and overcomes the aforementioned problems and disadvantages of the prior type systems.

The present system creates an annulus of water which is repeatedly and rapidly impacted with a high velocity steel impactor to form a succession of extremely high velocity jets of water which is used for breaking brittle materials such as bed rock.

STATEMENT OF THE OBJECTS OF THE INVENTION It isan object of the invention, therefore, to provide a new and improved means to form a high velocity jet BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of a high velocity water jet system for deep-ocean rock excavation.

FIG. 2 is a cross-sectional view of a preferred 'embodiment of the invention for creating, rapidly and repeatedly, extremely high velocity jets of water.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in greater detail, pressure head houses a high velocity jet producing means for producing a jet 12 capable of spalling rock (on the ocean floor, for example) as shown in FIG. 1. High pressure hydraulic power as well as'gas or air lines can be provided via'barrel 14 to the pressure head and thus to the jet producing means. The hydraulic power can be locally intensified, for example, by the use of variable area piston pumps with pressure intensification at approximately the ratio of the piston areas.

As shown in the apparatus of FIGS. 2 and 3 for creating a succession of extremely high velocity jets rapidly and repeatedly, a reciprocating plunger or impactor 20, which is reciprocated at high velocity within cylindrical housing 22, ejects a jet 12 capable of spalling rock. Water is pumped into the cavity of cylinder 22 tangentially via passage 23, where it hugs the wall due to centrifugal force, forming a desired annulus of rapidly rotating water 25 to be acted upon by impactor 20, leaving a clear space 26 for the working jet 12. For underwater operation, air or other gas must be supplied to provide the clear space within cylinder 22. Passage 27 can be used for this purpose when air or gas under pressure is required, as shown in FIG. 2. The face of impactor which impacts the annulusof water may be flat or shaped as shown in FIG. 2 to force the annulus of water together and eject it as a high velocity jet 12 during each driving stroke. As the impactor moves in the direction indicated by the arrow, the spinning water is forced to converge upon itself at the center of the cylinder and in turn creates a jet along the longitudinal axis of the cylindrical chamber 22 for ejection. The annulus or torroidal shaped slug of water: 25 may be formed by any other suitable means than as shown here.

As the impactor 20 over travels the filling passage 23 it acts as a valve which shuts off the incoming water supply until the impactor has ejected the water charge in the desired shaped jet 12 and returns to uncover passage 23. Any undesired excess water which might be introduced and which unduly increases use of water, causes splash and otherwise interferes with the shaped jet 12 can be removed by suction via an annular flange 28 and second passageway 29 as shown in FIG. 2. Impactor 20 also shuts off and uncovers passage 27 during each reciprocating cycle.

Each driving stroke of impactor 20 forms a small and extremely high velocity jet 12. from the annulus of rotating water 25 as it is ejected from the open end 30 of cylinder 22. lmpactor 20 can be accelerated at velocities up to 1,000 feet per second. Hydraulic pressure for the water entering passage 23 of from 10 pounds per square inch for a slow acting system up to 300 pounds per square inch for a high speed system and reciprocation of impactor 20 from 20 to 60 strokes per second will provide satisfactory operation. A jet stagnation pressure of from 100,000 to 750,000 pounds per square inch can thus be produced for rock destruction.

Hard granites havebeen successfully spalled as much as 2 to 3 cubic per shot using a small, extremely high velocity jet. Rapid replenishment of the annulus of water, and rapidly and repeatedly impacting same provides a highly effective tool for rapid excavation of rock and the like especially in a high pressure water environment or in the one-atmosphere environment of a sealed-off cavity under the ocean. This device is not restricted to an underwater environment, but may be used for other types of rock excavating.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A method for producing an annulus of water repeatedly to be shaped into a jet and delivered at high impact velocity against a surface to be eroded, comprising:

a. injecting water tangentially into a'cylindrical cavity wherein the water hugs the wall of said cylindrical cavity to form an annulus of rotating water due to centrifugal force;

b. impacting said annulus of water with a driving stroke of a piston type means at high velocity forcing said annulus of water to converge upon itself along the longitudinal axis of said cylindrical cavity and form into a shaped jet of water which is ejected from an open end thereof at high velocity;

cylindrical cavity and impacting it to form a succession of high velocity water jets.

2. A method as in claim 1 wherein the water being injected tangentially into said cylindrical cavity is prevented from entering the cavity during each impacting stroke of the piston type means.

3. A method as in claim 1 wherein excess water which could cause splash and otherwise interfere with the shaped jet of water is removed from the cylindrical cavity during the impacting of said annulus of water.

4. A method as in claim 1 wherein an air space is provided within the cylindrical cavity when used in an underwater environment.

5. Apparatus for producing an annulus of water repeatedly and forming same into a jet which is delivered at high impact velocity against a surface to be eroded, comprising:

a. a high pressure cylinder housing having an open jet ejection end;

b. a water inlet to said cylinder wherein water under pressure is pumped into said cylinder tangentially to form a rotating annulus of water which hugs the interior wall of the cylinder leaving a major portion therein as a clear space in which a jet is to be formed;

. a piston type reciprocating impactor head in the other end of said cylinder housing for impacting the rotating annulus of rotating water with a driving stroke at high velocity to force the annulus of water to converge upon itself along the longiturepeatedly injecting water tangentially into the 6. A device as in claim 5 wherein means is provided for removing any excess water entering said cylinder housing that might interfere with the shaped jet.

7. A device as in claim 6 wherein said means for removing excess water is an interior circumferential flange within said cylinder near the open jet ejection end thereof and a controlled water outlet.

8. A device as in claim 5 wherein means is provided to form an air space within said cylinder when used in an underwater environment.

unznnn A450

Claims

1. A method for producing an annulus of water repeatedly to be shaped into a jet and delivered at high impact velocity against a surface to be eroded, comprising: a. injecting water tangentially into a cylindrical cavity wherein the water hugs the wall of said cylindrical cavity to form an annulus of rotating water due to centrifugal force; b. impacting said annulus of water with a driving stroke of a piston type means at high velocity forcing said annulus of water to converge upon itself along the longitudinal axis of said cylindrical cavity and form into a shaped jet of water which is ejected from an open end thereof at high velocity; c. repeatedly injecting water tangentially into the cylindrical cavity and impacting it to form a succession of high velocity water jets.

5. Apparatus for producing an annulus of water repeatedly and forming same into a jet which is delivered at high impact velocity against a surface to be eroded, comprising: a. a high pressure cylinder housing having an open jet ejection end; b. a water inlet to said cylinder wherein water under pressure is pumped into said cylinder tangentially to form a rotating annulus of water which hugs the interior wall of the cylinder leaving a major portion therein as a clear space in which a jet is to be formed; c. a piston type reciprocating impactor head in the other end of said cylinder housing for impacting the rotating annulus of rotating water with a driving stroke at high velocity to force the annulus of water to converge upon itself along the longitudinal axis of said cylinder and form into a shaped jet which is then ejected from the open end thereof at high velocity; d. said impactor head as it travels within the cylinder to form a jet from the annulus of water and drive it from the cylinder being operable to cut-off and prevent water from entering the cylinder housing, and as it travels back being operable to allow water to again enter the cylinder tangentially; e. repeated reciprocation of said impactor head at high velocity being operable to form successive high velocity shaped water jets.

6. A device as in claim 5 wherein means is provided for removing any excess water entering said cylinder housing that might interfere with the shaped jet.