Boring method

Abstract

A horizontal boring method comprises the steps of boring a small diameter pilot hole, thereafter removing the small diameter bit, then boring the final diameter of the bore hole by advancing a boring bit having a lead-off bar guided within and by said pilot hole, simultaneously advancing a cylindrical casing immediately behind said bit, introducing a liquid into the end of the casing to slurry the cuttings and finally, when the boring step is completed, removing the bit through the casing and cleaning the thus installed casing. A roller bit is provided which is comprised of a pilot bit mounted on a lead-off bar which is attached to the final boring bit having roller overcutters which are retractable to permit removal of the assembly back through the casing when the casing has been completely installed. The method and apparatus has particular utility in horizontal boring such as when installing drain pipe, utility mains, etc., under pre-exisiting paved areas and the like.

Parent Case Text

This is a division of application Ser. No. 380,409, filed 7/18/73 , now U.S. Pat. No. 3,837,413.

Description

BACKGROUND

The boring of the earth is an ancient and well-known process involving the use of a variety of boring bits, power sources, bore hole linings and the like for any number of purposes. The bore holes may vary in size from less than an inch to as large as 20 or 30 feet depending on its purpose. Boring is done vertically, horizontally and at almost every imaginable angle, again as a consequence of the function which the bore hole will serve.

Regardless of the function of the finished bore hole, there are difficulties that plague such operations in respect of accuracy in determining that the boring operation results in a bore hole which is suitable for its intended purpose both in direction and line. The latter requirement is particularly important where the bore hole is to be lined with a casing such as steel or plastic pipe or the like. The former requirement is particularly important where the bore hole is made through or adjacent existing environment or objects which cannot be disturbed. The difficulties in controlling line and direction are less critical where the bore hole is vertical but become more and more magnified as the direction of the bore hole approaches the horizontal and gravitational and deflective forces come into play.

By way of example of a typical situation to which the invention pertains, let it be assumed that after completion of a dual lane highway including a median strip formed as a drainage swale of lower elevation between the ribbons of pavement area, it is discovered that for one reason or another drainage of the median strip is necessary. To effect such drainage a drain pipe or culvert must be installed beneath the pavement and underlying roadbed.

The installation of such a drain pipe or culvert can be effected in several ways. The first mode is by digging up the highway and underlying subsurface to the required level and, after installing the conduit, refilling the area and repaving the disrupted pavement. This operation is fraught with disadvantages in that the paved area must be closed to traffic; it is time consuming; it is difficult to refill the dug up area and obtain the desired degree of subsurface compaction as is required to support the pavement; it is virtually impossible to repair the pavement area with any degree of certitude that the repaved area will be permanent and not subject to rapid deterioration and finally, this mode is very expensive.

The second mode of conduit or culvert installation is by a boring method which has been an adaptation of vertical drilling, as for drilling wells and the like, to horizontal drilling. In this operation, a hole is bored horizontally following the desired direction, elevation and, hopefully line, so that the bore hole will not disrupt either the pavement or the subsurface therefor. After drilling or in many cases, concurrently with drilling, the bore hole is lined with a casing, usually steel or plastic conduit of the desired size which may be, in some cases, grouted in place in the bore hole. The liner or casing assures against collapse of the bore hole after drilling and during its useful life.

The second mode of operation, while a more desirable operation than the first mode described is not, however, without disadvantages. For, in drilling a horizontal bore hole, it is very difficult to control the line and direction of the drilling due to such factors as varying soil conditions, deflection of the drill bit due to its own weight and torque loads generated in the bit rotating and advancing machinery. Because of these factors, many times a bore hole will simply not follow a straight line or will not exit at the proper location despite careful efforts to control its line and direction by every known surveying and measuring method. When such a bore hole goes awry it is necessary, not only to repeat the drilling operation, but the faulty bore hole must be refilled in a method acceptable to the particular requirements of the jurisdiction in which the work is being done. Obviously, too, the expense and time consumed in refilling and reboring is of great concern to the entity performing the work.

In the most widely used horizontal boring operations the general practices fall into the "dry" boring category, i.e. the cuttings are fed back through the bore hole toward the entrance end as broken up dry, that is without varying its moisture content, material. Where the strata to be bored is soil, i.e., clay, sand, etc., absent rock content, a conventional dirt toothed bit is used. Where the strata to be bored is rock formation, carbide teeth are substituted for the conventional dirt teeth.

In methods employing the simultaneous installation of casing, the two major boring methods involve the use of either (a) non-removable cutting heads, or (b) removable cutting heads. The former type of cutting head is sized to the approximate diameter of the casing which is forced in the bore hole behind it and therefore cannot be removed from the bore hole until it emerges at the exit side. Thus, if the head jams or teeth break during the boring operation, the problem is virtually insurmountable. The mentioned type of cutting head is provided with variable diameter side cutters which expand out, when the head is rotated in the boring direction, to the casing size and retract, when the head is rotated in the opposite direction, so that the head may be removed through the casing. While this type of head obviates the jamming and breakage problem, it does so at the expense of very high power requirements and very high torque loading of the driving and advancing apparatus due to the very high power demands of side cutting blades. By way of further information as regards the above-noted cutting heads, reference may be had to drill heads manufactured and sold by CRC-CROSE International Inc. of Houston, Tex.

THE PRESENT INVENTION

The present invention, in large measure, seeks to resolve many, if not all of the prior art modes of boring horizontal bore holes and casing same. Accordingly, a first object of the invention is to provide a method of boring which virtually eliminates misdirection of the bore hole and casing.

Another object of the present invention is to provide a method of horizontal boring in which the casing is installed simultaneously with the boring operation.

Still a further object of the invention is to provide a method of boring, wherein the difficulties and errors inherent in prior art methods are obviated or virtually eliminated.

An additional object of the invention is to provide a novel bit structure particularly adapted for use in horizontal boring operations.

The specifically mentioned objects are but a few of the objectives of the invention which are inherent therein as will be obvious to those skilled in the art from the detailed description which follows. In the descriptive material reference is made to the drawing forming a part hereof and wherein:

FIG. 1 is a schematic view showing the first step in the process,

FIG. 2 is a schematic view showing the second operation involving a number of process steps,

FIG. 3 is side view of a drilling head particularly useful in performing the method of this invention while,

FIG. 4 is an end view of the head disclosed in FIG. 3.

Considering FIG. 1, it may be seen that a situation typifying the example given in the background, there is a pavement area 10 of concrete, asphalt or the like, resting on the compacted subsurface 20 which in turn rests on the natrual strata be it simply rock-free soil, or rocky formations or combinations thereof. As shown, the pavement surface is elevated above the swale 40 which must be drained or whatever by communication with the low area to the right-hand side of the drawing.

In order to avoid disturbance of the pavement and compacted subsurface with all of the previously noted disadvantages, the novel method of this invention is employed to install a drainage conduit or culvert. As shown in FIG. 1, the area of the swale immediately adjacent the roadbed may be excavated as required to permit positioning of a portable power and drill advance unit 1 to be lowered to the elevation at which the boring operation is to take place. In cases where the elevation of the swale is low enough the excavation can be dispensed with as should be obvious. The power and advance unit, which forms no part of this invention, includes a prime mover, a torque output means for driving the rotary drill shaft and a reciprocating carriage having means to advance both pipe and casing into the bore hole. A typical example of such a unit is shown in the co-pending application of Richard P. Dunn, Ser. No. D278,349, filed Aug. 7, 1972.

Once in position at the proper elevation and after a proper survey or calculation for line and direction, the power unit has attached thereto, in the conventional manner, a small diameter drill bit 3, driven by shaft 7, on the order of two to four inches, is rotated and advanced along the calculated direction to bore a pilot hole 5 underneath the roadbed. The pilot hole 5 extends completely through the natural strata to the exit point of the proposed culvert and the exit point is closely checked by suitable measurement to determine that its exit is in the proper location. When it has been determined that the exit of the pilot hole is satisfactory, the pilot bit and its drive shafting are removed from the pilot hole.

With the final boring to be undertaken, the power and advance unit is provided with a boring head 50 attached to suitable shafting 7 and is rotated and advanced to commence the final boring. The boring head 50 is provided with a pilot bit 9 of substantially the same size as the pilot hole mounted on a lead-off bar 11, and is followed by an auger 13 mounted for simultaneous rotation with the boring head 50.

The pilot bit 9 is inserted in the previously drilled pilot hole 5 which acts to guide the pilot bit along the same line and direction as the acceptable pilot hole to assure that the bore hole 17 also follows the same line and direction and exits at the proper predetermined location.

The boring head 50 is provided with face cutters and, as well overcutters, as will be described in detail, whereby the diameter of bore hole 17 is large enough to slidably accept the tubule conduit or casing 19 which is advanced by the power and advance unit 1 behind the boring head 50. The size of the bore hole 17 relative to the casing (shown exaggerated in FIG. 2) is also large enough to permit insertion of a liquid-carrying pipe 21 disposed between the casing 19 and the interior of the bore hole 17. The discharge end of the pipe is fixed by any suitable means to the advancing end of the casing and has its discharge end directed inwardly toward the center of the bore hole 17 and is advanced along with the end of the casing into the progressing bore hole 17.

Immediately behind boring head 50 and carried by the power-driven shafting 7 is the auger 13 which fits inside casing 19 and serves to transmit cuttings rearwardly toward the entrance end of the casing, i.e., toward the power unit 1. Preferably, the area of operations of boring head 50 is flooded with water from the pipe 21 so that the cuttings are reduced to more or less slurry form to be easily moved by auger 13 and discharged from the interior of the advancing casing 19.

Since the pilot bit follows the pilot hole, it being the path of least resistance, successful boring to the proper exit location is virtually assured.

Once complete, the boring head 50 can, along with pilot bit 9, lead bar 11 and auger 13 be readily removed from the casing in either direction, the casing flushed clean and the operation is complete. In some instances, the process may involve the insertion of grouting between the interior of bore hole 17 and casing 19 but this step is a function of strata conditions and may not be necessary though it is an optional step. Finally, the power unit is removed and the excavation, if there be an excavation, is closed in the conventional manner.

After removal of the boring head, the conduit or culvert may be easily cleaned out by washing same with water from a hose or the like having in mind that the bulk of the cuttings have previously virtually all been cleaned out of the casing in slurry form during the boring operation.

It can thus be seen that the practice of the method results in a considerable reduction in numbers of bad holes bored, since the use of the pilot hole which is relatively inexpensively and quickly bored, assures proper line and direction of the final boring by obviating the tendency of the boring head 50 to deviate from its chosen path due to any one or all of the factors outlined in the discussion previous hereto.

It might be stated, here, that the manner of adding and removing shaft lengths and casing sections between the power and advance unit and the advancing head 50 is quite well known in the art and need not be labored since reference may be had to U.S. Pats. Nos. 1,413,471; 2,234,451; 2,588,068 and 3,011,567, for such teachings. The addition of casing sections to form the desired length of casing as it is advanced follows practices quite similar to conventional practices in well drilling and need not be described in great detail.

It should be further noted that the present method may result in the deletion of the behind-head auger 13 where strata conditions so permit. In such cases, the strata cuttings slurry quite readily and simply flow back into the advancing casing and are subsequently flushed out when the boring operation and casing installation are complete.

In some cases, however, the use of the auger is believed necessary as where for example, the strata does not slurry readily or is rock. The addition of water, however, does facilitate the operation since it will flush smaller cuttings back and also serves to lubricate the cutting and auger flights to reduce friction as the cuttings are moved rearwardly and thus reduce power requirements.

Turning now to FIGS. 3 and 4 a novel boring head 50 for use in the described method is shown in detail. It should be understood, however, that the described boring head can be used in a dry boring or reaming operation and, thus, is adapted for broad utility.

The head 50 includes a rod-like head shaft 51 having a working end and a coupling end 52 or left and right-hand end as shown in FIG. 3. The coupling end 52 fits with the end of torque shaft 7 shown in dotted line outline and is fastened therein by bolt and nut assemblies 53, the latter also shown in dotted line outline, since various other coupling means can be used. The coupling of head shaft 51 to the driven shaft 9 is affected just inwardly of the advancing end of casing 19 regardless of what coupling means is used.

The head shaft 51 extends a substantial distance, beyond its place of coupling with the driven shaft 52 and terminates in its working end in an internal threaded socket 54. Threaded into the socket is a lead-off bar 11 which in turn terminates in socketed end 55. Threadedly connected in the socketed end of lead-off bar 11 is a removable pilot bit consisting of a plurality of forwardly extending trunnions 57 having journalled therein a plurality of toothed cutting cones 59. The axis of rotation of the toothed cones 59 is so disposed that the rotating surface of the toothed cones forms a line contact with an imaginary vertical surface extending across the face of the pilot hole bit.

The diameter of the pilot hole bit 9, i.e. the working face thereof, will vary depending on the size of the pilot hole previously drilled which, in turn, is a function of the final diameter of the bore hole to be bored to finished dimensions by the boring head 50. Generally speaking, the larger the bore hole, the larger is the pilot hole.

Similarly, the length of lead-off bar 11 may vary in accordance with boring head and pilot bit size and the type of strata into which the bore hole is being advanced. There is no empirical formula or fixed relationship which can be used to determine the length of the lead-off bar 11. Selection of a length is a matter of experience and judgment as applied to existing conditions.

Interposed between the lead-off bar socket 54 in head shaft 51 and coupling socket 52, the head shaft carries a cutter support 61 in the form of an annular plate securely fixed thereto as by welding or the like. Projecting outwardly from the support 61 toward the pilot bit and at angularly spaced intervals are a plurality of trunnions 63 which in turn carry rotatable toothed cutter cones 65. Cutter cones 65 are of a significantly larger size than the smaller cones 59 and also are so disposed about inwardly and downwardly inclined axes so that the cone surfaces would define line contact with an imaginary vertical surface. The cones 65 define in part the principal cutting means for the boring head in forming the bore hole 17.

Immediately behind the support plate 61 there are provided a plurality of journals 67, disposed at equal angular spacing around the surface of the shaft 51 and welded thereto with their respective centers aligned along an axis disposed parallel to the axis of shaft 51. Within the journals 67 are fitted a plurality of pivot pins 62 which carry a pair of spaced hinge pintles 69, 71. Pintles 69 and 71 are welded to the lower ends of pairs of pivot arms 73, 75 which with tie plate 77 define a swingable yoke. The forward, that is cutter end of the tie plate 77 and pivot arm 73, have attached thereto forwardly projecting overcutter journals 79 in which are journalled further toothed cone shaped cutters 81. Cutters 81 are rotatable about axes disposed downwardly and inwardly toward the central axis of the cutter head so that their outer surface, i.e. the toothed cone surface, would establish line contact with an imaginary vertical plane passing transversely through and at right angles to the shaft 51. The cutting cones 81 define with cones 65 the boring means for establishing the metes and bounds of bore holes 17.

As is obvious, the cutter cones 81 are thus so mounted as to be swingable about the axis of pins 62 and means must be provided to retain these cones in effective cutting position, yet permit of swinging as and for the purposes to be set forth. To this end, a solid generally rectangular plate member 83 is affixed, as by welding or the like, betwen pivot arms 73 and 75. The plate member which is a movable stop means is so positioned as to rest against a second plate 85, defining a fixed stop means, which is affixed to the head shaft 7 and is in the form of a flat rectangular plate disposed diametrically of shaft 7 medially of the pintles 69 and 71, and has its inner edge welded to the shaft and journal 67. It is to be noted that plate 85 extends outwardly from the journal 61 such that the movable stops means 83 lies on one side of its planar surface while the axis about which the pivot arms 73 and 75 swing lies on the opposite side thereof. Thus, the pivot arms can only swing outwardly as far as stop means 83, 85 permit, but they can swing in the opposite direction, i.e., inwardly toward head shaft 51 for some distance until they abut against the shaft. Thus the cutters 81 can be opened to circumscribe an area defined by the wall of bore hole 17 larger than the diameter of casing 19 when the head shaft is rotated in the working direction, i.e., counter-clockwise as shown in FIG. 4. However, when the head shaft is rotated in the reverse direction, the pivot arms swing inwardly through arc A and hence the cutter cones 81 are drawn in and circumscribe an area which is less than the area circumscribed by casing 17 and hence the cutter head can be withdrawn back through the casing 17.

The novel boring head structure, then, provides for removal of the head back through the casing in the event of jamming or breakage. At the same time, since it is a roller boring head, it provides all the advantages of roller bits, such as smooth operation and low power requirements, to mention but a few of such advantages.

After the bore hole is completed the whole assembly, auger 13, head 50 and shaft 7 may be readily removed by withdrawal back through the cased culvert or drain or the boring head 50 may be removed from torque shaft 7 at its connector end 52 leaving only the auger 13 and shaft 7 to be broken down and removed from the power unit side of the culvert.

Finally, where soil conditions so demand, the small area around the casing 19 between it and the bore hole 17 may be filled with a grouting material. In most cases, natural settlement causes the bore hole to collapse against the casing 19 making a grouting operation unnecessary.

Having described the invention in detail, it will be apparent that various modifications will occur to those skilled in the art and which fall within the purview of the novel subject matter as defined in the claims, wherein:

Claims

What is claimed is:

1. A method of installing generally horizontal cased bore holes such as drainage culverts, electrical conduit passages and the like, comprising the steps of

a. positioning a power source at a grade level at which the hole is to be bored and the casing installed;

b. establighing the line and grade for the hole to be bored and cased;

c. drilling a small diameter pilot hole along said determined line and grade;

d. boring the final diameter hole with a boring head having a diameter slightly larger than the diameter of the casing to be installed in said bore hole, and further, having a pilot hole bit which follows in the previously bored pilot hole;

e. advancing a casing of slightly less diameter than the final bore hole diameter into said bore hole immediately behind said final boring head;

f. simultaneously advancing with the casing, externally thereof a liquid carrying conduit having a discharge outlet positioned immediately behind the boring head but beyond the end of the casing;

g. discharging a liquid from said outlet inwardly toward the center of said casing whereby the cuttings from said boring head are slurried behind the boring head and readily carried through the advancing casing toward said power source for discharge from the casing.