US3293865A - System for lining large diameter bore holes - Google Patents

Description

Dec. 27, 1966 R. L. LOOFBOUROW ETAL 3,293,865

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Filed May 27, 1963 5 Sheets-Sheet 1 HHH ml F761 W INVENTORJ IPOBERTLZOOFBOUROW BY JbHN/fE/VRYJ'Cfl/PKE ATTORNEY! Dec. 27, 1966 R. LOOFBOURCSW ETAL 3,293,865

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES INVENTORS RoaERrLLaaFsoz/Row BY JOHN HENRYJcH/PKE AT TORNE Y6 1966 R. 1.. LOOFBOUROW ETAL 3,293,865

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Filed May 27, 1963 5 Sheets-Sheet 3 1 F/GZA IN VE N TOR) RwERrLlaoFaw/Raw BY JaH/vh'En/RrJbfl/PKE A T TORNE Yo Dec. 27, 1966 R. LOOFBOUROW ETAL 3,

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Filed May 27, 1963 5 Sheets-Sheet 4 IN VENTORS koafkrLloofaoz/fiow BY JbH/v/YEn/RYJcn/PKE ATraR/vE YJ R. 1.. LOOFBOUROW ETAL 3,293,865

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Dec. 27, 1966 5 Sheets-Sheet 5 Filed May 27, 1963 WE MW Mum MY m E H m United States Patent 3,293,865 SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Robert L. Loofbourow, 4032 Queen Ave., S., Minneapolis, Minn. 55410, and John Henry Schipke, 5324 Lyndale Ave., S., Minneapolis, Minn. 55419 Filed May 27, 1963, Ser. No. 283,405 8 Claims. (Cl. 61-41) This invention is directed to the lining, or drilling and lining, of deep bore holes of large diameter extending into the earth. More particularly, this invention is directed to the lining of deep large diameter bore holes by means of a rigid tight tubular liner of reinforced settable material cast in stationary slip forms held in place at the surface of the earth over the bore hole, the liner then being lowered into the bore hole as fast as the liner is formed.

It is usual practice to support the walls of wells and similar shafts with steel casing, successive lengths of casing being made up in threaded joints or welded as the casing is lowered into the hole. The casing is subsequently set in cement which is placed under a hydrostatic pressure greater than the pressure of ground water so that cement slurry enters and seals any water channels in the formation through which the hole passes. While this system is practicable for small diameter holes, the diificulty of using the same materials and methods for larger bore holes and shafts becomes obvious. One need only consider the necessary thickness of such steel liners in order to resist collapse in handling and while they are being cemented in place. The expense of manufacturing, shipping and storing such large and heavy liner sections presents a formidable problem.

The present invention contemplates the lining of such large diameter deep bore holes by means of a continuous tubular reinforced liner which is cast in stationary slip forms and then lowered into the hole. By large diameter bore holes is meant shafts or holes more than about three or four feet in diameter. Such holes may be anywhere from several hundred to several thousand feet in depth. The art of rotary drilling has developed to the point where shafts of 25 feet in diameter and 1,600 feet in depth have been completed. The development of equipment to bore large daimeter holes and the use of muds to support them temporarily were ahead of the ability to line such holes when completed, until the time the present invention was made.

The shaft lining system according to the present invention may be utilized in lining previously formed large diameter bore holes or it may be utilized to line such a bore hole simultaneously with the drilling of the bore hole. In this latter instance the weight of the liner itself may be utilized to exert drilling force against the drilling apparatus at the bottom of the hole.

The present invention is illustrated by means of the accompanying drawings in which the same numerals are used to identify corresponding parts and in which:

FIGURE 1 is a schematic cross-sectional view of the surface end of a deep large diameter hole bored into the earth and showing means for the casting of a continuous liner in stationary slip forms;

FIGURE 1A is a similar cross-sectional view showing alternative expedients for carrying out the lining system according to the invention;

FIGURE 2 is a further schematic cross-sectional view of a large diameter hole bored itno the earth and showing means for forming a reinforced liner in sections by casting in stationary slip forms and then lowering in sections into the hole;

FIGURE 2A is an enlarged fragmentary section of a portion of concrete liner showing means of horizontal reinforcement;

FIGURE 3 is a partial cross-sectional view showing a rotary bit for drilling large diameter bore holes utilizing the Weight of a slip formed cast concrete liner, shown in drilling position; and,

FIGURE 4 is a partial cross-sectional view of a rotary bit as in FIGURE 3 shown in hoisting position with the outermost cutting elements retracted.

Referring to FIGURE 1 of the drawings, there is shown a large diameter bore hole or shaft 10 extending into the earth. The upper end or foreshaft of the bore hole or shaft 10 adjacent the surface of the earth 11 is of somewhat larger diameter and is provided with a cylindrical lining 12 extending a short distance into the earth. The usual derrick 13 extends above the collar of the shaft. A stationary tubular slip form composed of outer Wall 14 and spaced apart inner wall 15 is rigidly supported at the collar of the shaft. example, from an annular beam 16 and suitable bracing. The inner slip form wall 15 may be supported from a platform 17 above the collar of the shaft on the derrick.

An annular unobstructed space 18, which is open at both ends, is defined by the surfaces of slip form walls 14 and 15. The reinforced liner 19 is cast in the stationary slip form by placing a concrete mix or other settable material into the annular space 18, permitting this to set sufiiciently to retain its form and then discharging from the annular space at the bottom of the slip form.

In order to form the initial segment of the liner 19, it is necessary to temporarily close the bottom of the stationary slip form in order to retain the initial material poured into the annular space 18 at the top of the slip form. This temporary closure may be in the form of a flanged annular ring 20. This ring is initially supported (as, for example, by the vertical reinforcing elements) in contact with the bottom edges of the slip form walls 14 and 15 to form a temporary bottom closure for the annular space between the walls. Alternatively, ring 20 may be supported by attaching it to a flanged bell form bulkhead 21 provided with an eyelet 22 by means of which it may be suspended by cable 23.

Both supporting means may be used together. Cable 23, as shown, is suspended from the hook 24 of a hoist means including a pulley block 25 suspended by cables 26 from a bank of sheaves 27 at the .top of the derrick. Cable 23 passes through guide means 28 on platform 17 to position it centrally within the liner.

Ring 26' performs a further function as an anchoring means for vertical reinforcing elements within the cast lining 19. In its preferred form, each reinforcing element is an elongated steel wire or cable 29. The free end of reinforcing cable 29 is secured to ring 20. The reinforcing element extends through the annular space 18 between the walls 14 and 15 of the stationary slip form being supplied from a supply reel 30 and then passing over a sheave 31 supported by the derrick over the annular space of the stationary slip form. Interconnected reinforcing rods may also be used. A plurality of vertical reinforcing elements are provided at relatively uniformly spaced intervals around the periphery of the stationary slip form. Each vertical reinforcing element is preferably engaged by a jack 32 which serves to maintain the reinforcing element under tension, to regulate its rate of feed into the slip form and, in some instances, to support the cast liner.

The inside surfaces of the slip form walls 14 and 15 defining the annular space 18 are smooth so as not to obstruct flow of the liner through the form. The initial segment of the prestressed reinforced liner 19 is formed by placing a suitable concrete mix or other settable material into the top of the annulus 18 and substantially filling the form. -The reinforcing elements 29 are preferably The outer wall 14 is supported, for

maintained under tension and spaced from the slip form walls as the concrete mix is being placed. A relatively quick setting concrete mix is preferably employed, although resinous materials such as epoxies, polyesters and the like may be used.

The outside diameter of the stationary slip form may range from 3 feet to 25 feet or more and the thickness of the liner formed may range from several inches to a foot and a half or more. form may range from about 4 feet to 8 feet or more. The rate of fill of the stationary slip form and the setting rate of the liner are preferably so interrelated that as the slip form begins to fill up the material placed in the bottom of the slip form has already set sufficiently to retain its form. Thus, before the slip form becomes full, the ring 20 may be lowered away from the bottom of the slip form carrying with it the set-up reinforced liner.

The lowering of the ring and liner leaves additional room at the top of the slip form to be filled. Thereafter, the cast liner is desirably lowered progressively, either intermittently or continuously, as further material is progressively added in the top of the slip form. The progressive rate at which the liner is formed may vary Widely depending upon such factors as the diameter of the bore hole, the thickness of the liner, the setting rate and the like. Accordingly, the liner may be progressively cast and discharged from the stationary slip form at rates ranging from a few inches to several feet per hour.

The movement of the liner through the form simulates hand working of the liner surfaces and results in a relatively impermeable structure. However, Where even greater impermeability is desired, a sealant may be applied to the outside of the liner as it is formed. Such sealants are known and include asphaltic paints, sodium silicate, rubber base paints, and the like. One manner of applying a sealant coating is by means of a spray ring 33 disposed below the bottom of the stationary slip form and having a plurality of inwardly directed jets or spray nozzles through which a sealant composition is sprayed under pressure. An alternative, or supplementary, method of applying a sealant is to provide a floating layer 34 of sealant material in the shaft on top of the drilling liquid 35 in the shaft. As the liner is lowered through this floating layer, a film of sealant is applied to the outer surface of the liner. As the liner is lowered through the drilling liquid the hydrostatic pressure exerted by that column of liquid forces the sealant into the pores of the reinforced concrete liner, whether the sealant is applied from the spray means or floating layer, or a combination of the two. The result is a tightly sealed impermeable dry lined shaft.

The lengthening cast liner is supported and its downward movement is controlled by several diflerent means used separately or together. By closing the bottom of the liner 19 by a bulkhead 21, the liner is made buoyant with respect to the drilling liquid 35. The displacement of the drilling liquid serves both to support the liner and control its movement. The liner is also supported by its vertical reinforcing elements which may be fed at a controlled rate either by jack means or by slow speed hoist means. Support is also provided by cable 23 and downward movement is controlled by connecting this cable to a heavy slow speed hoist. Where bulkhead 21 is not used, tanks or other containers evacuated of air may be attached to the lower end of the liner to provide bouyancy.

Referring to FIGURE 1A there is shown schematically a slightly different arrangement of equipment at the top of a bore hole 10' to be lined. The foreshaft lining 12' is stepped to provide access for workmen to the slip form cast liner. A derrick structure 13' rests on the collar of the foreshaft lining at the surface of the earth 11'. The stationary tubular slip form composed of outer wall 14' and spaced apart inner wall 15 is rigidly supported near the earths surface above the bore hole. The reinforced The depth of the stationary slip concrete liner 19 is cast in the stationary slip form, as

' already generally described. The bottom of the liner 19' is in the form of an annular ring 20'. The liner is both reinforced and supported by means of a plurality of flexible elongated vertical reinforcing elements 29' anchored in ring 20' and being supplied from a supply reel 30' and pasing over a sheave 31' and supported by jack 32'. The reels of reinforcing elements and the jacks are supported on platform 17' of the derrick 13'. Spray means 33 are provided spaced around the liner 19' below the slip form for application of sealant material.

The slip form walls 14 and 15' are held spaced apart by rigid spreader numbers 79 spaced at intervals about the periphery of the stationary slip form. In order to facilitate even distribution of concrete to the slip form, a rotatable distributor means is employed. This includes a hopper 80 mounted on a base 81 which is supported on a platform 82 within the stationary slip form. A revolving spout or chute 82 distributes the concrete from hopper 80 into the slip form. A lip 83 extends around the inner wall 15 of the stationary slip form to facilitate feeding of the concrete mix from the hopper as the chute revolves. Concrete mix is sup-plied to the hopper 80 by means of a cantilevered conveyor 84. To permit access by workmen to the interior of the cast liner 19, a stage 85 is suspended within the liner. This is preferably by means of a plurality of cables 86 or the like suspended below platform 82. In order to permit access to the staging, a manhole 87 is provided in platform 82.

As shown schematically in FIGURE 2, the reinforced concrete liner may also be formed in separated segments which are lowered successively into a shaft and fitted together to form a continuous shaft liner. Referring to FIGURE 2, a hole or shaft 10A of desired depth is bored into the earth. A first liner segment 19A is cast by pouring concrete mix into the top of a stationary slip form composed of an outer wall 14A and a spaced apart inner wall 15A in the manner already described. This first formed segment of the reinforced concrete liner is lowered into the shaft and positioned at the bottom of the shaft. Successive segments, as indicated by liner segment 19B, are separately formed and lowered successively into the shaft each being positioned on top of the immediately preceding lower liner section.

In order to facilitate fitting of the liner segments together, the top of each section is formed with an inward taper and the bottom of each section is formed with a mating outward taper. To insure a tight fit an O-ring 40 is preferably also seated in the inward taper at the top of each liner section. Then, when the next successive liner section is seated, its weight compresses the O-ring to insure a tight seal.

To protect the liner sections against damage through contact with the wall of the shaft during their passage down through the hole, each liner section is provided with a plurality of centralizers or bumpers 41 secured to the outside wall of the liner section and distributed evenly about its periphery. These bumpers serve merely to hold the shaft liner sections spaced from the wall of the shaft as they are lowered.

The liner sections may be lowered, for example, by means of a cable 23A secured to eyelets 42 embedded into the top portion of each liner section. Cable 23A passes over a sheave 43 journaled in derrick 13A to a hoist 44. To facilitate gentle lowering of the liner sections, each liner section is closed at each end by a bottom bulkhead 45 and a top bulkhead 46. Each bulkhead section is lowered through the drilling liquid 35A. The bouyancy of each liner section is controlled by the density of the drilling mud, by liquid introduced into the liner inside the bulkheads and, in some instances, by added weights. A vent hole 47 is provided in the upper bulkhead 46 to permit equalization of pressures.

After all of the liner sections are positioned, the drilling fluid is pumped from the shaft and the bulkheads are removed. The liner sections may be provided with an outer sealant coating either by spraying or by means of a floating layer or both, as already described. The bottom of each liner section is initially formed by a ring secured to the bottom of the slip form. This ring may either be left in place and lowered as part of the liner section, or it may be made in sections for removal after the bottom end of each slip form section has set up sufiiciently to retain its form.

Although the cast liner is in most instances desirably of a circular cross section, it is by no means so limited. It may be elliptical or rectangular and integral compartmented shaft liners may be case in order to provide separate channels to accommodate upcast and downcast air movement. Such a liner may take the form of a compartmented rectangular liner, or a circular compartment inside of a rectangular liner, or a rectangular compatment inside of a cicular liner.

The lining system according to the present invention is especially adapted to conditions where there is soft wet ground above strong tight bedrock. These conditions make conventional shaft sinking extremely diflicult. Where these conditions are encountered, the system of the present invention is used to extend a tight strong reinforced concrete liner down to a depth at which it may be set tightly into the bedrock. T hereafter, further lining may not be needed because of the strength and tightness of the bedrock. In some areas a succession of wet and dry beds which range from loose to coherent are encountered. Where such conditions are found, the shaft lining system of the present invention is especially useful to extend a liner which is tight and strong and which can be set tightly into bedrock.

The liner produced by casting in stationary slip forms according to the present invention may be set in much the same manner as metal casing. The liner may be set in cement grout placed in the liner and displaced into position by drilling mud pumped after it or, as is more usual in cementing large diameter casings, the cement may be placed directly in the annulus outside the casing. Instead of being set in cement, the liner may be set in a bitumen material. This latter is desirable where it is contemplated that the ground around the lined shaft might move as-the result of subsidence expected to accompany mining or otherwise. In this manner water may be completely sealed but the bitumen will adjust plastically to ground movement to maintain the seal rather than cracking.

For additional strength, the liner is also desirably provided with horizontal reinforcing in the form of rings of appropriate shape to correspond to the cross sectional shape of the concrete liner tube and of any desired cross section. In weight and cross section, these horizontal reinforcing elements maybe anywhere from light reinforcing rods to heavy rolled structural steel. As shown in FIGURE 2A, arcuate rolled structural steel I-beams 36 are assembled into rings and embedded in the cast concrete tube. Alternatively, a recessed channel 37 may be cast in the Wall of the liner. This is done by inserting a channel form into the top of the stationary slip forms. This channel form passes through the slip form along with the cast concrete tube and may be removed from the tube after it has cleared the bottom edge of the stationary slip form. Then a ring of structural steel members 36A are installed around the liner, set into the recess so as not to protrude out into the lined shaft. In some instances the reinforcing members 36B are secured around the cast liner in a cast iron or steel channel 38.

In their simplest form, the horizontal reinforcements are in the form of rods 39 cast into the concrete. These rods may be wired to the vertical reinforcements 29 if desired. Instead of using a series of horizontal rods, the reinforcements 39 may be in the form of a wire or cable cast in the concrete tube in the form of a spiral.

While the reinforcing elements 36A, 36B and 38 are illustrated as being secured to the inside periphery of the tube, this is a matter of choice and they may be installed around the outside periphery. In most cases, however, access to the inside of the cast liner from a stage suspended from the derrick is easier and therefore preferred. These various horizontal elements may be used separately or in combination dependent upon the needs dictated by conditions found in any given shaft. The reinforcing elements may be added uniformly throughout the length of the liner or, where unusual ground pressures are anticipated at particular elevations, additional reinforcement can be added to resist such pressures.

In order to insure proper alignment of the reinforced concrete tubular liner, concrete should 'be placed evenly around the stationary slip forms. In this manner the tube formed will be straight. A constant check is maintained on the vertical alignment of the shaft liner in order that any deviation from vertical can be immediately corrected before it exceeds the predetermined tolerances.

The liner may be cast in the stationary slip form simultaneously with the drilling operation. In this manner the bore hole is lined virtually as fast as it is drilled. When this is done, it is desirable to utilize the weight of the cast reinforced concrete liner to provide the thrust for the rotary drilling apparatus. Means for doing this are shown in FIGURES 3 and 4. To bore even moderately hard rock efficiently with rolling cutters requires a large downward force. Ordinarily this is supplied by heavy weights positioned just above the cutters or by thrust cylinders acting against wall jacks.

Referring to FIGURES 3 and 4 there is shown the bottom end of a hole or shaft 10B being drilled. This shaft is lined with a reinforced concrete liner 19C cast in stationary slip forms at the surface and provided around its periphery with a plurality of centralizers or bumpers 41A. A rotary drilling means is clamped to the bottom end of the liner 19C. The drilling means comprises a bit body 50 having an upwardly extending axial stem 51 and a downwardly extending pilot stem or stinger 52. This latter is engaged by a smaller diameter bore hole 53 to insure alignment of the bit.

The bit stem 51 rotates within tubular drill stem 54. A clamping ring 55 is secured to the lower end of drill stem 54 spaced upwardly from the bottom thereof. The clamping ring 55 has an outer peripheral groove or channel 56 of substantial width and depth into which is fitted an inflatable resilient tube or ring 57 formed of rubber or the like. Inflatable ring 57, when inflated, serves to clamp the bit means securely to the bottom end of the liner.

The bottom end of drill stem 54 is provided with a flange 58 which bears against the top of the bit body 50. A cutter platform or table 59 in the form of a ring is supported on top of flange 58 for rotation relative to the drill stem and shaft liner. The cutter table 59 is rotated by one or more hydraulic motors 60 fitted with pinions 61 engaging a ring gear 62 secured to the platform. Thrust is applied to the bit at two points, by the flange 58 at the bottom of the drill stern and through the motor and pinion to ring gear 62. In order to evenly distribute this thrust, it is preferred that a plurality of motors and pinions be arrayed uniformly around the periphery of the ring gear.

A plurality of small roller cutters 63 are supported under the bit body and journaled in brackets 64-67 for rotation as the bit is rotated. A large roller cutter 68 which undercuts the bore hole below the end of liner 19C is journaled for rotation in a pivoted frame or bracket 69. Frame 69 is in the form of a heavy plate pivoted to the bit body by a pin 70 and movable in a slot or channel 71 in the bit body. The outer end of slot or channel 71 is considerably wider at 72 to accommodate movement of the larger roller cutter 68 when the frame 69 is pivoted upwardly, as described hereinafter, for retraction so that the bit may be hoisted through the liner. In order to impart the rotation of the cutter table 59 to the roller cutters, the bottoin edge of the cutter table is provided with downwardly depending lugs 73 which engage the large cutter frame 69.

In order to permit retraction of the large undercutter, a link means 74 is provided. One end of link 74 is pivotally connected at 75 to the frame 69 for the large roller cutter 68. The other end of link 74 is pivotally connected at 76 to a lug on the bottom side of the cutter table 59.

As shown in FIGURE 4, if for any reason it becomes necessary to retract the bit, for example, for repair or replacement of parts or the like, the inflatable ring 57 is deflated in order to release the rigid connection between the bit means and the liner. Then the entire bit structure may be hoisted up through the liner. As the drill stem 54 is retracted, the clamping ring and associated structure attached to the drill stem is raised. The cutter table 59 is raised by virtue of flange 58 at the bottom of the drill stem. As the cutter table is lifted, force is exerted through link 74 to cause roller cutter 68 and its frame 69 to pivot on the pin 70. Then with the large cutter in this retracted position the bit may be hoisted up through the liner.

The motor 60 is preferably a mud turbine driven by drilling liquid forced under pressure from the surface. The exhaust from this motor means is then utilized to carry cuttings from the roller cutters to an annular pan or tray 78 supported on top of the clamping ring and adapted to be hoisted to the surface and emptied as required. The liquid to drive the motor may be pumped through conduits through the drill stem to the motor, conveyed through other conduits to the vicinity of the roller cutters and then forced upwardly along with the entrained cuttings for discharge into the cutting tray A plurality of groups of large and small cutters are arrayed about the periphery of the bit in order to distribute the thrust and cutting action. While the cutters are shown as if all of their axes lie in a single plane, they are preferably staggered with respect to one another. While the use of the reinforced concrete cast liner to apply thrust to the bit structure is shown with respect to a specific form of bit, it is to be understood that a number of different rotary bit means having retractable undercutters are known and are adaptable for use in conjunction with the liner.

In order to anchor the liner against rotation, some means must be provided by which the liner may be held. One manner of doing this is to cast flutes or splines in the outside of the liner as it is cast in the stationary slip form at the surface. A ring correspondingly fluted is fixed to the shaft walls near the surface but spaced some distance below it such that by the time the liner has reached the ring it will have acquired sufficient strength to withstand shearing off of the flutes or splines.

As one example of the use of the shaft lining system of the present invention, a shaft of 500 foot depth and 20 foot diameter is lined with a cast reinforced concrete tube 16 inches thick. The perimeter of the liner is approximately 63 feet. A total of 95 vertical reinforcing rods are set around the periphery of the liner spaced approximately 8 inches apart. The concrete has a weight of about 60 pounds per cubic foot under mud. The reinforcing rods are supported by jacks which carry the weight of the liner until it comes to rest at the bottom of the shaft. By multiplying the perimeter of 63 feet by the thickness of 1.33 feet, by the weight of the concrete of 60 pounds per cubic foot, by the 500 foot length of the liner, the total weight is calculated at approximately 2,520,000 pounds or 1,260 tons. This weight is carried by 95 rods and jacks so that each carries 26,500 pounds or 13% tons. This is well within the capacity of available equipment. It must be remembered that the bore hole will normally be full of drilling mud whose function is to support the walls of the hole until the casing is set. This mud assists in 8 supporting the liner and the Weight to be supported can be reduced further by the use of floats or a bulkhead in the liner or by using heavy mud and lightweight concrete.

As a further example, a shaft of 20 foot diameter and 1,000 foot depth is provided with a liner having 20 inch thick walls cast in stationary slip forms using 140 pound per cubic foot concrete. This shaft liner is formed with a water tight bottom bulkhead. The bore hole is filled with drilling mud having a weight of 75 pounds per cubic foot. The shaft is lowered through the mud by adding water to the inside of the concrete casing. At 1,000 feet depth the weight of the shaft liner and the water inside just balances the 1,000 foot depth of drilling mud outside. When this casing is filled with water, the differential pressure at the bottom results in a compressive unit stress (hoop stress) of only 282 pounds per square inch. By proportion we see that concrete feet from the surface is stressed at 28 pounds per square inch.

Taking another example, a 10 foot diameter shaft having a depth of 1,500 feet is lined with a cast concrete tube having 16 inch wall thickness throughout. This liner is formed with a bottom bulkhead and is filled with water as necessary to take the casing down. Using a drilling mud of 74 pounds per cubic foot, when the water level inside the casing is 605 feet below the surface, the outside pressure is 315 pounds per square inch and the compressive stress in the wall is 1,500 pounds per square inch at the water level. The development of adequate compressive strength in the liner to withstand such stresses presents no problem.

When the vertical reinforcing elements are composed of reels of high tensile strength steel wires, each fed over a head sheave or steel ring down through adjustable dies to restrain movement of the wire and thence into the concrete, the weight which can be supported by each Wire can be readily calculated and the need for additional support determined. For example, Where each wire is of inch diameter and can work at 100,000 pounds per square inch, each wire can support about 2,760 pounds.

Similarly, where high strength steel cable, either plain or galvanized, is fed from reels over a ring or sheaves down through cable jacks and into the concrete, the weight which can be supported by each cable can be determined. For example, taking galvanized steel bridge strand and assuming a safety factor of two, each 1 inch cable can support 30 tons.

Whether rods, wires, or wire rope are used as the vertical reinforcements, the cylindrical concrete tube is prestressed vertically by the tension automatically built into this support. This'prestressing becomes effective as soon as the lower end of the liner rests on the shaft bottom and so supports the weight of the concrete. It binds the concrete shell together and provides exceptional resistance to any unequal horizontal stresses.

It is apparent that many modifications and variations of this invention as hereinbefore set forth may be made without departing from the spirit and scope thereof. The specific embodiments described are given by way of example only and the invention is limited only by the terms of the appended claims.

We claim:

1. A system for lining a deep large diameter vertical hole bored into the surface of the earth which comprises casting a reinforced tubular casing in situ over said hole at the mouth thereof and progressively lowering said casing as formed into said hole until said hole is lined to the desired depth, said system comprising the steps of:

(A) supporting over the mouth of the hole to be lined tubular vertical uniformly spaced apart stationary forms defining the wall thickness of said casing,

(13) inserting the ends of a plurality of strong continuous metal strand vertical reinforcing elements between said forms uniformly spaced about the pe riphery of the forms from supply sources above the 9 mouth of the hole and anchoring the strands in a removable ring at the bottom of said forms,

(C) placing concrete -mix between said forms about said reinforcing elements to embed the same,

(D) leaving said concrete mix undisturbed between said forms until set up and hardened into a tubular casing,

(E) lowering said ring from the bottom of said forms a distance less than the length of the thusly formed casing segment, at least part of the suspended weight of said casing segment being supported by said reinforcing element to progressively insert further lengths of reinforcing elements and to maintain the strands thereof under constant substantially uniform tension to stress the same, and

(F) progressively placing further concrete into the top of said forms and progressively discharging tubular casing from the bottom thereof at a rate to permit the concrete mix to become set and hardened in the course of its passage through the forms.

2. A system according to claim 1 further characterized in that said casing is thereafter set in said hole by filling the space between the wall of said hole and the outer wall of said casing with a settable material.

3. A system according to claim 1 further characterized in that said tubular casing is supported in part by drilling liquid in said hole to be lined as the casing is lowered therein.

4. A system according to claim 3 further characterized in that the bottom end of said casing is closed to render said casing buoyant to facilitate support thereof by drilling liquid.

5. A system according to claim 1 further characterized in that annular horizontal reinforcing elements are incorporated in said casing spaced longitudinally along the length thereof, said horizontal reinforcing elements I being added progressively to said casing as formed.

6. A system according to claim 1 further characterized in that a sealant coating is applied to the outside of said tubular casing progressively as said casing is formed.

7. A system according to claim 6 further characterized in that said sealant coating is applied to said casing from a layer of sealant material floating on top of drilling liquid disposed in the space between the bore hole wall and easing as the casing passes downwardly through the floating layer.

8. A system according to claim 1 further characterized in that said tubular casing is cast substantially simultaneously along with deepening of the hole, the weight of the formed casing exerting the thrust for further boring.

References Cited by the Examiner UNITED STATES PATENTS 887,952 5/1908 Milligan 61-41 X 1,175,952 3/1916 Haase -97 1,574,040 2/1926 Lasher 166-24 X 1,847,814 3/1932 Byrne 6141 1,916,686 7/1933 Sandstone 166--24 2,080,406 5/1937 Allen 166-24 2,706,498 4/1955 Upson 61-56 X FOREIGN PATENTS 729,724 1932 France.

892,734 5/ 1944 France.

257,682 1913 Germany.

1,120,402 12/ 1961 Germany.

CHARLES E. OCONNELL, Primary Examiner.

JACOB SHAPIRO, Examiner.

C. D. JOHNSON, Assistant Examiner.

Claims (1)

1. A SYSTEM FOR LINING A DEEP LARGE DIAMETER VERTICAL HOLE BORED INTO THE SURFACE OF THE EARTH WHICH COMPRISES CASTING A REINFORCED TUBULAR CASING IN SITU OVER SAID HOLE AT THE MOUTH THEREOF AND PROGRESSIVELY LOWERING SAID CASING AS FORMED INTO SAID HOLE UNTIL SAID HOLE IS LINED TO THE DESIRED DEPTH, SAID SYSTEM COMPRISING THE STEPS OF: (A) SUPPORTING OVER THE MOUTH OF THE HOLE TO BE LINED TUBULAR VERTICAL UNIFORMLY SPACED APART STATIONARY FORMS DEFINING THE WALL THICKNESS OF SAID CASING, (B) INSERTING THE ENDS OF A PLURALITY OF STRONG CONTINUOUS METAL STRAND VERTICAL REINFORCING ELEMENTS BETWEEN SAID FORMS UNIFORMLY SPACED ABOUT THE PERIPHERY OF THE FORMS FROM SUPPLY SOURCES ABOVE THE MOUTH OF THE HOLE AND ANCHORING THE STRANDS IN A REMOVABLE RING AT THE BOTTOM OF SAID FORMS, (C) PLACING CONCRETE MIX BETWEEN SAID FORMS ABOUT SAID REINFORCING ELEMENTS TO EMBED THE SAME, (D) LEAVING SAID CONCRETE MIX UNDISTURBED BETWEEN SAID FORMS UNTIL SET UP AND HARDENED INTO A TUBULAR CASING, (E) LOWERING SAID RING FROM THE BOTTOM OF SAID FORMS A DISTANCE LESS THAN THE LENGTH OF THE THUSLY FORMED CASING SEGMENT, AT LEAST PART OF THE SUSPENDED WEIGHT OF SAID CASING SEGMENT BEING SUPPORTED BY SAID REINFORCING ELEMENT TO PROGRESSIVELY INSERT FURTHER LENGTHS OF REINFORCING ELEMENTS AND TO MAINTAIN THE STRANDS THEREOF UNDER CONSTANT SUBSTANTIALLY UNIFORM TENSION TO STRESS THE SAME, AND (F) PROGRESSIVELY PLACING FURTHER CONCRETE INTO THE TOP OF SAID FORMS AND PROGRESSIVELY DISCHARGING TUBULAR CASING FROM THE BOTTOM THEREOF AT A RATE TO PERMIT THE CONCRETE MIX TO BECOME SET AND HARDENED IN THE COURSE OF ITS PASSAGE THROUGH THE FORMS.

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