GB2136851A - Apparatus and methods of ground drilling - Google Patents

Abstract

A rotary ground drilling comprises a vertical leader (3) on which is guided a rotary-casing drilling unit (4, 5, 6,) suspended from a cable (43) passing over the top of the leader. The drilling unit comprises a driving source (4), a rotary casing (5) suspended from the driving source and rotated thereby, and a coaxial drill head (6) fixed to the bottom of the casing. In operation, the drilling unit excavates a hole while holding the excavated material in the form of a core and the material is lifted to the surface while being held within said casing. <IMAGE>

Description

SPECIFICATION Apparatus and method of ground drilling This invention relates to a means of and a method for excavating and removing obstacles, such as reinforcing bars, steel skeletons, rock strata, and so on during excavation.

Conventionally, for drilling a basic hole or providing a basic containing wall for the purpose of building a new structure, it is necessary to excavate the earth around obstacles buried in the ground and after removing all the earth surrounding the obstacles it is necessary to take out those obstacles.

Typically, the diameter of a basic hole or the thickness of a basic diaphragm wall or containing wall might be 600mm to 1 700mm.

As generally known engineering methods for deep excavation, there may be named, for example, the reverse boring methods, the boring machine method, the earth auger method, or the percussion boring method.

In the reverse boring method, the boring operation is carried on with the bit furnished on the head of the drill rod while the ground is kept soft by pouring water thereinto in such a manner that the hole may be kept filled to the brim with water from the start of boring; the resultant muddy water is removed and, after being filtered, is returned into the hole.

The reverse method, however, has such defects that the walls of the hole are prone to collapse on account of having become soft under the action of water, and further that it is impossible for drilling to continue if obstacles are met, e.g. in strata containing reinforcing bars, steel skeletons, rock bed, and so on.

In one rock-drilling method for strata containing the obstacles as described above, a boring operation is conducted while crushing the rock, the rotating boring bar being furnished at its end face with a plurality of bits similar in form to a bevel gear. The crushing operation requires a great deal of water in order to discharge the crushed earth as a slurry by the use of water circulating from outside, and brings the problem of diposing of the resulting slurry or sludge.

In addition, the use of this method has a weakness in that the boring operation is impractical in some concrete strata containing reinforcing bars or a steel frame because of the limitations of the strength of the boring bar.

On the other hand, the earth auger method conventionally used is not free from the shortcoming when drilling strata containing obstacles that the drill connot bear up against the torque of the driving source, on the one side, and the resistance of the obstacles, on the other, so that fracture may occur even when drilling a small diameter hole, thereby bringing the risk of a serious accident.

As for the percussion method, it also, like the boring machine method, has the fault that it is difficult for it to dispose of the excavated earth, and further it has no ability to crush reinforcing bars or steel frames left in the ground from a previous construction on that site.

It may also be noted that the present applicant has already filed a patent application (83.01466) describing an earth auger and a method of boring in obstacle-containing strata on Inline engineering method. That earth auger was arranged as a boring machine having a dead load about 100 ton and a jointing part able to transmit a high torque such as 1 50 to 360 H.P. so as to use sufficient propelling power to be able to penetrate the obstacle containing strata to a sufficient extent, while its drilling bits are formed in the respective unequal shapes so as to be able to adapt to any circumferential speeds.

The method according to this earlier invention for ground drilling has the ability to prevent the earth auger axle from crooking or bending and to protect thereby the wall of the bored hole from collapsing with the help of a fixed casing attached to the earth auger. As a result there is the possible drawback that the complete volume of the basic hole has to be drilled. One effect of this is that it is not possible to shorten the time it takes to bore a foundation hole.

One object of the present invention is to provide an earth auger which is able to excavate the earth for a foundation hole circumferentially.

A second object of this invention is to provide a method of excavation in ground having obstacles such as ferro-reinforced concrete, ferro-skeleton concrete, rock zones and the soft ground including rocks while holding the excavated material as a core and lifting it thus to the surface from the hole.

A preferred feature of the present invention is an exchangability of the method of excavation for the method of excavation with a rotary earth auger shaft such as is described in my earlier patent application. When the efficiency falls in the course of the drilling process using the earth auger, it may be arranged that there is an immediate changeover to the method of the present invention by exchanging the earth auger shaft for a ground drill according to the present invention.

By way of example, the invention will be described in more detail with reference to the accompanying drawings, in which: Figure 1 is a general side view of an earth auger or ground drill according to the invention; Figure 2 is a partial side view of a rotary casing for the drill in Fig. 1, and includes some detail sectional views of the casing; Figure 3(A) is an enlarged partial side view of the rotary casing head showing the connecting part of the rotary casing; Figure 3(B) is an enlarged side view of the fixing part on the lower portion of the casing head; Figure 3(C) is a partial view from below of the casing head; Figure 4(A) is a partial longitudinal section view of the vertical jack chamber of the auger in Fig. 1; Figure 4(B) is a partial longitudinal-section view of the horizontal jack chamber; Figure 4(C) is a cross-sectional view of the horizontal jack chamber;; Figure 5(A), (B), (C), (D), (E), are a series of illustrations explaining several examples embodied on the basis of the method according to the invention; Figure 6 is an explanatory drawing of the progress of drilling on the basis of the method according to the invention; Figures 7 and 8 are graphical illustrations of the progress of drilling by two different methods by way of comparison.

In Fig. 1, reference numeral 1 indicates a rotary-casing earth auger or drill which comprises a crawler 2 on endless tracks 21 and provided at its front with a mounting fork 22 for supporting a leader 3 vertically.

The leader 3 is erected vertically by being supported at its lower part 31 by the fork 22 of the crawler 2 and its middle part by two stays 32, thus, at three points in all.

A sheave cradle 33 provided at top part of the leader 3, has at its forward end a rotatable top sheave 34.

Guide tubes 35 are arranged extending over the whole length of the leader in the axial direction. There may be two or more of these guide tubes arranged parailel to each other.

The leader 3, which is long and cylindrical, as shown in Fig. 1, can be extended to any length by connecting any number of flanges one to another in series corresponding to the required depth to be drilled.

A driving source 4 comprises a motor, which is supported by a supporting frame 41 on which a sheave 43 is mounted rotatably.

Sliding pieces 42 are attached to the supporting frame 31 at its side part facing the leader 3. The sheave 43 is suspended from the above mentioned top sheave 34 by means of a cable.

On the other hand, the sliding pieces 42 are engaged with the guide tubes 35 of the leader. As a result, the whole body of the driving source 4 is slidable along the leader 3.

Numeral 5 indicates a rotary casing, which is formed from a number of casing units having a unit length (1) of about 5 to 10m.

Each casing unit is provided with several axially directed bolt holes 54 bored at regular intervals at its both end parts on the centre circle line of its wall thickness 51. Bolt-setting windows 55 are provided at the end parts of the casing at the respective bolt holes 54.

In each casing unit is embedded an oil-feed pipe 52 and a push pull oil pipe arrangement 56 within its own wall thickness 51 in the axial direction.

At the time of abutting the end faces of two casing units together, an O-ring 57 is interposed between the contacting faces of said oil-feed pipes 52 and said push pull oil pipe arrangement 56, and the required number of bolts 59 are passed through the corresponding bolt-setting windows. Thereby several casing units are interconnected one to another to obtain a casing of a required length, while the upper end part of said casing 5 thus obtained is connected through an adapter 58 to said driving source 4 and the lower end part of it is connected to a casing head 6.

The casing head 6 is made of steel in the form of a cylinder and has a number of bits 61 studded at several places of its lower part at an angle of inclination 8 to the axial direction (1), and a pressure liquid nozzle 62.

A liquid-feed pipe 52 communicating with said nozzle 62 is embedded within the thickwalled part 51, a number of radially directed bolt-setting windows 55 are formed in the casing head upper part facing said casing 5, and a corresponding number of bolt holes 54 are formed through the end faces of said boltsetting windows 55 in the wall-thickness in the axial direction.

Said bolt holes 54 and said liquid-feed pipe 52 are linked in said casing wall.

An O-ring 63 is required between said liquid-feed pipe 52 and said nozzle 62 when said casing head is bolted to the casing 5.

The bits 61 are embedded in the lower part of said casing head 6 and are provided at their base parts 611 with fitting portions 61 2 of U-shape in side view.

Each bit 61 of the casing head 6 is bolted detachably in a fitting portion 61 3 of M-shape having a bolt hole 615 and a kept setting window 614 at the insertion place of the bit 61.

Numeral indicates a steady rest member which is fitted on said guide tubes 35 at the side of the leader 3. The steady rest member 7 is slidable along said guide tubes 35 and surrounds the outer circumference of the casing.

Numeral 9 indicates a jack chamber, jack chamber 92 wherein an enagagement mechanism extending in the tangential direction (r) of the casing 5 comprising an oil cylinder 93 and a number of pawls 95 or link mechanisms 94 is positioned within the wall thickness of the casing tube above the jointing part of the casing head 6 with said casing 5.

A swivel joint is fixed fast on the central part of a supporting frame body 43 of the driving source 4, of which the one pipe communicates with a pressure-feed means, and the other with said liquid-feed pipe 52 of the casing 5.

Using the auger or drill as set forth above a method for excavating and removing an obstacle in the ground is, according to Fig.

5(A) to Fig. 5(B), impinging said casing head 6 on the surface 11 of the ground predeter mined to A method for excavating and removing an obstacle such as rock, reinforcing rods, steel skeletons or others is accordingly shown in Fig. 5(A) to Fig. 5(E) in the following steps.

A first step is impinging the casing head 6 on the ground surface 11 at the predeter mined position to excavate a foundation hole at the site of an obstacle 10 in the ground.

The next step is activating the driving source 4 in such a state as above to give a rotating excavation force to the casing 5, and the descent thereby of the casing 5 under the guidance of the leader 3 and continuing to excavate the hole around its circumference while holding the excavated earth as a core.

In the case of the need of protecting the wall of the hole or at the time of adding high pressure water jets in order to complement the excavation force, stabilizing liquid or highpressure jet water is fed from the casing head nozzles 62 via the liquid-feed pipe 52 into the interior of the casing.

The casing 5 is in due course raised from the foundation hole under the guidance of the leader 3 after excavating to a required depth (D), and withdrawing said casing 5 up to the ground surface 11.

If the excavated core 1 2 of earth tends to drop into the hole whereby the water flow penetrates into the casing 5, the pawls 95 or link mechanism 94 are projected into the casing 5 in the radial direction to be pushed into the excavated core 12, and so carry out the excavated earth being held within the casing as far as the ground surface.

After that, with the casing 5 over the ground surface away from the excavated hole, the excavated core is removed from the casing 5 by the use of some auxiliary means 14, or by vibrating the casing and so on.

Examples of the use of the invention will now by described in the following; A foundation hole of 0.8m in diameter and 5m in depth was bored at a site consisting of soft ground and obstacle-containing ground, as shown in the sectional view of geological strata in Fig. 6, which more precisely, is composed from top to bottom successively of a soft stratum of fill-up ground, pebbles, and pebble-clay mixed layer from the surface to the depth of 1.8m, a ferro-reinforced concrete layer from 1.8m to 3.5m, and a weathered rock layer from 3.5 to 5.0m.

Example 1 The bore was made at the above mentioned ground using the auger or drill described above.

The bits 61 were made using a metal having a specified hardness (Rockwell A) of 86 to 90 HRA, a defective strength of 300 to 340Kg/mm2, and tenacity of 50 to 60Kg/mm3/2. The weight of this apparatus is 40 to 50 tons, further including the crawler 100 tons.

The result was that the required time was 60 minutes, as shown in the graph of the drilling speed in Fig. 7.

Example 2 The same ground as above was bored by the use of an earth auger according to the earlier patent application referred to above, when it took 123.5 minutes, until the finish of work, as shown in the graph in Fig. 8.

To summarise, therefore, there has been described a rotary-casing auger or ground drill, which comprises the following structural components: (a) a crawler supporting a leader vertically by a catch fork which is provided on the front part of said crawler.

(b) a long cylinder-shaped leader which is erected vertically being supported at its lower part by said crawler and at its middle part by two propping legs, has a sheave cradle on its top end with a top sheave fixed fast thereon, and is furnished with a slide pipe (guide means) extending by its flank in the axial direction; (c) a driving source, which has a sheave fixed fast on its top part and has sliding pieces attached to its side part facing to said leader; wherein said sheave and said top sheave of the leader are suspension-connected to each other by means of wire, and said sliding pieces engage slidably with said slide pipe running by the side of and along said leader; (d) a tubular casing, wherein first a unit casing is made by being provided with several bolt holes bored at regular intervals at its both end parts piercingly in the axial direction on the centre circle line of its wall-thickness; next wherein said unit casing being of the unit length of 5-10m and being made of steel in the form of a cylinder, and embedding a liquid-feeding pipe and a push-pull oil pipe arrangement within its own wall-thickness in the axial direction; then wherein so many boltsetting windows are made piercingly at the end parts of said respective bolt holes in the radial direction of said unit casing; and lastly wherein, at the time of abutting both end faces of one unit casing and the other unit casing to each other, an O-ring is interposed between the contacting faces of said liquidfeeding pipe and said push-pull oil pipe arrangement, and each of a required number of bolts is made to pierce through the corresponding bolt-setting windows, and thereby several unit casings are interconnected one by one to obtain a casing of a required length, while the upper end part of said casing thus obtained is connected through an adapter to said driving source and the lower end part of it is connected to a casing head;; (e) the casirig head, being made of steel in the form of a cylinder and having a number of bits studded at several places of its lower part at an angle of inclination 8 to the axial direction and a pressure liquid nozzle, wherein a liquid-feeding pipe communicating with said compressed-liquid nozzle is embedded within the thick-walled part, a number of bolt-setting windows are formed by being bored piercingly in the radial direction so as to be provided at its upper part facing said casing, and so many bolt holes are formed while piercing through the end faces of said bolt-setting windows in the wall-thickness in the axial direction, whereupon said bolt holes and said liquid-feeding pipe are linked to said bolt holes and said liquid-feeding pipe of said casing correspondingly, and are abutted against and boltconnected to the under face of said casing through the interposition of an O-ring between said liquid-feeding pipe of said casing head and that of said casing; (f) a jack chamber, wherein an engaging mechanism consisting of a hydraulic jack and a number of pawls is loaded within the wallthickness of said casing tube above the jointing part of said casing head with said casing in the tangential direction of said casing; said hydraulic jack communicating with said push-pull hydraulic casing; and said pawls being fixed fast on the tip of the rod of said hydraulic jack; (g) a steady rest member being fitted on said slide pipe by the side of said leader, being slidable along said slide pipe, and surrounding the outer circumference of said casing; (h) a swivel joint being fixed fast on the central part of a supporting frame body of said driving source, of which the one pipe communicates with a pressure-feeding means, and the other with said liquid-feeding pipe of said casing, respectively.

There has also been described a rotarycasing method for excavating and removing an obstacle, which comprises: using said rotary casing earth auger as set forth above; impinging said casing head on the ground surface predetermined to excavate a foundation hole at an obstacle including rock, reinforcing rods, steel skeleton or others; activating said driving source in such a state as about to give the rotating excavation force to said casing; descent thereby of said casing under the guide of said leader and continuing to excavate the obstacle ground while holding the excavated earth in a core state as it is;; feeding stabilizing liquid or high-pressure jet water from said casing head nozzles through said liquid-feeding pipe into the interior of said casing, for example, in the case of the necessity of protecting the hole-wall or at the time of adding high-pressure jet water in order to complement the excavation force; raising said casing from said foundation hole under the guidance of said leader after having excavated to an expected depth, and withdrawing up said casing to the ground surface; making said pawls project within said casing in the radial direction, dash into the corelike excavated earth, and carry out the excavated earth being held within said casing as far as the ground surface; placing said casing on the surface of the ground outside the excavated hole; and taking out the core-like excavated earth from said casing by the use of some auxiliary means, otherwise by vibrating said casing and so on.

Claims (8)

1. A ground drill which comprises: (a) a crawler supporting an elongate leader by means provided on the front part of said crawler, (b) the leader being arranged to be supported upright by engagement of its lower part by said crawler and of its middle part by stay means, and having a suspending sheave on its upper end, and guide means extending in the axial direction along the leader, (c) a driving source, arranged to be suspended by said sheave and be slidably guided by said guide means, (d) a casing comprising a plurality of hollow cylindrical units secured together end to end, the walls of said units containing a liquid-feed conduit and a push-pull pressure-fluid conduit arrangement, the conduits continuing through the respective casing units with sealing means between adjoining sections of the conduits at the facing ends of successive casing units, and the upper end of said casing being connected to said driving source and the lower end to a casing head, (e) the casing head, being in the form of a cylinder and having a number of bits inclined to the axial direction at spaced positions on its lower part and a pressure liquid nozzle com municating with said liquid feed conduit, (f) at least one jack chamber in the casing wherein an engaging mechanism is contained within the casing wall thickness and communicating with said push-pull pressure-fluid ar rangement, said mechanism comprising at least one element arranged to be projected inwardly of the casing wall, (g) steady rest means slidable on said guide means of the leader and surrounding the outer periphery of the casing, (h) a swivel joint being fixed fast on a supporting body of said driving source, and providing supply connections for a pressurefluid feed means, and for said liquid-feed pipe of said casing.

2. A ground drill according to claim 1, wherein said bits in the casing head each have a fitting portion which is U-shape in side view, and are bolted detachably to the casing head in respective fitting seatings of M-shape in side view.

3. A ground drill according to claim 1 or claim 2, wherein said jack chamber is furnished with an engaging mechanism in the axial direction.

4. A method of ground drilling for excavation and removing a core of material, using an auger according to any one of the preceding claims, comprising rotating the casing by activating the driving source to allow the casing head to penetrate into the ground under the guidance of the leader and continuing to bore into the ground while holding the excavated material as a core, feeding stabilizing liquid or high-pressure jet liquid from the casing head through said liquid-feed conduit into the interior of said casing, raising said casing from the drilled hole under the guidance of the leader after having excavated to a required depth, projecting said jack mechanism element or elements inwardly to force said element or elements into the excavated core to hold the core within said casing, and discharging the core from the casing after moving the casing away from the drilled hole.

5. Apparatus for ground drilling comprising an elongate hollow cylindrical casing, with a circumferential wall, means at the lower end of said casing wall for cutting a ring-form drilling in which the casing can follow, said circumferential wall containing engagement elements that are displaceable inwardly of the wall to retain in the casing the core of excavated material within said ring-like drilling.

6. A method of ground drilling in which a hollow cylindrical casing is otated about its axis to form a corresponding ring-like drilling in the ground, the core of material within said drilling being retained in the casing by engagement elements that are moved between retracted positions within the thickness of the casing circumferential wall and engagement positions projecting inwardly from said wall into the core, the retained core being released from the hollow casing after raising it and moving it away from the drilling.

7. Apparatus for ground drilling constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.

8. A method of ground drilling substantially as described herein with reference to the accompanying drawings.