JPH0384115A - Excavated casing - Google Patents

Abstract

PURPOSE:To prevent an excavated hole wall from collapsing by providing casings having turning grooves and a compaction section to the peripheral surface to joints of normal casings, and providing also a turning groove and compaction section to a cutting head of the furthest tip. CONSTITUTION:When a plurality of normal casings 2 are connected to each other, turning grooves 20 and a longitudinal groove 23 are provided to the peripheral surface to lie a connecting shorter casing 18 forming a compaction section 21 between the normal casings 2 properly. In addition, a turning groove 6 formed of a projected thread 5 on the peripheral surface and a compaction section 7 projected to the outside slightly from the casings 2 are formed on the cutting head 1. A hole-wall is consolidated double and triply with the cutting head 1 and the connecting shorter casing 18. According to the constitution, even the collapse of an excavated hole having a greater depth is prevented and, at the same time, a water impermeable layer is so formed that a cast-in- place pile can be driven even if the speed of a current of the underwater is speedy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an excavation casing for constructing large diameter cast-in-place piles.

[Conventional technology]

In the construction of cast-in-place piles, the all-casing method is known, in which the inside of the casing is excavated with a drilling machine such as a hammer grab or drop hammer while the casing is being erected.
The Benotoe method is one of them.

In this Benotoe method, the casing is erected into the ground by shaking it, but since the casing itself does not have the ability to cut and crack boulders or bedrock, a drilling machine such as a drop hammer is inserted in advance of the casing, making it easier to dig. After creating the condition, the tip of the casing is press-fitted into it.
It is necessary to replace the drilling machine, such as using a separate hammer grab to discharge small pieces of boulders, etc. Not only is the workability extremely poor, but it is also necessary to use a hammer in ground where the groundwater flow rate is over 100 m/h. Preliminary excavation with a grab caused the ground to collapse, making it impossible to insert the casing, making it impossible to excavate. Even if excavation is possible, ready-mixed concrete cannot be poured in because it will be washed away by groundwater.Additionally, preliminary excavation using a hammer grab may cause the hole wall to collapse, which may lead to underground formation. For this reason, it was highly dependent on the presence or absence of groundwater.

Therefore, the inventor installed a cutter bit at the tip of the casing as an excavation method that was completely unaffected by the presence or absence of groundwater.
By appropriately selecting the casing's rotational speed, surface pressure, bit shape and angle, the casing itself has the ability to cut through rock and boulders, and this construction method uses a hammer grab, etc., to discharge earth and sand while the casing is in front. ) has been devised and implemented.

The most important point in this construction method is how to form the stratum around the casing into an impermeable layer.
Previously, the present inventor filed Utility Application No. 57-185595
9-89188), the earth and sand excavated at the tip of the casing is pushed out to the outer periphery of the casing, and the outer ground is consolidated to near the consolidation limit of each stratum using protrusions formed along the entire length of the casing body, reducing the void ratio. We proposed a method that forms an impermeable layer.

However, in this Japanese Utility Model Application No. 57-185595, the consolidation wall is formed over the entire length of the casing body, which may cause increased frictional resistance during excavation.

Therefore, the present inventor proposed a cutting head that fits into the tip of the casing and is fixed with bolts in Japanese Patent Application No. 62-125533 (Japanese Unexamined Patent Publication No. 63-289114).
We have proposed a structure in which a cutter bit is disposed on the lower end surface, and the outer circumferential surface is divided into a vertical turning groove forming section and a thick rolling section.

According to this cutting head, when the casing is rotated and erected, the earth and sand scraped by the cutter bit on the lower end of the head is pushed out to the outside of the head, and some of it is pressed against the hole wall by the rolling part on the outer circumferential surface. Consolidated. In addition, the remaining earth and sand are guided by the grooves of the swirl groove forming part and rise, and are consolidated on the hole wall by the rolling part.

By compacting the hole wall in this way, friction on the casing circumferential surface is eliminated.

[Problem to be solved by the invention]

The cutting head disclosed in Japanese Patent Application No. 62-125533 is quite effective when the entire casing is relatively short, but in order to perform deep excavation, a large number of casings are added in the length direction to make the entire casing longer. When forming a casing, there is a risk that the hole wall compacted by the cutting head may deteriorate and the desired effect may not be expected.

SUMMARY OF THE INVENTION An object of the present invention is to provide an excavation casing which eliminates the disadvantages of the conventional examples and which can sufficiently consolidate the hole wall and effectively form an impermeable layer even when excavating at great depths.

[Means to solve the problem]

In order to achieve the above object, the present invention provides vertical turning grooves and thick rolling sections on the outer circumferential surface at appropriate locations of the connections when a plurality of rotatable normal casings are connected in the longitudinal direction. A short connecting casing with a fitting joint to the normal casing is interposed at the upper and lower ends, and a thick rolling groove is formed on the outer peripheral surface of the connected normal casing at the bottom end with a vertical turning groove forming part. The gist is that the casing is divided into two parts, a fitting joint to the normal casing is provided at the upper end, and a cutting head of a short casing having a cutter bit is provided at the lower end.

[Effect]

According to the present invention, when the casing is rotated and erected, the earth and sand scraped by the cutter bit on the lower end of the cutting head is pushed out to the outside of the head, and some of the earth and sand is pressed against the hole wall by the rolling part on the outer circumferential surface. Consolidated. In addition, the remaining earth and sand are guided by the grooves of the swirl groove forming part and rise, and are consolidated on the hole wall by the rolling part.

In this way, the cutting head first consolidates the hole wall, thereby eliminating friction on the casing peripheral surface.

On the other hand, as the casing is excavated, the entire casing is erected into the ground, and the compacted area at the cutting head moves to the middle part of the casing, where it deteriorates and collapses.

On the other hand, when the part with the short connecting casing comes to that location, the collapsed soil is pushed out to the outside of the casing by the swirl groove, and some of it is pierced by the rolling part on the outer circumferential surface, similar to the cutting head. The remaining earth and sand are guided into the grooves of the swirl groove forming section and rise up, compacted against the hole wall by the rolling compaction section, reinforcing the hole wall again, and in the same way, the remaining earth and sand are introduced into the grooves of the swirling groove forming section, and are compacted onto the hole wall. The hole walls of the casing are also reinforced,
A consolidated wall can be reliably obtained throughout the entire length of a deep excavation hole.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a partially cutaway front view showing one embodiment of the excavation casing of the present invention. In the figure, 2 is a normal casing made of steel pipes, which are connected in plural in the length direction.

When connecting a plurality of normal casings 2 in this manner, the present invention interposes short connecting casings 18 at every second or third connection point.

As shown in FIGS. 2 and 3, this short casing 18 for connection is provided with a male fitting joint 19a and a female fitting joint 19b to the normal casing 2 at the upper and lower ends, and the outer peripheral surface is connected to the upper and lower ends. It is divided into a turning groove 20 in the direction and a thick rolling part 21. In the figure, 22 indicates bolt holes formed in the fitting joints 19a+19b.

The connecting short casing 18 has the same outer diameter as the normal casing 2 except for the rolling part 21, and the rolling part 21 is made thicker so that it protrudes slightly outward from the normal casing 2. and the edges are tapered.

Furthermore, the swirl grooves 20 are simultaneously formed between the rectangular rolling portions 21 by forming them at intervals in the vertical direction.

Further, the rolling portions 21 are formed at intervals in the circumferential direction of the short casing 18, and a vertical groove 23 intersecting with the swirl groove 20 is provided between them.

In this way, two or three of the normal casings 2 are
In this case, this connection short casing 18 is used for connection, and other connections are made normally, but the arrangement of the connection short casing 18 and the shape of the compaction part 21 etc. depend on the depth of excavation and the condition of the strata. You can select as appropriate.

Further, the cutting head 1 is fitted to the tip of the connected casing 2 and fixed with bolts.

As shown in FIG. 4, the cutting blade 1 has a fitting joint 3 for a normal casing 2 at its upper end, a cutter bit 4 is implanted at its lower end, and a protrusion 5 in a recess on its outer circumferential surface. It is divided into a swirl groove forming part with a swirl groove 6 between them and a rolling part 7 which is thick and slightly protrudes outward from the casing body 2. In the illustrated example, this swirl groove forming part and rolling A pair of portions 7 were formed to face each other.

The rolling section 7 has a cross-sectional shape that is tapered in the direction of rotation and has a tapered surface 7a, so that the excavated soil can be pressed outward by rotation through this tapered surface 7a. It is.

Some of the protrusions 5 are cut in the middle to form horizontal grooves 8 through which gravel and the like can escape.

Next, how to use it will be explained.

FIG. 5 shows the state of use, and 10 in the figure is a casing erection machine, in which a casing driving unit 15 consisting of a motor 12, a reducer 13, and a casing chuck mechanism 14 rotated by these is moved to a league mast by an elevating jack 16. 11 so that it can be raised and lowered freely.

Note that this casing erection machine 10 is not a base machine type having a moving mechanism, but may be a stationary type, and may be of a stationary type, and the lifting jack 16 is used as a leg.

When the casing 2 etc. are set in the casing drive section 15 of the casing erecting machine 14 so that the outer periphery of the casing 2 etc. is fixed by the chuck mechanism 14, and the motor 12 is started, the chuck mechanism 14 is moved through the reducer 13. The rotating casing 2 held by the chuck mechanism 14, the connecting short casing 18, and the cutting head 1 at its tip.
It also rotates slowly in one direction.

The dirt and stone chips cut by the cutter bit 4 at the tip are pushed out to the outside of the head 1, and some of them are compacted into the hole wall by the rolling part 7 of the head 1. Further, the remaining earth and sand rises along the swirl groove 6 and is compacted onto the hole wall by the rolling section 7.

The lifting jack 16 is free, and as the head 1, casing 2, etc. are built into the ground in this way, the casing drive unit 15 also descends due to its own weight, but when it reaches the lowest position, the chuck mechanism is loosened once, the lifting jack 16 is extended to push up the drive unit 15, and the upper part of the casing 2 etc. is fixed again with the chuck mechanism 14, and the same operation is repeated.

On the other hand, an excavator 17 such as a hammer grab or other excavation packet is suspended from above into the casing 2 to excavate and remove the earth and sand cut into rings within the head 1.

To further explain the consolidation of the hole wall, since the cutting head 1 is connected to the tip of the casing 2, etc., a portion of the earth and sand cut by the cutter bit 4 is immediately consolidated into the hole wall.

Normally, the void ratio is about 60 to 70% for loam layers, about 35 to 45% for sand layers, and about 25 to 35% for gravel layers, but according to cutting head 1, each layer is consolidated close to the consolidation limit. , which can lower the void ratio and form an impermeable layer.

On the other hand, as the casing is being excavated, the entire casing is erected into the ground, and the consolidated part of the cutting head 1 moves to the middle part of the casing, and when it rubs against the casing 2, it deteriorates and collapses.

On the other hand, when the part of the short connecting casing 18 comes to that location, the collapsed earth and sand are pushed out of the casing 18 by the turning groove 20, similar to the cutting gear 1, and a part of it is pushed out around the outer periphery. It is again consolidated into the hole wall at the surface rolling part 21. Further, the remaining earth and sand are guided into the swirl groove 20 and ascend, and are compacted onto the hole wall by the rolling compaction section 21, thereby reducing the void ratio of the soil and reinforcing the hole wall.

Similarly, the hole wall is reinforced in the short connection casing 18 above it, and in this way, it is divided into several stages, double layered,
By consolidating the hole wall in three layers, a consolidated wall can be reliably obtained over the entire length of the hole, even in a deep excavation hole.

〔Effect of the invention〕

As described above, the drilling casing of the present invention reliably consolidates the hole wall over the entire length of the drilling hole, even when forming a deep drilling hole in which multiple rotatable regular casings are connected longitudinally. This completely prevents the collapse of the hole wall, eliminates friction on the casing surface, and forms an impermeable layer, making it possible to construct cast-in-place piles even in areas where underground water flows quickly. .

[Brief explanation of drawings]

Fig. 1 is a partially cutaway front view showing one embodiment of the excavation casing of the present invention, Fig. 2 is a side view of a short casing for connection, Fig. 3 is a cross-sectional plan view of the same, and Fig. 4 is a view of the cutting head. Side view, FIG. 5 is a side view showing the state of use. 1... Cutting head 2... Normal casing 3... Fitting joint 5... Projection 7... Rolling section 8... Lateral groove 10... Casing erecting machine 11... League Mast 12...Motor 13...
・Deceleration l1114...Chuck mechanism 4...Cutter bit 6...Swivel groove 7a...Tapered surface 15...Casing drive unit 16...Elevating jack 17...Excavator 18...
・Short casing for connection

Claims (1)

[Claims] When connecting multiple rotatable normal casings in the length direction, vertical turning grooves and thick rolling parts are provided on the outer peripheral surface at appropriate locations of the connections, and the upper and lower ends are fitted with the normal casings. A short connecting casing formed with a joint is interposed, and the outer circumferential surface is divided into a vertical swirl groove forming part and a thick rolling part at the lowest end of the connected normal casing,
An excavation casing characterized by having a fitting joint for a regular casing at its upper end and a short casing cutting head having a cutter bit at its lower end.