GB2142677A

GB2142677A - Method of placing a pile in the earth and boring rod used therefore

Info

Publication number: GB2142677A
Application number: GB08409465A
Authority: GB
Inventors: Hazime Matsuzawa; Akira Nakayama
Original assignee: MATSUZAWAKIKO KK
Current assignee: MATSUZAWAKIKO KK
Priority date: 1983-07-04
Filing date: 1984-04-12
Publication date: 1985-01-23
Also published as: KR850001354A; GB2142677B

Abstract

A consolidated soil layer along the inner wall of the vertical cavity is formed by pressing the soil excavated while a boring rod 2 forms the vertical cavity in the earth against the inner wall of said vertical cavity. A ready-made pile is inserted into the vertical cavity having said consolidated layer therein. Said pile is fixed by the consolidated layer being pressed against the outer circumference of said pile as a result of the restoration of the soil from its consolidated state to its normal state. Cement grout is fed through the boring rod 2 to form soil cement 14 in a pit R in a bearing stratum W to provide foot protection for the pile. The grout can rise round the pile when inserted. A casing tube rotating oppositely to the boring bit may follow it into the cavity to be withdrawn after insertion of the pile. <IMAGE>

Description

SPECIFICATION Method of placing a pile in the earth and boring rod used therefor The present invention relates to a method for placing a pile in the earth which method comprises forming a vertical cavity within the earth and fixing a ready-made pile within said vertical cavity and the invention also relates to a boring rod used in this method.

In accordance with one conventional method, the vertical cavity is formed by an earth auger provided with screws along its full length. While the fluid cement grout is being grouted into the vertical cavity at the lower end of said auger, the auger is extracted. Then, a ready-made pile such as a concrete pile or an H-shape steel pile, is inserted in the vertical cavity. When said cement grout is hardened, said ready made pile is fixed within the vertical cavity. This method has been generally known.

Such a conventional method has a disadvantage. When the soil excavated is discharged out of the vertical cavity, the wall of the cavity collapses and the ground adjacent the vertical cavity is caused to be loosened. thereby, the ground sinks and causes damage to adjacent buildings.

When water gushes underground, the cement grout inserted into the vertical cavity tends to be washed away and the said pile becomes incapable of being fixed.

One object of the present invention is to provide a method of placing a pile in the earth which method is capable of preventing the wall of the vertical cavity from collapsing and the ground from subsiding. The invention enables a ready-made pile to be fixed firmly in a vertical cavity.

Another object of the invention is to provide a method for placing a pile in the earth which method is capable of preventing the cement grout, when such cement grout is used for fixing the pile, from being washed away underground.

Further, another object of the present invention is to provide a boring rod useful for practising the said method for placing a pile in the earth.

According to one aspect of this invention, there is provided a method for placing a pile in the earth, comprising the step of pressing the soil excavated, while forming the vertical cavity in the earth, against the inner wall of the vertical cavity, instead of discharging the soil out of the vertical cavity, and forming the layer of consolidated soil along the inner wall thereof, inserting the ready-made pile in the vertical cavity formed as mentioned above, and fixing said pile by the above-mentioned layer of consolidated soil which returns to the normal condition from the consolidated state and sticks to the outer circumference of said pile.

- When the above-mentioned method is practised, the vertical cavity can be prevented from collapsing because of the above-mentioned layer of consolidated soil. Not only that, but the pile can be firmly fixed within the vertical cavity by the restoration of the consolidated soil layer to its original statue.

According to another aspect of the present invention, there is provided a method for placing a pile in the earth, comprising the step of pressing the soil excavated, while forming the vertical cavity, against the inner wall of the vertical cavity and forming the layer of consolidated soil along the inner wall thereof, supplying the vertical cavity with the cement grout for fixing the pile, inserting the pile in the cement grout within the vertical cavity, and fixing the said pile by said consolidated soil layer which returns to the original state after the cement grout is hardened and sticks to the outer circumference of said hardened cement layer.

When this method is practised, the cement grout introduced into the vertical cavity is prevented from being washed away underground because of said soil consolidated layer. Thus, this constitutes a further advantageous method.

According to still another aspect of this invention, there is provided a boring rod to be used for the method for placing a pile in the earth, which boring rod has a rod and a boring head fixed at the lower end of said rod, said boring head comprising a downwardly tapering conical mandrel coaxially fixed with said rod and attached to the lower end of the rod, screw means positioned, almost from upper end to lower end, on the outer circumference of said mandrel, the diameter of said screw means being almost the same, from upper end to lower end, as the maximum diameter of said mandrel at its upper end whereby the capacity of a helical channel formed by said screw means is upwardly diminished, and a boring bit positioned at the lower end of said head having a boring diameter which is almost equal to the maximum diameter of said mandrel at its upper end.

When the vertical cavity is forried with this boring rod in the earth, it is possible to form the vertical cavity having the inner-wall consisting of a consolidated soil layer by a single effort merely through one excavation with this boring head up to the desired depth.

The preferred embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figs. 1 to 6, inclusive, show various steps of one embodiment of the present invention.

Fig. 1 is a side elevational view showing a step of forming a vertical cavity in earth with a boring rod. Fig. 2 is a side elevational view showing a step of excavating a bearing stratum of the earth. Fig. 3 is a side elevational view showing a step of drawing up the aforementioned boring rod out of the vertical cavity.

When the vertical cavity is formed with this boring rod in the earth, it is possible to form the vertical cavity having the inner wall consisting of consolidated soil layer by a sigle effort merely through one excavation with this boring head up to the desired depth.

The preferred embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 to 6, inclusive, show various steps of one embodiment of the present invention.

Figure 1 is a side elevational view showing a step of forming a vertical cavity in earth with a boring rod.

Figure 2 is a side elevational view showing a step of excavating a bearing stratum of the earth.

Figure 3 is a side elevational view showing a step of drawing up the aforementioned boring rod out of the vertical cavity.

Figure 4 is a side elevational view showing a step of inserting a pile into the vertical cavity.

Figure 5 is a side elevational view showing a step of pushing the lower end part of said pile into a pit for foot protection.

Figure 6 is a side elevational view showing a state in which said pile is fixed within the vertical cavity.

Figures 7 to 10, inclusive, show steps, but omitting some of another embodiment of the present invention.

Figure 7 is a side elevational view showing a step of drawing up a boring rod, while jetting cement grout, out of the vertical cavity.

Figure 8 is a side elevational view showing a step of inserting a pile into the vertical cavity.

Figure 9 is a side elevational view showing the step of pushing the lower end part of said pile into a pit for foot protection.

Figure 10 is a side elevational view showing the state in which said pile is fixed within the vertical cavity.

Figures 11 to 1 7, inclusive, show various steps in another embodiment.

Figure ii is a side elevational view showing a step of pushing a casing tube into a vertical cavity, while forming the vertical cavity with a boring rod.

Figure 12 is a side elevational view showing a step of forming a bearing stratum.

Figure 13 is a side elevational view showing a step of drawing up the boring rod, while jetting cement grout, from the casing tube.

Figure 14 is a side elevational view showing a step of inserting a pile into the casing tube.

Figure 15 is a side elevational view showing a step of pushing the lower end part of said pile into the pit for foot protection.

Figure 16 is a side elevational view showing a step of drawing up said casing tube out of the vertical cavity.

Figure 1 7 is a side elevational view showing the state in which said pile is fixed within the vertical cavity.

Figure 18 is a fragmentary view in side elevation of a boring rod, omitting the upper part.

Figure 19 is a view in section taken on the line A-A in Fig. 18.

Referring now to the drawings, there will be firstly described a boring rod to be used for the method of the present invention.

Now referring to Figs. 18 and 19, a boring head 2 is connected to the lower end of the long hollow rod 1. It has a boring diameter which is two to three times as large as the diameter of the rod. Said boring head 2 has double screws 4 and 4 throughout the overall length of the outer circumference of a downwardly tapering conical hollow mandrel 3 and bits 5 fixed at the end of said screws 4 and 4 positioned at the lower end of the mandrel 3.

The screws 4 and 4 have, from the upper end to the lower end, equal pitch and a diameter which is the same as the maximum diameter of said mandrel 3. Thus the size of the spiral channel formed by the outer circumference of said mandrel 3 and screws 4 and 4, namely, the delivery capacity of soil, is gradually decreased from the lower end to the upper end of mandrel 3.

The boring diameter of said bit 5 is approximately the same as the maximum diameter of said mandrel 3 at the upper end. The upper end having the largest diameter of said hollow mandrel 3 is closed by an upper plate 6. A plug 7 projecting from the center of said plate is inserted into a socket 8. Joint pins 9 and 9 are inserted. Thus, the boring head 2 and rod 1 are connected coaxially with each other.

A cement grout supply pipe 10 passing vertically through said hollow rod 1 is connected with the upper end of a cement grout supply pipe 11 passing vertically through the hollow mandrel 3 of the boring head 2. Said supply pipe 11 has an orifice 1 2 at the lower end of mandrel 3.

Said rod 1 is coaxially provided with a cylindrical vibration damper 1 3 having approximately the same diameter as the maximum diameter of said mandrel 3.

Example 1 (method of Figs. 1 to 6) As shown in Fig. 1, the rod 1 of said boring rod is first caused to rotate so that the boring head 2 is caused to rotate clockwise. The vertical cavity having a circular section is excavated.

At this time, the boring head 2 transports the soil excavated by its bits 5 upwardly by means of screws 4 and 4. The volume provided for the soil as it is transported by screws 4 and 4 decreases from the lower end to the upper end. The soil is harder pressed against the inner wall of the cavity as it is transported upwardly. In consequence, the entire inner wall is covered by the consolidated soil layer H having reduced porosity. The excavated soil which is not used for forming the consolidated layer H remains within the cavity.

When the boring head 2 reaches the bearing stratum W of the earth, the pit for foot protection 1 2 is formed to the desired depth by the boring head 2 as shown in Fig. 2.

Thus, while the boring head 2 is rotated reversely within the said pit for foot protection, fluid cement grout comprising cement and water is poured through supply pipes 10 and 11 into the pit for foot protection R at the jetting orifice on the lower end of the boring head. The cement grout is mixed with the soil within the pit R and stirred to form soil cement 14 for foot protection. Thus, the boring head is drawn up, while rotating reversely, as shown in Fig. 3. The rotation of the boring head 2 may be stopped, if desired, when it is drawn up.

Then, the PC pile P of circular section is inserted in the vertical cavity, as shown in Fig. 4 and the lower end of said pile is pushed into the soil cement 14 within the pit for foot protection.

After the pile P is pushed thereinto, said cement soil 14 becomes hardened. The lower end of the pile is fixed by said hardened soil cement layer 1 5. Thereafter, the soil of the consolidated layer H on the wall of the cavity gradually and automatically returns from the consolidated state to the normal state and sticks to the circumference of the pile P as shown in Fig. 6. Thus, the pile P is fixed within the earth. For the purpose of reinforcing the pressure of said soil against the circumference of the pile, it is desired that the inside diameter of the vertical cavity including the consolidated layer H should be made approximately equal to the outer diameter of the pile P.

An observation is herein made of the consolidation degree of said consolidated layer H. The particles and porosity of the stratum excavated is generally as shown below.

Stratum soil particle porosity Loam 0.0047 mm and under 60 to 70% Sand 0.0048 to 1.9 mm 35 to 45% Pebble 2.0 mm and over 25 to 35% Sand Stone, Conglomerate 0.4 to 68 Slate, Granite 0.04 to 0.6t The practice of the present invention results in the reduction of said soil excavated to about 1/4 in volume. Thus, the porosity is changed 1 5 to 18%, in terms of loam stratum, 9 to 13% in terms of sand stratum and 6 to 10% pebbel stratum. Such change reduces the porosity of said sand conglomerate to nearly 0.4 to 6%.This means that sand and pebble strata are reduced nearly to sand stones, conglomerate and the like.

Thus, the said consolidated layer H on the wall of the cavity is placed in the category of rocks and maintains such state for a considerable period of time. The wall of the cavity can be prevented from collapsing for such period. The consolidated layer H prevents gushing water from penetrating into the vertical cavity even in the area where water would otherwise gush out.

Example 2. (method of Figs. 7 to 10).

While forming substantially the same consolidated layer Ha as formed by the steps shown in Figs. 1 and 2 of Example 1 by using substantially the same boring rod as shown in Figs. 1 8 and 19, the step of excavating the vertical cavity and the step of putting the soil cement 1 4a in the pit Ra for foot protection are used. Thereafter, the boring head 2a is caused to rotate reversely or stop. Then, while the fluid cement grout 1 6a comprising the mixture of cement and water is caused to jet out of the orifice of the boring head 2a for fixing the pile, said boring head 2a is pulled out of the vertical cavity.

The cement grout 1 6a is poured thereinto in an amount appropriate for inserting the pipe in the subsequent step. The grout poured is surrounding by the consolidated layer Ha and prevented from being exuded or washed away.

An H-shape steel pile Pa is inserted into the cement grout 1 6a within the vertical cavity, as shown in Figure 8.

Thus, the cement grout 1 6a is interposed between the inner surface of the consolidated layer Ha and the pile Pa. Then, the lower end of said pile Pa is pushed into the soil cement 1 4a of the pit Ra for foot protection. It is desired that the level of the cement grout 1 6a should go up to the same level as the top of the vertical cavity.

After the said pile Pa is pushed thereinto, the soil cement 1 4a and cement grout 1 6a become hardened. The outer circumference is surrounded by the hardened soil cement layer 1 spa and hardened cement layer 1 7a. Thereafter, the soil of the consolidated layer Ha on the wall of the cavity is gradually restored to its original state. It is pressed against the outer circumference of the aforementioned hardened cement layer 1 5a and 1 7a as shown in Fig. 10. The pile Pa is firmly fixed.

Example 3 (method of Figs. 11 to 17) As shown in Fig. 11, the boring rod which is substantially the same as that shown in Figs. 1 8 and 1 9 is inserted into the steel pipe casing tube 1 8b having the inside diameter which is slightly larger than the maximum diameter of the boring head 2b. The boring head 2b projects downwards at the lower end of said casing tube. Under such condition, the boring head 2b is caused to rotate clockwise and excavate the vertical cavity ahead of the lower end of the aforementioned casing tube 1 8b. Simultaneously, the casing tube 1 8b is caused to rotate in a direction opposite to the rotation of said boring head and pushed into the vertical cavity. The consolidated soil layer Hb is formed on the wall of the vdertical cavity in a manner similar to those described in Examples 1 and 2.The forcible insertion of said casing tube 1 8b prevents completely the wall of the cavity from collapsing.

Then, the pit for foot protection Rb is formed within the bearing stratum Wb by the boring head 2b as shown in Fig. 12.

The soil cement 1 4b for foot protection is put into the pit for foot protection Rb as described with reference to Figs. 1 and 2.

As shown in Fig. 13, the boring head 2b is caused to rotate counterclockwise. While the pile fixing cement grout 1 6b is being jetted into the vertical cavity, the boring rod is drawn up out of the vertical cavity. When the boring head 2b is drawn up, the rotation thereof may be stopped, if desired.

As shown in Fig. 14, the H-shape steel pile Pb is downwardly inserted into the cement grout 1 6b within the casing tube 1 8b. Then, as shown in Fig. 15, the lower end part of said pile Pb is pushed into the soil cement 1 4b within the pit for foot protection.

As shown in Fig. 16, the casing tube 1 8b is drawn up out of the vertical cavity before the said soil cement 1 4b and cement grout 1 6b become hardened.

After the casing tube 1 8b is drawn up, the cement grout 1 6b within the vertical cavity comes into direct contact with the inner wall of the cavity. Said cement grout is prevented by said consolidated layer Hb from being penetrated into the ground or being washed away.

After said casing tube 1 8b is drawn up, said soil cement 1 4b and cement grout 1 6b become hardened. The outer circumference of the pile Pb is surrounded by the hardened soil cement 1 sub and hardened cement layer 1 7b. Thereafter, said consolidated layer Hb is gradually restored to its original state. As shown in Fig. 17, it is pressed against the outer circumference of hardened cement layers 1 sub and 1 7b. Thus, the pile Pb is firmly fixed.

Claims

1. A method for placing a pile in the earth, comprising the step of forming a consolidated soil layer along the inner wall of a vertical cavity by pushing soil excavated while boring the vertical cavity against the inner wall of the vertical cavity, the step of inserting a ready-made pile into the vertical cavity lined with said consolidated layer and the step of fixing said pile as a result of said consolidated soil layer pressing against the outer circumference of said pile due to restoration of the consolidated layer from its consolidated state to the normal state.

2. A method according to Claim 1, which further comprises, after the step of forming the vertical cavity with said consolidated soil layer, the step of forming a pit for pile fdot .prntection within a bearing stratum of the earth, and the step of forming soil cement within the pit for foot protection by pouring cement grout into said pit for foot protection and mixing the same cement grout with soil, and further comprises, after inserting the ready-made pile into the vertical cavity, the step of pushing the lower end part of said pile into soil cement within said pit for foot protection.

3. A method for placing a pile in the earth, comprising the step of forming a consolidated soil layer along the inner wall of a vertical cavity by pushing the soil excavated while boring the vertical cavity against the inner wall of the vertical cavity, the step of supplying the vertical cavity having said consolidated layer with the cement grout for fixing the pile, the step of inserting the ready-made pile into the cement grout of the vertical cavity, and, after said cement grout becoming hardened and the hardened cement layer being formed around said pile, the step of fixing said pile by the soil of the consolidated layer becoming pressed against the outer cirumference of said hardened cement layer due to the restoration of the consolidated layer to its original state.

4. A method according to Claim 3, which further comprises, after the step of forming the vertical cavity with said consolidated layer, the step of forming a pit for pile foot protection within the bearing stratum, and the step of forming soil cement within the pit for foot protection by pouring cement grout into said pit for foot protection and mixing the same cement grout with soil, and further comprising, after inserting the ready-made pile into the cement grout within said vertical cavity, the step of pushing the lower end part of said pile into soil cement within said pit for foot protection.

5. A method for placing a pile in the earth, comprising the step of forming a consolidated soil layer along the inner wall of a vertical cavity by pushing the soil excavated while boring the vertical cavity against the inner wall of the vertical cavity and simultaneously inserting a casing tube into said vertical cavity, the step of supplying the casing tube within the vertical cavity with the cement grout for fixing the pile, the step of inserting a ready-made pile into the cement grout within the casing tube, the step of drawing the said casing tube out of the vertical cavity prior to the hardening of said cement grout and the step of fixing said pile, after said cement grout becomes hardened and a hardened cement layer has formed around said pile, by the soil of said consolidated layer pressing against the outer circumference of said hardened cement layer due to the restoration of the soil to its original state.

6. A method according to Claim 5, which further comprises, after the step of forming the vertical cavity with said casing tube, the step of boring the pit for pile foot protection in a bearing stratum, the step of pouring the cement grout into said pit for foot protection and simultaneously forming the soil cement within said pit for foot protection by mixing said cement grout with soil, and further comprising, after the step of inserting the ready-made pile into the cement grout within said casing tube, the step of pushing the lower end part of said pile into the soil cement of the pit for foot protection.

7. A boring rod for use in the method of any one of the preceding claims, comprising a rod and a boring head attached to the lower end of said rod, said boring head comprising a downwardly tapering conical mandrel attached coaxially to the lower end of the rod, screw means provided approximately from the upper end to the lower end on the outer circumference of said mandrel, said screw means having the diameter which is approximately the same, from the upper end to the lower end, as the maximum diameter of said mandrel at the upper end, whereby the capacity of a helical channel formed by said screw means is upwardly reduced, and a boring bit, having the boring diameter approximately the same as the maximum diameter of said mandrel at its upper end, provided at the lower end of said boring head.

8. A method of placing a pile in the earth substantially as herein before described with reference to Figs. 1 to 6 of the accompanying drawings.

9. A method of placing a pile in the earth substantially as hereinbefore described with reference to Figs. 7 to 10 of the accompanying drawings.

10. A method of placing a pile in the earth substantially as hereinbefore described with reference to Figs. 11 to 1 7 of the accompanying drawings.

11. A boring rod for use in the method of any one of Claims 1 to 6 and substantially as herein before described with reference to Figs. 1 8 and 1 9 of the accompanying drawings.