GB2225363A

GB2225363A - Ground stabilization

Info

Publication number: GB2225363A
Application number: GB8920787A
Authority: GB
Inventors: Wataru Nakanishi
Original assignee: NIT Co Ltd Japan
Current assignee: NIT Co Ltd Japan
Priority date: 1988-11-18
Filing date: 1989-09-14
Publication date: 1990-05-30
Anticipated expiration: 2009-09-14
Also published as: FR2639381A1; GB2225363B; IT1231295B; CA1334795C; IT8921261A0; GB8920787D0

Abstract

A ground stabilization method comprises inserting an injection rod (1) into the ground, which injection rod includes a first conduit (2a) and a second conduit (2b) surrounding the first conduit, and a first injection nozzle (4a) communicated with the first conduit and a second injection nozzle (4b) surrounding the first nozzle and communicated with the second conduit; feeding a first component of an instantaneous hardening type hardening material into the flat conduit of the injection rod and a second component of the hardening material into the second conduit; and injecting the first component and the second component at a super high pressure through the first and second nozzles to mix with each other whilst the injection rod is revolved and retracted. Compressed gas and a slow hardening type hardening material may be substituted for the first and second components above mentioned. <IMAGE>

Description

GROUND REFORMING METHOD WITH A HARDENING MATERIAL MIXED AND INJECTED AT A SUPER HIGH PRESSURE AND REFORMING DEVICE OF SAME BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a method for reforming ground-condition by using an instantaneous hardening type hardening material to reform soft ground condition and harden foundation of building site. More particularly, the instantaneous hardening type hardening material is injected into the ground through a two fluid mixing nozzle.

Further, the present invention relates to a device for reforming ground-condition by using the two fluid mixing nozzle.

2. Description of the Prior Art Conventionally, various ground reforming methods using a hardening material jet have been provided. In these methods, high pressure and high speed jet injection has been applied to only a slow hardening type hardening material, on the other hand an instantaneous hardening type hardening material has been injected under a low pressure approaching ambient pressure. The high pressure injection has been conducted at highest 200 kg f/cm2, and thus any injection device adapted for further higher injection pressure has not yet been proposed.

The instantaneous hardening type hardening material cannot be used for such high pressure injection type ground reforming method because the instantaneous hardening type hardening material is composed of two separated liquids which should be mixed after injection. If these two liquids are mixed prior to injection, the hardening material will be wholly or partially hardened in an injection pump or pipe. Therefore the high pressure injection method has employed the slow hardening type hardening material which requires a long period to achieve hardening. However, the slow hardening type hardening material will sometimes cause problems owing to its slow hardening speed. For example, if injection amount will be increased, the slow hardening type hardening material will flow backwards to leak out of the injection pipe or the like.Special injection angle such as horizontal injection or upward injection will remarkably cause such problem and thus can not employ the high pressure injection method.

In the high pressure injection method, reaction force will be generated at the injection nozzle as the injection pressure is increased, and the reaction force will be applied to an injection rod. Revolving motion of the injection rod will be affected by the reaction force and as a result the injection rod will result in serious trouble.

BRIEF SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a ground reforming method which can overcome the above described problems.

It is another object of the present invention to provide a ground reforming method which employs an instantaneous hardening type hardening material injected at a super high pressure at least 200 kg f/cm2 to reform soft ground and harden foundation of building site.

It is a further object of the present invention to provide a ground reforming device adapted for the above method.

To accomplish the above objects, the ground reforming method according to the present invention comprises a first step for inserting an injection rod into ground to be reformed, which injection rod includes a first conduit and a second conduit surrounding the first conduit, and a first injection nozzle communicated with the first conduit and a second injection nozzle surrounding the first nozzle and communicated with the second conduit; a second step for individually feeding first and second components of an instantaneous hardening type hardening material into the first and second conduits of the injection rod; and a third step for injecting the first and second components under a super high pressure through the first and second nozzles to mix each other with moving back the injection rod from the inserted portion with revolving.

According to another aspect of the present invenion, the ground reforming device comprises an injection rod including a first conduit through which a first component of an instantaneous hardening type hardening material is fed and a second conduit through which a second component of the instantaneous hardening type hardening material is fed, the second conduit surrounding the first conduit; a first injection means communicated with the first conduit, which means includes a pair of first injection nozzles oppositely arranged in a side wall of the injection rod near its top; a second injection means communicated with the second conduit, which second injection means includes a pair of second injection nozzles surroundingly arranged around respective the first injection nozzles; and a drive means for supporting and driving the injection rod to revolve and retract the injection rod.

The first and second components of the instantaneous hardening type hardening material are respectively fed into the first and second coduits without mixing each other under a super high pressure. These components are injected through the injection nozzles and suddenly mixed each other to form hardening material jet. The jet injected from the opposite nozzles can absorb reaction force generated by injection from the other side. As the injection rod is revolving and moving back from the inserted position, the ground surrounding the injection rod is reformed into a cylindrical hardened layer.

Other and further objects of this invention will become obvious upon an understanding of the illustrative embodiment about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a schematic illustration showing one example of working state where the injection rod is inserted in ground; Fig. 2 is a vertical cross sectional view showing the top portion of the injection rod according to the present invention; and Fig. 3 is a cross sectional view taken along the line X - X in Fig. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be explained in conjunction with the accompanying drawings.

In Fig. 1, the reference numeral 1 denotes an injection rod which includes a first conduit 2a and a second conduit 2b isolated each other as shown in Fig. 2.

The first conduit 2a is arranged in a core of the injection rod 1 and surrounded with the second counduit 2b. The first conduit 2a is communicated with center nozzles 3a and 4a which are oppositely arranged in the side wall near the top of the injection rod l and extended radially with respect to the longitudinal axis of the injection rod 1.

As shown in Fig. 3, the second conduit 2b is communicated with surrounding nozzles 3b and 4b whoes annular openings surround respectively the center nozzles 3a and ta.

The injection rod 1 is supported by a drive unit 5 to revolve and retract the injection rod 1. The injection rod l is further connected to a first feeding pipe 6a and a second feeding pipe 6b through a swivel joint 6. Component A of an instantaneous hardening type hardening material is fed into the first conduit 2a from the first feeding pipe 6a, and component B of the instantaneous hardening type hardening material is fed into the second conduit 2b from the second feeding pipe 6b.

Alternatively, a slow - hardening type hardening material per se is fed into the first conduit 2a from the first feeding pipe 6a, and compressed gas is fed into the second conduit 2b from the second feeding pipe 6b.

The first and second feeding pipes 6a and 6b are connected to a compressor, not shown in the drawings, to generate a super high pressure fluid such as the instantaneous hardening type hardening material or gas.

The compressor includes a piston, a valve chamber, cylinder and a pressure sensitive member for transmitting pressure from the cylinder to the valve chamber. The pressure sensitive member is composed of active oil having different specific gravity from the instantaneous hardening type hardening material, and an elastic film actuated by the active oil. The active oil is moved in response to the reciprocal motion of the piston so that the hardening material can be introduced into the valve chamber and then discharged out of the chamber by the high pressure. In this compressor the hardening material is isolated from the piston through the pressure sensitive member. Therefore the hardening material can be discharged without energy loss caused by the friction between the piston and the hardening material.The valve chamber is provided with an inlet through which the hardening material is introduced into the chamber and an outlet through which the hardening material is discharged to the feeding pipe. Each the inlet and the outlet is provided with a valve box whose valve seat is sectionally formed in a half spherical recessed shape. The valve seat is further formed with a plurality of orifices in its axial direction. The valve seat receives a valve member formed in a spherical shape adapting for the valve seat. The valve member is always urged toward the valve seat by a spring. This valve mechanism employing the spherical valve member can promote to increase the discharging pressure.

The drive unit 5 is preferable to be designed that drive angle for the injection rod 1 can be freely changed and the drive unit 5 per se can be moved without additional drive mechanism.

The top of the injection rod 1 is provided with an excavating member 7 and a lubricating unit 8 as shown in Fig. 2. The lubricating unit 8 will discharge lubricant to assist excavating work of the excavating member 7.

pperation of the ground reforming method according to the present invention will be described. The injection rod 1 with revolving and discharging the lubricant from the lubricating unit 8 is moved towards ground M to be reformed. As the top of the injection rod 1 reaches to a predetermined depth, the lubricating unit 8 closes to stop discharging. The component A of the instantaneous hardening type hardening material is fed at a super high pressure into the first conduit 2a and the component B of the instantaneous hardening type hardening material (or gas) is fed at a super high pressure into the second conduit 2b. Both the components A and B are injected outwardly from the injection nozzles 3a, 3b, 4a and 4b while the injection rod 1 is moved back with revolving.

According to this revolving injection, the components A and B are completely mixed and then an essentially cylindrical hard layer S in the ground M has been generated.

Experiment in sand having N-value 15 to 20 resulted in an excellent reforming effect; that is, the cylindrical hard layer having a large diameter of 3m 70cm was obtained 2 under conditions; injection pressure of 400 kg f/cm injection rate of 100 Q/min, revolving speed of 8 r.p.m, and back-moving speed of 2cm/min.

As given explanation above, the ground reforming device according to the present invention can inject the instantaneous hardening type hardening material at a super high pressure 200 kg f/cmt or more. The two components of the instantaneous hardening type hardening material can be sufficiently and uniformly mixed immediately before application to the ground without back-flowing or leakage. On the other hand, when compressed gas such as air is injected from one injection nozzle, hardening material injected from the other nozzle can be splashed to a great distance. Further bubbles will generate by mixing the hardening liquid material and compressed gas. These bubbles will generate dynamic rupture effect by breaking these bubbles so that greater area will be hardened into a high density cylindrical hard layer by ruptured hardening material.The cylindrical hard layer may be formed in any configuration such as parallel arrangement or alignment as required.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been changed in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed. For example, one side of the injection means 3 and 4 or the feeding pipes 6a and 6b may be provided with a regulator valve to control injection condition, or the compressor may be further provided with a regulating means.

An example of a two component instantaneous hardening material is as follows: A component (5001) DENKA-ES 100KG, DENKA-ES SETTER 2 to 4Kg, Water to make 5001 B component (5001) Portland Cement 400Kg, Water to make 5001 When using instantaneous hardening material a number of precautionary measures would be taken. It would be normal to check the ambient temperature and to adjust the mixing ratio of the hardening material accordingly should the temperature be higher than 280C or there- abouts to avoid premature hardening. Also to avoid nozzle blockage it would be usual to prefilter the hardening material components using a mesh with openings that are smaller than the nozzle diameters.

Typically such diameters range between 1.8 mm and 3.2 mm. Since strong acid water and soil prevent satisfactory hardening of the hardening material, the PH value of the soil that is to be treated and of the water that is to be mixed in the preparation of the A and B components should also be checked. After working, the inside of the injection rod and all connective hoses etc should be subjected to a high pressure water washing for at least a ten minute period and the nozzle section should be dismantled and also washed thoroughly.

"TOUGH LOCK-3" manufactured by Sumitomo Cement Company for example may be used as the slower hardening material for the modified method described above.

A particular application of instantaneous hardening material is in the hardening of moist and water laden soils. In such soils slower hardening type materials have a tendency to disburse in soil water prior to hardening and are generally inappropriate.

Conversely in well drained soils, sandy soils and the like, slower hardening type hardening material may be used. An advantage of the modified method described above is that the hardening material is spread widely around the injection nozzle.

It will be apparent from the foregoing that the ground reforming device described can be used to treat a wide variety of soil conditions e.g. moist and water laden soils, organic soils, acid soils etc with either instantaneous or slower hardening type hardening materials as appropriate.

Claims

1. A ground reforming method comprising: inserting an injection rod into ground to be reformed, which injection rod includes a first conduit and a second conduit surrounding the first conduit, and a first injection nozzle communicated with the first conduit and a second injection nozzle surrounding the first nozzle and communicated with the second conduit; individually feeding first and second components of an instantaneous hardening type hardening material into the first and second conduits of the injection rod; and injecting the first and second components at a super high pressure through the first and second nozzles to mix with each other whilst retracting and revolving the injection rod.

2. A ground reforming device comprising: an injection rod including a first conduit through which a first component of an instantaneous hardening type hardening material can be fed and a second conduit through which a second component of the instantaneous hardening type hardening material can be fed, the second conduit surrounding the first conduit; a first injection means communicated with the first conduit, which means includes a pair of first injection nozzles oppositely arranged in a side wall of the injection rod near its top; a second injection means communicated with the second conduit, which second injection means includes a pair of second injection nozzles surroundingly arranged around respective the first injection nozzles; a high pressure generating means for providing a high pressure to the first and second component of the hardening material, the high pressure generating means being connected to the injection rod; and a drive means for supporting and driving the injection rod to revolve and retract the injection rod.

3. A ground reforming device according to claim 2, wherein the second conduit is connected to a source of compressed gas.

4. A ground reforming device according to either claims 2 or 3, wherein the injection nozzles are respectively provided with a regulator to control injection rate.

5. A ground reforming device according to any one of claims 2 to 4, wherein the high pressure generating means generates a super high pressure of 200 kg f/cm2 or more.

6. A ground reforming device according to any one of claims 2 to 5, wherein the drive means can move itself without any additional driving means.

7. A method of using the ground reforming device claimed in claim 2 wherein first and second components of an instantaneous hardening type hardening material are introduced into respective first and second conduits and expelled under super high pressure whilst the injection rod is both revolved and retracted.

8. A method of using the ground reforming device claimed in claim 2, wherein a hardening material and a compressed gas are introduced into respective first and second conduits and the hardening material expelled under super high pressure whilst the injection rod is both revolved and retracted.

9. A ground reforming method comprising a first step wherein an injection rod is inserted into ground to be reformed; and a second step wherein hardening material is expelled under a super high pressure from one end of the injection rod whilst the injection rod is both revolved and retracted.

10. A method according to claim 9, wherein the hardening material is of instantaneous hardening type, comprises two components each of which are expelled from and mixed at said one end of the injection rod.

11. A method according to claim 9, wherein the hardening material is of slow hardening type and is expelled from said one of the injection rod together with compressed gas.

12. A ground reforming method when performed substantially as described hereinbefore with reference to the accompanying drawings.

13. A ground reforming device constructed, adapted and arranged to perform substantially as described hereinbefore with reference to and as shown in the accompanying drawings.