GB2085509A - Soil stabilisation - Google Patents

Abstract

An injection tube for the injection of a liquid soil consolidation agent consists of an injection pipe body (1) carrying at its lower end a perforated injection member (6) of smaller diameter. The injection pipe is bored into the ground to the requisite depth and then withdrawn again by the length of the member (6). Consolidation agent is injected to fill the resulting void (7). The process is continued in like manner in stages. <IMAGE>

Description

SPECIFICATION Method and apparatus for injecting liquid soil consolidation agent into the ground This invention relates to the injection of a liquid soil consolidation agent into the ground for ground stabilisation.

Examples of prior methods of soil consolidation are the forced injection of the liquid soil consolidation agent under high pressure through an injection pipe to effect high speed injection thereof through the extremity of the pipe and into the ground; and a low pressure jetting method using a strainer pipe, the side wall of which is provided with a number of jet holes. In these prior art injection methods, however, there has been the disadvantage that, when the liquid soil consolidation agent is discharged into the ground, the jetting holes are closely in contact with or closed by the surrounding soil; the wall of the injection pipe itself thus prevents homogeneous jetting of the liquid consolidation agent into the soil, so that there is lack of balance between a portion of the soil contacting with a hole and a portion which is not adjacent to any hole.

It is accordingly an object of the present invention to provide a method by which the above-mentioned disadvantage can be reduced or eliminated so that a natural and homogeneous jetting of a liquid consolidation agent can be carried out.

The invention provides, in one aspect, a method of consolidating soil which comprises rotationally driving an injection pipe downwardly into the ground, the injection pipe comprising an injection pipe body and an injection member which is attached to the extremity of the pipe body, which has a diameter smaller than that of the pipe body, and which has a plurality of jet holes formed in its wall; after the injection pipe has reached a predetermined depth, moving the injection pipe upwardly by a given length; forcibly supplying a liquid soil consolidation agent into the injection pipe to eject the agent through the jet holes in the injection member; and continuing the upward movement of the injection pipe and the injection of the agent in stages; whereby a column of the agent is progressively formed in the empty bore hole formed in the soil by the injection pipe.

In this method, when the injection pipe is moved upwardly by one stroke, say, an annular gap defined by the vacant space bored previously with the injection pipe body and the injection member is formed in the ground. Then the liquid consolidation agent injected from the injection member fills up the above annular gap, so that the liquid consolidation agent uniformly permeates the surrounding soil. The annular gap itself thus functions as a kind of filling pipe having in a sense no wall, whereby a very homogeneous jetting of the liquid consolidation agent can quite naturally be carried out.

In another aspect, the invention provides apparatus for injecting a liquid soil consolidation agent into the ground, comprising an injection pipe body; an injection member which is attached to the extremity of the injection pipe body, which has a diameter less than that of the pipe body, and which has a plurality of jet holes in its wall; a rotational driving mechanism for driving the pipe body into the ground; and a feed mechanism for supplying the liquid soil consolidation agent to the pipe body.

The invention wili be more easily understood by way of example from the following description of soil consolidation apparatus and method, reference being made to the accompanying drawings, in which: Figure 1 is a longitudinal sectional view showing the apparatus for injecting a liquid soil consolidation agent into the ground; and Figure 2 is a longitudinal sectional view showing the essential part of an extreme end of a double-walled injection pipe.

Referring to the drawing, reference numeral 1 designates an injection pipe body to which a rotational drive mechanism 2 is connected for driving and withdrawing the injection pipe into and from the ground. A supply mechanism represented by a pipe 4 is connected to the pipe body through a rotary joint 3 to enable liquid soil consolidation agent to be supplied under pressure to the pipe body. 1 4 is a cutting blade carried on the lower end of the body 1. An injection member 6 having a plutality of jet holes 5, 5 is mounted on the lower extremity of the pipe body 1 and carries a cutting blade 1 5 at its lower end. The member 6 has a diameter les than that of the pipe body 1, as shown.The injection pipe thus constructed is rotationally moved downwardly into the ground while initiaily feed water or the like under pressure is supplied from the feed mechanism 1. When the injection pipe reaches a predetermined depth, it is upwardly retracted by a length corresponding to that of the injection member 6. An annular gap 7 is thus formed in the ground by the vacant space bored previously by the pipe body 1 and the injection member 6, the gap in part surrounding the member 6 in its new position. In this situation, when a liquid soil consolidation agent is forcibly supplied from the feed mechanism into the injection pipe, the liquid consolidation agent jets through the jet holes 5, 5 provided through the wall of the member 6 to fill up the annular gap 7 and, at the same time, such liquid consolidation agent permeates the surrounding soil.

The annular gap 7 effectively functions as a strainer pipe having no wall, so that the liquid consolidation agent permeates homogeneously the surrounding soil. The injection pipe is then further withdrawn upwardly by one stroke and injection of the liquid consolidation agent is again carried out, so that a similar annular gap is formed in the ground and, at the same time, the remaining vacant space in the preceding step is also filled up with the liquid consolidation agent. By continuing the injection of the consolidation agent stages in similar manner as mentioned above, a column of consolidated material is formed. As a result, and as such consolidated columns are successively joined together, a very valuable stable layer to act as for example a cut-off wall, a retaining wall or the like can be formed.

Although Figure 1 has been described above in connection with the injection of a single liquid consolidation agent, a two-liquid type consolidation agent can be utilised by means of the modified construction of Figure 2, in which an inner pipe 8 is provided inside the injection pipe body 1 and an annular nozzle 10 is fitted to the extreme end portion of a liquid supply passage 9 so formed between the inner and outer pipes. In this arrangement, the injection pipe is again driven downwardly into the ground while high pressure water is supplied through a liquid supply passage 11 formed by inner pipe 8 to cause the water to be ejected through the jet holes 5, 5 at the time of boring on the ground by the descent of the injection pipe.When the filling pipe reaches a predetermined depth, the injection pipe is retracted upwardly by a length substantially corresponding to that of the member 6, and a liquid A is forcibly supplied into the supply passage 11 in inner pipe 8 and a liquid B is simiiariy supplied into the supply passage 9 in outer pipe 1. The annular nozzle 10 mounted on the extreme end of the supply passage 9 has a frustoconical annular jet hole 12, so that the liquid B emerges as a conical jet converging to an apex and collides and mixes with the liquid A from supply passage 11 in a mixing chamber 13.

Thereafter the liquid soil consolidation agent consisting of the mixture of liquids A and B jets into the annular gap 7 through the jet holes 5, 5 to fili up the gap and, at the same time, the liquid consolidation agent permeates the surrounding soil.

It is to be noted that in the case where a liquid consolidation agent of two-liquid type is employed, smooth jetting of the consolidation agent can be effected by slowly revolving the filling pipe. Furthermore, when this injection of the consolidation agent is continued in stages, a column of consolidated layer is again formed in the ground as in the case of utilising a one-liquid type consolidation agent.

It is to be understood that the foregoing description is intended to be illustrative only and that the embodiments described can be modified in various ways within the scope of the invention.

For example, the shape of the injection member 6, and the number and positions of the jet holes may be suitably modified dependent upon a gelation time of the liquid soil consolidation agent, the properties of stratum and the like.

By the method and apparatus described above, an extremely natural and even injection and permeation of a liquid consolidation agent into the surrounding soil can be effected, as though such injection and permeation are carried out by the use of an injection pipe having no wall. In addition the resulting consolidated layer of this invention is very homogeneous as compared with those formed by known methods using known apparatus.

Claims (6)

1. A method of consolidating soil which comprises rotationally driving an injection pipe downwardly into the ground, the injection pipe comprising an injection pipe body and an injection member which is attached to the extremity of the pipe body, which has a diameter smaller than that of the pipe body, and which has a plurality of jet holes formed in its wall; after the injection pipe has reached a predetermined depth, moving the injection pipe upwardly by a given length; forcibly supplying a liquid soil consolidation agent into the injection pipe to eject the agent through the jet holes in the injection member; and continuing the upward movement of the injection pipe and the injection of the agent in stages; whereby a column of the agent is progressively formed in the empty bore hole formed in the soil by the injection pipe.

2. Apparatus for injecting a liquid soil consolidation agent into the ground, comprising an injection pipe body; an injection member which is attached to the extremity of the injection pipe body, which has a diameter less than that of the pipe body, and which has a plurality of jet holes in its wall; a rotational driving mechanism for driving the pipe body into the ground; and a feed mechanism for supplying the liquid soil consolidation agent to the pipe body.

3. Apparatus as claimed in claim 2, wherein an inner pipe is provided inside the injection pipe body to form a double pipe construction in the injection pipe body.

4. Apparatus as claimed in claim 2, wherein a portion of the injection pipe body is constructed as a double pipe and, at the same time, the extreme lower end portion of the liquid supply passage in the outer pipe is constructed as an annular frustoconical nozzle functioning such that the stream of liquid soil consolidation agent converges into the apex of the cone.

5. A method for injecting a liquid soil consolidation agent into the ground, substantially as hereinbefore described and illustrated in the drawing.

6. An apparatus for injecting a liquid soil consolidation agent into the ground, substantially as hereinbefore described and illustrated in the drawing.