JP2879386B2 - Ground improvement or reinforcement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving or strengthening soft ground, and in particular, by pressing a hardened cementitious material such as a cementitious material into a loosened ground so as to push it into the ground. The present invention relates to a method for improving the diameter of a solidified column while improving the method.

[0002]

2. Description of the Related Art Various types of ground improvement methods of this type are known. A typical example is a chemical liquid injection method. In this method, as is well known, a chemical solution is injected at a low pressure through an injection pipe inserted into the ground. In this case, the basic idea is that the chemical solution is osmotically injected without disturbing the ground.

On the other hand, in recent years, a high-pressure injection method represented by a so-called jet grout method has been widely used. In this high-pressure injection method, grout is injected into the ground at the same time as the ground is disturbed by the high pressure of grout or water. This high-pressure injection method can be said to be an agitation method for the ground. On the other hand, as a pure stirring method, mainly for the viscous ground, while a stirring shaft having stirring blades is inserted into the ground, the cement-based material is supplied through the stirring shaft or from a separate supply system,
While stirring the ground with stirring blades, the stirring region is replaced with a cement-based material or stirred and mixed with earth and sand.

[0004]

However, in the first chemical solution press-in method, in order to perform osmotic press-in, a low-viscosity material,
Since a water glass-based material is mainly used, the improved strength is low and the durability is poor. Furthermore, the reason that the improvement strength is low is that the ground is not replaced by the improvement material, but the permeation injection or splitting injection is preferable, so that the improvement material occupies a low per unit volume and is non-uniform. doing.

[0005] To further add a problem, in the case of a normal sandy soil layer, infiltration can be performed, but due to a slight difference in injection conditions, splitting injection is performed, and infiltration cannot be performed. There are many things. On the other hand, when injected into a cohesive soil layer, splitting is performed, and the improved material often escapes. For this reason, it is difficult to reliably improve only the target area, and there is a lot of material loss due to the runaway. Further, the desired improved diameter cannot be made uniform, and often becomes a tree-like (tree-like or vein-like) shape.

In the second high-pressure injection method, the ground is extremely disturbed, and slime (muddy water) treatment requires a great deal of labor and cost. Furthermore, if cutting and pouring are to be performed uniformly, and if slime is to be sufficiently discharged, the improvement rate must be reduced, which is a time-consuming method. Moreover, for sandy ground, the strength is 30kg /
cm ² or more, in the case of viscous soil is to target a 10 kg / cm ² or more, the variation in intensity due to the position variation and improvement of strength due to geological nature is extremely large problem. In particular, in the case of a viscous ground, there is a large variation due to embedment of the earth mass due to insufficient cutting.

[0007] The third stirring method is a major drawback in that the equipment becomes large, and in the case of a viscous soil layer, the mixture of the soil particles and the improving material co-rotates with the stirring blade, and the stirring effect is reduced. Not very high, thus lacking in uniformity of improved strength. On the other hand, this stirring method targets the viscous ground as described above. Application to sandy ground is not impossible, but it cannot be applied unless a huge stirring means is used because the resistance of the stirring shaft and stirring blade to the ground is large.

Accordingly, the main objects of the present invention are to improve the strength and the uniformity of the improved body, to make it possible to carry out the construction with simple and small-sized equipment, and to limit or achieve the object of the compaction effect. An object of the present invention is to form a strong improved body only at a specific location, and to increase the diameter of the improved body.

On the other hand, in order to solve this problem, the present inventors have previously disclosed in Japanese Patent Application No. 3-129473 a high pressure water injection nozzle provided on the outer peripheral surface of the tip of an injection pipe inserted into the ground. A method was proposed in which high-pressure water was injected to loosen the target ground, or after loosening, a hardened self-hardening material was pressed into the loose ground to form an improved body.

However, the reach distance from the high-pressure water injection nozzle has a limit in relation to the injection pressure and the like, and in particular, there is the ground that is easily relaxed due to the properties of the ground, that is, the ground that is difficult to relax. Relaxing with only the energy of the γ is a factor that causes the improved diameter to vary in the depth direction. On the other hand, it was considered to agitate the ground to a large diameter by the above-described agitation method, but in this case, the above-mentioned problem is accompanied, and in order to insert the agitating blade into the ground, a large load is applied. .

[0011] Therefore, another object of the present invention is to prevent the ground from being relaxed by the energy of high-pressure water, but to prevent variation in the improved diameter.

[0012]

SUMMARY OF THE INVENTION The object of the present invention is to provide an overhanging injection section which is provided at least at a tip end of an injection pipe in a state where the diameter is expanded and ejected to the outside of the pipe. An injection nozzle for injecting high-pressure water at least covering the ground area for the protruding length of the overhanging injection part, and further forming a spout of self-hardening material on the tip side from the lowermost injection nozzle; and is inserted into the ground, while at least a certain depth at a given depth customers, said by injecting high pressure water from the injection nozzle, to relax the ground region of the projecting length of the at least the projecting jetting portion After forming the relaxing mud column, press-fit a hardened self-hardening material into the relaxing mud column from the spout at the position where the predetermined depth is reached or in the process of lifting the injection pipe to form an improved body. Can be solved. In this case, the injection nozzle may be provided on the overhanging injection unit so as to face downward, or the injection nozzle may be provided on the outer surface of the injection pipe below the overhanging injection unit in the radial direction.

[0013]

According to the present invention, the present invention is intended to provide a "fluid injection agent having a large amount of water per unit and having a large amount of water per unit when the ground is once loosened and then press-fitted into the loosened portion, for example, as in the jet grouting method. The strength after the improvement is improved by the replacement action and the consolidation action of the improving material as compared with the case of using. "

According to the present invention, the target ground can be loosened by injecting high-pressure water. The loosening of the ground is mainly performed by breaking the connection between the large soil particles and the surrounding fine soil particles connecting these soil particles.

A stiffening material having a small slump value, preferably an improved material (self-hardening material) having a size of 15 cm or less, is pressed into the loose ground so as to be gradually deposited from the bottom of the mud column composed of the loose ground. I do. By this press-fitting, the improvement material is injected so as to push the loose ground. When the improving material according to the present invention uses a stiffening material, particularly one having a slump value of 15 cm or less, escape of the improving material is prevented,
The loosened ground part is completely replaced by the improving material, and the pressing force of the improving material consolidates the ground part. However, since the degree of loosening of the ground is small, the amount of press-fitting of the improving material is small, so that an improved body having uniform strength and uniform diameter as a whole can be formed.

On the other hand, it is possible to sufficiently cope with the use of relatively thin pipes, for example, those having a diameter of about 100 mm, so that the equipment cost is lower than that of the high-pressure injection method or the stirring method.
It will be cheap. Moreover, since only high-pressure water is used to loosen the ground, the slime is not a mixture of cement and soil particles as in the high-pressure injection method, but a mixture of water and soil particles. There is an advantage that is easy. In addition, as described later, when a mixture of water and soil particles is used, it is separated and water (which may contain fine particles) may be used again for relaxing the ground or dispersing the self-hardening material. As a result, the amount of waste liquid can be reduced,
Slime processing costs can be significantly reduced.

Further, the present invention can be easily applied to sandy ground, and this point has a remarkable difference from the conventional stirring method. In addition, since the relaxation of the target area of the ground and the press-fitting of the improvement material are performed in a separate step or another stage, the variation in the improvement strength seen in the high-pressure injection method is eliminated.

In the present invention, the most characteristic feature of the present invention, as compared with the invention of the prior application, is that, first, the overhanging injection into the injection pipe is performed.
Providing the elevation section, this protruding injector than or lower injection pipe to a second, providing an injection nozzle for injecting high pressure water covers the ground area of the protruding length of the at least projecting jetting portion It is.

As described above, in order to loosen the target ground to a large diameter by simply injecting high-pressure water from the high-pressure water injection nozzle provided on the outer peripheral surface of the tip of the injection pipe, the pressure is increased to increase the discharge flow rate. Or reducing the nozzle diameter to increase the pressure and decrease the discharge rate. However, in the case of the former, the amount of discharged mud is increased, and the cost of discharging mud is increased. In the latter case, after the high-pressure water is discharged into the ground, the energy of the high-pressure water rapidly decreases, and there is no sufficient ground relaxation effect.

However, according to the present invention, when the overhanging injection portion protruding from the outer surface of the injection tube is provided and the injection nozzle is provided at the overhanging injection portion, even if the reaching distance of the high-pressure water from each injection nozzle is short, The reaching distance based on the axis can be lengthened, so that without increasing the pressure or reducing the nozzle diameter, and without further increasing the discharge flow rate, at least the projecting length region of the overhanging injection unit is surely The ground can be relaxed.

If the injection nozzle is provided in a radial direction at a position below the overhanging injection portion on the outer surface of the injection pipe, there is no advantage in terms of reach. However, in this case as well, in the former case, if there is an overhanging injection unit,
If the injection pipe cannot be inserted into the ground, since the ground is not relaxed at the depth position, the overhanging injection part appears as resistance to the ground, and a judgment index of whether the ground is loose or not. can do. Conversely, when the injection pipe cannot be inserted into the ground as described above, measures such as reducing the rotation speed of the injection pipe, decreasing the descent speed, and increasing the pressure or flow rate of high-pressure water from the injection nozzle are given. By adopting, the ground can be surely relaxed at least up to the projection length of the overhanging injection portion. Furthermore, in both cases, since the overhanging injection part also has a stirring effect to some extent as in the case of the stirring blade, there is also an advantage in that the ground is relaxed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings and specific examples. 1 and 2 show a first specific example, in which 3A is an injection pipe, which has a drill bit on the front face of the tip, has a high pressure water injection nozzle 31A on the peripheral wall of the tip, and further has an injection nozzle of the injection pipe 3A. In the upper part of 31A, there is provided an overhanging injection part 30 projecting to the outside of the pipe at least in a state of expanded diameter injection, and injects high-pressure water to the overhanging injection part 30 outward with respect to the improved axis. An injection nozzle 31B is provided, and a spout 32 for a self-hardening material is formed on the tip side of the injection nozzle 31A.

As shown in FIG. 1, first, high-pressure water is injected from the first injection nozzle 31A by using the injection pipe 3A, and the reaching distance thereof is equal to or longer than the length of the overhanging injection unit 30. The injection pipe 3A is inserted to a certain depth in the ground while rotating. At this time, if necessary, spout 3
2 can discharge the drilling water. The injection of high-pressure water, mud pillars ground is expressed as to the primary relaxation zone S ₁ relaxation is Construction.

Next, when a certain depth is reached, FIG.
As shown in, while raising rotating the injection pipe 3A, to inject high-pressure water from only the second jetting nozzle 31B, secondary relaxation zone to form a S ₂ to the outside of the primary relaxation zone S _1, the spout 32, the self-hardening material G is press-fitted. The improved body A is formed from the self-hardening material G to a certain length.

The high-pressure water W is supplied from both injection nozzles 31A and 31B.
Is a pressure corresponding to the properties of the ground (soil, softness, etc.) and the desired improved diameter, preferably a pressure of generally 50 kg / cm ² or more, particularly preferably a pressure of 80 to 350 kg / cm ² Can be. When the improvement area is below the groundwater level, the reach of high-pressure water is significantly reduced, for example, 200 kg /
Even if the jet is injected at a pressure of ² cm, the improved diameter is about 40 cm. Therefore, as in the jet grouting method, the injection pipe 2 is formed as a double pipe, and the injection air is extended around high-pressure water to reach the distance. It can also be increased.

In the process of raising the injection pipe 3A, a self-hardening material G having a slump (JIS A 1101) of 15 cm or less is press-fitted from the spout 32 at the tip while forming a loose ground outside the overhanging injection section 30. The improved body A is formed. This improved A
Can be made to the ground surface or to a certain depth.

In this case, the suitable lower limit of the slump value of the self-hardening material is 5 cm or more, more preferably 8 cm or more. In addition, the injection of the self-hardening material is performed while gradually raising the injection pipe 3A upward from the bottom of the mud column,
The self-hardening material G is filled so as to be gradually deposited from the bottom. In addition, it is preferable to perform press-fitting while maintaining the immersion length of the injection pipe 3A in the self-hardening material G. The immersion length is preferably at least 30 cm, more preferably at least 50 cm. The press-fitting of the self-hardening material may be performed over the entire improved length while maintaining a certain depth position, or may be performed while continuously or intermittently pulling up the injection pipe. When the ground is not relaxed during the lifting process, the self-hardening material can be pressed in without rotating the injection pipe.

FIGS. 3 and 4 show the manner in which the self-hardening material G is press-fitted. 4 in FIG. 4 indicates aging. From these drawings, it will be understood that when the self-hardening material of the present invention is pressed, the material is pressed into a cream. In the present invention, as the self-hardening material, a self-hardening material such as a cement mortar type, a cement clay type, and a lime type can be used. As described above, a material having a high viscosity or a hardened material is used. Among them, cement mortar is most preferable, and other inorganic materials such as fine particle slag and bentonite, and various additives such as a foaming agent, a foaming agent, a separation preventing agent, and a water reducing agent can be added thereto. . Furthermore, water glass and its hardener can be added in a certain ratio.

FIG. 5 shows an example of the structure of the injection pipe 3A. 33
Is an inner tube, 34 is an outer tube, and 35 is a channel member for dividing a channel.

As shown in FIG. 6, a plurality of, for example, two overhanging injection portions of the present invention can be provided separately in the depth direction. In this case, the high pressure water from the first injection nozzle 31A, the high pressure water from the second injection nozzle 31B, the high pressure water from the first injection nozzle 31A, and the high pressure water from the second injection nozzle 31B, respectively, are relaxed. It is promised that the high pressure water from the third injection nozzle 31C will eventually form an improved body having a radius larger than the overhang length of the overhang injection section 30B.

In each of the above examples, the spray nozzles are provided in the radial direction, and cover the upper overhanging spray portion to relax the ground. On the other hand, as shown in FIG. 7, for example, an overhanging injection unit 30C formed by triangular blades is provided, and injection nozzles 31E, 31E... Provided obliquely downward or completely downward as shown in FIG. An example in which high-pressure water is injected from the injection nozzle 31D of the outermost diameter portion to the periphery in order to relax the injection tube 3C for insertion and further increase the improved diameter can be adopted.

Further, as shown in FIG.
Are provided on the lower surface of the nozzle 0, and can be used for relaxation for inserting the injection pipe 3C. Also in this case, the injection nozzle 31 can be provided in the overhanging injection part 30 as needed.

FIG. 9 shows an example in which a stirring blade 40 is provided further above the overhanging injection section 30 provided above the injection nozzle 31. In this example, the loosened ground is further loosened by the stirring blade 40.

In the above example, the overhanging injection portion protrudes outward from the pipe from the beginning, but it is sufficient that at least the overhanging injection portion protrudes outward from the pipe in the state of expanded diameter ejection. As shown in FIG. 10 and FIG. 11, when the protrusion does not protrude to a certain depth and reaches a predetermined depth, for example, the blade 41 of the wing-spread link mechanism constituting the overhanging injection part of the present invention.
, The wing expanding link mechanism blade 41 can be expanded as shown in FIG.拡翼linkage blade 41 may拡翼by pushing the outer tube 42 from the ground. 43 is a drilling blade.

When only a certain length portion in the depth direction in the ground is relaxed to expand the diameter, as shown in FIG. 12, the diameter of the hole at the mouth is small and the diameter of the improved body forming portion is large. be able to.

In the above example, the distance between the lowermost injection nozzle and the self-hardening material spout 32 should be at least 50.
When about cm, preferably 1 m or more is secured, there is no interference between the high-pressure water and the self-hardening material G, and a good improved body can be obtained.

In the present invention, the pressure of the high-pressure water is
It usually refers to the pressure of a gauge provided near the injection pipe or on the outlet side of the injection pump. The pressure is 50 kg / cm ²
Although it is preferable to set it as above, in some cases, 100 kg / cm ²
It may be preferable to make the above. The injection amount is preferably 5 to 150 l / min, and more preferably 10 to 100 l / min. The injection pipe of the present invention preferably has an outer diameter of usually 120 mm or less, particularly preferably 100 mm or less.

On the other hand, as high-pressure water for relaxing the ground,
Although the use of water is preferred in terms of availability and cost, the addition of a surfactant to water increases the machinability of the ground. Further, after the mud generated by the injection of the relaxed / self-hardening material is separated into a supernatant and a concentrated mud, the supernatant can be used. For example, as shown in FIG. 13, a mud pit 50 is provided at the mouth of the high-pressure injection pipe 3 </ b> A.
The mud 51 that has risen between A and the hole wall is pumped up by a pump 52 and separated into a supernatant 51A and a concentrated mud 51B by a separator 53, and the supernatant 51A is temporarily stored in a tank 58 by a pump 54. Store and use as high-pressure water for subsequent loose mud column formation. When the supernatant is used for cutting, small particles are included, so that the cutting property is improved. On the other hand, the concentrated mud 51B passes through the hopper 55,
After being supplied to the mixing drum 56 and mixed therewith with the self-hardening material G, the high pressure injection pipe 3A
Can be supplied as a self-hardening material for filling or replacement. Further, when the concentrated mud is reused, muddy water treatment is reduced correspondingly. In addition, the mud 51 can be added to the self-hardening material G without processing.

According to the present invention, a high-strength improved body can be obtained, so that a high-strength pile can be formed. In addition, by continuously connecting the piles, as shown in FIG.
Pillar piles or pillar rows (continuous walls) can also be created. In this case, the improved body is formed only by the self-hardening material, and the improved body is reinforced by inserting one or a plurality of reinforcing bars or appropriately shaped steel (referred to as reinforcing bars) into the improved body. Is preferred. Furthermore, according to the present invention, in forming the pillar row or pillar row wall, the injection pipe of a small diameter is sufficient, so that a plurality of injection pipes are gripped by a single elevator, and the descent and rotation pulling up during press-fitting are performed. Can be done.

[0040]

As described above, according to the present invention, the improvement strength is increased, the construction can be performed with simple and small equipment, and the uniform and strong improvement limited only by the consolidation effect or only at the intended portion is achieved. Advantages are obtained such that the body can be formed, and further, the diameter of the improved body can be increased, and particularly, an improved body having a uniform improved diameter can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a first step showing a first specific example in the order of construction.

FIG. 2 is a schematic diagram of a second step showing a first specific example in the order of construction.

FIG. 3 is a schematic diagram of a press-fit state of a self-hardening material.

FIG. 4 is a schematic sectional view of a press-fitting mode of a self-hardening material.

FIG. 5 is a longitudinal sectional view of a main part of a structural example of an injection tube.

FIG. 6 is another view of a modified example of the injection tube.

FIG. 7 is another view of a modified example of the injection tube.

FIG. 8 is a diagram of still another example of the injection tube.

FIG. 9 is a schematic view of an example of an injection tube having an agitating blade.

FIG. 10 is a schematic diagram of an example of a wing expansion type.

FIG. 11 is a state diagram of a wing-spread type example.

FIG. 12 is a schematic view of another example of a ground improvement mode.

FIG. 13 is a schematic diagram of an example of reusing mud.

FIG. 14 is a plan view of a formation mode of a pillar row and a pillar wall.

[Explanation of symbols]

3A: injection tube, 30, 30A, 30B: overhanging injection unit, W
... high-pressure water, G ... self-hardening material.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masatoshi Ogita 3-19-19 Higashi 3-chome, Kunitachi-shi, Tokyo (56) References JP-A-5-255925 (JP, A) JP-A-57-3911 ( JP, A) Special Table 63-503230 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) E02D 3/12 101

Claims (3)

(57) [Claims] At least one overhanging projection is provided at the distal end of the injection pipe so as to protrude outward from the pipe in at least the expanded diameter ejection state, and at least the overhanging injection projection is provided at the overhanging injection part or at a lower injection pipe. An injection nozzle that covers the ground area for the length and injects high-pressure water is provided, and a spout of self-hardening material is formed on the tip side from the lowermost injection nozzle.
Is inserted into the ground, while at least a certain depth at a given depth customers, said by injecting high pressure water from the injection nozzle, relaxed by relaxing the ground region of the projecting length of the at least the projecting jetting portion mud After forming the column, at the position where the predetermined depth is reached or in the process of raising the injection pipe, from the spout, a hardened self-hardening material is pressed into the loose mud column to form an improved body. Improvement or strengthening of the ground. 2. The method for improving or strengthening the ground according to claim 1, wherein said injection nozzle is provided on the overhanging injection portion so as to face downward. 3. The method of improving or strengthening the ground according to claim 1, wherein the injection nozzle is provided in a radial direction at a position below the overhanging injection portion on an outer surface of the injection pipe.