JP4740571B2 - Ground improvement method - Google Patents

Description

The present invention relates to a ground improvement method using a high-pressure jet agitator that injects a ground improvement material such as a solidified material slurry into the ground such as soft ground and mixes the solidified material slurry and the soft ground. It is.

In the ground improvement method in which ground improvement materials such as solidification materials are mixed and stirred into the ground, since the solidification material slurry equivalent to the volume of the solidification material mixed in is pushed in, the deformation in the soil is propagated to the surrounding ground and displaces to the surrounding ground. Bring.
In addition, the earth auger shaft is configured in the shape of a screw auger, and the soil is forcibly discharged to the ground surface by rotating and moving up and down. There is a known method for preventing this. However, this method is limited to the case where the shaft drive unit is at the upper part, and there is a problem that it cannot be applied to the lower drive type or boring type small machines.

In addition, in advance of the planned injection injection pile placement position for soft ground to be improved, disturb the mixture with the turbulent blades in advance, and install the injection injection pile into at least every other columnar disturbance part to inject the solidified material. A method of forming a pile that does not cause ground displacement has been proposed (see, for example, Patent Document 1), but there is a possibility that it cannot be sufficiently absorbed only by the formation of the disturbance part.
Japanese Unexamined Patent Publication No. 60-59222

In order to solve the above problems, the injection rod penetrates into the ground of the planned improvement ground, and the disturbance layer formed by disturbing the soil with the disturbance device of the injection rod, or the solidified material slurry is injected at high pressure on the outer periphery of the disturbance layer. When forming the cylindrical improvement body by pouring, the soil is pushed up by the soil push-up disk provided close to the top of the solidifying material slurry injection part of the pouring rod to raise the disturbed soil in the vicinity of the solidifying material slurry injection port. A ground improvement method that forms a gap below the push-up disk, absorbs the mixed soil mixed with the solidifying slurry into the gap, and prevents displacement movement to the surrounding ground (for example, Patent Document 2, Non-Patent Document 1). We have proposed).
Japanese Patent No. 2737602 Brochure "LDis Method" Onoda Chemico Co., Ltd.

  However, in the above patent invention proposed by the present inventors, the shape of the soil lifting disk to be used was not particularly specified. Therefore, when the above construction method is performed, soil lifting disks having different specifications are used. Produce a large number of soil, and in consideration of the target ground, the amount of solidified material slurry injected, the amount of soil removed, etc., select a soil lifting disk with an appropriate size and shape to obtain the optimum amount of soil removed after trial and error. It was improved and used.

  For this reason, the first few constructions at each site require time and labor, such as confirming the soil removal status and selecting the soil lifting disk, which is inefficient, and the most efficient soil removal for reducing displacement. The development of the shape of the soil push-up disk that can be used has been desired.

  In addition, the soil removal method during drilling is only effective to reduce displacement by only disclosing the general method of pushing up the disturbed soil in the vicinity of the hardener slurry injection port and discharging it with a soil lifting disk. The concrete soil removal procedure is also in a trial and error state, and the probability of the most efficient drilling method has been demanded.

The ground improvement construction examples according to the above-mentioned patented invention proposed by the present inventors have also been accumulated, and as a result of earnestly examining these many construction example cases, in regard to the shape of the soil push-up disk, the penetration and lifting resistance, the amount of soil removal, etc. It has become clear that there is an optimal shape.
In addition, the most effective soil removal method for displacement reduction has been established.

  The approximate optimum shape of the soil push-up disk is that the radius of the projected plane shape of the soil push-up disk provided close to the upper part of the solidifying material slurry injection part of the pouring rod is the horizontal stirring blade of the pouring rod. The same size as the radius of the circle of the circular trajectory drawn by the rotation of the above, or 10 cm or less, preferably 5 cm smaller than the stirring blade, and the diameter of the projected planar shape of the soil lifting disk is 40 cm or more and less than 90 cm depending on the mechanical capacity The soil uplift disk can be selected.

  In addition, as a drilling soil removal method, the step length in the depth direction corresponding to the amount of soiling that can be performed by one drilling and extraction is appropriately set according to the soil quality, and the excavating blade at the tip of the injection rod of the single pipe is set. A stirring device in which a spiral soil lifting disk having a radius smaller than the diameter of the stirring blade is disposed adjacent to the upper portion of the stirring blade provided in the upper portion, and the ground to be improved is drilled to the first step depth. After drilling the water while jetting water at a low pressure, the soil is extracted by a length corresponding to the depth of one step, and then drilled to the lower end of the second step depth, and while drilling the water at low pressure. Then, the soil corresponding to the depth of one step (second step depth) is extracted and evacuated. This is repeated for each step, drilled to the depth to be improved, and then the rod is pulled out to the ground and further improved. Re-drill to the planned depth and then slurry How the Jo of solidifying material coming pulled while spraying laterally from the nozzle in the vicinity of the rod tip it was found to be most effective displacement reduction.

  When the injection rod is penetrated while being rotated into a predetermined soft ground, a disturbance layer is formed in the soft soil by the stirring blade along with the rotation penetration of the injection rod. At this time, since the radius of the disturbance part formed by the stirring blade is the same as the radius of the soil push-up disk or 10 cm or less, preferably 5 cm from the stirring blade radius, there is a gap on the outer peripheral surface of the disturbance part. The hole water enters the gap and is mixed with the disturbed soft soil.

  Then, the soft soil in the gap is particularly disturbed to become mud, thereby forming a thin cylindrical mud film region. For this reason, when the pouring rod is pulled out in a stepped manner while rotating into the soft ground, the soft soil included in the diameter of the soil push-up disk and the region outside the diameter are cut off. At that time, due to the rotation of the soil push-up disk, the shear resistance of the soil when the soft soil contained in the diameter is pushed upward is reduced, and reliable earth removal is possible.

  Further, the shape of the soil lifting disk at this time is such that the radius of the projected plane shape is the same as the radius of the edge of the circular locus drawn by the rotation of the stirring blade or 10 cm or less, preferably 5 cm smaller than the stirring blade radius, And in the soil push-up disk shape, the inclination of the spiral soil push-up disk is 10 to 20 degrees, and the projection shape is overlapped with a fan shape having a central angle of about 10 degrees in addition to the circumference of the circumference, Or, when it is approximately one circumference, the effect of pushing up (discharging) the soil is the largest.

Note that if the radius of the soil push-up disk is larger than the radius of the stirring blade by 10 cm or more, the cylindrical mud film due to edge cutting becomes larger and easily collapses. Without increasing the shear resistance (of the injection rod), preventing smooth rotation and reducing the edge cutting effect.
Furthermore, when the diameter of the soil push-up disk is less than 40 cm, even if there is a muddy water film, the resistance of the peripheral area is large and the soil removal efficiency is poor.
Moreover, when the inclination of the spiral soil lifting plate is 10 to 20 degrees, the soil removal efficiency is good. If the inclination is less than 10 degrees, the soil removal efficiency is good, but the soil does not rise easily because it becomes resistance during penetration work, and if the inclination exceeds 20 degrees, the soil will slide down from the disk (resistance increases). There is a problem that the soil effect becomes worse.

  In this way, the fluidized mixed soil mixed with the solidifying material slurry is absorbed into the void formed by discharging the raw soil not containing the solidifying material slurry by the soil lifting disk, and the ground at the center of the injection rod In addition, since the amount of discharged soil is substantially equivalent to the volume of the injected injected solidified material slurry, displacement to the surrounding ground is most effectively reduced.

When the ground improvement device of the present invention is used, the radius of the soil lifting disk is the same size as the stirring blade radius of the soil removal mechanism or 10 cm or less, preferably 5 cm smaller than the stirring blade radius, and the inclination of the spiral soil lifting plate Is 10 to 20 degrees, the projection shape is added to the circumference of the circle and the central angle is overlapped with the fan shape of the center angle of 10 degrees, or by the effect of the soil push-up plate for the circumference of one circumference, the disturbance part in the drilling A cylindrical muddy water film is formed between the soil and the surrounding soft ground, and the soil is reliably discharged, so that adverse effects such as displacement on the surrounding ground can be reliably prevented.

  In addition, when the step lifting is improved, the mixed soil improved by mixing with the solidifying material slurry wraps around the stirring blades around the rod to be pulled up and the space immediately below the soil lifting disc, so the center of the rod is also improved. A uniform improved body can be created as compared with the solidified material slurry injection region on the outer periphery of the body.

  Furthermore, since the solidified material slurry is not mixed in the soil discharged to the ground surface by the soil push-up disk, it can be treated or diverted in the same manner as general residual soil treatment.

  An embodiment of the present invention will be described with reference to the drawings. The same reference numerals have the same names and functions.

FIG. 1 schematically shows the trend of the rod tip in the ground drilling method in the apparatus used in the method of the present invention. In this figure, the drilling length per step is drawn constant. However, in the implementation, the optimal step length with good soil removal efficiency should be set for each soil type according to the soil layer condition. Can be set arbitrarily.
Referring to FIG. 1, in each step, once the first step length has been drilled, the rod is once raised by the first step, then drilled to the lower end of the second step, and again the lower end of the first step. Pull the rod up to.

  When the rod is pulled out, the soil is pushed up by the soil push-up disk to push up the disturbed soil in the vicinity of the solidifying material slurry injection port and the soil is discharged. Repeat this until the nozzle position reaches the lowest end (nth step) of the drilling length. Once the rod is pulled out to the ground and drilled again to the planned depth, it reaches the planned depth. A slurry-like solidified material is pulled out from the nozzle of the stirring blade provided near the tip of the rod while high-pressure jetting to the side to create an improved column.

2 to 3 show an apparatus used in the construction method of the present invention and an example of the earthing situation. In FIGS. 2 and 4, reference numeral 1 denotes a rotary up-and-down moving mechanism, and the support rod is capable of rotating the injection rod 2 up and down. 4 to support. The upper end of the single tube injection rod 2 is connected to a solidified material slurry pressure feeding hose 9 via a swivel 8.
A drilling blade (earth auger) 3 and a stirring blade 5 constituting a disturbance device are provided at the lower end portion of the single tube injection rod 2, and a solidifying material slurry injection nozzle 10 is provided on the shaft portion and the stirring blade 5.
When the injection rod 2 is pulled up in the vicinity of the upper part of the stirring blade 5 by a step method, a soil lifting disk 6 is provided for pushing up the soil disturbed by the stirring blade 5 upward. The soil push-up disk 6 has the same radius as the radius of the stirring blade 5 or the stirring so as to maximize the soil removal efficiency when the injection rod 2 penetrating into the ground is pulled up. It is formed to be 10 cm or less than the blade radius, preferably 5 cm smaller, and the inclination of the soil push-up disk is 10 to 20 degrees, preferably 15 degrees in the projected plane shape, and the projected shape is circumferential as shown in FIGS. In addition to one round, it is overlapped with a fan shape with a central angle of about 10 or formed so as to be substantially one round.

When the single tube injection rod 2 configured in this manner is rotated and penetrated into the soft ground 11 while jetting the drilling water at a low pressure, the disturbing portion 16 formed by the stirring blade 5 along with the rotation penetration of the injection rod 2. However, since it is 10 cm or less, preferably 5 cm larger than the radius of the soil push-up disk 6, the region of the cylindrical mud film 12 is formed by the disturbed soil and the drilling water.
Therefore, when the injection rod 2 is pulled out from the soft ground 11 by the step-up method, the soft ground included in the diameter of the soil push-up disk and the region outside the diameter are cut off. At that time, due to the rotation of the soil push-up disk 6, the shear resistance when the soft soil contained in the diameter is pushed upward is reduced, and the soil can be discharged 17 reliably.

  FIG. 4 shows an apparatus used in the method of the present invention and an improved embodiment. FIG. 5 is a cross-sectional view of the improved body formed in FIG. 4, and 15 in the figure is an improved portion. The improved mixed soil mixed with the solidifying material slurry 14 wraps around the gap 7 that is formed immediately below the soil lifting disk 6 around the rod 2 that is pulled up in a stepped manner.

2 to FIG. 3 or FIG. 4 to FIG. 5 in the construction stage, for example, when the diameter of the stirring blade 5 having the injection nozzle 10 is 50 cm or more and 100 cm, the solidified material of the injection rod 2 The soil push-up disk 6 provided close to the upper part of the slurry injection unit 10 has a radius of the projected plane shape of the soil push-up disk 6 equal to the radius of the circular locus drawn in the rotation of the stirring blade 5 or The diameter of the projected plane shape of the soil lifting disk 6 is 10 cm or less, preferably 5 cm smaller than the stirring blade radius, and is formed on a soil lifting disk having a diameter of 40 cm or more and less than 90 cm.
In the figure, 6a is a lower disk surface constituting a spiral soil lifting disk, and 6b is an upper disk surface formed in a fan shape.

It is the figure which showed typically the accompaniment of the rod front-end | tip part in the ground drilling method using the improvement apparatus of this invention. It is sectional drawing which shows the apparatus of the Example used for the construction method of this invention, and the soil removal condition. It is a top view of the attachment state of a soil pushing-up disk same as the above. It is sectional drawing which shows the apparatus of the Example used for the construction method of this invention, and the improvement condition. It is sectional drawing of the improved body same as the above. It is a front view of the apparatus of the other Example used for the construction method of this invention. It is a side view same as the above. It is a top view of a soil pushing-up disk same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation vertical mechanism 2 Single pipe injection rod 3 Excavation blade (earth auger)
4 Struts 5 Stirring Blades 6 Soil Pushing Disk 6a Lower Disk Surface 6b Fan-shaped Overlapping Upper Disk Surface 7 Cavity 8 Swivel 9 Pressure Hose 10 Nozzle 11 Soft Ground 12 Cylindrical Mud Water Film 13 Soil Destination 14 Spray Hardening Material slurry 15 Improvement section 16 Disturbance section 17 Earth removal

Claims (4)

Adjacent to the upper part of the stirring blade provided at the top of the excavating blade at the tip of the single tube type injection rod, it has the same dimension as the radius of the stirring blade or a radius smaller than the stirring blade radius by 10 cm or less, and is a spiral circle. The inclination of the plate is 10 to 20 degrees, and the projection shape is overlapped with a fan shape having a central angle of about 10 degrees in addition to the circumference of the circumference, or a soil push-up disk of about one circumference is provided. In the agitator , the ground is drilled to a predetermined depth by the excavating blade, and the outside of the agitating blade is cut and mixed with the energy of the solidified slurry injected at high pressure into the ground through the injection rod. A disturbed soil in the vicinity of the solidifying material slurry injection port is pushed upward by a soil lifting disc provided in the vicinity of the upper portion of the solidifying material slurry spraying unit, and a void is formed below the soil lifting disc, thereby solidifying slurry. The mixed soil mixed with Absorbing, in method of construct a cylindrical improvement body in improvements scheduled ground to;
The drilling method up to the planned improvement depth is a multiple-step drilling method.
The step length in the depth direction corresponding to the amount of soil that can be drilled and pulled out at the time of drilling is appropriately set according to the soil quality, and the drilling water is injected at low pressure up to the set first step depth. After drilling, the length corresponding to the depth of one step is extracted and evacuated to the bottom of the next second step depth. And excavating and excavating for the length to be drilled, repeating this step for each step, drilling and excavating to the planned depth of improvement,
Next, pull out the rod once to the ground,
Furthermore, after re-drilling to the planned depth for improvement,
From the nozzle of the stirring blade provided near the tip of the rod that has reached the planned depth ground, the slurry-like solidified material is pulled out while being high-pressure jetted to the side to create a cylindrical improvement body. Improved construction method. The ground improvement method according to claim 1 , wherein a radius of the soil push-up disk is 5 cm smaller than a radius of the stirring blade. The ground improvement method according to claim 1, wherein the inclination of the soil push-up disk is 15 degrees . A raw soil dumping does not contain a solidifying material slurry is earth removal by the soil pushed up disc claim 1 in which the soil removing amount is characterized Oh Rukoto stands volume equivalent injection injection solidifying material slurry 2. Ground improvement method according to 2 or 3.

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