JP7561516B2 - Mechanical mixing method - Google Patents

Description

The present invention relates to a mechanical mixing method used in a mechanical mixing type ground improvement method in which a mixing blade device and a nozzle are attached to the tip of various construction machines, and the slurry is mixed and stirred with the in-situ soil while being injected into the construction ground, forming a ground improvement body in the construction ground. In particular, the present invention relates to a mechanical mixing method that mixes the slurry and the in-situ soil with high mixing efficiency to build a high-quality ground improvement body with high uniformity.

Conventionally, a mechanical mixing type ground improvement method has been known in which a mixing blade device and a nozzle are attached to the tip of various construction machines, and a cement slurry containing cement and water is injected into the construction ground while mixing and mixing the cement slurry with the existing soil, thereby constructing a ground improvement body in the construction ground. This type of method is proposed in Patent Document 1.

Patent Document 1 relates to a management system for a mixing and stirring device, and in this document, the so-called WILL
The method is disclosed.
In this WILL method, a construction machine such as a backhoe is used as the base machine, and while injecting solidification material slurry from the tip of a vertically rotating mixing device attached to the end bracket of the base machine's arm, the mixing device penetrates into the soft ground from the ground surface, and while pulling it out, the soft soil and solidification material are mixed and mixed, and the soft ground is solidified to improve the ground. The mixing device used in this WILL method has multiple mixing blades that rotate vertically on both the left and right sides of the tip, and while penetrating and pulling the mixing device into the ground, each mixing blade at the tip is rotated, and solidification material slurry is injected from the vicinity of the blades, thereby mixing and mixing the soil to be improved and the solidification material.
As disclosed in Document 1, the WILL method employs a high-performance WILL method management system that can manage the depth, rotation speed, and excavation angle of the impeller, the trajectory of the impeller, and the flow rate of the solidification material slurry in real time.

This type of construction method has also been proposed in Patent Document 1, as well as Patent Documents 2 and 3.

Patent No. 4954166 Patent No. 4038525 Patent No. 3958347

However, in the above conventional mechanical mixing type ground improvement method, when improving soft ground, especially when the ground has high adhesive strength, a long mixing time is required to sufficiently mix the ground, which increases costs and places a heavy burden on the construction period and economy. In this type of method, in order to improve the construction speed, it is necessary to increase the amount of slurry injected per unit time and increase the mixing efficiency (early homogeneity) between the slurry and the ground to ensure good quality (early homogeneity) of the ground improvement body in a short construction time. However, in the conventional method, a certain quality of the ground improvement body is obtained by injecting the slurry into the ground using one pump and a nozzle at the tip of the mixing and mixing device, and mixing the slurry and the ground with the mixing blade at the tip for a predetermined time. Therefore, if the amount of slurry injected is increased to shorten the mixing time in order to achieve high-speed construction, the quality of the ground improvement body will decrease, such as the strength of the ground improvement body being insufficient or the homogeneity being reduced.

In addition, with this mechanical mixing ground improvement method, there is a growing need to shorten construction time and improve cost-effectiveness for a variety of grounds, including sandy soil and gravel ground in addition to clayey soil, and similar issues as those mentioned above exist for various other construction grounds, such as sandy soil and gravel ground.

The present invention aims to solve such problems in the past, and to provide a multi-directional slurry injection mechanical mixing method that increases the amount of slurry injected per unit time and improves the mixing efficiency of the slurry and the construction ground in this type of mechanical mixing ground improvement method, thereby ensuring good quality (early homogeneity) of the ground improvement body in a short construction time.

In order to achieve the above object, the present invention provides
In a mechanical mixing method, a mixing blade device for mixing the ground and a nozzle for spraying slurry are attached to the tip of a construction machine, and the slurry and in-situ soil are mixed while being injected into the construction ground.
The agitator blade device is a vertical rotation type agitator blade device having a pair of agitator blade units rotatably attached to the tip of a construction machine via a rotating shaft, the pair of agitator blade units having two agitator blades symmetrically arranged around the axis of the rotating shaft, with the axis of the rotating shaft being the center of symmetry, and one of the two agitator blades is arranged diagonally around the rotating shaft with one end facing forward facing outward and the other end facing inward, as viewed from the front, and the other is arranged diagonally with one end facing backward facing inward and the other end facing outward, and a plurality of agitator claws are arranged on the outer peripheral surface of each agitator blade ,
The nozzles are provided above and below the rotating shaft of the pair of mixing blade units , the upper nozzle is arranged so that the direction of spraying the slurry from the nozzle is approximately vertical to the construction ground, a high-pressure pump for feeding the slurry is connected to the upper nozzle , the lower nozzle is arranged so that the direction of spraying the slurry from the nozzle is approximately horizontal to the construction ground, and a low-pressure pump for feeding the slurry is connected to the lower nozzle ,
When the construction ground is stirred by the stirring blade device, the pair of stirring blade units stirs and mixes the construction ground in the up-down, front-back and left-right directions, while the high-pressure pump supplies the slurry to the upper nozzle at high pressure and sprays it from the nozzle toward the construction ground at high pressure, and the low-pressure pump supplies the slurry to the lower nozzle at low pressure and sprays it from the nozzle toward the construction ground at low pressure , thereby increasing the amount of slurry injected into the construction ground and injecting the slurry while loosening the in-situ soil of the construction ground with the slurry injection pressure.
The gist of the present invention is as follows.
In this case, it is desirable that the diameter of the slurry discharge port of the upper nozzle is approximately 4.5 mm, and the injection pressure of the slurry from the upper nozzle is 10 MPa to 15 MPa .
In this regard, the tip of the construction machinery refers, for example, in the case of a backhoe, to the tip of the arm connected to the boom that extends forward from the front of the rotating part that has the driver's cab; in general construction machinery, this is the part where the mixing blade device for mixing the ground is attached.

In the mechanical mixing method of the present invention, when the construction ground is mixed with the mixing blade device, the pair of mixing blade units mix and mix the construction ground in the vertical, front-back and left-right directions, while the high-pressure pump sends the slurry to the upper nozzle at high pressure and sprays it from the nozzle toward the construction ground at high pressure, and the low-pressure pump sends the slurry to the lower nozzle at low pressure and sprays it from the nozzle toward the construction ground at low pressure , thereby increasing the amount of slurry injected into the construction ground, and injecting the slurry while loosening the in-situ soil of the construction ground with the injection pressure of the slurry. Therefore, in a commonly used mechanical mixing type ground improvement method, the amount of slurry injected per unit time can be increased and the mixing efficiency of the slurry and the construction ground can be improved, and this increase in the amount of slurry injected and the improvement in mixing efficiency ensure good quality (early homogeneity) of the ground improvement body in a short construction time, which is a unique and exceptional effect of the present invention.

FIG. 1 is a diagram showing an image of a multi-directional slurry jet mechanical mixing method according to one embodiment of the present invention. FIG. 1 is a diagram (front view) showing the configuration of a vertical rotation type mixing blade device used in the method. FIG. 1 is a diagram (side view) showing the configuration of a vertical rotation type mixing blade device used in the method. The figure shows an example of construction using this method, in which the backhoe is moved to the construction site and stopped at a position where the mixing blade device can be set at the excavation and mixing position of the construction site. This figure shows an example of construction using the method, in which the arm is lowered and a pair of vertically rotating mixing blade units is inserted vertically into the construction ground while the slurry fed to each nozzle by each high-pressure pump is high-pressure sprayed from each nozzle toward the construction ground. The figure shows an example of construction using the method, in which the arm is further lowered to excavate and mix the construction ground with a pair of vertically rotating mixing blade units, and the slurry fed to each nozzle by each high-pressure pump is sprayed from each nozzle at high pressure into the construction ground to mix and mix the in-situ soil and the slurry. A diagram for explaining the action of the mixing blade device, multiple nozzles, and high-pressure pump used in the method. Figure showing the results of field testing of this method

Next, a multi-directional slurry injection mechanical mixing method (hereinafter, simply referred to as this method) according to one embodiment of the present invention will be described with reference to the figures. Figure 1 shows this method, and Figures 2 and 3 show the configuration of the mixing blade device and multiple nozzles used in this method.

As shown in Figure 1, this method is a mechanical mixing method in which a mixing blade device 1 for mixing the ground and a nozzle 2 for spraying the slurry are attached to the tip of a construction machine M, and the slurry is injected into the construction ground while mixing and mixing the slurry and the in-situ soil.

In this method, multiple nozzles 2 are arranged around the mixing blade device 1, with each nozzle 2 spraying slurry in multiple different directions relative to the construction ground, and a high-pressure pump 3H is connected to each nozzle 2 for supplying the slurry. In this way, when the construction ground is mixed with the mixing blade device 1, the slurry is supplied at high pressure by the high-pressure pump 3H to each nozzle 2 around the mixing blade device 1, and is sprayed at high pressure in multiple directions from each nozzle 2 around the mixing blade device 1 to the construction ground, thereby increasing the amount of slurry injected into the construction ground and loosening the in-situ soil of the construction ground with the slurry spray pressure.

Figure 1 shows this method in more detail. As shown in Figure 1, a backhoe (hereinafter referred to as backhoe M) is used as the construction machine M. A vertical rotation type agitator (hereinafter referred to as agitator 1) is used as the agitator 1 for mixing the ground, which is rotatably attached to the tip of the backhoe M via a rotating shaft 11 and has a pair of agitator units 14 that rotate vertically via a rotating shaft 141 at the tip. All of the multiple nozzles 2 are arranged around the agitator 1, above and below the rotating shafts 141 of the pair of agitator units 14, with the slurry spray direction facing approximately vertically and approximately horizontally to the construction ground. In this case, the multiple nozzles 2 are configured as multiple units, with at least two nozzles 2 as one unit, and one high-pressure pump 3H or low-pressure pump 3L is connected to each unit.

Here, the backhoe M is a commonly known device, consisting of a crawler-type running machine M1 at the bottom and a rotating part M2 at the top, which has a cab and various drive parts, and the boom a and arm b are provided on the rotating part M2. In this case, the boom a is supported rotatably on the rotating part M2 via a rotating shaft (not shown), and a boom cylinder a2 is connected between the rotating part M2 and the middle part of the boom a, so that the boom a can rotate around the rotating shaft between the rotating part M2 and the boom a by the expansion and contraction of the boom cylinder a2. The arm b is supported rotatably on the tip of the boom a via a rotating shaft b1, and an arm cylinder b2 is connected between the middle part of the boom a and the base end of the arm b, so that the arm b can rotate around the rotating shaft b1 between the boom a and the arm b by the expansion and contraction of the arm cylinder b2. The tip of this arm b is the tip of the construction machine mentioned above, in this case, the tip of the backhoe M. A vertical rotation type agitator blade device 1 is rotatably supported at the tip of the arm b via a rotating shaft 11, and an agitator blade device cylinder 12 is connected between the middle part of the arm b and the base end of the agitator blade device 1, so that the agitator blade device 1 can rotate around the rotating shaft 11 between the arm b and the agitator blade device 1 by the expansion and contraction of the agitator blade device cylinder 12, and can be driven vertically up and down relative to the construction ground. The rotating shaft 11 of the agitator blade device 1 is inserted between the tip of the arm b and the agitator blade device 11 so that it is parallel to the construction ground when the agitator blade device 1 is excavating the construction ground.

The vertical rotation type agitator blade device 1 is generally used in the WILL method, and is shown enlarged in Figures 2 and 3. As shown in Figures 2 and 3, the vertical rotation type agitator blade device 1 is configured with a vertically long upper support arm 101, a vertically long lower support arm 102, and a pair of left and right agitator blade units 14.

A hydraulic motor 13 is installed on the upper part of the upper support arm 101, and a drive sprocket (not shown) is attached to the drive shaft of the hydraulic motor 13. An intermediate shaft (not shown) is inserted into the connection between the upper support arm 101 and the lower support arm 102, and an intermediate sprocket (not shown) is attached to the intermediate shaft. A rotating shaft 141, which is formed by connecting a left rotating shaft 141L and a right rotating shaft 141R for a pair of left and right agitator blade units 14 so that they can rotate together, is inserted into the lower part of the lower support arm 102, and a driven sprocket (not shown) is attached to this rotating shaft 141. In this way, an endless chain (not shown) is wound between the driving sprocket of the drive shaft of the hydraulic motor 13 and the intermediate sprocket of the intermediate shaft, and an endless chain (not shown) is wound between the intermediate sprocket of the intermediate shaft and the driven sprocket of the rotating shaft 141.

Each of the pair of left and right agitator blade units 14 has two agitator blades 15a, 15b arranged symmetrically around the left rotating shaft 141L and the right rotating shaft 141R, with the axis of the left rotating shaft 141L and the axis of the right rotating shaft 141R as the center of symmetry.

In the left agitator blade unit 14, multiple agitator claws 152 are arranged diagonally from the outside to the inside on the outer peripheral surface of one agitator blade 15a, and multiple agitator claws 152 are arranged diagonally from the inside to the outside on the outer peripheral surface of the other agitator blade 15b. In this case, a circular mounting portion 142L is provided on the left rotating shaft 141L, and the agitator blade support plate 143L is attached to this mounting portion 142L with both ends protruding from the outer periphery of the mounting portion 142L. Each of the two agitator blades 15a and 15b consists of a blade-shaped base 151 with an arc-shaped cross section and multiple agitator claws 152 protruding at equal intervals from the outer surface of the base 151. One agitator blade 15a is attached diagonally from the outside to the inside to one end of the agitator blade support plate 143L, and multiple agitator claws 152 are arranged diagonally from the outside to the inside on the base 151. The other agitator blade 15b is attached at an angle from the inside to the outside to the other end of the agitator blade support plate 143L, and multiple agitator claws 152 are arranged on the base 151 at an angle from the inside to the outside.

In the right-side agitator blade unit 14, multiple agitator claws 152 are arranged diagonally from the outside to the inside on the outer peripheral surface of one agitator blade 15a, and multiple agitator claws 152 are arranged diagonally from the inside to the outside on the outer peripheral surface of the other agitator blade 15b. In this case, a circular mounting portion 142R is provided on the right rotating shaft 141R, and the agitator blade support plate 143R is attached to this mounting portion 142R with both ends protruding from the outer periphery of the mounting portion 142R. Each of the two agitator blades 15a and 15b consists of a blade-shaped base 151 with an arc-shaped cross section and multiple agitator claws 152 protruding at equal intervals from the outer surface of the base 151. One of the agitator blades 15a is attached diagonally from the outside to the inside to one end of the agitator blade support plate 143R, and multiple agitator claws 152 are arranged diagonally from the outside to the inside on the base 151. The other agitator blade 15b is attached at an angle from the inside to the outside to the other end of the agitator blade support plate 143R, and multiple agitator claws 152 are arranged on the base 151 at an angle from the inside to the outside.

In this way, the pair of agitator blade units 14 are configured in a vertical rotation format, with a pair of agitator blades 15a with multiple agitator claws 152 arranged diagonally from the outside to the inside, and a pair of agitator blades 15b with multiple claws 152 arranged diagonally from the inside to the outside, each of which is attached vertically rotatably to a rotating shaft 141 arranged horizontally at the tip of the lower support arm 102. Thus, when the drive shaft of the hydraulic motor 13 is rotated by the rotation drive of the hydraulic motor 13, this rotation is transmitted to the intermediate shaft via the endless chain between the drive sprocket and the intermediate sprocket, causing the intermediate shaft to rotate, and the rotation of this intermediate shaft is transmitted to the rotating shaft 141 via the endless chain between the intermediate sprocket and the driven sprocket, causing the pair of left and right agitator blade units 14 to rotate vertically up and down.

In addition, when using this mixing impeller device 1 in this construction method, a plurality of hose clamps 16 are installed on the front edge of each of the upper support arm 101 and the lower support arm 102 so that the hose can be arranged along the front edge. In this case, the hose clamp 16 is a block-shaped metal fitting with a cross section of an approximately inverted U-shape, but any shape, such as a cylindrical shape, may be used as long as the hose can be inserted and held. In addition, nozzle mounting parts 17A and 17B are installed at the vertical middle and bottom of the front edge of the lower support arm 102. In this case, the nozzle mounting part 17A at the vertical middle has nozzle mounting parts 171 with nozzle insertion ports at the bottom on both the left and right sides, and has a hose connection part 172 in the center that has a hose connection port at the top and communicates with each of the left and right nozzle mounting parts 171. This nozzle mounting part 17A is installed at the vertical middle of the front edge of the lower support arm 102, straddling both the left and right sides of this front edge. Hereinafter, this nozzle mounting part 17A will be referred to as the upper nozzle mounting part 17A. The nozzle mounting part 17B at the bottom is equipped with nozzle attachment parts 173 on both the left and right sides with nozzle insertion openings facing both left and right sides, and a hose connection part 174 in the center with a hose connection opening on the front part that communicates with each of the left and right nozzle mounting parts 173. This nozzle mounting part 17B is installed at the bottom of the front edge of the lower support arm, straddling both the left and right sides of this front edge. Hereinafter, this nozzle mounting part 17B will be referred to as the lower nozzle mounting part 17B.

A plurality of nozzles 2 are attached to such an agitating impeller device 1. In this case, each nozzle 2 is used to have a circular or elliptical cross-sectional outlet with a predetermined diameter determined together with the pressure of the high-pressure pump 3H according to the properties of the construction ground. In this case, a nozzle with a circular cross-sectional outlet is used as one construction example of this construction method. In this case, four nozzles 2 are used as one construction example of this construction method, and two nozzles 2 are used as one unit to form a two-unit configuration. Then, first, two nozzles 2 per unit are attached to the upper part of the rotation shaft 141 of a pair of agitating impeller units 14 at the vertical middle part of the front edge of the lower support arm 102. In this case, two nozzles 2 are attached from the nozzle insertion openings at the lower part to the nozzle mounting parts 171 on both the left and right sides of the upper nozzle mounting part 17A installed at the vertical middle part of the front edge of the lower support arm 102, with the slurry spray direction being approximately vertical, in this case, particularly slightly forward of the rotation shaft 141. Hereinafter, this nozzle 2 is referred to as the upper nozzle 2. Next, one unit of two nozzles 2 is attached to the bottom of the front edge of the lower support arm 102 below the rotating shaft 141. In this case, the two nozzles 2 are attached to the nozzle mounting parts 173 on both the left and right sides of the lower nozzle mounting part 17B installed at the bottom of the front edge of the lower support arm 102 from the side nozzle insertion openings, with the slurry spray direction facing approximately horizontally to the left and right. Hereinafter, this nozzle 2 is referred to as the lower nozzle 2.

Then, one pump 3H, 3L is connected to each of the two nozzles in each of the upper and lower nozzles 2. In this case, as an example of this method, as shown in FIG. 1, one high-pressure pump 3H for the upper nozzle 2 and one low-pressure pump 3L for the lower nozzle 2 are installed at the construction site together with a slurry supply device 4 consisting of a batcher plant, cement silo, etc., and the high-pressure pump 3H (suction side) and the low-pressure pump 3L (suction side) are connected to the slurry supply device 4 by two hoses 31. Then, the two upper and lower nozzles 2 are connected by two hoses 32, with each of the upper nozzles 2 and the high-pressure pump 3H (discharge side) for the upper nozzle 2, and each of the two lower nozzles 2 and the low-pressure pump 3L (discharge side) for the lower nozzle 2. In this case, the hose 32 connected to the high-pressure pump 3H for the upper nozzle 2 is extended from the rear side of the backhoe M toward the mixing blade device 1, and is connected to the hose connection part 172 in the center of the upper nozzle mounting part 17A from the upper hose connection port, and is connected to each nozzle 2 attached to each nozzle mounting part 171 on the left and right of the upper nozzle mounting part 17A. Also, the hose 32 connected to the low-pressure pump 3L for the lower nozzle 2 is extended from the rear side of the backhoe M toward the mixing blade device 1, and is routed along the front edges of the upper support arm 101 and the lower support arm 102 through each hose fastener 16 on the front edge, and is connected to the hose connection part 174 in the center of the lower nozzle mounting part 17B from the hose connection port on the front side, and is connected to each nozzle 2 attached to each nozzle mounting part 173 on the left and right of the lower nozzle mounting part 17B.

Thus, in this construction method, as one construction example, construction is performed with a two-pump, four-nozzle configuration. In particular, in this configuration, the slurry is fed to the nozzles 2 at high pressure by the high-pressure pump 3H so that the spray direction of the slurry from each nozzle 2 arranged above the rotating shaft 141 is directed substantially vertically to the construction ground, in this case, particularly slightly forward of the rotating shaft 141. The slurry is fed to the nozzles 2 at low pressure by the low-pressure pump 3L so that the spray direction of the slurry from each nozzle 2 arranged below the rotating shaft 141 is directed substantially horizontally to the construction ground. In this way, the slurry fed at high pressure by the high-pressure pump 3H to each nozzle 2 arranged above the rotating shaft 141 is sprayed from these nozzles 2 in a substantially vertical direction to the construction ground at high pressure. In addition, the slurry fed at low pressure by the low-pressure pump 3L to each nozzle 2 arranged below the rotating shaft 141 is sprayed from these nozzles 2 in a substantially horizontal direction to the construction ground at low pressure. The slurry is injected from these nozzles 2 in both directions by combining high-pressure spraying and low-pressure spraying. In this way, the multi-directional high-pressure injection method of the slurry into the construction ground by this method increases the amount of slurry injected into the construction ground compared to the conventional method. In addition, the energy of the increased slurry injection pressure is used as a means for loosening the in-situ soil of the construction ground, improving the mixing performance of the mixing blade device 1.
The slurry discharge port of each nozzle 2, the injection pressure and injection speed (injection amount) of the slurry from each nozzle 2, and the injection direction of the slurry from each nozzle 2 can be variously changed by determining appropriate specifications based on the results of field tests conducted in advance.

An example of this construction method is shown in Figures 4, 5 and 6.
Based on the results of field tests conducted in advance, the slurry outlet of each nozzle 2 is made circular with a diameter of 4.5 mm, particularly for the upper injection. The injection pressure of the slurry from each nozzle 2 is increased from the conventional 1 MPa to 10 MPa. The injection rate of the slurry from each nozzle 2 is increased from the conventional 240 L/min to 400 L/min (upper injection rate 160 L/min, lower injection rate 240 L/min). The injection direction of the slurry is approximately perpendicular to the construction ground, and in this case, it is directed toward the center of the mixing blade device 1 and about 3 cm forward of the rotation shaft 141.
First, in this construction example, as shown in FIG. 4, the backhoe M is moved to the construction ground, and the mixing blade device 1 is stopped at a position where it can be set at the excavation and mixing position of the construction ground. Next, as shown in FIG. 5, the arm b is appropriately moved to hold the mixing blade device 1 at the mixing position of the construction ground. Here, the hydraulic motor 13 is driven to rotate the pair of left and right mixing blade units 14, while the arm b is lowered, and the pair of left and right mixing blade units 14 is pushed and inserted into the construction ground. At the same time, the high-pressure pump 3H and the low-pressure pump 3L (see FIG. 4) outside the backhoe M are operated to increase the amount of slurry from the slurry supply device 4 (see FIG. 4) and send it to the four nozzles 2 with a combination of high pressure and low pressure. In this way, the slurry is sprayed from each nozzle 2 above the lower support arm 102 in a substantially vertical direction toward the construction ground, in this case, from the top of the agitator blade device 1 toward the center of the agitator blade device 1 and slightly (about 3 cm) forward of the rotating shaft 141, at high pressure, and the slurry is sprayed from each nozzle 2 below the lower support arm 102 in a substantially horizontal direction to the left and right toward the construction ground at low pressure. The high-pressure and low-pressure spraying of the slurry from these nozzles 2 loosens the construction ground, making it easier to insert the pair of left and right agitator blade units 14 into the construction ground.

In this construction example, as shown in Figure 6, arm b is lowered to insert each mixing blade unit 14 vertically into the construction ground, and each mixing blade unit 14 rotates vertically to excavate the in-situ soil while mixing it with the slurry.

In this case, the construction ground is excavated and stirred by the vertical rotation of each mixing blade unit 14, and the slurry is high-pressure sprayed and low-pressure sprayed into the construction ground from each nozzle 2 by the high-pressure pump 3H and the low-pressure pump 3L, respectively, so that the in-situ soil and slurry are stirred and mixed as follows.
7, each mixing blade unit 14 has a plurality of mixing tines 152 arranged diagonally from the outside to the inside on one mixing blade 15a, so that as one mixing blade 15a rotates, the in-situ soil moves from the outside to the inside while being mixed up and down and back and forth. Also, each mixing blade unit 14 has a plurality of mixing tines 152 arranged diagonally from the inside to the outside on the other mixing blade 15b, so that as the other mixing blade 15b rotates, the in-situ soil moves from the inside to the outside while being mixed up and down and back and forth. In addition, the slurry is sprayed at high pressure from each nozzle 2 above the rotating shaft 141 in a vertical direction, in this case slightly (about 3 cm) forward of the rotating shaft 141 toward the center of the agitator blade device 1, and at low pressure from each nozzle 2 below the rotating shaft 141 in an approximately horizontal direction to the left and right. This causes the slurry spray energy to loosen the construction ground, improving the mixing performance of the construction ground by each agitator blade unit 14, and the construction ground is thoroughly mixed up and down, front and back, and left and right, and is mixed evenly with the increased amount of slurry.

Then, after the in-situ soil and slurry have been mixed and stirred to a specified depth in the construction ground, arm b is raised to pull each mixing blade unit 14 above the construction ground. This excavation and mixing process is repeated to improve the construction ground.

In this construction example, by carrying out construction with a two-pump, four-nozzle configuration, the amount of slurry sprayed per unit time can be significantly increased from the conventional 240 L/min to 400 L/min. The diameter of each upper nozzle 2 is set to 4.5 mm, the spray energy (spray pressure) from the high-pressure pump 3H and each upper nozzle 2 among the two pumps and four nozzles is increased from the conventional 1 MPa to 10 MPa, and the slurry spray direction of each upper nozzle 2 is directed 3 cm forward of the rotation shaft 141 in the center direction of the mixing blade device 1, thereby significantly improving the mixing efficiency of the construction ground compared to the conventional method. In this way, in this construction method, by carrying out construction using a multiple-pump, multiple-nozzle configuration, the amount of slurry injected per unit time is increased to approximately 1.5 to 2.0 times the conventional injection amount, and by changing the diameter of each nozzle 2 and increasing the injection energy (injection pressure) from the multiple-pump, multiple-nozzle configuration to 10 MPa or more, the mixing efficiency (early homogeneity) of the slurry and the construction ground can be improved, and good quality of the ground improvement body, i.e., early homogeneity, can be ensured with construction in a short period of time.
The results of the field test of this method are shown in Figure 8. The test results confirmed that this method can ensure the same quality as the conventional method, even when the construction speed is increased by 1.67 times compared to the conventional method.

As explained above, in this method, when the construction ground is stirred by the stirring blade device 1, the slurry is fed at high pressure by the high-pressure pump 3H to multiple nozzles 2 around the stirring blade device 1, and is sprayed at high pressure from each nozzle 2 in multiple directions into the construction ground. In this way, the amount of slurry injected into the construction ground is increased, and the in-situ soil of the construction ground is loosened by the slurry injection pressure. Therefore, in the commonly used mechanical stirring type ground improvement method, the amount of slurry injected per unit time can be increased and the mixing efficiency of the slurry and the construction ground can be improved. This increase in the amount of slurry injected and the improvement in mixing efficiency make it possible to ensure good quality (early homogeneity) of the ground improvement body in a short construction time.

In addition, in this method, as shown in one construction example, four nozzles 2 are configured into two units, with two nozzles 2 per unit, and a high-pressure pump 3H and a low-pressure pump 3L are connected to each unit, so that the normally used high-pressure pump 3H and low-pressure pump 3L can be used as is, thereby keeping costs low.

Furthermore, in this construction example, a vertical rotation type agitator blade device 1 is used for the agitator blade device for mixing the ground, which is attached to the tip of the backhoe M via a rotating shaft 11 and has a pair of agitator blade units 14 that rotate vertically via a rotating shaft 141 at the tip. All four nozzles 2 are arranged around each agitator blade unit 14, above and below the rotating shaft 14 of each agitator blade unit 14, with the slurry spray direction facing approximately vertically and approximately horizontally to the construction ground. The slurry fed at high pressure to each upper nozzle 2 by the high-pressure pump 3H is sprayed from each upper nozzle 2 in a substantially vertical direction to the construction ground at high pressure, and the slurry fed at low pressure to each lower nozzle 2 by the low-pressure pump 3L is sprayed from each lower nozzle 2 in a substantially horizontal direction to the construction ground at low pressure. This allows the construction ground to be thoroughly agitated up and down, front and back, and left and right, and evenly mixed with the increased amount of slurry.

In this embodiment, as one example of construction, four nozzles 2 are configured into two units, with two nozzles 2 per unit, and one high-pressure pump 3H and one low-pressure pump 3L are connected to each unit, but five or more nozzles may be configured into multiple units, with at least two nozzles per unit, and one high-pressure pump may be connected to each unit in combination with an appropriate one-unit low-pressure pump. This can also achieve the same or greater effects as the above embodiment.

In addition, in this construction method, a vertically rotating type agitator 1 is used as the agitator blade device for mixing the ground, and has a pair of agitator blade units 14 that are attached to the tip of the backhoe M via a rotating shaft 11 and rotate vertically via a rotating shaft 141 at the tip. However, this construction method can also be applied in the same way when other types of agitator blades are used for this type of ground mixing, and the same effects can be achieved. In one example of this construction method, all of the four nozzles 2 are arranged around each mixing blade unit 14 above and below the rotating shaft 141 of each mixing unit 14, and the slurry is supplied to each nozzle 2 at high pressure by the high-pressure pump 3H with the slurry spray direction of each nozzle 2 arranged above the rotating shaft 141 facing approximately vertically to the construction ground, and the slurry is supplied to each nozzle 2 at low pressure by the low-pressure pump 3L with the slurry spray direction of each nozzle 2 arranged below the rotating shaft 141 facing approximately horizontally to the construction ground, and the slurry supplied at high pressure by the high-pressure pump 3H to each nozzle 2 arranged above the rotating shaft 141 is sprayed from each nozzle 2 at high pressure in a direction approximately vertical to the construction ground, and The slurry is supplied to the tank 2 at low pressure by the low-pressure pump 3L from each nozzle 2 in a substantially horizontal direction to the construction ground, but all of the five or more nozzles may be arranged at any position around each agitator unit, or some of the five or more nozzles may be arranged around each agitator unit, above and below the rotation axis of each agitator unit, and the remaining nozzles may be arranged at any position around the agitator, with the slurry spray direction facing multiple directions including substantially vertical and horizontal to the construction ground, and the slurry is supplied to each nozzle at high pressure (including low pressure) by the high-pressure pump (including low-pressure pump) from each nozzle in multiple directions including substantially vertical and horizontal to the construction ground. In this way, the same or better effects as those of the above embodiment can be achieved.

M Construction machinery (backhoe)
M1 crawler type traveling machine M2 swivel section a boom a2 boom cylinder b arm b1 rotating shaft b2 arm cylinder 1 agitator 101 upper support arm 102 lower support arm 11 rotating shaft 12 agitator cylinder 13 hydraulic motor 14 agitator unit 141 rotating shaft 141L left rotating shaft 141R right rotating shaft 142L, 142R mounting section 143L, 143R agitator support plate 15a, 15b agitator 151 base 152 agitator claw 16 hose fastener 17A, 17B nozzle mounting section 171, 173 nozzle mounting section 172, 174 hose connection section 2 nozzle 3H high pressure pump 3L low pressure pump 31, 32 hose 4 slurry supply device

Claims (2)

In a mechanical mixing method, a mixing blade device for mixing the ground and a nozzle for spraying slurry are attached to the tip of a construction machine, and the slurry and in-situ soil are mixed while being injected into the construction ground.
The agitator blade device is a vertical rotation type agitator blade device having a pair of agitator blade units rotatably attached to the tip of a construction machine via a rotating shaft, the pair of agitator blade units having two agitator blades symmetrically arranged around the axis of the rotating shaft, with the axis of the rotating shaft being the center of symmetry, and one of the two agitator blades is arranged diagonally around the rotating shaft with one end facing forward facing outward and the other end facing inward, as viewed from the front, and the other is arranged diagonally with one end facing backward facing inward and the other end facing outward, and a plurality of agitator claws are arranged on the outer peripheral surface of each agitator blade ,
The nozzles are provided above and below the rotating shaft of the pair of mixing blade units , the upper nozzle is arranged so that the direction of spraying the slurry from the nozzle is approximately vertical to the construction ground, a high-pressure pump for feeding the slurry is connected to the upper nozzle , the lower nozzle is arranged so that the direction of spraying the slurry from the nozzle is approximately horizontal to the construction ground, and a low-pressure pump for feeding the slurry is connected to the lower nozzle ,
When the construction ground is stirred by the stirring blade device, the pair of stirring blade units stirs and mixes the construction ground in the up-down, back-and-forth and left-right directions, while the high-pressure pump supplies the slurry to the upper nozzle at high pressure and sprays it from the nozzle toward the construction ground at high pressure , and the low-pressure pump supplies the slurry to the lower nozzle at low pressure and sprays it from the nozzle toward the construction ground at low pressure , thereby increasing the amount of slurry injected into the construction ground and injecting the slurry while loosening the in-situ soil of the construction ground with the slurry injection pressure.
A mechanical mixing method characterized by the above. The mechanical mixing method according to claim 1 , wherein the diameter of the upper nozzle's slurry outlet is approximately 4.5 mm, and the injection pressure of the slurry from the upper nozzle is 10 MPa to 15 MPa .

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