JP6752076B2 - Ground improvement method and its equipment - Google Patents

Description

The present invention relates to a ground improvement method and an apparatus thereof, which are suitable for multi-layered ground in which upper and lower layers are different layers, particularly alternating layers of sandy soil layer and cohesive soil layer.

There is known a ground improvement method for strengthening the ground by injecting an improving material such as cement milk into the ground, stirring and mixing to solidify it (for example, Japanese Patent No. 3416774, hereinafter referred to as a reference publication). In this construction method, the soil at the construction site is bored and sampled in advance according to the target improvement strength, an indoor compounding test is conducted, and the on-site construction compounding amount of the improved material is set in consideration of the safety factor. The strength after construction is affected by the soil quality of the ground, the amount of improved material to be injected, the number of blade cuttings indicating the degree of stirring, etc. It is difficult to maintain the temperature, and the injection amount of the improved material is increased to prevent the decrease in strength. In addition, in cohesive soil, soil lumps that remain without being mixed with the injected improved material are likely to form, the reliability of the degree of agitation is low, and the strength varies widely. Especially in highly acidic cohesive soil mixed with humus soil and humus soil, the strength tends not to be as expected. On the other hand, in the ground of sandy soil layer, the penetration resistance is large, but the strength after construction is easy to be obtained and the degree of agitation is highly reliable, so that the amount of improved material to be injected can be small.

In any case, in this kind of target ground, it is rare that there is only cohesive ground or only sandy ground, and it is an alternating layered ground in which sandy soil layers and cohesive soil layers are alternately overlapped. Is common. When performing ground improvement in such alternating layers, it is complicated to change the amount of improvement material to be injected between the cohesive soil layer and the sandy soil layer, so the amount of improvement material to be injected should be adjusted to the cohesive soil layer. I had a lot. For this reason, in the sandy soil layer in the alternating ground, the amount of improved material is excessive than the required amount, and since the excess improved material is injected, the amount of soil discharged as industrial waste also increases, and the construction cost rises. Not only does it do, but the disposal costs are not ridiculous.

In relation to the above alternate layered ground, Patent Documents 1 and 2 disclose a ground improvement method in which the target ground is applied to the alternate layered ground of the sandy soil layer and the cohesive soil layer. As a feature of the construction method of Patent Document 1, in the sandy soil layer, the cement milk in the agitator is discharged from the first discharge port to the original ground through the first supply flow path in the rod by the first pump and mixed. In the cohesive soil layer, the cement milk in the agitator is put into the aggregate mixer via the switching valve, and the mortar mixed with the aggregate such as sand is passed through the second supply flow path in the rod by the second pump. Discharge from the discharge port to the original ground and mix. Further, as a feature of the construction method of Patent Document 2, in the sandy soil layer, sand pile is formed by pouring sand into the casing pipe from the upper hopper and vibrating the casing pipe with the lower vibrator at the same time. In the cohesive soil layer, the casing pipe is rotated to create a cement-based pile composed of a stabilizer and in-situ soil from a nozzle provided on the rotary blade.

JP-A-2002-339342 Japanese Unexamined Patent Publication No. 9-328745

By the way, in the recent ground improvement method, even when the target ground is alternating ground, it is necessary not only to satisfy the required ground improvement effect but also to reduce the construction cost as much as possible. In this regard, as in Patent Documents 1 and 2, even if the material cost may increase just by changing the improvement materials used in the sandy soil layer and the cohesive soil layer that make up the alternating layer ground, the entire construction The cost cannot be reduced.

As a result of investigating a construction method that enables such reduction of construction costs, the present inventors have found that, in the case of a sandy soil layer and a cohesive soil layer as alternating ground, the sand constituting the sandy soil layer It is said that the material can be used as an improvement material for the cohesive soil layer, or the clay material that constitutes the cohesive soil layer can be used as an improvement material for the sandy soil layer, and as a result, the amount of improvement material such as cement milk can be reduced. It came to the confirmation of.

An object of the present invention is a ground improvement method and an apparatus thereof capable of performing good ground improvement while reducing costs in a multi-layered ground in which upper and lower layers are different layers, particularly in alternating layers of sandy soil layer and cohesive soil layer. Is to provide. Other purposes will be clarified in the following description.

In order to achieve the above object, the present invention is specified with reference to FIG. 6, and the upper layer A and the lower layer B are penetrated and pulled out under the ground in the ground improvement method applied to the multi-layered ground 9 of different layers. A forward / reverse rotatable outer cylinder 3 and a forward / reverse rotatable inner shaft 4 having a spiral screw 41 around the outer cylinder and arranged through the inside of the outer cylinder are provided. In the process of penetrating into the multi-layered ground, one of the original ground portions of the upper layer portion A and the lower layer portion B is taken into the outer cylinder from the lower end of the outer cylinder 3 by the normal rotation of the inner shaft 4, and then a further penetration process is performed. Alternatively, one of the original ground portions taken into the outer cylinder by reversing the inner shaft in the pulling process is discharged to the other original ground of the upper layer portion A and the lower layer portion B as an improvement material , and the one original is discharged . It is characterized in that the ground portion and the other original ground are mixed.

It is more preferable that the above invention is embodied as in claims 2 to 7.
(A) In claim 1, the multi-layer ground has a clay-based lower layer and a sand-based upper layer, and the sand portion of the upper layer is discharged and mixed with the clay of the lower layer (claim). Item 2), the lower layer portion is sand-based, the upper layer portion is clay-based, and the clay portion of the upper layer portion is discharged to the sand of the lower layer portion and mixed (claim 3). These also include ground configurations in which intermediate layers other than sand-based and clay-based are interposed between the upper and lower layers.

(A), in any one of claims 1 to 3, the vertical moving means for allowing the inner shaft to move up and down relative to the outer cylinder is provided, and the lower end opening of the outer cylinder is provided by the vertical moving means. The gap between the inner shaft and the lower end side of the inner shaft is adjusted according to the ground properties (claim 4).

(C), in any one of claims 1 to 4, the inner excavation means for both stirring blades mounted on the lower end of the inner shaft and the outer excavation means for both stirring blades mounted around the lower end of the outer cylinder. The inner excavation means and the outer excavation means excavate and stir the original ground in the process of penetrating the outer cylinder and the inner shaft into the original ground (claim 5).

(D), in any one of claims 1 to 5, an inner improving material discharging means provided on the lower end side of the inner shaft and discharging the improving material transferred along the inner shaft to the original ground, and the above-mentioned. It has an outer improving material discharging means provided in the outer excavating means arranged around the lower end of the outer cylinder and discharging the improving material transferred along the outer cylinder to the original ground, and has an outer improving material discharging means of the inner shaft and the outer cylinder. The structure is such that the improved material is discharged to the original ground by the improved material discharging means in the process of penetrating into the multi-layered ground and / and the process of drawing out (claim 6). Here, examples of the improving material include cement milk obtained by adding water to cement, mortar material obtained by adding sand, soil, etc. to the cement milk, and materials similar thereto. The discharge method is, for example, a method in which the improved material is transferred to the supply pipe by a pump and discharged from a nozzle connected to the tip of the supply pipe, the improved material and the compressed air are transferred to the dedicated pump and the dedicated supply pipe, and the improved material is transferred to the compressed air. This is a method (reference publication) in which the air is discharged from the nozzle along with the air.

(E) In the ground improvement equipment used in the ground improvement method applied to the multi-layered ground where the upper and lower layers are different layers, a forward / reverse rotatable outer cylinder that penetrates and is pulled out from the ground, and a spiral screw. Has a forward / reverse rotatable inner shaft that is arranged through the inside of the outer cylinder, and in the process of penetrating the inner shaft and the outer cylinder into the multilayer ground, the upper layer portion or the lower layer portion. The original ground moving means for taking the original ground portion into the outer cylinder from the lower end of the outer cylinder by rotating the inner shaft in the forward and reverse directions and discharging and mixing it into the original ground again, and the inner shaft relative to the outer cylinder. A vertical movement means that enables vertical movement, an inner excavation means that also serves as a stirring blade attached to the lower end of the inner shaft, and an outer excavation means that also serves as a stirring blade that is mounted around the lower end of the outer cylinder. An inner improving material discharging means provided on the lower end side of the inner shaft and transferred along the inner shaft is discharged into the original ground, and an inner improving material discharging means provided on the outer excavation means and transferred along the outer cylinder. The configuration is provided with an outer improving material discharging means for discharging the coming improving material to the original ground (claim 7).

In the invention of claim 1, a multi-layered ground having different layers in the upper layer and the lower layer is targeted, and one of the original ground portions of the upper and lower layers is discharged to the other original ground as the other improvement material and mixed. It is possible to almost average the soil properties between the layers while obtaining the improvement effect, and the amount and total amount of improvement materials such as cement milk and mortar used as needed are reduced while maintaining the improvement effect. As a result, both construction costs and waste treatment costs can be reduced.

In the invention of claim 2, when the lower layer portion is clay-based and the upper layer portion is sand-based, the sand portion of the upper layer portion is discharged to the clay of the lower layer portion and mixed, for example, to lower the water content ratio or improve the drainage property. It can be added to improve the clay properties.

In the invention of claim 3, when the lower layer portion is sand-based and the upper layer portion is clay-based, the clay portion of the upper layer portion is discharged to the sand of the lower layer portion and mixed, so that, for example, the strength of the sand-based lower layer portion ( Liquefaction strength) is increased to make it effective as a liquefaction countermeasure.

In the invention of claim 4, the gap between the lower end opening of the outer cylinder and the lower end side of the inner shaft by the vertical moving means, that is, the intake port for taking the original ground portion into the outer cylinder, and / or the inner cylinder. By adjusting the size of the discharge port that discharges the captured original ground portion, it is possible to optimize the intake speed, total intake amount, discharge speed, total discharge amount, and the like.

In the invention of claim 5, since the original ground is excavated and agitated in the process of intruding the outer cylinder and the inner shaft into the original ground by the inner excavation means and the outer excavation means that also serve as a stirring blade, the penetration ability in the hard ground is insufficient. It is also easy to create a large-diameter improved body that is less likely to occur or has a diameter of, for example, 2 meters or more.

In the invention of claim 6, the inner shaft is provided on the lower end side and has an inner improving material discharging means for discharging the improved material transferred into the inner shaft to the original ground, and the outer cylinder is arranged around the lower end. Since it has an outer improving material discharging means provided in the outer excavating means and discharging the improved material transferred along the outer cylinder to the original ground, the improved material is shown from FIG. 6 according to the ground properties. As illustrated in 8, it is possible to discharge in various modes, and it is possible to add variety to the construction method.

In the invention of claim 7, it is used as an optimum device for the ground improvement method of claims 1 to 6 as a ground improvement device used in a ground improvement method in which an upper layer portion and a lower layer portion are applied to a multi-layered ground of different layers. it can.

It is a schematic diagram which shows the whole of the ground improvement apparatus most suitable for the construction method of this invention. (A) is a schematic view showing a drive mechanism unit for driving the outer cylinder and the inner shaft of FIG. 1, and (b) is a schematic view showing a state in which the inner shaft is lowered with respect to the outer cylinder by a vertical moving means. (A) is a cross-sectional view showing the outer cylinder and the lower side of the inner shaft of FIG. 2, and (b) is a state in which the inner shaft is lowered with respect to the outer cylinder by a vertical moving means, and the original ground portion is removed from the outer cylinder in the ground penetration process. It is a schematic diagram which shows the state which takes in inside. FIG. 3A is a schematic diagram showing a state in which the original ground portion taken into the outer cylinder is discharged in FIG. 3B, and FIG. 3B is a schematic diagram for explaining the stirring region. A modified example of the inner excavation means connected to the lower end of the inner shaft is shown, (a) is a front view and (b) is a bottom view. (A) to (f) are explanatory views which show the construction procedure example of the construction method of this invention. (A) to (f) are explanatory views which show the other construction procedure example of this invention construction method. (A) to (f) are explanatory views showing still another construction procedure example of the construction method of this invention.

Hereinafter, a mode to which the present invention is applied will be described with reference to the drawings. In this description, after explaining the device structure of the ground improvement device used in the construction method of the present invention and a modification of the inner excavation means, the ground improvement construction methods 1 to 3 using the same will be described in detail. The details of the drawings are omitted or simplified due to drawing restrictions.

(Device Structure) In FIGS. 1 to 4, the ground improvement device 1 includes a base machine 10, a reader 14 mounted upright on the tip support portion 11 of the base machine 10, and a reader 14 as an overall structure. It includes a stay 1 2 that supports it in an upright position, a guide rail 15 mounted on one side surface of the leader 14, and an attachment 2 that is moved up and down along the guide rail 15.

Further, as a main part structure, it has an outer cylinder 3 that can rotate in the forward and reverse directions and an inner shaft 4 that has a spiral screw 41 around and is arranged through the outer cylinder 3 and can rotate in the forward and reverse directions. In the process of penetrating the 3 and the inner shaft 4 into the multi-layered ground 9, the original ground portion of the upper layer or the lower layer is taken into the outer cylinder from the lower end of the outer cylinder 3 by the forward and reverse rotation of the inner shaft 4 and discharged to the original ground again. The original ground moving means 5 for mixing and mixing, the hydraulic cylinder 6 which is a vertical moving means for moving the inner shaft 4 up and down relative to the outer cylinder 3, and the improved material transferred along the inner shaft 4 are inside. Inner improving material discharging means (7, 40, 42) for discharging into the original ground from the lower end side of the shaft and improving material transferred along the outer cylinder 3 from the lower end side of the outer cylinder or the outer excavation means 35 side described later. It is equipped with outer improving material discharging means (8, 30, 32) for discharging into the original ground. These details will be clarified below.

First, the base machine 10 is supported so that the upper main body 16 can turn with respect to the lower traveling body 17 having a caterpillar via a turning portion. Although details are omitted, the upper main body 16 is provided with a cockpit, a winch for wires (not shown), and the like, and a stage 18 is connected to the rear portion. Various construction operation units and control units are arranged in the cockpit. The stage 18 is equipped with an engine and the like.

Further, the attachment 2 is a moving base 22 that constitutes an elevating means that moves up and down with the upper mount base 20, the lower mount base 21, and the mount bases 20, 21 being fitted to the guide rail 15 as an integral body. And a guide sleeve 25 fixedly supported in a skewered state with respect to each of the mount bases 20 and 21. Reference numeral 19 is a hanging member such as a rope that supplements the raising and lowering of the moving base 22 . Although the details are omitted, the suspension member 19 is pulled out from a winch drum (not shown) mounted on the base machine 10 and connected to a support frame 26 described later through a pulley group incorporated in a cap tree at the top of the leader 14. To.

In the original ground moving means 5, the inner shaft 4 is on the outer circumference, and a spiral screw 41 is integrated from the lower end to the front of the guide sleeve 25. The upper side of the inner shaft 4 is inserted through the guide sleeve 25 described above. The outer cylinder 3 has an inner diameter for loosely fitting the inner shaft 4 with the screw 41, and the supply pipe 30 extends from a portion corresponding to the swivel 8 to the vicinity of the outer excavation means 35 on the outer circumference.

Further, as shown in FIGS. 3 and 4, an outer excavation means 35 is provided around the lower end of the outer cylinder 3, and a stirring blade 39 is provided slightly above the outer excavation means 35. The outer excavation means 35 is attached to each of the tubular fixed cylinder 36 mounted on the outer cylinder 3, the pair of blades 37 projecting from the fixed cylinder 36 for both excavation and stirring, and each blade 37. It has a plurality of drilling bits 38 and nozzles 32. The nozzle 32 is connected to the lower end of the corresponding supply pipe 30 so that an improved material such as cement milk can be discharged to the original ground. The stirring blade 39 has substantially the same length and number as the blade 37, and is projected from the tubular fixed cylinder 38 mounted on the outer cylinder 3.

On the other hand, the inner excavation means 45 is connected to the lower end of the inner shaft 4. The inner excavation means 45 is attached to a tubular fixed cylinder 46 mounted on the inner shaft 4, a pair of blades 47 projecting from the fixed cylinder 46 for both excavation and stirring, and each blade 47. It has a plurality of excavation bits 48 and a closing member 43 that closes the lower opening of the inner shaft 4 and holds the nozzle 42. The nozzle 42 is connected to the lower end of the corresponding supply pipe 40 so that an improved material such as cement milk can be discharged to the original ground.

The upper mount base 20 includes a pair of drive motors 50 that allow the inner shaft 4 that penetrates the guide sleeve 25 to rotate in the forward and reverse directions, and a supply pipe 40 in which an improved material transferred from the outside is piped in the inner shaft 4. A swivel 7 is provided so as to be movable in the. Of these, each drive motor 50 is connected to the upper portion of the inner shaft 4 inserted into the guide sleeve 25 via a gear mechanism (not shown) to rotate the inner shaft 4 in the forward and reverse directions. The swivel 7 is provided inside the support frame 26 held by the mount base 20 and transfers an improved material such as cement milk sent from the outside to the supply pipe 40.

The lower mount base 21 has a pair of drive motors 51 that allow the outer cylinder 3 to rotate in the forward and reverse directions, and an improved material that is transferred from the outside to the supply pipe 30 that is piped to the outer circumference of the outer cylinder 3. A swivel 8 is provided. Of these, each drive motor 51 is connected to the upper part of the outer cylinder 3 via a gear mechanism (not shown) to rotate the outer cylinder 3 in the forward and reverse directions. The swivel 8 transfers an improved material such as cement milk provided inside the support frame 27 held under the mount base 21 and sent from the outside to the supply pipe 30 of the outer cylinder.

The outer improving material discharging means is provided in the outer cylinder swivel 8 and the outer excavation means 35 that enable the improving material such as cement milk to be transferred to the supply pipe 30 piped on the outer circumference of the outer cylinder 3. It is composed of a nozzle 32 or the like that receives the improved material transferred via the 30 and discharges it to the original ground. The inner improving material discharging means is provided in the inner shaft swivel 7 and the inner excavation means 45 that enable the improving material such as cement milk to be transferred to the supply pipe 40 piped in the inner shaft 4, and is provided via the supply pipe 40. It is composed of a nozzle 42 or the like that receives the improved material to be transferred and discharges it to the original ground.

In the hydraulic cylinder 6, the cylinder body 6a, which is the main body, is connected and supported by the mounting portion 23 provided on the lower surface side of the upper mount base 20, and the piston 6b appearing and disappearing in the cylinder body 6a is provided on the lower mount base 21. It is connected and supported by the portion 24 . In this example, each (a) of FIGS. 2 and 3 shows a state in which the piston 6b protrudes from the inside of the cylinder 6a, and each (b) shows a state in which the piston 6b is submerged in the inside of the cylinder 6a. In the protruding state of the piston 6b of each (a), the gap between the lower end opening of the outer cylinder 3 and the lower end side of the inner shaft 4 is minimized. In the submerged state of the piston 6b of each (b), the gap, that is, the intake port for taking in the original ground portion into the outer cylinder 3 and the discharge port for discharging the original ground portion taken into the outer cylinder 3 are maximized. ..

(Modification Example) FIG. 5 shows a modification of the inner excavation means 45 described above. In this description, substantially the same parts as those in the above form are designated by the same reference numerals, and the changes are clarified. The inner excavation means 45A includes a main body 44 having substantially the same diameter as the inner shaft 4, a screw 44a provided around the main body 44 and continuous with the screw 41, and a lower end of the inner shaft 4 projecting from the upper surface of the main body 44. It has a connecting shaft 44b that is engaged on the side. The main body 44 and the connecting shaft 44b have a tubular shape on the inside in which the supply pipe 40 is arranged. A nozzle 42 mounted on the lower end side of the cylinder and connected to the lower end of the supply pipe 40 is mounted on the tubular shape. A plurality of excavation bits 48 are attached to the lower ends of the main body 44 and the screw 44a. The screw 44a has both an excavating action and an action of moving the original ground. The excavation bit 48 is configured to excavate the original ground directly below the main body 44.

(Ground improvement method) Next, three examples will be described as a construction procedure in the case of ground improvement by the ground improvement method of the present invention using the above ground improvement device. In FIGS. 6 to 8, the smaller rotation direction indicated by the ellipse in the figure indicates the rotation direction of the inner shaft, and the larger rotation direction indicates the rotation direction of the outer cylinder. In the construction work, the soil at the construction site is bored and collected in advance according to the target improvement strength, and the boundary depth between the upper and lower layers and the length of each layer are grasped. In addition, an indoor compounding experiment will be conducted on the collected soil, and the amount of the improved material to be applied on site will be set. These are the same as before.

(Ground improvement method 1) In the multi-layered ground shown in FIG. 6, the upper layer A is assumed to be sand-based ground and the lower layer B is assumed to be clay-based ground. The same (a) shows a state in which the ground improvement device is moved and the original ground moving means 5, that is, the lower ends of the outer cylinder 3 and the inner shaft 4 are positioned at the construction site. In this state, the tip end portion of the inner shaft 4, that is, the inner excavation means 45 protrudes more than the lower end portion of the outer cylinder 3, and the sand portion of the original ground can be taken into the outer cylinder 3.

The same (b) shows a state in which the original ground moving means 5, that is, the outer cylinder 3 and the inner shaft 4 have started to descend. In this descent, as shown by the arrows in the drawing, the improved material is discharged from the nozzle 42 on the tip side of the inner shaft 3 and the nozzle 32 on the side of the outer excavation means 35, while the inner shaft 3 and the outer cylinder 4 are lowered in a forward rotation. .. In the descending process, while excavating the inside of the original ground with the inner excavation means 45 and the outer excavation means 35, the improved materials discharged from the nozzles 42 and 32 are mixed and agitated, and as shown in the same (c), a circle is formed in the original ground. Create a columnar improved reserve body. At the same time, the sand portion of the original ground is sequentially taken into the cylinder of the outer cylinder 4 by the forward rotation of the inner shaft 3.

The same (c) shows a state in which the lower end of the outer cylinder 3 or the outer excavation means 35 constituting the original ground moving means 5 is lowered to the vicinity of the boundary between the upper layer portion A and the lower layer portion B. The determination of this boundary is determined by whether or not the lower end of the outer cylinder 3 or the outer excavation means 35 has reached the boundary depth previously known by the boring survey. Of course, since the rotational resistance of sand-based ground is higher than that of clay-based ground, it can be determined by sudden fluctuations in rotational torque, and it is preferable to use this determination as well.

In the same (d), after the lower end of the outer cylinder 3 or the outer excavation means 35 crosses the boundary and reaches the clay-based ground, the inner shaft 3 is rotated in the reverse direction to remove the sand portion taken into the outer cylinder 4. It shows a state in which the sand portion is sequentially discharged from the lower end opening of the cylinder to the original ground, and this sand portion, the clay-based ground of the lower layer portion B, and the improved material discharged from the nozzles 42 and 32 are mixed. ing. The same (e) shows a state in which the lower end of the outer cylinder 3 or the outer excavation means 35 constituting the original ground moving means 5 has reached a target depth. In the original ground (clay-based ground) of the lower layer portion B, clay-based soil particles are loosened apart by mixing the sand portion discharged from the outer cylinder 3, and in that state, the clay-based soil particles are discharged from the nozzles 42 and 32. Since the materials are also mixed, it is possible to create a columnar improved body having uniform strength without forming clay lumps.

In the same (d) and (e), for example, when humus or humus is present in the clay-based ground of the lower layer B, especially in the clay-based soil, the alkalin reaction of the cement is suppressed by the acidity, causing poor solidification. Although it is easy to develop the strength, the acidity is alleviated by the mixing of the sand portion of the upper layer A as in this construction method, so that the strength can be satisfied relatively easily.

Next, after reaching the construction target depth, the outer cylinder 3 is reversed, and the original ground moving means 5, that is, the outer cylinder 3 and the inner shaft 4 are raised to shift to the pulling operation. The same (f) shows a state in which the lower end of the outer shaft 3 or the outer excavation means 35 reaches the surface GL after the shift to the pulling operation. The columnar improved body constructed as described above becomes almost homogeneous by appropriately mixing clay, sand and the improving material regardless of the properties of each soil in the alternating layered ground. Further, in this columnar improved body, since the sand portion of the upper layer A is used as the improving material for the clay-based ground of the lower layer B, the amount of the improving material such as cement milk discharged from the nozzles 42 and 33 is reduced and the construction cost is reduced. Can be reduced.

(Ground improvement method 2) Similar to FIG. 6, the multi-layered ground in FIG. 7 assumes that the upper layer A1 is sand-based ground and the lower layer B1 is clay-based ground. In this description, only the configuration modified as compared with FIG. 6 will be clarified. In this ground improvement method, FIGS. 7 (a) to 7 (c) are different from FIGS. 6 (a) to 6 (c) in that the improved material is not discharged from the nozzles 42 and 32. That is, in this construction method, the sand portion of the original ground is sequentially taken into the cylinder of the outer cylinder 4 by the forward rotation of the inner shaft 3, but the improved material is not discharged from the nozzles 42 and 32 until the boundary is reached.

7 (d) to 7 (f) show the inner shaft 3 after the lower end of the outer cylinder 3 or the outer excavation means 35 crosses the boundary and reaches the clay-based ground as compared with FIGS. 6 (d) to 6 (f). By rotating in the reverse direction, the sand portion taken into the outer cylinder 4 is sequentially discharged from the lower end opening of the outer cylinder to the original ground, and from the discharged sand portion, the clay-based ground of the lower layer portion B1, and the nozzles 42 and 32, respectively. It is the same in that it mixes with the discharged improved material. However, unlike the configuration of FIG. 6, the sand portion taken into the outer cylinder 4 does not contain an improving material. Therefore, in the columnar improved body formed in the lower layer portion B1, if the total amount of the improved material discharged from the nozzles 42 and 32 is the same in FIGS. 6 and 7, the content of the improved material is FIG. FIG. 7 is lower than the above.

Further, in this construction method, as compared with FIG. 6F, when the ground moving means 5, that is, the outer cylinder 3 and the inner shaft 4 penetrate and then rise above the boundary in the pulling process, the improving material is layered above the nozzle 42. It is discharged to the sand-based ground of part A1. This discharge amount is determined according to, for example, the amount of movement of the sand portion that has moved from the sand-based ground of the upper layer portion A1 to the lower layer portion B2.

(Ground improvement method 3) In the multi-layered ground shown in FIG. 8, the upper layer A2 is assumed to be clay-based ground and the lower layer B2 is assumed to be sand-based ground. In this explanation as well, only the configuration changed as compared with FIG. 7 will be clarified. In this ground improvement method, FIGS. 8 (a) to 8 (c) are substantially the same as those in FIGS. 7 (a) to 7 (c). That is, in this construction method, the improved material is not discharged from the nozzles 42 and 32, and the clay portion of the original ground is sequentially taken into the cylinder of the outer cylinder 4 by the forward rotation of the inner shaft 3.

8 (d) to 8 (f) show that after the lower end of the outer cylinder 3 or the outer excavation means 35 crosses the boundary and reaches the sand-based ground, the inner shaft 3 is rotated in the reverse direction and taken into the outer cylinder 4. The clay portion is sequentially discharged from the lower end opening of the outer cylinder to the original ground, and the discharged clay portion and the sand-based ground of the lower layer portion B1 are mixed. However, in this method, the improved material is not discharged from the nozzles 42 and 32 as compared with FIG. Therefore, in the columnar improved body formed in the lower layer portion B2, the sand-based ground and the clay portion moved from the upper layer portion A2 are mixed and agitated. Further, also in this construction method, as compared with FIG. 7 (f), when the ground moving means 5, that is, the outer cylinder 3 and the inner shaft 4 penetrate and then rise above the boundary in the pulling process, the improved material is layered above the nozzle 42. It is discharged to the sand-based ground of part A2. This discharge amount is also determined, for example, according to the amount of movement of the clay portion that has moved from the clay-based ground of the upper layer portion A2 to the lower layer portion B2.

The above embodiment does not limit the present invention in any way. The present invention only needs to include the components specified in each claim, and the details can be variously changed and developed as necessary. For example, in terms of equipment, the construction scale and depth include an elevating means that moves the attachment up and down, a vertical moving means that moves the inner shaft up and down relative to the outer cylinder, and a configuration that discharges the improved material from the corresponding nozzle. It can be changed as appropriate according to the ground properties, the type of improvement material, and the like.

In addition, legally, the target multi-layer ground has a surface layer that is not subject to improvement, an intermediate layer lies between the upper and lower layers, and alternating ground is stacked alternately. It also includes complex multi-layered ground. In addition, when the depth of each layer ground is different, the intake and discharge amount into the outer cylinder is adjusted by changing the forward / reverse rotation speed and penetration speed of the inner shaft, and each layer is made as uniform as possible. Of course, it should be possible to mix them.

1 ... Ground improvement device 2 ... Attachment 5 ... Original ground moving means (3 is the outer cylinder, 4 is the inner shaft, 41 is the screw)
6 ... Hydraulic cylinder (vertical moving means)
7 ... Swivel for inner shaft (inner improving material discharge means)
8 ... Swivel for outer cylinder (outer improving material discharge means)
9 ... Multi-layer ground (A is sand-based ground, B is clay-based ground)
9A ... Multi-layer ground (A1 is sand-based ground, B1 is clay-based ground)
9B ... Multi-layer ground (A2 is clay-based ground, B2 is sand-based ground)
45 ... Inner excavation means (48 is excavation bit)
45A ・ ・ ・ Inner excavation means (48 is excavation bit)
10 ... Base machine 14 ... Leader 15 ... Guide rail 30 ... Outer cylinder supply pipe (outer improvement material discharge means)
32 ... Nozzle (outer improving material discharge means)
35 ... Outer excavation means (38 is excavation bit)
39 ... Stirring blade 40 ... Inner shaft supply pipe (inner improved material discharge means)
42 ... Nozzle (inner improvement material discharge means)
45 ... Inner excavation means (48 is excavation bit)
45A ・ ・ ・ Inner excavation means (48 is excavation bit)

Claims (7)

In the ground improvement method applied to multi-layered ground where the upper and lower layers are different layers,
It is equipped with a forward / reverse rotatable outer cylinder that penetrates and is pulled out under the ground, and a forward / reverse rotatable inner shaft that has a spiral screw around it and is arranged through the inside of the outer cylinder.
In the process of penetrating the inner shaft and the outer cylinder into the multi-layered ground, one of the original ground portions of the upper layer portion and the lower layer portion is taken into the outer cylinder from the lower end of the outer cylinder by the normal rotation of the inner shaft. The one original ground portion taken into the outer cylinder by the reversal of the inner shaft in the further penetration process or the pulling process is discharged to the other original ground of the upper layer portion and the lower layer portion as an improvement material , and the one A ground improvement method characterized by mixing the original ground portion of the above and the other original ground . The ground improvement according to claim 1, wherein the lower layer portion is clay-based and the upper layer portion is sand-based, and the sand portion of the upper layer portion is discharged to the clay of the lower layer portion and mixed. Construction method. The ground improvement according to claim 1, wherein the lower layer portion is sand-based and the upper layer portion is clay-based, and the clay portion of the upper layer portion is discharged to the sand of the lower layer portion and mixed. Construction method. It has a vertical movement means that allows the inner shaft to move up and down independently with respect to the outer cylinder, and the vertical movement means creates a gap between the lower end opening of the outer cylinder and the lower end side of the inner shaft. The ground improvement method according to any one of claims 1 to 3, wherein the ground improvement method is adjusted according to the above. The inner excavation means also used as a stirring blade mounted on the lower end of the inner shaft and the outer excavating means also used as a stirring blade mounted around the lower end of the outer cylinder are provided, and the inner excavating means and the outer excavating means are said to have the same. The ground improvement method according to any one of claims 1 to 4, wherein the original ground is excavated and agitated in the process of penetrating the outer cylinder and the inner shaft into the original ground. It is provided in the inner improving material discharging means and the outer excavation means which discharge the improving material which is provided on the lower end side of the inner shaft and is transferred through the supply pipe which is piped along the inner shaft to the original ground. It has an outer improving material discharging means for discharging the improving material transferred through the supply pipe piped along the outer cylinder to the original ground, and the process of penetrating the inner shaft and the outer cylinder into the multilayer ground. Alternatively, The ground improvement method according to claim 5, wherein the improved material is discharged to the original ground by the improved material discharging means in the drawing process. In the ground improvement equipment used in the ground improvement method applied to the multi-layered ground where the upper and lower layers are different layers.
It has a forward / reverse rotatable outer cylinder that penetrates and is pulled out from the ground, and a forward / reverse rotatable inner shaft that has a spiral screw around it and is arranged through the inside of the outer cylinder. In the process of penetrating the outer cylinder into the multi-layered ground, the original ground portion of the upper layer portion or the lower layer portion is taken into the outer cylinder from the lower end of the outer cylinder by the forward and reverse rotation of the inner shaft, and is discharged to the original ground again. Mixing ground transportation means and
A vertical movement means that enables the inner shaft to move up and down relative to the outer cylinder,
An inner excavation means for both stirring blades mounted on the lower end of the inner shaft, and an outer excavation means for both stirring blades mounted around the lower end of the outer cylinder.
An inner improving material discharging means provided on the lower end side of the inner shaft and being transferred along the inner shaft is discharged into the original ground, and an inner improving material discharging means provided on the outer excavating means and transferred along the outer cylinder. A ground improvement device characterized by being provided with an outer improvement material discharging means for discharging the coming improvement material to the original ground.

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