JP2018021379A - Method and device for ground improvement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to perform good ground improvement in a multilayer system ground, especially a laminated ground of a sandy soil layer and a cohesive soil layer while reducing costs.SOLUTION: In a ground improvement method applied to a multilayer system ground 9 that has an upper layer part A and a lower layer part B that are different with each other, the ground improvement machine comprises: an external cylinder 3 that is free to rotate in normal/reverse directions and is penetrated/pulled out into/from the ground; and an inner shaft 4 that can be free to rotate in normal/reverse directions, and has a spiral screw 40 on the periphery and is penetratingly arranged inside the external cylinder 3. In the step of penetrating the inner shaft 4 and the external cylinder 3 into the multilayer system ground 9, an original ground part of the upper layer part A or the lower layer part B is taken into the external cylinder 3 from the bottom edge thereof by the normal rotation of the inner shaft 4. After this, in the further penetrating or pulling out step, by the reverse rotation of the inner shaft 4, the original ground part taken into the external cylinder is discharged to the lower layer part B or the upper layer part A to be mixed for use as an improvement material.SELECTED DRAWING: Figure 6

Description

  TECHNICAL FIELD The present invention relates to a ground improvement method and apparatus suitable for a multi-layered ground having different upper and lower layers, in particular, a sandy soil layer and a viscous soil layer.

  There is known a ground improvement method for strengthening the ground by injecting an improvement material such as cement milk into the ground, stirring and mixing to solidify (for example, Japanese Patent No. 3416774, hereinafter referred to as a reference). In this method, the soil at the construction site has been bored in advance according to the target improvement strength, an indoor blending test is conducted, and the site construction blending amount of the improved material is set in consideration of the safety factor. The strength after construction is affected by the soil quality, the amount of improved material to be injected, the number of blade cuttings that indicate the degree of stirring, etc., but especially in the soil of viscous soil (especially humus and humus) Is difficult to maintain, and the amount of improvement material injected is increased to prevent a decrease in strength. In addition, in the soil of clay soil, a lump that remains without being mixed with the injected improvement material is easily formed, the reliability of the degree of stirring is low, and the variation in strength increases. In particular, the strength does not tend to be as expected in viscous soil with high acidity mixed with humus and humus. On the other hand, in the ground of the sandy soil layer, although the penetration resistance is large, the strength after construction is easily obtained and the reliability of the degree of stirring is high, so that the amount of the improved material to be injected is small.

  In any case, in this type of target ground, it is rare that it is only a viscous ground or only a sandy ground, and it is an alternate-layered ground in which sandy soil layers and viscous soil layers are alternately overlapped. It is common. When performing ground improvement on such an alternate layer ground, changing the amount of the improved material to be injected between the viscous soil layer and the sandy soil layer becomes cumbersome, so the amount of the improved material to be injected should match the viscous soil layer. A lot. For this reason, in the sandy soil layer in the alternating layer ground, the amount of the improved material is excessive than the required amount, and since the excessive improved material is injected, the amount of soil that is industrial waste also increases and the construction cost increases. Not only does it cost waste disposal.

  In relation to the above alternate ground, Patent Documents 1 and 2 disclose a ground improvement method in which the target ground is applied to an alternate ground of a sandy soil layer and a viscous soil layer. As a construction method feature of Patent Document 1, in the sandy soil layer, 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 viscous soil layer, the mortar in which cement milk in the agitator is mixed with the aggregate such as sand through the switching valve is mixed with the second pump through the second supply flow path in the rod by the second pump. Discharge from the outlet to the ground and mix. Further, as a feature of the construction method of Patent Document 2, in the sandy soil layer, sand is poured into the casing pipe from the upper hopper and at the same time the casing pipe is vibrated by the lower vibrator. In the cohesive soil layer, the casing pipe is rotated to create a cement pile made of a stabilizer and in-situ soil from a nozzle provided on the rotor blade.

JP 2002-339342 A JP-A-9-328745

  By the way, in the recent ground improvement method, even when the target ground is an alternating layer ground, not only the required ground improvement effect but also the construction cost must be suppressed as much as possible. In this regard, as in Patent Documents 1 and 2, the entire construction work is possible even if the material cost may be increased simply by changing the improvement material used in the sandy soil layer and the viscous soil layer constituting the alternate layered ground. Cost cannot be reduced.

  As a result of studying a construction method capable of reducing such construction costs, the present inventors have found that sand that constitutes a sandy soil layer is an example of a sandy soil layer and a viscous soil layer as an alternating layer ground. If the material can be used as an improvement material for the viscous soil layer, or the clay material constituting the viscous 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 confirmation.

  An object of the present invention is to provide a ground improvement method and apparatus capable of improving the ground while reducing costs in a multi-layered ground having different upper and lower layers, in particular, a sandy soil layer and a viscous soil layer. Is to provide. Other purposes will be clarified in the description below.

  In order to achieve the above object, when the present invention is specified with reference to FIG. 6, the upper layer portion A and the lower layer portion B are penetrated and extracted under the ground in the ground improvement method applied to the multi-layered ground 9. An outer cylinder 3 capable of rotating in the forward and reverse directions, and an inner shaft 4 having a spiral screw 41 around the inner cylinder 4 that can be rotated in the forward and reverse directions are disposed inside the outer cylinder, and the inner shaft and the outer cylinder are In the process of penetrating into the multi-layered ground, after the original ground portion of the upper layer part A or the lower layer part B is taken into the outer cylinder from the lower end of the outer cylinder 3 by forward rotation of the inner shaft 4, further penetration process or extraction The raw ground portion taken into the outer cylinder by the reversal of the inner shaft in the process is discharged and mixed into the lower layer B or the upper layer A for improvement material.

The present invention as described above is more preferably embodied as in claims 2 to 7.
(A) In claim 1, the multi-layered ground is configured such that 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 and mixed with the clay of the lower layer portion. Item 2), 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 into and mixed with the sand of the lower layer portion (claim 3). These include a ground configuration in which an intermediate layer other than sand or clay is interposed between the upper layer and the lower layer.

(A) In any one of claims 1 to 3, the apparatus has vertical movement means that allows the inner shaft to move up and down relatively with respect to the outer cylinder, and the vertical movement means opens the lower end of the outer cylinder. It is the structure which adjusts the clearance gap between the lower end side of the said inner shaft according to ground property (Claim 4).

(C) In any one of claims 1 to 4, an inner excavation means combined with a stirring blade attached to a lower end of the inner shaft, and an outer excavation means combined with an agitation blade attached around the lower end of the outer cylinder And the inner excavating means and the outer excavating means excavate the original ground and agitate in the process of penetration of the outer cylinder and the inner shaft with respect to the original ground (Claim 5).

(D) In any one of Claims 1-5, the improvement material discharge means inside which discharges the improvement material which is provided in the lower end side of the inner shaft and is transferred along the inner shaft to the original ground, and the An outer improvement material discharging means provided on an outer excavation means disposed around the lower end of the outer cylinder and discharging the improved material transferred along the outer cylinder to the original ground; the inner shaft and the outer cylinder; According to the sixth aspect of the present invention, the improvement material is discharged to the original ground by the improvement material discharge means in the process of penetration into the multilayer ground or / and the drawing process. Here, examples of the improving material include cement milk obtained by adding water to cement, mortar material obtained by adding sand or soil to the cement milk, and similar materials. The discharge method is, for example, a method in which the improved material is transferred to a supply pipe by a pump and discharged from a nozzle connected to the tip of the supply pipe, the improved material and compressed air are transferred to a dedicated pump and a dedicated supply pipe, and the improved material is compressed air. This is a method (reference gazette) that discharges from a nozzle accompanied with the nozzle.

(E) In a ground improvement device used in a ground improvement method applied to a multi-layered ground in which the upper layer and the lower layer are different layers, an outer cylinder that can be rotated in the forward and reverse directions and penetrated into the ground, and a spiral screw In the process of penetrating the inner shaft and the outer cylinder into the multi-layered ground, and the upper layer or the lower layer. The original ground portion is taken into the outer cylinder from the lower end of the outer cylinder by forward and reverse rotation of the inner shaft, and is discharged and mixed into the original ground again, and the inner shaft is relative to the outer cylinder. A vertical movement means that enables vertical movement, an inner excavation means that also serves as an agitating blade attached to the lower end of the inner shaft, and an outer excavation means that also serves as an agitating blade attached around the lower end of the outer cylinder, Improvement provided on the lower end side of the inner shaft and transferred along the inner shaft And an outer improvement material discharge means for discharging the improvement material which is provided in the outer excavation means and is transported along the outer cylinder to the original ground. (Claim 7).

  In the first aspect of the invention, the upper layer portion and the lower layer portion are targeted for the multi-layered ground, and one raw ground portion of the upper and lower layer portions is discharged to the other raw ground as the other improving material and mixed. In addition, while obtaining an improvement effect, the soil properties can be almost averaged between each other layer, and the amount of use and total amount of the improvement material such as cement milk and mortar used as needed is reduced while maintaining the improvement effect. As a result, both construction costs and waste disposal costs can be reduced.

  In the invention of claim 2, when the lower layer part is clay-based and the upper layer part is sand-based, by discharging and mixing the sand part of the upper layer part into the clay of the lower layer part, for example, the water content ratio is lowered or the drainage is improved. It is possible to improve clay properties by imparting.

  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 and mixed with the sand of the lower layer portion, for example, the strength of the sand-based lower layer portion ( Increase liquefaction strength) and make it effective as a countermeasure against liquefaction.

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

  In the invention of claim 5, since the original ground is excavated and agitated in the intrusion process of the outer cylinder and the inner shaft with respect to the original ground by the inner excavating means and the outer excavating means which are also used as the stirring blades, the lack of penetration capability in the hard ground is caused. It is also easy to create an improved body having a large diameter, which is less likely to occur or has a diameter of 2 meters or more, for example.

  In the invention of claim 6, the inner shaft is provided on the lower end side and has the inner improved material discharge 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 the outer improvement material discharging means that discharges the improvement material that is provided in the outer excavation means and is transferred along the outer cylinder to the original ground is provided, the improvement material is shown in FIG. As illustrated in FIG. 8, it becomes possible to discharge in various modes, and diversity can be imparted to the construction method.

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

It is a schematic diagram which shows the whole ground improvement apparatus optimal for this invention construction method. (A) is a schematic diagram which shows the drive mechanism part which drives the outer cylinder and inner shaft of FIG. 1, (b) is a schematic diagram which shows the state which the inner shaft lowered | hung with the up-and-down moving means with respect to the outer cylinder. 2A is a cross-sectional view showing the lower side of the outer cylinder and the inner shaft of FIG. 2, and FIG. 2B is a diagram showing the original ground portion in the outer cylinder while the inner shaft is lowered by the vertical movement means with respect to the outer cylinder. It is a schematic diagram which shows the state taken in. (A) is a schematic diagram which shows the state which has discharged | emitted the raw ground part taken in in the outer cylinder in FIG.3 (b), (b) is a schematic diagram for demonstrating the stirring area | region. The modification of the inner excavation means connected with the lower end of the said inner shaft is shown, (a) is a front view, (b) is a bottom view. (A)-(f) is explanatory drawing which shows the construction procedure example of this invention construction method. (A)-(f) is explanatory drawing which shows the other construction procedure example of this invention construction method. (A)-(f) is explanatory drawing which shows the further another construction procedure example of this invention construction method.

  Hereinafter, embodiments 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 method of the present invention and a modified example of the inner excavation means, the ground improvement methods 1 to 3 using it will be described in detail. In the drawings, details are omitted or simplified due to restrictions in drawing.

1 to 4, the ground improvement device 1 includes, as an overall structure, a base machine 10, a reader 14 placed upright on a tip support portion 11 of the base machine 10, and a reader 14. A stay 12 and a catch hawk 13 that are supported in an upright state, a guide rail 15 that is mounted on one side of the leader 14, and an attachment 2 that is moved up and down along the guide rail 15 are provided.

  Further, as the main part structure, the outer cylinder 3 having a forward and reverse rotation and the inner shaft 4 having a spiral screw 41 around the outer cylinder 3 and being disposed through the outer cylinder 3 are provided. In the process of penetrating 3 and the inner shaft 4 into the multi-layered ground 9, the upper or lower layer of the original ground portion is taken into the outer tube from the lower end of the outer tube 3 by the forward and reverse rotation of the inner shaft 4, and discharged again to the original ground The raw ground moving means 5 for mixing, the hydraulic cylinder 6 which is a vertical moving means for moving the inner shaft 4 up and down relatively with respect to the outer cylinder 3, and the improved material transferred along the inner shaft 4 The inner improvement material discharge means (7, 40, 42) for discharging into the raw ground from the lower end side of the shaft, and the improved 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. Outer improvement material discharge 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 from the upper body 16, a cockpit, a winch for wires (not shown), and the like are provided, and a stage 18 is connected to the rear part. Various construction operation units and control units are arranged in the cockpit. A motor or the like is mounted on the stage 18.

  The attachment 2 includes an upper mount base 20, a lower mount base 21, and a moving base body 23 that constitutes an elevating means that moves up and down in a state where the mount bases 20 and 21 are fitted to the guide rail 15. And a guide sleeve 25 that is fixedly supported in a skewed state with respect to the mount bases 20 and 21. Reference numeral 19 denotes a suspension member such as a rope that supplements the movement of the moving base 23. Although the details of the suspension member 19 are omitted, the suspension member 19 is pulled out from a winch drum (not shown) mounted on the base machine 10 and is connected to a support frame 26 described later through a pulley group incorporated in a headboard on the top of the reader 14. The

  In the original ground moving means 5, the inner shaft 4 is on the outer periphery, 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 extends from a portion corresponding to the swivel 8 on the outer periphery to the vicinity of the outer excavating means 35.

  Further, an outer excavating means 35 is provided around the lower end of the outer cylinder 3 as shown in FIGS. 3 and 4, and a stirring blade 39 is provided slightly above the outer excavating means 35. The outer excavating means 35 is attached to each of the wings 37, a cylindrical fixed cylinder 36 attached to the outer cylinder 3, a pair of wings 37 projecting from the fixed cylinder 36 and used for both excavation and stirring. A plurality of drill bits 38 and nozzles 32 are provided. The nozzles 32 are connected to the lower ends of the corresponding supply pipes 30 so that an improved material such as cement milk can be discharged to the raw ground. The stirring blade 39 has substantially the same length and the same number as the blades 37, and protrudes from a cylindrical fixed cylinder 38 attached to the outer cylinder 3.

  On the other hand, an inner excavating means 45 is connected to the lower end of the inner shaft 4. The inner excavating means 45 is attached to each of the blades 47, a cylindrical fixed tube 46 attached to the inner shaft 4, a pair of blades 47 that project from the fixed tube 46 and have both excavation action and stirring action. A plurality of excavation bits 48 and a closing member 43 for closing the lower opening of the inner shaft 4 and holding the nozzle 42 are provided. The nozzles 42 are connected to the lower ends of the corresponding supply pipes 40 so that an improved material such as cement milk can be discharged to the raw ground.

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

  In the lower mount base 21, a pair of drive motors 51 that can rotate the outer cylinder 3 forward and backward, and an improvement material transferred from the outside can be transferred to a supply pipe 30 piped on the outer periphery of the outer cylinder 3. A swivel 8 is provided. Among 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 forward and backward. The swivel 8 is provided inside the support frame 27 held on the lower side of the mount base 21 and transfers an improving material such as cement milk sent from the outside to the supply pipe 30 of the outer cylinder.

  The outer improvement material discharge means is provided in the outer cylinder swivel 8 and the outer excavation means 35 that allow the improvement material such as cement milk to be transferred to the supply pipe 30 provided on the outer periphery of the outer cylinder 3. The nozzle 32 etc. which receive the improved material conveyed through 30 and discharge it to a raw ground. The inner improvement material discharge means is provided in the inner shaft swivel 7 and the inner excavation means 45 that allow the improvement material such as cement milk to be transferred to the supply pipe 40 piped in the inner shaft 4. And a nozzle 42 for receiving the improved material to be transported and discharging it to the original ground.

  The hydraulic cylinder 6 has a cylindrical body 6a as a main body connected to and supported by a mounting portion 22 provided on the lower surface side of the upper mount base 20, and a piston 6b protruding and retracting from the cylindrical body 6a is provided on the lower mount base 21. The portion 23 is connected and supported. In this example, each (a) in FIGS. 2 and 3 shows a state in which the piston 6b protrudes from the cylinder 6a, and each (b) shows a state in which the piston 6b is submerged in 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 each of the (b) pistons 6b in the collapsed state, the gap, that is, the intake port for taking 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) FIG. 5 shows a modification of the inner excavation means 45 described above. In this description, parts that are substantially the same as those in the above embodiment are given the same reference numerals, and 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 continuing to the screw 41, and a lower end of the inner shaft 4 protruding from the upper surface of the main body 44. And a connecting shaft 44b engaged on the side. The main body 44 and the connecting shaft 44b have a cylindrical shape on the inner side where the supply pipe 40 is disposed. A nozzle 42 attached to the lower end side of the cylinder and connected to the lower end of the supply pipe 40 is attached to the cylinder. A plurality of excavation bits 48 are attached to the lower ends of the main body 44 and the screw 44a. The screw 44a doubles as an excavating action and an action of moving the original ground. The excavation bit 48 is configured to excavate the original ground just below the main body 44.

(Ground improvement method) Next, three examples will be described as construction procedures when the ground improvement method of the present invention is used to improve the ground using the above ground improvement device. 6 to 8, the smaller rotation direction indicated by an 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 in advance according to the target improvement strength, and the boundary depth of the upper layer and the lower layer, the length of each layer, etc. are grasped. In addition, an indoor blending experiment is performed on the collected soil, and the amount of on-site construction blending of the improved material is set. These are the same as before.

(Soil Improvement Method 1) The multi-layer ground shown in FIG. 6 assumes that the upper layer A is sand-based ground and the lower layer B is clay-based ground. The same (a) has shown the state which moved the said ground improvement apparatus, and positioned the original ground moving means 5, ie, the outer cylinder 3, and the lower end of the inner shaft 4, in the construction location. In this state, the tip end portion of the inner shaft 4, that is, the inner excavation means 45 protrudes larger than the lower end 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 are started to descend. In this lowering, the inner shaft 3 and the outer cylinder 4 are lowered in a normal rotation while discharging the improved material from the tip side nozzle 42 of the inner shaft 3 and the nozzle 32 on the outer excavating means 35 side as indicated by the arrows in the figure. . In the descending process, the improvement material discharged from the nozzles 42 and 32 is mixed and stirred while the inside excavation means 45 and the outside excavation means 35 excavate the inside of the original ground, and as shown in FIG. A column-shaped improved spare body is created. 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.

  FIG. 6C shows a state where the lower end or outer excavation means 35 of the outer cylinder 3 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. This boundary is determined by whether or not the lower end of the outer cylinder 3 or the outer excavation means 35 has reached a boundary depth that has been previously determined by a boring survey. Of course, since the rotational resistance of the sand-based ground is higher than that of the clay-based ground, it can be determined by a sudden change in rotational torque, and therefore it is preferable to use that determination in combination.

  (D) shows that after the lower end of the outer cylinder 3 or the outer excavation means 35 reaches the clay-based ground beyond the boundary, the inner shaft 3 is rotated backward to remove the sand portion taken into the outer cylinder 4. Sequentially discharged from the bottom end of the cylinder to the original ground, and using this as an improved material, this sand part and the clay-based ground of the lower layer B and the improved material discharged from the nozzles 42 and 32 are mixed. ing. (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 the target depth. The base ground (clay-based ground) of the lower layer B is improved in that clay-based soil particles are loosened apart by mixing the sand parts discharged from the outer cylinder 3 and discharged from the nozzles 42 and 32 in that state. Since the materials are also mixed, a cylindrical improvement body with uniform strength can be created without producing a mass of earth.

  In (d) and (e), for example, when humus or humus soil is present in the clay-based soil as the clay-based ground of the lower layer B, the alkali reaction of the cement is suppressed due to its acidity, resulting in poor solidification. Although it is easy to develop the strength, the acidity is relaxed by mixing the sand portion of the upper layer portion 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, the original ground moving means 5, that is, the outer cylinder 3 and the inner shaft 4 are raised, and the operation is shifted to the drawing operation. (F) shows a state in which the lower end of the outer shaft 3 or the outer excavation means 35 has reached the ground surface GL after the transition to the pulling-out operation. The cylindrical improvement body created as described above becomes almost homogeneous by mixing clay, sand, and improvement material appropriately regardless of the properties of each soil of the alternate layered ground. Moreover, since this cylindrical improvement body used the sand part of the upper layer part A as an improvement material of the clay type ground of the lower layer part B, it reduces the usage amount of improvement materials, such as cement milk discharged from the nozzles 42 and 33, and construction cost Can be reduced.

(Soil Improvement Method 2) The multi-layered ground in FIG. 7 assumes that the upper layer portion A1 is sand-based ground and the lower layer portion B1 is clay-based ground, as in FIG. In this description, only the configuration changed from that in FIG. 6 will be clarified. In this ground improvement construction method, FIGS. 7A to 7C are different from FIGS. 6A to 6C in that the improvement 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 normal rotation of the inner shaft 3, but the improvement material is not discharged from the nozzles 42 and 32 until the boundary is reached.

  7 (d) to (f), compared with FIGS. 6 (d) to (f), after the lower end of the outer cylinder 3 or the outer excavation means 35 reaches the clay-based ground beyond the boundary, the inner shaft 3 is moved. By rotating in reverse, 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 and the clay-based ground of the lower layer B1 and the nozzles 42, 32 It is the same in that the improved material to be discharged is mixed. However, the sand portion taken into the outer cylinder 4 does not include an improving material unlike the configuration of FIG. For this reason, if the total amount of the improved material discharged from the nozzles 42 and 32 is the same in FIG. 6 and FIG. FIG. 7 is lower than FIG.

  Further, in this construction method, compared with FIG. 6 (f), after the original ground moving means 5, that is, the outer cylinder 3 and the inner shaft 4 penetrates, the improvement material is higher than the nozzle 42 when it is raised above the boundary in the drawing process. It is discharged onto 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.

(Soil Improvement Method 3) The multilayer ground in FIG. 8 assumes that the upper layer portion A2 is clay-based ground and the lower layer portion B2 is sand-based ground. In this description, only the configuration changed from that in FIG. 7 will be clarified. In this ground improvement construction method, FIGS. 8A to 8C are substantially the same as FIGS. 7A to 7C. That is, in this construction method, the improvement 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 normal rotation of the inner shaft 3.

  FIGS. 8D to 8F show that the lower end of the outer cylinder 3 or the outer excavation means 35 reaches the sand-based ground beyond the boundary, and then the inner shaft 3 is reversely rotated to be taken into the outer cylinder 4. The clay portion thus discharged 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 construction method, the improved material is not discharged from the nozzles 42 and 32 as compared to FIG. For this reason, the cylindrical improvement body created in lower layer part B2 becomes what the sand system ground and the clay part moved from upper layer part A2 mixed and stirred. Further, even in this construction method, the improved material is higher than the nozzle 42 when it is lifted from the boundary in the drawing process after the original ground moving means 5, that is, the outer cylinder 3 and the inner shaft 4 penetrates, as compared with FIG. It is discharged onto the sand-based ground of part A2. This discharge amount is also determined according to, for example, 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.

  Note that the above embodiments do not limit the present invention. The present invention only has 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 lifting and lowering means for moving the attachment up and down, the vertical movement means for moving the inner shaft up and down relatively with respect to the outer cylinder, the configuration for discharging the improved material from the corresponding nozzle, etc. It can be appropriately changed according to the ground properties, the type of the improved material, and the like.

  In terms of construction, the target multi-layer ground has a surface layer that is not subject to improvement, an intermediate layer lies between the upper layer and the lower layer, and alternate layers are stacked alternately. This includes complex multi-layered ground. In addition, when the depth of each layer is different, by changing the forward / reverse rotation speed and penetration speed of the inner shaft, the amount of intake and discharge into the outer cylinder is adjusted so that each layer is as homogeneous as possible. Of course, it is only necessary to allow mixing.

DESCRIPTION OF SYMBOLS 1 .... Ground improvement apparatus 2 .... Attachment 5 .... Original ground moving means (3 is an outer cylinder, 4 is an inner shaft, 41 is a screw)
6 .... Hydraulic cylinder (up and down movement means)
7 ... Swivel for inner shaft (inner improvement material discharge means)
8 ... Swivel for outer cylinder (outside improvement material discharge means)
9 ... Multilayer ground (A is sand ground, B is clay ground)
9A ... Multi-layered ground (A1 is sand-based ground, B1 is clay-based ground)
9B ... Multi-layered ground (A2 is clay-based ground, B2 is sand-based ground)
45... Inside drilling means (48 is a drill bit)
45A ... Inside drilling means (48 is a drill bit)
DESCRIPTION OF SYMBOLS 10 ... Base machine 14 ... Leader 15 ... Guide rail 30 ... Outer cylinder supply pipe (outside improvement material discharge means)
32 .... Nozzle (outside improved material discharge means)
35... Outer drilling means (38 is a drill bit)
39 ... Agitator blade 40 ... Inner shaft supply pipe (inner improvement material discharge means)
42... Nozzle (inner improvement material discharge means)

Claims (7)

In the ground improvement method applied to the multi-layered ground where the upper layer and lower layer are different layers,
An outer cylinder that can be rotated forward and backward that penetrates and pulls out under the ground, and an inner shaft that can be rotated forward and reversely disposed inside the outer cylinder with a helical screw around the periphery,
In the process of penetrating the inner shaft and outer cylinder into the multi-layered ground, after the original ground portion of the upper layer part or the lower layer part is taken into the outer cylinder from the lower end of the outer cylinder by forward rotation of the inner shaft, further A ground improvement method characterized by discharging and mixing an original ground portion taken into the outer cylinder by reversal of the inner shaft in an intrusion process or a drawing process into the lower layer or upper layer for improvement material.   2. The ground improvement according to claim 1, wherein the multilayered ground is a clay-based lower layer part and a sand-based upper layer part, and the sand part of the upper layer part is discharged and mixed with the clay of the lower layer part. Construction method.   2. The ground improvement according to claim 1, wherein the multi-layered ground is sand-based in the lower layer and clay-based in the upper layer, and the clay portion in the upper layer is discharged and mixed with the sand in the lower layer. Construction method.   It has 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 allows a clearance between the lower end opening of the outer cylinder and the lower end side of the inner shaft to be ground The ground improvement construction method according to any one of claims 1 to 3, wherein the ground improvement method according to any one of claims 1 to 3 is adjusted according to the conditions.   An inner digging means also serving as a stirring wing attached to a lower end of the inner shaft, and an outer digging means serving also as a stirring wing attached to the periphery of the lower end of the outer cylinder, wherein the inner digging means and the outer digging means are the The ground improvement method according to any one of claims 1 to 4, wherein the ground is excavated and agitated in an intrusion process of the outer cylinder and the inner shaft with respect to the ground.   Provided in the inner improved material discharge means for discharging the improved material, which is provided on the lower end side of the inner shaft and transferred through a supply pipe routed along the inner shaft, to the original ground, and in the outer excavation means. And having an outer improvement material discharge means for discharging the improved material transferred through a supply pipe routed along the outer cylinder to the original ground, the process of penetrating the inner shaft and the outer cylinder into the multilayered ground, 6. The ground improvement method according to claim 5, wherein the improvement material is discharged onto the original ground by the improvement material discharge means in the drawing process. In the ground improvement device used in the ground improvement method applied to the multi-layered ground where the upper layer and the lower layer are different layers,
An outer cylinder capable of rotating in the forward and reverse directions penetrating into and extracted from the ground, and an inner shaft capable of rotating in the forward and reverse directions having a helical screw around the inside and penetrating inside the outer cylinder; In the process of penetrating the outer cylinder into the multi-layered ground, 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 by the forward and reverse rotation of the inner shaft, and is discharged again to the original ground. Raw ground moving means to be mixed;
Vertical movement means for allowing the inner shaft to move up and down relatively with respect to the outer cylinder;
An inner excavation means combined with a stirring blade attached to the lower end of the inner shaft, and an outer excavation means combined with an agitation blade attached around the lower end of the outer cylinder;
Inner improvement material discharge means provided at the lower end side of the inner shaft and discharged along the inner shaft into the original ground, and provided on the outer excavation means and transferred along the outer cylinder. A ground improvement device, comprising: an outside improvement material discharge means for discharging the coming improvement material to the original ground.

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