JP2017014738A - Drain material installation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drain material installation method, which can eliminate a damage of absorbing sediment or water in a water permeable stratum from a tip of the drain material and reduce attention and effort to set the tip of the drain material at a predetermined depth.SOLUTION: A soft ground to be improved 100 has a water permeable stratum 101 having a gravel layer and a sand layer at its deep part. A drain material installation method comprises following processes: to insert a drain material 10, which is used for foundation improvement by dehydrating based on vacuum consolidation method, into a mandrel; to connect an anchor plate 40 to a drain material lower end 11 through a rope 30; to press-fit the drain material into the ground to be improved 100 by a drain installation device capable of press-fitting the drain material along with the mandrel; and to pull out the mandrel onto the ground and embed the drain material 10 in the ground to be improved 100. The rope 30 is set at a length which positions the lower end 11 of the drain material 10 vertically at a predetermined distance X above the top face of the water permeable stratum 101 and the lower end 11 of the drain material 10 is closed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a drain material placing method used in ground improvement work in which a vacuum consolidation method is applied to soft ground, and more specifically, a drain material is buried in soft ground having a permeable gravel layer or sand layer in a deep part. The present invention relates to a drain material placing method.

  Conventionally, after a roll-shaped drain material is attached to a reel of a drain placing device and passed through a mandrel that is a guide body for embedding, a drain material is cast using a hydraulic device in the ground to be improved together with the mandrel. The installation method is well known. More specifically, the anchor plate is placed at the end of the mandrel, and the drain plate connected to the anchor plate is inserted into the mandrel and driven to a predetermined depth in the soft ground to fix the anchor plate in the ground. Then, the outer mandrel is pulled out and the drain material inside is buried in the soft ground. As described above, Patent Documents 1 and 2 describe techniques related to a drain material placing method in which a roll-shaped drain material is placed on soft ground using a mandrel or an anchor plate.

  Here, in addition to a general embankment method, the drain method includes a vacuum consolidation method in which moisture is removed by evacuation from a soft ground covered with a sheet.

JP 2013-96217 A JP 2000-54358 A

In this vacuum consolidation method, vacuum pressure is applied to the soft ground through the drain material, so in the soft ground having a water permeable layer such as a gravel layer or sand layer in the deep part, the tip of the drain material is in contact with the water permeable layer. There is a first problem that the water in the water-permeable formation is sucked and a large amount of water in the water-permeable formation not related to compaction is sucked to cause a decrease in vacuum pressure.
In order to solve this problem, it is preferable that the depth of the drain material is set in a soft ground having a height of about 1.5 m from the top of the permeable formation.
However, in order to set the depth of the drain material to a predetermined depth in the soft ground above the permeable formation, there is a second problem that considerable consideration and labor are required.
Experiments have revealed that there is a third problem in that if the tip of the drain material is not covered with a filter, clogging is caused by sucking silt or clay of the soft ground from the tip of the drain material.

  The present invention has been made in view of such a problem, and the object of the present invention is to form a water-permeable formation unrelated to compaction in a soft ground having a water-permeable formation such as a gravel layer or a sand layer in the deep part. Eliminates the negative effects of suctioning water and lowering the vacuum pressure. Second, it reduces the consideration and labor required to set the depth of the drain material to a predetermined depth in the soft ground above the permeable layer. In addition, thirdly, a drain material placing method that can secure the design drain length by eliminating the harmful effect of clogging by sucking earth and sand from the tip of the drain material not covered with the filter is provided. There is to do.

  The present invention has been made to achieve such an object, and the invention according to claim 1 is a soft improvement target ground (100) having a water permeable formation (101) such as a gravel layer or a sand formation in a deep part. In addition, a drain material (10) used for improving the ground by dehydrating by applying a vacuum consolidation method is inserted into a mandrel (20) which is a guide for burial, and a lower end (11) of the drain material (10). An anchor plate (40) is connected with a rope (30) interposed therebetween, and the mandrel (20) is press-fitted into the improvement target ground (100) with a drain placing device (50) that can be press-fitted, and then the mandrel (20) is a drain material placement method in which the drain material (10) is buried in the improvement target ground (100) by pulling it up to the ground, and is predetermined from the upper surface of the water permeable formation (101). The effective length of the rope (30) is set so that the lower end portion (11) of the drain material (10) is positioned vertically upward by the distance (X), and the lower end portion of the drain material (10) ( 11) is closed.

  The invention according to claim 2 of the present invention is to improve the ground by applying a vacuum consolidation method to a soft ground (100) to be improved having a permeable ground layer (101) such as a gravel layer or a sand layer in the deep part. The drain material (10) used for the insertion is inserted into the mandrel (20), which is a guide for burying, and the anchor plate (40) is inserted with the rope (30) interposed at the lower end (11) of the drain material (10). Connected and press-fitted into the ground (100) to be improved with a drain placing device (50) that can be press-fitted together with the mandrel (20), and then the mandrel (20) is pulled up to the ground to drain the drain material (10). A drain material placement method for embedding in the improvement target ground (100), wherein the drain material (1) is within a predetermined distance (X) vertically above the upper surface of the water permeable ground layer (101). ) Is adjusted so that it does not reach, and the length from the lower end (11) of the drain material (10) to the anchor plate (40) is kept at the predetermined distance (X). The effective length of the rope (30) is set in the above.

  The invention described in claim 3 of the present invention is to improve the ground by applying a vacuum consolidation method to a soft ground (100) to be improved having a permeable ground layer (101) such as a gravel layer or a sand layer in the deep part. The drain material (10) used for the insertion is inserted into the mandrel (20), which is a guide for burying, and an anchor plate (40) is connected to the lower end (11) of the drain material (10), and the mandrel (20) And press-fit into the ground to be improved (100) by a drain placing device (50) that can be press-fitted together, and then lift the mandrel (20) to the ground to place the drain material (10) in the ground to be improved (100). A drain material placement method for burying in the drain material (10), which is located within a predetermined distance (X) vertically upward from the upper surface of the water permeable formation (101). Characterized by blocking the.

  The invention according to claim 4 of the present invention is the drain material placing method according to any one of claims 1 to 3, wherein the predetermined distance (X) is 0.5 to 2.0 m. It is characterized by.

  The drain material placing method according to claim 5 of the present invention is the drain material placing method according to claim 3 or 4, wherein the drain material (10) positioned within the range of the predetermined distance (X) is long. A closing process is performed so as to prevent the flow in the direction, and suction of earth and sand on the side deeper than the closed part (60) subjected to the closing process is blocked.

  The invention according to claim 6 of the present invention is the drain material placing method according to claim 5, wherein the drain material (10) is placed at predetermined intervals in a plan view. Refer to the placement depth (Y0, Y1) or the increase / decrease amount (E) of the placement depth measured with the previous placement at the timing between the next placement and the next placement. The depth (Yn) is predicted, and the closed portion (64) in the longitudinal direction of the drain material (10) is set close to the drain reel (54) so as to match the predicted driving depth (Yn). Positioning is performed, and the closed portion (64) thus positioned is subjected to the closing process at the timing.

  According to a seventh aspect of the present invention, in the drain material placing method according to the fifth or sixth aspect, the drain material (10) is viewed from the width direction of the closed portion (60) subjected to the closing treatment. It is folded in a Z shape.

  The invention according to claim 8 of the present invention is the drain material placing method according to any one of claims 5 to 7, wherein the clamping device (71) is attached to the drain material (10) as the closing process. It is characterized by being attached.

  The invention according to claim 9 of the present invention is the drain material placing method according to any one of claims 5 to 8, wherein the filler material (72) is added to the drain material (10) as the closing treatment. It is characterized by filling.

  According to a tenth aspect of the present invention, in the drain material placing method according to any one of the fifth to ninth aspects, as the closing process, the drain material (10) is sealed with a sealing bag (73 ).

  According to the present invention, in a soft ground having a water-permeable formation such as a gravel layer or a sand layer in the deep part, firstly eliminating the adverse effect of sucking water of the water-permeable formation unrelated to compaction and causing a decrease in vacuum pressure, Secondly, in addition to reducing the consideration and labor required to set the tip of the drain material to a predetermined depth in the soft ground above the permeable formation, thirdly, the drain material not covered with a filter It is possible to provide a drain material placing method capable of eliminating the harmful effect of clogging by sucking earth and sand from the tip and ensuring the design drain length.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view for explaining an actual drain material placing device mainly from the exterior (a sectional view of only the underground), (A) is an overall view, and (B) is an enlarged sectional view near the placing point. It is a model explanatory drawing for demonstrating the structure and operation | movement of a drain placement apparatus shown in FIG. It is explanatory drawing of the process of the drain material placement method (henceforth "this method") concerning the embodiment of the present invention, (A) At the time of completion of placement, (B) Each of the steps of (C) closing the drain material at a predetermined distance vertically above the upper surface of the water permeable formation, and (D) placing is cut. Indicates. It is explanatory drawing of each method about the closing process of FIG.3 (C), (A) Bag hanging, (B) Filler injection, (C) Folding the middle and fixing a metal fitting, (D) Folding a terminal and rope Each method is described. It is explanatory drawing of the process of the drain material placement method which concerns on the application Example of this invention, (O) Placing to the 0th point, (A) Placing to the 1st point, (B) To the 2nd point , (C) placement at the third point, and (D) placement at the fourth point. It is the perspective view partly cut in order to demonstrate the structure of a vertical drain. It is explanatory drawing of the state which can anchor | hang and drive an anchor plate to the front-end | tip of the drain material penetrated by the mandrel, (A) is a whole sectional side view, (B) is a plane top view. It is a perspective view for demonstrating the shape which locked the anchor plate to the front-end | tip of the drain material of FIG. It is a schematic explanatory drawing of the experimental apparatus (henceforth "this verification apparatus") which verifies about the difference in the drainage function by the seal existence of the drain material lower end part. It is a graph which shows the time-dependent change of the amount of drainage by drain length 1m in this verification device. It is a photograph of a drain material comparing a pair of verification results when a vacuum pressure is applied for a predetermined time according to conditions by this verification device. (A) When the drain material lower end is sealed (sealed), (B) Drain This is a case where the lower end of the material is not sealed and is open.

Embodiments of the present invention will be described below with reference to the drawings.
[Basic example]
FIG. 1 is a side view (a cross-sectional view of the basement only) for explaining an actual drain material placing device mainly from the exterior, (A) is an overall view, and (B) is an enlarged cross-section in the vicinity of the placing point 90. FIG. As shown in FIG. 1A, the drain placing device 50 is a caterpillar device 51 in which a pedestal 52 (FIG. 2) of a heavy machine with a tower 59 standing upright over 30 m is movable at a walking speed of a person. The mandrel 20 is pressed into the ground along the tower 59 that is suspended and stationary vertically. The drain driving device 50 can drive the drain material 10 inserted through the mandrel 20 at a speed of about 0.3 m per second up to a maximum driving depth of about 30 m.

  FIG. 2 is a schematic explanatory diagram for explaining the configuration and operation of the drain placing apparatus shown in FIG. 1. As shown in FIG. 2, in addition to the tower 59 (not shown in FIG. 2) and the mandrel 20, the drain placing device 50 includes a hydraulic device, a control unit 53, a hydraulic resistance detector 21, and a drain reel. 54, a back tension device 55, and a placement length detector 56. Since the drain 10 having a long shape is inconvenient for transportation and handling, the drain 10 is wound around the drain reel 54 so as to be able to be wound and fed out.

  In order to press-fit the mandrel 20 into the ground, the hydraulic device generates a penetration pressure of about 15 t downward with respect to the tower 59 (FIG. 1). The controller 53 can drive the drain 10 to a predetermined driving depth by the penetration pressure of the mandrel 20 based on the detection outputs of the driving length detector 56 and the hydraulic resistance detector 21.

  The long-wound drain material 10 wound around the drain reel 54 is inserted through the mandrel 20 which is a guide body for embedding. Next, the anchor plate 40 is connected to the lower end portion (hereinafter, also referred to as “drain material lower end portion”) 11 of the drain material 10 directly or via the rope 30 (FIG. 4). The drain material 10 connected to the anchor plate 40 is press-fitted into the improvement target ground 100 (FIG. 1, FIG. 3) together with the mandrel 20 by the drain placing device 50. The drain material 10 is continuously sent out while being unwound from the drain reel 54.

  When the anchor plate 40 locked to the tip of the placing unit 1 comes into contact with the water-permeable formation 101 (FIGS. 4 and 5) such as a gravel layer or a sand layer, the press-fit resistance of the mandrel 20 to the formation having different hardness Changes. The change is detected by the hydraulic resistance detector 21 as a change in detection output. The placement depth from the ground surface can be monitored by the placement length detector 56. When the anchor plate 40 comes into contact with the water permeable formation 101, the mandrel 20 stops press-fitting, and only the mandrel 20 is pulled up to the ground, whereby the placing unit 1 is placed.

  The drain placing device 50 can be placed at the second point by driving and moving the caterpillar device 51 after completing the placement at the first point. By repeating these steps, it is possible to sequentially complete the placement to the first to nth points covering the improvement target ground 100 in a plan view (not shown) in a grid pattern.

  FIG. 3 is an explanatory diagram of the steps of a drain material placing method (hereinafter also referred to as “the present method”) according to an embodiment of the present invention. (A) At the end of placement, (B) Drain placed. The material is cut at the ground surface, and the placement device is moved to the next placement point. (C) The draining material is closed at a predetermined distance from the upper surface of the permeable formation, and (D) The placement is performed. Each process of is shown. FIG. 3 shows only the minimum components necessary for the description of the process, and the other components are omitted.

  As shown in FIG. 3A, the long-winding drain material 10 wound around the drain reel 54 is continuously fed out in the order of the placing units 1 to 3. As described above, the mandrel 20 (see FIGS. 1 and 2) stops press-fitting when the anchor plate 40 locked to the tip of the placing unit 1 comes into contact with the water permeable formation 101, and only the mandrel 20 is used. The placement of the placement unit 1 is completed by pulling up to the ground. Since the function, control, and operation of the mandrel 20 are the same as those already described with reference to FIGS. 1 and 2, they are omitted from an appropriate range from FIGS. 3 to 5 and the description along those drawings. Yes.

  As shown in FIG. 3B, the placement at the first point is completed by separating the drain material 10 of the placement unit 1 from the drain material 10 after the subsequent placement unit 2 at the cutting point 8. . Thereafter, the drain placing device 50 moves to the next second point by the caterpillar device 51 and places placement unit 2. In this placing unit 2, as shown in FIG. 3C, the drain material 10 is closed above the predetermined distance X from where the anchor plate 40 is locked at the lower end 11 of the placing unit 2. The place 60 is placed after the closing process is performed on the ground. The predetermined distance X is 0.5 to 2.0 m, preferably 1.5 m.

  When the placement unit 1 shown in FIGS. 3 (A) to 3 (D) is placed at the first point of the ground 100 to be improved, the placement is connected to the drain material 10 of the placement unit 1. Unit 2 is separated from placement unit 1 and is placed at the second point as shown in FIG. Similarly, the placing unit 3 fed out from the drain reel 54 is placed at a third point (not shown). Such a process is repeated, and the placing unit n fed out from the drain reel 54 is sequentially placed at the nth point (not shown).

  As described with reference to FIGS. 1 to 3, in the drain material placing method according to the present invention, the vacuum consolidation method is applied to the soft improvement target ground 100 having the permeable ground layer 101 such as a gravel layer or a sand layer in the deep part. This is a drain material placement method used for ground improvement work to be dewatered and more specifically as follows. First, the drain material 10 used for ground improvement is inserted through a mandrel 20 which is a guide body for embedding. Next, the anchor plate 40 is connected to the drain material lower end portion 11 directly or via the rope 30 (predetermined distance X in FIG. 4D). Further, since the drain reel 54 and the back tension device 55 appropriately apply the back tension to the drain material 10, the anchor plate 40 locked to the tip of the rope 30 tied to the drain material lower end portion 11 is provided with the mandrel. It is attracted to the tip 22 of 20. The drain material 10 connected to the anchor plate 40 is press-fitted into the improvement target ground 100 together with the mandrel 20 by the drain placing device 50.

  Thereafter, the drain material 10 connected to the anchor plate 40 is buried in the improvement target ground 100 by pulling up only the mandrel 20 to the ground. At that time, the placement depth Y is adjusted so that the drain material 10 does not reach within a predetermined distance X vertically above the upper surface of the water permeable formation 101, and the length from the drain material lower end 11 to the anchor plate 40 is adjusted. The effective length of the rope 30 is set so as to keep the distance X at a predetermined distance X.

Moreover, when the drain material 10 reaches | attains within the predetermined distance X, the suction | inhalation of the earth and sand of the drain material 10 located in the range of the predetermined distance X in the perpendicular upper direction from the upper surface of the water-permeable formation 101 is interrupted | blocked. There are two specific methods for placing the drain material to block the suction of earth and sand.
As a first method (depth management placement method), in the improvement target ground 100, the depth of the permeable formation 101 is investigated in advance, and the placement depth is increased or decreased while referring to the investigated depth. There is a drain material placing method in which the material lower end portion 11 is kept at a height (depth) 1.5 m above the permeable formation.

  On the other hand, as a second method (bottoming management placement method) mainly disclosed in the present invention, a 1.5 m long rope is interposed between the anchor plate 40 and the drain material lower end portion 11. There is also a method in which the drain material lower end 11 is kept at a height (depth) 1.5 m above the water permeable formation 101 by connecting the drain material to the water permeable formation 101 (FIG. 4 ( D)). Compared to the fact that the above-described first method requires a thorough investigation on the depth of the water-permeable formation in the ground 100 to be improved, the second method only requires the placement of the hard water-permeable formation 101 and the drain material. The point that the lower end part 11 can be driven to the depth prescribed | regulated by design is excellent. That is, the second method has an advantage that the distance from the top of the water-permeable base layer 101 to the drain material lower end portion 11 can be easily and accurately separated by 1.5 m. There is also a third method (see FIGS. 4A to 4C) as an embodiment that takes advantage of the advantages of the second method.

  FIG. 4 is an explanatory diagram of each method for the closing process of FIG. 3 (C), (A) bag hanging, (B) filler injection, (C) folding back halfway, and (D) terminal. Fold the rope and show each method. 4A to 4C show the above-described third method, and FIG. 4D shows the above-described second method. In FIG. 4 (A), the airtight bag 73 is put over the section from the drain material lower end part 11 to the closing point 60 positioned above the predetermined distance X. At the closing point 60, the upper part of the sealing bag 73 is sealed so as to close the opening. In FIG. 4B, the fluid flow in the longitudinal direction of the drain material 10 is blocked by injecting the filler 72 into the closed portion 60 above the drain material lower end portion 11 by a predetermined distance X.

  As shown in FIG. 4C, at the closing point 60, the middle is folded and fixed. That is, the closed portion 60 above the drain material lower end portion 11 by a predetermined distance X is folded in a Z shape when the drain material 10 is viewed from the width direction (hereinafter also referred to as “Z-folded portion”). The Z-folded portion is fixed by a holding tool 71, for example, a dedicated metal fitting. In FIG. 4D, the end (lower end portion 11) of the drain material 10 is folded back and fixed with the staple 13, the rope is tied to the folding point 12, and the anchor plate 40 is below the folding point 12 by a predetermined distance X. The length of the rope 30 is set so as to be positioned. As described above, as one of the closing means of the closing point 60 shown in FIG. 3C, as shown in FIG. 4D, from the turning point 12 of the drain material 10 (approximate to the folded lower end portion 11). The effective length of the rope 30 was set so as to keep the length to the anchor plate 40 at a predetermined distance X. As described above, the predetermined distance X is set to 0.5 to 2.0 m, and preferably set to 1.5 m.

  As described above, according to the present invention, in the soft ground having the permeable formation layer 101 such as a gravel layer or a sand layer in the deep part, first, the water of the permeable formation layer 101 unrelated to consolidation is sucked to cause a decrease in vacuum pressure. In addition to eliminating the negative effects, secondly, in addition to reducing the consideration and labor required to set the drain material lower end portion 11 to a predetermined depth in the soft ground above the permeable ground layer 101, and thirdly, a filter A drain material placing method that can eliminate the harmful effect of sucking earth and sand from the lower end portion 11 of the drain material that is not covered with clogging and causing clogging to ensure the design drain length can be provided.

[Application Examples]
Hereinafter, with reference to FIG. 5, the drain material placing method according to the application example of the present invention, in particular, vertically upward from the upper surface of the permeable formation 101 without using the rope 30 as shown in FIG. A drain material placing method that blocks the suction of the earth and sand of the drain material 10 located within the range of the predetermined distance X will be described. Here, the case where the bottom part of the improvement ground 100 is inclined is assumed. Even in such a case, if the rope 30 used in the basic embodiment is used, it conforms to the changing placement depths Y0 to Yn (n is the same as the number of placement units and the number of placement points). As described above, the closing point 64 in the longitudinal direction of the drain material 10 can be appropriately set. However, each time a large number of drain members 10 are driven, it is still more efficient if the labor of connecting the rope 30 between the drain member lower end portion 11 and the anchor plate 40 can be omitted. Furthermore, it has also been desired to efficiently perform the closing process described with reference to FIGS. 3 and 4 in a safer place. The application examples show that these points have been improved.

  Here, a practical problem of the closing process will be briefly described. As shown in FIG. 3C, if the closing process for the closing point 60 is performed immediately before the placement, it is performed directly under the tower 59 in the drain placing apparatus 50 shown in FIG. This is a dangerous place in addition to a small work space, and is an additional work to the inevitable work of attaching the anchor plate 40 to the lower end portion 11 of the drain material 10, so that a sense of practical burden is great. If it is possible to perform the closing process even before the drain material 10 passes through the mandrel 20 and passes through the tip 22 (FIG. 7), it is desired to avoid performing it immediately below the tower 59. There are also challenges. Therefore, in the application example, the closing process as an additional work is devised so that it can be performed in a safer and easier work place.

  FIG. 5 is an explanatory diagram of the steps of the drain material placing method according to the application example of the present invention. That is, FIG. 5 refers to the placement depth measured with the previous placement, predicts the subsequent placement depth, and sets the closed portion 64 to the drain reel so as to match the predicted placement depth Yn. 54 is a work flow chart for explaining a procedure for positioning near 54, (O) placing on the 0th point, (A) placing on the first point, (B) placing on the second point, (C) Driving to the third point and (D) Driving to the fourth point are shown.

  In the first method (depth management placement method) in which the distribution of the thickness of the soft ground is investigated in advance and the depth of the drain material lower end 11 is determined and placed, if there is a large change in the formation, the investigation is performed closely. There is a need to do. In general, it cannot be found if the change is large or if there is a local change. Therefore, in the drain material placing method according to this application example, the following second and third methods (bottom management placing method) for always anchoring the anchor plate 40 to the bottom of the improvement target ground 100 are adopted. So dealt with.

  That is, in a continuous process in which the drain material 10 is driven at predetermined intervals in a plan view, the placement measured in accordance with the previous placement at the timing between the previous placement and the next placement. The subsequent placement depth Yn is predicted with reference to the depth Y0, Y1 or the increase / decrease amount E = Y1-Y0 of the placement depth. The closed portion 64 in the longitudinal direction of the drain material 10 is positioned near the drain reel 54 so as to conform to the predicted placement depth Yn. The closing position 64 positioned here is closed at the timing between the previous placement and the next placement.

  According to the drain material placing method according to the application example, the vertical movement of the mandrel 20 is (1) stopped and (2) the operation is continued at the timing between the previous placement and the next placement. It is possible to perform the closing process at any timing. (1) The reason why the mandrel 20 needs to be stopped and closed is that the closing position 60 moves away from the work site due to the relationship between the placement depth Y and the height of the tower 59. In other words, the suitable work site is in the immediate vicinity of the drain reel 54, whereas when the closing position 60 is extremely away from the drain reel 54, the handling of the drain material 10 that is extended for a long time obstructs the closing operation. Reduce efficiency. During the placing operation, the control unit 53 controls the back tension device 55 so as not to loosen the drain material 10.

  Therefore, at a timing immediately after the closing position 60 of the drain material 10 is unwound from the drain reel 54, the lowering operation (placement) of the mandrel 20 is temporarily stopped, so that the closing position 60 is made coincident with the suitable work site. Perform the closing process. Since the work efficiency is lowered during the temporary stop, the lowering operation is resumed after the closing process is quickly performed in a short time.

  On the other hand, (2) the case where the closing process is performed while the mandrel 20 is continuing the lowering operation is realized when a high-speed closing device (not shown) is used in combination. For example, this can be realized by injecting the filler 72 shown in FIG. In that case, the closing process is instantaneously completed at the timing when the closing position 60 of the moving drain material 10 passes through the work place where the high-speed closing processing device is arranged.

  In addition, a device (not shown) that absorbs the slack of the drained material 10 when the closing position 60 is close to a suitable working place closest to the drain reel 54 due to the relationship between the placement depth Y and the height of the tower 59. When used together, it is also possible to perform the closing process with the minimum time loss while the vertical movement of the mandrel 20 is stopped at the timing before the next placement starts after the end of the previous placement. Hereinafter, it will be described in detail with reference to the flowchart of FIG.

  As shown in the flow charts of FIGS. 5 (O) to 5 (D), the drain material 10 of the placement units 0 to 7 that are continuously drawn from the drain reel 54 (hereinafter simply referred to as “placement unit”). ) Is sequentially placed from point 0 to point 4 for each point. In this way, every time the placing units 0 to 4 (the placing units 5 to 7 in FIG. 5 are in the standby state) complete the placement in sequence, if the cutting unit 8 is cut at the cutting point 8 of the drain material 10, The placement unit is extended to cover the ground 100 to be improved.

  Here, only the placement unit 1 and the placement unit 4 in the drain material 10 are marked with hatching, and the movement situation corresponding to the progress of each stage of FIG. 5 (O) to FIG. 5 (D) is clarified. . First, the placement depth Y0 of the placement unit 0 shown in FIG. 5 (O) and the placement depth Y1 of the placement unit 1 shown in FIG. 5 (A) are the placement length detector 56 (FIG. 2). Can be measured more accurately. With reference to this measured value, the length of the placement unit 4 shown in FIGS. 5B to 5D is predicted. Details are as follows.

  In FIG. 3, the placement depth Y is defined as the distance from the ground surface to the anchor plate 40, but in FIG. 5, for convenience of explanation, one of the closed portions 60 to 67 is sandwiched between adjacent symbols. Each section is used as a guideline corresponding to the placement depths Y0 to Y4.

  The actual specific work is as follows. First, if the placement depth Y0 in FIG. Next, in FIG. 5A, when the anchor plate 40 comes into contact with the water permeable formation 101, the placement depth Y1 of the placement unit 1 is measured by the placement length detector 56, and the measured value is measured. Is stored by the control unit 53. Since the placement depth Y1 is deeper than the placement depth Y0 of the previous point and the increase / decrease amount E = Y1-Y0, the placement unit 1 in the drain material 10 is the increase / decrease amount E more than the placement unit 0. It is necessary to lengthen it.

  Therefore, the positions of the closing points 64, 65,... That can be easily set are set. That is, the closing point 64 is shifted toward the drain reel 54 by twice the increase / decrease amount E (hereinafter simply referred to as “increase / decrease amount 2E”), and the closing point 65 is shifted toward the drain reel 54 by the increase / decrease amount 3E in the direction of the arrow. By shifting, the length of the placement units 3 and 4 is increased compared to the placement units 0 and 1. This operation can be realized in the operation of closing the closing points 64, 65,. That is, the closing location 64 performs the closing operation at the first point in FIG. 5A, and the closing location 65 performs the closing operation at the second point in FIG. 5B.

  Thus, when the shape of the bottom of the formation is a downward slope, since the placement depth Y0 <Y1 <Y2 <Y3 <Y4 <..., the length of the placement units 0 to 4 of the drain material 10 is increased or decreased. Set so that E is added. Conversely, in the case of an ascending slope, since the placement depth Y0> Y1> Y2> Y3> Y4>..., The lengths of the placement units 0 to 4 are set so as to be sequentially reduced. Note that FIG. 5 is a schematic explanatory diagram, and the actual situation is not necessarily scaled down accurately.

  The timing at which the respective closing locations 60 to 63 in the placement units 1 to 3 shown in FIG. First, the closing position 61 of the placing unit 1 is a position higher than the ground (about 1 m), and is closed by pulling out the drain material 10 about 2 m laterally from directly below the tower 59 (FIG. 1) (not shown). Although it is not impossible to perform the processing work, it is not possible to cope with the mandrel 20 in particular during the up and down period.

  Moreover, since the closing location 62 of the placement unit 2 is near the top of the tower 59 exceeding the ground height of 30 m, the closing process at this position cannot be performed. On the other hand, if the closing position 63 of the placing unit 3 is in this position with respect to the drain material 10 immediately after being supplied from the drain reel 54, an appropriate closing process can be performed. That is, this position is a low position of about 1 m above the ground, and is a little away from directly below the tower 59, so it is a place where it is relatively easy to ensure safety.

  If the timing is other than the press-fitting process of the drain material 10, for example, during the process of pulling up the mandrel 20, the supply operation of the drain material 10 wound around the drain reel 54 is stopped. Further, if the closing process is added during the process, the overall process processing time does not increase. Accordingly, if the closing process is performed in parallel with the timing other than the press-fitting process of the drain material 10, that is, the process of supporting the press-fitting, it is possible to execute the closing process without reducing the overall work efficiency. is there.

  Therefore, it is optimal to add a closing process at the position of the closing point 63 of the placing unit 3 at the 0th point in FIG. 5 (O) in terms of overall work efficiency and easy safety. It is. In addition, in order to position the closed portions 63 to 67 somewhere in the longitudinal direction of the drain material 10 immediately after being supplied from the drain reel 54, it is placed before the 0th point in FIG. 5 (O). It is necessary to refer to the actual results. As described above, the measured value, the calculated value, and the stored values obtained by the driving length detector 56 and the control unit 53 can be used as the actual performance of the driving.

  In addition, if there is a water-permeable ground layer 101 such as a gravel layer or a sand layer at the bottom of the ground 100 to be improved and the depth from the ground surface is Y, the water-permeable ground layer 101 is compared with the soft ground to be improved. Since the stratum has different hardness, it is possible to detect by the drain placing device 50 that the tip 22 of the mandrel 20 is in contact with the water permeable stratum 101. That is, as described with reference to FIG. 2, when the anchor plate 40 locked to the tip of the placing unit 1 comes into contact with the permeable formation 101, the permeable formation having a hardness different from that of the soft ground. The press-fit resistance of the mandrel 20 with respect to 101 changes. The change is detected by the hydraulic resistance detector 21 as a change in detection output.

  Further, the placement depths Y0 to Y4 from the ground surface can be monitored in real time by the placement length detector 56. According to the drain material placing method according to the application example described here, the distance X from the upper surface of the water permeable stratum 101 is measured for all the drain material lower end portions 11 using the measurement values obtained relatively easily. It is possible to make the depths spaced apart upward. Therefore, the closed locations 60 to 64 that are spaced upward by the distance X from the plurality of drain material lower end portions 11 that are continuously placed can easily ensure a certain separation distance X from the upper surface of the water-permeable base layer 101.

  As a result, no sediment or the like flows from the drain material lower end 11 where the filter 19 is not covered. Therefore, clogging does not occur in the drain material 10. As a result, the drain length at the time of design is maintained, so that the error from the design value is reduced in the construction period and finished state. Further, the pressure in the drain is not easily reduced. Due to these characteristics, the work efficiency of the drain material placement can be increased.

  According to the drain material placement method according to the application example described above, even if the placement depths Y0 to Yn vary as the formation changes, all the drain material lower end portions 11 are constant from the permeable formation 101. Thus, it is possible to efficiently perform the operation of continuously placing the separation distance X. Moreover, earth and sand etc. do not flow in from the drain material lower end part 11 where the filter 19 is not covered. Therefore, clogging does not occur in the drain material 10. As a result, the drain length at the time of design is maintained without being changed due to clogging, so that the error from the design value is reduced with respect to the construction period and the finished state. Further, the pressure in the drain is not easily reduced. Thus, according to the drain material placing method according to the application example of the present invention, a good effect was achieved.

  As described above, according to the drain material placing method according to the application example, it is possible to manage the separation distance X from the lower end portion 11 of the drain 10 to the permeable formation 101 and continuously. As a result, it is possible to improve work efficiency while ensuring safety.

[Drain material]
FIG. 6 is a perspective view partially cut to explain the structure of the drain material. As shown in FIG. 6, the drain material 10 has a core material 18 through which pore water in the improvement target ground 100 (see FIG. 1) passes and a pore water in the improvement target ground 100 provided around the core material 18 is permeated. Filter 19. The core material 18 is provided with a plurality of partition walls extending in the longitudinal direction on both surfaces of the long body, whereby a plurality of grooves 18a serving as moisture passages in the improvement target ground 100 are formed in the longitudinal direction. Yes. The core material 18 is a material that keeps the water passage performance even when deformed and the flexibility to follow the ground subsidence. Because of this flexibility, it is possible to wind reels that are easy to supply long, so they are compact and convenient for transportation and convenience. The core material 18 is formed using, for example, polypropylene, polyethylene, or other resin material. Moreover, even if the core material 18 is made of, for example, a biodegradable resin material, the environmental load can be reduced even when the core material 18 is left in the improvement target ground 100.

  The filter 19 covering the periphery of the core material 18 is formed of a material having water permeability, for example, a polyester non-woven fabric. The filter 19 is wound around the core member 18 and is bonded by heat welding or the like to cover the periphery of the core member 18. Also, the filter 19 can be made of, for example, a biodegradable nonwoven fabric, similarly to the core material 18, thereby reducing the environmental load.

  The drain material 10 is manufactured in advance at the manufacturing plant by covering the core material 18 with the filter 19 as described above, and after being wound in a roll shape, is carried into the construction site and is predetermined on the improvement target ground 100. Placed at intervals. Next, the drain material 10 is connected by overlapping the extra length protruding from the ground surface on a horizontal drain (not shown).

[Relationship between mandrel, drain material and anchor plate]
FIGS. 7A and 7B are explanatory views showing a state where the anchor plate can be locked and driven at the tip of the drain material inserted through the mandrel. FIG. 7A is an overall side sectional view and FIG. 7B is a schematic plan view. The mandrel 20 shown in FIG. 7 is a cylindrical body having a spire shape whose lower end is flat like a flathead screwdriver and having a slit hole. The drain material lower end portion 11 inserted into the cylinder from above the mandrel 20 is pulled out from the lower slit hole, and the anchor plate 40 is drawn to the outside of the lower end of the mandrel 20 so that it can be driven. Since the back tension is applied upward by the back tension device 55 above the drain material 10, stress that pulls the drain material lower end portion 11 and the anchor plate 40 fixed thereto acts upward. The drain material 10 has no slack.

[Drain material and anchor plate locking]
FIG. 8 is a perspective view for explaining a shape in which the anchor plate 40 is locked to the drain material lower end portion 11 of FIG. As shown in FIG. 8, the anchor plate 40 is a metal member in which a handle-like locking fitting is attached to the upper surface of a rectangular metal plate having a flat bottom surface by welding or the like. The drain member lower end portion 11 is inserted through the locking metal fitting 41 and pulled out, and then turned back, returned upward by a predetermined length from the turning point 12, and pulled back into the mandrel 20 in that state.

  Note that the drain material placing method according to the present invention is effective as a measure for preventing clogging of the drain material 10 due to suction from the lower end portion 11 of the drain material 11, that is, the end surface not covered with the filter 19, together with moisture to earth and sand. Is.

[Experimental result]
The state of inflow of earth and sand into the drain material 10 when the drain material lower end portion 11 was closed and not was verified. First, after briefly explaining the result of this experiment result that it is effective to seal (seal) the drain material lower end 11, the experimental apparatus shown in FIG. 9 and the main experimental data shown in FIG. 10 and FIG. Will be described.

(1) When a vacuum pressure was applied while the drain material lower end portion 11 was not sealed, the invasion of about 1 m of clay from the drain material lower end portion 11 could be confirmed.
(2) The intrusion of clay into the drain material 10 not only deteriorates the water permeability of the drain material 10 itself, but also deteriorates to a state deviating from the original design by replacing the drain (drainage) functional part with clay. Conceivable.
(3) From the results of this experiment, it was confirmed that the drain material lower end 11 must be sealed (sealed) in the vacuum consolidation method.

  FIG. 9 is a schematic explanatory diagram of an experimental apparatus (hereinafter, also referred to as “the present verification apparatus”) that verifies the difference in drainage function depending on whether or not the drain material lower end portion 11 is sealed. As shown in FIG. 9, the verification device 80 fills a 200-liter water tank 81 with Kasaoka clay 82, in which the drain material 10 to be tested is wound and submerged, and is opposite to the drain material lower end 11. Is connected to a drainage tank 84 through a socket (connecting member) 13 and a nylon tube 83 that can be hermetically connected from the section, and the drainage tank 84 is negative pressure (maximum 88 kPa) by a vacuum pump 86 connected through a nylon tube 85. It is the structure sucked in. The verification apparatus 80 configured in this manner simulates ground improvement work for dewatering soft ground by a vacuum consolidation method, and was continuously operated for 1 to 2 weeks in this experiment.

The Kasaoka clay 82 is known to be distributed around Kasaoka City, Okayama Prefecture, and 400 kg of a commercial product called “Kasaoka Clay” has a soil particle density of 2.717 g / cm ³ and a liquid limit of 59. This verification apparatus 80 was simulated and prepared in the soil of the ground to be improved 100 (see other figures) after being prepared and confirmed in a state of 5%, an initial moisture content of 89.12 to 92.38%, and a clay moisture content of around 1.5. Used for.

  Further, the drain material 10 is used in the vacuum consolidation method. The cross-sectional dimensions shown in FIG. 6 are 100 mm in width × 4 mm in thickness × 1 m in length, and are used for the experiment in the winding state shown in FIG. . In addition, the range other than 10 cm from the drain material lower end 11 was wound twice or more with a polyethylene air-impermeable film so as to be covered with an air-impermeable film (not shown). Moreover, the state which made the drain material lower end part 11 with a seal | sticker implement | achieved by sealing the drain material lower end part 11 with a vinyl tape.

  FIG. 10 is a graph showing the change over time in the amount of drainage with a drain length of 1 m in this verification apparatus. As shown in the graph of FIG. 10, the amount of drainage is initially greater when the drain material lower end 11 is not sealed (not closed) than when the seal is present (closed), but gradually with time. It tends to decrease. This is because earth and sand flow into the drain material 10 and become clogged. A capacity scale like a female cylinder is attached to the transparent wall surface of the cylindrical drainage tank 84, and the amount of drainage is detected by directly reading the amount of water accumulated and stored in the drainage tank 84.

  Further, during the experiment, the water accumulated and stored in the drainage tank 84 is turbid due to the mixing of the Kasaoka clay 82 when there is no seal, but it is almost transparent when there is a seal.

  FIG. 11 is a photograph of the drain material comparing the verification results when the vacuum pressure is applied for a predetermined time according to the conditions by the verification apparatus. As shown in FIG. 11 (A), when the lower end of the drain material was sealed (sealed), it was confirmed that there was little deterioration with time of the drainage function because there was no clay intrusion. On the other hand, as shown in FIG. 11 (B), when the drain material lower end was not sealed and opened, it was confirmed that clay had entered from the lower end of the drain material to a depth of about 1 m.

  More specifically, after the experiment is completed, the filter 19 (see FIG. 6) is disassembled from the drain material 10 and observed. As a result, when the drain material lower end 11 has a seal, the Kasaoka clay 82 to the core material 18 (FIG. 6). There was almost no intrusion. On the other hand, in the case of no seal, it was confirmed that the Kasaoka clay 82 entered about 1 m from the lower end 11 of the drain material.

  The result of whether or not soil or sand that has an adverse effect on the drainage function in actual construction invades about 1 m from the drain material lower end 11 is clear as can be seen from the above-described difference in the turbidity of the drainage. Therefore, from this experimental result, it can be concluded that there is an effect of improving the construction efficiency by sealing the drain material lower end portion 11 in the vacuum consolidation method using the drain material placing method according to the present invention.

  The drain material placing method according to the present invention can be applied to ground improvement work for dehydrating soft ground by applying a vacuum consolidation method.

0 to 7 Drain material 10 placement unit, 8 Drain material 10 cutting point, 10 Drain material, 11 Lower end of drain material 10, 12 Folding point of drain material 10, 18 Core material, 18a Groove, 19 Filter, 20 Mandrel, 21 Hydraulic resistance detector, 22 Tip of mandrel 20, 30 Rope, 40 Anchor plate, 41 Locking bracket, 50 Drain driving device, 51 Caterpillar device, 52 Base, 53 Control unit, 54 Drain reel, 55 Back tension Equipment, 56 Casting length detector, 59 Tower, 60-67 Closed location, 71 Clamping tool, 72 Filler, 73 Sealed bag, 80 Experimental equipment (this verification equipment), 81 Water tank, 82 Kasaoka clay, 13 Socket (connection) Member), 83 nylon tube, 84 drainage tank, 85 nylon tube, 86 vacuum 90, near the placement point, 100 ground to be improved, 101 permeable formation, E (increase / decrease in the placement depth Y), X a predetermined distance vertically above the top surface of the permeable formation 101, Y placement depth, Y0, Pitching depth measured with Y1 first placement, Pitching depth after Yn

Claims (10)

In the soft improvement target ground having a permeable formation such as gravel layer and sand layer in the deep part,
The drain material used to improve the ground by dehydrating by applying the vacuum consolidation method is inserted into the mandrel which is a guide for burial,
An anchor plate is connected via a rope at the lower end of the drain material,
Press-fit into the improvement target ground with a drain placing device that can be press-fitted together with the mandrel,
Then, the drain material placing method for raising the mandrel to the ground and burying the drain material in the ground to be improved,
While setting the effective length of the rope so that the lower end portion of the drain material is positioned vertically upward by a predetermined distance from the upper surface of the water permeable formation,
A drain material placing method, wherein the lower end portion of the drain material is closed. In the soft improvement target ground having a permeable formation such as gravel layer and sand layer in the deep part,
The drain material used to improve the ground by dehydrating by applying the vacuum consolidation method is inserted into the mandrel which is a guide for burial,
An anchor plate is connected via a rope at the lower end of the drain material,
Press-fit into the improvement target ground with a drain placing device that can be press-fitted together with the mandrel,
Then, the drain material placing method for raising the mandrel to the ground and burying the drain material in the ground to be improved,
Within a predetermined distance vertically above the upper surface of the water permeable formation, while adjusting the placement depth so as not to reach the drain material,
The drain material placing method, wherein an effective length of the rope is set so that a length from a lower end portion of the drain material to the anchor plate is maintained at the predetermined distance. In the soft improvement target ground having a permeable formation such as gravel layer and sand layer in the deep part,
The drain material used to improve the ground by dehydrating by applying the vacuum consolidation method is inserted into the mandrel which is a guide for burial,
An anchor plate is connected to the lower end of the drain material,
Press-fit into the improvement target ground with a drain placing device that can be press-fitted together with the mandrel,
Then, the drain material placing method for raising the mandrel to the ground and burying the drain material in the ground to be improved,
A drain material placing method, wherein suction of soil and sand of the drain material located within a predetermined distance in a vertically upward direction from an upper surface of the water permeable formation is cut off.   The drain material placing method according to any one of claims 1 to 3, wherein the predetermined distance is 0.5 to 2.0 m.   4. The drain material positioned within the range of the predetermined distance is closed so as to prevent distribution in the longitudinal direction, and suction of earth and sand on the side deeper than the closed closed portion is blocked. Or the drain material placing method of 4. In a continuous process in which the drain material is placed at predetermined intervals in plan view,
At the timing between the previous placement and the next placement, refer to the placement depth measured with the previous placement or the increase / decrease amount of the placement depth to predict the subsequent placement depth,
Positioning the closure point in the longitudinal direction of the drain material close to the drain reel to match the predicted placement depth after;
6. The drain material placing method according to claim 5, wherein the closing process is performed on the positioned closing position at the timing.   The drain material placing method according to claim 5 or 6, wherein the closed portion subjected to the closing process is folded in a Z shape when the drain material is viewed from the width direction.   The drain material placing method according to any one of claims 5 to 7, wherein a clamping tool is attached to the drain material as the closing process.   The drain material placing method according to any one of claims 5 to 8, wherein the drain material is filled with a filler as the closing process.   The drain material placing method according to any one of claims 5 to 9, wherein a sealing bag is put on the drain material from the tip as the closing process.