Shield arrival structure and shield arrival method

Abstract

To provide shield arrival structure and a shield arrival method that can secure stability of surrounding the natural ground and aim at improving workability in making a shield tunnelling machine arrive under the water surface.SOLUTION: The present invention relates to shield arrival structure 1 comprising a box body 2 having a socket 21 of a shield tunnelling machine M to tunnel through the water bottom ground and a shield accommodation pipe 3 capable of accommodating the shield tunnelling machine M advancing from the socket 21 into the box body 2, and a shield arrival method to the shield arrival structure 1. A solidified substance capable of boring by the shield tunnelling machine M is filled inside the socket 21 and inside the shield accommodation pipe 3. In addition, the shield accommodation pipe 3 is detachably connected to the socket 21, and has a water filler 31 for taking in water being present around the shield accommodation pipe 3 into the shield accommodation pipe 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shield access structure and a shield access method. [Background technology]

[0002] Tunnel construction using the shield method is typically carried out by placing a shield machine at a specified depth in a starting shaft and then driving it toward a destination shaft. After construction is complete, the shield machine is often partially or completely withdrawn from the destination shaft.

[0003] The shield tunneling method covers the ground with a lining (segment rings) without exposing the ground, so it can prevent ground collapse even in soft ground that is relatively difficult to stand on its own.For this reason, the shield tunneling method is sometimes used when constructing tunnels underwater, such as at the bottom of the sea or river.

[0004] When constructing a tunnel through a body of water using the shield method, there are cases in which the shield machine is made to reach an arrival shaft formed at the bottom of the water. Patent Document 1 discloses a method for recovering the shield machine underwater after it has reached the arrival shaft formed at the bottom of the water.

[0005] The shield machine recovery method described in Patent Document 1 involves separating and recovering the shield machine from its segments underwater. In this recovery method, the interior of the shield machine is divided into sections in the axial direction by front and rear bulkheads spaced a predetermined distance apart, and then the shield machine is separated between the front and rear bulkheads, and the shield machine separated by the front bulkhead is recovered from underwater. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-126991 Summary of the Invention [Problem to be solved by the invention]

[0007] In the construction method of Patent Document 1, the shield tunneling machine is driven directly into the arrival shaft, which creates the risk of soil and sand flowing in through the gap between the outer surface of the shield tunneling machine and the entrance to the arrival shaft. If soil and sand flow into the shaft, visibility will be reduced, affecting work inside the shaft. Furthermore, the inflow of soil and sand into the shaft could cause the ground around the shaft and the tunnel to loosen. Furthermore, the construction method of Patent Document 1 requires the installation of a front bulkhead and a rear bulkhead, which makes the installation of the bulkheads time-consuming.

[0008] The present invention aims to provide a shield access structure and a shield access method that ensure the stability of the surrounding ground and improve workability when a shield tunneling machine reaches below water level. [Means for solving the problem]

[0009] To solve the above problems, the shield access structure of the present invention includes a box having a socket for a shield machine that excavates the waterbed, and a shield encasement pipe capable of accommodating the shield machine that has advanced into the box from the socket. The interior of the socket and the shield encasement pipe are filled with a solidified material that can be excavated by the shield machine. The shield encasement pipe is detachably connected to the socket and has a water inlet for drawing water present around the shield encasement pipe into the shield encasement pipe.

[0010] In addition, the shield access method of the present invention comprises a reach section construction step of constructing the shield reach structure, an excavation step of advancing the shield tunneling machine to the receiving port, an access excavation step of advancing the shield tunneling machine from the receiving port into the shield storage pipe, a segment removal step of removing a removal segment placed at the boundary between the receiving port and the shield storage pipe and the solidified body remaining on the back side of the removal segment, a water injection step of opening the water inlet to inject water present around the shield storage pipe into the shield tunnel, and a storage pipe removal step of removing the shield storage pipe from the receiving port and removing it from the box body.

[0011] According to this shield access structure and shield access method, a shield encasement pipe capable of housing a shield machine is provided within the box, and the inside of the socket and the inside of the shield encasement pipe are filled with solidified material, preventing soil and sand from flowing into the arrival shaft (inside the box) when the shield machine arrives. This maintains the stability of the ground around the shield tunnel and the shaft. Furthermore, when the shield machine is withdrawn, water is poured into the shield tunnel, eliminating the need to form a bulkhead.

[0012] It is preferable that, before the segment removal step, a water-stopping injection is performed from the segment placed in the receiving port to the outside of the segment. It is also preferable that the method further includes a water-stopping step of sealing the gap between the inner peripheral surface of the receiving port and the outer peripheral surface of the tunnel lining left in the receiving port from the space side formed by the segment removal step, and a covering step of covering the solidified body remaining inside the shield encasement pipe from the space side formed by the segment removal step.

[0013] If the box is installed below water level and a temporary surveying structure with an upper surface protruding above the water surface is erected on the box, the excavation process can be carried out while checking the relative positions of the shield machine and the socket using surveying equipment installed above the water surface. This allows for more accurate tunnel construction. If the box is a cylindrical structure with an open top and a closed bottom, the temporary structure can have multiple masts erected on the bottom of the box.

[0014] The reach section construction process preferably includes the following steps: bottom excavation, which forms a recess by bottom excavation at the reach of the shield machine that excavates the bottom ground; box installation, which installs the box on the bottom of the recess; and backfilling, which fills in the area around the box. In this case, the backfilling involves pouring underwater non-separating mortar that can be excavated by the shield machine at least up to the top of the socket. This prevents the ground from loosening as the shield machine excavates, since an artificial ground made of mortar is placed around the box. Pouring underwater non-separating concrete on top of the underwater non-separating mortar is less expensive than using mortar. [Effects of the Invention]

[0015] According to the shield access structure and shield access method of the present invention, it is possible to ensure the stability of the ground around the tunnel and shaft, and to improve workability. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 10 is a cross-sectional view showing a shield reach structure. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] 10 is a flowchart showing the steps of a shield reaching method. [Figure 5]10A and 10B are diagrams showing the construction process of the reach section, in which (a) shows the excavation work and (b) shows the bottom leveling work. [Figure 6] 6A and 6B are diagrams showing the construction process of the arrival section following FIG. 5, in which (a) shows the box installation work and (b) shows the backfilling work. [Figure 7] This is a cross-sectional view showing the reaching excavation process to the water injection process. [Figure 8] 10A and 10B are diagrams showing a process of removing the encasing tube. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In this embodiment, a case will be described in which a tunnel (shield tunnel) is formed by excavating the water bottom toward an arrival shaft formed at the bottom of the water. The tunnel is formed by excavating the water bottom ground with a shield machine and assembling segments behind the shield machine to provide a lining. Figure 1 shows a shield arrival structure 1 (arrival shaft).

[0018] As shown in Figure 1, the shield access structure 1 comprises a box body 2 having a receiving port 21 for a shield tunneling machine M, a shield storage pipe 3 capable of accommodating the shield tunneling machine M that has advanced into the box body 2 from the receiving port 21, an artificial ground section 4 formed between the receiving port 21 and the waterbed G, and a temporary structure 5 for surveying.

[0019] The box body 2 is made of a concrete precast caisson, and as shown in Figure 1, is cylindrical with an open top and a closed bottom. The box body 2 is installed below the water surface on the bottom of a recess 6 formed in the waterbed ground G by excavating the bottom of the water. The recess 6 is formed by excavating the waterbed ground G in the shape of an inverted truncated square pyramid or an inverted truncated cone. The bottom surface 61 of the recess 6 has a larger area than the bottom surface of the box body 2, and flatness is ensured by riprap 63 or the like.

[0020] A receiving port 21 into which a shield machine M can be inserted is formed on the wall surface of the box body 2 on the starting shaft side. In this embodiment, the receiving port 21 is formed by combining steel segments to form a cylindrical body with an inner diameter larger than the outer diameter of the shield machine M. The inside of the receiving port 21 (cylindrical body) is filled with a solidified body 22 that can be excavated by the shield machine M and has water-stopping properties. In this embodiment, the solidified body 22 filled in the receiving port 21 is low-strength mortar (uniaxial compressive strength σ 28 =6220kN / m 2 The solidified body 22 filled inside the receiving port 21 is not limited as long as it is a material that can be excavated by the shield machine M.

[0021] The artificial ground portion 4 is formed between the side surface (slope) 62 of the recess 6 and the outer surface of the box body 2. The artificial ground portion 4 is formed by pouring a solidified material that can be excavated by a shield tunneling machine M around the box body 2 from the bottom surface 61 of the recess 6 to a height higher than the upper end of the socket 21. In this embodiment, underwater non-separating mortar is used as the solidified material that constitutes the artificial ground portion 4. The artificial ground portion 4 is covered with a covering portion 7. The covering portion 7 is formed by pouring underwater non-segregating concrete from the upper surface of the artificial ground portion 4 to the upper end of the recessed portion 6.

[0022] The shield encasement pipe 3 is made of a tubular body that can accommodate the shield tunneling machine M, and is removably connected to the socket 21. The shield encasement pipe 3 of this embodiment is made up of a combination of steel segments, resulting in a tubular body with an inner diameter that is larger than the outer diameter of the shield tunneling machine M. The shield encasement pipe 3 is bolted to the cylindrical body that constitutes the socket 21. The shield encasement pipe 3 is shown in Figure 2.

[0023] As shown in FIG. 2, the shield encasement tube 3 has a water inlet 31 for taking in water present around the shield encasement tube 3 and an air vent 32 for venting air from the inside during water injection. The water inlet 31 and the air vent 32 are made of pipes that penetrate the steel segments that make up the shield encasement tube 3. As shown in FIG. 1, the inside of the shield encasement tube 3 is filled with a solidified body 33 that can be excavated by a shield tunneling machine M. In this embodiment, liquefied treated soil is used as the solidified body filled inside the shield encasement tube 3, but the solidified body 33 filled inside the shield encasement tube 3 is not limited. Furthermore, the shield encasement tube 3 is supported by a frame 35 formed by combining steel materials. Buffer material is provided around the shield encasement tube 3 as needed.

[0024] FIG. 3 shows the temporary structure 5. As shown in FIG. 3, the temporary structure 5 is erected on the box body 2 and has an underwater section 51 that protrudes above the water surface and on which surveying equipment can be installed. The temporary structure 5 is formed by combining steel pipes or steel materials and has multiple masts 52 (four in this embodiment) erected on the bottom of the box body 2 and horizontal members 53 that are connected horizontally to adjacent masts 52. The masts 52 have a length that protrudes above the water surface, and the portions of the masts 52 above the water surface form the underwater sections 51 on which surveying equipment can be installed. The masts 52 are provided with ladders (not shown) that divers and others can use to climb up and down when installing surveying equipment. In this embodiment, the masts 52 are erected at corners of the bottom of the box body 2. The installation location of the masts 52 is not limited; for example, they may be erected at the upper ends of the side walls of the box body 2.

[0025] The shield reach method of this embodiment will be described below. The steps of the shield reach method are shown in Figure 4. As shown in Figure 4, the shield reach method includes a reach section construction process S1, an excavation process S2, a reach excavation process S3, a segment removal process S4, a covering process S5, a water stopping process S6, a water injection process S7, and a housing pipe removal process S8.

[0026] In the reach section construction process S1, a shield reach structure 1 is constructed. The reach section construction process S1 is shown in FIGS. 5 and 6. In the reach section construction process S1, first, as shown in FIG. 5(a), bottom excavation work is performed to form a recess 6 by excavating the bottom of the water at the reach position of the shield tunneling machine M. Next, as shown in FIG. 5(b), bottom leveling work is performed to flatten the bottom surface 61 of the recess 6 by laying riprap or the like on it. Next, as shown in FIG. 6(a), box installation work is performed to install the box 2 on the bottom surface 61. At this time, the shield encasement pipe 3 and temporary structure 5 have already been installed in the box 2. In addition, solidified bodies 22 and 33 have been filled in the receiving port 21 and the shield encasement pipe 3, respectively.

[0027] Once the box body 2 is installed, backfilling work is carried out to fill in the area around the box body 2, as shown in Figure 6(b). In the backfilling work, underwater non-separating mortar that can be excavated by the shield tunneling machine M is poured at least up to the upper end position of the receiving hole 21 to form the artificial ground portion 4. Once the underwater non-separating mortar has developed a predetermined strength (after the underwater non-separating mortar has cured), underwater non-separating concrete is poured on top of the underwater non-separating mortar to form the covering portion 7.

[0028] In the excavation step S2, the shield machine M is advanced to the socket 21 (see FIG. 1). In this embodiment, excavation is performed by the shield machine M, and concrete segments are assembled behind the shield machine M. In the excavation step S2, surveying equipment installed on the underwater section 51 of the temporary structure 5 erected on the box body 2 is used to confirm the positional relationship between the shield machine M and the socket 21 while excavating. The socket 21 is measured by measuring reference points on the revetment and surveying equipment such as an omnidirectional mirror and a satellite positioning system antenna installed on the underwater section 51. In this embodiment, the relative coordinates of the socket 21 and the underwater section 51 are measured above ground before the box body 2 is installed in the recess 6 (for example, during the manufacture of the box body 2). In this way, the position coordinates of the socket 21 can be calculated by surveying the underwater section 51 (obtaining the coordinates of the four masts 52, 52, ...).

[0029] In the arrival excavation step S3, the shield machine M is caused to excavate up to the inside of the shield encasement pipe 3. In this embodiment, as the shield machine M excavates, steel segments are assembled behind the shield machine M. Figure 7 shows the arrival excavation step S3 to the water injection step S7. As shown in Figure 7, the shield machine M penetrates the socket 21 and enters the shield encasement pipe 3. At this time, the shield machine M advances while excavating the solidified body 22 (low-strength mortar) inside the socket 21 and the solidified body 33 (liquefied treated soil) inside the shield encasement pipe 3. The shield machine M excavates until the entire machine is housed inside the shield encasement pipe 3. Segments are also assembled from the socket 21 to the rear of the shield machine M inside the shield encasement pipe 3. Once the shield tunneling machine M is housed in the shield housing pipe 3, water-stopping injection (chemical injection) is performed from the segment placed in the receiving port 21 to the outside of the segment (backfill material in the gap between the segment and the solidified body 33). Once the shield tunneling machine M reaches the inside of the shield housing pipe 3, the temporary structure 5 is removed. The temporary structure 5 is removed by cutting the lower end of the mast 52 near the bottom of the box body 2.

[0030] In the segment removal process S4, the removal segment placed at the boundary between the receiving port 21 and the shield encasement pipe 3 is removed. At this time, the solidified body 33 (liquefied treated soil) remaining on the back side of the removal segment is also removed. The removal segment and solidified body 33 are removed from inside the tunnel. In the area where the removal segment and solidified body 33 have been removed, the inner surface of the shield encasement pipe is exposed.

[0031] In the covering step S5, the solidified body 33 (liquefied treated soil) remaining inside the shield encasement pipe 3 is covered. That is, the end faces of the solidified body 33 exposed by removing the removal segments are covered to prevent the outflow of water that has permeated the solidified body 33 and the formation of water paths. The solidified body 33 is covered by installing a water-conducting material from the side of the space formed by removing the removal segments in the segment removal step S4, and then installing a steel plate (waterstop plate 34) on its surface. The steel plate is reinforced with ribs or the like as necessary.

[0032] In the watertightness step S6, water is stopped by sealing the gap between the inner peripheral surface of the receiving port 21 and the outer peripheral surface of the tunnel lining (segment) left inside the receiving port 21. This prevents water paths from forming along the outer surface of the segment. The watertightness treatment between the inner peripheral surface of the receiving port 21 and the outer peripheral surface of the tunnel lining left inside the receiving port 21 is performed from the side of the space formed by removing the segment to be removed in the segment removal step S4.

[0033] In the water injection process S7, water is injected into the shield tunnel. Water is injected into the shield tunnel by opening the water injection port 31 of the shield encasement tube 3 and taking in the water that is present around the shield encasement tube 3. At this time, the air vent 32 is opened to vent the air inside the shield encasement tube 3. Because the water pressure around the shield tunnel is greater than the air pressure inside the shield tunnel, water can be taken in simply by opening the water injection port 31. Once the shield tunnel is filled with water, the pressure difference between the inside and outside of the shield tunnel disappears.

[0034] Figure 8 shows the encasement tube removal process. In the encasement tube removal process S8, as shown in Figure 8, the shield encasement tube 3 is removed from the socket 21 and removed from the box body 2. At this time, the shield tunneling machine M is removed together with the shield encasement tube 3 while still housed in the shield encasement tube 3. The shield encasement tube 3 is separated into the removed portion and the remaining portion by removing the bolts at the boundary with the remaining portion. To make it easier to identify the bolts to be removed underwater, it is preferable to color the bolts to be removed in advance with fluorescent paint or the like. Because the shield tunnel is filled with water, water does not suddenly flow into the shield tunnel when the shield encasement tube 3 is removed.

[0035] According to the shield access structure 1 and shield access method of this embodiment, a shield encasement pipe 3 capable of accommodating a shield tunneling machine M is provided inside the box body 2, and the inside of the socket 21 and the inside of the shield encasement pipe 3 are filled with solidified body 33, preventing earth and sand from flowing into the access shaft (inside the box body 2) when the shield tunneling machine M arrives. This maintains the stability of the ground around the shield tunnel and around the access shaft.

[0036] Furthermore, when the shield tunneling machine M (shield housing pipe 3) is retrieved, water is poured into the shield tunnel, eliminating the need to form a partition between the retrieved part and the remaining part of the shield tunneling machine M. Furthermore, because water is poured into the shield tunnel to remove any air pockets within the shield tunnel, there is no risk of air escaping from within the shield tunnel when the shield tunneling machine M is removed, ensuring safety.

[0037] Construction using the shield tunneling machine M can be carried out with high precision because the coordinates can be confirmed using the temporary structure 5. Around the box body 2, underwater non-segregating mortar that can be excavated by the shield machine M is poured, so construction by the shield machine M is not hindered by backfill material, and artificial ground made of mortar is placed around the box body, so the ground is prevented from loosening as the shield machine M excavates. Also, because underwater non-segregating concrete is poured on top of the underwater non-segregating mortar, it is less expensive than backfilling the entire recess with underwater non-segregating mortar.

[0038] In addition, before the segment removal process S4, a waterproof injection is performed from the segment placed inside the receiving port 21 to the outside of the segment, thereby preventing soil and sand from flowing into the space from which the segment has been removed from the surrounding area.

[0039] In addition, by sealing the space between the inner surface of the receiving port 21 and the outer surface of the tunnel lining left inside the receiving port 21 from the side of the space formed by the segment removal process S4, it is possible to prevent soil and sand, etc. from flowing into the tunnel along the tunnel.

[0040] By covering the solidified body 33 remaining inside the shield housing pipe 3 from the space side formed by the segment removal process S4 with a water stop plate 34, it is possible to prevent the solidified body (liquefied treated soil) 33 from flowing into the tunnel or flowing out into the construction water area.

[0041] In the reaching excavation step S3, steel segments are used, which makes it easy to remove the segments. In other words, steel segments are lighter than reinforced concrete segments, making them easier to handle. On the other hand, in the general section of the tunnel construction (excavation step S2), concrete segments are used, which ensures flatness inside the tunnel (few irregularities on the inner surface).

[0042] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-described components can be appropriately modified within the scope of the present invention. In the above embodiment, the artificial ground portion 4 is formed using underwater non-separating mortar, but the material that constitutes the artificial ground portion 4 is not limited as long as it can be excavated using a shield tunneling machine M and is difficult to separate underwater.

[0043] Furthermore, the artificial ground portion 4 may be formed between the side surface 62 of the recess 6 and the receiving port 21 using underwater non-segregating mortar, and the other portions may be formed using underwater non-segregating concrete. Furthermore, the covering portion 7 may be formed as needed. For example, if the artificial ground portion 4 is formed up to the height of the upper end of the box body 2, the covering portion 7 may be omitted.

[0044] In the above embodiment, the case where the box body 2 on which the temporary structure 5 is provided in advance is installed in the recessed portion 6 has been described, but the temporary structure 5 may be fixed to the box body 2 after the box body 2 is installed in the recessed portion 6. Also, the box body 2 on which a part (base) of the temporary structure 5 is installed may be installed in the recessed portion 6, and then the remaining part of the temporary structure 5 may be fixed.

[0045] In the above embodiment, the type of segment is changed depending on the location, but the type of segment used in the construction of the tunnel is not limited. That is, the same type of segment may be used throughout the entire section. [Explanation of symbols]

[0046] 1. Shield reach structure 2 box 21 socket 22 Solidified body 3 Shielded housing tube 31 Water inlet 32 Air vent 33 Solidified body 34 Waterstop (covering) 4 Artificial ground section 5 Temporary structure 51 Water upper part 52 Mast 53 Cross member 6 recess 61 bottom 62 Side 7 Covering part G underwater ground M shield tunneling machine S1 reach section construction process S2 excavation process S3 reaching excavation process S4 Segment removal process S5 Coating process S6 Water stop process S7 Water injection process S8 Removal of the storage tube

Claims

1. a box having a socket for a shield machine that excavates the waterbed; A shield access structure comprising: a shield storage pipe capable of storing a shield machine that has advanced into the box body from the receiving port; The inside of the receiving port and the inside of the shield housing pipe are filled with a solidified body that can be excavated by the shield tunneling machine, A shield access structure characterized in that the shield housing tube is detachably connected to the receiving port and has a water inlet for drawing water present around the shield housing tube into the shield housing tube.

2. 2. The shield access structure according to claim 1, wherein an artificial ground portion made of a solidified body that can be excavated by the shield tunneling machine is disposed between the bottom ground and the receiving port.

3. The box is installed on the bottom surface of a recess formed by excavating the bottom of the water, 3. The shield access structure according to claim 2, wherein the artificial ground portion is disposed between a side surface of the recess and the socket.

4. 3. The shield access structure according to claim 2, wherein the solidified body is made of underwater non-separating mortar.

5. A covering portion is provided to cover the upper surface of the artificial ground portion, 5. The shield access structure according to claim 4, wherein the covering portion is made of underwater non-segregating concrete.

6. The box is installed below the water surface, 2. The shield access structure according to claim 1, further comprising a temporary surveying structure erected on the box body and having an underwater portion protruding from the water surface onto which surveying equipment can be installed.

7. The box has a cylindrical shape with an open top and a closed bottom, 7. The shield access structure according to claim 6, wherein the temporary structure has a plurality of masts erected on the bottom of the box body.

8. a reach portion construction step of constructing the shield reach structure according to claim 1; an excavation step of causing the shield machine to excavate to the receiving hole; an arrival excavation step of causing the shield machine to excavate from the socket to the inside of the shield housing pipe; a segment removal step of removing a removal segment disposed at a boundary between the receiving port and the shield encasement tube and the solidified body remaining on a rear side of the removal segment; a water injection step of opening the water injection port and injecting water present around the shield encasement tube into the shield tunnel; A shield access method comprising: a shield encasement tube removal step of removing the shield encasement tube from the receiving port and removing it from the housing.

9. The shield access method according to claim 8, characterized in that, before the segment removal step, water-stopping injection is performed from the segment placed in the receiving port to the outside of the segment.

10. A shield access method as described in claim 8, characterized in that it includes a water-stopping process for sealing the gap between the inner surface of the receiving port and the outer surface of the tunnel lining left in the receiving port from the space formed by the segment removal process.

11. 9. The shield access method according to claim 8, further comprising a covering step of covering the solidified body remaining inside the shield housing tube from the space formed by the segment removing step.

12. The box is installed below the water surface, A temporary surveying structure having an underwater portion protruding from the water surface is erected on the box, 9. The shield access method according to claim 8, characterized in that in the excavation process, surveying equipment installed above the water is used to check the positional relationship between the shield machine and the socket while excavating.

13. In the reaching portion construction step, a bottom excavation work to form a depression by bottom excavation at the position where the shield tunneling machine reaches, which excavates the bottom ground; a box installation operation of installing the box on a bottom surface of the recess; A backfilling operation is performed to backfill the area around the box body, 9. The shield tunneling method according to claim 8, wherein the backfilling work involves pouring underwater non-segregating mortar excavable by the shield tunneling machine at least up to the upper end position of the receiving hole.

14. 14. The shield reaching method according to claim 13, wherein the backfilling work comprises pouring underwater non-segregating concrete on top of the underwater non-segregating mortar.

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