Grouting and channeling test device for shield tail of shield tunnel under pressure condition
By designing a test device to simulate the slurry phenomenon during shield end grouting process in shield tunnel, the problem of slurry phenomenon affecting construction quality and safety during shield end grouting is solved, and the real simulation of slurry phenomenon and construction parameter optimization is achieved.
Patent Information
- Application Number
- CN202411897122.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-03-25
AI Technical Summary
During the shield end grouting process of shield tunnel, the gap between the shield shell and the formation causes the slurry to rush to the excavation surface, resulting in loss and impaired gaps, which affects the construction quality and poses safety hazards. Especially under high-pressure formation conditions, the slurry phenomenon is more serious.
A shield tunnel shield tail grouting test device under pressure conditions is designed, including a slurry assembly, a grouting assembly, a first pressurized assembly, a slurry collection assembly and a second pressurized assembly. By simulating the pressure difference between the shield tail and the excavation surface, the slurry passage is simulated to realize the real simulation of the slurry phenomenon.
This device can truly simulate the slurry phenomenon under different formation pressures during shield tunnel end grouting process, explore the degree of slurry under different construction parameters, improve the quality of shield tunnel end grouting construction, and avoid safety hazards in later tunnel operation.
Smart Images
Figure CN119688967A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of shield tunnel tail grouting, and specifically relates to a shield tunnel tail grouting and slurry mixing test device, and more particularly to a shield tunnel tail grouting and slurry mixing test device under pressure conditions. Background Art
[0002] During shield construction, since the outer diameter of the cutterhead is slightly larger than the outer diameter of the shield shell, there is a gap between the shield shell and the stratum. When the shield tail is synchronously grouting, the slurry is very likely to flow along the gap between the shield shell and the stratum to the excavation surface, which is called slurry leakage, resulting in loose filling of the gap and a decline in the quality of grouting construction at the shield tail. In serious cases, it will bury a safety hazard for the later operation of the tunnel.
[0003] When the stratum contains high-pressure gas or water, slag discharge will reduce the pressure of the excavation face, which means that there is pressure in the stratum. However, during shield construction, there is a pressure difference between the gap at the shield tail and the excavation face, which will inevitably increase the tendency of slurry to flow from the shield tail to the excavation face and increase the possibility of slurry leakage.
[0004] Studying the extent of slurry channeling under different formation pressures during shield tail grouting of shield tunnels through experimental equipment is an effective way to understand the phenomenon of slurry channeling during shield tail grouting of shield tunnels. However, there is currently a lack of effective experimental equipment for this test, which is not conducive to improving the construction quality of shield tail grouting of shield tunnels. Summary of the invention
[0005] The purpose of the present invention is to provide a shield tail grouting and slurry leakage test device for a shield tunnel under pressure conditions in order to solve the above problems.
[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:
[0007] A shield tail grouting and grouting test device for a shield tunnel under pressure conditions, comprising a grouting assembly for simulating a grouting process, a grouting assembly for injecting slurry, a first pressurizing assembly for simulating high pressure at the shield tail, a slurry collecting assembly for collecting slurry, and a second pressurizing assembly for simulating high pressure on an excavation face, wherein the grouting assembly comprises a first end plate, a second end plate, an outer tube, an inner tube, and a connecting rod, wherein the two ends of a plurality of transverse connecting rods are respectively fixedly connected to the vertical first end plate and the vertical second end plate, the transverse inner tube is placed in the transverse outer tube and the center lines of the two coincide, one end of the inner tube is open and the other end is closed, both ends of the outer tube are open, one end of the outer tube and the open end of the inner tube are respectively sealed and connected to a surface of one side of the first end plate, and the other end of the outer tube is sealed and connected to a surface of one side of the second end plate The surfaces are sealed and connected, and a gap is left between the closed end of the inner cylinder and the side surface of the second end plate, an annular sandwich space is formed between the circumferential outer wall of the inner cylinder and the circumferential inner wall of the outer cylinder, a grouting through hole is provided at a position corresponding to the annular sandwich space on the first end plate, and the grouting pipe of the grouting assembly is connected to the grouting through hole, a radially penetrating pressurized through hole is provided at a position close to the first end plate on the cylinder wall of the outer cylinder, and the first pressurized pipe of the first pressurized assembly is connected to the pressurized through hole, a slurry collecting through hole is provided at a position corresponding to the central area of the closed end of the inner cylinder on the second end plate, and the slurry collecting pipe of the slurry collecting assembly is connected to the slurry collecting through hole, the second pressurized pipe of the second pressurized assembly is connected to the slurry collecting barrel of the slurry collecting barrel and provides high pressure for the closed space in the slurry collecting barrel.
[0008] Preferably, in order to reliably seal the inner cylinder and the outer cylinder with the first end plate and the second end plate respectively, the two ends of the connecting rod are respectively provided with external threads, and the two ends of the four connecting rods respectively pass through the four first connecting through holes near the four corners of the first end plate and the four second connecting through holes near the four corners of the second end plate and are connected with corresponding nuts, and an inner annular groove and an outer annular groove are provided on one side surface of the first end plate, the center point of the inner annular groove coincides with the center point of the outer annular groove, the diameter of the inner annular groove is smaller than the diameter of the outer annular groove, and an inner A sealing ring, the open end of the inner cylinder is placed in the inner annular groove and the inner sealing ring is pressed, four locking screws evenly distributed in the circumferential direction respectively pass through the four locking through holes on the first end plate and the four through holes of the inner sealing ring in sequence, and are connected with the four locking screw holes on the end surface of the open end of the inner cylinder, an outer sealing ring is provided in the outer annular groove, one end of the outer cylinder is placed in the outer annular groove and the outer sealing ring is pressed, a circular groove is provided on one side surface of the second end plate, a sealing ring is provided in the circular groove, and the other end of the outer cylinder is placed in the circular groove and the sealing ring is pressed.
[0009] Preferably, the inner sealing ring, the outer sealing ring and the sealing ring are all rubber sealing rings.
[0010] Preferably, in order to facilitate intuitive observation of the flow of the slurry in the outer cylinder, the outer cylinder and the inner cylinder are both transparent organic glass cylinders, and the outer wall of the outer cylinder is provided with scale lines distributed along the axial direction.
[0011] Preferably, in order to provide a suitable grouting pressure, the grouting assembly includes a grout storage barrel, a grouting pump and the grouting pipe, the inlet of the grouting pump is connected to the grout storage barrel, and the outlet of the grouting pump is connected to the grouting through hole through the grouting pipe.
[0012] Preferably, in order to inject slurry from multiple positions in the circumferential direction to achieve a more realistic slurry simulation effect, there are four grouting holes and they are evenly distributed along the circumferential direction, and a section of the grouting pipe located between the grouting pump and the grouting holes is divided into four sections, one end of which is connected in parallel to each other and the other end is respectively connected to the four grouting holes.
[0013] Preferably, in order to prevent the slurry from settling and solidifying in the slurry storage barrel and to monitor the grouting pressure, an agitator is installed at the bottom of the slurry storage barrel and a pressure gauge is installed on the grouting pipe.
[0014] Preferably, in order to provide a stable high-pressure environment in the outer cylinder to achieve a more realistic slurry simulation effect, and to further stabilize and monitor the air pressure provided by the first pressurizing component, the first pressurizing component includes a first air compressor and the first pressurizing pipe, one end of the first pressurizing pipe is connected to the high-pressure gas outlet of the first air compressor, and the other end is connected to the pressurizing through hole, and a pressure stabilizer and the pressure gauge are installed on the first pressurizing pipe.
[0015] Preferably, in order to weigh the collected slurry in real time and better simulate the actual excavation face pressure, and to further stabilize and monitor the air pressure provided by the second pressurizing assembly, the slurry collecting assembly includes an electronic scale, the slurry collecting barrel and the slurry collecting pipe, the slurry collecting barrel is placed on the electronic scale, the slurry inlet of the slurry collecting barrel is connected to the slurry collecting through hole through the slurry collecting pipe, the second pressurizing assembly includes a second air compressor and the second pressurizing pipe, the pressure stabilizer and the pressure gauge are installed on the second pressurizing pipe, one end of the second pressurizing pipe is connected to the high-pressure gas outlet of the second air compressor, and the other end is connected to the high-pressure gas inlet at the top of the slurry collecting barrel.
[0016] The beneficial effects of the present invention are:
[0017] The present invention integrates a slurry mixing component, a grouting component, a first pressurizing component, a slurry collecting component and a second pressurizing component, uses the outer cylinder of the slurry mixing component to simulate rock formations, uses the inner cylinder of the slurry mixing component to simulate the shield shell of a shield machine, uses the annular interlayer space between the inner cylinder and the outer cylinder to simulate the slurry mixing channel, uses the grouting component to simulate the actual grouting process, uses the first pressurizing component to simulate the high pressure at the shield tail, uses the second pressurizing component to simulate the high pressure at the excavation face, uses the slurry collecting component to collect the slurry and use it to simulate the slurry flowing to the excavation face during the slurry mixing process, and finally realizes the function of simulating the real slurry mixing phenomenon that occurs under different formation pressures during the grouting process of the shield tail of the shield tunnel, and is used to explore the slurry mixing degree of different construction parameters (grouting pressure, slurry type) under different pressure conditions, which is beneficial to improving the grouting construction quality of the shield tail of the shield tunnel and avoiding safety hazards in the later operation of the tunnel. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a schematic diagram of the main structure of the shield tail grouting and slurry channeling test device for a shield tunnel under pressure conditions according to the present invention;
[0019] Figure 2 It is a three-dimensional structural schematic diagram of the grouting assembly of the shield tail grouting and grouting test device for a shield tunnel under pressure conditions according to the present invention;
[0020] Figure 3 Schematic diagram of the half-section structure of the grouting component of the shield tail grouting grouting test device for the shield tunnel under pressure conditions according to the present invention, with the viewing angle and Figure 2 same;
[0021] Figure 4 yes Figure 3 A magnified view of "A" in the figure;
[0022] Figure 5 It is a side view structural schematic diagram of the first end plate of the shield tail grouting and slurry channeling test device for a shield tunnel under pressure conditions according to the present invention;
[0023] Figure 6 It is a side structural schematic diagram of the second end plate of the shield tail grouting and slurry channeling test device for a shield tunnel under pressure conditions described in the present invention. DETAILED DESCRIPTION
[0024] The present invention will be further described below in conjunction with the accompanying drawings:
[0025] like Figure 1-Figure 6As shown, the shield tail grouting and grouting test device for the shield tunnel under pressure conditions described in the present invention includes a grouting assembly for simulating the grouting process, a grouting assembly for injecting slurry, a first pressurizing assembly for simulating the high pressure of the shield tail, a slurry collecting assembly for collecting slurry and a second pressurizing assembly for simulating the high pressure of the excavation face, the grouting assembly includes a first end plate 10, a second end plate 15, an outer tube 13, an inner tube 21 and a connecting rod 12, the two ends of a plurality of transverse connecting rods 12 are respectively fixedly connected to the vertical first end plate 10 and the vertical second end plate 15, the transverse inner tube 21 is placed in the transverse outer tube 13 and the center lines of the two coincide, one end of the inner tube 21 is open and the other end is closed, both ends of the outer tube 13 are open, one end of the outer tube 13 and the open end of the inner tube 21 are respectively sealed and connected to one side surface of the first end plate 10, the other end of the outer tube 13 is sealed and connected to one side surface of the second end plate 15 and the inner tube 21 A gap is left between the closed end 23 of the inner cylinder 21 and the side surface of the second end plate 15, and an annular interlayer space 22 is formed between the circumferential outer wall of the inner cylinder 21 and the circumferential inner wall of the outer cylinder 13. A grouting through hole 19 is provided at a position corresponding to the annular interlayer space 22 on the first end plate 10, and the grouting pipe 8 of the grouting assembly is communicated with the grouting through hole 19. A radially penetrating pressurized through hole 20 is provided on the wall of the outer cylinder 13 near the first end plate 10, and the first pressurized pipe 7 of the first pressurized assembly is communicated with the pressurized through hole 20. A slurry collecting through hole 24 is provided at a position corresponding to the central area of the closed end 23 of the inner cylinder 21 on the second end plate 15, and the slurry collecting pipe (not marked in the figure) of the slurry collecting assembly is communicated with the slurry collecting through hole 24. The second pressurized pipe (not marked in the figure) of the second pressurized assembly is communicated with the slurry collecting barrel 16 of the slurry collecting assembly and provides high pressure for the closed space in the slurry collecting barrel 16.
[0026] like Figure 1-Figure 6 As shown, the present invention also shows the following more optimized specific structures:
[0027] In order to reliably seal and connect the inner cylinder 21 and the outer cylinder 13 to the first end plate 10 and the second end plate 15 respectively, external threads are respectively provided at both ends of the connecting rod 12, and the two ends of the four connecting rods 12 respectively pass through the four first connecting through holes 27 near the four corners on the first end plate 10 and the four second connecting through holes 31 near the four corners on the second end plate 15 and are connected to the corresponding nuts 11. An inner annular groove 29 and an outer annular groove 28 are provided on one side surface of the first end plate 10, and the center point of the inner annular groove 29 coincides with the center point of the outer annular groove 28. The diameter of the inner annular groove 29 is smaller than the diameter of the outer annular groove 28. An inner sealing ring 26 is provided in the inner annular groove 29. The inner cylinder 2 The open end of the inner cylinder 1 is placed in the inner annular groove 29 and the inner sealing ring 26 is pressed, and four locking screws 9 evenly distributed in the circumferential direction respectively pass through the four locking through holes 30 on the first end plate 10 and the four through holes (not marked in the figure) of the inner sealing ring 26 in sequence, and are connected with the four locking screw holes (not marked in the figure) on the end surface of the open end of the inner cylinder 21, an outer sealing ring 25 is arranged in the outer annular groove 28, one end of the outer cylinder 13 is placed in the outer annular groove 28 and the outer sealing ring 25 is pressed, a circular groove 32 is arranged on one side surface of the second end plate 15, a sealing ring (not marked in the figure) is arranged in the circular groove 32, and the other end of the outer cylinder 13 is placed in the circular groove 32 and the sealing ring is pressed.
[0028] The inner sealing ring 26 and the outer sealing ring 25 are all rubber sealing rings.
[0029] In order to facilitate intuitive observation of the flow of the slurry in the outer cylinder 13 , the outer cylinder 13 and the inner cylinder 21 are both transparent organic glass cylinders, and the outer wall of the outer cylinder 13 is provided with scale lines 14 distributed along the axial direction.
[0030] In order to provide appropriate grouting pressure, the grouting assembly includes a grout storage barrel 1, a grouting pump 3 and a grouting pipe 8. The inlet of the grouting pump 3 is connected to the grout storage barrel 1, and the outlet of the grouting pump 3 is connected to the grouting through hole 19 through the grouting pipe 8.
[0031] In order to inject slurry from multiple positions in the circumferential direction to achieve a more realistic slurry simulation effect, there are four grouting holes 19 that are evenly distributed along the circumferential direction, and a section of the grouting pipe 8 located between the grouting pump 3 and the grouting holes 19 is divided into four lines, one end of which is connected in parallel to each other and the other end is respectively connected to the four grouting holes 19.
[0032] In order to prevent the slurry from settling and solidifying in the slurry storage barrel 1 and to monitor the grouting pressure, an agitator 2 is installed at the bottom of the slurry storage barrel 1 and a pressure gauge 6 is installed on the grouting pipe 8 (the pressure gauge 6 here and the pressure gauge 6 in the following content do not refer to the same pressure gauge 6).
[0033] In order to provide a stable high-pressure environment in the outer cylinder 13 to achieve a more realistic slurry simulation effect, and to further stabilize and monitor the air pressure provided by the first pressurizing component, the first pressurizing component includes a first air compressor 4 and a first pressurizing pipe 7. One end of the first pressurizing pipe 7 is connected to the high-pressure gas outlet of the first air compressor 4, and the other end is connected to the pressurizing through hole 20. A stabilizer 5 (the stabilizer 5 here and the stabilizer 5 in the following content do not refer to the same stabilizer 5) and a pressure gauge 6 are installed on the first pressurizing pipe 7.
[0034] In order to weigh the collected slurry in real time and better simulate the actual excavation face pressure, and to further stabilize and monitor the air pressure provided by the second pressurizing component, the slurry collecting component includes an electronic scale 17, a slurry collecting barrel 16 and the slurry collecting pipe. The slurry collecting barrel 16 is placed on the electronic scale 17. The slurry inlet of the slurry collecting barrel 16 is connected to the slurry collecting through hole 24 through the slurry collecting pipe. The second pressurizing component includes a second air compressor 18 and the second pressurizing pipe. A pressure stabilizer 5 and a pressure gauge 6 are installed on the second pressurizing pipe. One end of the second pressurizing pipe is connected to the high-pressure gas outlet of the second air compressor 18, and the other end is connected to the high-pressure gas inlet at the top of the slurry collecting barrel 16.
[0035] like Figure 1-Figure 6 As shown, during the test, according to the relevant parameters in the actual shield tail grouting process of the shield tunnel, the grouting pump 3 and the corresponding pressure gauge 6 are used to inject slurry of corresponding pressure into the annular interlayer space 22, and the first air compressor 4 and the corresponding pressure stabilizer 5 and the pressure gauge 6 are used to provide the corresponding shield tail high pressure for the rear end of the annular interlayer space 22 (i.e., the end close to the shield tail, the left end in the figure), and the second air compressor 18 and the corresponding pressure stabilizer 5 and the pressure gauge 6 are used to provide the corresponding shield tail high pressure for the front end of the annular interlayer space 22 (i.e., the end close to the excavation surface, The right end in the figure) provides a high pressure on the excavation surface of the corresponding pressure, so as to achieve the purpose of using the annular interlayer space 22 to simulate the actual environmental parameters of the slurry channel. Under the action of the pressure difference between the rear end and the front end of the annular interlayer space 22, the slurry flows from the rear end to the front end in the annular interlayer space 22, and flows into the slurry storage barrel 16 through the slurry collecting hole 24 and the slurry collecting pipe. The slurry in the slurry storage barrel 16 can be weighed in real time by the electronic scale 17, so as to achieve the purpose of measuring the weight of the slurry that spurts out of the annular interlayer space 22 under the corresponding conditions. If the slurry does not flow out of the annular interlayer space 22, the slurry slurry distance in the annular interlayer space 22 is observed and understood through the scale line 14, and the slurry slurry distance under the corresponding conditions is obtained. The above-mentioned relevant parameter conditions and the obtained slurry slurry results are used to explore the slurry slurry degree of different construction parameters (grouting pressure, slurry type) under different pressure conditions, which is beneficial to improve the shield tail grouting construction quality of the shield tunnel and avoid safety hazards in the later operation of the tunnel.
[0036] The above embodiments are only preferred embodiments of the present invention and are not limitations of the technical solutions of the present invention. Any technical solution that can be implemented on the basis of the above embodiments without creative work should be deemed to fall within the scope of protection of the patent of the present invention.
Claims
1. A shield tail grouting and slurry channeling test device for a shield tunnel under pressure conditions, characterized in that: The invention comprises a slurry-stirring assembly for simulating a slurry-stirring process, a grouting assembly for injecting slurry, a first pressurizing assembly for simulating high pressure at the shield tail, a slurry-collecting assembly for collecting slurry, and a second pressurizing assembly for simulating high pressure at the excavation face, wherein the slurry-stirring assembly comprises a first end plate, a second end plate, an outer tube, an inner tube, and a connecting rod, wherein the two ends of a plurality of transverse connecting rods are respectively fixedly connected to the vertical first end plate and the vertical second end plate, the transverse inner tube is placed in the transverse outer tube and the center lines of the two coincide, one end of the inner tube is open and the other end is closed, both ends of the outer tube are open, one end of the outer tube and the open end of the inner tube are respectively sealed to one side surface of the first end plate, the other end of the outer tube is sealed to one side surface of the second end plate, and the inner tube A gap is left between the closed end and the side surface of the second end plate, and an annular interlayer space is formed between the circumferential outer wall of the inner cylinder and the circumferential inner wall of the outer cylinder; a grouting through hole is provided at a position corresponding to the annular interlayer space on the first end plate, and the grouting pipe of the grouting assembly is communicated with the grouting through hole; a radially penetrating pressurized through hole is provided at a position close to the first end plate on the cylinder wall of the outer cylinder, and the first pressurized pipe of the first pressurized assembly is communicated with the pressurized through hole; a slurry collecting through hole is provided at a position corresponding to the central area of the closed end of the inner cylinder on the second end plate, and the slurry collecting pipe of the slurry collecting assembly is communicated with the slurry collecting through hole; the second pressurized pipe of the second pressurized assembly is communicated with the slurry collecting barrel of the slurry collecting assembly and provides high pressure for the closed space in the slurry collecting barrel.
2. The shield tail grouting and slurry channeling test device for shield tunnel under pressure conditions according to claim 1 is characterized in that: The two ends of the connecting rod are respectively provided with external threads, and the two ends of the four connecting rods respectively pass through the four first connecting through holes near the four corners of the first end plate and the four second connecting through holes near the four corners of the second end plate and are connected to the corresponding nuts. An inner circular annular groove and an outer circular annular groove are provided on one side surface of the first end plate, and the center point of the inner circular annular groove coincides with the center point of the outer circular annular groove. The diameter of the inner circular annular groove is smaller than the diameter of the outer circular annular groove. An inner sealing ring is provided in the inner circular annular groove, and the opening end of the inner cylinder is placed on the inner circular annular groove. The inner sealing ring is pressed in the annular groove, and four locking screws evenly distributed in the circumferential direction respectively pass through the four locking through holes on the first end plate and the four through holes of the inner sealing ring and are connected with the four locking screw holes on the end surface of the open end of the inner cylinder. An outer sealing ring is arranged in the outer annular groove, and one end of the outer cylinder is placed in the outer annular groove and presses the outer sealing ring. A circular groove is arranged on one side surface of the second end plate, and a sealing ring is arranged in the circular groove, and the other end of the outer cylinder is placed in the circular groove and presses the sealing ring.
3. The shield tail grouting and slurry channeling test device for shield tunnel under pressure conditions according to claim 2 is characterized in that: The inner sealing ring, the outer sealing ring and the sealing ring are all rubber sealing rings.
4. The shield tail grouting and slurry channeling test device for a shield tunnel under pressure conditions according to any one of claims 1 to 3, characterized in that: The outer cylinder and the inner cylinder are both transparent organic glass cylinders, and the outer wall of the outer cylinder is provided with scale lines distributed along the axial direction.
5. The shield tail grouting and slurry channeling test device for a shield tunnel under pressure conditions according to any one of claims 1 to 3, characterized in that: The grouting assembly comprises a grout storage barrel, a grouting pump and the grouting pipe. The inlet of the grouting pump is connected to the grout storage barrel, and the outlet of the grouting pump is connected to the grouting through hole through the grouting pipe.
6. The shield tail grouting and slurry channeling test device for a shield tunnel under pressure conditions according to claim 5 is characterized in that: There are four grouting through holes which are evenly distributed along the circumferential direction; a section of the grouting pipe located between the grouting pump and the grouting through holes is divided into four sections, one end of which is connected in parallel to each other and the other end is respectively connected to the four grouting through holes.
7. The shield tail grouting and slurry channeling test device for shield tunnel under pressure conditions according to claim 5 is characterized by: A stirrer is installed at the bottom of the slurry storage barrel, and a pressure gauge is installed on the grouting pipe.
8. The shield tail grouting and slurry channeling test device for a shield tunnel under pressure conditions according to any one of claims 1 to 3, characterized in that: The first pressurizing component includes a first air compressor and the first pressurizing pipe, one end of the first pressurizing pipe is connected to the high-pressure gas outlet of the first air compressor, and the other end is connected to the pressurizing through hole, and a pressure stabilizer and the pressure gauge are installed on the first pressurizing pipe.
9. The shield tail grouting and slurry channeling test device for a shield tunnel under pressure conditions according to any one of claims 1 to 3, characterized in that: The slurry collecting component includes an electronic scale, the slurry collecting barrel and the slurry collecting pipe. The slurry collecting barrel is placed on the electronic scale. The slurry inlet of the slurry collecting barrel is connected to the slurry collecting through hole through the slurry collecting pipe. The second pressurizing component includes a second air compressor and the second pressurizing pipe. The second pressurizing pipe is equipped with the regulator and the pressure gauge. One end of the second pressurizing pipe is connected to the high-pressure gas outlet of the second air compressor, and the other end is connected to the high-pressure gas inlet at the top of the slurry collecting barrel.