A method for testing the grouting effect of post-cast layer concrete of a second lining arch of a semi-precast tunnel
By conducting full-scale section tests at the arch foot, arch shoulder, and arch crown of the secondary lining arch ring of the semi-prefabricated tunnel, and using steel arch frames and closed steel molds for concrete pouring and setting up vent overflow ports, the problem of difficulty in evaluating the post-cast layer pouring effect in the existing technology was solved, and low-cost repeated tests and concrete mix optimization were achieved.
Patent Information
- Application Number
- CN202611198974.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-08
- Publication Date
- 2026-11-06
AI Technical Summary
Existing technologies make it difficult to accurately evaluate the casting effect of the post-cast layer of the secondary lining arch ring of a semi-prefabricated tunnel at key locations such as the arch foot, arch shoulder, and arch crown without conducting a full-ring grouting test. Furthermore, repeated tests are costly and difficult.
Full-scale section tests were conducted using steel arch frames and enclosed steel molds. Concrete pouring ports and vent overflow ports were set at the arch foot, arch shoulder, and arch crown. Data on the pouring process were recorded, and the concrete mix design was evaluated to determine whether it met the construction requirements, in conjunction with the inspection of the specimens after pouring.
It achieves a true reflection of the post-cast concrete pouring effect at low cost, facilitates repeated tests, optimizes concrete mix proportions, and reduces test costs and difficulty.
Smart Images
Figure CN123046368A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of highway tunnel construction technology, and relates to a construction method for a semi-prefabricated tunnel secondary lining arch ring, specifically a test method for the concrete pouring effect of the post-cast layer of the semi-prefabricated tunnel secondary lining arch ring. Background Technology
[0002] Patent CN221779439U discloses a semi-prefabricated highway tunnel lining arch ring, comprising a prefabricated layer and a post-cast layer. The prefabricated layer is constructed by assembling multiple prefabricated components into a prefabricated arch ring inside the tunnel. A certain gap is maintained between the prefabricated arch ring and the tunnel wall during assembly. After assembly, concrete is poured between the prefabricated arch ring and the tunnel wall to form the post-cast layer. The prefabricated layer and the post-cast layer together form the load-bearing system of the tunnel secondary lining arch ring.
[0003] The concrete mix design of post-cast layers is crucial to their construction quality. Currently, post-cast layer concrete mix designs often refer to the specifications of ordinary self-compacting concrete or pumped concrete, primarily focusing on slump spread, strength, and plasticity retention. However, post-cast layers are characterized by their thinness, dense reinforcement, inability to be vibrated, susceptibility to air accumulation at the arch crown, and coarse aggregate content. Furthermore, the spatial orientation, gravity direction, air venting conditions, and injection difficulty of the concrete differ at the arch foot, abutment, and crown. Since post-cast layers are poured in a closed space, conventional indicators alone are insufficient to determine whether the concrete has achieved adequate compaction in the back wall environment. Therefore, it is necessary to conduct pre-construction tests to determine the optimal concrete mix design. While using a full-scale casting test model of the entire arch ring can effectively reflect real-world conditions, the testing is costly and time-consuming. Moreover, the large size of the specimens makes disassembly and inspection difficult, hindering repeated testing. Therefore, it is unsuitable for verifying and optimizing various concrete mix designs. Summary of the Invention
[0004] The purpose of this invention is to address the above-mentioned problems by providing a test method for the concrete pouring effect of the post-cast layer of the secondary lining arch ring in semi-prefabricated tunnels. Without conducting a full-ring pouring test, this method can accurately reflect the pouring effect of the post-cast layer at key locations such as the arch foot, arch shoulder, and arch crown at a lower cost. It also facilitates repeated tests and allows for optimization of the concrete mix ratio of the post-cast layer.
[0005] The technical solution of the present invention is as follows:
[0006] A test method for evaluating the pouring effect of post-cast concrete in the secondary lining arch of a semi-prefabricated tunnel, characterized by the following steps:
[0007] (1) A steel arch frame and three closed steel molds are prefabricated; the steel arch frame is made according to the full cross-sectional dimensions of the inner ring of the tunnel arch; the closed steel mold is a box-shaped structure with a cover plate installed on the top. The internal planar dimensions of the steel mold are the same as the planar dimensions of a tunnel secondary lining prefabricated component, and the internal height of the steel mold is the same as the thickness of the tunnel secondary lining arch.
[0008] (2) Place three steel molds at the arch foot, arch shoulder and arch top of the arch frame respectively. Place a secondary lining precast component in each steel mold. Tie the secondary lining post-cast reinforcement to the top of each precast component. Fix the steel mold to the arch frame with screws. The screws pass through the steel mold and the precast component inside the steel mold. The lower end of the screw is anchored to the bottom of the steel arch frame by a nut. The upper end is anchored to the steel mold cover plate. Press the cover plate tightly. The space between the top of the precast component and the cover plate is the space for pouring the post-cast concrete.
[0009] Each steel mold is equipped with a concrete pouring port and an vent overflow port. For the steel mold located at the arch foot, the concrete pouring port is located at the lower end of the steel mold, and the vent overflow port is located at the upper end. This is used to verify the ability of concrete to be poured from a low position, filled at the bottom, and initially wrapped around the reinforcing bars. For the steel mold located in the arch shoulder area, the concrete pouring port is located on the downward-sloping side of the steel mold, and the vent overflow port is located on the upward-sloping side. This is used to verify the ability of concrete to flow upwards at an angle and to wrap around the dense reinforcing bars. For the steel mold in the arch crown area, the concrete pouring port is located at both ends of the steel mold, and the vent overflow port is located at the arch crown. This is used to verify the removal of stagnant air at the arch crown and secondary pressurization.
[0010] (3) Pour concrete with the desired mix ratio into each steel mold through the concrete pouring port, and record the pouring port pressure, instantaneous flow rate, cumulative injection volume, number of pressure surges, exhaust time of the exhaust port, and overflow discharge time. After pouring, stabilize the pressure for 5 minutes. If the pressure decrease is not greater than 20% and the ratio of stone content in the overflow material to stone content in the inlet material is not less than 0.70, then proceed to the specimen curing stage.
[0011] (4) After curing, remove the steel mold, take out the concrete specimen inside the steel mold, check the concrete void area ratio on the surface of the specimen, and set up a section inspection surface along the back, middle and end of the reinforcement of the post-cast layer of the specimen to check the reinforcement wrapping and internal voids. Combine the data recorded during the pouring process to comprehensively evaluate whether the concrete mix ratio meets the actual construction requirements.
[0012] This invention, through full-scale section tests on the arch foot, shoulder, and crown of the secondary lining arch of a semi-prefabricated tunnel, can obtain real test data and pouring effects on key parts such as the low-position pouring of concrete at the arch foot, the upward slope of the arch shoulder, and the air stagnation at the crown, without using a full-ring full-scale model. This reduces test costs. Moreover, the steel mold is small in size, easy to assemble and disassemble, and facilitates repeated tests, which is beneficial for the selection of various concrete mix proportions and the optimization of pouring processes. Attached Figure Description
[0013] Figure 1 This is a side view of the experimental device of the present invention. Detailed Implementation
[0014] The specific construction method of this invention is as follows:
[0015] (1) such as Figure 1 As shown, a steel arch frame 1 and three closed steel molds 2 are prefabricated; the steel arch frame is made according to the full cross-sectional dimensions of the inner ring of the tunnel arch; the closed steel mold is a box-shaped structure with a cover plate movably installed on the top, the internal planar dimensions of the steel mold are the same as the planar dimensions of a tunnel secondary lining precast component, and the internal height of the steel mold is the same as the thickness of the tunnel secondary lining arch.
[0016] (2) Place three steel molds 2 at the arch foot 11, arch shoulder 12 and arch top 13 of the arch frame respectively. Place a secondary lining precast component 3 in each steel mold. The top of each precast component is pre-tied with the secondary lining post-cast reinforcement. Fix the steel mold to the arch frame with screws 4. The screws pass through the steel mold and the precast component inside the steel mold. The lower end of the screw is anchored to the bottom of the steel arch frame by a nut, and the upper end is anchored to the steel mold cover plate. Press the cover plate tightly. The space between the top of the precast component and the cover plate is the space for pouring the post-cast concrete.
[0017] For steel molds installed at the arch shoulder, a support plate 5 can be welded to the bottom of the steel mold on the arch frame to support the steel mold.
[0018] The precast secondary lining components placed in the steel formwork are the same precast components actually used in the construction of the semi-precast tunnel secondary lining, with a longitudinal length of 0.8m to 2.5m and a circumferential arc length of 0.8m to 3.0m. The diameter, spacing, protective layer thickness, and binding method of the post-cast reinforcement are consistent with the corresponding parts of the post-cast secondary lining of the actual semi-precast tunnel.
[0019] Each steel mold is equipped with a concrete pouring port and an vent overflow port. For the steel mold located at the arch foot, the concrete pouring port is located at the lower end of the steel mold, and the vent overflow port is located at the upper end, to verify the ability of concrete to be poured from a low position, filled at the bottom, and initially wrapped around the reinforcing bars. For the steel mold located in the arch shoulder area, the concrete pouring port is located on the downward-sloping side of the steel mold, and the vent overflow port is located on the upward-sloping side, to verify the ability of concrete to flow upwards at an angle and around the dense reinforcing bars. For the steel mold in the arch crown area, the concrete pouring port is located at both ends of the steel mold, and the vent overflow port is located at the arch crown, to verify the removal of stagnant air at the arch crown and secondary pressurization.
[0020] (3) Concrete with the desired mix proportions was poured into each steel mold through the concrete pouring port.
[0021] In a specific embodiment of the present invention, the mix design targets for the post-cast concrete include a slump spread of 560mm to 700mm, a T500 flow time of 5s to 12s, a slump spread loss of no more than 80mm within 90 minutes, a pressure bleeding rate of no more than 2.0%, a static segregation rate of no more than 10%, and a 28-day compressive strength of no less than the design strength grade. The concrete contains coarse aggregate with a maximum particle size of no more than 20mm, preferably a continuous gradation of 5mm to 16mm or a two-gradation combination of 5mm to 10mm and 10mm to 16mm. The amount of cementitious material is 420kg / m³ to 540kg / m³, the water-cement ratio is 0.32 to 0.40, the sand ratio is 44% to 56%, and at least one of polycarboxylate superplasticizer, plasticizing component, viscosity modifier, expansion component, or shrinkage reduction component is incorporated.
[0022] During concrete pouring, the following parameters are recorded: inlet pressure, instantaneous flow rate, cumulative injection volume, number of pressure spikes, venting time at the vent overflow port, overflow discharge time, and pressure stabilization time. When the vent overflow port changes from continuous venting to the discharge of uniform slurry, mortar, or concrete containing coarse aggregate, and responds to pressure changes at the inlet during the pressure stabilization phase, the corresponding location is considered to have been effectively reached by the subsequently poured concrete. After pouring, the pressure is stabilized for 5 minutes. If the pressure decrease is no more than 20%, and the ratio of aggregate content in the overflow material to that inlet material is no less than 0.70, the specimen curing stage begins.
[0023] (4) After curing, remove the steel mold, take out the concrete specimen inside the steel mold, check the concrete void area ratio on the surface of the specimen, and set up a section inspection surface along the back, middle and end of the reinforcement of the post-cast layer of the specimen to check the reinforcement wrapping and internal voids. Combine the data recorded during the pouring process to comprehensively evaluate whether the concrete mix ratio meets the actual construction requirements.
[0024] The criteria for judging the quality of injection molding include: the surface void area ratio after demolding is not greater than 2.0%, the unfilled area ratio behind the reinforcing bars is not greater than 3.0%, the length of continuous voids in the arch is not greater than 100mm, the pressure decay after 5 minutes of stabilization is not greater than 20%, and the ratio of stone content in overflow material to stone content in inlet material is not less than 0.70.
[0025] Using the above method, repeated tests were conducted on concrete with various mix proportions to optimize and select the mix proportion of the post-cast concrete.
Claims
1. A test method for the pouring effect of post-cast concrete in the secondary lining arch of a semi-prefabricated tunnel, characterized in that, Includes the following steps: (1) A steel arch frame and three closed steel molds are prefabricated; the steel arch frame is made according to the full cross-sectional dimensions of the inner ring of the tunnel arch; the closed steel mold is a box-shaped structure with a cover plate installed on the top. The internal planar dimensions of the steel mold are the same as the planar dimensions of a tunnel secondary lining prefabricated component, and the internal height of the steel mold is the same as the thickness of the tunnel secondary lining arch. (2) Place three steel molds at the arch foot, arch shoulder and arch top of the arch frame respectively. Place a secondary lining precast component in each steel mold. Tie the secondary lining post-cast reinforcement to the top of each precast component. Fix the steel mold to the arch frame with screws. The screws pass through the steel mold and the precast component inside the steel mold. The lower end of the screw is anchored to the bottom of the steel arch frame by a nut. The upper end is anchored to the steel mold cover plate. Press the cover plate tightly. The space between the top of the precast component and the cover plate is the space for pouring the post-cast concrete. Each steel mold is equipped with a concrete pouring port and an vent overflow port. For the steel mold located at the arch foot, the concrete pouring port is located at the lower end of the steel mold, and the vent overflow port is located at the upper end. This is used to verify the ability of concrete to be poured from a low position, filled at the bottom, and initially wrapped around the reinforcing bars. For the steel mold located in the arch shoulder area, the concrete pouring port is located on the downward-sloping side of the steel mold, and the vent overflow port is located on the upward-sloping side. This is used to verify the ability of concrete to flow upwards at an angle and to wrap around the dense reinforcing bars. For the steel mold in the arch crown area, the concrete pouring port is located at both ends of the steel mold, and the vent overflow port is located at the arch crown. This is used to verify the removal of stagnant air at the arch crown and secondary pressurization. (3) Pour concrete with the desired mix ratio into each steel mold through the concrete pouring port, and record the pouring port pressure, instantaneous flow rate, cumulative injection volume, number of pressure surges, exhaust time of the exhaust port, and overflow discharge time. After pouring, stabilize the pressure for 5 minutes. If the pressure decrease is not greater than 20% and the ratio of stone content in the overflow material to stone content in the inlet material is not less than 0.70, then proceed to the specimen curing stage. (4) After curing, remove the steel mold, take out the concrete specimen inside the steel mold, check the concrete void area ratio on the surface of the specimen, and set up a section inspection surface along the back, middle and end of the reinforcement of the post-cast layer of the specimen to check the reinforcement wrapping and internal voids. Combine the data recorded during the pouring process to comprehensively evaluate whether the concrete mix ratio meets the actual construction requirements.