Layered casting of unreinforced hybrid steel fiber concrete shield segment and manufacturing method thereof

Abstract

The present invention discloses a layered cast unreinforced hybrid steel fiber concrete shield segment, the shield segment is an arc-shaped structure, and includes: a first steel fiber concrete layer and a second steel fiber concrete layer from the inner arc surface to the outer arc surface of the shield segment; the raw materials of the first steel fiber concrete layer include: long steel fiber, short steel fiber, cement, water reducer, coarse aggregate, fine aggregate and fly ash; the raw materials of the second steel fiber concrete layer include: short steel fiber, cement, water reducer, coarse aggregate, fine aggregate and fly ash. The steel fiber concrete shield segment of the present invention has two layers of steel fiber concrete, one layer is a long + short steel fiber concrete layer, and the other layer is a short steel fiber concrete layer. Long and short steel fibers are mixed, and short steel fibers have a reinforcing effect on the concrete matrix, mainly suppressing the occurrence of cracks in the early stage, and long steel fibers mainly delay the expansion of cracks in the later stage, transmit and bear the shear force at the cracks, and the early and later effects are different, and the advantages are complementary.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, and in particular to a layered casting unreinforced hybrid steel fiber concrete shield segment and a manufacturing method thereof. Background Art

[0002] In recent years, with the continuous advancement of urbanization and the continuous development of urban scale, major cities in China have begun to develop subways and urban underground spaces. Among them, shield construction technology is a construction method that has been widely used in underground tunnel construction. The shield segment is the main assembly component of the shield construction and is the innermost barrier of the tunnel. It is responsible for resisting soil pressure, groundwater pressure and some special loads.

[0003] As the main body of the tunnel structure, prefabricated shield segments are directly related to the overall quality of the tunnel, affecting the tunnel's bearing capacity, waterproof performance and durability. At present, domestic prefabricated shield segments are basically reinforced concrete segments, but reinforced concrete shield segments also have many disadvantages:

[0004] (1) Production and transportation: The steel bar processing procedure is cumbersome, time-consuming and labor-intensive, and has low production efficiency. During transportation, it is inevitable that there will be accumulation and extrusion, and stress concentration will occur at the contact parts, which will eventually lead to the edge of the pipe segment being prone to corner chipping, edge falling, and edge damage.

[0005] (2) Construction and installation: During the construction process, jacks are often used to push the pipe forward. Under the action of the jacking load, a large splitting torque will be generated, which will cause cracks to form on the surface of the pipe segment. Moisture will enter the interior of the pipe segment, causing the steel bars to rust, reducing the main strength and durability of the pipe segment.

[0006] (3) Lining joints: The joints are the weakest parts of the segments. Structural damage usually starts at the joints, especially when the deviatoric force acts on the annular seam surface of the segment, which is more likely to cause the segment to be crushed and cracked.

[0007] (4) Waterproofness: “Nine out of ten tunnels leak” indicates that leakage is a common hazard in tunnels. Damage and water seepage in the pipe segments not only increase the cost of subsequent maintenance, but also seriously affect the service life and operational safety of the tunnel.

[0008] Based on the above shortcomings, some people have invented pure steel fiber concrete shield segments without steel bars, and various performances have been confirmed in research tests. However, due to the uncertainty of steel fiber distribution, they may gather in the compression zone, while the sparse distribution in the tension zone causes the steel fibers to be unable to play a tensile role. The tensile properties of the steel fibers cannot be fully utilized, which will cause uncertain risks to the segments.

[0009] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0010] The purpose of the present invention is to provide a layered cast unreinforced mixed steel fiber concrete shield segment, so as to overcome the shortcomings of existing shield segments, such as high brittleness and low toughness, easy to break during transportation, easy to form cracks in the segments, and water seepage, which affects the service life and operation safety of the tunnel.

[0011] Another object of the present invention is to provide a method for manufacturing layered casting of unreinforced hybrid steel fiber concrete shield segments to improve work efficiency.

[0012] To achieve the above-mentioned purpose, the present invention provides a layered cast unreinforced hybrid steel fiber concrete shield segment, wherein the shield segment has an arc-shaped structure, and comprises, from the inner arc surface to the outer arc surface of the shield segment, a first steel fiber concrete layer and a second steel fiber concrete layer in sequence; the raw materials of the first steel fiber concrete layer include: long steel fibers, short steel fibers, cement, a water reducer, coarse aggregate, fine aggregate and fly ash; the raw materials of the second steel fiber concrete layer include: short steel fibers, cement, a water reducer, coarse aggregate, fine aggregate and fly ash.

[0013] Preferably, in the above technical solution, the amount of long steel fibers added to the first steel fiber concrete layer is 20-50 kg / m 3 The amount of short steel fiber added is 3-15kg / m 3 .

[0014] Preferably, in the above technical solution, the amount of short steel fibers added to the second steel fiber concrete layer is 20-50 kg / m 3 .

[0015] Preferably, in the above technical solution, the first steel fiber concrete layer and / or the second steel fiber concrete layer comprises: cement 300-600kg / m 3 , water reducing agent 5-10kg / m 3 , coarse crushed stone 800-1300kg / m 3 , fine aggregate 500-1200kg / m 3 , fly ash 60-100kg / m 3 .

[0016] Preferably, in the above technical solution, the long steel fiber is one or more of a milling type, a shearing type or an end hook type; and / or the short steel fiber is a straight steel fiber.

[0017] Preferably, in the above technical solution, the long steel fiber has a length of 40-60 mm and an aspect ratio of 60-80; and / or the short steel fiber has a length of 5-15 mm and an aspect ratio of 60-80.

[0018] Preferably, in the above technical solution, the coarse aggregate includes 5-10 mm crushed stone and 10-20 mm crushed stone, and the mixing mass ratio is 5-8:2-5.

[0019] Preferably, in the above technical solution, the fine aggregate is medium-coarse river sand with a fineness modulus of 2.3-3.0.

[0020] A method for manufacturing a layered casting unreinforced hybrid steel fiber concrete shield segment comprises the following steps:

[0021] (1) Mold preparation: first assemble the mold, clean the mold surface, apply the release agent, and then adjust the mold;

[0022] (2) Material preparation: taking long steel fibers, short steel fibers, cement, water reducing agent, coarse aggregate, fine aggregate, and fly ash according to weight ratio, mixing the coarse aggregate, fine aggregate, and cement, and then adding the long steel fibers and short steel fibers, and mixing them, and then adding water, and mixing them, to obtain a first steel fiber concrete; mixing the coarse aggregate, fine aggregate, and cement, and then adding the short steel fibers, and then mixing them, and then adding water, and mixing them, to obtain a second steel fiber concrete;

[0023] (3) Casting: Cast the first steel concrete layer first, vibrate and compact it, cast the second steel concrete layer before initial setting, and vibrate and compact it again;

[0024] (4) Steam curing and demoulding: After the concrete is poured, let it stand, then introduce steam for curing, and then demould;

[0025] (5) Inspection and maintenance.

[0026] Preferably, in the above technical solution, after the pouring of step (4) is completed, the concrete is allowed to stand for 1-3 hours, and the steam curing time is not less than 5 hours. After the steam curing is cooled down, the concrete strength reaches more than 15 MPa, and then demoulding is performed;

[0027] The curing of step (5) is to place the prepared shield segment in a curing pool for 5-10 days.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention casts the unreinforced hybrid steel fiber concrete shield segment in layers, and has two layers of steel fiber concrete, one of which is a long + short steel fiber concrete layer, and the other is a short steel fiber concrete layer. The long and short steel fibers are mixed, and the short steel fibers have a reinforcing effect on the concrete matrix, mainly suppressing the appearance of cracks in the early stage, and the long steel fibers mainly delay the expansion of cracks in the later stage, transmitting and bearing the shear force at the cracks. The early and late effects are different, and the advantages complement each other and are perfectly combined.

[0030] (2) The mixture of long and short steel fibers can improve the initial crack load, initial crack bending moment and post-crack bearing capacity of concrete, give full play to their respective strengths under different stress conditions, reduce the number and width of concrete cracks, thereby improving the corrosion resistance of the pipe segment and extending the life of the tunnel. Short steel fibers have a reinforcing effect on the concrete matrix and inhibit the appearance of cracks; long steel fibers delay the expansion of cracks, transmit and bear the shear force at the cracks.

[0031] (3) Layered concrete pouring: pour long steel fiber + short steel fiber concrete at the bottom of the segment. The bottom of the segment mainly bears tension. Short steel fiber + long steel fiber can increase the matrix strength and withstand tension. Pour short steel fiber concrete at the top of the segment. The top of the segment mainly bears pressure. Short steel fiber can improve the matrix strength. Layered pouring of steel fiber concrete, according to the stress performance of the segment, centralized arrangement of long and short steel fibers, greatly exerts the performance of long and short steel fibers, improves economic benefits, and reduces the cost of the segment.

[0032] (4) The manufacturing method of the layered casting of unreinforced hybrid steel fiber concrete shield segments of the present invention greatly saves the cost of steel bar binding and labor, improves work efficiency, can solve the problems of complicated production process, high brittleness and low toughness, easy breakage during transportation, etc., reduces the breakage rate during transportation, and has significant engineering, economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a manufacturing flow chart of layered casting of unreinforced hybrid steel fiber concrete shield segments according to the present invention;

[0034] Figure 2 It is a front view of a layered cast unreinforced hybrid steel fiber concrete shield segment according to the present invention;

[0035] Figure 3 yes Figure 2 Sectional view at AA in the middle;

[0036] Figure 4 is a bottom view of a layered cast unreinforced hybrid steel fiber concrete shield segment according to the present invention;

[0037] Figure 5It is a schematic diagram of the structure of long steel fibers in the layered casting of unreinforced hybrid steel fiber concrete shield segments according to the present invention;

[0038] Figure 6 It is a schematic diagram of the structure of short steel fibers in the layered casting of unreinforced hybrid steel fiber concrete shield segments according to the present invention. DETAILED DESCRIPTION

[0039] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0040] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0041] like Figures 1 to 6 As shown, according to a specific embodiment of the present invention, a layered cast unreinforced hybrid steel fiber concrete shield segment is provided, wherein the shield segment is an arc-shaped structure, and includes a first steel fiber concrete layer 1 and a second steel fiber concrete layer 2 in sequence from the inner arc surface to the outer arc surface of the shield segment.

[0042] Example 1

[0043] The inner arc surface and the outer arc surface of the shield segment of the present invention sequentially include a first steel fiber concrete layer 1 and a second steel fiber concrete layer 2. The raw materials of the first steel fiber concrete layer 1 include: long steel fiber 3, short steel fiber 4, cement, water reducer, coarse aggregate, fine aggregate and fly ash. The first steel fiber concrete layer is a CF50 long + short steel fiber concrete layer, and the specific raw material ratio of the concrete is as follows: P·O42.5 ordinary Portland cement, the dosage is 400kg / m 3 ; Drinkable or natural water, dosage 95kg / m 3 ; Polycarboxylic acid-based high-efficiency water reducer, dosage 7.65kg / m 3 The coarse aggregate is 5-20 mm crushed stone with good and continuous grading. The mixing mass ratio of 5-10 mm crushed stone to 10-20 mm is 7:3. The total amount of coarse aggregate is 1080 kg / m 3 ; The fine aggregate is medium-coarse river sand, with a fineness modulus of about 2.8 and a dosage of 800kg / m 3 ; Fly ash, dosage 80kg / m 3 ; Long steel fiber, dosage 30kg / m 3 , short steel fiber, dosage 6kg / m 3 , a total of 36kg / m 3The long and short steel fibers are mixed. The long steel fibers are one or more of the milling type, shearing type or end hook type; and / or the short steel fibers are straight steel fibers. The long steel fibers of this embodiment are end hook type steel fibers (such as Figure 5 As shown), the length is 40 to 60 mm, and the aspect ratio is 70; the short steel fiber is a straight steel fiber (as shown Figure 6 As shown), the length is 10 mm and the aspect ratio is 70.

[0044] The raw materials of the second steel fiber concrete layer 2 include: short steel fiber, cement, water reducing agent, coarse aggregate, fine aggregate and fly ash. The second steel fiber concrete layer is a CF50 short steel fiber concrete layer, and the specific raw material ratio of concrete is as follows: P·O42.5 ordinary silicate cement, with a dosage of 400kg / m 3 ; Drinkable or natural water, dosage 95kg / m 3 ; Polycarboxylic acid-based high-efficiency water reducer, dosage 7.65kg / m 3 The coarse aggregate is 5-20 mm crushed stone with good and continuous grading. The mixing mass ratio of 5-10 mm crushed stone to 10-20 mm is 7:3. The total amount of coarse aggregate is 1080 kg / m 3 ; The fine aggregate is medium-coarse river sand, with a fineness modulus of about 2.8 and a dosage of 800kg / m 3 ; Fly ash, dosage 80kg / m 3 ; Short steel fiber, dosage 30kg / m 3 , short steel fibers are straight steel fibers (such as Figure 6 As shown), the length is 10 mm and the aspect ratio is 70.

[0045] A method for manufacturing a layered casting unreinforced hybrid steel fiber concrete shield segment comprises the following steps:

[0046] (1) Mold preparation

[0047] ① Mold assembly: First, clean the inside and then the outside, then the middle and then the surrounding areas. Use a clean rag to thoroughly clean the concrete residue and other debris attached to the inner surface of the mold. Special tools must be used to clean the scale in the key parts such as the lifting hole seat and the hand hole seat. Finally, use compressed air to blow away the residue on the inner and outer surfaces of the mold.

[0048] ② Mould adjustment: professional mould inspection personnel shall measure the width, curvature and hand hole position. After the mould is put into production, the width and diagonal of the product must be measured every day.

[0049] (2) Preparation of materials

[0050] ① Prepare the raw materials for the first steel fiber concrete layer, and take long steel fiber, short steel fiber, cement, water reducing agent, coarse aggregate, fine aggregate and fly ash according to the above weight ratio;

[0051] ② Prepare the raw materials for the second steel fiber concrete layer, and take short steel fibers, cement, water reducing agent, coarse aggregate, fine aggregate, and fly ash according to the above weight ratio;

[0052] ③ Mixing: First, add the coarse and fine aggregates and cement into the concrete mixer in turn and stir for 2 minutes. Then, add the steel fiber in three times, stirring for 1 minute each time. After the steel fiber and aggregate are fully mixed, add water and stir for about 2 minutes. During the whole process, the concrete raw materials are fully stirred to ensure that each component is stirred evenly and the concrete has no bleeding and segregation. The first steel fiber concrete and the second steel fiber concrete are respectively obtained.

[0053] (3) Casting

[0054] After mixing, immediately put the steel fiber concrete into the steel mold, first pour the lower layer of CF50 long + short steel fiber concrete, and vibrate it to make it dense. Pour the upper layer of CF50 short steel fiber concrete before initial setting, use a special concrete vibration table to vibrate and shape, scrape off the excess concrete on the mold, and smooth the surface of the concrete specimen.

[0055] (4) Steam curing and demoulding

[0056] After the concrete is poured, let it stand for 2 hours, cover it with a curing cover, and introduce saturated steam for curing. Steam curing lasts for 6 hours. During the curing process, prevent the temperature from rising too fast, causing the concrete to expand and damage the internal structure. After the specified steam curing time is reached, close the air supply valve, open part of the canvas cover, let the mold and concrete cool naturally, and then completely remove the canvas cover. After cooling, send the concrete test block to the laboratory for pressure testing. When the strength reaches more than 15MPa, it can be demolded and the pipe segment can be hoisted onto a flatbed truck using a special hoist.

[0057] (5) Inspection

[0058] Inspection includes dimension inspection, appearance finishing, and record marking. Specifically:

[0059] ① Finished product size inspection: Use a vernier caliper with a range larger than the segment width to measure the segment width, and use a vernier caliper with a range larger than the thickness to measure the segment thickness. Each segment undergoes an appearance quality inspection. The segment surface should be smooth and flat, without honeycombs, exposed reinforcement, cracks, or missing corners. Minor defects should be modified, and no defects are allowed near the water stop. Grouting holes should be complete and free of cement slurry and other debris.

[0060] ② Appearance finishing: fill the bubbles, blister holes and shrinkage cracks on the surface with adhesive, water, and then add appropriate amount of cement and sand, and grind the surface to achieve a smooth and flat surface.

[0061] ③Qualified segment identification, identification content: product model, cumulative production number of product model, and product production date. Identification location: upper right corner of the inner arc surface, facing the upper right side end face of the inner arc surface.

[0062] (6) Water pond maintenance

[0063] After the hardness of the shield segment reaches 60% of the specified compressive strength, it is demoulded and then moved into the curing pool to avoid shrinkage cracks on the segment surface due to excessive temperature difference. The water temperature, the temperature of the segment before being put into water, and the first-level water curing time must be recorded for pool curing. The segment is cured in the curing pool for 7 days.

[0064] (7) Stacking in the storage yard

[0065] Use a forklift to transport it to the stacking yard. The stacking site should be solid and flat. When stacking, the segments should be stacked neatly and steadily with the inner arc surface facing upward. Flexible materials should be placed under and between the segments. The pads should be placed symmetrically to prevent collisions between the segments. The stacking height should not exceed four layers. The segments can only be shipped out of the factory when their strength reaches 100% of the design strength.

[0066] Example 2

[0067] The preparation method of the shield segment of this embodiment is basically the same as that of Example 1. The difference between this embodiment and Example 1 is that the raw materials for preparing the shield segment are different. The shield segment includes a first steel fiber concrete layer 1 and a second steel fiber concrete layer 2. The raw materials of the first steel fiber concrete layer 1 include: long steel fiber, short steel fiber, cement, water reducer, coarse aggregate, fine aggregate and fly ash. The first steel fiber concrete layer is a CF50 long + short steel fiber concrete layer, and the specific raw material ratio of the concrete is as follows: P·O42.5 ordinary Portland cement, with an admixture of 600kg / m 3 ; Drinkable or natural water, dosage 95kg / m 3 ; Polycarboxylic acid-based high-efficiency water reducer, dosage 10kg / m 3 The coarse aggregate is 5-20mm crushed stone with good and continuous grading. The mixing mass ratio of 5-10mm crushed stone to 10-20mm is 5:5. The total amount of coarse aggregate is 800kg / m 3 ; The fine aggregate is medium-coarse river sand, with a fineness modulus of about 3.0 and a dosage of 1200kg / m 3 ; Fly ash, dosage 60kg / m 3 ; Long steel fiber, dosage 20kg / m 3 , short steel fiber, dosage 15kg / m 3 , a total of 35kg / m 3 The long and short steel fibers are mixed. The long steel fibers are one or more of the milling type, shearing type or end hook type; and / or the short steel fibers are straight steel fibers. The long steel fibers are end hook type steel fibers (such as Figure 5As shown), the length is 40 to 60 mm, and the aspect ratio is 60; the short steel fiber is a straight steel fiber (as shown Figure 6 As shown), the length is 10 mm and the aspect ratio is 60.

[0068] The raw materials of the second steel fiber concrete layer 2 include: short steel fiber, cement, water reducing agent, coarse aggregate, fine aggregate and fly ash. The second steel fiber concrete layer is a CF50 short steel fiber concrete layer, and the specific raw material ratio of concrete is as follows: P·O42.5 ordinary Portland cement, with a dosage of 300kg / m 3 ; Drinkable or natural water, dosage 95kg / m 3 ; Polycarboxylic acid-based high-efficiency water reducer, dosage 5kg / m 3 The coarse aggregate is 5-20mm crushed stone with good and continuous grading. The mixing mass ratio of 5-10mm crushed stone to 10-20mm is 5:5. The total amount of coarse aggregate is 1300kg / m 3 ; The fine aggregate is medium-coarse river sand, with a fineness modulus of 3.0 and a dosage of 1200kg / m 3 ; Fly ash, dosage 60kg / m 3 ; Short steel fiber, dosage 35kg / m 3 , short steel fibers are straight steel fibers (such as Figure 6 As shown), the length is 10 mm and the aspect ratio is 60.

[0069] Example 3

[0070] The preparation method of the shield segment of this embodiment is basically the same as that of Example 1. The difference between this embodiment and Example 1 is that the raw materials for preparing the shield segment are different. The shield segment includes a first steel fiber concrete layer 1 and a second steel fiber concrete layer 2. The raw materials of the first steel fiber concrete layer 1 include: long steel fiber, short steel fiber, cement, water reducer, coarse aggregate, fine aggregate and fly ash. The first steel fiber concrete layer is a CF50 long + short steel fiber concrete layer, and the specific raw material ratio of the concrete is as follows: P·O42.5 ordinary Portland cement, with an admixture of 300kg / m 3 ; Drinkable or natural water, dosage 95kg / m 3 ; Polycarboxylic acid-based high-efficiency water reducer, dosage 5kg / m 3 The coarse aggregate is 5-20 mm crushed stone with good and continuous grading. The mixing mass ratio of 5-10 mm crushed stone to 10-20 mm is 8:2. The total amount of coarse aggregate is 1300 kg / m 3 ; The fine aggregate is medium-coarse river sand, with a fineness modulus of about 2.3 and a dosage of 500kg / m 3 ; Fly ash, dosage 100kg / m 3 ; Long steel fiber, dosage 50kg / m 3 , short steel fiber, dosage 3kg / m 3, a total of 53kg / m 3 The long and short steel fibers are mixed. The long steel fibers are one or more of the milling type, shearing type or end hook type; and / or the short steel fibers are straight steel fibers. The long steel fibers are end hook type steel fibers (such as Figure 5 As shown), the length is 40 to 60 mm, and the aspect ratio is 80; the short steel fiber is a straight steel fiber (as shown Figure 6 As shown), the length is 10 mm and the aspect ratio is 80.

[0071] The raw materials of the second steel fiber concrete layer 2 include: short steel fiber, cement, water reducing agent, coarse aggregate, fine aggregate and fly ash. The second steel fiber concrete layer is a CF50 short steel fiber concrete layer, and the specific raw material ratio of concrete is as follows: P·O42.5 ordinary Portland cement, with a dosage of 300kg / m 3 ; Drinkable or natural water, dosage 95kg / m 3 ; Polycarboxylic acid-based high-efficiency water reducer, dosage 10kg / m 3 The coarse aggregate is 5-20 mm crushed stone with good and continuous grading. The mixing mass ratio of 5-10 mm crushed stone to 10-20 mm is 8:2. The total amount of coarse aggregate is 1300 kg / m 3 ; The fine aggregate is medium-coarse river sand, with a fineness modulus of about 2.3 and a dosage of 500kg / m 3 ; Fly ash, dosage 100kg / m 3 ; Short steel fiber, dosage 53kg / m 3 , short steel fibers are straight steel fibers (such as Figure 6 As shown), the length is 10 mm and the aspect ratio is 80.

[0072] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A layered casting of unreinforced hybrid steel fiber concrete shield segment, characterized in that: The shield segment is an arc-shaped structure, and includes, from the inner arc surface to the outer arc surface of the shield segment, a first steel fiber concrete layer and a second steel fiber concrete layer; The raw materials of the first steel fiber concrete layer include: long steel fiber, short steel fiber, cement, water reducing agent, coarse aggregate, fine aggregate and fly ash; The raw materials of the second steel fiber concrete layer include: short steel fibers, cement, water reducing agent, coarse aggregate, fine aggregate and fly ash; The long steel fiber has a length of 40-60 mm and an aspect ratio of 60-80; the short steel fiber has a length of 5-15 mm and an aspect ratio of 60-80.

2. The layered casting unreinforced hybrid steel fiber concrete shield segment according to claim 1 is characterized in that: The amount of long steel fibers added in the first steel fiber concrete layer is 20-50 kg / m 3 The amount of short steel fiber added is 3-15kg / m 3 .

3. The layered casting unreinforced hybrid steel fiber concrete shield segment according to claim 1 is characterized in that: The amount of short steel fibers added to the second steel fiber concrete layer is 20-50 kg / m 3 .

4. The layered casting unreinforced hybrid steel fiber concrete shield segment according to claim 1 is characterized in that: The first steel fiber concrete layer and / or the second steel fiber concrete layer comprises: cement 300-600kg / m 3 , water reducing agent 5-10kg / m 3 , coarse crushed stone 800-1300kg / m 3 , fine aggregate 500-1200kg / m 3 , fly ash 60-100kg / m 3 .

5. The layered casting unreinforced hybrid steel fiber concrete shield segment according to claim 1 is characterized in that: The long steel fibers are one or more of the milling type, shearing type or end hook type; and / or the short steel fibers are straight steel fibers.

6. The layered casting unreinforced hybrid steel fiber concrete shield segment according to claim 1 is characterized in that: The coarse aggregate includes 5-10 mm crushed stone and 10-20 mm crushed stone, and the mixing mass ratio is 5-8:2-5.

7. The layered casting unreinforced hybrid steel fiber concrete shield segment according to claim 1 is characterized in that: The fine aggregate is medium-coarse river sand with a fineness modulus of 2.3-3.

0.

8. A method for manufacturing a layered casting unreinforced hybrid steel fiber concrete shield segment, characterized in that: The following steps are involved: (1) Mold preparation: first assemble the mold, clean the mold surface, apply the release agent, and then adjust the mold; (2) Material preparation: taking long steel fibers, short steel fibers, cement, water reducing agent, coarse aggregate, fine aggregate, and fly ash according to weight ratio, mixing the coarse aggregate, fine aggregate, and cement, and then adding the long steel fibers and short steel fibers, and mixing them, and then adding water, and mixing them, to obtain a first steel fiber concrete; mixing the coarse aggregate, fine aggregate, and cement, and then adding the short steel fibers, and then mixing them, and then adding water, and mixing them, to obtain a second steel fiber concrete; (3) Casting: Cast the first steel fiber concrete layer first, vibrate and compact it, cast the second steel fiber concrete layer before initial setting, and vibrate and compact it again; (4) Steam curing and demoulding: After the concrete is poured, let it stand, then introduce steam for curing, and then demould; (5) Inspection and maintenance; The long steel fiber has a length of 40-60 mm and an aspect ratio of 60-80; the short steel fiber has a length of 5-15 mm and an aspect ratio of 60-80.

9. The method for manufacturing a layered casting unreinforced hybrid steel fiber concrete shield segment according to claim 8, characterized in that: Step (4) After the pouring is completed, the concrete is allowed to stand for 1-3 hours, and the steam curing time is not less than 5 hours. After the steam curing is cooled down, when the concrete strength reaches more than 15 MPa, demoulding is performed; The curing of step (5) is to place the prepared shield segment in a curing pool for 5-10 days.

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