Fe-SMA reinforced UHPC casing for CAES and its construction method

Abstract

The present invention discloses an Fe-SMA reinforced UHPC casing for CAES and a construction method, comprising N UHPC casings and N-1 Fe-SMA pipe joints; each UHPC casing has a central cavity and can be used for underground gas transportation in CAES technology; each UHPC casing has a built-in Fe-SMA spiral hoop cage, and the top outer wall and bottom outer wall of each UHPC casing are provided with an external connection portion; the inner wall of each Fe-SMA pipe joint is provided with an internal connection portion, and each can be connected to an external heating source. The present invention can promote the hydration reaction of the UHPC internal matrix and improve the density of the material, so that the UHPC has higher strength by autoclaving the UHPC casing; at the same time, the high temperature environment during autoclaving can also stimulate the internal Fe-SMA ribs and stimulate their "shape memory" effect, thereby applying circumferential uniform prestress and axial prestress to the UHPC casing, thereby improving the circumferential crack resistance and axial tensile strength, durability and other indicators of underground gas transportation pipelines in the CAES field.

Description

Technical Field

[0001] The present invention relates to the field of compressed air energy storage (CAES), and in particular to an Fe-SMA reinforced UHPC casing for CAES and a construction method thereof. Background Art

[0002] Compressed air energy storage (CAES) utilizes excess off-peak electricity to compress air through underground pipelines into large, sealed underground caverns, such as salt caverns, caverns, or newly constructed gas storage wells. CAES technology, characterized by cleanliness, high efficiency, and low cost, is currently a mainstream air energy storage technology. However, given the long-distance nature of underground gas transmission pipelines, which require high levels of airtightness and corrosion resistance, CAES pipelines often require a high level of quality assurance.

[0003] Currently, underground gas transmission pipelines in CAES technology often face the following problems:

[0004] 1. During transportation, the high-speed airflow carrying sand particles will erode the pipe wall and cause wear, and may even cause deformation, collapse, rupture and other problems of the transport pipeline;

[0005] 2. The circumferential alternating stress generated during the frequent injection and production of transportation pipelines can easily cause cracks on the edges of the pipelines, destroy the integrity of the pipelines and accelerate pipeline corrosion.

[0006] Currently, to address the above issues, the following methods are used in CAES technology for transport pipelines:

[0007] 1. Select high-quality pipes and apply anti-corrosion coating on the pipe wall.

[0008] 2. Run the injection and production string into the production casing to prevent the production casing from directly bearing the alternating load.

[0009] These methods have the following shortcomings:

[0010] 1. The cost is high and the construction is relatively complicated.

[0011] 2. The ability to resist corrosion, erosion and alternating loads is not significant. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide an Fe-SMA reinforced UHPC casing for CAES and a construction method. The Fe-SMA reinforced UHPC casing for CAES and the construction method autoclave the UHPC casing with built-in Fe-SMA spiral stirrups and Fe-SMA axial reinforcements during factory prefabrication, which can promote the hydration reaction of the internal aggregate of the UHPC, improve the density of the material, and make the UHPC have higher strength; at the same time, the high temperature environment during autoclave curing can also stimulate the internal Fe-SMA reinforcement and stimulate its "shape memory" effect, thereby applying circumferential uniform prestress and axial prestress to the UHPC casing, thereby improving the circumferential crack resistance, axial tensile strength, durability and other indicators of underground gas transportation pipelines in the CAES field.

[0013] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0014] An Fe-SMA reinforced UHPC casing for CAES, comprising N UHPC casings and N-1 Fe-SMA pipe joints;

[0015] N UHPC casings are coaxially connected end to end through N-1 Fe-SMA pipe joints;

[0016] Each UHPC casing has a central cavity; wherein the central cavity can be used for underground gas transportation in CAES technology.

[0017] Each UHPC casing is equipped with a Fe-SMA spiral stirrup cage, and the top and bottom outer walls of each UHPC casing are provided with external connection parts.

[0018] The inner wall of each Fe-SMA pipe joint is provided with an inner connecting portion, and each Fe-SMA pipe joint can be connected to an external heating source.

[0019] Before being heated by a heating source, the minimum inner diameter of each Fe-SMA pipe joint is larger than the maximum outer diameter of each UHPC casing, so that each Fe-SMA pipe joint can be sleeved on the outer circumference of the outer connecting portion of two adjacent UHPC casings.

[0020] After being heated by a heating source, each Fe-SMA pipe joint will shrink radially, so that the outer connection portion of the Fe-SMA pipe joint is matched with the inner connection portion of the UHPC casing.

[0021] Each Fe-SMA spiral stirrup cage includes a Fe-SMA spiral stirrup and a Fe-SMA axial rib evenly distributed along the circumference of the Fe-SMA spiral stirrup.

[0022] The outer connection part is a serrated convex groove, and the inner connection part is a serrated groove; after each Fe-SMA pipe joint is heated using a heating source, the outer connection part of the Fe-SMA pipe joint forms a convex-concave or mortise-and-tenon connection with the inner connection part of the UHPC casing.

[0023] The outer connection part is wedge-shaped one, and the inner connection part is wedge-shaped two; after each Fe-SMA pipe joint is heated using a heating source, the outer connection part of the Fe-SMA pipe joint forms a wedge-shaped inclined surface match with the inner connection part of the UHPC casing.

[0024] The outer connection part is an outer thread, and the inner connection part is an inner thread; after each Fe-SMA pipe joint is heated using a heating source, the outer connection part of the Fe-SMA pipe joint and the inner connection part of the UHPC casing can form a threaded connection.

[0025] A construction method for Fe-SMA reinforced UHPC casing for CAES includes the following steps.

[0026] Step 1. Make a Fe-SMA spiral stirrup cage: pre-stretch the Fe-SMA bars and divide them into two groups; one group of Fe-SMA bars is processed into Fe-SMA axial bars of a set size, and the other group of Fe-SMA bars is processed into Fe-SMA spiral stirrups of a set size; then, the Fe-SMA axial bars are evenly tied to the Fe-SMA spiral stirrups along the circumference to form a Fe-SMA spiral stirrup cage.

[0027] Step 2: Making a Fe-SMA pipe joint: pre-stretch the Fe-SMA strip and uniformly carve an inner connecting portion on its surface; then, bend the Fe-SMA strip with the inner connecting portion carved into a tube, and make the inner connecting portion located inside the tube, thereby forming a Fe-SMA pipe joint.

[0028] Step 3: Make the UHPC casing, including the following steps:

[0029] Step 3-1, formwork: Set up the UHPC casing formwork, which has a circular cylindrical inner cavity with the same shape as the UHPC casing.

[0030] Step 3-2: Place the Fe-SMA spiral stirrup cage: Place the Fe-SMA spiral stirrup cage produced in Step 1 in the UHPC casing formwork erected in Step 3-1.

[0031] Step 3-3, pouring: pour the pre-prepared UHPC slurry into the UHPC casing formwork where the Fe-SMA spiral stirrup cage is placed.

[0032] Step 3-4, conventional curing: The UHPC casing cast in step 3-3 and provided with a UHPC casing template is cured for a set time under a standard environment to form a UHPC casing with a set strength; the outer sides of the top and bottom ends of the UHPC casing both have external connection portions that cooperate with the internal connection portions.

[0033] Step 3-5, autoclave curing: remove the UHPC casing template and place the UHPC casing that has completed conventional curing into an autoclave for autoclave curing.

[0034] Step 4: Assembling the UHPC casing: Assemble and connect the two adjacent UHPC casings produced in step 3 using the Fe-SMA pipe joint produced in step 2. Assuming that the two adjacent UHPC casings are an upper UHPC casing and a lower UHPC casing, the specific assembly method includes the following steps:

[0035] Step 4-1. Fixing the upper UHPC casing: Drive the upper UHPC casing into the pre-drilled pipe well, and expose the external connection part at the bottom end of the upper UHPC casing.

[0036] Step 4-2, initial splicing: first, put the Fe-SMA pipe joint on the outer periphery of the exposed external connection part at the bottom end of the upper UHPC casing, and then insert the external connection part at the top end of the lower UHPC casing into the designated position in the Fe-SMA pipe joint.

[0037] Step 4-3, bite-fit splicing: The Fe-SMA pipe joint is heated to stimulate the "shape memory" effect of the Fe-SMA pipe joint, thereby generating circumferential contraction, so that the inner connection part of the Fe-SMA pipe joint forms a tight bite with the outer connection parts of the upper UHPC casing and the lower UHPC casing, respectively, to achieve the splicing of two adjacent UHPC casings.

[0038] Step 4-4: Repeat steps 4-1 to 4-3 to complete the splicing of multiple UHPC casings.

[0039] In step 4, the axial cracking load F of the spliced ​​UHPC casing is t The calculation formula of ' is:

[0040] F t '=F t +F1

[0041] in:

[0042] F t =f t1 S1=f t1 π(r1 2 -r2 2 )

[0043] F1=nfr S2=nf r πr Fe 2

[0044] Where: F t is the axial cracking bearing capacity of the UHPC casing itself (N);

[0045] F1 is the cracking bearing capacity increased by the prestress applied by Fe-SMA tendons to the UHPC casing (N);

[0046] f t1 is the axial crack strength of UHPC casing (MPa);

[0047] S1 is the cross-sectional area of ​​the UHPC casing (mm 2 );

[0048] r1 is the outer radius of the UHPC casing (mm 2 );

[0049] r2 is the inner radius of the UHPC casing (mm 2 );

[0050] f r is the prestress value generated by Fe-SMA tendons (MPa);

[0051] S2 is the cross-sectional area of ​​a single Fe-SMA bar (mm 2 );

[0052] n is the number of axial Fe-SMA ribs in the UHPC casing;

[0053] r Fe is the radius of the Fe-SMA axial rib (mm);

[0054] The axial crack resistance of UHPC casing can be enhanced by increasing the number of Fe-SMA axial ribs, reducing the spacing of Fe-SMA spiral stirrups or reducing the wall thickness of UHPC casing.

[0055] In step 3-5, the heating temperature of the autoclave is 180-200° C., the pressure is 0.9-1.6 MPa, and the autoclave curing time is 3-6 hours.

[0056] In steps 3-5, autoclaving and curing of the UHPC casing can, on the one hand, promote the hydration reaction of the aggregate inside the UHPC, improve the material density, and enhance the strength of the UHPC. On the other hand, the high temperature environment during autoclaving can stimulate the Fe-SMA spiral stirrups and Fe-SMA axial reinforcement built into the UHPC casing, thereby applying uniform circumferential prestress and axial prestress to the UHPC casing, improving its circumferential crack resistance and axial tensile strength.

[0057] The present invention has the following beneficial effects:

[0058] 1. The arrangement of the iron-based shape memory alloy (Fe-SMA) spiral stirrups and axial reinforcement in the present invention makes the axial tensile mechanical properties of the self-prestressed Fe-SMA reinforced UHPC casing F t 'Compared with the axial tensile mechanical properties of UHPC casing without Fe-SMA spiral stirrups and Fe-SMA axial reinforcement t , increased by more than 15%, thereby greatly improving the axial crack resistance and tensile strength of the transport pipeline while keeping the original size of the casing unchanged.

[0059] 2. During the production process, this self-prestressed Fe-SMA-reinforced UHPC casing undergoes autoclave curing. This not only promotes the hydration reaction of fine aggregate in the UHPC, increasing the density and compressive strength of the UHPC material, but also stimulates the Fe-SMA spiral stirrups and axial reinforcements within the UHPC casing, imparting uniform circumferential and axial prestressing stresses to the casing, improving its circumferential crack resistance, axial tensile strength, and corrosion resistance. Autoclave curing achieves a two-pronged effect for this self-prestressed Fe-SMA-reinforced UHPC casing.

[0060] 3. This invention significantly improves the axial tensile and circumferential crack resistance of underground gas pipelines used in CAES applications, thereby preventing axial tensile or circumferential cracking damage during long-distance vertical installation or when subjected to circumferential alternating stress. The excellent corrosion resistance of UHPC significantly extends the service life of underground gas pipelines, protecting them from erosion by high-speed airflow and corrosive damage from the external environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 A cross-sectional view of a Fe-SMA reinforced UHPC casing for CAES according to the present invention is shown.

[0062] Figure 2 A three-dimensional image of the Fe-SMA spiral stirrup cage of the present invention is shown.

[0063] Figure 3 A cross-sectional view of the Fe-SMA pipe joint of the present invention is shown.

[0064] Figure 4 A schematic diagram of the assembly process of two adjacent UHPC sleeves in the present invention is shown; wherein, Figure (a) is a schematic diagram of the assembly of the Fe-SMA pipe joint before heating; Figure (b) is a schematic diagram of the assembly of the Fe-SMA pipe joint after heating.

[0065] Figure 5 Schematic diagrams showing the autoclave curing process and on-site hoisting assembly of the UHPC casing in the present invention are shown; wherein, Figure (a) is a schematic diagram of the autoclave curing of the UHPC casing; (b) is a schematic diagram of the state of the UHPC casing after autoclave curing is completed; and (c) is a schematic diagram of the UHPC casing assembly process.

[0066] Among them are:

[0067] 1-Fe-SMA axial reinforcement; 2-Fe-SMA spiral stirrups; 3-Fe-SMA pipe joints; 4-UHPC casing; 5-serrated grooves; 6-autoclave; 7-Fe-SMA spiral stirrup cage; 8-electric excitation control equipment; 9-derrick; 10-bridge crane. DETAILED DESCRIPTION

[0068] The present invention will be further described in detail below with reference to the accompanying drawings and specific preferred embodiments.

[0069] In the description of the present invention, it should be understood that the terms "left side," "right side," "upper," "lower," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Terms such as "first" and "second" do not indicate the importance of components and therefore should not be construed as limitations on the present invention. The specific dimensions used in this embodiment are intended only to illustrate the technical solution and do not limit the scope of protection of the present invention.

[0070] like Figure 1 、 Figure 4 Shown and Figure 5 , an Fe-SMA reinforced UHPC casing for CAES, including N UHPC casings 4 and N-1 Fe-SMA pipe joints 3.

[0071] N UHPC casings are coaxially connected end to end through N-1 Fe-SMA pipe joints.

[0072] Each UHPC casing has a central cavity; wherein the central cavity can be used for underground gas transportation in CAES technology.

[0073] Each UHPC casing is built with a Fe-SMA spiral stirrup cage 7, such as Figure 2 As shown, each Fe-SMA spiral stirrup cage includes a Fe-SMA spiral stirrup 2 and a Fe-SMA axial rib 1 uniformly distributed along the circumference of the Fe-SMA spiral stirrup.

[0074] The top outer wall and the bottom outer wall of each UHPC casing are provided with an external connection portion.

[0075] The inner wall of each Fe-SMA pipe joint is provided with an inner connecting portion, and each Fe-SMA pipe joint can be connected to an external heating source.

[0076] Before being heated by a heating source, the minimum inner diameter of each Fe-SMA pipe joint is larger than the maximum outer diameter of each UHPC casing, so that each Fe-SMA pipe joint can be sleeved on the outer circumference of the outer connecting portion of two adjacent UHPC casings.

[0077] After being heated by a heating source, each Fe-SMA pipe joint will shrink radially, so that the outer connection portion of the Fe-SMA pipe joint is matched with the inner connection portion of the UHPC casing.

[0078] The above-mentioned external connection part and internal connection part preferably have the following three embodiments.

[0079] Example 1

[0080] like Figure 1 and Figure 3 As shown, the outer connection portion is a serrated convex groove 5, and the inner connection portion is a serrated concave groove. After heating each Fe-SMA pipe joint using a heating source, the outer connection portion of the Fe-SMA pipe joint forms a convex-concave or mortise-and-tenon connection with the inner connection portion of the UHPC casing. The heating source is preferably electrical excitation, ceramic armor heating, infrared radiation heating, etc.

[0081] Example 2

[0082] The outer connection part is wedge-shaped one, and the inner connection part is wedge-shaped two; after each Fe-SMA pipe joint is heated using a heating source, the outer connection part of the Fe-SMA pipe joint forms a wedge-shaped inclined surface match with the inner connection part of the UHPC casing.

[0083] Example 3

[0084] The outer connection part is an outer thread, and the inner connection part is an inner thread; after each Fe-SMA pipe joint is heated using a heating source, the outer connection part of the Fe-SMA pipe joint and the inner connection part of the UHPC casing can form a threaded connection.

[0085] Ultra-High Performance Concrete (UHPC) is a new type of ultra-high performance cement-based material based on the closest packing theory. It has the advantages of high strength and excellent durability: its compressive strength is generally above 120MPa, which is at least 3 to 4 times that of traditional concrete. The tensile strength of UHPC is usually above 10MPa, which is about 10 times that of ordinary concrete. UHPC is almost impermeable, with almost zero chloride ion permeability and sulfate permeability, and has excellent corrosion resistance. Based on this, UHPC is a good choice for underground gas transmission pipelines in the CAES field.

[0086] However, simply using UHPC casing as the underground gas transmission pipeline in CAES technology cannot simultaneously meet the requirements of long-distance vertical tensile strength and circumferential crack resistance. Iron-based shape memory alloy (Fe-SMA) has the potential for large-scale application in the field of civil engineering due to its low cost, shape memory function and superelasticity. The shape memory effect of Fe-SMA is mainly achieved by the transformation between internal martensite crystals and austenite crystals. After the pre-stretched Fe-SMA is subjected to high temperature, the internal martensite crystals and austenite crystals transform, which is manifested macroscopically as the deformation of Fe-SMA being restored.

[0087] By pre-embedding Fe-SMA within a structure, utilizing its shape memory effect, it generates recovery stress after exposure to high temperatures, thereby prestressing the structure. This paper proposes a self-prestressed Fe-SMA-reinforced UHPC casing. Fe-SMA, embedded within the UHPC casing in the form of spiral stirrups and axial reinforcement, applies uniform circumferential prestress and axial prestress, respectively, to the structure under high-temperature conditions. This meets the high requirements for axial tensile strength, circumferential crack resistance, and corrosion resistance in the CAES field for transportation pipelines.

[0088] A construction method for Fe-SMA reinforced UHPC casing for CAES includes the following steps.

[0089] Step 1: Make Fe-SMA spiral stirrup cage: pre-stretch the Fe-SMA bars and divide them into two groups; one group of Fe-SMA bars is processed into Fe-SMA axial bars of set size, and the other group of Fe-SMA bars is processed into Fe-SMA spiral stirrups of set size; then, evenly tie the Fe-SMA axial bars to the Fe-SMA spiral stirrups along the circumference, so as to form Figure 2 The Fe-SMA spiral stirrup cage shown.

[0090] Step 2: Make Fe-SMA pipe joint: pre-stretch the Fe-SMA strip and evenly carve the inner connection part on its surface; then, bend the Fe-SMA strip with the inner connection part carved into a tube, and make the inner connection part located inside the tube, so as to form a tube. Figure 3 Fe-SMA pipe fitting shown.

[0091] Step 3: Make the UHPC casing, including the following steps:

[0092] Step 3-1: Formwork: Erect the UHPC casing formwork. The UHPC casing formwork has a circular cylindrical inner cavity with the same shape as the UHPC casing. The UHPC casing formwork consists of a cylindrical inner mold and a cylindrical outer mold, arranged coaxially from the inside to the outside. The cylindrical outer mold is preferably a log or steel formwork with serrated grooves at both the top and bottom. The cylindrical inner mold is preferably an inflatable cylindrical airbag or a removable cylindrical formwork.

[0093] Step 3-2: Place the Fe-SMA spiral stirrup cage: Place the Fe-SMA spiral stirrup cage produced in Step 1 in the UHPC casing formwork erected in Step 3-1.

[0094] Step 3-3, pouring: pour the pre-prepared UHPC slurry into the UHPC casing formwork where the Fe-SMA spiral stirrup cage is placed.

[0095] Step 3-4, conventional curing: The UHPC casing cast in step 3-3 and provided with a UHPC casing template is cured under a standard environment for a set time, such as 3 to 4 days, to form a UHPC casing having a set strength; the outer sides of the top and bottom ends of the UHPC casing both have external connection portions that cooperate with the internal connection portions.

[0096] Step 3-5: Autoclave curing: Remove the UHPC casing template and place the conventionally cured UHPC casing in an autoclave for autoclave curing. The autoclave temperature is preferably 180-200°C, the pressure is preferably 0.9-1.6 MPa, and the autoclave curing time is preferably 3-6 hours.

[0097] During autoclaving, the UHPC casing can, on the one hand, promote the hydration reaction of the aggregate inside the UHPC, improve the density of the material, and enhance the strength of the UHPC. On the other hand, the high temperature environment during autoclaving can stimulate the Fe-SMA spiral stirrups and Fe-SMA axial reinforcement built into the UHPC casing, thereby applying uniform circumferential prestress and axial prestress to the UHPC casing, improving its circumferential crack resistance and axial tensile strength.

[0098] Step 4: UHPC casing assembly: Figure 5 As shown, two adjacent UHPC casings manufactured in step 3 are assembled and connected through the Fe-SMA pipe joint manufactured in step 2; assuming that the two adjacent UHPC casings are an upper UHPC casing and a lower UHPC casing, the specific assembly method includes the following steps:

[0099] Step 4-1. Fixing the upper UHPC casing: Drive the upper UHPC casing into the pre-drilled pipe well, and expose the external connection part at the bottom end of the upper UHPC casing.

[0100] Step 4-2, initial splicing: First, vertically hoist the Fe-SMA pipe joint using the derrick 9 and the bridge crane (overhead crane) 10, and fit it around the outer periphery of the exposed outer connection portion at the bottom end of the upper UHPC casing. Then, vertically hoist the lower UHPC casing, and insert the outer connection portion at the top end of the lower UHPC casing into the designated position of the Fe-SMA pipe joint.

[0101] Step 4-3, bite splicing: The Fe-SMA pipe joint is preferably electrified by the electrified excitation console 9 to heat it up, thereby stimulating the "shape memory" effect of the Fe-SMA pipe joint and causing it to shrink in annular direction, so that the inner connecting portion of the Fe-SMA pipe joint forms a tight bite with the outer connecting portion of the upper UHPC casing and the lower UHPC casing, respectively, so that the adjacent two UHPC casings are spliced, as shown in FIG. Figure 4 shown.

[0102] Step 4-4: Repeat steps 4-1 to 4-3 to complete the splicing of multiple UHPC casings.

[0103] The axial cracking load F of the above-mentioned UHPC casing is t The calculation formula of ' is:

[0104] F t '=F t +F1

[0105] in:

[0106] F t =f t1 S1=f t1 π(r1 2 -r2 2 )

[0107] F1=nf r S2=nf r πr Fe 2

[0108] Where: F t is the axial cracking bearing capacity of the UHPC casing itself (N);

[0109] F1 is the cracking bearing capacity increased by the prestress applied by Fe-SMA tendons to the UHPC casing (N);

[0110] f t1 is the axial crack strength of UHPC casing (MPa);

[0111] S1 is the cross-sectional area of ​​the UHPC casing (mm 2 );

[0112] r1 is the outer radius of the UHPC casing (mm2 );

[0113] r2 is the inner radius of the UHPC casing (mm 2 );

[0114] f r is the prestress value generated by the Fe-SMA axial reinforcement (MPa);

[0115] S2 is the cross-sectional area of ​​a single Fe-SMA axial rib (mm 2 );

[0116] n is the number of axial Fe-SMA ribs in the UHPC casing;

[0117] r Fe is the radius of the Fe-SMA axial rib (mm);

[0118] The axial tensile properties of UHPC casing can be enhanced by increasing the number of Fe-SMA axial ribs, reducing the spacing of Fe-SMA spiral stirrups or reducing the wall thickness of UHPC casing.

[0119] To prove the feasibility of the above scheme, a 900m deep salt cavern energy storage well is taken as an example. The inner diameter of a single UHPC pipe is 400mm and the length is 9m. Each pipe is equipped with 12 Fe-SMA axial ribs with a diameter of 10mm and a Fe-SMA spiral stirrup with a diameter of 10mm. The Fe-SMA reinforced UHPC casing is vertically hoisted and placed in the pipeline well, where the pipe wall thickness is divided into three types: 100mm wall thickness for 0-700m underground, 80mm wall thickness for 700-850mm underground, and 60mm wall thickness for 850-900mm underground. The default most unfavorable situation is that all casings are vertically suspended and hoisted. In order to prove that the self-prestressed Fe-SMA reinforced UHPC casing will not suffer axial cracking and damage, this scheme is used to verify the feasibility of the embodiment:

[0120] The dead weight of UHPC casing is ρ=25kN / m 3 According to gravity G = ρSh, the weight of a single UHPC casing with a length of l = 9m and a wall thickness of 100mm and built-in Fe-SMA reinforcement is G1 = 35.34kN; the weight of a UHPC casing with a wall thickness of 80mm and a length of l = 9m and built-in Fe-SMA reinforcement is G2 = 27.14kN; the weight of a UHPC casing with a wall thickness of 60mm and a length of l = 9m and built-in Fe-SMA reinforcement is G3 = 19.51kN.

[0121] For a salt cavern energy storage well with a depth of H=900m, the number of UHPC casings with a wall thickness of 100mm is:

[0122]

[0123] The number of UHPC casings with a wall thickness of 80 mm required:

[0124]

[0125] The number of UHPC casings with a wall thickness of 60 mm required:

[0126]

[0127] Considering the most unfavorable situation, that is, the top UHPC casing bears the maximum tensile force, its axial crack resistance must be greater than:

[0128] F t ”=N1·G1+N2·G2+N3·G3=3334.96kN

[0129] The prepared UHPC casing can increase the steel fiber content appropriately to improve its tensile strength. At the same time, by adjusting the UHPC material ratio, the tensile strength of the UHPC casing after autoclaving can reach more than 20MPa. Here, the UHPC casing strength f t1 =20MPa conservative calculation.

[0130] The axial cracking bearing capacity of the UHPC casing itself is F t =f t1 π(r12-r2 2 )=3141.593kN.

[0131] The 10mm diameter Fe-SMA axial rib can generate a recovery stress of 300-400MPa after high temperature excitation at 200℃. Here, the recovery stress of the Fe-SMA rib is also taken as f r =300MPa conservatively calculated, the cracking bearing capacity F1 increased by the prestressing force applied by 12 Fe-SMA bars to the UHPC casing is F1 = n·f r ·πr Fe 2 =282.743kN.

[0132] In summary, the axial cracking bearing capacity F of the spliced ​​UHPC casing is t '=F t +F1=3424.336kN, which is greater than the required F t ”=3334.96kN, meeting the design requirements.

[0133] It should be noted that the above calculations are conservative for a 900m deep salt cavern energy storage pipeline. They do not account for factors such as the partial axial prestress provided by the Fe-SMA spiral stirrups, the friction between the Fe-SMA-reinforced UHPC casing and the salt cavern energy storage wellbore, and the active hoop effect of the Fe-SMA spiral stirrups on the axial tensile strength, thus providing a certain safety margin. In summary, this self-prestressed Fe-SMA-reinforced UHPC casing is feasible for use in 900m deep salt cavern compressed air energy storage wells and meets design requirements.

[0134] The heating temperature of the autoclave is preferably 180-200°C, the pressure is preferably 0.9-1.6 MPa, the autoclave curing time is preferably 3-6 hours, and the recovery stress of Fe-SMA is generally 300-400 MPa. After experiencing the high temperature environment of autoclave curing, the Fe-SMA axial reinforcement will activate its "shape memory" effect, applying axial prestress to the UHPC casing, preventing excessive axial force generated during vertical lifting and splicing of the self-prestressed Fe-SMA-reinforced UHPC casing, which may cause axial tensile cracking of the casing. Similarly, after experiencing the high temperature environment of autoclave curing, the Fe-SMA spiral stirrups will activate their "shape memory" effect, applying uniform circumferential prestress to the UHPC casing, preventing circumferential tensile cracking of the transportation pipeline caused by the circumferential alternating stress generated by frequent injection and production during use of the self-prestressed Fe-SMA-reinforced UHPC casing.

[0135] The number of Fe-SMA axial bars in the present invention is not necessarily limited to eight and can be increased to 10, 12, or other numbers. The specific number should be determined based on the required axial prestressing level in the specific project. The Fe-SMA stirrups in the present invention are not necessarily limited to spiral stirrups and can also be circular stirrups, single-sided circular stirrups, square stirrups, etc. All of these Fe-SMA axial bars and Fe-SMA stirrup forms fall within the scope of protection of the present invention.

[0136] The UHPC (ultra-high performance concrete) casing used in the present invention has excellent durability indicators such as resistance to chloride ion corrosion, sulfate corrosion, chemical corrosion, carbonization, and wear resistance, and is an ideal energy storage and transportation material in the CAES field.

[0137] The present invention is mainly used for conveying pipelines in the field of Compressed-Air Energy Storage (CAES). Autoclaving and curing the UHPC casing with autoclave equipment can promote the hydration reaction of the aggregate in the UHPC and improve the compressive strength and other indicators of the UHPC; at the same time, the high temperature environment in the autoclave can stimulate the Fe-SMA ribs built into the UHPC casing to generate recovery stress, thereby applying prestress to the UHPC casing, achieving the purpose of "killing two birds with one stone". The Fe-SMA axial ribs are built into the UHPC casing, and after being stimulated by the high temperature environment, they can provide axial pre-compression stress to the UHPC casing to improve its axial tensile performance. After being stimulated by the high temperature environment, the Fe-SMA spiral stirrups can apply uniform circumferential pre-pressure to the UHPC casing to prevent the alternating stress generated by frequent injection and production in the field of CAES from causing cracks in the pipe wall. The ends of the UHPC casing have serrated grooves. The continuous UHPC casings are connected by Fe-SMA pipe joints with serrated grooves on the inner side. The Fe-SMA is heated / energized to cause it to shrink in the annular direction. The teeth between the outer side of the UHPC casing and the inner side of the Fe-SMA pipe joint are tightly engaged, achieving a firm connection between the continuous UHPC casings.

[0138] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention.

Claims

1. A construction method for Fe-SMA reinforced UHPC casing for CAES, characterized by: The steps include: Step 1: Fabricate a Fe-SMA spiral stirrup cage: Pre-stretch the Fe-SMA bars and divide them into two groups; one group of Fe-SMA bars is processed into Fe-SMA axial bars of a set size, and the other group of Fe-SMA bars is processed into Fe-SMA spiral stirrups of a set size; then, the Fe-SMA axial bars are evenly tied to the Fe-SMA spiral stirrups along the circumference, thereby forming a Fe-SMA spiral stirrup cage; Step 2: Fabricating an Fe-SMA pipe joint: pre-stretching the Fe-SMA strip and uniformly engraving the inner connecting portion on its surface; then, bending the Fe-SMA strip with the engraved inner connecting portion into a tube, with the inner connecting portion located inside the tube, thereby forming an Fe-SMA pipe joint; Step 3: Make the UHPC casing, including the following steps: Step 3-1, formwork: erect the UHPC casing formwork, which has a circular cylindrical inner cavity with the same shape as the UHPC casing; Step 3-2, placing the Fe-SMA spiral stirrup cage: Place the Fe-SMA spiral stirrup cage made in step 1 in the UHPC casing template erected in step 3-1; Step 3-3, pouring: pour the pre-prepared UHPC slurry into the UHPC casing formwork with the Fe-SMA spiral stirrup cage placed; Step 3-4, conventional curing: The UHPC casing cast in step 3-3 and provided with the UHPC casing template is cured for a set time under a standard environment to form a UHPC casing with a set strength; the outer sides of the top and bottom ends of the UHPC casing are both provided with external connection parts that match the internal connection parts; Step 3-5, autoclave curing: remove the UHPC casing template and place the conventionally cured UHPC casing into the autoclave for autoclave curing; Step 4: Assembling the UHPC casing: Assemble and connect the two adjacent UHPC casings produced in step 3 using the Fe-SMA pipe joint produced in step 2. Assuming that the two adjacent UHPC casings are an upper UHPC casing and a lower UHPC casing, the specific assembly method includes the following steps: Step 4-1. Fix the upper UHPC casing: Drive the upper UHPC casing into the pre-drilled pipe well, and expose the external connection part at the bottom end of the upper UHPC casing; Step 4-2, initial splicing: first, put the Fe-SMA pipe joint on the outer periphery of the exposed outer connection part at the bottom end of the upper UHPC casing, and then insert the outer connection part at the top end of the lower UHPC casing into the designated position of the Fe-SMA pipe joint; Step 4-3, occlusal splicing: The Fe-SMA pipe joint is heated to stimulate its "shape memory" effect, causing circumferential contraction. This allows the inner connection of the Fe-SMA pipe joint to form a tight occlusal fit with the outer connection of the upper and lower UHPC casings, respectively, to achieve splicing of the two adjacent UHPC casings. Step 4-4: Repeat steps 4-1 to 4-3 to complete the splicing of multiple UHPC casings.

2. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 1, characterized in that: In step 4, the axial cracking load F of the spliced ​​UHPC casing is t The calculation formula of ′ is: F t ′=F t +F1 in: F t =f t1 S1=f t1 π(r1 2 -r2 2 ) F1=nf r S2=nf r πr Fe 2 Where: F t is the axial cracking bearing capacity of the UHPC casing itself (N); F1 is the cracking bearing capacity increased by the prestress applied by the Fe-SMA axial reinforcement to the UHPC casing (N); f t1 is the axial crack strength of UHPC casing (MPa); S1 is the cross-sectional area of ​​the UHPC casing (mm 2 ); r1 is the outer radius of the UHPC casing (mm 2 ); r2 is the inner radius of the UHPC casing (mm 2 ); f r is the prestress value generated by the Fe-SMA axial reinforcement (MPa); S2 is the cross-sectional area of ​​a single Fe-SMA axial rib (mm 2 ); n is the number of axial Fe-SMA ribs in the UHPC casing; r Fe is the radius of the Fe-SMA axial rib (mm).

3. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 2, characterized in that: The axial tensile properties of UHPC casing can be enhanced by increasing the number of Fe-SMA axial ribs, reducing the spacing of Fe-SMA spiral stirrups or reducing the wall thickness of UHPC casing.

4. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 1, characterized in that: In step 3-5, the heating temperature of the autoclave is 180-200° C., the pressure is 0.9-1.6 MPa, and the autoclave curing time is 3-6 hours.

5. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 1 or 4, characterized in that: In steps 3-5, autoclaving and curing of the UHPC casing can, on the one hand, promote the hydration reaction of the aggregate inside the UHPC, improve the material density, and enhance the strength of the UHPC. On the other hand, the high temperature environment during autoclaving can stimulate the Fe-SMA spiral stirrups and Fe-SMA axial reinforcement built into the UHPC casing, thereby applying uniform circumferential prestress and axial prestress to the UHPC casing, improving its circumferential crack resistance and axial tensile strength.

6. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 1, characterized in that: Based on the Fe-SMA reinforced UHPC casing for CAES, the Fe-SMA reinforced UHPC casing includes N UHPC casings and N-1 Fe-SMA pipe joints; N UHPC casings are coaxially connected end to end through N-1 Fe-SMA pipe joints; Each UHPC casing has a central cavity, which can be used to transport underground gas in CAES technology. Each UHPC casing is built with a Fe-SMA spiral hoop cage, and each UHPC casing has external connections on the top and bottom outer walls. The inner wall of each Fe-SMA pipe joint is provided with an internal connection part, and each Fe-SMA pipe joint can be connected to an external heating source; Before being heated by a heating source, the minimum inner diameter of each Fe-SMA pipe joint is larger than the maximum outer diameter of each UHPC casing, so that each Fe-SMA pipe joint can be sleeved on the outer circumference of the outer connection portion of two adjacent UHPC casings; After being heated by a heating source, each Fe-SMA pipe joint will shrink radially, so that the outer connection portion of the Fe-SMA pipe joint is matched with the inner connection portion of the UHPC casing.

7. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 6, characterized in that: Each Fe-SMA spiral stirrup cage includes a Fe-SMA spiral stirrup and a Fe-SMA axial rib evenly distributed along the circumference of the Fe-SMA spiral stirrup.

8. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 6, characterized in that: The outer connection part is a serrated convex groove, and the inner connection part is a serrated groove; after each Fe-SMA pipe joint is heated using a heating source, the outer connection part of the Fe-SMA pipe joint forms a convex-concave or mortise-and-tenon connection with the inner connection part of the UHPC casing.

9. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 6, characterized in that: The outer connection part is wedge-shaped one, and the inner connection part is wedge-shaped two; after each Fe-SMA pipe joint is heated using a heating source, the outer connection part of the Fe-SMA pipe joint forms a wedge-shaped inclined surface match with the inner connection part of the UHPC casing.

10. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 6, characterized in that: The outer connection part is an outer thread, and the inner connection part is an inner thread; after each Fe-SMA pipe joint is heated using a heating source, the outer connection part of the Fe-SMA pipe joint and the inner connection part of the UHPC casing can form a threaded connection.

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