Fe-SMA reinforced UHPC sleeve for CAES and construction method

Abstract

The invention discloses a Fe-SMA reinforced UHPC sleeve for a CAES and a construction method. The Fe-SMA reinforced UHPC sleeve comprises N UHPC sleeves and N-1 Fe-SMA pipe joints, each UHPC sleeve is provided with a central cavity and can be used for underground gas transportation in the CAES technology; a Fe-SMA spiral stirrup cage is arranged in each UHPC sleeve, and outer connecting parts are arranged on the outer wall of the top end and the outer wall of the bottom end of each UHPC sleeve; the inner wall of each Fe-SMA pipe joint is provided with an inner connecting part, and each Fe-SMA pipe joint can be externally connected with a heating source. The UHPC sleeve is subjected to autoclaved curing, so that the hydration reaction of an internal matrix of the UHPC can be promoted, the compactness of the material is improved, and the UHPC has higher strength; and meanwhile, the high-temperature environment in autoclaved curing can excite the internal Fe-SMA ribs and excite the shape memory effect of the Fe-SMA ribs, so that circumferential uniform pre-compressive stress and axial pre-compressive stress are applied to the UHPC sleeve, and the indexes such as circumferential crack resistance, axial tensile property and durability of the underground gas transportation pipeline in the CAES field are improved.

Description

Technical Field

[0001] The 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, referred to as CAES (Compressed-Air Energy Storage), refers to the use of non-peak excess electricity to compress air into a closed large-capacity underground cave as a gas storage chamber through an underground transportation pipeline, such as a salt cave, cave or a newly built gas storage well. CAES technology has the advantages of being clean and pollution-free, high efficiency and low cost, and is one of the mainstream technologies of air energy storage technology. Considering the long-distance transportation of underground gas transmission pipelines, the high requirements for airtightness and corrosion resistance, etc., the underground gas transportation pipelines in CAES technology often need to have a high quality assurance.

[0003] At present, 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 transportation pipeline;

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

[0006] At present, in response to the above problems, the methods adopted by CAES technology for transportation pipelines are:

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

[0008] 2. Install 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 provide a Fe-SMA reinforced UHPC casing and a construction method for CAES in view of the deficiencies of the above-mentioned prior art. The Fe-SMA reinforced UHPC casing and the construction method for CAES can promote the hydration reaction of the internal aggregate of UHPC and improve the density of the material to make UHPC have higher strength by autoclaving and curing the UHPC casing with built-in Fe-SMA spiral stirrups and Fe-SMA axial ribs during factory prefabrication. 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 pre-compression stress and axial pre-compression stress 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.

[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 hoop cage, and the top outer wall and the bottom outer wall of each UHPC casing are provided with external connecting 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 externally connected to a heating source.

[0019] Before being heated by a heating source, the minimum inner diameter of each Fe-SMA pipe joint is greater 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 comprises a Fe-SMA spiral stirrup and a Fe-SMA axial rib uniformly arranged 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 concave groove; after each Fe-SMA pipe joint is heated by 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 by 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 by 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 a Fe-SMA reinforced UHPC casing for CAES comprises the following steps.

[0026] Step 1, making a Fe-SMA spiral hoop cage: pre-stretch the Fe-SMA tendons and divide them into two groups; one group of Fe-SMA tendons is processed into Fe-SMA axial tendons of set sizes, and the other group of Fe-SMA tendons is processed into Fe-SMA spiral hoop tendons of set sizes; then, the Fe-SMA axial tendons are evenly tied to the Fe-SMA spiral hoop tendons along the circumferential direction to form a Fe-SMA spiral hoop cage.

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

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

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

[0030] Step 3-2, placing the Fe-SMA spiral stirrup cage: place the Fe-SMA spiral stirrup cage manufactured in step 1 in the UHPC casing template 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 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 both have outer connection parts that match the inner connection parts.

[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, UHPC casing assembly: assemble and connect the two adjacent UHPC casings manufactured in step 3 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:

[0035] Step 4-1, upper UHPC casing fixing: drive the upper UHPC casing into the pre-drilled pipeline well, and expose the outer connection part at the bottom end of the upper UHPC casing.

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

[0037] Step 4-3, bite 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 is tightly bitten with the outer connection part 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 the Fe-SMA tendon (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, when the UHPC casing is autoclaved and cured, on the one hand, the hydration reaction of the aggregate inside the UHPC can be promoted, the density of the material can be improved, and the strength of the UHPC can be enhanced; on the other hand, the high temperature environment during the autoclave curing process can stimulate the Fe-SMA spiral stirrups and Fe-SMA axial ribs built into the UHPC casing, thereby applying circumferential uniform prestress and axial prestress to the UHPC casing, thereby improving its circumferential crack resistance and axial tensile resistance.

[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 ribs 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, the self-prestressed Fe-SMA reinforced UHPC casing is autoclaved and cured by autoclave equipment, which can promote the hydration reaction of fine aggregate in UHPC, improve the density of UHPC materials, and enhance the compressive strength of UHPC; at the same time, the high temperature environment during the autoclave curing process can also stimulate the Fe-SMA spiral stirrups and axial ribs in the UHPC casing, apply circumferential uniform and axial prestressing stress to the UHPC casing, and improve the circumferential crack resistance, axial tensile resistance, corrosion resistance and other properties of the UHPC casing. Autoclave curing can achieve the effect of "killing two birds with one stone" for the self-prestressed Fe-SMA reinforced UHPC casing.

[0060] 3. The present invention can greatly improve the axial tensile and circumferential crack resistance of underground gas transportation pipelines in the CAES field, thereby preventing axial tensile or circumferential cracking damage during vertical long-distance lifting or circumferential alternating stress. The excellent corrosion resistance of UHPC materials can greatly increase the service life of underground gas transportation pipelines, preventing high-speed airflow erosion of the pipe wall and corrosion damage to the pipeline by the external environment during use. 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 hoop 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; and Figure (b) is a schematic diagram of the assembly of the Fe-SMA pipe joint after heating.

[0065] Figure 5 The schematic diagram of the autoclave curing process and on-site hoisting assembly of the UHPC casing in the present invention is 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 the autoclave curing is completed; (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 convex grooves; 6-autoclave; 7-Fe-SMA spiral stirrup cage; 8-power-on excitation control equipment; 9-derrick; 10-bridge crane. DETAILED DESCRIPTION

[0068] The present invention will be further described in detail below in conjunction with 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 part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating 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 , a Fe-SMA reinforced UHPC casing for CAES, comprising N UHPC casings 4 and N-1 Fe-SMA pipe joints 3.

[0071] N UHPC casings are coaxially connected end to end in sequence 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 arranged 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 part.

[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 externally connected to a heating source.

[0076] Before being heated by a heating source, the minimum inner diameter of each Fe-SMA pipe joint is greater 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 part is a sawtooth convex groove 5, and the inner connection part is a sawtooth groove; after each Fe-SMA pipe joint is heated by 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. The heating source is preferably electric excitation / ceramic armor heating / infrared ray 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 by 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 by 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 field of CAES.

[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 as the recovery of the Fe-SMA deformation on a macro scale.

[0087] By using the "shape memory" effect of Fe-SMA, it is embedded in the structure. After experiencing high temperature, Fe-SMA will generate recovery stress, thereby applying prestress to the structure. This paper proposes a self-prestressed Fe-SMA reinforced UHPC casing. Fe-SMA is built into the UHPC casing in the form of spiral stirrups and axial ribs. Under high temperature environment, it can apply circumferential uniform prestress and axial prestress to the structure respectively, thereby meeting the high requirements for axial tensile resistance, circumferential crack resistance and corrosion resistance of transportation pipelines in the CAES field.

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

[0089] Step 1, making a Fe-SMA spiral hoop 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 hoop bars of set size; then, the Fe-SMA axial bars are evenly tied to the Fe-SMA spiral hoop bars along the circumferential direction, so as to form a cage as shown in FIG. Figure 2 The Fe-SMA spiral stirrup cage shown.

[0090] Step 2, making a 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 Figure 3 The Fe-SMA pipe fitting shown.

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

[0092] Step 3-1, formwork: erect the UHPC casing formwork, which has a circular cylindrical inner cavity with the same shape as the UHPC casing. The UHPC casing formwork includes a cylindrical inner mold and a cylindrical outer mold coaxially arranged from the inside to the outside; wherein the cylindrical outer mold is preferably a log / steel formwork with serrated convex grooves at both the top and bottom ends. The cylindrical inner mold preferably adopts an inflatable cylindrical airbag or a detachable cylindrical formwork.

[0093] Step 3-2, placing the Fe-SMA spiral stirrup cage: place the Fe-SMA spiral stirrup cage manufactured in step 1 in the UHPC casing template 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 with a set strength; the top outer side and the bottom outer side of the UHPC casing both have an outer connection portion that matches the inner connection portion.

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

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

[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, upper UHPC casing fixing: drive the upper UHPC casing into the pre-drilled pipeline well, and expose the outer connection part at the bottom end of the upper UHPC casing.

[0100] Step 4-2, initial splicing: First, the Fe-SMA pipe joint is vertically hoisted by the derrick 9 and the bridge crane (overhead crane) 10, and is sleeved on the outer periphery of the exposed outer connection part at the bottom end of the upper UHPC casing. Then, the lower UHPC casing is vertically hoisted, and the outer connection part at the top end is inserted into the designated position of the Fe-SMA pipe joint.

[0101] Step 4-3, bite splicing: The Fe-SMA pipe joint is preferably energized by an energized excitation console 9 to heat it up, stimulating the "shape memory" effect of the Fe-SMA pipe joint to produce annular contraction, so that the inner connection part of the Fe-SMA pipe joint is tightly bitten with the outer connection part of the upper UHPC casing and the lower UHPC casing, respectively, so that the splicing of the two adjacent UHPC casings is as follows: 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 after splicing 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 hoop with a diameter of 10mm. The Fe-SMA reinforced UHPC casing is vertically hoisted and placed in the pipeline well, and 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] UHPC casing deadweight ρ=25kN / m 3 According to the gravity G=ρSh, the weight of a single UHPC casing with built-in Fe-SMA ribs and a length of l=9m and a wall thickness of 100mm is G1=35.34kN; the weight of a UHPC casing with built-in Fe-SMA ribs and a wall thickness of 80mm and a length of l=9m is G2=27.14kN; the weight of a UHPC casing with built-in Fe-SMA ribs and a wall thickness of 60mm and a length of l=9m 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 capacity 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 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 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 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, greater than the required F t ”=3334.96kN, meeting the design requirements.

[0133] It should be noted that the above calculations are conservative calculations for 900m deep salt cavern energy storage pipelines. In fact, 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 well wall, and the active hoop effect of the Fe-SMA spiral stirrups on the improvement of the axial tensile performance are not considered, and there is still a certain safety reserve. In summary, the self-prestressed Fe-SMA reinforced UHPC casing is feasible in the 900m deep salt cavern compressed air energy storage well and meets the design requirements.

[0134] The heating temperature of the above-mentioned autoclave is preferably 180-200°C, the pressure is preferably 0.9-1.6MPa, the autoclave curing time is preferably 3-6h, and the recovery stress of Fe-SMA is generally 300MPa-400MPa. After the Fe-SMA axial ribs experience the high temperature environment during autoclave curing, their "shape memory" effect will be activated, and axial pre-stress will be applied to the UHPC casing to prevent the self-prestressed Fe-SMA enhanced UHPC casing from generating excessive axial force during vertical lifting and splicing, resulting in axial tensile cracking of the casing. Similarly, after the Fe-SMA spiral stirrups experience the high temperature environment during autoclave curing, their "shape memory" effect will be activated, thereby applying circumferential uniform pre-stress to the UHPC casing, preventing the self-prestressed Fe-SMA enhanced UHPC casing from generating circumferential alternating stresses during frequent injection and production, causing circumferential tensile cracking of the transport pipeline.

[0135] The Fe-SMA axial ribs in the present invention are not necessarily limited to 8, and can also be increased to 10, 12, etc. The specific number should be determined according to the axial prestressing level required 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. The above Fe-SMA axial ribs and Fe-SMA stirrups are all 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 resistance, and wear resistance, and is an ideal energy storage and transportation material in the CAES field.

[0137] The present invention is mainly used for transmission pipelines in the field of Compressed-Air Energy Storage (CAES). The UHPC casing is autoclaved and cured by an autoclave device, which can promote the hydration reaction of aggregates in the UHPC and improve the compressive strength of the UHPC. At the same time, the high temperature environment in the autoclave can stimulate the Fe-SMA tendons built into the UHPC casing to produce restoring stress, thereby applying prestress to the UHPC casing, achieving the purpose of "killing two birds with one stone". The Fe-SMA axial tendons 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 annular pre-pressure to the UHPC casing to prevent the alternating stress generated by frequent injection and production in the field of CAES from causing cracking of the pipe wall. There are serrated grooves on the end of the UHPC casing. The continuous UHPC casings are connected by a Fe-SMA pipe joint with serrated grooves on the inner side. The Fe-SMA is heated / energized to cause circumferential contraction. The teeth between the outer side of the UHPC casing and the inner side of the Fe-SMA pipe joint are tightly engaged, so that a firm connection between the continuous UHPC casings can be achieved.

[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 belong to the protection scope of the present invention.

Claims

1. A Fe-SMA reinforced UHPC casing for CAES, characterized by: It 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; wherein the central cavity can be used for underground gas transportation in CAES technology; each UHPC casing has a built-in Fe-SMA spiral hoop cage, and each UHPC casing has an external connection portion on the top outer wall and the bottom outer wall; The inner wall of each Fe-SMA pipe joint is provided with an inner 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 greater 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 part 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.

2. The Fe-SMA reinforced UHPC casing for CAES according to claim 1, characterized in that: Each Fe-SMA spiral stirrup cage comprises a Fe-SMA spiral stirrup and a Fe-SMA axial rib uniformly arranged along the circumference of the Fe-SMA spiral stirrup.

3. The Fe-SMA reinforced UHPC casing for CAES according to claim 1, characterized in that: The outer connection part is a serrated convex groove, and the inner connection part is a serrated concave groove; after each Fe-SMA pipe joint is heated by 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.

4. The Fe-SMA reinforced UHPC casing for CAES according to claim 1, 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 by 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.

5. The Fe-SMA reinforced UHPC casing for CAES according to claim 1, 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 by 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.

6. A construction method for Fe-SMA reinforced UHPC casing for CAES, characterized by: The steps include: Step 1, making 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 circumferential direction, thereby forming a Fe-SMA spiral stirrup cage; Step 2, making a Fe-SMA pipe joint: pre-stretching the Fe-SMA strip, and evenly engraving the inner connecting part on its surface; then, bending and rolling the Fe-SMA strip with the inner connecting part engraved into a tube, and making the inner connecting part located inside the tube, thereby forming a Fe-SMA pipe joint; Step 3: Making UHPC casing, including the following steps: Step 3-1, formwork: erecting a UHPC casing template, the UHPC casing template having a circular cylindrical inner cavity of the same shape as the UHPC casing; Step 3-2, placing the Fe-SMA spiral stirrup cage: placing the Fe-SMA spiral stirrup cage manufactured in step 1 in the UHPC casing template erected in step 3-1; Step 3-3, pouring: pouring 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 both have an outer connection portion that matches the inner connection portion; Step 3-5, autoclave curing: remove the UHPC casing template, and place the UHPC casing that has been cured conventionally into an autoclave for autoclave curing; Step 4, UHPC casing assembly: assemble and connect the two adjacent UHPC casings manufactured in step 3 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: Step 4-1, fixing the upper UHPC casing: driving the upper UHPC casing into the pre-drilled pipeline well, and leaving the outer connection part at the bottom of the upper UHPC casing exposed; Step 4-2, initial splicing: first, sleeve 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 in the Fe-SMA pipe joint; Step 4-3, bite splicing: the Fe-SMA pipe joint is heated to stimulate the "shape memory" effect of the Fe-SMA pipe joint to produce circumferential contraction, so that the inner connection part of the Fe-SMA pipe joint is tightly bitten with the outer connection part of the upper UHPC casing and the lower UHPC casing respectively, so as to realize the splicing of two adjacent UHPC casings; Step 4-4: Repeat steps 4-1 to 4-3 to complete the splicing of multiple UHPC casings.

7. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 6, 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 ribs 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).

8. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 7, 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.

9. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 6, 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.

10. The construction method of Fe-SMA reinforced UHPC casing for CAES according to claim 6 or 9, characterized in that: In steps 3-5, when the UHPC casing is autoclaved and cured, on the one hand, the hydration reaction of the aggregate inside the UHPC can be promoted, the density of the material can be improved, and the strength of the UHPC can be enhanced; on the other hand, the high temperature environment during the autoclave curing process can stimulate the Fe-SMA spiral stirrups and Fe-SMA axial ribs built into the UHPC casing, thereby applying circumferential uniform prestress and axial prestress to the UHPC casing, thereby improving its circumferential crack resistance and axial tensile resistance.

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