Modular self-repairing energy-absorbing stone blocking wall based on SMA supports

Abstract

The invention belongs to the technical field of stone blocking walls, discloses a modular self-repairing energy-absorbing stone blocking wall based on SMA supports, and aims to solve the problems of insufficient durability, attenuated energy-absorbing effect and high maintenance cost of an existing cushion layer. The buffering structure of the stone blocking wall comprises a rigid panel and a plurality of SMA energy dissipation supports, the rigidity of the rigid panel is larger than that of the SMA energy dissipation supports, one ends of the SMA energy dissipation supports are fixedly connected with the rigid panel, the other ends of the SMA energy dissipation supports are fixedly connected with a stone blocking wall body, and the stone blocking wall body is fixedly connected with the rigid panel. The SMA energy dissipation support comprises a cylindrical folding cylinder which is made of shape memory alloy. On the basis that falling rocks are effectively intercepted, the energy absorption capacity and the structural durability of the stone blocking wall are remarkably improved; meanwhile, the stone blocking wall has the self-recovery characteristic, permanent deformation of the structure is avoided, the maintenance frequency is reduced, and the service life of the stone blocking wall is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock retaining walls, and particularly relates to a modular self-repairing energy-absorbing rock retaining wall based on SMA bearings. Background Technique

[0002] A rock retaining wall is a structure used to intercept, slow down, and control falling rocks or collapse bodies rolling down from mountainsides, steep slopes, or rocky areas, preventing them from damaging traffic, buildings, and facilities. With the rapid development of transportation facilities such as mountainous areas, railways, and highways, the rockfall disaster has become a hidden danger seriously threatening traffic safety. To reduce the harm of falling rocks to traffic lines, buildings, and personnel, rock retaining walls, as a common protective structure, are widely used in high-risk areas, such as mountain roads, railway lines, and buildings at the bottom of slopes.

[0003] According to different structural forms and functions, rock retaining walls can be divided into various types. Common types include rigid rock retaining walls (gravity type), pile-plate rock retaining walls, and reinforced earth rock retaining walls, etc. Different types of rock retaining walls have their own unique advantages and disadvantages, as follows: Although traditional common rock retaining walls can, to a certain extent, block the harm of falling rocks, they generally have the following several disadvantages: (1) Insufficient energy absorption capacity: When traditional rigid rock retaining walls and pile-plate rock retaining walls encounter a large falling rock impact, their energy absorption capacity is weak, and they are prone to damage or deformation. Even for reinforced earth rock retaining walls, their energy absorption effect is limited, and it is impossible to completely avoid damage under strong impacts.

[0004] (2) Poor adaptability to complex terrains: The installation of traditional rock retaining walls is difficult in some complex terrains (such as narrow valleys and places with large slopes). Due to the strong structural rigidity of these walls, they often cannot adapt to the natural shape of the mountain body, resulting in a waste of installation space and possibly requiring large-scale earthwork excavation.

[0005] To solve the problems of insufficient energy absorption and poor adaptability to complex terrains of traditional rock retaining walls, many studies have begun to focus on the design of buffer cushions for rock retaining walls. The main function of the buffer cushion is to absorb the energy generated by the impact of falling rocks, reduce the damage to the rock retaining wall itself, thereby improving the protection effect and extending the service life. Common types of buffer layers include soil cushions, EPS material buffer layers, and rubber buffer layers, etc. Similarly, each type of buffer layer has its own advantages and disadvantages, as follows: Although the existing buffer layer design can, to a certain extent, improve the overall effect of the rock retaining wall, these traditional buffer materials still have the following problems during continuous impacts: (1) Insufficient durability: With the extension of the service time, problems such as settlement, aging, and decomposition may occur in soil cushions and EPS materials, resulting in a gradual decline in the buffer capacity.

[0006] (2) Energy absorption effect attenuation: Under frequent impacts or extreme weather conditions, the energy absorption effect of some buffer layer materials will gradually weaken, affecting the protection effect of the rockfall retaining wall.

[0007] (3) High maintenance cost: Traditional buffer layers often require regular inspection and replacement, especially in harsh environments, and require a large amount of labor and materials, resulting in high maintenance costs. Summary of the Invention

[0008] In order to solve the problems of insufficient durability, energy absorption effect attenuation and high maintenance cost existing in the existing buffer cushion (or buffer layer), the present invention provides a modular self-repairing energy-absorbing rockfall retaining wall based on SMA bearings, which significantly improves the energy absorption capacity and structural durability of the rockfall retaining wall on the basis of effectively intercepting falling rocks; at the same time, it has self-recovery characteristics to avoid permanent deformation of the structure, reduce the maintenance frequency, and extend the service life of the rockfall retaining wall.

[0009] In order to solve the technical problems, the technical solution adopted by the present invention is: A modular self-repairing energy-absorbing rockfall retaining wall based on SMA bearings, including a rockfall retaining wall body, a buffer structure is arranged on one side of the rockfall retaining wall body facing the mountain slope. It is characterized in that the buffer structure includes a rigid panel and a plurality of SMA energy-dissipating bearings. The stiffness of the rigid panel is greater than that of the SMA energy-dissipating bearings. One end of the SMA energy-dissipating bearing is fixedly connected to the rigid panel, and the other end of the SMA energy-dissipating bearing is fixedly connected to the rockfall retaining wall body. The SMA energy-dissipating bearing includes a telescopic cylinder made of shape memory alloy and formed into a cylindrical shape. Installation plates are fixedly installed at both ends of the telescopic cylinder, and a resistance heating layer for restoring the telescopic cylinder to its original state is coated on the periphery of the telescopic cylinder.

[0010] In some embodiments, the telescopic cylinder is provided with a guiding and protecting mechanism for guiding the deformation and recovery of the telescopic cylinder.

[0011] In some embodiments, the guiding and protecting mechanism includes a first connecting cylinder and a second connecting cylinder which are arranged inside the telescopic cylinder and are cylindrical. A first end cover is arranged at the top of the first connecting cylinder, and a second end cover is arranged at the bottom of the second connecting cylinder. The lower end of the first connecting cylinder extends into the second connecting cylinder and is in sliding contact with the second connecting cylinder. Vertical holes and horizontal holes are formed inside both the first connecting cylinder and the second connecting cylinder, and the vertical holes and the horizontal holes form a wire passing channel. A clamping groove is formed on the outer wall of the first connecting cylinder, and a contact piece is arranged in the clamping groove. A contact head for contacting the contact piece is installed in the horizontal hole of the second connecting cylinder. One section of the wire of the resistance heating layer is introduced into the wire passing channel inside the first connecting cylinder and is electrically connected to the contact piece, and the other section of the wire of the resistance heating layer is introduced into the wire passing channel inside the second connecting cylinder and is connected to the contact head. When the SMA energy dissipation bearing is not impacted and deformed, the contact head and the contact piece are not in contact. When the SMA energy dissipation bearing is impacted and deformed, the contact head and the contact piece are in contact with each other.

[0012] In some embodiments, a return spring is arranged between the lower end of the first connecting cylinder and the second end cover, and a return spring is arranged between the upper end of the second connecting cylinder and the first end cover. The initial lengths of the return springs at the ends of the first connecting cylinder and the second connecting cylinder are both greater than the deformation amount of the telescopic cylinder.

[0013] In some embodiments, the guiding and protecting mechanism further includes a third connecting cylinder and a fourth connecting cylinder which are arranged around the telescopic cylinder and are cylindrical. The upper end of the third connecting cylinder is connected to the mounting plate at the upper end of the telescopic cylinder, and the fourth connecting cylinder is connected to the mounting plate at the lower end of the telescopic cylinder. The upper end of the fourth connecting cylinder extends into the third connecting cylinder and is in sliding contact with the third connecting cylinder. A return spring is arranged between the lower end of the third connecting cylinder and the lower mounting plate, and a return spring is arranged between the upper end of the fourth connecting cylinder and the upper mounting plate. The initial lengths of the return springs at the ends of the third connecting cylinder and the fourth connecting cylinder are both greater than the deformation amount of the telescopic cylinder.

[0014] In some embodiments, grooves for placing return springs are formed on the sides of the first connecting cylinder and the third connecting cylinder facing the telescopic cylinder.

[0015] In some embodiments, the rigid panel is formed by splicing a plurality of panel units. Protrusions and sliding grooves are respectively arranged on four side surfaces of each panel unit. The protrusions are arranged on two opposite side surfaces of the panel unit, and the sliding grooves are arranged on two opposite side surfaces of the panel unit. The thickness of the protrusion is less than the width of the sliding groove so that the protrusion can slide in the sliding groove along the direction perpendicular to the panel unit, and the difference between the width of the sliding groove and the thickness of the protrusion is less than the deformation amount of the telescopic cylinder. The protrusions of the panel units are adapted to the sliding grooves on the adjacent panel units. At least one SMA energy dissipation bearing is arranged behind each panel unit.

[0016] In some embodiments, at least three guide rods are fixedly installed on the mounting plate of the telescopic cylinder, through holes are provided at positions corresponding to the mounting plate on the panel unit, and the guide rods pass through the through holes of the panel unit.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The modular self-repairing energy-absorbing rock retaining wall based on the SMA bearing of the present invention is provided with a buffer structure on the side facing the mountain slope surface, and the buffer structure is made of a rigid panel and an SMA energy-consuming bearing. When a collapse occurs on the mountain slope surface, first, the rigid panel is used to bear the impulse, and then the rigid panel transfers the impact force to the SMA energy-consuming bearing. After the SMA energy-consuming bearing buffers and releases energy, it is transferred to the rock retaining wall body, thereby playing a role in protecting the rock retaining wall body and improving the service life and durability of the rock retaining wall body. At the same time, the SMA energy-consuming bearing has excellent self-recovery characteristics; compared with the existing buffer layer, it has the advantages of good durability, low maintenance cost, and low repair frequency, and there is no problem of attenuation of the energy-absorbing effect of the SMA energy-consuming bearing.

[0018] The present invention is provided with a guiding and protecting mechanism for guiding the deformation and recovery of the telescopic cylinder for the telescopic cylinder. The guiding and protecting mechanism plays a guiding and protecting role in the deformation and recovery of the telescopic cylinder, so that the SMA telescopic cylinder can be guided to a certain extent during the deformation and recovery process, thereby avoiding irreversible deformation of the telescopic cylinder, and further improving the durability of the SMA energy-consuming bearing.

[0019] The structural design of the first connecting cylinder and the second connecting cylinder, the first end cover and the second end cover of the guiding and protecting mechanism of the present invention. The mutually sleeved first connecting cylinder and the second connecting cylinder can provide a certain supporting force for the rigid panel (each panel unit), so that there is no need for the telescopic cylinder to provide a force for the stability of the rigid panel, enabling the telescopic cylinder to play its role of buffering and releasing energy. More importantly, when the rigid panel (panel unit) squeezes the telescopic cylinder to deform, the first connecting cylinder and the second connecting cylinder can automatically turn on the resistance heating layer during the relative movement, so as to heat the telescopic cylinder, so that the telescopic cylinder can quickly return to its original state after deformation, in order to be prepared to offset the impact force of the next falling rock, thus conforming to the actual situation of the rock mass collapse. At the same time, the ability of the telescopic cylinder to automatically heat and recover does not require on-site operation by staff, further reducing the maintenance frequency.

[0020] The reset springs of the first connecting cylinder and the second connecting cylinder of the present invention can, in addition to providing a certain supporting effect for the restoration of the telescopic cylinder (i.e., after the reset springs are compressed, they can release a certain elastic force to push the rigid panel in the reverse direction, so as to facilitate the self-restoration of the telescopic cylinder after heating), also buffer the impact force of falling rocks together with the telescopic cylinder, further improve the impact resistance of the buffer structure, and ultimately extend the service life of the rock retaining wall body.

[0021] In addition to guiding the deformation and restoration of the telescopic cylinder, the structural design of the third connecting cylinder and the fourth connecting cylinder of the guiding and protecting mechanism of the present invention can also play a certain protective role for the entire SMA energy dissipation bearing.

[0022] In the present invention, the rigid panel is composed of several panel units spliced together, which is convenient for the installation of the rigid panel; at the same time, each panel unit can form an independent and unified whole. When a certain panel unit is impacted by a falling rock, the panel unit uses the SMA energy dissipation bearing behind it for buffering. As the displacement of the panel unit exceeds the distance between the protrusion and the card slot, the panel unit transmits the impact force to the adjacent panel unit, so as to use the adjacent panel unit to jointly buffer the impact force of the falling rock. In this way, each panel unit can not only buffer the impact force of the falling rock alone, but also jointly buffer the impact force of the panel unit with the remaining panel units. This makes the stress situation of the entire buffer structure closer to the actual collapse situation of the rock and soil mass, so as to play a better buffering role and improve the protection effect on the rock retaining wall body.

[0023] Through the action of the guide rod, the present invention can not only play a certain stabilizing role for the panel unit, but also play a guiding role for the movement of the panel unit, ensuring the smoothness of the panel unit's movement under the impact of falling rocks and preventing the problem of the panel unit tilting under the impact of falling rocks; on the one hand, it enables the panel unit to smoothly transmit the impact force to the adjacent panel unit, and on the other hand, it also ensures the stability of the assembled rigid panel.

[0024] In addition to the above advantages, the present invention also has the following advantages: The rigid panel, SMA energy dissipation bearing and guiding and protecting mechanism can all be manufactured using factory standardization. While reducing the transportation cost, it also significantly shortens the construction period, reduces the labor intensity, and improves the construction efficiency; it is applicable to areas with complex terrain and limited construction conditions.

[0025] It is especially suitable for areas with limited terrain and narrow space. Through its assembled structure and flexible structure adjustment, it can provide an efficient protection solution in a limited space. This strong adaptability makes the present invention have broad application potential in high-risk areas such as mountain roads and railway lines. Description of the Drawings

[0026] Figure 1 It is a structural schematic diagram of an existing rock retaining wall, which is a combination of a gravity rock retaining wall and a soil cushion layer; Figure 2 It is a structural schematic diagram of an existing rock retaining wall, which is a combination of a gravity rock retaining wall and an EPS cushion layer; Figure 3 It is a structural schematic diagram of an existing rock retaining wall, which is a combination of a pile-plank wall rock retaining wall and an EPS cushion layer; Figure 4 It is a structural schematic diagram of an existing rock retaining wall, which is a combination of a pile-plank wall rock retaining wall and a soil cushion layer; Figure 5 It is a structural schematic diagram of an embodiment of the present invention; Figure 6 It is a structural schematic diagram of an SMA energy dissipation bearing arranged on a rigid panel; Figure 7 It is a longitudinal sectional structural schematic diagram of an embodiment of the SMA energy dissipation bearing of the present invention; Figure 8 It is a transverse sectional structural schematic diagram of an embodiment of the SMA energy dissipation bearing of the present invention; Figure 9 Structural schematic diagram of an embodiment of the SMA energy dissipation bearing of the present invention; Figure 10 For Figure 9 The partial enlarged view schematic diagram at position A in Figure 11 Structural schematic diagram of another embodiment of the SMA energy dissipation bearing of the present invention; Figure 12 Structural schematic diagram of an embodiment of the rigid panel of the invention; Markings in the figure: 1. Rock retaining wall body, 2. Rigid panel, 21. Panel unit, 22. Slide groove, 23. Protrusion, 24. Through hole, 3. SMA energy dissipation bearing, 31. Telescopic cylinder, 32. Mounting plate, 321. Bolt hole, 33. Resistance heating layer, 34. Heat insulation and heat preservation layer, 35. First connecting cylinder, 351. Groove, 352. Card slot, 353. Contact piece, 36. Second connecting cylinder, 361. Contact head, 37. Wire passing channel, 371. Vertical hole, 372. Horizontal hole, 38. Wire passing hole, 39. Return spring, 310. Third connecting cylinder, 311. Fourth connecting cylinder, 312. Guide rod, 4. Panel support, 5. Track groove. Detailed implementation manners

[0027] The present invention will be further described below in conjunction with embodiments. The described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0028] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention; the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance; in addition, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] Combined with the attached Figure 1 to the attached Figure 4 is the existing rock retaining wall structure. As mentioned in the background art of the present invention, although the existing buffer layer design can improve the overall effect of the rock retaining wall to a certain extent, the following problems will still occur in these traditional buffer materials during the continuous impact process: (1) Insufficient durability: As the service time extends, problems such as settlement, aging, and decomposition may occur in the soil cushion layer and EPS materials, resulting in a gradual decline in the buffering ability.

[0030] (2) Deterioration of the energy absorption effect: Under frequent impacts or extreme weather conditions, the energy absorption effect of some buffer layer materials will gradually weaken, affecting the protection effect of the rock retaining wall.

[0031] (3) Higher maintenance costs: Traditional buffer layers often require regular inspections and replacements, especially in harsh environments. The maintenance costs are relatively high and may require a large amount of labor and materials.

[0032] Combined with the attached Figure 5 to the attached Figure 12, the modular self-repairing energy-absorbing rock retaining wall based on SMA bearings of the present invention includes a rock retaining wall body 1. A buffer structure is provided on one side of the rock retaining wall body 1 facing the mountain slope. The buffer structure includes a rigid panel 2 and a plurality of SMA energy-dissipating bearings 3. The rigidity of the rigid panel 2 is greater than that of the SMA energy-dissipating bearings 3. One end of the SMA energy-dissipating bearing 3 is fixedly connected to the rigid panel 2, and the other end of the SMA energy-dissipating bearing 3 is fixedly connected to the rock retaining wall body 1. The SMA energy-dissipating bearing 3 includes a telescopic cylinder 31 made of shape memory alloy and in a cylindrical shape. Mounting plates 32 are fixedly installed at both ends of the telescopic cylinder 31 respectively. A resistive electrothermal layer 33 is coated on the periphery of the telescopic cylinder 31, and a heat insulation and heat preservation layer 34 is coated on the periphery of the resistive heating layer 33. Among them, the mounting plates 32 at both ends of the telescopic cylinder 31 are respectively used to connect with the rock retaining wall body 1 and the rigid panel 3, so as to install the SMA energy-dissipating bearing 3 between the rigid panel 2 and the rock retaining wall body 1.

[0033] In the specific implementation process, bolt holes 321 are provided on the mounting plate 32, and screws are provided for the bolt holes 321. The SMA energy-dissipating bearing is installed between the rigid panel 2 and the rock retaining wall body 1 through the screws.

[0034] In the specific implementation process, at least two panel bearings 4 are arranged below the rigid panel 2, and the panel bearings 4 are used to bear the weight of the entire rigid panel 2. Preferably, a track groove 5 is laid on the ground, and the lower end of the panel bearing 4 is adapted to the track groove 5. Thus, when the rigid panel 5 slides under the impact of falling rocks, the track groove 5 provides a guiding function for the movement of the rigid panel 2, and at the same time reduces the friction force when the rigid panel 2 moves, ensuring that the rigid panel 2 moves synchronously with the deformation compression and recovery of the SMA energy-dissipating bearing.

[0035] During the use of the present invention, when the rock and soil mass on the mountain slope rolls down, it first contacts the rigid panel. Since the rigid panel does not break or undergo significant deformation, the rigid panel transmits the impact force to a plurality of SMA energy-dissipating bearings. The SMA energy-dissipating bearing contains a telescopic cylinder made of shape memory alloy. Each telescopic cylinder deforms after being impacted and buffers the impact force, and finally transmits the remaining impact force to the rock retaining wall body. Thus, the SMA energy-dissipating bearing plays the role of energy dissipation and buffering, and finally plays the role of protecting the rock retaining wall body.

[0036] That is to say, the rigid panel provides a preliminary impact force dispersion and interception function, and the SMA energy-dissipating bearing, relying on its superelasticity and self-recovery characteristics, absorbs energy during impact and restores its shape through heating, avoiding permanent deformation of the structure, reducing the maintenance frequency, and prolonging the service life of the rock retaining wall body.

[0037] In the specific implementation process, the rigid panel is made of high-strength steel plates (such as Q460, Q690), or the rigid panel is cast with ultra-high performance concrete.

[0038] For high-impact areas (i.e., large amounts of rock and soil collapses): The telescopic cylinder of the present invention is made of the following raw materials by weight: 64-66 parts of Cu; 29-31 parts of Zn; 4-6 parts of Al; the activation temperature of the telescopic cylinder is 70-80 °C; the tensile strength of the telescopic cylinder is greater than or equal to 400 MPa, the yield strength of the telescopic cylinder is greater than or equal to 300 MPa, the elastic modulus of the telescopic cylinder is 70-100 MPa; the impact toughness of the telescopic cylinder is 10-20 J / cm²; the strain of the telescopic cylinder is 5-8%.

[0039] For low-impact areas (i.e., relatively small amounts of rock and soil collapses): The telescopic cylinder of the present invention is made of the following raw materials by weight: 74-76 parts of Cu; 19-21 parts of Zn; 4-6 parts of Al; the activation temperature of the telescopic cylinder is 50-70 °C; the tensile strength of the telescopic cylinder is greater than or equal to 300 MPa, the yield strength of the telescopic cylinder is greater than or equal to 250 MPa, the elastic modulus of the telescopic cylinder is 70-100 MPa; the impact toughness of the telescopic cylinder is 10-20 J / cm²; the strain of the telescopic cylinder is not less than 3-5%.

[0040] The activation temperature refers to the heating temperature of the resistance heating layer. At this temperature, the telescopic cylinder can restore its original state. Generally, the telescopic cylinder made of shape memory alloy can be quickly restored after heating for 10-15 minutes, so as to prepare for the next buffer.

[0041] The present invention provides two options (i.e., high-impact areas and low-impact areas) according to the rolling situation of the collapsed rocks in the area where the retaining wall body is arranged, so as to select a suitable SMA energy dissipation bearing according to the actual situation.

[0042] The manufacturing method of the telescopic cylinder of the present invention includes the following: (1) Material configuration, select the corresponding ratio according to high-impact areas and low-impact areas; in the specific implementation process, high-purity copper, zinc and aluminum are preferably selected as raw materials. For the telescopic cylinder used in high-impact areas, the proportion of copper is relatively high and the proportion of zinc is high to ensure a higher phase change temperature.

[0043] (2) Melting Selection of melting furnace: Commonly, an electric arc furnace or an induction furnace is used for melting. In the manufacturing process of the present invention, it is more appropriate to select an induction furnace because the induction furnace has a uniform heating temperature and high control accuracy, and can avoid excessive oxidation of alloy components.

[0044] Melting temperature: Heat copper, zinc, and aluminum to their melting temperatures; Melting temperature of copper: 1085°C Melting temperature of zinc: 419°C Melting temperature of aluminum: 660°C, Among them, due to the relatively high melting point of copper, first heat the copper to 1200°C - 1300°C, then add zinc and aluminum, and maintain at about 1200°C to ensure that each component is fully dissolved and a uniform liquid alloy is formed.

[0045] Adjustment of alloy composition: During the melting process, adjust the composition by adding appropriate alloying elements to ensure compliance with the target ratio. Adjust the composition ratio of the copper alloy by adding zinc (Zn) and aluminum.

[0046] Removal of impurities treatment: During the melting process, it is necessary to control the oxygen content in the furnace gas to avoid the formation of oxides. Oxides in the alloy can be removed by adding deoxidizers (such as silicon or aluminum).

[0047] Casting: After melting is completed, pour the liquid alloy into a pre-designed mold. The design of the mold needs to be based on the shape and use of the final product. Usually, steel molds or graphite molds are used to ensure that the alloy can obtain the required crystal structure when cooling.

[0048] (3) Solution treatment Solution temperature: Solution treatment is to heat the cast alloy (i.e., the alloy taken out of the mold in the last step of step (2)) to a certain temperature and hold for a certain time to make the alloy composition uniform. For Cu-Zn-Al alloy, the solution temperature is usually 850°C to 900°C.

[0049] Solution time: The solution treatment time is usually 1 - 2 hours to ensure uniform internal composition of the alloy and refined grains.

[0050] Rapid cooling: After solution, the alloy needs to be water quenched to rapidly reduce the temperature, retain the high-temperature structure of the alloy, and avoid the formation of precipitation phases.

[0051] (4) Heat treatment (aging treatment) Aging treatment temperature: Aging treatment is used to improve the strength and hardness of the alloy. For Cu-Zn-Al alloy, the aging treatment is usually carried out between 300°C and 400°C for 2 to 4 hours.

[0052] Adjustment of Aging Time and Temperature: During the aging treatment process, the proportion of aluminum has a significant impact on the formation of hardness and shape memory effect. Higher aging temperature and longer aging time contribute to improving the hardness and recovery ability of the alloy.

[0053] (5) Cold Working (Rolling or Drawing) Rolling: After the alloy is cooled and aged, the alloy can be processed by rolling or drawing to form the desired shape. During cold working, attention should be paid to the deformation rate to avoid damage to the alloy due to excessive stretching or compression.

[0054] Cold Working Temperature: Cold working is usually carried out at room temperature. However, if a large deformation is required, it can be appropriately heated to 200°C to 300°C to improve the workability of the alloy.

[0055] Among them, after obtaining the telescopic cylinder through cold working, quality inspection and performance testing are carried out: Mechanical Property Testing: Tensile test, yield strength, tensile strength and other tests are carried out to ensure that the alloy has sufficient strength and elasticity.

[0056] Shape Memory Effect Testing: Through temperature cycle testing, it is ensured that the alloy can return to its original shape after multiple temperature changes.

[0057] Impact Resistance Testing: Impact test is carried out to ensure that the alloy can effectively absorb energy and return to its shape when facing a large impact force.

[0058] In some embodiments, the telescopic cylinder is provided with a guiding and protecting mechanism for guiding the deformation and recovery of the telescopic cylinder. The guiding and protecting mechanism plays a guiding and protecting role in the deformation and recovery of the telescopic cylinder, so that the SMA telescopic cylinder can be guided to a certain extent during the deformation and recovery process, thereby avoiding irreversible deformation of the telescopic cylinder, and further improving the durability of the SMA energy dissipation bearing.

[0059] In some embodiments, the guiding and protecting mechanism includes a first connecting cylinder 35 and a second connecting cylinder 36, both of which are cylindrical and arranged inside the telescopic cylinder 31. A first end cover is provided at the top of the first connecting cylinder 35, and a second end cover is provided at the bottom of the second connecting cylinder 36. The lower end of the first connecting cylinder 35 extends into the second connecting cylinder 36 and is in sliding contact with the second connecting cylinder 36. Vertical holes 371 and transverse holes 372 are formed inside both the first connecting cylinder 35 and the second connecting cylinder 36, and the vertical holes 372 and the transverse holes 372 form a wire passing channel 37. A clamping groove 352 is formed on the outer wall of the first connecting cylinder 35, and a contact piece 353 is arranged in the clamping groove 352. A contact head 361 for contacting the contact piece 353 is installed in the transverse hole 372 of the second connecting cylinder 36. One section of the wire of the resistance heating layer 33 is introduced into the wire passing channel 37 inside the first connecting cylinder 35 and is electrically connected to the contact piece 353, and the other section of the wire of the resistance heating layer 33 is introduced into the wire passing channel 37 inside the second connecting cylinder 36 and is connected to the contact head. When the SMA energy dissipation bearing 3 is not impacted and deformed, the contact head 361 and the contact piece 353 are not in contact. When the SMA energy dissipation bearing 3 is impacted and deformed, the contact head 361 and the contact piece 353 are in contact with each other.

[0060] That is to say, when the SMA energy dissipation bearing is in the initial position, the contact head on the second connecting cylinder is not in contact with the contact piece on the first connecting cylinder. When the SMA energy dissipation bearing is extruded and deformed, the contact head on the second connecting cylinder is in contact with the contact piece on the first connecting cylinder, so that the wire of the resistance heating layer is energized and electrical energy is input into the resistance heating layer. Among them, the resistance heating layer needs to be energized by two wires (one positive wire and one negative wire) to work. The present invention can control whether the resistance heating layer works by controlling the on-off of one of the wires. Those skilled in the art can understand and comprehend this, and will not be elaborated here.

[0061] In some embodiments, the first end cover and the mounting plate 32 above the telescopic cylinder 31 are of an integral structure, and the second end cover and the mounting plate 32 below the telescopic cylinder 31 are of an integral structure. In some embodiments, the first connecting cylinder 35 is directly installed on the mounting plate 32 above the telescopic cylinder 31, and the second connecting cylinder 36 is directly installed on the mounting plate below the telescopic cylinder.

[0062] The present invention can control the working state of the resistance heating layer by using the working state of the SMA energy dissipation bearing. That is, when the SMA energy dissipation bearing squeezes the rigid panel under the impact of a falling rock, the SMA energy dissipation bearing utilizes its own deformation ability to offset and buffer the impact force of the falling rock, thereby reducing the impact on the retaining wall body and achieving the purpose of protecting the retaining wall body. On the other hand, during the deformation process of the SMA energy dissipation bearing, the first connecting cylinder moves towards the second connecting cylinder, causing the contact piece on the first connecting cylinder to come into contact with the contact head on the second connecting cylinder, so that the two ends of the wire of the resistance heating layer are connected, and the wire of the resistance heating layer can be energized, and then the resistance heating layer can be heated and energized to work; it takes a certain amount of time for the resistance heating layer to heat up and for the telescopic cylinder made of shape memory alloy to return to its original state after being heated. However, the impact force borne by the SMA energy dissipation bearing is instantaneous (i.e., the deformation time of the telescopic cylinder is relatively fast). Therefore, the operation of the resistance heating layer 33 does not affect the buffering effect of the telescopic cylinder 31 in the SMA energy dissipation bearing. The telescopic cylinder of the SMA energy dissipation bearing can be heated automatically without the need for staff to reach the site, enabling the SMA energy dissipation bearing to restore its own elastic function to resist the impact of the next falling rock, thereby maximizing the protection of the retaining wall body.

[0063] Since the rolling (collapse) of rocks on the mountain slope generally occurs multiple times and is not continuous (usually with a certain time interval), that is, it does not all roll down at once. More often, a smaller part of the rock mass rolls down first, then a large-scale rock mass collapse occurs, and finally a part of the rock mass rolls down. When a rock mass collapse occurs, due to the distance, it generally takes some time for the staff to reach the collapse site. At this time, if the SMA energy dissipation bearing cannot be heated in time to restore its elastic deformation ability, then the SMA energy dissipation bearing cannot buffer and release the energy of the subsequent collapsing rock mass, and the subsequent collapse of the rock mass can only be transmitted to the retaining wall body, resulting in the easy damage of the retaining wall body. However, in the present invention, when the SMA energy dissipation bearing 3 deforms, it can automatically connect the resistance heating layer 33 to heat and work, enabling the SMA energy dissipation bearing 3 to restore its original state (i.e., having a certain deformation buffering ability), preparing for resisting the impact of the next falling rock, thereby maximizing the buffering of the impact force transmitted to the retaining wall body 1, improving the service life of the retaining wall body 1, and at the same time reducing its own maintenance cost.

[0064] Among them, in the specific implementation process, in order to protect the wires of the resistance heating layer 33, wire passing holes 38 are also provided on the first end cover and the second end cover. One section of the wire of the resistance heating layer 33 first enters the wire passing hole of the first end cover and then penetrates into the wire passing channel 37 of the first connecting cylinder 35; while the other section of the wire of the resistance heating layer first enters the wire passing hole 38 of the second end cover and then penetrates into the wire passing channel 37 of the second connecting cylinder 36. On the one hand, the wire passing holes on the first end cover and the second end cover and the wire passing channels of the first connecting cylinder and the second connecting cylinder are used for protection to prevent the wires of the resistance heating layer from being squeezed and damaged during the telescopic process of the SMA energy dissipation bearing; on the other hand, the wire passing holes and the wire passing channels also form a space for accommodating the wires of the resistance heating layer.

[0065] In the specific implementation process, one end of the wire passing holes on the first end cover and the second end cover is aligned with the position of the resistance heating layer, and the other ends of the wire passing holes on the first end cover and the second end cover are respectively aligned with the wire passing channels of the first connecting cylinder and the second connecting cylinder. Among them, when the first end cover and the mounting plate 32 above the telescopic cylinder 31 are of an integral structure, or the first connecting cylinder 35 is directly mounted on the mounting plate 32 above the telescopic cylinder 31; and the second end cover and the mounting plate below the telescopic cylinder are of an integral structure, or the second connecting cylinder 36 is directly mounted on the mounting plate 32 below the telescopic cylinder; in order to facilitate the passing of the wires of the resistance heating layer, the mounting plate 32 is also provided with a wire passing hole 38.

[0066] In the present invention, a first connecting cylinder and a second connecting cylinder are respectively arranged inside the telescopic cylinder, and the contact pieces on the first connecting cylinder correspond to the contact heads on the second connecting cylinder. On the one hand, the first connecting cylinder and the second connecting cylinder can guide the deformation of the SMA energy dissipation bearing, and the mutually sleeved first connecting cylinder and second connecting cylinder can provide a certain supporting force for the rigid panel (each panel unit), so that there is no need for the telescopic cylinder to provide a force for the stability of the rigid panel, enabling the telescopic cylinder to play its role of buffering and energy release. More importantly, when the rigid panel (panel unit) squeezes the telescopic cylinder to deform, the first connecting cylinder and the second connecting cylinder can automatically turn on the resistance heating layer during the relative movement, so as to heat the telescopic cylinder, so that the telescopic cylinder can quickly return to its original state after deformation, in order to be prepared to offset the impact force of the next rockfall, thus fitting the actual situation of the rock mass collapse. At the same time, the ability of the telescopic cylinder to automatically heat and recover does not require the staff to operate on-site, further reducing the maintenance frequency.

[0067] In some embodiments, a return spring 39 is provided between the lower end of the first connecting cylinder 35 and the second end cover, and a return spring 39 is provided between the upper end of the second connecting cylinder 36 and the first end cover. The initial lengths of the return springs 39 at the ends of the first connecting cylinder and the second connecting cylinder are both greater than the deformation amount of the telescopic cylinder 31. Thus, the designs of the first connecting cylinder and the second connecting cylinder will not affect the deformation of the telescopic cylinder itself. At the same time, the return springs on the first connecting cylinder and the second connecting cylinder can also jointly offset the impact force of the falling rocks with the telescopic cylinder, buffer and release the impact force, and further improve the protection ability of the rock retaining wall body.

[0068] In the specific implementation process, generally, the elastic modulus of the telescopic cylinder made of shape memory alloy is certain. Then, by matching return springs 39 with different stiffness coefficients, the buffering capabilities of individual SMA energy dissipating bearings 3 can be made different, so as to be used in different scenarios. Thus, while ensuring the buffering and protection effect, the cost of the SMA energy dissipating bearing is reduced (springs with different stiffness coefficients have different prices).

[0069] In some embodiments, the guiding and protecting mechanism further includes a third connecting cylinder 310 and a fourth connecting cylinder 311 which are arranged around the telescopic cylinder 31 and are in a cylindrical shape. The upper end of the third connecting cylinder 311 is connected to the mounting plate 32 at the upper end of the telescopic cylinder 31, the fourth connecting cylinder 311 is connected to the mounting plate 32 at the lower end of the telescopic cylinder 31, and the upper end of the fourth connecting cylinder 311 extends into the interior of the third connecting cylinder 310 and contacts the third connecting cylinder 310; a return spring 39 is provided between the lower end of the third connecting cylinder 310 and the lower mounting plate 32, and a return spring 39 is provided between the upper end of the fourth connecting cylinder 311 and the upper mounting plate 32; the initial lengths of the return springs at the ends of the third connecting cylinder and the fourth connecting cylinder are both greater than the deformation amount of the telescopic cylinder.

[0070] The present invention protects the inner wall of the telescopic cylinder through the first connecting cylinder and the second connecting cylinder, and protects the outer wall of the telescopic cylinder through the third connecting cylinder and the fourth connecting cylinder. On the one hand, it ensures that the deformation of the telescopic cylinder will not undergo irreversible deformation under the action of the impact force. On the other hand, the return springs on each connecting cylinder can play a buffering role together with the telescopic cylinder. At the same time, the acting force of the return spring is used to guide the telescopic cylinder to restore its original state after heating, improving the service life of the telescopic cylinder. And the sleeved structures of the first connecting cylinder and the second connecting cylinder, and the sleeved structures of the third connecting cylinder and the fourth connecting cylinder can provide sufficient stiffness for the entire SMA bearing, so as to support the rigid panel 2.

[0071] In some embodiments, a groove 351 for placing a return spring 39 is formed on one side of the first connecting cylinder 35 and the third connecting cylinder 39 facing the telescopic cylinder 31. Since the second connecting cylinder and the fourth connecting cylinder are relatively thin in themselves, the space at the upper ends of the second connecting cylinder and the fourth connecting cylinder is small. By forming grooves on the first connecting cylinder and the third connecting cylinder, the space at the upper ends of the second connecting cylinder and the fourth connecting cylinder can be enlarged, so as to place a return spring with a larger size, thereby facilitating the improvement of the impact resistance force.

[0072] In the specific implementation process, there is a gap between the second connecting cylinder and the inner wall of the telescopic cylinder, and there is a gap between the fourth connecting cylinder and the outer wall of the telescopic cylinder to facilitate the installation of the resistive heating layer. That is to say, when the third connecting cylinder and the fourth connecting cylinder are provided, the resistive heating layer is arranged on one side of the third connecting cylinder and the fourth connecting cylinder facing the telescopic cylinder, and the resistive heating layer covers the outer wall of the telescopic cylinder to facilitate heating the telescopic cylinder. The gap between the second connecting cylinder 36 and the telescopic cylinder 31 is to provide sufficient space for the deformation of the telescopic cylinder 31.

[0073] In some embodiments, the heat insulation layer is arranged on the inner walls of the third connecting cylinder and the fourth connecting cylinder, so that the third connecting cylinder and the fourth connecting cylinder can be used to protect the resistive heating layer and the heat insulation layer.

[0074] In some embodiments, the heat insulation layer is also arranged on one side of the first connecting cylinder and the second connecting cylinder facing the telescopic cylinder, so as to further reduce heat dissipation.

[0075] In some embodiments, the rigid panel 2 is formed by splicing a plurality of panel units 21. Protrusions 23 and chutes 22 are respectively arranged on the four side surfaces of each panel unit 21. The protrusions 23 are arranged on two opposite side surfaces of the panel unit 21, and the chutes 22 are arranged on two opposite side surfaces of the panel unit 21. The thickness of the protrusion 23 is less than the width of the chute 22 so that the protrusion 23 can slide in the chute 22 along a direction perpendicular to the panel unit, and the difference between the width of the chute 22 and the thickness of the protrusion 23 is less than the deformation amount of the telescopic cylinder 31; the protrusions 23 of the panel unit 21 are adapted to the chutes 22 on the adjacent panel unit 21; at least one SMA energy dissipation support 3 is arranged behind each panel unit 21.

[0076] In the specific implementation process, the card slots are arranged along the side surface of the panel unit and penetrate the entire side surface, so as to facilitate the assembly of the panel unit.

[0077] The rigid panel of the present invention is composed of several panel units spliced together, which is convenient for the installation of the rigid panel; at the same time, each panel unit can form an independent and unified whole. When a certain panel unit is impacted by a falling rock, the panel unit uses the SMA energy dissipation bearing behind it for buffering. When the displacement of the panel unit exceeds the distance between the protrusion and the card slot, the panel unit transfers the impact force to the adjacent panel unit, so as to use the adjacent panel unit to jointly buffer the impact force of the falling rock, so that each panel unit can not only buffer the impact force of the falling rock alone, but also buffer the impact force of the panel unit together with the other panel units. Because the collapse of the falling rock on the mountain slope is uncertain, when the impact amount of the falling rock is small (for example, when the collapse amount is small or the collapse position is low), only the SMA energy dissipation bearings behind some panel units can play a role in buffering the impact force; if the rigid panel is a whole structure, when the impact force is small, the impact force cannot drive all the SMA energy dissipation bearings to buffer, so that the SMA energy dissipation bearings cannot play a buffering role. When the impact amount of the falling rock is large, the 1 or more SMA energy dissipation bearings that first come into contact with the falling rock play a buffering role. When the 1 or more SMA energy dissipation bearings are not enough to resist, they drive more SMA energy dissipation bearings to act together to play a buffering role (that is, let the SMA energy dissipation bearings behind the adjacent panel units play a buffering role together) to offset and buffer the impact of the falling rock, so that the present invention can not only buffer the falling rock with a small impact amount, but also buffer the falling rock with a large impact amount, improving the protection effect on the retaining wall body.

[0078] In the prior art, whether it is a buffer layer made of EPS material or rubber material, the elastic modulus of the EPS material and the rubber material is certain, and only by stacking the material thickness can the overall buffering performance be improved. The buffering effects between regions are independent of each other (for example, the buffering performance of the EPS and rubber layers in the lower layer cannot be utilized by the EPS and rubber layers in the upper layer). The EPS material and the rubber material can only play a buffering role at the stacking position, so that local buffering failure is likely to occur when dealing with large-area rock and soil body collapses, and the impact force on the retaining wall body is large and it is easy to be damaged.

[0079] The rigid panel of the present invention is composed of panel units in a splicing manner, and each panel unit can not only offset the impact alone, but also drive other panel units to jointly bear the impact, so that the SMA energy dissipation bearing can adapt according to the size of the collapse amount, so as to offset the uncontrollable rock mass collapse, and finally improve the protection effect on the retaining wall body.

[0080] In some embodiments, at least three guide rods 312 are fixedly installed on the mounting plate 32 of the telescopic cylinder 31. A through hole 24 is provided at a position corresponding to the mounting plate 32 on the panel unit 21, and the guide rod 312 passes through the through hole 24 of the panel unit. Through the action of the guide rod 312, the present invention can not only play a certain role in stabilizing the panel unit, but also play a guiding role for the movement of the panel unit, ensuring the smooth movement of the panel unit under the impact of falling rocks without tilting of the panel unit under the impact of falling rocks. On the one hand, it enables the panel unit to transfer the impact force to the adjacent panel unit smoothly, and on the other hand, it also ensures the stability of the rigid panel assembled as a whole.

[0081] In the specific implementation process, the guide rod passes through the through hole of the panel unit, and the outer end surface of the guide rod is flush with the outer side surface of the panel unit (the side surface facing away from the SMA energy dissipation support), or there is a certain distance between the outer end surface of the guide rod and the through hole of the panel unit, so as to prevent the falling rocks from directly impacting the guide rod and damaging the guide rod.

Claims

1. A modular self-repairing energy-absorbing rock retaining wall based on SMA bearings, comprising a rock retaining wall body, wherein a buffer structure is arranged on one side of the rock retaining wall body facing the mountain slope surface, and is characterized in that, The buffer structure includes a rigid panel and a number of SMA energy dissipation bearings. The stiffness of the rigid panel is greater than that of the SMA energy dissipation bearings. One end of the SMA energy dissipation bearing is fixedly connected to the rigid panel, and the other end of the SMA energy dissipation bearing is fixedly connected to the retaining wall body. The SMA energy dissipation bearing includes a telescopic cylinder made of shape memory alloy and in a cylindrical shape. Mounting plates are fixedly installed at both ends of the telescopic cylinder, and a resistance heating layer for restoring the telescopic cylinder to its original state is coated on the periphery of the telescopic cylinder.

2. The modular self-healing energy-absorbing boulder retaining wall based on SMA bearings according to claim 1, characterized in that, The telescopic cylinder is provided with a guiding and protecting mechanism for guiding the deformation and restoration of the telescopic cylinder.

3. The modular self-healing energy-absorbing rockfall retaining wall based on SMA bearings according to claim 2, characterized in that, The guiding and protecting mechanism includes a first connecting cylinder and a second connecting cylinder both in a cylindrical shape and arranged inside the telescopic cylinder. A first end cover is arranged at the top of the first connecting cylinder, and a second end cover is arranged at the bottom of the second connecting cylinder. The lower end of the first connecting cylinder extends into the interior of the second connecting cylinder and is in sliding contact with the second connecting cylinder. Vertical holes and horizontal holes are opened in both the first connecting cylinder and the second connecting cylinder, and the vertical holes and the horizontal holes form a wire passing channel; a clamping groove is opened on the outer wall of the first connecting cylinder, and a contact piece is arranged in the clamping groove; a contact head for contacting the contact piece is installed in the horizontal hole of the second connecting cylinder. One section of the resistance heating layer wire is introduced into the wire passing channel inside the first connecting cylinder and is electrically connected to the contact piece, and the other section of the resistance heating layer wire is introduced into the wire passing channel inside the second connecting cylinder and is connected to the contact head; when the SMA energy dissipation bearing is not deformed by impact, the contact head and the contact piece are not in contact; when the SMA energy dissipation bearing is deformed by impact, the contact head and the contact piece are in contact with each other.

4. The modular self-healing energy-absorbing rockfall retaining wall based on SMA bearings according to claim 3, characterized in that, A return spring is arranged between the lower end of the first connecting cylinder and the second end cover, and a return spring is arranged between the upper end of the second connecting cylinder and the first end cover. The initial lengths of the return springs at the ends of the first connecting cylinder and the second connecting cylinder are both greater than the deformation amount of the telescopic cylinder.

5. The modular self-healing energy-absorbing rockfall retaining wall based on SMA bearings according to any one of claims 2-4, characterized in that The guiding and protecting mechanism further includes a third connecting cylinder and a fourth connecting cylinder both in a cylindrical shape and arranged on the periphery of the telescopic cylinder. The upper end of the third connecting cylinder is connected to the mounting plate at the upper end of the telescopic cylinder, and the fourth connecting cylinder is connected to the mounting plate at the lower end of the telescopic cylinder. The upper end of the fourth connecting cylinder extends into the interior of the third connecting cylinder and is in sliding contact with the third connecting cylinder; a return spring is arranged between the lower end of the third connecting cylinder and the lower mounting plate, and a return spring is arranged between the upper end of the fourth connecting cylinder and the upper mounting plate; the initial lengths of the return springs at the ends of the third connecting cylinder and the fourth connecting cylinder are both greater than the deformation amount of the telescopic cylinder.

6. The modular self-healing energy-absorbing rockfall retaining wall based on SMA bearings according to claim 5, characterized in that, Grooves for placing return springs are opened on the sides of the first connecting cylinder and the third connecting cylinder facing the telescopic cylinder.

7. The modular self-healing energy-absorbing boulder retaining wall based on SMA bearings according to claim 1, characterized in that, The rigid panel is formed by splicing a number of panel units. Protrusions and chutes are respectively arranged on four side faces of each panel unit. The protrusions are arranged on two opposite side faces of the panel unit, and the chutes are arranged on two opposite side faces of the panel unit. The thickness of the protrusion is less than the width of the chute so that the protrusion can slide in the chute along the direction perpendicular to the panel unit, and the difference between the width of the chute and the thickness of the protrusion is less than the deformation amount of the telescopic cylinder; the protrusions of the panel unit are adapted to the chutes on the adjacent panel unit; at least one SMA energy dissipation support is arranged behind each panel unit.

8. The modular self-healing energy-absorbing boulder retaining wall based on the SMA bearing according to claim 7, characterized in that, At least three guide rods are fixedly installed on the mounting plate of the telescopic cylinder. Through holes are arranged at the positions corresponding to the mounting plate on the panel unit, and the guide rods pass through the through holes of the panel unit.

9. The modular self-healing energy-absorbing rockfall retaining wall based on SMA bearings according to claim 1, characterized in that, When the SMA energy dissipation support is used in a high-impact area, the telescopic cylinder is made of the following raw materials by weight: 64 - 66 parts of Cu, 29 - 31 parts of Zn, and 4 - 6 parts of Al; the activation temperature of the telescopic cylinder is 70 - 80 °C; the tensile strength of the telescopic cylinder is greater than or equal to 400 MPa, the yield strength of the telescopic cylinder is greater than or equal to 300 MPa, the elastic modulus of the telescopic cylinder is 70 - 100 MPa; the impact toughness of the telescopic cylinder is 10 - 20 J / cm²; the strain of the telescopic cylinder is 5 - 8%.

10. The modular self-healing energy-absorbing boulder retaining wall based on the SMA bearing according to claim 1, characterized in that, When the SMA energy dissipation support is used in a low-impact area, the telescopic cylinder is made of the following raw materials by weight: 74 - 76 parts of Cu, 19 - 21 parts of Zn, and 4 - 6 parts of Al; the activation temperature of the telescopic cylinder is 50 - 70 °C; the tensile strength of the telescopic cylinder is greater than or equal to 300 MPa, the yield strength of the telescopic cylinder is greater than or equal to 250 MPa, the elastic modulus of the telescopic cylinder is 70 - 100 MPa; the impact toughness of the telescopic cylinder is 10 - 20 J / cm²; the strain of the telescopic cylinder is not less than 3 - 5%.

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