Constant-resistance large-deformation force-transfer cushion applicable to shear keys of immersed tunnel joints and design method

Abstract

The present invention discloses a constant-resistance large-deformation force transfer cushion for shear keys of immersed tunnel joints and a design method. The constant-resistance large-deformation force transfer cushion is arranged between adjacent vertical or horizontal shear keys, and comprises a cushion box, a sleeve, a slip resistance member and a force transfer rod. The sleeve is fixed in the cushion box; the slip resistance member is arranged in the sleeve. A non-through hole is arranged in the slip resistance member along the vertical direction, and there is a distance between the bottom surface of the slip resistance member and the bottom surface of the cushion box; the upper end of the force transfer rod extends out of the sleeve, and its lower end is embedded in the hole and is in sliding fit with the hole; the slip resistance member is configured such that when the force transfer rod drives the slip resistance member to move downward, the slip resistance member is used to squeeze the sleeve to cause radial expansion thereof, so that a constant sliding friction resistance is generated between the slip resistance member and the sleeve on the extrusion surface. The present invention has multiple functions such as a large stable deformation amount, a high constant resistance, energy absorption, and the ability to control the internal force value received by the shear key, and solves the problems in the background art.

Description

Technical Field

[0001] The present invention relates to the technical field of immersed tunnel design and construction, and particularly relates to a constant-resistance large-deformation force transfer cushion for a shear key of an immersed tunnel joint and a design method therefor. Background Art

[0002] With the deep promotion of the strategies of building China into a maritime power and a transportation power, the transportation engineering industry has shown a booming development trend. There are many cross-river and cross-sea channels that have been built, are under construction, and are planned to be built in China, and a large number of major projects such as cross-river and cross-sea tunnels have emerged continuously. Due to many advantages such as flexible burial depth, strong adaptability to geological conditions, short connection lines on both sides of the river, and small impact on the shoreline environment, the immersed tunnel construction method has become one of the main construction methods for these cross-river and cross-sea tunnel constructions, and is gradually developing in the directions of long distance, large pipe section, strong runoff, thick soft foundation, deep foundation trench, and large burial depth. In an ultra-long, deep-buried, large siltation, and strong foundation non-uniformity environment, the shear safety degree of the immersed tunnel pipe joint is relatively low, and there will be a risk of shear failure of the joint structure due to excessive differential settlement. The shear key is an important connecting structure arranged at the joint of the immersed tunnel pipe section. The internal force and deformation generated between adjacent pipe sections are mainly transmitted through the joint shear key. By the staggered deformation between adjacent shear keys, the rigidity of the immersed tube structure and the flexibility of the joint are combined to ensure that the immersed tube joint can have a certain structural safety while being able to generate deformation. When complex differential settlement occurs underwater, excessive internal force and deformation will cause structural damage to the joint shear key, resulting in water seepage in the immersed tube wall or joint. Therefore, how to avoid the shear failure of the shear key of the immersed tunnel pipe joint under differential settlement has great significance for ensuring the structural and waterproof safety of the immersed tunnel joint.

[0003] At present, a force transfer cushion layer is often placed between the shear keys of the segment joints of immersed tunnels to transfer the contact pressure and joint deformation between the shear keys. Through the passive compression of the force transfer cushion layer, the differential settlement between the segments is released. The existing force transfer cushion layers for the shear keys of immersed tunnel joints are often EPS plastic board cushion layers or rubber cushion layers, which have large deformations, but low stiffness and bearing capacity, and are only applicable to shallow-buried immersed tunnels or cases with small differential settlements between segment joints; in the case of large burial depths or large differential settlements, these EPS plastic board cushion layers or rubber cushion layers will be excessively compressed, unable to control the magnitude of the contact pressure between the shear keys, which may cause the internal force borne by the shear keys to exceed the bearing capacity of the shear keys, resulting in shear failure of the shear keys. Chinese patent document CN202122757642.4 records a shear key elastic cushion device for immersed tunnels, which meets the functional requirements of large deformation compression of the existing force transfer cushion layer for shear keys of immersed tunnels through the vertical elastic compression deformation of the elastic elements in the annular space surrounded by the upper seat plate and the lower seat plate. However, this structure is relatively complex, and its action mechanism under large deformation compression is similar to spring compression. As the compression deformation increases, the internal force of the elastic elements will continue to increase. In the case of large burial depths or large differential settlements, the internal force borne by the shear keys can exceed their bearing capacity, causing shear failure of the shear keys.

[0004] Therefore, there is an urgent need to develop a force transfer cushion layer for the shear keys of immersed tunnels that not only has large deformations but also can control the magnitude of the internal force borne by the shear keys to avoid shear failure of the shear keys under large burial depths or large differential settlements. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a constant resistance large deformation force transfer cushion layer and design method applicable to the shear keys of immersed tunnel joints. The structural design of the present invention is novel, with multiple functions such as a large stable deformation amount, high constant resistance, energy absorption, and the ability to control the magnitude of the internal force borne by the shear keys, solving the problems in the background technology.

[0006] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0007] On the one hand, the present invention provides a constant-resistance large-deformation force-transfer cushion applicable to shear keys of immersed tunnel joints. The constant-resistance large-deformation force-transfer cushion is arranged between adjacent vertical or horizontal shear keys. The constant-resistance large-deformation force-transfer cushion includes a cushion box, a sleeve, a slip resistance member, and a force-transfer rod. The sleeve is fixed inside the cushion box; the slip resistance member is arranged inside the sleeve. A non-penetrating hole is arranged vertically inside the slip resistance member. There is a gap between the bottom surface of the slip resistance member and the bottom surface of the cushion box; the upper end of the force-transfer rod extends out of the sleeve, and its lower end is embedded in the hole and is in sliding fit with it; the slip resistance member is configured such that when the force-transfer rod drives the slip resistance member to move downward, the slip resistance member is used to squeeze the sleeve to cause it to expand radially, so that a constant sliding friction resistance is generated between the slip resistance member and the sleeve on the extrusion surface.

[0008] Preferably, the slip resistance member includes a cone body and a slip rod fixed to the bottom of the cone body. The slip rod is arranged inside the sleeve and is in sliding fit with it. The cone body is arranged inside the sleeve and extrudes the sleeve outward, so that the contact surface between the cone body and the sleeve is extruded into a conical surface, and the angle between the conical surface and the horizontal plane is an acute angle.

[0009] Preferably, the material strength of the sleeve is lower than the material strength of the slip resistance member to prevent the cone body from being damaged by friction due to its lower strength when the cone body slips inside the sleeve, resulting in a resistance reduction characteristic;

[0010] Preferably, a grouting hole is arranged on the cushion box, and the gap between the cushion box and the sleeve is filled with cement mortar to prevent the sleeve from rusting and at the same time enhance the sliding friction resistance between the slip resistance member and the sleeve.

[0011] Preferably, the top of the sleeve extends out of the cushion box to form an extended end, and the surface of the extended end is provided with threads, and a first fastening nut is arranged on the threads.

[0012] Preferably, fixing feet are arranged at the bottom of the cushion box, and a screw rod and a second fastening nut are arranged on the fixing feet.

[0013] Preferably, a cap is arranged at the upper end of the force-transfer rod.

[0014] Assume that the maximum axial friction resistance that can be provided between the sleeve and the cone body is the critical resistance P0, and the axial pressure applied by the force-transfer rod to the slip rod is P. Then the following criterion can be obtained:

[0015] (1) Elastic deformation stage: When the axial pressure P < critical resistance P0, the differential settlement at the pipe joint is small, the load transfer bars have no rigid movement, and there is no relative sliding between the cone and the sleeve. At this time, through the elastic deformation of the load transfer bars and the sliding bars, the differential settlement and relative rotation at the joint are absorbed.

[0016] (2) Sliding deformation stage: When the axial pressure P ≥ critical resistance P0, the load transfer bars push the cone to move downward rigidly, and relative frictional sliding occurs between the cone and the sleeve, absorbing the differential settlement deformation and relative rotation at the joint. During the sliding process, the cone will maintain a constant frictional resistance P0.

[0017] (3) Rebalanced static stage: After the cone performs frictional sliding work in the sleeve, the differential settlement at the immersed tunnel joint is fully released, and the axial pressure P will be less than the critical resistance P0 again. The cone stops frictional sliding, and the shear key of the joint is in a relatively stable state again.

[0018] Preferably, when the axial resistance provided between the sleeve and the slip resistance member reaches the constant sliding frictional resistance, the shear key needs to be in a safe state, and the relevant parameters of the constant resistance and large deformation load transfer cushion layer of the present invention need to be optimized through indoor shear tests.

[0019] On the other hand, the present invention provides a design method for a constant resistance and large deformation load transfer cushion layer suitable for the shear key of an immersed tunnel joint. The design method includes:

[0020] Step 1) Obtain the maximum allowable differential settlement design value s at the joint of the actual immersed tunnel.

[0021] Step 2) Manufacture the upper shear key and the lower shear key with dimensions and relevant material parameters consistent with the shear key of the actual immersed tunnel. Then install multiple constant resistance and large deformation load transfer cushion layers between the upper shear key and the lower shear key. Keep the upper shear key stationary and slowly move the lower shear key upward by a distance s. During the test, the vertical pressure P and its vertical displacement u received by each cap need to be monitored and recorded.

[0022] Step 3) Determine the maximum vertical external force F received by the upper shear key when the lower shear key moves upward by a displacement s m Whether it is less than the bearing capacity limit F of the upper shear key s , and whether the maximum vertical elastic compression deformation amount u0 before the sliding bar undergoes frictional sliding relative to the sleeve is less than the upward movement displacement s of the lower shear key; if F m ≤F s , and u0 ≤ s, then the various index parameters of the designed constant resistance and large deformation load transfer cushion layer are reasonable, and under the condition of differential settlement s, the shear key will be in a safe state; if F m ≥F sIf \(u_0\leq s\), some of the designed index parameters of the constant-resistance large-deformation force-transfer cushion are unreasonable. Under the differential settlement \(s\), the shear keys may undergo shear failure, and the relevant index parameters of the constant-resistance large-deformation force-transfer cushion need to be redesigned; if \(F\) m \(\leq F\) s and \(u_0\geq s\), the designed constant-resistance large-deformation force-transfer cushion is too conservative and needs to be redesigned.

[0023] Preferably, the method for obtaining the maximum allowable differential settlement design value \(s\) at the joint of the actual relying immersed tunnel in step S1 is as follows:

[0024] Step 1.1) First, conduct a drawing analysis for the relying immersed tunnel engineering project, select three adjacent tunnel segment units with the maximum buried depth or the possible maximum differential settlement of the immersed tunnel as the objects, and establish a three-dimensional finite element refined numerical simulation model including the underlying stratum - immersed tunnel structure - overlying soil layer;

[0025] Step 1.2) If the immersed tunnel adopts an integral segment structure, only the segment joints are simulated in the three-dimensional finite element numerical model. The Gina waterstop at the segment joints is simulated by nonlinear spring elements, and the horizontal and vertical shear keys at the segment joints are simulated by three-dimensional solid elements;

[0026] Step 1.3) If the immersed tunnel adopts a segmental segment structure, in addition to considering the segment joints, the joint segments also need to be simulated in the three-dimensional finite element numerical model; the Gina waterstop at the segment joints is simulated by nonlinear spring elements, and the horizontal and vertical shear keys at the segment joints are simulated by three-dimensional solid elements; the main stress-bearing members at the internal segment joints of the segment units are generally shear keys, so the horizontal and vertical shear keys at the joint segments are simulated by three-dimensional solid elements;

[0027] Step 1.4) Based on the established three-dimensional finite element refined numerical simulation model of the underlying stratum - immersed tunnel structure - overlying soil layer, carry out the simulation of the landfill construction process of the relying immersed tunnel, and analyze the maximum differential settlement value \(s1\) at the segment joints during the construction stage;

[0028] Step 1.5) Using the equivalent load method to consider the traffic load and seismic load, considering the maximum back-silt buried depth at the top of the tunnel during the operation stage, based on the established three-dimensional finite element refined numerical simulation model of the underlying stratum - immersed tunnel structure - overlying soil layer, carry out the numerical simulation analysis of the stress and deformation of the relying immersed tunnel during the operation stage, and analyze the maximum differential settlement value \(s2\) at the segment joints during the operation stage;

[0029] Step 1.6) Based on the obtained maximum differential settlements \(s1\) and \(s2\), select the maximum value of the two as the maximum allowable differential settlement design value \(s\) at the joint.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] In the present invention, through the sliding of the conical body inside the sleeve, the casing expands radially and deforms. The friction force between the conical body and the sleeve is used to generate a constant resistance and a large deformation amount. The deformation energy of the joint is absorbed by the friction work between the conical body and the sleeve. The upper limit value of the contact pressure between the shear keys of the joint can be controlled to avoid the shear failure of the shear keys under large buried depths or large differential settlements, and the vibration and impact energy induced by accidental loads such as strong earthquakes, shipwrecks, vehicle impacts, and blasting can be absorbed. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic cross-sectional structure diagram of the constant-resistance and large-deformation force-transfer cushion layer of the present invention.

[0033] Figure 2 It is a schematic structure diagram of the constant-resistance and large-deformation force-transfer cushion layer of the present invention installed between adjacent vertical shear keys.

[0034] Figure 3 It is a schematic structure diagram of the constant-resistance and large-deformation force-transfer cushion layer of the present invention installed between adjacent horizontal shear keys.

[0035] Figure 4 It is a structural diagram of a direct shear test for determining the parameters of the designed constant-resistance and large-deformation force-transfer cushion layer.

[0036] Figure 5 It is a functional relationship between the vertical external force F received by the shear key and the vertical displacement u of the cushion cap.

[0037] In the figure: 1 - cushion box; 2 - sleeve; 3 - sliding resistance member; 31 - conical body; 32 - sliding rod; 4 - conical surface; 5 - force-transfer rod; 6 - cap; 7 - extended end; 8 - first fastening nut; 9 - upper shear key; 10 - lower shear key; 11 - grouting hole; 12 - cement mortar; 13 - screw rod; 14 - fixed foot; 15 - second fastening nut; 16 - left shear key; 17 - right shear key; 18 - constant-resistance and large-deformation force-transfer cushion layer; 19 - jack; 20 - horizontal fixed beam; 21 - vertical fixed beam; 22 - ground; 23 - left immersed tube concrete structure; 24 - right immersed tube concrete structure. DETAILED DESCRIPTION OF THE INVENTION

[0038] To enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation of the present invention will be described below in conjunction with specific embodiments. However, it should be understood that the drawings are only for illustrative purposes and cannot be construed as a limitation of this patent; to better illustrate this embodiment, some components in the drawings will be omitted, enlarged or reduced, which do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The positional relationships described in the drawings are only for illustrative purposes and cannot be construed as a limitation of this patent.

[0039] Embodiment 1

[0040] As Figure 1 shown, the present invention provides a constant-resistance large-deformation force-transfer cushion applicable to shear keys of immersed tunnel joints. The constant-resistance large-deformation force-transfer cushion is arranged between adjacent vertical shear keys. The constant-resistance large-deformation force-transfer cushion includes a cushion box 1, a sleeve 2, a slip resistance member 3 and a force-transfer rod 5. The slip resistance member includes a cone 31 and a slip rod 32. Among them, the materials of the cushion box 1, the sleeve 2, the cone 31, the slip rod 32 and the force-transfer rod 5 are all steel materials.

[0041] As Figure 1 and 2 shown, fixed feet 14 are arranged on the left and right sides of the bottom surface of the cushion box 1 in the device of the present invention. A cylindrical screw hole is arranged at the center of the fixed feet 14. The screw 13 is placed in the screw hole, and a second fastening nut 15 is installed on the upper part of the screw 13 to press the fixed feet 14 against the lower shear key 10, so as to realize the fixed installation of the cushion box 1 on the lower shear key 10.

[0042] As Figure 1 shown, a circular opening is arranged in the middle of the top surface of the cushion box 1. The sleeve 2 is placed inside the cushion box 1 through the circular opening, and the center line of the sleeve 2 coincides with the center line of the cushion box 1; a thread is arranged on the surface of the top extending end 7 of the sleeve 2, and the sleeve 2 is fixed inside the cushion box 1 through the first fastening nut 8.

[0043] As Figure 1 shown, a cone 31 and a slip rod 32 are placed inside the sleeve 2; the cone 31 is fixed on the top surface of the slip rod 32, and the cone 31 and the slip rod 32 are rigidly connected; the cone 31 is arranged inside the sleeve 2 and extrudes the sleeve 2 outward, so that the contact surface between the cone 31 and the sleeve 2 is extruded into a conical surface 4, and the angle between the conical surface 4 and the horizontal plane is an acute angle; there is a certain distance between the lower end surface of the slip rod 32 and the bottom surface of the cushion box 1; the cone 31, the slip rod 32 and the first fastening nut 8 are provided with inner holes of the same diameter; the force-transfer rod 5 passes through the first fastening nut 8, the cone 31 from top to bottom in sequence, and enters the inside of the slip rod 32.

[0044] As Figure 1 shown, the load transfer bar 5 is in non-bonded contact with the first fastening nut 8, the conical body 31, and the sliding bar 32, and it can be freely pulled out upward; a cap 6 is provided at the top of the load transfer bar 5, and the cap 6 is connected to the load transfer bar 5 by a thread.

[0045] As Figure 1 shown, grouting holes 11 are provided on the left and right side walls of the cushion box 1, and cement mortar 12 can be injected into the gap between the inner wall of the cushion box 1 and the outer wall of the sleeve 2 through the grouting holes 11 to protect the sleeve 12 and prevent it from rusting.

[0046] As Figure 1 shown, the material strength of the sleeve 2 needs to be lower than that of the conical body 31 and the sliding bar 32 to prevent the conical body 31 from being damaged by friction due to its low strength when the conical body 31 slides in the sleeve 2, resulting in a resistance reduction characteristic; when the axial resistance provided between the sleeve 2 and the conical body 31 reaches the critical resistance P0, the shear key needs to be in a safe state, and the value of P0 needs to be determined through an indoor shear test.

[0047] As Figure 4 and 5 shown, to prevent the shear key structure of the immersed tunnel joint from being damaged by shear, the present invention can be designed and installed according to the following steps:

[0048] Step 1) First, analyze the drawings for the immersed tunnel engineering project to be relied on, select three adjacent tunnel segment units at the maximum buried depth or the location where the maximum differential settlement may occur in the immersed tunnel as the object, and establish a three-dimensional finite element refined numerical simulation model including the underlying stratum - the immersed tunnel structure - the overlying soil layer;

[0049] Step 2) If the immersed tunnel adopts an integral segment structure, only the segment joints are simulated in the three-dimensional finite element numerical model. The Gina waterstop at the segment joints is simulated by a nonlinear spring element, and the horizontal and vertical shear keys at the segment joints are simulated by three-dimensional solid elements;

[0050] Step 3) If the immersed tunnel adopts a segmental segment structure, in addition to considering the segment joints, the joint between segments needs to be simulated in the three-dimensional finite element numerical model. The Gina waterstop at the segment joints is simulated by a nonlinear spring element, and the horizontal and vertical shear keys at the segment joints are simulated by three-dimensional solid elements. The main load-bearing members at the joint between segments inside the segment unit are generally shear keys, so the horizontal and vertical shear keys at the joint between segments are simulated by three-dimensional solid elements;

[0051] Step 4) Based on the established 3D finite element refined numerical simulation model of the underlying stratum - immersed tube tunnel structure - overlying soil layer, conduct the landfill construction process simulation of the immersed tube tunnel of the project under study, and analyze the maximum differential settlement value s1 at the joints of the tunnel segments during the construction stage;

[0052] Step 5) Consider the traffic load and seismic load by the equivalent load method, and consider the maximum silting burial depth on the top of the tunnel during the operation stage. Based on the established 3D finite element refined numerical simulation model of the underlying stratum - immersed tube tunnel structure - overlying soil layer, conduct the numerical simulation analysis of the stress and deformation of the immersed tube tunnel of the project under study during the operation stage, and analyze the maximum differential settlement value s2 at the joints of the tunnel segments during the operation stage;

[0053] Step 6) Based on the obtained maximum differential settlements s1 and s2, select the maximum value of the two as the design value s of the maximum allowable differential settlement at the joints.

[0054] Step 7) Based on the design drawings of the immersed tube tunnel under study, fabricate two shear key test specimens, the dimensions and related material parameters of which shall be consistent with those of the shear keys of the actual immersed tube tunnel under study, and conduct the shear test as Figure 4 shown.

[0055] Step 8) When conducting the shear test as Figure 4 shown, install the upper shear key 9 on the corresponding left immersed tube concrete structure 23, install the lower shear key 10 on the corresponding right immersed tube concrete structure 24, place the bottom of the immersed tube concrete structure 23 on the ground, use the horizontal fixed beam 20 to restrict the vertical movement of the left immersed tube concrete structure 23, rigidly connect the horizontal fixed beam 20 with the vertical fixed beam 23, and rigidly connect the vertical fixed beam 23 with the ground 22; a row of jacks 19 are installed at the bottom of the immersed tube concrete structure 24, and the right immersed tube concrete structure 24 and the lower shear key 10 are pushed to move upward by a displacement s through the jacks 19.

[0056] Step 9) When conducting the shear test as Figure 4 shown, install n invented constant resistance large deformation force transfer cushions between the upper shear key 9 and the lower shear key 10, slowly push the immersed tube concrete structure 24 to move upward by a distance s through the bottom jacks 19. During the test process, it is necessary to monitor the vertical pressure P and its vertical displacement u received by the cap 6 of the invented constant resistance large deformation force transfer cushion, and the vertical external force F received by the upper shear key 9 is calculated as follows:

[0057] F = nP i A (1)

[0058] In formula (1), n is the number of installed constant resistance large deformation force transfer cushions, and P is the vertical pressure received by the cap 6 of a single constant resistance large deformation force transfer cushion; A i is the top area of the cap of a single constant resistance large deformation force transfer cushion.

[0059] Step 10) Determine the maximum vertical external force F on the upper shear key 9 when the lower shear key moves upward by a displacement s m Whether it is less than the bearing capacity limit F of the upper shear key 9 s , and whether the maximum vertical elastic compression deformation u0 before the sliding rod undergoes frictional sliding relative to the sleeve is less than the upward movement displacement s of the lower shear key; as Figure 5 shown, if F m ≤F s , and u0 ≤ s, then the index parameters of the designed constant-resistance large-deformation force-transfer cushion are reasonable, and under the differential settlement s condition, the shear keys will be in a safe state; if F m ≥F s , and u0 ≤ s, then some of the index parameters of the designed constant-resistance large-deformation force-transfer cushion are unreasonable, and under the differential settlement s condition, the shear keys may undergo shear failure, and the relevant index parameters of the constant-resistance large-deformation force-transfer cushion need to be redesigned (mainly including the number n of cushions placed, the inclined surface angle and the two end diameters of the cone 31, the length of the cone 31, the contact surface friction coefficient between the steel sleeve 2 and the cone 31, the inner diameter of the steel sleeve, etc.); if F m ≤F s , and u0 ≥ s, then the designed constant-resistance large-deformation force-transfer cushion is too conservative and needs to be redesigned;

[0060] Step 11) After optimizing the design of the relevant index parameters of the constant-resistance large-deformation force-transfer cushion invented through direct shear tests, the functional relationship between the vertical external force F on the upper shear key 9 and the vertical displacement u of the cushion cap 6 needs to present Figure 5 the characteristics shown, with functions such as a large stable deformation amount, a high constant resistance, energy absorption, and the ability to control the contact pressure value between shear keys;

[0061] Step 12) After the on-site construction of the immersed tunnel to which it belongs starts, install the optimized constant-resistance large-deformation force-transfer cushion 18 between adjacent vertical shear keys and adjacent horizontal shear keys at the immersed tunnel pipe joint to protect the shear keys and concrete structures at the pipe joint and prevent them from undergoing shear failure under large differential settlements.

[0062] Embodiment 2

[0063] As Figure 3 shown, the difference between this embodiment and Embodiment 1 is that: the constant-resistance large-deformation force-transfer cushion is placed between adjacent horizontal shear keys, and the fixed feet 14 at the bottom of the cushion box 1 are pressed against the left shear key 16 through the screw 13 and the second fastening nut 15 to realize the fixed installation of the cushion box 1 on the left shear key 16.

[0064] Based on the description and drawings of the present invention, those skilled in the art can easily manufacture or use a constant-resistance large-deformation force-transfer cushion layer for a shear key of a immersed tunnel joint according to the present invention and its design method, and can achieve the positive effects recorded in the present invention.

[0065] Unless otherwise specified, in the present invention, if there are terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., the orientation or positional relationship indicated 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. Therefore, the terms used to describe the orientation or positional relationship in the present invention are only for exemplary illustration and should not be construed as a limitation of this patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood in combination with the drawings and according to specific circumstances.

[0066] Unless otherwise clearly defined and limited, in the present invention, if there are terms such as "set", "connected" and "connected", they 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, and it can be the communication inside two elements. 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.

[0067] The above is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Any simple modification and equivalent change made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

[0068] The above is only the preferred implementation scheme of the present invention, but the present invention is not limited to the above specific implementation schemes. Without departing from the principle of the present invention, those of ordinary skill in the art can make several modifications, supplements, or use similar methods to replace them, and these should also be regarded as the protection scope of the present invention.

Claims

1. A constant-resistance large-deformation force-transfer cushion applicable to shear keys of immersed tunnel joints. The constant-resistance large-deformation force-transfer cushion is arranged between adjacent vertical or horizontal shear keys, and is characterized in that: The constant-resistance large-deformation force transfer cushion layer includes a cushion box (1), a sleeve (2), a slip resistance member (3), and a force transfer rod (5). The sleeve (2) is fixed inside the cushion box (1); the slip resistance member (3) is arranged inside the sleeve (2). A non-penetrating hole is arranged vertically inside the slip resistance member (3). There is a gap between the bottom surface of the slip resistance member (3) and the bottom surface of the cushion box (1); the upper end of the force transfer rod (5) extends out of the sleeve (2), and its lower end is embedded in the hole and is in sliding fit with it; the slip resistance member (3) is arranged such that when the force transfer rod (5) drives the slip resistance member (3) to move downward, the slip resistance member (3) is used to squeeze the sleeve (2) to cause it to expand radially, so that a constant sliding friction resistance is generated between the slip resistance member (3) and the sleeve (2) on the extrusion surface. The slip resistance member (3) includes a conical body (31) and a slip rod (32) fixed to the bottom of the conical body (31). The slip rod (32) is arranged inside the sleeve (2) and is in sliding fit with it. The conical body (31) is arranged inside the sleeve (2) and extrudes the sleeve (2) outward, so that the contact surface between the conical body (31) and the sleeve (2) is extruded into a conical surface (4). The angle between the conical surface (4) and the horizontal plane is an acute angle; the material strength of the sleeve (2) is lower than that of the slip resistance member (3); a grouting hole (11) is arranged on the cushion box (1), and cement mortar (12) is filled in the gap between the cushion box (1) and the sleeve (2). A cap (6) is arranged at the upper end of the force transfer rod (5). When the axial resistance provided between the sleeve (2) and the slip resistance member (3) reaches the constant sliding friction resistance, the shear key needs to be in a safe state.

2. The constant-resistance large-deformation force transfer cushion applicable to the shear key of the immersed tunnel joint according to claim 1, wherein: The top of the sleeve (2) extends out of the cushion box (1) to form an extended end (7). Threads are arranged on the surface of the extended end (7), and a first fastening nut (8) is arranged on the threads.

3. The constant-resistance large-deformation force transfer cushion applicable to the shear key of the immersed tunnel joint according to claim 1, characterized in that: Fixed feet (14) are arranged at the bottom of the cushion box (1), and a screw rod (13) and a second fastening nut (15) are arranged on the fixed feet (14).

4. A design method for a constant-resistance large-deformation force transfer cushion applicable to shear keys of immersed tunnel joints as described in any one of claims 1-3, characterized in that, The design method includes: Step 1) Obtain the design value of the maximum allowable differential settlement at the joint of the actual immersed tube tunnel s ; Step 2) Fabricate the upper shear key and the lower shear key with dimensions and relevant material parameters consistent with those of the shear keys of the actual immersed tunnel underpinning. Then, install multiple constant-resistance large-deformation force transfer cushions between the upper shear key and the lower shear key. Keep the upper shear key stationary and slowly move the lower shear key upward by a distance s . During the test, it is necessary to monitor and record the vertical pressure on each cap P and its vertical displacement u ; Step 3) Determine whether the vertical external force maximum value on the upper shear key s when the lower shear key moves upward F m is less than the bearing capacity limit of the upper shear key F s and whether the maximum vertical elastic compression deformation amount of the sliding rod relative to the sleeve before frictional sliding occurs u 0 is less than the upward movement displacement of the lower shear key s ; if F m ≤ F s and u 0 ≤ s , then the index parameters of the designed constant-resistance large-deformation force transfer cushion are reasonable, and under the differential settlement s condition, the shear key will be in a safe state; if F m ≥ F s and u 0≤ s , then some index parameters of the designed constant-resistance large-deformation force transfer cushion are unreasonable, and under the differential settlement s condition, the shear key may undergo shear failure, and the relevant index parameters of the constant-resistance large-deformation force transfer cushion need to be redesigned; if F m ≤ F s and u 0≥ s , then the designed constant-resistance large-deformation force transfer cushion is too conservative and needs to be redesigned.

5. The design method according to claim 4, characterized in that: The method for obtaining the maximum allowable differential settlement design value at the actual joint of the immersed tunnel in step S1 is as follows: s : Step 1.1) First, conduct a drawing analysis for the immersed tube tunnel engineering project on which it depends. Select three adjacent tunnel segment units at the maximum buried depth or the location where the maximum differential settlement may occur in the immersed tube tunnel as the object, and establish a three-dimensional finite element refined numerical simulation model including the underlying stratum - immersed tube tunnel structure - overlying soil layer. Step 1.2) If the immersed tube tunnel adopts an integral segment structure, only the segment joint is simulated in the three-dimensional finite element numerical model. The Gina waterstop at the segment joint is simulated by a nonlinear spring element, and the horizontal and vertical shear keys at the segment joint are simulated by three-dimensional solid elements. Step 1.3) If the immersed tunnel adopts a segmental pipe structure, in addition to considering the joints of the pipe elements in the three-dimensional finite element numerical model, it is also necessary to simulate the segment joints; the Gina waterstop at the joints of the pipe elements is simulated by non-linear spring elements, and the horizontal and vertical shear keys at the joints of the pipe elements are simulated by three-dimensional solid elements; the main stress-bearing members at the segment joints inside the pipe elements are shear keys, so the horizontal and vertical shear keys at the segment joints are simulated by three-dimensional solid elements. Step 1.4) Based on the established three-dimensional finite element fine numerical simulation model of the underlying stratum - immersed tunnel structure - overlying soil layer, carry out the simulation of the landfill construction process of the immersed tunnel of the project under study, and analyze the maximum differential settlement value s1 at the joints of the tunnel pipes during the construction stage. Step 1.5) Using the equivalent load method to consider the traffic load and seismic load, considering the maximum silting burial depth at the top of the tunnel during the operation stage, based on the established three-dimensional finite element fine numerical simulation model of the underlying stratum - immersed tunnel structure - overlying soil layer, carry out the numerical simulation analysis of the stress and deformation of the immersed tunnel of the project under study during the operation stage, and analyze the maximum differential settlement value s2 at the joints of the tunnel pipes during the operation stage. Step 1.6) Based on the obtained maximum differential settlements s1 and s2, select the maximum value of the two as the design value s of the maximum allowable differential settlement at the joints.

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