A servo-controlled variable stiffness tunnel lining static-dynamic loading test system

Abstract

The present invention discloses a servo-controlled variable stiffness tunnel lining static-dynamic loading test system, which belongs to the technical field of tunnel engineering test equipment, and includes a servo-controlled variable stiffness test system, which includes a variable stiffness test loading system, a monitoring system, a vibration platform, a hydraulic pump station and a control system. The servo-controlled variable stiffness tunnel lining static-dynamic loading test system can simulate the test of various stiffness ranges of different circumferential and axial positions of the tunnel under compression according to the test requirements by adjusting the variable stiffness loading system, and can also simulate the dynamic response characteristics of the tunnel under compression through the vibration system, and can more accurately meet the indoor test requirements of the tunnel under compression and earthquake conditions. Secondly, during loading, the static-dynamic load test of the tunnel lining containing a cavity behind can also be simulated by adjusting whether the pressure head assembly is pressurized, so as to meet the mechanical property test of the diseased tunnel.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering test equipment, in particular to a servo-controlled variable-rigidity tunnel lining static-dynamic loading test system. Background Art

[0002] Traditional tunnel and underground engineering model tests are usually carried out using similar material model test systems. First, the similarity ratio of the model is determined according to the requirements of the prototype and indoor laboratory conditions. Quartz sand, gypsum, glycerin and water are used to adjust the proportion of materials to cast the surrounding rock and lining models respectively. Not only is the workload large, but the material consumption is also large, and the test is relatively time-consuming and labor-intensive. Another way is to pressurize the tunnel lining model through a mechanical device, and arrange multiple hydraulic loading devices along the lining ring to achieve the application and control of the lining load, which can effectively reduce the preparation of manpower and materials, and is relatively time-saving and labor-saving. However, since the loading stiffness in the mechanical pressurization system is a constant value, the characterization of surrounding rocks of different levels can only be achieved by replacing springs with different stiffnesses, which increases the difficulty of the test process. At present, mechanical pressurization devices are mostly used for the study of strength and deformation characteristics of two-dimensional tunnel models under static loads, and lack the design and development of corresponding three-dimensional devices under dynamic loads (earthquake effects). my country is located between the world's two major seismic belts - the Pacific Rim and the Eurasian Seismic Belt. Regional earthquakes are very active and frequent, and nearly half of the country's land area is located in high-intensity areas above 7 degrees. The comprehensive and rapid development of my country's transportation engineering makes it inevitable that tunnel projects will be built in high-intensity areas. Therefore, it is very necessary to develop a test system that can simultaneously realize the evaluation of the evolution law of tunnel mechanical properties under seismic loads. Summary of the invention

[0003] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0004] In view of the above-mentioned and / or existing problems in the existing tunnel similar material model test system, the present invention is proposed.

[0005] Therefore, the technical problem to be solved by the present invention is that the traditional model test needs to determine the similarity ratio of the model according to the requirements of the on-site prototype and the indoor laboratory conditions, and use quartz sand, gypsum, glycerin and water to adjust the ratio and cast the surrounding rock and lining models respectively. Not only is the workload large, but the material consumption is also large, and the test is relatively time-consuming and laborious. Secondly, the loading stiffness in the mechanical pressurization system is a constant value. Only by replacing springs with different stiffnesses can the characterization of surrounding rocks of different levels be achieved, which increases the difficulty of the test process. At present, mechanical pressurization devices are mostly used for the study of strength and deformation characteristics of two-dimensional tunnel models under static loads, and there is a lack of design and development of corresponding three-dimensional devices under dynamic loads (seismic effects).

[0006] To achieve the above-mentioned object, the present invention provides the following technical solutions: a servo-controlled variable stiffness tunnel lining static-dynamic loading test system, including a servo-controlled variable stiffness test system, the servo-controlled variable stiffness test system including a variable stiffness test loading system, a monitoring system, a vibration platform, a hydraulic pump station and a control system;

[0007] The variable stiffness test loading system comprises a first reaction frame, a second reaction frame, a first support, a second support, a pressure head assembly and a lining fixed base;

[0008] A tunnel lining specimen is arranged inside the first reaction frame and the second reaction frame, one end face of the first support is fixed to the first reaction frame and the second reaction frame by bolts, the other end face of the first support is fixedly connected to the vibration platform by bolts, one end face of the second support is fixed to the first reaction frame and the second reaction frame by bolts, and the other end face of the second support is fixedly connected to the vibration platform by bolts;

[0009] There are four lining fixing bases, and the tunnel lining specimen is arranged on the lining fixing bases, and the lining fixing bases are located between the first support and the second support, and are fixedly connected with the first support and the second support by bolts;

[0010] The pressure head assembly is composed of a servo electric cylinder, a guide rod, a fixed flange, a pressure sensor, a displacement sensor and an arc clamping plate. The servo electric cylinder is fixedly installed on the fixed flange. A guide rail is provided below the servo electric cylinder. The displacement sensor is assembled and installed at the bottom end of the servo electric cylinder. There are two guide rods, which pass through the guide rail, the fixed flange and the side of the displacement sensor. The bottom ends of the two guide rods are equipped with an arc clamping plate, and the pressure sensor is fixedly installed above the arc clamping plate.

[0011] The vibration platform is divided into an upper platform, a middle platform, a lower platform, a servo cylinder and fixed feet. The upper platform is assembled above the middle platform, and the middle platform is assembled above the lower platform. Servo cylinders are arranged on the upper platform and the middle platform, and the lower platform is fixed to the fixed feet.

[0012] As a further solution of the present invention: the displacement sensor and the pressure sensor constitute a monitoring system.

[0013] As a further solution of the present invention: the axial lengths of the first reaction frame and the second reaction frame are 1 m respectively;

[0014] The axial lengths of the first support and the second support are 2 m respectively.

[0015] As a further solution of the present invention: the middle platform and the lower platform of the vibration platform are connected by a slide rail, and the middle platform generates X-axis movement under the action of the servo cylinder;

[0016] The upper platform and the middle platform are also connected by slide rails, and the upper platform generates Y-axis movement under the action of the servo cylinder;

[0017] The vibration frequency of the vibration platform is within 0-20 Hz.

[0018] As a further solution of the present invention: the first reaction frame and the second reaction frame are each provided with nine mounting holes, a scale line is provided on one side of each mounting hole, and the annular spacing of the mounting holes is 22.5°;

[0019] Two pressing head assemblies are installed on each mounting hole of the first reaction frame and the second reaction frame, and the fixing flange and the guide rail cooperate to enable the pressing head assembly to slide linearly in the mounting hole.

[0020] As a further solution of the present invention: the arc-shaped clamping plate is a detachable structure, and a rubber pad is fixedly connected to the inner surface of the arc-shaped clamping plate;

[0021] The arc-shaped clamping plate is made of metal, and the curvature of the arc-shaped clamping plate is consistent with the curvature of the corresponding part of the tunnel lining specimen.

[0022] As a further solution of the present invention: the servo electric cylinder is composed of a loading cylinder and a stiffness adjusting cylinder.

[0023] As a further solution of the present invention: the first reaction frame and the second reaction frame are made of Q235 steel, welded by steel plates and square tubes, heat treated after welding, and sprayed.

[0024] As a further solution of the present invention: the servo electric cylinder of the pressure head assembly and the servo cylinder of the vibration platform are powered by a hydraulic pump station.

[0025] As a further solution of the present invention: the data monitored by the displacement sensor and the pressure sensor are fed back to the control system in real time, and the control system adjusts the pressurization of the stiffness regulating cylinder in real time according to the displacement monitored by the displacement sensor and a preset stiffness value.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The servo-controlled variable stiffness tunnel lining static-dynamic loading test system can simulate the test of various stiffness ranges in different circumferential and axial positions of the tunnel under compression according to the test requirements by adjusting the variable stiffness loading system. It can also simulate the dynamic response characteristics of the tunnel under compression through the vibration system, and can more accurately meet the indoor test requirements of the tunnel under compression and vibration. Secondly, during loading, the static-dynamic load test of the tunnel lining with cavities behind can be simulated by adjusting whether the pressure head assembly is pressurized, so as to meet the mechanical performance test of the diseased tunnel;

[0028] 2. This servo-controlled variable stiffness tunnel lining static-dynamic loading test system realizes load control by adopting an electro-hydraulic servo system, which is low in noise, energy-saving and environmentally friendly, and can be connected with control systems such as PLC to achieve high-precision motion control. Secondly, this device uses a pressure head assembly to concentrate force to replace the surrounding rock load, reducing the surrounding rock pouring process, and realizing the automatic characterization of the surrounding rock stiffness. There is no need to replace springs of different stiffness, which saves time and effort and is simple to operate;

[0029] 3. The servo-controlled variable stiffness tunnel lining static-dynamic loading test system is designed with a vibration platform, which can be used to test the deformation characteristics of tunnel lining under dynamic loads. This device can simultaneously meet the performance test of tunnel lining under static-dynamic loads, and can also realize the performance evaluation of diseased tunnel linings and the study of damage evolution laws. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0031] Figure 1 The present invention is a schematic diagram of the three-dimensional structure of a servo-controlled variable stiffness tunnel lining static-dynamic loading test system according to an embodiment of the present invention.

[0032] Figure 2 A schematic structural diagram of a vibration platform in a servo-controlled variable stiffness tunnel lining static-dynamic loading test system according to an embodiment of the present invention.

[0033] Figure 3 A schematic structural diagram of a first reaction frame in a servo-controlled variable stiffness tunnel lining static-dynamic loading test system according to an embodiment of the present invention.

[0034] Figure 4The present invention is a three-dimensional structural schematic diagram of a pressure head assembly in a servo-controlled variable stiffness tunnel lining static-dynamic loading test system according to an embodiment of the present invention.

[0035] Figure 5 It is a schematic diagram of the division of various parts of the cross section of the tunnel lining specimen of the present invention.

[0036] Figure 6 It is the change of the yield strength of the tunnel lining specimen under different loading stiffnesses of the present invention with the size of the vault cavity of the tunnel lining specimen.

[0037] Figure 7 It is a schematic diagram of the change of the local strain of the arch top of the tunnel lining specimen of the present invention with time.

[0038] Figure 8 It is a schematic diagram of the change of the lining arch strain under different earthquake motion intensities of the present invention.

[0039] In the figure: 1 - first reaction frame; 11 - mounting hole; 2 - second reaction frame; 3 - vibration platform; 31 - upper platform; 32 - middle platform; 33 - lower platform; 34 - fixed foot; 4 - pressure head assembly; 41 - servo cylinder; 42 - guide rod; 43 - fixed flange; 44 - pressure sensor; 46 - displacement sensor; 45 - arc clamp; 5 - first support; 6 - lining fixed base; 7 - tunnel lining specimen; 8 - second support. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0041] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0042] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0043] Furthermore, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments. DETAILED DESCRIPTION

[0045] like Figure 1 -8, the present invention provides a servo-controlled variable stiffness tunnel static-dynamic loading test system, the specific implementation method is as follows

[0046] A servo-controlled variable stiffness tunnel lining static-dynamic loading test system, characterized in that: it includes a servo-controlled variable stiffness test system, the servo-controlled variable stiffness test system includes a variable stiffness test loading system, a monitoring system, a vibration platform 3, a hydraulic pump station and a control system;

[0047] The variable stiffness test loading system includes a first reaction frame 1, a second reaction frame 2, a first support 5, a second support 8, a pressure head assembly 4 and a lining fixed base 6. The axial lengths of the first reaction frame 1 and the second reaction frame 2 are 1m respectively, and the axial lengths of the first support 5 and the second support 8 are 2m respectively. Nine mounting holes 11 are respectively arranged on the first reaction frame 1 and the second reaction frame 2. A scale line is arranged on one side of each mounting hole 11. The annular spacing of the mounting holes 11 is 22.5°. Two pressure head assemblies 4 are installed on each mounting hole 11 of the first reaction frame 1 and the second reaction frame 2. The fixing flange 43 and the guide rail cooperate to make the pressure head assembly 4 slide linearly in the mounting hole 11. The material of the first reaction frame 1 and the second reaction frame 2 is Q235 steel, which is made of steel plates and square tubes welded, heat treated after welding, and sprayed. The servo electric cylinder 41 of the pressure head assembly 4 and the servo cylinder of the vibration platform 3 are powered by a hydraulic pump station;

[0048] The first reaction frame 1 and the second reaction frame 2 are provided with a tunnel lining specimen 7 inside. The tunnel lining specimen 7 can be in various shapes, such as horseshoe or circular. The prototype of the lining model is made of C25 or C30 concrete reinforced casting. Such test models are cast according to the similarity ratio of length and strength. There are two first supports 5 and second supports 8 respectively. One end face of the first support 5 is fixed to the first reaction frame 1 and the second reaction frame 2 by bolts, and the other end face of the first support 5 is fixedly connected to the vibration platform 3 by bolts. One end face of the second support 8 is fixed to the first reaction frame 1 and the second reaction frame 2 by bolts, and the other end face of the second support 8 is fixedly connected to the vibration platform 3 by bolts.

[0049] There are four lining fixing bases 6, and the tunnel lining test piece 7 is arranged on the lining fixing base 6. The lining fixing base 6 is located between the first support 5 and the second support 8, and is fixedly connected with the first support 5 and the second support 8 by bolts;

[0050] The pressure head assembly 4 is composed of a servo electric cylinder 41, a guide rod 42, a fixing flange 43, a pressure sensor 44, a displacement sensor 46 and an arc-shaped clamping plate 45. The arc-shaped clamping plate 45 is a detachable structure. By replacing the arc-shaped clamping plate 45, the pressurization requirements of tunnel lining models of different shapes can be met. The inner surface of the arc-shaped clamping plate 45 is fixedly connected with a rubber pad, and the rubber pad can increase the anti-slip property. The arc-shaped clamping plate 45 is made of metal, and the curvature of the arc-shaped clamping plate 45 is consistent with the curvature of the corresponding part of the tunnel lining specimen 7, thereby ensuring that the tunnel lining specimen 7 is uniformly stressed. The displacement sensor 46 and the pressure sensor 44 form a monitoring system, which is used to monitor the displacement and pressure of the tunnel lining specimen 7 during the test. The data monitored by the displacement sensor 46 and the pressure sensor 44 are fed back to the control system in real time. The control system adjusts the pressurization of the stiffness adjustment cylinder in real time according to the displacement monitored by the displacement sensor 46 and the preset stiffness value. The servo electric cylinder 41 is fixedly mounted on the fixed flange 43. A guide rail is provided below the servo electric cylinder 41. The displacement sensor 46 is assembled and installed at the bottom end of the servo electric cylinder 41. There are two guide rods 42. The setting of the guide rods 42 can be used to limit the loading direction. The guide rods 42 pass through the guide rails, the fixed flange 43 and the sides of the displacement sensor 46. The bottom ends of the two guide rods 42 are equipped with arc-shaped clamping plates 45. The pressure sensor 44 is fixedly installed above the arc-shaped clamping plates 45. The servo electric cylinder 41 consists of a loading cylinder and a stiffness adjustment cylinder.

[0051] The vibration platform 3 is divided into an upper platform 31, a middle platform 32, a lower platform 33, a servo cylinder and a fixed foot 34. The upper platform 31 is assembled on the upper part of the middle platform 32, and the middle platform 32 is assembled on the upper part of the lower platform 33. Servo cylinders are arranged on the upper platform 31 and the middle platform 32. The lower platform 33 is fixed to the fixed foot 34. The fixed foot 34 is installed and fixed on the pre-cast concrete foundation. Since relatively strong vibration will be generated during the test, the middle platform 32 and the lower platform 33 of the vibration platform 3 are prevented from moving the whole machine and interfering with the surrounding environment during the test. The middle platform 32 and the lower platform 33 of the vibration platform 3 are connected by a slide rail. The middle platform 32 generates X-axis movement under the action of the servo cylinder. The upper platform 31 and the middle platform 32 are also connected by a slide rail. The upper platform 31 generates Y-axis movement under the action of the servo cylinder. Through the movement in the direction of the X and Y axes, the tunnel lining specimen 7 can realize unidirectional movement in the X axis or unidirectional movement in the Y axis or synchronous conforming movement in the XY axis. The vibration frequency of the vibration platform 3 is within 0-20Hz.

[0052] Example 1

[0053] This embodiment relates to a method for using a static loading test system for a tunnel lining. The method is based on a servo-controlled variable stiffness tunnel static-dynamic loading test system to meet the requirements of different stiffness loading tests, and specifically includes the following steps:

[0054] Firstly, according to the size of the test system and the provided load limit value, the geometric similarity ratio and strength similarity ratio of the tunnel lining specimen 7 are determined, and the mass ratio of gypsum and water is adjusted according to the determined strength similarity ratio to cast the tunnel lining specimen 7 with strength meeting the requirements, and the cast tunnel lining specimen 7 is cured. After the curing is completed, the tunnel lining specimen 7 is fixed on the lining fixed base 6, and the number and pressurizing position of the pressure head assembly 4 are selected according to the test requirements, and the initial position of the arc clamping plate 45 is adjusted. During static loading, the vibration platform 3 remains fixed and is in a non-working state.

[0055] This example takes the lining with cavities in the vault as an example, but the test system is not limited to cavities, and can also be lining with cracks, lining with strength attenuation, etc. Figure 5 The cross section of the tunnel lining specimen 7 is divided into various parts. The arc-shaped clamping plate 45 of the pressure head assembly 4 at the arch top position does not fit the outer surface of the tunnel lining specimen 7, thereby realizing the simulation of the cavity behind the tunnel lining specimen 7. According to the on-site investigation, it is found that there will be stress concentration near the lining cavity. Therefore, the pressure of the pressure head assembly 4 at the arch shoulder position of the tunnel lining specimen is selected as the yield strength evaluation index of the lining. After the tunnel lining specimen 7 is installed, the preset stiffness required for the test is set, and then the servo electric cylinder 41 starts to pressurize the lining through the arc-shaped clamping plate 45. After the tunnel lining specimen 7 is loaded, the displacement sensor 46 and the pressure sensor 44 transmit the data in real time. The data is transmitted to the control system. The control system adjusts the actual loading pressure of the stiffness adjustment cylinder in real time according to the data fed back by the displacement sensor 46 and the preset stiffness. The pressure head assembly 4 continues to load and ensures that the loading stiffness meets the preset stiffness and remains constant until the tunnel lining specimen 7 is unstable and damaged. The loading test is completed and the peak pressure of the pressure head assembly 4 at the spandrel is recorded as the yield strength of the tunnel lining specimen 7. During the test, a high-pixel camera is used to collect the deformation and crack evolution characteristics of the key parts of the lining specimen during the test. Different loading stiffnesses are adjusted and loaded multiple times. The specimen loading test under different loading stiffnesses can be carried out. Figure 6 The yield strength of tunnel lining specimen 7 under different stiffness, that is, under different surrounding rock grade characterizations, when the arch contains cavities of different sizes, is shown. It can be seen that with the increase of surrounding rock grade, the yield strength of the lining is significantly improved.

[0056] Example 2

[0057] This embodiment relates to a method for using vibration loading of a tunnel lining test system. The method is based on a servo-controlled variable stiffness tunnel static-dynamic loading test system, realizes the requirements of loading tests under dynamic load conditions, and specifically includes the following steps:

[0058] Before dynamic load loading, fix the tunnel lining specimen 7 on the lining fixed base 6, paste the strain gauge on the inner surface of the tunnel lining specimen 7, adjust the position of the arc clamping plate 45 of the pressure head assembly 4 to make it fit with the outer surface of the tunnel lining specimen 7, and then adjust the actual loading pressure and stiffness value of the servo electric cylinder 41 to the preset test value. This process can also be completed with reference to Example 1. When the dynamic load is loaded, the seismic wave excitation signals with different vibration frequencies and vibration intensities are input into the vibration platform 3 through the control system to realize unidirectional motion in the X-axis direction or unidirectional motion in the Y-axis direction or synchronous composite motion in the XY axis. Record the dynamic strain of the arch top position, such as Figure 7 shown. Figure 8 The strain extremes of the arch crown under different seismic wave intensities are shown. It can be seen that the tensile and compressive strains increase significantly with the increase of seismic intensity, and the tunnel lining specimen 7 is seriously damaged.

[0059] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​(e.g., temperature, pressure, etc.), installation arrangement, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to numerous modifications still falling within the scope of the appended claims.

[0060] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0061] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0062] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A servo-controlled variable stiffness tunnel lining static-dynamic loading test system, characterized in that: The servo-controlled variable stiffness test system includes a variable stiffness test loading system, a monitoring system, a vibration platform (3), a hydraulic pump station and a control system; The variable stiffness test loading system comprises a first reaction frame (1), a second reaction frame (2), a first support (5), a second support (8), a pressure head assembly (4) and a lining fixing base (6); A tunnel lining specimen (7) is provided inside the first reaction frame (1) and the second reaction frame (2); one end face of the first support (5) is fixed to the first reaction frame (1) and the second reaction frame (2) by bolts; the other end face of the first support (5) is fixedly connected to the vibration platform (3) by bolts; one end face of the second support (8) is fixed to the first reaction frame (1) and the second reaction frame (2) by bolts; and the other end face of the second support (8) is fixedly connected to the vibration platform (3) by bolts; There are four lining fixing bases (6), and the tunnel lining test piece (7) is arranged on the lining fixing base (6). The lining fixing base (6) is located between the first support (5) and the second support (8), and is fixedly connected to the first support (5) and the second support (8) by bolts. The pressure head assembly (4) is composed of a servo electric cylinder (41), a guide rod (42), a fixed flange (43), a pressure sensor (44), a displacement sensor (46) and an arc-shaped clamping plate (45); the servo electric cylinder (41) is fixedly mounted on the fixed flange (43); a guide rail is provided below the servo electric cylinder (41); the displacement sensor (46) is mounted on the bottom end of the servo electric cylinder (41); there are two guide rods (42); the guide rods (42) penetrate the guide rail, the fixed flange (43) and the side of the displacement sensor (46); the bottom ends of the two guide rods (42) are equipped with an arc-shaped clamping plate (45); the pressure sensor (44) is fixedly mounted on the top of the arc-shaped clamping plate (45); The vibration platform (3) is divided into an upper platform (31), a middle platform (32), a lower platform (33), a servo cylinder and a fixed foot (34); the upper platform (31) is mounted above the middle platform (32); the middle platform (32) is mounted above the lower platform (33); the servo cylinder is arranged on the upper platform (31) and the middle platform (32); and the lower platform (33) is fixed to the fixed foot (34); The middle platform (32) and the lower platform (33) of the vibration platform (3) are connected by a slide rail, and the middle platform (32) generates X-axial movement under the action of the servo cylinder; The upper platform (31) and the middle platform (32) are also connected by a slide rail, and the upper platform (31) generates Y-axis movement under the action of the servo cylinder; The vibration frequency of the vibration platform (3) is within 0-20 Hz; The first reaction frame (1) and the second reaction frame (2) are each provided with nine mounting holes (11), a scale line is provided on one side of each mounting hole (11), and the annular spacing of the mounting holes (11) is 22.5°; Two pressing head assemblies (4) are mounted on each mounting hole (11) of the first reaction frame (1) and the second reaction frame (2), and the fixing flange (43) and the guide rail cooperate to enable the pressing head assembly (4) to slide linearly in the mounting hole (11); The data monitored by the displacement sensor (46) and the pressure sensor (44) are fed back to the control system in real time, and the control system adjusts the pressurization of the stiffness regulating cylinder in real time according to the displacement monitored by the displacement sensor (46) and a preset stiffness value.

2. A servo-controlled variable stiffness tunnel lining static-dynamic loading test system as claimed in claim 1, characterized in that: The displacement sensor (46) and the pressure sensor (44) constitute a monitoring system.

3. A servo-controlled variable stiffness tunnel lining static-dynamic loading test system as claimed in claim 1, characterized in that: The axial lengths of the first reaction frame (1) and the second reaction frame (2) are respectively 1 m; The axial lengths of the first support (5) and the second support (8) are respectively 2 m.

4. A servo-controlled variable stiffness tunnel lining static-dynamic loading test system as claimed in claim 1, characterized in that: The arc-shaped clamping plate (45) is a detachable structure, and a rubber pad is fixedly connected to the inner surface of the arc-shaped clamping plate (45); The arc-shaped clamping plate (45) is made of metal, and the curvature of the arc-shaped clamping plate (45) is consistent with the curvature of the corresponding part of the tunnel lining specimen (7).

5. A servo-controlled variable stiffness tunnel lining static-dynamic loading test system as claimed in claim 1, characterized in that: The servo electric cylinder (41) consists of a loading cylinder and a stiffness adjustment cylinder.

6. A servo-controlled variable stiffness tunnel lining static-dynamic loading test system as claimed in claim 1, characterized in that: The first reaction frame (1) and the second reaction frame (2) are made of Q235 steel and are welded by steel plates and square tubes, and are heat treated and spray-painted after welding.

7. A servo-controlled variable stiffness tunnel lining static-dynamic loading test system as claimed in claim 1, characterized in that: The servo electric cylinder (41) of the pressure head assembly (4) and the servo cylinder of the vibration platform (3) are powered by a hydraulic pump station.

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