Novel heat insulation and energy absorption structure of heat-conductive fault tunnel and test method

Abstract

The present application relates to the technical field of tunnel engineering model test, in particular to a new heat insulation and energy absorption structure of a heat-conductive fault tunnel and a test method, the heat insulation and energy absorption structure is arranged between the primary support and the secondary lining of the heat-conductive fault tunnel, and comprises a ribbed heat insulation and energy absorption layer, the ribbed heat insulation and energy absorption layer comprises a bottom plate close to the secondary lining, a top plate close to the primary support, and a support rib fixed between the bottom plate and the top plate, and the heat insulation effect and the energy consumption capacity are enhanced by introducing air medium. The test method comprises the following steps: a test model is made, which is in a proportionally reduced manner, for the primary support, the secondary lining, and the heat insulation and energy absorption layer between the primary support and the secondary lining, and the outer part of the test model of different types of heat insulation and energy absorption layers is filled with surrounding rock similar material in the model box; the test model is loaded by a vibration table, and sensors synchronously collect various data. The heat and earthquake coupling working conditions of the heat-conductive fault tunnel with high rock temperature and strong earthquake can be truly reproduced, and the defects that the conventional test can only carry out normal temperature and earthquake loading and is difficult to synchronously simulate the high fault temperature environment are made up.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering model testing technology, specifically to a novel heat-insulating and energy-absorbing structure for thermally conductive fault tunnels and its testing method. Background Technology

[0002] Defects such as capillary pores, voids, and material cracks are unavoidable during the pouring and forming of tunnel lining concrete. In thermally conductive fault tunnels, under long-term high-temperature thermal conditions, the stress at these defect locations will concentrate and gradually develop due to the added stress from temperature, forming microcracks. When subjected to seismic forces, these microcracks will further induce progressive damage such as cracking and spalling of the lining, ultimately leading to a decrease in the load-bearing capacity of the lining structure and even collapse. Furthermore, railway operating conditions require that the ambient temperature inside the tunnel not exceed 28℃; otherwise, heat insulation and ventilation control measures must be implemented.

[0003] Therefore, in actual tunnel design and construction, to reduce the transmission of seismic wave energy to the tunnel structure under earthquake action, an elastic energy-absorbing layer is often installed between the initial support and the secondary lining. This layer utilizes its elastic deformation to achieve seismic isolation and vibration reduction. Based on this, high-damping rubber is selected as the main material for the energy-absorbing layer. This material has both a low thermal conductivity and good damping energy dissipation characteristics, thus achieving both heat insulation and vibration reduction simultaneously.

[0004] To further enhance its thermal insulation and deformation energy dissipation performance, this invention incorporates a ribbed structure design on the basis of a solid thermal insulation and energy-absorbing layer, introducing air as a medium to enhance the thermal insulation effect and energy dissipation capacity. Through simulation experiments on the thermal insulation and vibration reduction performance of the thermal insulation and energy-absorbing structure, and considering safety and economy, a suitable thermal insulation and energy-absorbing structure is selected to assess the structural stability of the thermally conductive fault tunnel section under seismic loading. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a novel heat-insulating and energy-absorbing structure for thermally conductive fault tunnels. This structure features a ribbed design based on a solid heat-insulating and energy-absorbing layer, and enhances heat insulation and energy dissipation capacity by introducing air as a medium. Through simulation experiments on the heat insulation and vibration damping performance of the heat-insulating and energy-absorbing structure, and considering both safety and economy, a suitable heat-insulating and energy-absorbing structure is selected.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A novel heat-insulating and energy-absorbing structure for thermally conductive fault tunnels is provided, which is installed between the primary support and secondary lining of the tunnel. It includes a ribbed heat-insulating and energy-absorbing layer, comprising a bottom plate near the secondary lining, a top plate near the primary support, and supporting ribs fixed between the bottom and top plates. The thickness of the top plate, the bottom plate, and the height of the supporting ribs are all 6-10 cm, the width of the supporting ribs is 8-12 cm, and the ratio of rib spacing to rib width is 0.2-0.4. The ribbed heat-insulating and energy-absorbing layer uses foamed sponge rubber with a density of 120±20 kg / m³ and a tensile strength greater than 0.08 MPa as the base material.

[0008] As one embodiment of the present invention, it also includes a solid heat-insulating and energy-absorbing layer with a thickness of 13-17cm; according to the structural stability of the thermally conductive fault tunnel under seismic action, the tunnel is divided into sections with different degrees of influence along the longitudinal direction; the ribbed heat-insulating and energy-absorbing layer is set in the high-influence zone, and the solid heat-insulating and energy-absorbing layer is set in the medium-influence zone.

[0009] In one embodiment of the present invention, both the ribbed heat-insulating and energy-absorbing layer and the solid heat-insulating and energy-absorbing layer are made of EPDM foamed sponge rubber.

[0010] In one embodiment of the present invention, the thickness of the top plate, the thickness of the bottom plate, and the height of the supporting rib are all 8cm, the width of the supporting rib is 10cm, and the ratio of the rib spacing to the rib width is 0.3; the thickness of the solid heat insulation and energy absorption layer is 15cm.

[0011] A novel test method for thermally conductive fault tunnel insulation and energy-absorbing structures involves fabricating a scaled-down test model of the primary support, secondary lining, and the insulation and energy-absorbing layer between them. Different types of insulation and energy-absorbing layers are filled with similar surrounding rock materials inside the model box. The test model is then loaded using a vibration table, and sensors simultaneously collect various data.

[0012] The experimental model making includes:

[0013] Acceleration sensors, temperature sensors, and strain gauges are installed at designated locations in the precast secondary lining.

[0014] A ribbed or solid heat-absorbing layer is installed on the outside of the secondary lining. Structural joints are pre-set at the left and right arch feet of the tunnel. First, the heat-absorbing layer is temporarily fixed by tightly attaching it to the outer surface of the precast secondary lining with tape. Then, double-sided tape is used to stick the end face of the heat-absorbing layer at the structural joint to achieve a seal.

[0015] The precast secondary lining, after the heat insulation and energy absorption layer installation is completed, is hoisted into the mold box. A waterproof membrane is placed on the outside of the heat insulation and energy absorption layer. After the waterproof membrane is tightly bonded to the heat insulation and energy absorption layer, gypsum admixture is evenly applied to the surface of the waterproof membrane to simulate the initial support.

[0016] After the gypsum admixture has initially solidified, subsequent filling operations using similar surrounding rock materials will commence. Acceleration sensors and temperature sensors will be deployed during the filling process. The filling operation will employ a layered compaction method, following geological zoning for layer-by-layer filling and compaction.

[0017] Experimental model loading:

[0018] The temperature of the test model is controlled by the heating system inside the model box, so that the temperature conditions and heating conditions of the ribbed heat-absorbing layer test model and the solid heat-absorbing layer test model are consistent. After the temperature of the test model reaches the test temperature and the temperature field remains stable, heating is stopped and the model is kept warm by heating plate.

[0019] According to the test loading scheme, dynamic loading was carried out through a vibration table, and the sensors simultaneously collected various data.

[0020] As one embodiment of the present invention, the ribbed heat insulation and energy absorption layer includes a bottom plate near the secondary lining, a top plate near the primary support, and a support rib fixed between the bottom plate and the top plate. For ease of fabrication, the ribbed heat insulation and energy absorption layer in the test model includes a top plate and a support rib in contact with the surface of the secondary lining.

[0021] As one embodiment of the present invention, the precast secondary lining is composed of three precast segmental lining sections spliced ​​together; the test method mainly monitors the thermally conductive fault lining section located in the middle, with three monitoring surfaces set on the thermally conductive fault lining section in the middle and one monitoring surface set on each of the lining sections on both sides. Accelerometers are arranged along the dip of the surrounding rock cross-section; in the footwall surrounding rock, accelerometers are arranged along the direction perpendicular to the fault; and in the hanging wall surrounding rock, accelerometers are arranged along the X direction. Accelerometers are installed on the central monitoring face of the thermally conductive fault lining segment, circumferentially on the arch, left wall, invert, and right wall. Meanwhile, accelerometers are installed along the longitudinal direction of the tunnel at the invert position of the tunnel lining on the other four monitoring faces. A PT100 resistance temperature sensor is buried along the thermally conductive fault in the Z direction at a height of 45cm; temperature sensors are installed longitudinally inside and outside the tunnel secondary lining arch; and temperature sensors are buried in the surrounding rock at a specific location of 5cm from the tunnel arch foot to the horizontal distance of the tunnel lining. Circumferential strain gauges were placed on the inner and outer surfaces of the lining structure at the arch, left and right side walls, and invert arch at the five monitoring surfaces, while axial strain gauges were placed at the arch.

[0022] As one embodiment of the present invention, when the shaking table is subjected to dynamic loading, six different seismic waves with peak ground motion values ​​of 0.1g, 0.2g, 0.3g, 0.4g, 0.6g and 0.8g are loaded. The direction of the input seismic wave is perpendicular to the tunnel axis. Before the formal loading, a 0.05g seismic wave is input for preloading. When the peak ground motion value of the seismic wave changes, a 0.05g white noise is input for loading.

[0023] As one embodiment of the present invention, when filling layer by layer according to geological zoning, the surrounding rock grade of the tunnel axially crossing the upper and lower plates and the distribution of heat-conducting faults is determined by the geological exploration results. The surrounding rock similar material is prepared in the corresponding mix ratio of the raw materials. The surrounding rock similar material is filled into the model box in layers. After each layer is compacted, the density is checked by ring sampler until the standard is met. In the heat-conducting fault area, in order to enhance the heat conduction characteristics, the surrounding rock similar material is mixed with iron powder at a mass ratio of 3:1 and then filled in.

[0024] After filling to the design elevation of the tunnel floor, the prefabricated secondary lining with sensors installed is hoisted into the mold box; a 0.5-mil thick linear low-density polyethylene film is laid on the outer wall of the energy-absorbing and heat-insulating layer to simulate a waterproof membrane.

[0025] Similar materials to the surrounding rock are filled in layers above and around the precast secondary lining until the final filling height designed for the model box is reached.

[0026] As one embodiment of the present invention, the heat insulation and energy absorption layer also includes an uninsulated heat insulation and energy absorption layer. The heat insulation performance and vibration reduction performance are analyzed by collecting data from sensors under three working conditions: an uninsulated heat insulation and energy absorption layer, a solid heat insulation and energy absorption layer, and a ribbed heat insulation and energy absorption layer. Considering safety and economy, appropriate heat insulation and energy absorption layer parameters and types are selected based on the strength of the affected area.

[0027] The beneficial effects of adopting the above technical solution are as follows:

[0028] The installation of a heat-insulating and energy-absorbing layer can effectively improve the uniformity of stress distribution and the consistency of deformation in the tunnel lining structure. After the installation of the heat-insulating and energy-absorbing layer, cracks are mainly distributed in weak parts such as the invert and crown, and crack development in the thermally conductive fault section is still relatively prominent. The ribbed heat-insulating and energy-absorbing layer provided by this invention, due to the optimization of the rib structure, exhibits a more significant heat insulation effect near the thermally conductive fault and in the fault region, which can significantly slow down crack propagation and local damage, effectively improving the overall seismic performance of the tunnel structure. Considering both heat insulation and vibration reduction effects and economy, the ribbed heat-insulating and energy-absorbing layer structure is used in the high-impact section, while the solid heat-insulating and energy-absorbing layer structure is used in the medium-impact section, which can achieve better heat insulation and energy absorption effects and is the choice for the coordinated control of tunnel heat insulation and vibration reduction.

[0029] The aforementioned experimental method was used to conduct comparative experiments on ribbed, solid, and unsupported thermal insulation energy absorption layer test models, eliminating systematic errors caused by factors such as materials, filling, and boundaries between multiple models. This provides a reliable experimental basis for the selection of thermal insulation energy absorption layer type, the thickness of solid thermal insulation energy absorption layer, and the optimization of key parameters such as rib spacing, rib width, and thickness of ribbed thermal insulation energy absorption layer.

[0030] The experimental method described above can realistically reproduce the thermal-seismic coupling conditions of high rock temperature and strong earthquake in thermally conductive fault tunnels, making up for the shortcomings of conventional tests which can only carry out normal temperature earthquake loading and are difficult to simultaneously simulate the high ground temperature environment of faults.

[0031] A steady-state temperature field was established inside the test model using a heating system. Before vibration loading, the hot water in the heat pipes was drained and the external pipeline of the heating device was disconnected. The high-temperature boundary condition of 80°C of the fault was maintained by the heating plate pre-embedded inside the fault. This avoided additional constraints and external force interference from the external pipeline when loading the model box through the vibration table, ensuring the accuracy of the seismic wave input. The test boundary conditions were closer to the real engineering environment of the heat-conducting fault tunnel, and the test data had high reliability. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the ribbed heat insulation and energy absorption layer in this invention.

[0033] Figure 2 This is a partially enlarged schematic diagram of the ribbed heat-insulating and energy-absorbing layer in this invention.

[0034] Figure 3 This is a schematic diagram of the elevation layout of the surrounding rock acceleration sensor in this invention.

[0035] Figure 4 This is a schematic diagram of the longitudinal arrangement of the secondary lining accelerometer in this invention.

[0036] Figure 5 This is a schematic diagram of the planar layout of the surrounding rock temperature sensor in this invention.

[0037] Figure 6 This is a schematic diagram of the arrangement of the temperature sensors in the secondary lining of this invention.

[0038] Figure 7 This is a schematic diagram of the lining structure in this invention.

[0039] The structure consists of: 1. Primary support, 2. Ribbed heat insulation and energy absorption layer, 3. Secondary lining, 4. Top plate, 5. Bottom plate, and 6. Supporting ribs. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the invention will be described clearly and completely below in conjunction with specific embodiments.

[0041] like Figure 1 and Figure 2 The diagram illustrates a novel heat-insulating and energy-absorbing structure for thermally conductive fault tunnels. This structure is installed between the initial support 1 and the secondary lining 3 (initial support and secondary lining) of the tunnel. It includes a ribbed heat-insulating and energy-absorbing layer 2. The ribbed heat-insulating and energy-absorbing layer 2 comprises a bottom plate 5 near the secondary lining 3, a top plate 4 near the initial support 1, and supporting ribs 6 fixed between the bottom plate 5 and the top plate 4. The thickness of the top plate 4, the thickness of the bottom plate 5, and the height of the supporting ribs 6 are all 6-10 cm, the width of the supporting ribs 6 is 8-12 cm, and the ratio of rib spacing to rib width is 0.2-0.4. The ribbed heat-insulating and energy-absorbing layer 2 uses a material with a density of 120±20 kg / m³. 3 The base material is foamed sponge rubber with a tensile strength greater than 0.08 MPa. This material has both a low thermal conductivity and good damping energy dissipation characteristics, and can achieve both heat insulation and shock absorption. The ribbed heat insulation and energy absorption layer 2 enhances the heat insulation effect and energy dissipation capacity by introducing air medium.

[0042] As a feasible example, the heat insulation and energy absorption structure also includes a solid heat insulation and energy absorption layer with a thickness of 13-17 cm; based on the structural stability of the thermally conductive fault tunnel under seismic loading, the tunnel is divided longitudinally into sections with different levels of influence; the ribbed heat insulation and energy absorption layer 2 is located in the high-influence zone, and the solid heat insulation and energy absorption layer is located in the medium-influence zone. The zoning criteria for the thermally conductive fault tunnel are shown in Table 1.

[0043] Table 1 Earthquake Impact Zoning Standards

[0044]

[0046] In this embodiment, both the ribbed heat-absorbing layer 2 and the solid heat-absorbing layer are made of EPDM foamed sponge rubber. Its elongation at break is >150%, its applicable temperature is -20~120℃, and its elastic modulus is 1.5MPa.

[0047] Preferably, the thickness of the top plate 4, the thickness of the bottom plate 5, and the height of the supporting rib 6 are all 8cm, the width of the supporting rib 6 is 10cm, and the ratio of the rib spacing to the rib width is 0.3; the thickness of the solid heat insulation and energy absorption layer is 15cm.

[0048] This invention also provides a test method for a novel heat-insulating and energy-absorbing structure for thermally conductive fault tunnels, which includes: making a test model that is proportionally scaled down to the primary support 1, the secondary lining 3, and the heat-insulating and energy-absorbing layer between them; filling the test model with surrounding rock similar materials for different types of heat-insulating and energy-absorbing layers in the model box; loading the test model with a vibration table; and simultaneously collecting various data with sensors.

[0049] Specifically, the experimental model making includes:

[0050] After the prefabrication of similar materials to the tunnel lining 3 and the surrounding rock was completed, the test model was fabricated according to the following procedure:

[0051] First, the precast lining is treated with wood wax oil for moisture protection and dried thoroughly. Acceleration sensors, temperature sensors and strain gauges are installed at designated locations in the precast secondary lining according to the monitoring plan.

[0052] A ribbed or solid heat-absorbing layer is installed on the outside of the secondary lining (3). In actual tunnel engineering, the heat-absorbing layer is usually connected to the primary support structure by bonding or mechanical fixing to ensure that it forms a continuous and integral load-bearing system with the surrounding rock and lining. However, under the coupled effects of high temperature and strong earthquake, this conventional installation method is prone to interface performance degradation due to aging of the bonding material or stress concentration, affecting the long-term stability of the heat insulation and vibration reduction effects. Therefore, this case adopts an installation process that avoids direct contact between the adhesive and the secondary lining in the model test. During installation, to eliminate the influence of the adhesive on the load-bearing performance of the lining and to simulate the heat insulation and vibration reduction effect of the heat-absorbing layer under the worst case, no adhesive material is used at the contact surface between the heat-absorbing layer and the secondary lining (3). The specific steps are as follows: pre-set structural joints at the left and right arch feet of the tunnel. First, use tape to temporarily fix the heat insulation and energy absorption layer tightly to the outer surface of the precast secondary lining. Then, use double-sided tape to stick the end face of the heat insulation and energy absorption layer at the structural joint to achieve a seal. This method avoids direct contact between the adhesive and the secondary lining 3, and does not interfere with the simulation of the subsequent initial support.

[0053] The precast secondary lining with the completed heat insulation and energy absorption layer is hoisted into the mold box. A waterproof membrane is placed on the outside of the heat insulation and energy absorption layer. After the waterproof membrane is tightly bonded to the heat insulation and energy absorption layer, gypsum admixture is evenly applied to the surface of the waterproof membrane to simulate the initial support 1.

[0054] After the gypsum admixture has initially solidified, the subsequent filling operation of similar surrounding rock materials will be carried out. During the filling process, acceleration sensors and temperature sensors will be installed. The filling operation adopts the layered compaction method, and the filling and compaction will be carried out layer by layer according to the geological zoning.

[0055] Experimental model loading:

[0056] The temperature of the surrounding rock and secondary lining 3 of the test model is controlled by the heating system inside the model box, ensuring that the temperature conditions and heating status of the ribbed heat-absorbing layer 2 test model and the solid heat-absorbing layer test model are consistent. After the temperature of the surrounding rock and secondary lining 3 of the test model reaches the test temperature and the temperature field remains stable, heating is stopped and the model is kept warm by heating plates. In this embodiment, the test temperature is 80℃ and the room temperature is 15℃. To improve test efficiency and shorten the time required for the test model to heat up, the heating system is started simultaneously during the model box filling stage to preheat the surrounding rock. After the model filling is completed, the temperature acquisition system is turned on to continuously monitor and record the temperature changes inside the surrounding rock and lining. After about 3 days of continuous heating and heat conduction, the readings of each temperature measuring point gradually stabilize, and a steady-state temperature field has been formed inside the test model. The connection between the heat pipe system and the model box is disconnected, and heating plates are used for insulation to maintain the predetermined temperature conditions. Then, according to the pre-set vibration table loading conditions in the test loading scheme, dynamic loading was carried out through the vibration table to conduct thermal insulation and vibration reduction performance tests on the thermally conductive fault tunnel in sequence, while sensors simultaneously collected various data. The heating plate was placed 20cm away from the bottom of the fault inside the fault during the filling of the test model.

[0057] As a further optimization, the ribbed heat insulation and energy absorption layer 2 includes a bottom plate 5 near the secondary lining 3, a top plate 4 near the primary support 1, and a support rib 6 fixed between the bottom plate 5 and the top plate 4. For ease of fabrication, the ribbed heat insulation and energy absorption layer 2 in the test model includes a top plate 4 and a support rib 6 in contact with the surface of the secondary lining 3. During installation, the ribbed heat insulation and energy absorption layer 2 contacts the surface of the secondary lining 3 with its support ribs, and the surface of the secondary lining 3 acts as the bottom plate 5.

[0058] As a feasible example, the precast secondary lining is composed of three precast segmental lining sections, each 30cm long, for a total length of 90cm. The precast secondary lining structure is designed to be 12mm thick. In terms of materials, gypsum admixture is used to simulate C30 concrete, which possesses the corresponding mechanical properties after hardening. Simultaneously, galvanized steel wire mesh with a diameter of 0.7mm and a spacing of 18mm is used, simplifying the simulation of the secondary lining's circumferential and longitudinal reinforcement according to the principle of strength equivalence, and uniformly laying one layer of wire mesh.

[0059] The test method mainly monitors the thermally conductive fault lining segment ② located in the middle. Three monitoring surfaces #2 to #4 are set on the thermally conductive fault lining segment ②, and monitoring surfaces #1 and #5 are set on the lining segments ① and ③, respectively.

[0060] To study the acceleration response characteristics of the thermally conductive fault and the interface between the hanging wall and footwall, acceleration sensors were placed at specific locations inside the test model. (Refer to...) Figure 3Accelerometers ZA-1 to ZA-4 are arranged along the dip direction (Z direction) of the surrounding rock section. Accelerometers XA-11 to XA-14 are arranged in the footwall surrounding rock along the vertical fault direction (X direction), with XA-11 and ZA-1 sharing a measuring point. XA-41 to XA-44 are arranged in the hanging wall surrounding rock along the X direction, with XA-41 and ZA-4 sharing the same measuring point.

[0061] Reference Figure 4 Accelerometers a3-1 to a3-4 are installed on the circumferential arch, left wall, invert, and right wall of monitoring face 3 within the thermally conductive fault. At the same time, accelerometers a1-3 to a5-3 are installed along the longitudinal direction of the tunnel at the invert position of the tunnel lining on monitoring faces 1, 2, 4, and 5.

[0062] Reference Figure 5 To study the temperature distribution characteristics of the thermally conductive fault and the surrounding rocks of the hanging wall and footwall, PT100 resistance temperature sensors T1~T9 were installed along the thermally conductive fault in the Z direction, and temperature sensors XT1~XT7 were installed at a height of 45cm; (Refer to...) Figure 6 To study the heat insulation effect of tunnel secondary lining 3, temperature sensors K1-1~K5-1 and K1-2~K5-2 were installed longitudinally inside and outside the invert arch of tunnel secondary lining 3. To study the temperature field of the surrounding rock of the tunnel with thermal fault, temperature sensors were buried in the surrounding rock. Specifically, temperature sensors K1-3~K1-5, K2-3~K2-5, K3-3~K3-5, K4-3~K4-5, and K5-3~K5-5 were buried at a horizontal distance of 5cm from the tunnel lining at the height of the tunnel arch foot (35cm).

[0063] Reference Figure 7 Circumferential strain gauges were placed on the inner and outer surfaces of the lining structure of monitoring surfaces #1 to #5 at the arch top, left and right side walls and invert arch, and axial strain gauges were placed at the arch top.

[0064] As a feasible example, referring to Table 2, when the shaking table is subjected to dynamic loading, six different seismic waves with peak ground motions of 0.1g, 0.2g, 0.3g, 0.4g, 0.6g and 0.8g are loaded. In the experiment, the direction of the input seismic wave is perpendicular to the tunnel axis. Before the formal loading, a 0.05g seismic wave is input for preloading, and when the peak ground motion of the seismic wave changes, a 0.05g white noise is input for loading.

[0065] Table 2 Loading conditions for shaking table test

[0066]

[0067] As a feasible example, when constructing the tunnel layer by layer according to geological zoning, the surrounding rock grade of the tunnel's axial crossing of the hanging wall, footwall, and thermal fault distribution is determined based on the geological exploration results. Surrounding rock similar materials are prepared according to the corresponding mix proportions of raw materials to maximize the replication of the actual material composition of the hanging wall, footwall, and surrounding rock of the thermal fault tunnel. The surrounding rock similar materials are filled into the model box in layers, and the density is checked by ring sampler after each layer is compacted until it meets the standard. In the thermal fault area, to enhance heat conduction characteristics, the surrounding rock similar materials are mixed with iron powder at a mass ratio of 3:1 before being filled in.

[0068] After filling to the design elevation of the tunnel floor, the precast secondary lining with sensors installed is hoisted into the mold box; a 0.5 mil (approximately 0.0125 mm) thick linear low-density polyethylene (LLDPE) film is laid on the outer wall of the heat insulation and energy absorption layer to simulate a waterproof membrane.

[0069] Similar materials to the surrounding rock were filled in layers above and around the precast secondary lining, and the same layer-by-layer compaction and density control were carried out until the final filling height designed for the model box was reached.

[0070] As an example of implementation, the heating system includes a heat-conducting pipe located at the bottom of the model box and below the heat-conducting fault area, and a heating device located outside the model box, with a circulation pump realizing the circulation of the heat-conducting medium.

[0071] As an example, the heat insulation and energy absorption layer also includes an uninsulated heat insulation and energy absorption layer (without an insulation and energy absorption layer) as a control group. The heat insulation performance and vibration reduction performance are analyzed by collecting data from sensors under three working conditions: uninsulated heat insulation and energy absorption layer, solid heat insulation and energy absorption layer, and ribbed heat insulation and energy absorption layer 2. Considering safety and economy, appropriate heat insulation and energy absorption layer parameters and types are selected based on the strength of the affected area.

[0072] By repeatedly conducting multiple sets of tests to adjust different combinations of parameters such as the thickness of the top plate 4, the thickness of the bottom plate 5, the height and width of the supporting ribs 6, the rib spacing and rib width ratio, the material and density of the heat insulation and energy absorption layer, and the tensile strength, the optimal parameter combination was obtained. At the same time, considering safety and economy, appropriate heat insulation and energy absorption layer parameters and types (ribbed / solid) were selected for the strength of the affected area.

[0073] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A novel heat-insulating and energy-absorbing structure for thermally conductive fault tunnels, disposed between the primary support and secondary lining of the tunnel, characterized in that: It includes a ribbed heat-absorbing and energy-insulating layer, which comprises a bottom plate near the secondary lining, a top plate near the primary support, and supporting ribs fixed between the bottom plate and the top plate. The thickness of the top plate, the thickness of the bottom plate, and the height of the supporting ribs are all 6-10 cm, the width of the supporting ribs is 8-12 cm, and the ratio of the rib spacing to the rib width is 0.2-0.

4. The ribbed heat-absorbing and energy-insulating layer uses a material with a density of 120±20 kg / m³. 3 The base material is foamed sponge rubber with a tensile strength greater than 0.08MPa.

2. The novel heat-insulating and energy-absorbing structure for a thermally conductive fault tunnel according to claim 1, characterized in that: It also includes a solid heat-insulating and energy-absorbing layer with a thickness of 13-17cm; based on the structural stability of the thermally conductive fault tunnel under seismic action, the tunnel is divided into sections with different degrees of influence along the longitudinal direction; the ribbed heat-insulating and energy-absorbing layer is set in the high-influence zone, and the solid heat-insulating and energy-absorbing layer is set in the medium-influence zone.

3. The novel heat-insulating and energy-absorbing structure for a thermally conductive fault tunnel according to claim 2, characterized in that: Both the ribbed heat-absorbing layer and the solid heat-absorbing layer are made of EPDM foamed sponge rubber.

4. A novel heat-insulating and energy-absorbing structure for a thermally conductive fault tunnel according to claim 2 or 3, characterized in that: The thickness of the top plate, the thickness of the bottom plate, and the height of the supporting ribs are all 8cm, the width of the supporting ribs is 10cm, and the ratio of the rib spacing to the rib width is 0.3; the thickness of the solid heat insulation and energy absorption layer is 15cm.

5. A test method for a novel heat-insulating and energy-absorbing structure for thermally conductive fault tunnels, characterized in that, A scaled-down test model of the primary support, secondary lining, and the heat-absorbing layer between them was constructed. The test model of different types of heat-absorbing layers was filled with surrounding rock similar materials inside the model box. The test model was loaded with a vibration table, and the sensors collected various data simultaneously. The experimental model making includes: Acceleration sensors, temperature sensors, and strain gauges are installed at designated locations in the precast secondary lining. A ribbed or solid heat-absorbing layer is installed on the outside of the secondary lining. Structural joints are pre-set at the left and right arch feet of the tunnel. First, the heat-absorbing layer is temporarily fixed by tightly attaching it to the outer surface of the precast secondary lining with tape. Then, double-sided tape is used to stick the end face of the heat-absorbing layer at the structural joint to achieve a seal. The precast secondary lining, after the heat insulation and energy absorption layer installation is completed, is hoisted into the mold box. A waterproof membrane is placed on the outside of the heat insulation and energy absorption layer. After the waterproof membrane is tightly bonded to the heat insulation and energy absorption layer, gypsum admixture is evenly applied to the surface of the waterproof membrane to simulate the initial support. After the gypsum admixture has initially solidified, subsequent filling operations using similar surrounding rock materials will commence. Acceleration sensors and temperature sensors will be deployed during the filling process. The filling operation will employ a layered compaction method, following geological zoning for layer-by-layer filling and compaction. Experimental model loading: The temperature of the test model is controlled by the heating system inside the model box, so that the temperature conditions and heating conditions of the ribbed heat-absorbing layer test model and the solid heat-absorbing layer test model are consistent. After the temperature of the test model reaches the test temperature and the temperature field remains stable, heating is stopped and the model is kept warm by heating plate. According to the test loading scheme, dynamic loading was carried out through a vibration table, and the sensors simultaneously collected various data.

6. The test method for a novel heat-insulating and energy-absorbing structure for a thermally conductive fault tunnel according to claim 5, characterized in that: The ribbed heat insulation and energy absorption layer includes a bottom plate near the secondary lining, a top plate near the primary support, and supporting ribs fixed between the bottom plate and the top plate. For ease of fabrication, the ribbed heat insulation and energy absorption layer in the test model includes a top plate and supporting ribs in contact with the surface of the secondary lining.

7. The test method for a novel heat-insulating and energy-absorbing structure for a thermally conductive fault tunnel according to claim 6, characterized in that: The precast secondary lining is composed of three precast segmental lining sections spliced ​​together; the test method mainly monitors the thermally conductive fault lining section located in the middle, with three monitoring surfaces set on the thermally conductive fault lining section in the middle and one monitoring surface set on each of the lining sections on both sides. Accelerometers are arranged along the dip of the surrounding rock cross-section; in the footwall surrounding rock, accelerometers are arranged along the direction perpendicular to the fault; and in the hanging wall surrounding rock, accelerometers are arranged along the X direction. Accelerometers are installed on the central monitoring face of the thermally conductive fault lining segment, circumferentially on the arch, left wall, invert, and right wall. Meanwhile, accelerometers are installed along the longitudinal direction of the tunnel at the invert position of the tunnel lining on the other four monitoring faces. A PT100 resistance temperature sensor is buried along the thermally conductive fault in the Z direction at a height of 45cm; temperature sensors are installed longitudinally inside and outside the tunnel secondary lining arch; and temperature sensors are buried in the surrounding rock at a specific location of 5cm from the tunnel arch foot to the horizontal distance of the tunnel lining. Circumferential strain gauges were placed on the inner and outer surfaces of the lining structure at the arch, left and right side walls, and invert arch at the five monitoring surfaces, while axial strain gauges were placed at the arch.

8. The test method for a novel heat-insulating and energy-absorbing structure for a thermally conductive fault tunnel according to claim 7, characterized in that: When the shaking table is subjected to dynamic loading, six different seismic waves with peak ground motions of 0.1g, 0.2g, 0.3g, 0.4g, 0.6g and 0.8g are loaded. The direction of the input seismic wave is perpendicular to the tunnel axis. Before the formal loading, a 0.05g seismic wave is input for preloading. When the peak ground motion of the seismic wave changes, a 0.05g white noise is input for loading.

9. The test method for the novel thermal insulation and energy absorption structure of a thermally conductive fault tunnel according to any one of claims 5-8, characterized in that: When filling layer by layer according to geological zoning, based on the surrounding rock grade of the tunnel axially crossing the upper and lower footwalls and thermally conductive faults in the geological exploration results, similar materials for the surrounding rock are prepared according to the corresponding mix ratio of raw materials in the zoning. The surrounding rock similar material was filled into the model box in layers. After each layer was compacted, the density was checked by taking a sample with a ring cutter until it met the standard. In the thermally conductive fault area, in order to enhance the thermal conductivity, the surrounding rock similar material was mixed with iron powder at a mass ratio of 3:1 and then filled in. After filling to the design elevation of the tunnel floor, the precast secondary lining with sensors installed is hoisted into the mold box; a 0.5-mil thick linear low-density polyethylene film is laid on the outer wall of the heat insulation and energy absorption layer to simulate a waterproof membrane; Similar materials to the surrounding rock are filled in layers above and around the precast secondary lining until the final filling height designed for the model box is reached.

10. The test method for a novel heat-insulating and energy-absorbing structure for a thermally conductive fault tunnel according to claim 9, characterized in that: The heat insulation and energy absorption layer also includes an uninsulated heat insulation and energy absorption layer. The heat insulation performance and vibration reduction performance are analyzed by collecting data from sensors under three working conditions: uninsulated heat insulation and energy absorption layer, solid heat insulation and energy absorption layer, and ribbed heat insulation and energy absorption layer. Considering safety and economy, appropriate heat insulation and energy absorption layer parameters and types are selected according to the strength of the affected area.

Images