A seismic isolation method and structure for underground utility tunnels based on wave impedance matching and using lightweight foam soil.

Abstract

This invention discloses a seismic isolation method for underground utility tunnels based on wave impedance matching using foamed lightweight soil. The method includes: S1 determining the performance parameters of the foamed lightweight soil based on the properties of the soil surrounding the underground utility tunnel, and delineating a foamed lightweight soil filling zone around the tunnel; S2 preparing foamed lightweight soil that meets the performance parameters and pouring it into the filling zone to form a continuous foamed lightweight soil filling zone enclosing the area below the tunnel's bottom slab, its sides, and above the top slab. The performance parameters of the foamed lightweight soil satisfy the wave impedance matching relationship, and the pouring thickness of the foamed lightweight soil isolation layer is determined according to a preset correspondence table. This invention is designed based on wave impedance matching theory, scientifically matching the dynamic mechanical characteristics of the isolation layer with the surrounding soil, maximizing the reflection and dissipation of vibration energy, and achieving a leap from empirical vibration reduction to theoretical vibration isolation. It is applicable to improving the seismic resistance and vibration isolation performance of various underground utility tunnels under complex geological conditions.

Description

Technical Field

[0001] This invention relates to the fields of geotechnical engineering and urban underground space engineering, and in particular to a seismic isolation method and structure for underground pipe corridors made of foam lightweight soil based on wave impedance matching. Background Technology

[0002] In the current construction and operation of urban underground utility tunnels, their structural safety and the normal operation of internal pipeline systems face two major vibration threats: one is the occasional but extremely destructive force of earthquakes; the other is long-term environmental vibrations (such as those from nearby subways, road traffic, and industrial equipment operation). Therefore, developing efficient, reliable, durable, and environmentally friendly seismic and vibration isolation technologies for underground utility tunnels has become an urgent need in the field of modern civil engineering.

[0003] Traditional seismic design mainly relies on enhancing the stiffness of the structure itself or implementing complex soil modifications to resist earthquake effects. This approach is not only costly and has limited applicability, but also lacks specialized damping measures for underground structures, making it difficult to effectively control seismic ground pressure and shear wave transmission.

[0004] Currently, vibration isolation methods for underground utility tunnels mainly include barrier isolation, foundation isolation, and replacement. Among them, barrier isolation involves setting up a physical barrier between the vibration source and the protected structure to block the propagation path of vibration waves. It often takes the form of continuous pile walls, open trenches, or filled trenches. However, it has problems such as limited isolation frequency, complex construction, and high cost.

[0005] The foundation isolation method isolates vibration by setting a flexible foundation or vibration isolation bearing at the bottom of the structure. It is suitable for the overall vibration isolation of newly built structures. However, it is extremely difficult and costly to implement for existing underground pipe corridors or linear pipe corridors and tunnels. Furthermore, the vibration isolation bearings have problems such as long-term creep, aging, maintenance and replacement, and their durability in complex underground water and soil environments is challenged.

[0006] The replacement method achieves vibration reduction by partially or completely replacing the original soil around the structure with lightweight materials, thereby reducing the mass and stiffness of the backfill material. Commonly used materials include EPS foam blocks and volcanic slag. However, these materials generally face the contradiction of being lightweight while maintaining high strength and durability. Furthermore, their wave impedance is randomly matched with the soil, resulting in large fluctuations in vibration isolation efficiency and unstable vibration isolation effect.

[0007] In conclusion, there is an urgent need for a new type of earthquake resistance and vibration isolation method that integrates high efficiency in earthquake resistance and vibration isolation, high strength and durability, environmental friendliness and scientific design, in order to address the increasingly serious problems of earthquake safety and vibration interference in urban underground spaces. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a seismic isolation method for underground utility tunnels using foamed lightweight soil based on wave impedance matching. The method is designed based on wave impedance matching theory, which scientifically matches the dynamic mechanical properties of the isolation layer with the surrounding soil. This maximizes the reflection and dissipation of vibration energy from the perspective of wave principle, achieving a leap from "empirical vibration reduction" to "theoretical vibration isolation" and solving the problem of unstable vibration isolation effect in traditional replacement methods.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] A seismic isolation method for underground utility tunnels using foam lightweight soil based on wave impedance matching includes the following steps:

[0011] S1: Based on the properties of the soil surrounding the underground utility tunnel to be protected, determine the required performance parameters and pouring thickness of the foamed lightweight soil, and delineate the foamed lightweight soil filling area surrounding the underground utility tunnel.

[0012] S2: Prepare foamed lightweight soil that meets the performance parameters described in step S1, and pour the foamed lightweight soil into the filling area to form a continuous foamed lightweight soil filling area that covers the bottom slab, the sides, and the top slab of the underground pipe gallery.

[0013] The performance parameters of the foamed lightweight soil and the surrounding soil of the vibration isolation layer satisfy the following wave impedance matching relationship:

[0014] ,

[0015] In the formula, G F It is the shear modulus of foamed lightweight soil, in MPa;

[0016] ρ F This is the density of foamed lightweight soil, in kg / m³. 3 ;

[0017] G s It is the equivalent shear modulus of the soil surrounding the foamed lightweight soil vibration isolation layer, in MPa;

[0018] ρ s It is the equivalent density of the soil surrounding the foamed lightweight soil vibration isolation layer, in kg / m³. 3 ;

[0019] K is the matching coefficient, and K≤0.2.

[0020] Compared with existing technologies, the seismic resistance and vibration isolation method and structure for underground utility tunnels based on foamed lightweight soil provided by this invention have the following significant advantages:

[0021] Three-dimensional all-round protection: By pouring foamed lightweight soil vibration isolation layers in all directions on the bottom slab, side walls and top slab of the underground utility tunnel, a closed three-dimensional vibration isolation system is constructed, which can effectively block and attenuate seismic shear waves and environmental vibrations from all directions, overcoming the traditional method of only setting a vibration damping layer at the top.

[0022] This invention is based on wave impedance matching theory. Through multi-frequency vibration isolation scaled model tests, the wave impedance matching relationship between the performance parameters of foamed lightweight soil and the performance parameters of the surrounding soil of the vibration isolation layer is obtained. This enables the dynamic mechanical properties (the ratio of shear modulus to density) of the vibration isolation layer to be scientifically matched with the surrounding soil. From the wave principle, it maximizes the reflection and dissipation of vibration energy, realizing the leap from "empirical vibration reduction" to "theoretical vibration isolation" and solving the problem of unstable vibration isolation effect of traditional replacement method.

[0023] More preferably, the matching coefficient K is 0.2.

[0024] Beneficial effects: Based on the principle of vibration isolation layer arrangement according to impedance mismatch, combined with the material characteristics of foamed lightweight soil and the needs of engineering practice, the optimal matching coefficient is 0.2.

[0025] More preferably, the density ρ of the foamed lightweight soil F 28-day compressive strength q u And the thickness H of the vibration isolation layer, based on the equivalent shear modulus G of the soil surrounding the foamed lightweight soil vibration isolation layer. s Depending on the differences, the appropriate selection and construction will be carried out according to the preset correspondence.

[0026] More preferably, the preset correspondence is determined by the following table:

[0027] .

[0028] Beneficial effects: As shown in the table above and the accompanying calculation formulas, the optimal density, strength, and vibration isolation layer thickness of foamed lightweight soil can be directly determined based on the soil shear modulus measured on-site. The design process is based on solid evidence and the results are reliable, completely changing the traditional extensive model that relies on engineering experience. The same design system can simultaneously meet the different performance requirements of seismic resistance (to cope with accidental strong earthquakes) and vibration isolation (to cope with long-term micro-vibrations). By adjusting material parameters, such as the differentiated configuration of "seismic-resistant layer" and "vibration isolation layer," multifunctional integration can be achieved, making it more widely applicable.

[0029] Further preferred, the foamed lightweight soil is prepared using cement and industrial solid waste as cementing materials and employing physical or chemical foaming methods.

[0030] Beneficial effects: Utilizing industrial solid waste such as fly ash as raw materials yields significant environmental benefits. Simultaneously, its lightweight nature greatly reduces the additional load on the foundation, lowering structural costs; its excellent vibration isolation performance also extends the service life of the pipe gallery and internal pipelines, resulting in outstanding economic benefits throughout its entire life cycle.

[0031] More preferably, in step S2, the equivalent shear modulus and equivalent density of the surrounding soil are preferably calculated using the parameters of the weak soil layer with the lowest wave impedance, or using equivalent parameters of multi-layer soil weighted by thickness.

[0032] The present invention further discloses an underground utility tunnel seismic isolation structure based on foamed lightweight soil, comprising an underground utility tunnel and a continuous foamed lightweight soil isolation layer wrapped around the underground utility tunnel;

[0033] The foamed lightweight soil vibration isolation layer is filled below the bottom slab, around the sides and above the top slab of the underground pipe gallery, forming a three-dimensional encapsulation structure;

[0034] The dynamic mechanical properties of the foamed lightweight soil satisfy the wave impedance matching relationship described in claim 1.

[0035] Furthermore, the thickness of the foamed lightweight soil vibration isolation layer is determined and constructed according to the shear modulus of the soil surrounding the underground utility tunnel, based on the preset correspondence table.

[0036] Furthermore, this invention discloses a construction method for an underground utility tunnel seismic isolation structure based on foamed lightweight soil. The method involves on-site casting, pumping fluid foamed lightweight soil slurry into the filling area to allow it to self-level and fill, forming a continuous isolation layer. Specifically, the method includes the following steps:

[0037] S1. Cast the foamed lightweight soil isolation layer at the bottom of the underground pipe gallery;

[0038] S2. After the foamed lightweight soil isolation layer at the bottom of the underground utility tunnel has solidified, place the underground utility tunnel on the solidified foamed lightweight soil isolation layer.

[0039] S3. Cast a foamed lightweight soil isolation layer on all four sides of the underground pipe gallery.

[0040] S4. Pour the foamed lightweight soil isolation layer above the top slab.

[0041] This invention further discloses a foamed lightweight soil for seismic resistance and vibration isolation of underground utility tunnels, the dynamic mechanical properties of which are configured to satisfy the following relationship:

[0042] ,

[0043] In the formula, G F It is the shear modulus of foamed lightweight soil, in MPa;

[0044] ρ F This is the density of foamed lightweight soil, in kg / m³. 3 ;

[0045] G s It is the equivalent shear modulus of the soil surrounding the foamed lightweight soil vibration isolation layer, in MPa;

[0046] ρ s It is the equivalent density of the soil surrounding the foamed lightweight soil vibration isolation layer, in kg / m³. 3 ;

[0047] The density ρ of the foamed lightweight soil F 28-day compressive strength q u Based on the shear modulus G of the soil surrounding the foamed lightweight soil vibration isolation layer s The different ranges are adjusted for adaptability in the preset correspondence table as described in claim 4. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the seismic isolation structure of the underground utility tunnel based on foamed lightweight soil according to the present invention.

[0049] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention.

[0050] Among them, 1. Foamed lightweight soil vibration isolation layer; 2. Underground pipe gallery; 3. Seismic load; 4. Surrounding soil; 5. Enclosure structure.

[0051] Figure 3 A comparison of noise curves for when foamed lightweight soil isolation layers are installed and when they are not. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0054] A seismic isolation method for underground utility tunnels using foam lightweight soil based on wave impedance matching includes the following steps:

[0055] S1: Based on the properties of the soil surrounding the underground utility tunnel to be protected, determine the required performance parameters and pouring thickness of the foamed lightweight soil, and delineate the foamed lightweight soil filling area surrounding the underground utility tunnel.

[0056] S2: Prepare foamed lightweight soil that meets the performance parameters described in step S1, and pour the foamed lightweight soil into the filling area to form a continuous foamed lightweight soil filling area that covers the bottom slab, the sides, and the top slab of the underground pipe gallery.

[0057] The performance parameters of the foamed lightweight soil and the surrounding soil of the vibration isolation layer satisfy the following wave impedance matching relationship:

[0058] ,

[0059] In the formula, G F It is the shear modulus of foamed lightweight soil, in MPa;

[0060] ρ F This is the density of foamed lightweight soil, in kg / m³. 3 ;

[0061] G s It is the equivalent shear modulus of the soil surrounding the foamed lightweight soil vibration isolation layer, in MPa;

[0062] ρ s It is the equivalent density of the soil surrounding the foamed lightweight soil vibration isolation layer, in kg / m³. 3 ;

[0063] K is the matching coefficient, and K≤0.2.

[0064] The seismic and vibration isolation method and structure for underground utility tunnels based on foamed lightweight soil provided by this invention has the following significant advantages: Three-dimensional all-round protection: By pouring foamed lightweight soil vibration isolation layers in all directions on the bottom slab, side walls and top slab of the underground utility tunnel, a closed three-dimensional vibration isolation system is constructed, which can effectively block and attenuate seismic shear waves and environmental vibrations from all directions, overcoming the traditional method of only setting a vibration damping layer at the top.

[0065] This invention is based on wave impedance matching theory. Through multi-frequency vibration isolation scaled model tests, the wave impedance matching relationship between the performance parameters of foamed lightweight soil and the performance parameters of the surrounding soil of the vibration isolation layer is obtained. This enables the dynamic mechanical properties (the ratio of shear modulus to density) of the vibration isolation layer to be scientifically matched with the surrounding soil. From the wave principle, it maximizes the reflection and dissipation of vibration energy, realizing the leap from "empirical vibration reduction" to "theoretical vibration isolation" and solving the problem of unstable vibration isolation effect of traditional replacement method.

[0066] As a preferred embodiment of the present invention, based on the principle of vibration isolation layer arrangement due to impedance mismatch, and combined with the material characteristics of foamed lightweight soil and the requirements of engineering practice, the optimal matching coefficient is determined to be 0.2.

[0067] In a preferred embodiment of the present invention, the density ρ of the foamed lightweight soil is... F 28-day compressive strength q u And the thickness H of the vibration isolation layer, based on the equivalent shear modulus G of the soil surrounding the foamed lightweight soil vibration isolation layer. s Depending on the differences, the appropriate selection and construction will be carried out according to the preset correspondence.

[0068] The preset correspondence is determined by the following table:

[0069] .

[0070] As shown in the table above and the accompanying calculation formulas, the optimal density, strength, and vibration isolation layer thickness of the foamed lightweight soil can be directly determined based on the soil shear modulus measured on-site. This provides a data-driven and reliable design process, completely changing the traditional, extensive approach that relies on engineering experience. The same design system can simultaneously meet the different performance requirements of seismic resistance (to cope with accidental strong earthquakes) and vibration isolation (to cope with long-term micro-vibrations). By adjusting material parameters, such as the differentiated configuration of the "seismic layer" and "vibration isolation layer," multi-functional integration can be achieved, making it more widely applicable.

[0071] As a preferred embodiment of the present invention, foamed lightweight soil is prepared using cement and industrial solid waste as cementing materials, employing physical or chemical foaming methods. Utilizing industrial solid waste such as fly ash as raw materials offers significant environmental benefits. Simultaneously, its lightweight nature greatly reduces the additional load on the foundation, lowering structural costs; its excellent vibration isolation performance also extends the service life of pipe corridors and internal pipelines, resulting in outstanding economic benefits throughout its entire life cycle.

[0072] Furthermore, in step S2, the equivalent shear modulus and equivalent density of the surrounding soil are preferably calculated using the parameters of the weak soil layer with the lowest wave impedance, or by using equivalent parameters of multi-layer soil weighted by thickness.

[0073] The present invention further discloses an underground utility tunnel seismic isolation structure based on foamed lightweight soil, comprising an underground utility tunnel and a continuous foamed lightweight soil isolation layer surrounding the underground utility tunnel; the foamed lightweight soil isolation layer fills the area below the bottom plate, the surrounding sides and the top plate of the underground utility tunnel to form a three-dimensional encapsulation structure; the dynamic mechanical properties of the foamed lightweight soil satisfy the wave impedance matching relationship.

[0074] Furthermore, the thickness of the foamed lightweight soil vibration isolation layer is determined and constructed according to the shear modulus of the soil surrounding the underground utility tunnel, based on the preset correspondence table.

[0075] This invention relates to a construction method for an underground utility tunnel seismic isolation structure based on foamed lightweight soil. The method involves on-site casting, pumping fluid foamed lightweight soil slurry into the filling area to allow it to self-level and fill, forming a continuous isolation layer. Specifically, the method includes the following steps:

[0076] S1. Cast the foamed lightweight soil isolation layer at the bottom of the underground pipe gallery;

[0077] S2. After the foamed lightweight soil isolation layer at the bottom of the underground utility tunnel has solidified, place the underground utility tunnel on the solidified foamed lightweight soil isolation layer.

[0078] S3. Cast a foamed lightweight soil isolation layer on all four sides of the underground pipe gallery.

[0079] S4. Pour the foamed lightweight soil isolation layer above the top slab.

[0080] This invention further discloses a foamed lightweight soil for seismic resistance and vibration isolation of underground utility tunnels, the dynamic mechanical properties of which are configured to satisfy the following relationship:

[0081] ,

[0082] In the formula, G F It is the shear modulus of foamed lightweight soil, in MPa;

[0083] ρ F This is the density of foamed lightweight soil, in kg / m³. 3 ;

[0084] G s It is the equivalent shear modulus of the soil surrounding the foamed lightweight soil vibration isolation layer, in MPa;

[0085] ρs It is the equivalent density of the soil surrounding the foamed lightweight soil vibration isolation layer, in kg / m³. 3 ;

[0086] The density ρ of the foamed lightweight soil F Compressive strength q u Based on the shear modulus G of the surrounding soil s The different ranges are adjusted for adaptability in the preset correspondence table as described in claim 1.

[0087] Example 1:

[0088] When applying Formula 1 to verify the dynamic mechanical properties of foamed lightweight soil, the shear modulus of the foamed lightweight soil can be calculated using the elastic modulus and Poisson's ratio, as shown in the following formula:

[0089] Formula 2

[0090] Formula 3

[0091] Formula 4

[0092] Formula 5

[0093] In the formula, G F —Shear modulus of foamed lightweight soil, MPa;

[0094] G s —Shear modulus of the soil surrounding the foamed lightweight soil, MPa;

[0095] E F — Elastic modulus of foamed lightweight soil, MPa;

[0096] υ F —Poisson's ratio of foamed lightweight soil;

[0097] υ s —Poisson's ratio of the soil surrounding the foamed lightweight soil;

[0098] q u —Compressive strength of foamed lightweight soil, MPa;

[0099] —Equivalent elastic modulus of the soil surrounding the foamed lightweight soil, MPa;

[0100] A i —The integral value of the additional stress coefficient of the i-th soil layer along the soil layer thickness, in meters;

[0101] E si—Compression modulus of the i-th soil layer, in MPa, calculated from the soil self-weight pressure at the average depth of the i-th soil layer to the pressure range between the soil self-weight pressure and the additional stress.

[0102] Example 2:

[0103] (1) Project Overview:

[0104] A newly constructed integrated utility tunnel in a city is laterally parallel to an existing subway tunnel, with a net distance D = 12m. The tunnel is buried at a depth of approximately 10 meters, and the geological strata, from top to bottom, are: ① miscellaneous fill (2m thick), ② silty clay (6m thick), ③ silty mud (4m thick). The subway train's main operating frequency is f = 40Hz. Vibration monitoring indicates that without vibration isolation measures, the vibration acceleration level inside the tunnel will exceed the standard, affecting the safe operation of the high-voltage cables and communication lines inside.

[0105] (2) Vibration isolation scheme design

[0106] 1) Determine the design reference soil layer:

[0107] Measured parameters of each soil layer: ② layer G2=35MPa, ρ2=1850kg / m³; ③ layer G3=15MPa, ρ3=1700kg / m³.

[0108] Calculate the wave impedance: ② Layer Z2 ≈ 2.5 × 10 6 kg / (m²·s), ③ layer Z3 ≈ 1.4×10 6 kg / (m²·s).

[0109] Determination: Layer ③ (silty clay) has the lowest wave impedance and is the dominant layer for vibration energy. Based on its parameter G... s / ρ s = 15×10 6 / 1700 ≈ 8824 m² / s² is used as the design benchmark.

[0110] 2) Design the properties of foamed lightweight soil materials:

[0111] According to the core relation G F / ρ F ≤ 0.2 (G s / ρ s ), requiring lightweight foamed soil G F / ρ F ≤ 1765 m² / s².

[0112] According to the preset correspondence table, the density ρ of the foamed lightweight soil is taken as follows: F =1000 kg / m³, Shear modulus G of foamed lightweight soil F =1.0 MPa, GF / ρ F =1.0×10 6 / 1000=1000<1765, which meets the requirements.

[0113] 3) Determine the thickness and arrangement of the vibration isolation layer:

[0114] The vibration source is the subway (f=40Hz), and the net distance D=12m (between 10-30m, in the mid-field zone). According to Table 1, the thickness H of the foamed lightweight soil vibration isolation layer should be 30-80cm. We take H=50cm.

[0115] Arrangement method: On the side wall and under the bottom slab of the utility tunnel near the subway, a continuous vibration isolation layer is constructed by on-site casting to simultaneously isolate horizontal and vertical vibrations.

[0116] (3) Implementation results:

[0117] Vibration monitoring was conducted for one month after construction was completed. Data showed that the vibration acceleration level inside the utility tunnel caused by subway operation decreased by 22 dB, significantly lower than the control standard. Subsequent year-long monitoring indicated that the vibration isolation performance did not deteriorate, and the settlement of the utility tunnel structure was uniform and stable, fully meeting the design expectations.

[0118] Example 3

[0119] (1) Project Overview and Issues:

[0120] In a densely populated urban area, an 8-meter-deep foundation pit was excavated for an underground parking garage. One side of the pit is only 5 meters from a historically protected building housing precision instruments. The pit is supported by pile foundations, but the soil behind the piles requires the demolition of the existing basement, creating a narrow, strip-shaped open area 3 meters deep and 2 meters wide. This area needs backfilling, and during subsequent excavation, support, and structural construction, it is essential to isolate the area from the impact and vibration generated by heavy machinery (such as hydraulic hammers and excavators).

[0121] (2) Vibration isolation scheme design:

[0122] 1) Vibration source analysis and material property design:

[0123] The vibration source is mainly the impact load of hydraulic hammer breaking concrete, which is a broadband vibration. The dominant energy is concentrated in 10-50Hz, and the vibration velocity level is >85dB.

[0124] The building foundation is located on silty clay, and its G s ≈ 45MPa, ρ s ≈ 1900kg / m³, 0.2G s / ρ s =4737 m² / s².

[0125] Due to the confined space, high requirements are placed on the self-weight stress control and early strength performance of the backfill material. A high-strength mix design is adopted, and the shear modulus and density of the foamed lightweight soil are selected based on a pre-defined correspondence table: G F =2.5MPa, ρ F =825 kg / m³, G F / ρ F =2.5×10 6 / 825=3030<4737, which meets the requirements.

[0126] 2) Determine the thickness of the vibration isolation layer:

[0127] This is for impact-type vibration sources, specifically those located in the near-field strong influence zone (D=5m < 10m).

[0128] According to the pre-defined correspondence table, the recommended thickness for impact-type construction activities is no less than 600mm. Considering near-field correction, the design thickness H = 800mm.

[0129] (3) Implementation results:

[0130] The prefabricated vibration isolation wall was assembled within 48 hours and immediately provided soil retention. Vibration monitoring of adjacent historical buildings throughout the foundation pit construction period showed that the peak impact vibration was significantly reduced, and precision instruments inside the buildings remained operational. This solution offers rapid construction, requires no large machinery, causes minimal site disturbance, and can be retained as a permanent vibration isolation structure, achieving a combination of temporary engineering and permanent benefits.

[0131] The purpose of this invention is to address the problems in existing underground utility tunnel seismic and vibration isolation technologies, such as the difficulty in simultaneously achieving seismic and vibration isolation effects, structural strength and durability, crude design methods, and the environmental unfriendliness and high resource consumption of materials. This invention uses cement and industrial solid waste as the main cementing materials for foamed lightweight soil and establishes a quantitative design system based on wave impedance theory, realizing a systematic seismic and vibration isolation method that integrates "precision, efficiency, high strength, durability, and green economy."

[0132] The above examples demonstrate that this method has excellent isolation effects on subway vibration, reducing it by 22dB and construction impact vibration by 70% of the peak value, and its performance remains stable over a long period, proving the maturity and reliability of the technology.

[0133] The significance of this invention lies in providing a specific design and application method for earthquake resistance and vibration isolation of underground utility tunnels using foamed lightweight soil, which greatly improves the ability of underground utility tunnels to control earthquakes using artificial vibration sources under complex working conditions.

[0134] Although the present invention has been illustrated and described with reference to preferred embodiments, those skilled in the art should understand that various changes and modifications can be made to the present invention without departing from the scope defined by the claims.

Claims

1. A seismic isolation method for underground utility tunnels using lightweight foam soil based on wave impedance matching, characterized in that, Includes the following steps: S1: Based on the properties of the soil surrounding the underground utility tunnel to be protected, determine the required performance parameters and pouring thickness of the foamed lightweight soil, and delineate the foamed lightweight soil filling area surrounding the underground utility tunnel. S2: Prepare foamed lightweight soil that meets the performance parameters described in step S1, and pour the foamed lightweight soil into the filling area to form a continuous foamed lightweight soil filling area that covers the bottom slab, the sides, and the top slab of the underground pipe gallery. The performance parameters of the foamed lightweight soil and the surrounding soil of the vibration isolation layer satisfy the following wave impedance matching relationship: ， In the formula, G F It is the shear modulus of foamed lightweight soil, in MPa; ρ F This is the density of foamed lightweight soil, in kg / m³. 3 ; G s It is the equivalent shear modulus of the soil surrounding the foamed lightweight soil vibration isolation layer, in MPa; ρ s It is the equivalent density of the soil surrounding the foamed lightweight soil vibration isolation layer, in kg / m³. 3 ; K is the matching coefficient, and K≤0.

2.

2. The seismic isolation method for underground utility tunnels based on wave impedance matching using lightweight foam soil according to claim 1, characterized in that, The matching coefficient K is 0.

2.

3. The seismic isolation method for underground utility tunnels based on wave impedance matching using lightweight foam soil according to claim 1, characterized in that, The density ρ of the foamed lightweight soil F 28-day compressive strength q u And the thickness H of the vibration isolation layer, based on the equivalent shear modulus G of the soil surrounding the foamed lightweight soil vibration isolation layer. s Depending on the differences, the appropriate selection and construction will be carried out according to the preset correspondence.

4. The seismic isolation method for underground utility tunnels based on wave impedance matching using lightweight foam soil according to claim 3, characterized in that, The preset correspondence is determined by the following table: 。 5. The seismic isolation method for underground utility tunnels based on wave impedance matching using lightweight foam soil as described in claim 1, characterized in that, Foamed lightweight soil is prepared using cement and industrial solid waste as cementing materials and employing physical or chemical foaming methods.

6. The seismic isolation method for underground utility tunnels based on wave impedance matching using lightweight foam soil according to claim 1, characterized in that, In step S2, the equivalent shear modulus and equivalent density of the surrounding soil are preferably calculated using the parameters of the weak soil layer with the lowest wave impedance, or by using equivalent parameters of multi-layer soil weighted by thickness.

7. A seismic isolation structure for underground utility tunnels based on foamed lightweight soil, characterized in that, Includes an underground utility tunnel and a continuous foamed lightweight soil vibration isolation layer surrounding the underground utility tunnel; The foamed lightweight soil vibration isolation layer is filled below the bottom slab, around the sides and above the top slab of the underground pipe gallery, forming a three-dimensional encapsulation structure; The dynamic mechanical properties of the foamed lightweight soil satisfy the wave impedance matching relationship described in claim 1.

8. The seismic isolation structure for underground utility tunnels based on foamed lightweight soil according to claim 7, characterized in that, The thickness of the foamed lightweight soil vibration isolation layer is determined and constructed according to the shear modulus of the soil surrounding the underground utility tunnel, in accordance with the preset correspondence table described in claim 4.

9. The construction method of the underground utility tunnel seismic isolation structure based on foamed lightweight soil as described in claim 7 or 8, characterized in that, The construction method employs on-site casting, pumping fluid, lightweight foamed soil slurry into the filling area to allow it to self-level and fill, forming a continuous vibration isolation layer. Specifically, this includes the following steps: S1. Cast the foamed lightweight soil isolation layer at the bottom of the underground pipe gallery; S2. After the foamed lightweight soil isolation layer at the bottom of the underground utility tunnel has solidified, place the underground utility tunnel on the solidified foamed lightweight soil isolation layer. S3. Cast a foamed lightweight soil isolation layer on all four sides of the underground pipe gallery. S4. Pour the foamed lightweight soil isolation layer above the top slab.

10. A foamed lightweight soil for seismic resistance and vibration isolation of underground utility tunnels, characterized in that, Its dynamic mechanical properties are configured to satisfy the following relationship: ， In the formula, G F It is the shear modulus of foamed lightweight soil, in MPa; ρ F This is the density of foamed lightweight soil, in kg / m³. 3 ; G s It is the equivalent shear modulus of the soil surrounding the foamed lightweight soil vibration isolation layer, in MPa; ρ s It is the equivalent density of the soil surrounding the foamed lightweight soil vibration isolation layer, in kg / m³. 3 ; The density ρ of the foamed lightweight soil F 28-day compressive strength q u Based on the shear modulus G of the soil surrounding the foamed lightweight soil vibration isolation layer s The different ranges are adjusted for adaptability in the preset correspondence table as described in claim 4.

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