An assessment method for determining the risk of a tunnel passing through a building based on the crack width

Abstract

The present invention provides an assessment method for determining the risk of a tunnel passing through a building based on the crack width. On the basis of considering the damage and deterioration of existing buildings, the risk of the tunnel passing through the building is determined by simulating the crack width of the building during the construction process. The implementation principle is as follows: first, the actual parameters are investigated to form a data model, different construction conditions are simulated in the data model, the impacts on the building are statistically analyzed, and the construction plan with the least impact and the lowest cost is obtained through comprehensive data, so as to ensure the progress and cost during the actual construction in the later stage. When the soil disturbance caused by tunnel construction is transmitted to the building, the building will generate cracks with different quantities and degrees. Taking the number and width of the cracks as indicators for tunnel construction risk assessment, the present invention realizes accurate assessment of construction risk on the premise of fully ensuring the safety of existing buildings, and can also ensure reasonable construction costs.

Description

Technical Field

[0001] The present invention relates to the technical field of risk assessment of ground buildings in tunnel construction, and particularly relates to an assessment method for determining the risk of a tunnel passing through a building by crack width. Background Art

[0002] In recent years, the subway tunnels in China have developed rapidly. The environmental conditions faced by the construction of subway tunnels have become increasingly complex and sensitive. Subway tunnels are often laid under busy main roads, with buildings standing on both sides of the road. When constructing subway tunnels, it is necessary to pass through various types of buildings such as dense residential buildings, office buildings, and shopping malls. The types of buildings include masonry structures, reinforced concrete structures, and frame structures, etc. During the construction of subway tunnels, it is inevitable to disturb the surrounding soil mass, and the resulting stratum deformation will further cause the surrounding buildings to deform accordingly, resulting in phenomena such as building inclination and cracking, and even major accidents such as house collapse. Therefore, before the construction of subway tunnels, it is of great significance to determine the deformation that the surrounding buildings can withstand and the risk control indicators for passing through buildings, and to evaluate the safety of tunnel construction to ensure the safety of existing buildings in the vicinity.

[0003] After retrieving the existing technical literature, it is found that there are many studies on the risk control indicators for tunnels passing through buildings at present. The analysis methods mainly fall into two categories: The first category is the overall analysis method, which generally uses numerical methods such as finite elements for calculation and analysis. When simulating the tunnel excavation process, the surrounding soil mass, building foundation, and its superstructure are analyzed as a whole. Its main feature is that the soil and the structure satisfy the deformation coordination condition at the contact surface, and the two are linked through the displacement condition. The responses of the soil and the structure are characterized by the displacement at the contact surface under the action of external forces. The second category is the two-stage analysis method, that is, the influence of tunnel excavation on the building is divided into two stages. The first stage analyzes the soil deformation caused by tunnel excavation, and the second stage applies this deformation to the building to analyze the deformation and internal force changes of the building. However, existing buildings will show damage and deterioration during long-term operation or use, but the current formulation of deformation control standards is still based on the intact state of the building structure and does not consider the damage and deterioration of existing buildings. Therefore, there are certain deficiencies in the determination methods mentioned above. The present invention provides an assessment method for determining the risk of a tunnel passing through a building by crack width to solve the above problems. Summary of the Invention

[0004] The present invention provides an assessment method for determining the risk of a tunnel passing through a building by crack width. Considering the existing damage and deterioration of existing buildings, the risk control indicators for a tunnel passing through a building are evaluated to accurately evaluate the risk control indicators for a tunnel passing through a building.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] An assessment method for determining the risk of a tunnel passing through a building based on the crack width, comprising the following steps:

[0007] S1. Obtain external parameters: Obtain the design parameters A of the tunnel, soil layer parameters B, the positional relationship C between the surrounding buildings and the newly built tunnel, the design parameters D of the buildings, the crack condition F of the buildings, and the elevation H of the building characteristic points;

[0008] S2. Obtain soil parameters: Take samples of the soil for tunnel construction and conduct tests on the samples to obtain the soil parameters along the tunnel construction line;

[0009] S3. Establish a model: Input the parameters obtained in S1 and S2 into the simulation model to establish a data model of the construction tunnel;

[0010] S4. Simulate construction: Conduct simulated construction of the tunnel in the numerical model established in S3, and simulate different construction conditions under different parameters to obtain the external deformation parameters under different conditions; The external deformation parameters include the deformation S 地层 of the stratum, the crack width L of the building after passing through, and the deformation S 新建隧道 of the newly built tunnel;

[0011] S5. Divide the risk level: Determine the allowable crack width L i容许 of the i-th building according to the structural type and damage degree of the building;

[0012] S6. Result comparison: Compare the maximum value L i of the crack width L imax of the i-th building after passing through calculated in S4 with the allowable crack width L i容许 . When L imax = L i容许 , take this condition as the control condition for passing through the i-th building, and find the corresponding S i地层 and S i新建隧道 values under this condition;

[0013] S7. Determine construction parameters: Repeat the operations of S4 and S6 to obtain the control conditions of all buildings and the corresponding S i地层 , S i新建隧道 values. Compare all the S i地层 to obtain the minimum deformation S 地层min of the stratum as the risk control value of the stratum deformation. Compare all the S i新建隧道 to obtain the minimum deformation S 新建隧道min of the newly built tunnel as the risk control value of the newly built tunnel deformation. Take the values of S 地层min and S 新建隧道min as the risk control indicators for tunnel construction.

[0014] Further, in step S3, the external parameters and soil parameters are used as the basic parameters of the simulation model, and a refined finite element model considering the existing structural damage of the existing buildings is established.

[0015] Further, in step S4, the tunnel simulation construction is operated as follows. In the finite element model, the processes of rapid adjustment cyclic excavation, support, and grouting are simulated. After the model operation, the operation results are extracted to obtain the formation deformation S 地层 , the crack width L of the building after crossing, and the deformation S of the newly built tunnel 新建隧道 .

[0016] Further, in step S4, the simulation operations for different construction conditions are as follows. Using the cyclic excavation footage d, the face thrust F 掌子面 and the tail shield grouting pressure F 盾尾 parameters as variables to simulate different construction conditions, and calculate them one by one.

[0017] Further, in step S5, the structural types of the buildings are classified into brick-concrete structure, frame structure, and masonry structure, and the damage degrees are classified into negligible, very slight, slight, moderate, severe, and very severe.

[0018] Further, in step S6, there will be an unequal number of cracks in a single simulation construction under different construction conditions. Select the maximum crack width L of the i-th building imax and compare it with the allowable crack width L i容许 .

[0019] Further, in step S7, the tunnel construction affects different positions and numbers of buildings simultaneously. All the affected buildings are selected and each building is analyzed independently. Different S i地层 and S i新建隧道 values are obtained under the condition of ensuring the safety of each building. These values are classified and compared, and the minimum S 地层min and S 新建隧道min values are selected, which are the risk control indexes for the tunnel to cross the buildings determined by the crack width.

[0020] Further, in step S1, the design parameters A of the tunnel include the shield thrust, the shield tunneling parameters, and the advanced support parameters of the mined tunnel. The soil layer parameters B include the soil layer type and the layer thickness. The position relationship C between the surrounding buildings and the newly built tunnel includes the net distance between the surrounding buildings and the newly built tunnel, the buried depth and the alignment of the newly built tunnel. The design parameters D of the buildings include the building structure type and the foundation type. The crack condition F of the buildings includes the number, alignment, and position of the cracks. The elevation H of the building characteristic points includes at least the elevations of 4 corner points and the midpoints of 4 sides of each building.

[0021] Further, in step S2, the soil parameters include unit weight γ, Poisson's ratio μ, cohesion c, and internal friction angle secant stiffness of triaxial test tangent stiffness of primary consolidation loading test unloading elastic modulus and coefficient of earth pressure at rest K 0nc 。

[0022] Further, in step S3, in the building type, the discrete fracture model is used to simulate the size of the crack width of reinforced concrete

[0023] The beneficial effects of the present invention are as follows:

[0024] When the soil disturbance caused by tunnel construction is transmitted to the building, different numbers and degrees of cracks are generated in the building. Taking the number and width of cracks as indicators to evaluate the tunnel construction risk, it realizes accurate evaluation of construction risk on the premise of fully ensuring the safety of existing buildings, and at the same time can ensure reasonable construction costs; at the same time, considering the existing structural damage of existing buildings when establishing the finite element model ensures the accuracy of the evaluation results Description of the Drawings

[0025] Figure 1 is the flow chart of the present invention;

[0026] Figure 2 is the comparison table of allowable crack widths of buildings in the present invention Detailed Embodiments

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention

[0028] In the description of this patent, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing this patent and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of this patent

[0029] Such as Figure 1As shown in the figure, before the tunnel passes through a building, it is necessary to determine the deformation control index in advance to ensure construction safety. If the control index is set too strictly, it will cause construction difficulties and a significant increase in construction costs. If the control index is set too loosely, it may cause excessive deformation of the existing building, posing a safety hazard. The present invention provides an assessment method for determining the risk of a tunnel passing through a building by the crack width. On the basis of considering the damage deterioration of the existing building, the risk of the tunnel passing through the building is determined by simulating the crack width of the building during the construction process. The implementation principle is to first investigate the actual parameters to form a data model, simulate the construction under different working conditions in the data model, statistically analyze the impact on the building, and comprehensively obtain the construction plan with the least impact and the lowest cost to ensure the progress and cost during the actual construction in the later stage.

[0030] In a specific embodiment of the present invention, a certain subway tunnel is constructed by the shield method. The lower side of the section passes through multiple buildings. The building types in the section include brick-concrete structure, frame structure, and masonry structure. The specific implementation steps are as follows.

[0031] As Figure 1 shown in the figure, S1, obtain external parameters: obtain the design parameters A of the tunnel, soil layer parameters B, the position relationship C between the surrounding buildings and the new tunnel, the design parameters D of the buildings, the crack condition F of the buildings, and the elevation H of the characteristic points of the buildings through means such as investigation, data consultation, and on-site measurement.

[0032] After investigation, it is determined that the design parameters A of the tunnel include the shield tunnel burial depth of 16m, outer diameter of 6.44m, segment thickness of 0.35m, ring width of 1.5m, and elastic modulus of 35MPa. The soil layer parameters B are determined by on-site drilling and sampling: 1-1 miscellaneous fill, burial depth of 0 - 2.4m; 3-1 new loess, burial depth of 2.4 - 7.4m; 3-4 silty clay, burial depth of 7.4 - 16.7m; 4-2 clay, burial depth of 16.7 - 27.3m. The position relationship C between the surrounding buildings and the new tunnel, the design parameters D of the buildings, and the crack condition F of the buildings are respectively: the horizontal net distance between the brick-concrete structure and the tunnel is 6.2m. The brick-concrete structure is a 5-story residence, and there is a vertical crack with a length of 0.52m and a maximum crack width of 0.1mm on the 3rd floor, 2 / F. The frame structure is filled with bricks, the horizontal net distance from the tunnel is 10.7m, and there is an inclined 45° crack with a length of 1.2m and a maximum crack width of 0.1mm. The masonry structure has a horizontal net distance of 7.4m from the tunnel and has an inclined 60° crack with a length of 0.4m and a maximum crack width of 0.1mm. The elevation H of the characteristic points of the buildings includes that the elevations of the 4 corner points and the midpoints of the 4 sides of the brick-concrete structure 1 are the same, the elevations of the frame structure 2 are the same, and the elevations of the masonry structure 3 are the same.

[0033] S2, obtain soil parameters: sample the soil for tunnel construction and test the samples to obtain the soil parameters along the tunnel construction line, including unit weight γ, Poisson's ratio μ, cohesion c, and internal friction angle Secant stiffness of triaxial test Tangent stiffness of primary consolidation loading test Unloading elastic modulus and coefficient of earth pressure at rest K 0nc .

[0034] Referring to the "Standard for Geotechnical Test Methods" (GB / T 50123—2019), the sampling soil was tested by geotechnical test methods, and the parameters of each soil layer were obtained as follows: 1-1 miscellaneous fill, buried depth 0 - 2.4m, unit weight γ 18.5kN / m 3 , Poisson's ratio μ is 0.35, cohesion c is 4.0kPa, internal friction angle is 28°, secant stiffness of triaxial test is 3.9MPa, tangent stiffness of primary consolidation loading test is 16.1MPa, unloading elastic modulus is 1.75MPa, coefficient of earth pressure at rest K 0nc is 0.9; 3-1 new loess, buried depth 2.4 - 7.4m, unit weight γ 18.7kN / m 3 , Poisson's ratio μ is 0.34, cohesion c is 5.0kPa, internal friction angle is 26°, secant stiffness of triaxial test is 2.9MPa, tangent stiffness of primary consolidation loading test is 14.1MPa, unloading elastic modulus is 1.52MPa, coefficient of earth pressure at rest K 0nc is 0.88; 3-4 silty clay, buried depth 7.4 - 16.7m, unit weight γ 18.1kN / m 3 , Poisson's ratio μ is 0.36, cohesion c is 21.0kPa, internal friction angle is 28.2°, secant stiffness of triaxial test is 2.6MPa, tangent stiffness of primary consolidation loading test is 19.1MPa, unloading elastic modulus is 2.32MPa, coefficient of earth pressure at rest K 0nc is 0.91; 4-2 clay, buried depth 16.7 - 27.3m, unit weight 17.7kN / m 3 , cohesion is 15.7kPa, internal friction angle is 29.1°, secant modulus is 2.4MPa, tangent modulus of primary loading is 20.2MPa, unloading modulus is 1.98MPa.

[0035] S3. Establish a model: Input the external parameters and soil parameters as basic parameters into the finite element model established by DIANA software. The model size is 60 m wide, 40 m high, and 100 m long. Model the cracks in the brick-concrete structure, frame structure, and masonry structure, and establish a data model for the construction tunnel. Among them, the reinforced concrete of the building adopts the discrete fracture model, the rock and soil adopt the modified Mohr-Coulomb criterion, the segment adopts the elastic model, and the grouting layer adopts the elastic model to establish the data model of the construction tunnel, preparing for subsequent construction simulation.

[0036] S4. Simulate the construction: Simulate the processes of rapid adjustment cycle excavation, support, and grouting in the finite element model. After model operation, extract the operation results to obtain the deformation S of the stratum under this working condition. 地层 、the crack width L of the building after passing through and the deformation S of the newly built tunnel 新建隧道 ; And simulate the operation under different construction working conditions as follows, taking the cyclic excavation footage d, the face thrust F 掌子面 and the tail shield grouting pressure F 盾尾 parameters as variables to simulate different construction working conditions and calculate them one by one.

[0037] The cyclic excavation footage is set to 0.5 m, 1.0 m, 1.5 m, 2.0 m, 2.5 m, 3.0 m respectively, the face thrust is set to 50 kPa, 75 kPa, 100 kPa, 125 kPa, 150 kPa, 175 kPa, 200 kPa, 225 kPa, 250 kPa, 275 kPa, 300 kPa, 325 kPa, 350 kPa, 375 kPa, 400 kPa, and the tail shield grouting pressure is set to 100 kPa, 125 kPa, 150 kPa, 175 kPa, 200 kPa, 225 kPa, 250 kPa, 275 kPa, 300 kPa, 325 kPa, 350 kPa, 375 kPa, 400 kPa. A total of 6 * 15 * 13 = 1170 working conditions are calculated, and the deformation S of the stratum, 地层 the crack width L of the building after passing through and the deformation S of the newly built tunnel 新建隧道 values are obtained respectively.

[0038] As Figure 2 shown, S5. Divide the risk level: Determine the allowable crack width L of the i-th building according to the structural type and damage degree of the building. i容许 Buildings are divided into brick-concrete structure, frame structure, and masonry structure according to the structural type, and the damage degree is divided into six levels: negligible, very slight, slight, moderate, severe, and very severe. The standards of buildings with different structural types are different under the same damage degree.

[0039] S6, Result Comparison: Compare the maximum value L i of the crack width L of the i-th building after crossing, calculated in S4 imax with the allowable crack width L i容许 . When L imax = L i容许 , take this working condition as the control working condition for crossing the i-th building, and find the corresponding S i地层 and S i新建隧道 values under this working condition.

[0040] S7, Determine Construction Parameters: Repeat the operations of S4 and S6 to obtain the control working conditions of all buildings and the corresponding S i地层 , S i新建隧道 values. Compare all the S i地层 to obtain the minimum formation deformation S 地层min as the risk control value of formation deformation. Compare all the S i新建隧道 to obtain the minimum formation deformation S 新建隧道min as the risk control value of the deformation of the new tunnel. Use the values of S 地层min and S 新建隧道min as the risk control indicators for tunnel construction.

[0041] Taking "very slight" as the judgment criterion for the degree of loss, the allowable value L 1容许 of the crack width of the brick-concrete structure 1 is 1 mm. Compared with the S4 working condition, under the control working condition of the brick-concrete structure 1, S 1地层 is 43 mm, and the S 1新建隧道 value is 38 mm.

[0042] Taking "very slight" as the judgment criterion for the degree of loss, the allowable value L 2容许 of the crack width of the frame structure 2 is 1 mm. Compared with the S4 working condition, under the control working condition of the frame structure 2, S 2地层 is 55 mm, and the S 2新建隧道 value is 47 mm.

[0043] Taking "very slight" as the judgment criterion for the degree of loss, the allowable value L 3容许 of the crack width of the masonry structure 3 is 0.5 mm. Compared with the S4 working condition, under the control working condition of the masonry structure 3, S 3地层 is 38 mm, and the S 3新建隧道 value is 32 mm.

[0044] Under the three control working conditions, while ensuring the safety of each building, classify and compare S 地层 and S 新建隧道 to take the minimum value. The final selection result is that the surface settlement control index S 地层min in this interval is 38 mm, and the crown settlement control index S新建隧道min is 32 mm.

[0045] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention, and any reference signs in the claims should not be regarded as limiting the claims involved.

Claims

1. An assessment method for determining the risk of a tunnel passing through a building based on the crack width, characterized in that, it includes the following steps: S1. Obtain external parameters: Obtain the design parameters A of the tunnel, soil parameters B, the positional relationship C between the surrounding buildings and the new tunnel, the design parameters D of the buildings, the crack condition F of the buildings, and the elevation H of the building characteristic points; S2. Obtain soil parameters: Take samples of the soil for tunnel construction and conduct tests on the samples to obtain the soil parameters along the tunnel construction line; S3. Establish a model: Input the parameters obtained in S1 and S2 into the simulation model to establish a data model of the constructed tunnel; S4. Simulation of construction: Conduct the simulation of tunnel construction in the numerical model established in S3, simulate different construction conditions under different parameters, and obtain the external deformation parameters under different conditions; the external deformation parameters include the deformation S of the stratum 地层 , the crack width L of the building after passing through, and the deformation S of the newly built tunnel 新建隧道 ; S5, Divide the risk level: Determine the allowable crack width L of the i-th building according to the structural type and damage degree of the building i容许 ; S6, Result comparison: Compare the maximum value L i of the crack width L of the i-th building after passing through calculated in S4 imax with the allowable crack width L i容许 . When L imax = L i容许 , take this working condition as the control working condition for passing through the i-th building, and find the corresponding S i地层 and S i新建隧道 values under this working condition; S7. Determine construction parameters: Repeat the operations in S4 and S6 to obtain the control conditions of all buildings and the corresponding S i地层 , S i新建隧道 values. Compare all the S i地层 to obtain the minimum ground deformation S 地层min as the risk control value for ground deformation. Compare all the S i新建隧道 to obtain the minimum ground deformation S 新建隧道min as the risk control value for the deformation of the new tunnel. Use the values of S 地层min and S 新建隧道min as the risk control indicators for tunnel construction; In step S4, the tunnel simulated construction operation is as follows. The processes of rapid adjustment cyclic excavation, support, and grouting are simulated in the finite element model. After the model operation, the operation results are extracted to obtain the formation deformation S under this working condition. 地层 , the crack width L of the building after passing through, and the deformation S of the newly built tunnel 新建隧道； In step S4, the simulation operations for different construction conditions are as follows. Using the cyclic excavation footage d, the face thrust F 掌子面 and the tail shield grouting pressure F 盾尾 parameters as variables to simulate different construction conditions and perform calculations one by one; In step S2, the soil parameters include unit weight γ, Poisson's ratio μ, cohesion c, and internal friction angle Secant stiffness of triaxial test Tangent stiffness of primary consolidation loading test Unloading elastic modulus and coefficient of earth pressure at rest K 0nc .

2. The assessment method for determining the risk of a tunnel passing through a building based on the crack width according to claim 1, characterized in that: In step S3, the external parameters and soil parameters are used as the basic parameters of the simulation model to establish a refined finite element model considering the existing structural damage of the existing buildings.

3. The assessment method for determining the risk of a tunnel passing through a building based on the crack width according to claim 1, characterized in that: In step S5, the structural types of the buildings are classified into brick-concrete structures, frame structures, and masonry structures, and the damage degrees are classified into negligible, very slight, slight, moderate, severe, and very severe.

4. The assessment method for determining the risk of a tunnel passing through a building based on the crack width according to claim 1, characterized in that: In step S6, during a single simulated construction under different construction conditions, there will be different numbers of cracks. Select the maximum crack width L of the i-th building among them. imax Compare it with the allowable crack width L i容许 for comparison.

5. The assessment method for determining the risk of a tunnel passing through a building based on the crack width according to claim 1, characterized in that: In step S7, during tunnel construction, different positions and quantities of buildings are affected simultaneously. All the affected buildings are selected and each building is analyzed independently. Different values of S are obtained on the premise of ensuring the safety of each building. These values are classified and compared, and the minimum values of S and S are selected. These values are the risk control indicators for the tunnel to pass through the buildings determined by the crack width. i地层 and S i新建隧道 values, and these numerical values are classified and compared, and the minimum S 地层min and S 新建隧道min values are taken, which are the risk control indicators for the tunnel to pass through the buildings determined by the crack width.

6. The assessment method for determining the risk of a tunnel passing through a building based on the crack width according to claim 1, characterized in that: Step In S1, the design parameters A of the tunnel include shield thrust, shield tunneling parameters, and advanced support parameters for the mined tunnel, the soil parameters B include soil types and layer thicknesses, the positional relationship C between the surrounding buildings and the new tunnel includes the net distance between the surrounding buildings and the new tunnel, the buried depth and alignment of the new tunnel, the design parameters D of the buildings include building structural types and foundation types, the crack condition F of the buildings includes the number, alignment, and position of the cracks, and the elevation H of the building characteristic points includes at least the elevations of the 4 corners of each building and the midpoints of the 4 sides.

7. The assessment method for determining the risk of a tunnel passing through a building based on the crack width according to claim 3, characterized in that: In step S3, in the building type, a discrete fracture model is used to simulate the size of the crack width of the reinforced concrete.

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