An evaluation method for the influence of residual deformation of goaf on the structural stability of simply supported beam bridge

Abstract

The present application belongs to the technical field of geotechnical engineering research, and particularly relates to a method for evaluating the influence of residual deformation of a goaf on the structural stability of a simply supported beam bridge, which comprises the following steps: constructing a numerical model in a virtual environment in combination with the goaf and the stratum structure of the target simply supported beam bridge; obtaining the mechanical parameters of the broken rock mass and performing sensitivity analysis to generate a sensitivity sequence; equivalent the residual deformation of the goaf to the mechanical parameters of the broken rock mass in the caving zone, determining the equivalent parameters of the residual deformation based on the sensitivity sequence, importing the equivalent parameters into the numerical model to simulate the residual deformation, and outputting the simulation results; establishing a stability evaluation system based on the influence index of the structural stability of the simply supported beam bridge and the residual subsidence, introducing the residual subsidence of the pile foundation of the simply supported beam bridge and the tangential resultant force on the rock-soil contact surface of the pile foundation to evaluate the stability of the target simply supported beam bridge; the evaluation method proposed by the present application can effectively evaluate the influence of the residual deformation of the goaf on the structural stability of the simply supported beam bridge and improve the research efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geotechnical engineering research, and particularly relates to a method for evaluating the influence of residual deformation of a goaf on the structural stability of a simply supported beam bridge. BACKGROUND

[0002] Goafs are widely distributed in China, causing a large amount of land resources to be wasted and posing a safety hazard to engineering construction. Among them, the phenomenon of building a simply supported beam bridge above a goaf is relatively common. As an important component of transportation junction hubs, simply supported beam bridges are indispensable engineering facilities.

[0003] Simply supported beam bridges have unique advantages and applicability in the transportation construction of special regions such as mining areas and industrial areas. First, the construction of a simply supported beam bridge above a goaf helps to make full use of underground space resources. In mining activities, the goaf formed after underground mining is a special geological phenomenon. By building a simply supported beam bridge above it, the goaf can be effectively covered. Second, this bridge structure has high economic efficiency and construction efficiency. The simply supported beam bridge above the goaf uses a simplified structural design, reducing material and labor costs, and has high flexibility and operability during construction. Overall, the construction trend of a simply supported beam bridge above a goaf plays an important role in improving the level of regional transportation and infrastructure, and also provides an innovative solution for engineering construction in special geological environments.

[0004] Currently, based on the residual deformation of the goaf that has existed for a long time and the disturbance influence on the structural stability of the simply supported beam bridge, a method for evaluating the influence of the residual deformation of the goaf on the structural stability of the simply supported beam bridge is proposed. It is necessary to study the disturbance influence law and mechanism of the residual deformation of the goaf on the structural stability of the simply supported beam bridge. SUMMARY

[0005] The purpose of the present application is to provide a method for evaluating the influence of the residual deformation of a goaf on the structural stability of a simply supported beam bridge to solve the problems raised in the background art.

[0006] The present application achieves the above-mentioned purpose through the following technical solutions:

[0007] A method for evaluating the influence of the residual deformation of a goaf on the structural stability of a simply supported beam bridge, the method comprising:

[0008] S1, constructing a numerical model in a virtual environment in combination with the goaf and the stratum structure of the target simply supported beam bridge;

[0009] S2, a caving zone corresponding range is acquired and introduced into the numerical model to complete modeling, broken rock mass mechanical parameters are acquired and sensitivity analysis is carried out, a sensitivity sequence is generated, residual deformation equivalent caving zone broken rock mass mechanical parameters are acquired, the equivalent parameters of residual deformation are determined based on the sensitivity sequence, the equivalent parameters are introduced into the numerical model to carry out residual deformation simulation, and simulation results are outputted;

[0010] S3, a stability evaluation system is established based on the simply supported beam bridge structure stability influence index and the residual subsidence, and the residual subsidence of the simply supported beam bridge pile foundation and the tangential resultant force on the pile foundation rock-soil contact surface are introduced to evaluate the stability of the target simply supported beam bridge.

[0011] As a further optimization scheme of the present application, the construction step of the numerical model is: a multi-physical field network model is established in a virtual environment based on the goaf and stratum structure of the target simply supported beam bridge, and then a numerical model is acquired by introducing the simulation calculation software, which is used for the subsidence calculation and the simply supported beam bridge stability evaluation.

[0012] As a further optimization scheme of the present application, the caving zone range corresponding to the goaf includes the longitudinal and transverse widths of the broken rock mass, the transverse width is the same as the mining width, and the longitudinal height is H :

[0013] ;

[0014] In the formula, H is the longitudinal height of the caving zone, is the cumulative mining thickness.

[0015] As a further optimization scheme of the present application, the broken rock mass mechanical parameters include the internal friction angle, Poisson's ratio, elastic modulus and cohesion, in the process of determining the sensitivity of the parameters based on the OAT method, only the value of the target parameter in the mechanical parameters is changed, and the remaining mechanical parameters are fixed to obtain the influence curve of the above-mentioned mechanical parameters on rock mass deformation, and the sensitivity sequence is determined according to the influence curve.

[0016] As a further optimization scheme of the present application, in step S2, the residual deformation simulation process includes:

[0017] S201, the equivalent parameters of the broken rock mass in the caving zone are replaced in sequence, and the subsidence difference of adjacent two groups of equivalent parameters through the numerical model results is calculated;

[0018] S202, the subsidence difference of the simulation results of adjacent two groups of equivalent parameters is taken as the residual subsidence of the goaf by weakening the equivalent parameters.

[0019] As a further optimization scheme of the present application, in step S3, the simply supported beam bridge structure stability influence index includes residual settlement, residual inclination, ground curvature change and horizontal movement, and the stability evaluation system is established based on the influence index, and the specific is:

[0020] S301, based on the residual settlement, the influence index is quantitatively analyzed, and the quantitative analysis result is characterized as the influence degree of goaf corresponding to each index;

[0021] S302, the numerical relationship between the residual settlement value of the simply supported beam bridge underground pile foundation and the tangential contact force of the pile foundation rock-soil contact surface is established:

[0022] ;

[0023] In the formula H s is the final residual settlement value of the pile foundation, F s is the difference between the final parameter group and the tangential force under the second working condition, F 2 is the tangential force value of the contact surface in the second stage, H 2 is the residual settlement value of the pile foundation corresponding to the second stage;

[0024] S302, the numerical relationship between the residual settlement value of the pile foundation and the tangential force is monitored based on the above relationship, which is used for managers to judge the residual settlement degree of the simply supported beam bridge by monitoring the force.

[0025] The present application has the advantages of:

[0026] 1. The present application provides an evaluation method for the influence of goaf residual deformation on the structure stability of a simply supported beam bridge, which can effectively evaluate the influence of goaf residual deformation on the structure stability of a simply supported beam bridge and improve the research efficiency.

[0027] 2. The evaluation method proposed in the present application verifies that the structure stability of a simply supported beam bridge is closely related to the goaf residual deformation, wherein the stability of the structure is an external reflection of the influence of goaf residual deformation on the destruction of a simply supported beam bridge, and the goaf residual deformation is an internal factor of the stability of a simply supported beam bridge, and the residual settlement of a simply supported beam bridge in the goaf residual deformation stage is a fundamental means to ensure the safety and reliability of the structure stability of a simply supported beam bridge. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a schematic diagram of the evaluation method implementation steps in the present application;

[0029] Figure 2 is a flow chart of the evaluation method in the present application;

[0030] Figure 3is a research area profile in the embodiment of the present application;

[0031] Figure 4 is a grid division and pile numbering diagram in the embodiment of the present application;

[0032] Figure 5 is an equivalent numerical value calculation model schematic diagram in the embodiment of the present application;

[0033] Figure 6 is a parameter change influence curve diagram in the embodiment of the present application;

[0034] Figure 7 is a ground surface, pile and bridge deck residual settlement curve diagram in the embodiment of the present application;

[0035] Figure 8 is a ground surface and pile foundation, bridge deck residual settlement ratio schematic diagram in the embodiment of the present application;

[0036] Figure 9 is a pile foundation inclination principle diagram in the embodiment of the present application;

[0037] Figure 10 is a residual settlement difference schematic diagram of adjacent pile foundations in the embodiment of the present application;

[0038] Figure 11 is a ground surface curvature analysis diagram in the embodiment of the present application;

[0039] Figure 12 is a ground surface monitoring line curvature change schematic diagram in the embodiment of the present application;

[0040] Figure 13 is a final horizontal movement curve schematic diagram of pile foundation in the embodiment of the present application;

[0041] Figure 14 is a ground surface, pile foundation and bridge deck horizontal movement curve schematic diagram in the embodiment of the present application;

[0042] Figure 15 is a tangential resultant force schematic diagram at different stages in the embodiment of the present application;

[0043] Figure 9 in the embodiment of the present application, is a pile foundation cross-sectional load, is a distance of gravity acting on the calculation section; Figure 11 in the embodiment of the present application, is a pile foundation inclination angle. EMBODIMENT

[0044] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content. Example

[0045] like Figures 1-2 As shown in the figure, this embodiment provides a method for evaluating the impact of residual deformation in a goaf on the structural stability of a simply supported beam bridge. The method includes the following steps:

[0046] S1. Construct a numerical model in a virtual environment by combining the goaf and geological structure of the target simply supported beam bridge;

[0047] S2. Obtain the range of the collapse zone in the corresponding goaf and import it into the numerical model to complete the modeling. Obtain the mechanical parameters of the fractured rock mass and perform sensitivity analysis. Generate a sensitivity sequence. Equivalent the mechanical parameters of the fractured rock mass in the collapse zone to the residual deformation of the goaf. Determine the equivalent parameters of the residual deformation based on the sensitivity sequence. Import the equivalent parameters into the numerical model to simulate the residual deformation and output the simulation results.

[0048] S3. Based on the stability impact index of simply supported beam bridge structure and the residual settlement, a stability evaluation system is established. The residual settlement of the pile foundation and the tangential resultant force in the soil-rock contact surface of the simply supported beam bridge are introduced to evaluate the stability of the target simply supported beam bridge.

[0049] As a further preferred option, the steps for constructing the numerical model are as follows: based on the goaf and geological structure of the target simply supported beam bridge, a multiphysics network model is established in a virtual environment, and then imported into the simulation software to obtain the numerical model. The numerical model is used for settlement calculation and stability evaluation of the simply supported beam bridge.

[0050] For example, in step S1, Rhino software is used to create a multiphysics mesh model of the goaf, strata, and simply supported beam bridge. The minimum and maximum sizes of the output mesh cells are 1 and 2 m, respectively. The superstructure of the bridge model is a prestressed concrete simply supported beam, and the abutments are pile columns.

[0051] Importing mesh models from Rhino software into FLAC 3D The initial numerical model obtained by the software can be used for subsequent calculation of residual deformation in the goaf and data extraction of the disturbance effect on simply supported beam bridges.

[0052] When the strength parameters of rock mass decrease, its anti-deformation ability decreases, and the bearing capacity of rock mass will decrease. The main bearing structure of overburden rock in goaf is broken rock mass in broken zone. If the bearing capacity of broken rock mass decreases, even if the load of overburden rock does not change, the cavity and void in goaf will be gradually compacted under the load and residual deformation will be generated. Based on the above analysis, a numerical simulation method is proposed by weakening the mechanical parameters of broken rock mass in goaf to obtain residual deformation.

[0053] As a further preferred solution, in step S2, the caving zone range corresponding to the goaf includes the longitudinal and transverse width of the broken rock mass, the transverse width is the same as the mining width, and the longitudinal height is H :

[0054] ;

[0055] In the formula, H is the longitudinal height of the caving zone, is the cumulative mining thickness.

[0056] The strength variation of the broken rock mass in the equivalent caving zone is used to represent the compaction process of the cavity and void in the overburden rock. The determination of the range of broken rock mass considers both the transverse and longitudinal directions. The height of the broken rock mass is determined by calculating the height of the water flowing fractured zone. The height of the broken rock mass in the caving zone is calculated using the above empirical formula.

[0057] For example, after calculating the height range using the above formula, the reasonableness of modeling is considered, and finally the height of the caving zone is taken as 12m. Since the longitudinal development height of the broken rock mass is only 12m, the transverse range of the outward expansion is small, which has little effect on the residual deformation process. Therefore, the value of the development width of the broken rock mass in the transverse direction is the same as the width of the mining working face in the modeling process.

[0058] As a further preferred solution, the mechanical parameters of the broken rock mass include the internal friction angle, Poisson's ratio, elastic modulus, and cohesion. In the process of determining the sensitivity of the parameters based on the OAT method, only the value of the target parameter in the mechanical parameter is changed, and the remaining mechanical parameters are fixed to obtain the influence curve of the above mechanical parameters on rock mass deformation. The sensitivity sequence is determined according to the influence curve.

[0059] For example, in order to analyze the sensitivity of the above rock mass mechanical parameters to the residual deformation of the goaf site, around the four parameters, each time fix the other three parameters, only change the parameter to be studied, and finally obtain the influence curve of different parameters. It is found that among the four parameters affecting the residual deformation of the goaf, the elastic modulus plays a major role. Therefore, the equivalent numerical simulation process of residual deformation gradually weakens the elastic modulus of the broken rock mass in the caving zone E is realized.

[0060] In the initial stage of the residual deformation of the goaf, the fractured rock mass is separated from the rock stratum, the stress is released, and is randomly accumulated on the floor. The model calculation in the finite element software is based on a continuous medium. After the rock mass in the caving zone is fractured, the stress still exists in the calculation unit. The stress of the unit in the caving zone is first set to zero to simulate the real stress release process of the fractured rock mass. Then the initial modulus of the fractured rock mass in the caving zone is:

[0061] ;

[0062] In the formula, B characterizes the degree of rock fragmentation, is the compressive strength value of the rock, and in the calculation process is 9.96 MPa, B is 1.25, and the calculation result is E 0 is 20.37 MPa, that is, the elastic modulus of the fractured rock mass in the caving zone E is 20.37 MPa, the cohesion is 0, and the internal friction angle is the same as that of the original rock.

[0063] Combined with the probability integral model and the residual deformation prediction parameter, the predicted limit residual subsidence value is about 230 mm. By changing the elastic modulus of the broken rock mass E It can be seen that when E is 5.96 MPa, the surface residual subsidence value reaches 230.6 mm. By gradually weakening the elastic modulus of the broken rock mass in the caving zone from 20.37 MPa to 5.96 MPa, the residual deformation process of the goaf is simulated.

[0064] In the simulation process of the residual deformation of the goaf, the mechanical parameters of the broken rock mass in the caving zone are replaced in turn. The subsidence difference between the simulation results of the adjacent two groups of parameters is the residual subsidence of the goaf between the two groups of parameters. With the gradual weakening of the rock mass parameters, the cumulative residual subsidence value of the goaf gradually increases.

[0065] As a further preferred scheme, in step S2, the residual deformation simulation process comprises:

[0066] S201, the equivalent parameters of the broken rock mass in the caving zone are replaced in turn, and the subsidence difference between the simulation results of the adjacent two groups of equivalent parameters is calculated;

[0067] S202, the residual subsidence of the goaf is obtained by weakening the equivalent parameters and taking the subsidence difference between the simulation results of the adjacent two groups of equivalent parameters as the residual subsidence of the goaf.

[0068] As a further preferred scheme, in step S3, the simply supported beam bridge structure stability influence index includes residual subsidence, residual inclination, surface curvature change and horizontal movement. The stability evaluation system is established based on the influence index and is specifically:

[0069] S301, quantitatively analyze the influence index based on the residual subsidence, and the quantitative analysis result is characterized as the influence degree of the goaf on each index;

[0070] S302, a numerical relationship between the residual subsidence value of the underground pile foundation of the simply supported beam bridge and the tangential contact force on the rock-soil contact surface is established:

[0071]

[0072] In the formula, is the final residual subsidence value of the pile foundation, is the difference between the final parameter group and the tangential contact force under the second working condition, is the tangential contact force value on the contact surface in the second stage, is the residual subsidence value of the pile foundation corresponding to the second stage;

[0073] S302, the numerical relationship between the residual subsidence value of the pile foundation and the tangential contact force is monitored based on the above relationship, which is used by management personnel to judge the residual subsidence degree of the simply supported beam bridge by monitoring the force.

[0074] Corresponding to the above step S4, during the residual deformation of the goaf, the caving zone gradually becomes stable from unstable, the rock mass parameters decrease, and with the passage of time, the parameters tend to be stable. The upper part of the bridge is connected in the form of a hinge, and the stress of the simply supported beam bridge within the bridge abutment support range basically does not change, that is, the shear force and the bending moment do not change. When analyzing whether the simply supported beam bridge structure is stable, only the deformation and displacement of the pile foundation need to be considered, and then the stability of the overall structure of the simply supported beam bridge is discussed.

[0075] With the continuous development of the residual deformation of the goaf, the pile foundation and the surrounding rock of the simply supported beam bridge present a non-synchronous deformation. During the process of gradually weakening the elastic modulus from 20.37MPa to 8MPa, the surface and the residual subsidence of the pile foundation gradually increase, but the residual subsidence speed of the pile foundation is slow. In view of the non-synchronous deformation phenomenon of the surface and the pile foundation, the residual deformation is calculated, and the non-synchronous deformation mechanism is further analyzed.

[0076] The numerical relationship between the residual subsidence of the pile foundation of the simply supported beam bridge and the tangential contact force on the rock-soil contact surface of the pile foundation is established, and the formula is used to verify the numerical relationship between the residual subsidence value of other pile foundations and the tangential contact force, which helps management personnel to judge the residual subsidence degree of the simply supported beam bridge by monitoring the force, or to obtain the tangential contact force on the rock-soil contact surface of the underground pile foundation by monitoring the subsidence value of the bridge.

[0077] The above method is further described in combination with an actual processing routine:

[0078] ​With the actual engineering background of the main line overpass bridge of Songshan Avenue in Xingyang to Xinmi section of Jiaozuo to Pingdingshan highway, the bridge model is established. The upper structure of the bridge is a prestressed concrete simply supported beam, and the abutment is a pile column. The grid model of goaf, stratum and simply supported beam bridge is established by using Rhino software, and the minimum and maximum sizes of the grid element are 1 and 2 m.

[0079] The initial numerical model is obtained by importing the grid model in Rhino software into FLAC3D software. Based on the numerical model, the numerical simulation of residual deformation of goaf can be carried out.

[0080] It is assumed that the gaps in the overburden rock are fully filled and gradually compacted during the residual deformation process of the goaf. The strength variation of the broken rock mass in the equivalent caving zone is used to represent the compaction process of the cavities and gaps in the overburden rock. The determination of the range of broken rock mass is considered from the horizontal and vertical directions. The height of the broken rock mass is determined by calculating the height of the water flowing fractured zone in the vertical direction. Since Shenhe coal mine has been closed, it is difficult to obtain all the geological and mining data in this area. The height of the broken rock mass development in the caving zone is calculated by using the empirical formula, as shown in the following formula, where H is the height of the caving zone, is the cumulative mining thickness. After calculating the height range, the reasonableness of modeling is considered, and finally the height of the caving zone is taken as 12 m.

[0081] (3)

[0082] Since the vertical development height of the broken rock mass is only 12 m, the horizontal range of the outward expansion is small, which has little effect on the residual deformation process. Therefore, the value of the horizontal development width of the broken rock mass in the modeling process is the same as the width of the mining working face.

[0083] The main mechanical parameters affecting rock mass deformation are internal friction angle, Poisson's ratio, elastic modulus and cohesion. In order to analyze the sensitivity of residual deformation of goaf to the above rock mass mechanical parameters, around these four parameters, fix the other three parameters each time, and only change the parameter to be studied. Finally, the influence curve of different parameters is obtained.

[0084] In order to further analyze the sensitivity of internal friction angle, Poisson's ratio, elastic modulus and cohesion, the one-at-a-time (OAT) method (sensitivity analysis method) is used to test the sensitivity of residual subsidence value to the four parameters. It is found that when the elastic modulus decreases from 40 MPa to 10 MPa, the change rate of residual subsidence value reaches 69.5%, and the sensitivity ranking order is elastic modulus > cohesion > internal friction angle > Poisson's ratio. It is shown that among the four parameters affecting the residual deformation of goaf, the main role is the elastic modulus, so the equivalent numerical simulation process of residual deformation in this paper gradually weakens the elastic modulus of the broken rock mass in the caving zone E is realized.

[0085] At the initial stage of residual deformation of goaf, the fractured rock mass is separated from the rock stratum, the stress is released and accumulated on the floor. The model calculation in the finite element software is based on continuous medium. After the rock mass in the caving zone is fractured, the stress still exists in the calculation unit. The stress of the unit in the caving zone is set to zero first to simulate the real stress release process of the fractured rock mass, and then the initial modulus of the fractured rock mass in the caving zone is set:

[0086] (4)

[0087] In the formula, B characterizes the degree of rock fragmentation, is the compressive strength value of rock, and the value of 9.96 MPa is taken in the calculation process of residual deformation of goaf, is 1.25, and the calculation result is B is 20.37 MPa, that is, the elastic modulus of the fractured rock mass in the caving zone is taken as 20.37 MPa, the cohesion E is taken as 0, and the internal friction angle is the same as the original rock.

[0088] Combined with the probability integral model and the residual deformation prediction parameters, the predicted limit residual subsidence value is about 230 mm. By changing the elastic modulus of the broken rock mass E It can be seen that when E is 5.96 MPa, the surface residual subsidence value reaches 230.6 mm. The elastic modulus of the broken rock mass in the caving zone is gradually weakened from 20.37 MPa to 5.96 MPa, and the residual deformation process of the goaf is simulated. The elastic modulus is divided into 8 stages from strong to weak, and the specific parameters of the elastic modulus (E), bulk modulus (K) and shear modulus (G) at different stages are as follows:

[0089] ;

[0090] In the simulation process of residual deformation of goaf, the mechanical parameters of the broken rock mass in the caving zone are replaced in turn, and the subsidence difference between the simulation results of the adjacent two groups of parameters is the residual subsidence of the goaf between the two groups of parameters. With the gradual weakening of the rock mass parameters, the cumulative residual subsidence of the goaf gradually increases.

[0091] ​During the residual deformation of the goaf, the caving zone changes from unstable to gradually stable, and the rock mass parameters decrease. With the passage of time, the parameters tend to be stable. The upper part of the bridge is connected in the form of a hinge. Within the support range of the abutment, the stress of the simply supported beam bridge does not change, that is, the shear force and the bending moment do not change. When analyzing the stability of the simply supported beam bridge structure, only the deformation and displacement of the pile foundation need to be considered, and then the overall structural stability of the simply supported beam bridge is discussed. The four aspects of residual subsidence, residual inclination, surface curvature change and horizontal movement caused by the goaf have the following effects on the structural stability of the simply supported beam bridge:

[0092] (1) Residual subsidence influence

[0093] With the continuous development of the residual deformation of the goaf, the surface residual subsidence presents a nonlinear evolution characteristic of rapid subsidence first and then slow subsidence. The logarithmic function can be used for fitting, and the fitting accuracy is evaluated by the fitting measure . After calculation, , it is shown that the logarithmic function can explain more than 97% of the changes, and the fitting accuracy is high. The residual subsidence law of the pile foundation and the bridge deck is similar. With the continuous weakening of the elastic modulus E , the residual subsidence also presents the evolution characteristic of subsidence first and then tends to be gentle. However, due to the small subsidence speed at the early stage compared with the surface residual subsidence, the linear function can be used for fitting, and the fitting accuracy is more than 0.86, and the linear function fitting effect is good.

[0094] Before the elastic modulus is weakened to 8 MPa, the residual subsidence speed of the pile foundation is fast. When E decreases to 8 MPa, the residual subsidence speed of the pile foundation tends to be gentle, that is, the influence of the residual deformation of the goaf on the pile foundation has tended to be stable. The residual subsidence of the pile foundation can be divided into three categories. The residual subsidence of the middle four pile foundations A2, A3, B2 and B3 is greater than that of the two end pile foundations A1, A4, B1 and B4, but due to the influence of the goaf position, the residual subsidence of the pile foundations A4 and B4 is greater than that of the pile foundations A1 and B1, and the final residual subsidence of the pile foundations A2, A3, B2 and B3 is consistent. There are also three cases of the cooperative deformation relationship between the pile foundation and the bridge deck. Before the elastic modulus is weakened to 8 MPa, the ratio of the residual subsidence of the pile foundations A4 and B4 close to the center of the goaf to the residual subsidence of the bridge deck gradually increases from 1.57 to 1.82. After the elastic modulus is weakened to 8 MPa, the ratio tends to be stable. The residual subsidence of the pile foundations A1 and B1 far from the goaf is close to the residual subsidence of the bridge deck, and they present the same subsidence law. The residual subsidence law of the pile foundations A2, A3, B2 and B3 in the middle of the bridge is consistent, and the ratio of the residual subsidence of the four pile foundations to the residual subsidence of the bridge deck changes between 1.90 and 1.95, and the ratio fluctuates little.

[0095] Compared with the residual settlement of pile foundation and bridge deck, the residual settlement of ground surface is larger in both speed and amplitude, and the elastic modulus of the ground surface is E The ratio of the residual settlement of ground surface to the residual settlement of pile foundation A4, B4 near the center of goaf gradually decreases from 11.85 to 10.16 before the elastic modulus E is weakened to 8MPa, and the ratio tends to be stable after the elastic modulus E is weakened to 8MPa; the ratio of the residual settlement of ground surface to the residual settlement of pile foundation A1, B1 far away from the goaf changes between 17.80-20.75, and the ratio relationship is stable; since the residual settlement of bridge deck is similar to the residual settlement of pile foundation A1, B1, the ratio of the residual settlement of ground surface to the residual settlement of bridge deck also changes in the range; the ratio of the residual settlement of ground surface to the residual settlement of pile foundation A2, A3, B2, B3 in the middle of the bridge gradually decreases from 9.73 to 9.11, and the ratio fluctuation is small.

[0096] (2) Residual inclination influence

[0097] The occurrence of inclination is due to the uneven settlement between structures, and the simply supported beam bridge has the characteristics of small foundation and large stiffness, which is prone to inclination deformation. Under the influence of residual deformation in goaf, there are two reasons for the inclination of simply supported beam bridge: one is that the rock and soil around the pile foundation move, causing the instability of the force on the opposite side of the pile foundation, and the pile foundation is inclined; the other is that the difference in the settlement of adjacent pile foundations leads to the inclination of the bridge.

[0098] Under the influence of residual deformation in goaf, the rock and soil around the simply supported beam bridge are inclined After the angle, the pile foundation is also inclined, and the self-weight added moment on the cross section of the pile , in the formula, is the weight on the cross section of the pile foundation; is the distance of gravity acting on the calculation section; is the inclination angle of the pile foundation, and the inclination calculation of the pile foundation is carried out according to the following formula:

[0099] (5)

[0100] In the formula, L is the length of the bottom surface in the inclined direction, cm; P , Q are the weight value above the pile foundation, the sum of the self-weight and the soil weight, N; M 1 , M 2 represent the moment generated by the environmental load and the gravity load on the center of gravity of the bottom surface, .

[0101] On this basis, the residual settlement difference of 12 groups of adjacent pile foundations is calculated. It is found that with the continuous development of residual deformation, the residual settlement difference of A1-A2 and B1-B2 groups of adjacent pile foundations is the largest, the difference growth rate presents a nonlinear evolution characteristic of first decreasing and then tending to be flat, the residual settlement difference of A3-A4 and B3-B4 groups of adjacent pile foundations is the second, and the settlement rate is small; the residual settlement difference curves of other adjacent pile foundations fluctuate around the y=0 curve, indicating that with the continuous development of residual deformation of the goaf, the residual settlement difference of the corresponding adjacent pile foundation changes little; the pile foundations on both sides of the bridge show that the residual settlement of the middle pile foundation is large, and the residual settlement of the two end pile foundations is small, and the two sides of the bridge segment tilt to the middle segment; the position of the goaf has a significant impact on the residual settlement of the pile foundation, the pile foundation close to the center of the goaf has a significant increase in residual settlement, resulting in an increase in the residual settlement difference of adjacent pile foundations.

[0102] The reason is that the initial stage of the deformation of the surrounding ground surface caused by the residual deformation of the goaf, the influence of the residual deformation on the simply supported beam bridge is small, and the inclination degree is low. With the continuous development of the residual deformation of the goaf, the stress loading and unloading of the pile foundation with small foundation and large stiffness of the simply supported beam bridge are carried out at the same time, and part of the stress loading area is embedded in the surrounding stratum to eliminate part of the inclination difference, so that the inclination of the simply supported beam bridge is smaller than that of the surrounding ground surface.

[0103] (3) Ground curvature influence

[0104] Curvature refers to the ratio of the inclination difference of two adjacent sections to the horizontal distance of the two section points, which is used to measure the bending degree of the ground surface. An observation line of 120 m is arranged along the bridge direction around the ground surface and the bridge deck of the simply supported beam bridge (120 m is close to one end of the goaf), and the data is extracted for curvature calculation.

[0105] Assume the ground Three points are affected by the residual deformation of the goaf, The inclination of point , the inclination of point , and the inclination of point

[0106] (6)

[0107] (7)

[0108] In the formula, are the settlement differences between point and point; are the horizontal distances between point and point; are the curvatures of The tilt angle between the points is much smaller than the horizontal distance between the two points, Therefore, there are The tilt angle between the points is much smaller than the horizontal distance between the two points,

[0109] (8)

[0110] The surface and bridge deck curvature curves both have three peaks and two valleys. The two valleys of the surface curvature appear at 40 m and 80 m of the monitoring line, respectively, and the curvature values suddenly decrease at 0 m, 40 m, 80 m, and 120 m, which correspond to the positions of the pile foundation, indicating that the existence of the pile foundation has a significant effect on the surface curvature deformation. The residual curvature values of the surface and the bridge deck are both positive, i.e., the surface and the pile foundation monitoring line are both in the positive curvature influence area, and the surface curvature deformation is greater than the bridge deck curvature deformation, but the curvature limit values of both appear at 90 m of the monitoring line.

[0111] The surface curvature on the 0-40 m, 40-80 m, and 80-120 m sections of the surface monitoring line all show a non-linear deformation characteristic of first increasing and then slowing down. The corresponding curvature limit values of each section are significantly affected by the goaf, and the closer to the goaf, the greater the corresponding curvature limit value. Compared with the surface curvature deformation, the bridge deck curvature deformation value is small, and the limit value is only 0.003 m -1 The appearance positions of the valleys on the bridge deck curvature curve are the same as those of the surface, indicating that the bridge deck curvature deformation is also affected by the position of the pile foundation, and the closer to the corresponding position of the pile foundation, the smaller the curvature value, i.e., the existence of the pile foundation can suppress the bridge deck curvature deformation. Under the influence of the goaf position and the pile foundation, the surface and bridge deck curvature deformations are small, and the impact on the stability of the simply supported beam bridge structure is limited.

[0112] (4) Horizontal deformation influence

[0113] With the continuous development of the residual deformation of the goaf, the surface produces uneven subsidence and also exists horizontal deformation. The horizontal deformation of the surface leads to changes in the vertical direction load of the bridge, which in turn causes the bridge to have relative horizontal displacement, affecting the safety and stability of the simply supported beam bridge structure. The horizontal deformation of the simply supported beam bridge can be divided into horizontal deformation along the bridge direction and horizontal deformation perpendicular to the bridge direction.

[0114] Extracting the horizontal deformation values of the bridge pile foundation, it is found that with the increase of the elastic modulus E ​​​​The surface in the direction along the bridge and the direction perpendicular to the bridge presents the nonlinear evolution characteristics of increasing nonlinearity, and the growth rate gradually slows down; compared with the residual horizontal deformation of the surface, the residual horizontal deformation of the pile foundation is smaller, and the residual horizontal deformation of the bridge deck is the smallest;

[0115] In the process of gradually weakening the elastic modulus from 20.37 MPa to 6 MPa, the residual horizontal deformation of the surface gradually increases, and the growth rate gradually slows down. The residual horizontal deformation of the pile foundations A1, B1, A4, and B4 is smaller than that of the surface, but the growth trend is consistent with that of the surface. The horizontal deformation values of the pile foundations A2, B2, A3, and B3 in the direction along the bridge are close to 0, and the horizontal deformation in the direction perpendicular to the bridge presents a gradually increasing trend. The residual horizontal deformation of the bridge deck in the two directions is small. When the elastic modulus is between 8 MPa and 6 MPa, the residual horizontal movement curve tends to be flat, indicating that the horizontal deformation of the surface, the pile foundation, and the bridge deck has stabilized.

[0116] In the direction along the bridge, the pile foundations on both sides of the bridge present a symmetrical deformation trend. The horizontal deformation values of A4 and B4 are the largest, the horizontal deformation values of the pile foundations A2, A3, B2, and B3 located in the middle of the bridge are close to 0, and the horizontal deformation values of the pile foundations A1 and B1 at the other end are between the two. That is, the horizontal deformation degree in the direction along the bridge is small in the middle of the bridge, and the influence of the pile foundations A4 and B4 on the side of the bridge is large, indicating that the horizontal deformation in the direction along the bridge is related to the position of the goaf. The closer the bridge structure is to the center of the goaf, the more likely it is to deform horizontally. In the direction perpendicular to the bridge, the horizontal deformation values of the pile foundations on both sides of the bridge are consistent, and the deformation directions are different, indicating that the horizontal deformation in the direction perpendicular to the bridge causes the bridge to be affected by stretching, affecting the structural stability of the simple-supported beam bridge.

[0117] With the continuous development of the residual deformation of the goaf, the development of the surrounding plastic zone eventually reaches fullness, that is, the inflection point offset distance The length of the boundary active cavity region is 0; the calculation length is the mining length minus the inflection point offset distance Due to the cantilever effect, the equivalent mining thickness in the subsequent calculation of residual deformation is considered as the mining thickness The limit maximum subsidence value of the surface, including the residual deformation of the goaf, will not exceed the mining thickness The equivalent mining thickness The calculation is as follows:

[0118] (9)

[0119] In the formula, The subsidence coefficient of the end of the sinking is obtained from the measured results before the residual deformation of the goaf. The Shenghe Coal Mine has been closed, and it is difficult to obtain all the mining data in this area. Therefore, according to the surface movement formula after stopping mining, the subsidence of T in the activation of the goaf is calculated to obtain the coefficient.

[0120] (10)

[0121] In the formula: is the surface subsidence value of unit mining; is the main influence radius, and the horizontal coordinate of the unit is , the horizontal coordinate of any point on the surface is , and the subsidence value of the point caused by the mining thickness is , then the residual subsidence value is:

[0122] (11)

[0123] The coal seam inclination needs to be considered in the residual deformation stage of the goaf , and the above formula becomes:

[0124] (12)

[0125] Combining the function , and the coal seam inclination is 0, the residual deformation calculation formula of the goaf is obtained

[0126] (13)

[0127] According to the calculation formula, the residual subsidence of the center point of the surface where the simply supported beam bridge is located is , and the residual subsidence of the corresponding point in the model is 230.4 mm. In the same way, the residual subsidence of several surface points is calculated, and it is found that the result of the numerical simulation method is larger than the calculated value of the residual subsidence, and the increase ratio is about 5%. This shows that the construction of the simply supported beam bridge on the goaf will intensify the residual subsidence of the construction site and further affect the structural stability of the bridge itself.

[0128] The numerical relationship between the residual subsidence value of the underground pile foundation of the simply supported beam bridge and the tangential contact force of the pile foundation-rock contact surface is established:

[0129] (14)

[0130] In combination with the above-mentioned implementation procedures, it is found by the evaluation method according to the present application that the structural stability of the simply supported beam bridge is closely related to the residual deformation of the goaf, wherein whether the structure is stable is an external reflection of the influence of the residual deformation of the goaf on the damage of the simply supported beam bridge, the residual deformation of the goaf is an internal factor of whether the structure of the simply supported beam bridge is stable, and the residual settlement of the simply supported beam bridge in the stage of controlling the residual deformation of the goaf is a fundamental means to ensure the safety and reliability of the structural stability of the bridge.

[0131] The above examples are only used to illustrate the technical solutions of the present application, but not limit the same; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not drive the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for evaluating the impact of residual deformation in a goaf on the structural stability of a simply supported beam bridge, characterized in that the method... include: S1. Construct a numerical model in a virtual environment by combining the goaf and geological structure of the target simply supported beam bridge; S2. Obtain the range of the collapse zone in the corresponding goaf and import it into the numerical model to complete the modeling. Obtain the mechanical parameters of the fractured rock mass and perform sensitivity analysis to generate a sensitivity sequence. Equivalently convert the residual deformation of the goaf into the mechanical parameters of the fractured rock mass in the collapse zone. Determine the equivalent parameters of the residual deformation based on the sensitivity sequence. Import the equivalent parameters into the numerical model to simulate the residual deformation and output the simulation results. The mechanical parameters of the fractured rock mass include internal friction angle, Poisson's ratio, elastic modulus and cohesion. In the process of determining the sensitivity of the parameters based on the OAT method, only the target parameter value of the mechanical parameters is changed, and the remaining mechanical parameters are fixed to obtain the influence curve of the above-mentioned mechanical parameters on the deformation of the rock mass. The sensitivity sequence is determined according to the influence curve. In step S2, the residual deformation simulation process includes: S201. Replace the equivalent parameters of the fractured rock mass in the collapse zone in sequence, and calculate the subsidence difference between two adjacent sets of equivalent parameters as determined by the numerical model. S202. By weakening the equivalent parameters, the subsidence difference between the simulation results of two adjacent sets of equivalent parameters is taken as the residual subsidence of the goaf. S3. Based on the structural stability impact index of simply supported beam bridge and the residual settlement, a stability evaluation system is established. The residual settlement of the pile foundation and the tangential resultant force in the soil-rock contact surface of the pile foundation are introduced to evaluate the stability of the target simply supported beam bridge.

2. The evaluation method for the influence of residual deformation in a goaf on the structural stability of a simply supported beam bridge according to claim 1, characterized in that: The steps for constructing the numerical model are as follows: a multiphysics network model is established in a virtual environment based on the goaf and geological structure of the target simply supported beam bridge, and then imported into the simulation software to obtain the numerical model. The numerical model is used for the calculation of the settlement and the stability evaluation of the simply supported beam bridge.

3. The evaluation method for the influence of residual deformation in a goaf on the structural stability of a simply supported beam bridge according to claim 1, characterized in that: The collapse zone corresponding to the goaf includes the longitudinal and transverse widths of the fractured rock mass, with the transverse width being the same as the mining width and the longitudinal height being... H : ； In the formula, H The longitudinal height of the landslide zone. For cumulative thickness.

4. The evaluation method for the influence of residual deformation in a goaf on the structural stability of a simply supported beam bridge according to claim 1, characterized in that: In step S3, the stability indices of the simply supported beam bridge include residual settlement, residual tilt, changes in surface curvature, and horizontal movement. The stability evaluation system is established based on these indices as follows: S301. Based on the residual subsidence, perform quantitative analysis on the impact indicators, and characterize the quantitative analysis results as the degree of influence of each indicator corresponding to the goaf. S302. Establish a numerical relationship between the residual settlement value of the underground pile foundation of a simply supported beam bridge and the monitored value of the tangential resultant force at the soil-rock interface of the pile foundation: ； In the formula H s This represents the final residual settlement value of the pile foundation. F s This is the difference between the final resultant tangential force under the parameter set and that under the second working condition. F 2 represents the resultant tangential force value within the contact surface during the second stage. H 2 represents the residual settlement value of the pile foundation corresponding to the second stage; S302. Based on the above relationship, monitor the numerical relationship between the residual settlement value and the tangential resultant force of the pile foundation, so that managers can judge the degree of residual settlement of the simply supported beam bridge by monitoring the force.

Images