Design method and device for pile-slab subgrade adjacent to existing railway bridge foundation

Abstract

The application relates to the technical field of pile-slab subgrade design, in particular to a pile-slab subgrade design method and device adjacent to a well foundation of an existing railway bridge, which can solve the problem of how to design a pile-slab subgrade adjacent to a well foundation of an existing railway bridge to a certain extent. The method comprises the following steps: determining a plurality of groups of initial structure data of a to-be-constructed pile-slab subgrade, each group of initial structure data being used for constructing a corresponding to-be-constructed highway model; modeling the intersection of each to-be-constructed highway model and the existing railway bridge to obtain a same number of finite element models as the to-be-constructed highway model; updating initial mechanical parameters based on each finite element model to obtain corresponding to-be-selected mechanical parameters; selecting target mechanical parameters from the to-be-selected mechanical parameters, the initial structure data of the finite element model corresponding to the target mechanical parameters being target structure data, and constructing a pile-slab subgrade adjacent to the well foundation of the existing railway bridge according to the target structure data.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pile-slab subgrade design, in particular to a pile-slab subgrade design method and device adjacent to a well foundation of an existing railway bridge. BACKGROUND

[0002] The so-called pile-slab subgrade is generally a subgrade composed of piles and slabs, which is currently composed of two major frame structures of factory-precast slab beams and pipe piles, and is a subgrade form that has emerged in recent years. Compared with the traditional subgrade, the pile-slab subgrade has greater stiffness, smaller settlement, and lower cost, and reduces the width of the slope during construction, thereby greatly improving land utilization.

[0003] When a pile-slab subgrade-based highway is obliquely constructed under an existing railway bridge, if the highway subgrade is close to the pier structure of the existing railway bridge, the vehicle load on the highway subgrade will disturb the foundation structure of the existing railway bridge, increase the foundation load of the existing railway bridge, reduce the bearing redundancy of the foundation of the existing railway bridge, increase the risk of structural deformation and instability of the existing railway bridge, and seriously affect railway operation.

[0004] The foundation of an existing railway bridge includes pile foundations and well foundations, and it is common to construct a pile-slab subgrade adjacent to or below an existing railway bridge with a pile foundation as the bridge foundation. However, there are few construction schemes for constructing a pile-slab subgrade adjacent to an existing railway bridge with a well foundation as the bridge foundation in the prior art. Therefore, it is necessary to study how to design a pile-slab subgrade when constructing a pile-slab subgrade adjacent to a well foundation, in order to minimize the impact of the subsequent pile-slab subgrade construction on the structure of the existing railway bridge. SUMMARY

[0005] The present application provides a pile-slab subgrade design method and device adjacent to a well foundation of an existing railway bridge, which studies how to design a pile-slab subgrade to minimize the impact of the subsequent pile-slab subgrade construction on the structure of the existing railway bridge.

[0006] Embodiments of the present application are implemented as follows:

[0007] The present application provides a pile-slab subgrade design method adjacent to a well foundation of an existing railway bridge, which includes the following steps:

[0008] Determine a plurality of sets of initial structure data of the proposed pile-slab subgrade, each set of initial structure data being used to construct a corresponding proposed highway model based on the proposed pile-slab subgrade;

[0009] modeling the intersection of each proposed highway model and the existing railway bridge, obtaining a same number of finite element models as the proposed highway model, the proposed highway model being obliquely downward through the existing railway bridge to form the intersection;

[0010] updating the initial mechanical parameters based on each finite element model to obtain the selected mechanical parameters corresponding to each finite element model, the initial mechanical parameters being determined based on the existing soil parameters of the existing railway bridge and the proposed soil parameters of the proposed highway model;

[0011] selecting a target mechanical parameter from the selected mechanical parameters, the initial structure data of the finite element model corresponding to the target mechanical parameter being target structure data, and constructing a pile-slab subgrade adjacent to the excavation foundation of the existing railway bridge according to the target structure data.

[0012] In some embodiments, the initial structure data at least includes the pile length, the pile diameter of the proposed pile-slab subgrade, and the distance between the proposed pile-slab subgrade and the excavation foundation of the existing railway bridge.

[0013] In some embodiments, the initial mechanical parameters include the stress and displacement of the piers of the existing railway bridge;

[0014] Determining the initial mechanical parameters of the finite element model based on the existing soil parameters of the existing railway bridge and the proposed soil parameters of the proposed highway model further includes:

[0015] obtaining the existing soil parameters of the existing railway bridge and the proposed soil parameters of the proposed highway model;

[0016] calculating the stress and displacement of the piers of the existing railway bridge based on the existing soil parameters and the proposed soil parameters.

[0017] In some embodiments, the selected mechanical parameters include the stress and displacement of the existing railway bridge during the construction and operation of the proposed highway, and updating the initial mechanical parameters based on each finite element model to obtain the selected mechanical parameters corresponding to each finite element model further includes:

[0018] loading the finite element model with a load, updating the initial mechanical parameters based on each finite element model loaded with a load to obtain the stress and displacement of the existing railway bridge during the operation of the proposed highway;

[0019] updating the initial mechanical parameters based on each finite element model not loaded with a load to obtain the stress and displacement of the existing railway bridge during the construction of the proposed highway.

[0020] In some embodiments, selecting the target mechanical parameter from the candidate mechanical parameters further comprises: selecting the candidate mechanical parameter corresponding to the minimum stress as the target mechanical parameter.

[0021] In some embodiments, the existing railway bridge foundation and the to-be-constructed pile-slab subgrade are linear elastic material models, the soil material model of the finite element model is a Mohr-Coulomb model, and the strength failure criterion of the finite element model is a Mohr-Coulomb strength criterion.

[0022] In some embodiments, the soil of the existing railway bridge includes silt, round gravel, and a foundation pit, the soil parameters of the silt and the round gravel each include an elastic modulus, a cohesive force, an internal friction angle, a Poisson's ratio, and a specific gravity, and the soil parameters of the foundation pit include an elastic modulus, a Poisson's ratio, and a specific gravity.

[0023] In some embodiments, the soil of the to-be-constructed highway includes the pile-slab subgrade, the soil parameters of the pile-slab subgrade include an elastic modulus, a Poisson's ratio, and a specific gravity, and the elastic modulus of the pile-slab subgrade is greater than the elastic modulus of each soil of the existing railway bridge.

[0024] In some embodiments, the method further comprises setting a constraint condition for the finite element model, and the setting of the constraint condition comprises:

[0025] applying a horizontal constraint in two mutually perpendicular directions at the bottom of the finite element model, and applying a normal constraint on both sides of the finite element model.

[0026] The application also provides a pile-slab subgrade design device adjacent to a foundation pit of an existing railway bridge, comprising:

[0027] A determining module is configured to determine a plurality of groups of initial structure data of a to-be-constructed pile-slab subgrade, each group of the initial structure data being used to construct a corresponding to-be-constructed highway model, and the to-be-constructed highway being based on the to-be-constructed pile-slab subgrade.

[0028] A modeling module is configured to model an intersection of each to-be-constructed highway model and an existing railway bridge to obtain a same number of finite element models as the to-be-constructed highway models, and the to-be-constructed highway is obliquely downward through the existing railway bridge to form the intersection.

[0029] A parameter updating module is configured to update an initial mechanical parameter based on each finite element model to obtain a candidate mechanical parameter corresponding to each finite element model, and the initial mechanical parameter is determined based on existing soil parameters of the existing railway bridge and to-be-determined soil parameters of the to-be-constructed highway model.

[0030] The selecting module is configured to select a target mechanical parameter from the to-be-selected mechanical parameters, the initial structure data of the finite element model corresponding to the target mechanical parameter being target structure data, and to construct a pile-slab subgrade adjacent to the existing railway bridge foundation pit according to the target structure data.

[0031] The application has the following beneficial effects: the application provides a method for designing a pile-slab subgrade adjacent to an existing railway bridge foundation pit, calculates the mechanical influence of a to-be-constructed highway on the structure of the existing railway bridge according to each initial structure parameter by using a finite element model, selects a target mechanical parameter from the to-be-selected mechanical parameters, and designs a pile-slab subgrade of the to-be-constructed highway according to the initial structure data of the to-be-constructed highway corresponding to the target mechanical parameter, so that the influence of the pile-slab subgrade on the structure of the existing railway bridge is minimized. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative labor.

[0033] Figure 1 A flowchart of a pile-slab subgrade design method adjacent to an existing railway bridge foundation pit in an embodiment of the application is shown;

[0034] Figure 2 A flowchart of determining initial mechanical parameters in another embodiment of the application is shown;

[0035] Figure 3A A relationship between the distance of the subgrade and the vertical variation of the pier of the existing railway bridge during the construction period and the operation period of the pile-slab subgrade is shown;

[0036] Figure 3B A relationship between the distance of the subgrade and the horizontal displacement of the pier of the existing railway bridge during the construction period and the operation period of the pile-slab subgrade is shown;

[0037] Figure 4 A relationship between different pile lengths and the vertical displacement of the pier and the horizontal displacement in the bridge direction of the pier during the construction of the highway is shown;

[0038] Figure 5 A relationship between different pile lengths and the settlement of the pier and the horizontal displacement in the bridge direction of the pier during the operation of the highway is shown;

[0039] Figure 6A A relationship between different pile diameters and the settlement of the pier and the horizontal displacement in the bridge direction of the pier when the pile length of the pile foundation excavation is 5m is shown;

[0040] Figure 6B The relationship between the pile length of 9m, different pile diameters and the settlement of the pier, and the horizontal displacement along the bridge direction is shown.

[0041] Figure 7A The relationship between the pile length of 5m, different pile diameters and the settlement of the pier, and the horizontal displacement along the bridge direction is shown when in operation.

[0042] Figure 7B The relationship between the pile length of 9m, different pile diameters and the settlement of the pier, and the horizontal displacement along the bridge direction is shown when in operation. DETAILED DESCRIPTION

[0043] In order to make the purpose, implementation and advantages of the present application clearer, the following will combine the drawings in the exemplary embodiments of the present application to clearly and completely describe the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only a part of the embodiments of the present application, but not all the embodiments.

[0044] It should be noted that the brief description of the terms in the present application is only for the convenience of understanding the subsequently described embodiments, and is not intended to limit the embodiments of the present application. Unless otherwise specified, these terms should be understood according to their ordinary and general meanings.

[0045] The terms "first", "second", "third" and the like in the specification and claims of the present application and the above drawings are used to distinguish similar or similar objects or entities, and do not necessarily mean to limit the specific order or sequence, unless otherwise specified. It should be understood that the terms used in this way can be interchanged under appropriate circumstances.

[0046] The terms "include" and "have" and any variations thereof are intended to cover but not exclusive inclusion, for example, a product or device including a series of components does not have to be limited to all the components clearly listed, but can include other components that are not clearly listed or inherent to these products or devices.

[0047] The terms "set", "connected" should be broadly understood, for example, it can be fixedly connected, or detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between the two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0048] Figure 1 An exemplary flowchart of a pile and slab subgrade design method adjacent to a well foundation of an existing railway bridge in an embodiment of the present application is shown as follows: Figure 1 As shown, the pile and slab subgrade design method adjacent to a well foundation of an existing railway bridge comprises the following steps:

[0049] In step 110, a plurality of sets of initial structure data of the pile-slab subgrade to be built are determined, each set of initial structure data being used to construct a corresponding model of the highway to be built based on the pile-slab subgrade to be built;

[0050] According to construction experience and relevant national regulations, when the pile-slab subgrade is built, the influence of the pile-slab subgrade on the existing railway bridge structure needs to be considered, such as the influence of the distance between the pile-slab subgrade to be built and the excavation foundation of the existing railway bridge on the pier column of the existing railway bridge, the influence of the excavation construction of pile foundations with different pile lengths on the displacement of the pier of the existing railway bridge, the influence of the operation of pile-slab subgrades with different pile lengths on the displacement of the pier of the existing railway bridge, the influence of different pile diameters during the excavation construction of pile foundations on the displacement of the pier of the existing railway bridge, and the influence of pile-slab subgrades with different pile diameters on the displacement of the pier of the existing railway bridge.

[0051] Therefore, the initial structure data at least includes the pile length, the pile diameter of the pile-slab subgrade to be built, and the distance between the pile-slab subgrade to be built and the excavation foundation of the existing railway bridge. According to the guidance of the national standard, a plurality of sets of initial structure data are set in order to obtain the best structure data through the method of the present application, and the pile-slab subgrade designed according to the best structure data has the least influence on the existing railway bridge structure.

[0052] In step 120, the intersection between each model of the highway to be built and the existing railway bridge is modeled to obtain a same number of finite element models as the model of the highway to be built, and the highway to be built is obliquely downward through the existing railway bridge to form the intersection.

[0053] The foundation of the highway to be built, i.e., the pile-slab foundation, needs to be built adjacent to the foundation of the existing railway bridge, i.e., the excavation foundation, and the highway to be built is built under the existing railway bridge and obliquely through the railway bridge, therefore, in order to study the influence of the pile-slab subgrade to be built on the structure of the existing railway bridge, the intersection between the two is modeled.

[0054] In the finite element model, the excavation foundation of the existing railway bridge and the pile-slab subgrade to be built are linear elastic material models, the soil material model of the finite element model is a Mohr-Coulomb model, and the strength failure criterion of the finite element model is a Mohr-Coulomb strength criterion.

[0055] In some embodiments, constraint conditions are set for the finite element model, and the constraint conditions include: applying horizontal constraints in two mutually perpendicular directions at the bottom of the finite element model, and applying normal constraints on both sides of the finite element model. The top of the finite element model is a free surface without any constraints.

[0056] In step 130, the initial mechanical parameter is updated based on each finite element model to obtain a to-be-selected mechanical parameter corresponding to each finite element model, and the initial mechanical parameter is determined based on an existing soil parameter of an existing railway bridge and a to-be-determined soil parameter of a to-be-constructed highway model.

[0057] In some embodiments, the initial mechanical parameter includes stress and displacement of a pier of the existing railway bridge.

[0058] Figure 2 A flowchart for determining the initial mechanical parameter in another embodiment of the present application is shown, Figure 2 As shown, the initial mechanical parameter is determined based on the existing soil parameter of the existing railway bridge and the to-be-determined soil parameter of the to-be-constructed highway model, and includes the following steps:

[0059] In step 210, an existing soil parameter of an existing railway bridge and a to-be-determined soil parameter of a to-be-constructed highway model are obtained.

[0060] The existing railway bridge has been constructed, and thus the soil parameter thereof can be directly obtained. The soil of the existing railway bridge includes silt, round gravel and a dug well foundation. The soil parameters of the silt and the round gravel both include an elastic modulus, a cohesive force, an internal friction angle, a Poisson's ratio and a specific gravity, and the soil parameter of the dug well foundation includes an elastic modulus, a Poisson's ratio and a specific gravity.

[0061] The soil parameters of the pile-slab subgrade include an elastic modulus, a Poisson's ratio and a specific gravity, and the soil parameter of the to-be-constructed highway also needs to be set according to construction requirements and relevant standards. It should be noted that the elastic modulus of the pile-slab subgrade is greater than the elastic modulus of each soil in the existing railway bridge.

[0062] In some embodiments, the soil parameters can be set with reference to Table 1. Table 1 exemplarily shows data of the existing soil parameter and the to-be-determined soil parameter.

[0063] Table 1

[0064]

[0065] In step 220, stress and displacement of a pier of the existing railway bridge are calculated based on the existing soil parameter and the to-be-determined soil parameter.

[0066] In step 140, a target mechanical parameter is selected from the to-be-selected mechanical parameter, the initial structure data of the finite element model corresponding to the target mechanical parameter is target structure data, and a pile-slab subgrade is constructed adjacent to the dug well foundation of the existing railway bridge according to the target structure data.

[0067] In some embodiments, the load is loaded to the finite element model, and the initial mechanical parameters are updated based on each finite element model loaded with the load to obtain the stress and displacement of the existing railway bridge respectively subjected to the to-be-constructed highway in operation. The load of the corresponding weight is applied according to the specification of the to-be-constructed highway, and the applied load is used to simulate the vehicle carrying capacity of the highway in operation.

[0068] In some embodiments, the initial mechanical parameters are updated based on each finite element model not loaded with the load to obtain the stress and displacement of the existing railway bridge respectively subjected to the to-be-constructed highway in construction.

[0069] The application calculates the mechanical influence of the to-be-constructed highway constructed according to the initial structure parameters on the existing railway bridge structure by the finite element model, and the mechanical influence is represented by the to-be-selected mechanical parameters. Then, the target mechanical parameters are selected from the to-be-selected mechanical parameters. When the initial structure data of the to-be-constructed highway corresponding to the target mechanical parameters are used to design the pile-slab subgrade of the to-be-constructed highway, the influence of the pile-slab subgrade on the existing railway bridge structure is the smallest.

[0070] The following is the calculation result obtained according to the method of the application.

[0071] (1) Influence of distance between pile foundation of pile-slab subgrade and excavation foundation of existing railway bridge on pier column of existing railway bridge

[0072] (1.1) Influence of distance between pile foundation of pile-slab subgrade and excavation foundation of existing railway bridge on vertical displacement of pier column of existing railway bridge

[0073] For the pile-slab subgrade in operation period, when the subgrade distance L (i.e. the distance between the pile foundation of the pile-slab subgrade and the excavation foundation of the existing railway bridge) is 11 m, the left and right pier columns of the existing railway bridge are both settled by 0.3 mm; when the subgrade distance L is 9 m, the left pier column is settled by 0.2 mm, and the right pier column is settled by 0.7 mm; when the distance L is 7 m, the left pier column is settled by 0.1 mm, and the right pier column is settled by 1.6 mm; when the subgrade distance L is 5 m, the left pier column is settled by 0.1 mm, and the right pier column is settled by 3.3 mm. It can be seen that, with the increase of the distance between the pile foundation of the pile-slab subgrade and the excavation foundation of the existing railway bridge, the settlement of the pier column of the existing railway bridge gradually decreases, and the maximum displacement amount shows a decreasing trend. Figure 3A The relationship between the subgrade distance and the vertical change amount of the pier column of the existing railway bridge during the construction period and the operation period of the pile-slab subgrade is shown.

[0074] (1.2) Influence of distance between pile foundation of pile-slab subgrade and excavation foundation of existing railway bridge on horizontal displacement of pier column of existing railway bridge

[0075] With the reduction of the distance between the pile foundation of the newly-built pile slab subgrade and the existing bridge pier, the horizontal displacement of the bridge pier gradually increases in the bridge longitudinal direction. For the road operation period, when the subgrade distance L is 11 m, the maximum horizontal displacement of the left and right side bridge piers in the bridge longitudinal direction is 1.4 mm; when the subgrade distance L is 9 m, the maximum horizontal displacement of the right side bridge pier in the bridge longitudinal direction is 2.8 mm; when the subgrade distance L is 7 m, the maximum horizontal displacement of the right side bridge pier in the bridge longitudinal direction is 3.8 mm; and when the subgrade distance L is 5 m, the maximum horizontal displacement of the right side bridge pier in the bridge longitudinal direction is 4.4 mm.

[0076] The distance between the pile foundation of the newly-built pile slab subgrade and the excavation foundation of the existing railway bridge has a significant effect on the horizontal displacement of the bridge foundation in the bridge longitudinal direction. The closer the distance between the pile foundation of the newly-built pile slab subgrade and the bridge foundation, the greater the effect on the horizontal displacement of the existing railway bridge pier. Figure 3B The relationship between the subgrade distance and the horizontal displacement of the bridge pier of the existing railway bridge during the construction and operation periods of the pile slab subgrade is shown.

[0077] (2) Effect of different pile lengths of the pile slab subgrade on the displacement of the bridge pier of the existing railway bridge

[0078] (2.1) Effect of different pile lengths of the pile foundation on the displacement of the bridge pier of the existing railway bridge during excavation construction

[0079] With the progress of the excavation process of the pile slab subgrade foundation pit, the surrounding soil tends to slide in the direction of soil unloading, which causes the settlement of the surrounding ground surface. Therefore, the finite element method is used to calculate and analyze the effect of different pile foundation excavation conditions on the existing railway bridge pier.

[0080] The effect of pile foundation excavation on the displacement of the existing bridge pier during piling is analyzed. Considering that the construction is a jump row and jump pile construction method, in order to make the calculation realistic and the results representative, only the displacement change of the bridge pier under the condition of single bored pile excavation under the action of self-weight is considered, the pile diameter is kept constant at 1.2 m, and the displacement change of the bridge pier under the maximum excavation depth is calculated when the pile length is 5 m, 7 m, 9 m, 11 m, 13 m, and 15 m (i.e. initial structure data). Through calculation, the pile foundation excavation bridge pier settlement (i.e. vertical displacement) and the horizontal displacement in the bridge longitudinal direction under different pile lengths are obtained. As shown in Figure 4 The relationship between different pile lengths and the vertical displacement of the bridge pier and the horizontal displacement in the bridge longitudinal direction during highway construction is shown.

[0081] As shown in Figure 4It can be seen that as the pile length increases, the excavation of the pile foundation leads to unloading of the soil around the pier, resulting in settlement and horizontal displacement of the pier. The settlement increases from 1.9 mm (for a 5m pile) to 4.6 mm (for a 15m pile), and the horizontal displacement along the bridge direction increases from 0.1 mm (for a 5m pile) to 3.9 mm (for a 15m pile). When the pile foundation excavation depth is less than 7.5m, the settlement of the existing railway bridge pier caused by the excavation changes with the excavation depth at a rate of 0.05 mm / m, and the horizontal displacement along the bridge direction changes at a rate of 0.25 mm / m. When the excavation depth is greater than 7.5m, the settlement changes with the excavation depth at a rate of 0.38 mm / m, and the horizontal displacement along the bridge direction changes at a rate of 0.42 mm / m.

[0082] It is evident that when the excavation depth exceeds 7.5m, the settlement rate of the existing railway bridge piers increases from 0.05mm / m to 0.38mm / m, while the longitudinal horizontal displacement rate increases from 0.25mm / m to 0.42mm / m. Therefore, during the pile foundation construction process of the slab subgrade, both the settlement and longitudinal horizontal displacement of the existing railway bridge piers caused by excavation are significantly affected by the foundation depth of the railway bridge. When the excavation depth exceeds the burial depth of the existing railway bridge piers, both the settlement and longitudinal horizontal displacement rates caused by excavation increase significantly.

[0083] (2.2) Impact of different pile lengths on the displacement of existing railway bridge piers during operation of roadbed with pile slabs

[0084] To analyze the impact of different pile lengths on the displacement of existing bridge piers, considering the combined effects of self-weight and traffic load, and keeping the pile diameter constant at 1.2m, the displacement changes of the roadbed and bridge piers under different pile lengths of 5m, 7m, 9m, 11m, 13m, and 15m were calculated. The calculations yielded the settlement (vertical displacement) and longitudinal horizontal displacement of the existing railway bridge piers under different pile length conditions. Figure 5 This illustrates the relationship between different pile lengths and pier settlement and longitudinal horizontal displacement during highway operation.

[0085] Depend on Figure 5 It can be seen that the maximum vertical displacement of the bridge pier first increases slightly from 6.1 mm (when the pile length is 5m) to 6.4 mm (when the pile length is 7m) and then decreases to 5.8 mm (when the pile length is 15m); the maximum horizontal displacement of the bridge pier first increases slightly from 2.8 mm (when the pile length is 5m) to 3.0 mm (when the pile length is 9m) and then decreases to 2.4 mm (when the pile length is 15m). When the pile length is less than 7.5m, the settlement and horizontal displacement of the existing railway bridge pier increase with the increase of pile length; when the pile length is greater than 7.5m, the settlement and horizontal displacement of the bridge pier decrease with the increase of pile length.

[0086] (3) The impact of different pile diameters on the settlement of existing railway bridge piers

[0087] (3.1) The influence of different pile diameters on the displacement of the existing railway bridge pier during pile foundation excavation construction

[0088] In order to study the influence of different pile diameters on the displacement of the bridge pier during excavation, finite element analysis and calculation are performed, and the construction method of jump row and jump pile is adopted during construction. In order to make the calculation conform to the actual situation and make the results representative, the displacement change of the bridge pier under the condition of single bored pile excavation under the action of self-weight is considered.

[0089] The displacement change of the bridge pier during excavation when the pile length is 5m and 9m and the pile diameter is 1.0m, 1.2m, 1.5m and 2.0m is calculated. Through calculation, the settlement (vertical displacement) and the horizontal displacement along the bridge of the bridge pier under the condition of different pile diameters during pile foundation excavation are obtained. For example, Figure 6A the relationship between the pile foundation excavation with a pile length of 5m and different pile diameters and the settlement (vertical displacement) and the horizontal displacement along the bridge of the bridge pier is shown, Figure 6B the relationship between the pile foundation excavation with a pile length of 9m and different pile diameters and the settlement (vertical displacement) and the horizontal displacement along the bridge of the bridge pier is shown.

[0090] As can be seen from Figure 6A when the excavation depth is 5m, the excavation depth is less than the bridge foundation depth, and as the pile diameter increases from 1.0m to 2.0m, the settlement of the bridge pier decreases from 2.0mm to 1.8mm, and the horizontal displacement along the bridge decreases from 0.4mm (when the pile diameter is 1.0m) to 0.1mm (when the pile diameter is 2.0m).

[0091] As can be seen from Figure 6B when the excavation depth is 9m, the excavation depth is greater than the bridge foundation depth, and as the excavation width increases from 1.0m to 2.0m, the settlement of the bridge pier is about 2.4mm, and the horizontal displacement along the bridge is about 1.4mm. Excluding the influence of calculation accuracy, it can be seen that the influence of pile diameter on the existing railway bridge pier during pile foundation excavation is very small.

[0092] (3.2) The influence of different pile diameters on the displacement of the existing railway bridge pier during pile foundation excavation construction

[0093] In order to analyze the influence of different pile diameters on the displacement of the existing bridge pier, the displacement change of the pile plate subgrade and the bridge pier when the pile length is 5m and 9m and the pile diameter is 1.0m, 1.2m, 1.5m and 2.0m under the combined action of self-weight and traffic load is calculated, and the settlement (vertical displacement) and the horizontal displacement along the bridge of the bridge pier under the condition of different pile diameters during operation are obtained. For example, Figure 7A the relationship between the pile foundation excavation with a pile length of 5m and different pile diameters and the settlement (vertical displacement) and the horizontal displacement along the bridge of the bridge pier during operation is shown, Figure 7BThe relationship between the pile length of 9m, different pile diameters and the settlement (vertical displacement) of the pier and the horizontal displacement along the bridge direction is shown.

[0094] By Figure 7A It can be seen that when the pile length is 5m, the settlement of the pier is 6.1mm as the pile diameter increases from 1m to 2m, and the horizontal displacement along the bridge direction decreases from 2.9mm (when the pile diameter is 1.0m) to 2.7mm (when the pile diameter is 2.0m).

[0095] By Figure 7B It can be seen that when the pile length is 9m, the settlement of the pier is 6.1mm as the pile diameter increases from 1.0m to 2.0m, and the horizontal displacement of the pier decreases from 3.1mm (when the pile diameter is 1.0m) to 3.0mm (when the pile diameter is 2.0m), and the change is less than 4%. It can be seen that excluding the influence of calculation accuracy, the change of the pile diameter has little effect on the settlement and the horizontal displacement along the bridge direction of the existing railway pier during operation.

[0096] The calculation results show that the underpass highway project breaks the balance of the foundation soil and changes the initial coupling relationship between the existing railway bridge foundation and the surrounding soil. The calculation results show that the distance between the pile-slab subgrade and the pier has a significant effect on the pier, and the closer the distance, the greater the effect, which is similar to the existing research. However, the existing research generally sets the distance between the post-construction pile-slab subgrade and the existing railway bridge pier to be 4-6 times the diameter of the post-construction pile foundation, which is different from the results obtained in the present application. The distance between the post-construction pile-slab subgrade and the existing railway bridge pier is preferably set to be 4-9 times the diameter of the post-construction pile foundation.

[0097] The calculation results also show that the settlement and the horizontal displacement along the bridge direction of the existing railway pier increase with the increase of the maximum excavation depth of the pile foundation, and the settlement and the horizontal displacement along the bridge direction of the existing railway pier gradually decrease with the increase of the pile length. The settlement and the horizontal displacement along the bridge direction of the existing railway pier caused by excavation are significantly affected by the depth of the railway bridge foundation. When the excavation depth exceeds the buried depth of the excavation foundation of the existing railway pier, the change rate of the settlement and the horizontal displacement along the bridge direction caused by excavation significantly increases.

[0098] The calculation results also show that in order to effectively reduce the horizontal and vertical displacement of the pile-slab subgrade on the existing structure, the pile length of the pile-slab subgrade is optimized. By comparing the pile arrangement and other arrangement methods, a ring arrangement scheme is proposed. The pile-slab subgrade with ring arrangement has little effect on stabilizing the soil and reducing the impact on the railway bridge, but by increasing the number of piles and effectively reducing the pile length, the expected purpose is achieved.

[0099] The influence law of the pile-slab subgrade in different structure data on the existing railway bridge structure is simulated by the method, and the pile-slab subgrade is designed based on the influence law, mainly including the selection of the distance between the pile-slab subgrade and the excavation foundation, the pile length of the pile-slab subgrade, the pile diameter of the pile-slab subgrade and the like, so as to reduce the influence on the existing railway bridge pier and ensure the structure and operation safety of the existing railway bridge.

[0100] The embodiment of the application further provides a rigid frame pile-slab subgrade structure. The rigid frame pile-slab subgrade structure is composed of a reinforced concrete cast-in-situ beam, a reinforced concrete bored pile and other auxiliary engineering; the reinforced concrete cast-in-situ beam and the reinforced concrete bored pile are connected by steel bars and poured into an integrated body, and the integrated body is a multi-span continuous rigid frame structure. The rigid frame structure is a cantilever structure in the transverse direction, which effectively avoids the foundation and the like of the existing railway bridge. The rigid frame structure is made of C50 reinforced concrete, the plate thickness is 90 cm, and the top position of the pile foundation is thickened to 1.5 m. The reinforced concrete bored pile at the beam end of the cast-in-situ beam is designed in the form of a single row of three piles, and the row direction is perpendicular to the cast-in-situ beam; the reinforced concrete bored pile at the middle part of the cast-in-situ beam is arranged in the form of seven plum blossom shapes (pile groups), and the pile diameter is less than or equal to 1.2 m, so as to ensure that the minimum distance between the pile foundation of the rigid frame structure and the integral foundation of the existing railway bridge pier is greater than or equal to 4d (4.8 m).

[0101] The embodiment of the application further provides a pile-slab subgrade design device adjacent to an excavation foundation of an existing railway bridge, which comprises:

[0102] A determination module is configured to determine a plurality of groups of initial structure data of a to-be-constructed pile-slab subgrade, each group of initial structure data being used to construct a corresponding to-be-constructed highway model, and the to-be-constructed highway being based on the to-be-constructed pile-slab subgrade;

[0103] A modeling module is configured to model a crossing between each to-be-constructed highway model and the existing railway bridge to obtain a same number of finite element models as the to-be-constructed highway model, and the to-be-constructed highway is obliquely downwardly through the existing railway bridge to form the crossing;

[0104] A parameter updating module is configured to update initial mechanical parameters based on each finite element model to obtain to-be-selected mechanical parameters corresponding to each finite element model, and the initial mechanical parameters are determined based on existing soil parameters of the existing railway bridge and tentative soil parameters of the to-be-constructed highway model;

[0105] A selection module is configured to select target mechanical parameters from the to-be-selected mechanical parameters, the initial structure data of the finite element model corresponding to the target mechanical parameters is target structure data, and the pile-slab subgrade is constructed adjacent to the excavation foundation of the existing railway bridge according to the target structure data.

[0106] The above modules can be embedded in or independent of a processor in a computer device in hardware form, or stored in a memory in the computer device in software form, so as to be called and executed by the processor to perform the operations corresponding to the above modules.

[0107] For the convenience of explanation, the above description has been made in conjunction with specific embodiments. However, the above description in some embodiments is not intended to be exhaustive or to limit the embodiments to the specific form disclosed. Various modifications and variations can be derived from the above teachings. The selection and description of the above embodiments are to better explain the principles and practical applications, so that those skilled in the art can better use the embodiments and various different modified embodiments suitable for specific use considerations.

Claims

1. A method for designing pile-slab subgrade adjacent to the foundation of an existing railway bridge, characterized in that, The method includes the following steps: Multiple sets of initial structural data for the proposed pile-slab roadbed are determined. Each set of initial structural data is used to construct a corresponding model of the proposed highway. The proposed highway is based on the proposed pile-slab roadbed. Modeling is performed at the intersection of each proposed highway model and an existing railway bridge to obtain the same number of finite element models as the proposed highway model. The proposed highway crosses the existing railway bridge at an angle to form the intersection. The initial mechanical parameters are updated based on each finite element model to obtain the candidate mechanical parameters corresponding to each finite element model. The initial mechanical parameters are determined based on the existing soil parameters of the existing railway bridge and the proposed soil parameters of the proposed highway model. Select a target mechanical parameter from the candidate mechanical parameters. The initial structural data of the finite element model corresponding to the target mechanical parameter is the target structural data. Based on the target structural data, excavate the well foundation of the existing railway bridge and construct a pile-slab roadbed.

2. The pile-slab subgrade design method for excavating well foundations adjacent to existing railway bridges as described in claim 1, characterized in that, The initial structural data includes at least the pile length and diameter of the proposed pile-slab roadbed, as well as the distance between the proposed pile-slab roadbed and the excavated foundation of the existing railway bridge.

3. The pile-slab subgrade design method for excavating foundations adjacent to existing railway bridges as described in claim 1, characterized in that, The initial mechanical parameters include the stress and displacement experienced by the existing railway bridge piers; The initial mechanical parameters of the finite element model are determined based on the existing soil parameters of the existing railway bridge and the proposed soil parameters of the proposed highway model, further including: Obtain the existing soil parameters of the existing railway bridge and the proposed soil parameters of the pre-built highway model; The stress and displacement of the existing railway bridge piers are calculated based on the existing soil parameters and the proposed soil parameters.

4. The pile-slab subgrade design method for excavating foundations adjacent to existing railway bridges as described in claim 3, characterized in that, The candidate mechanical parameters include the stress and displacement experienced by the existing railway bridge during the construction and operation of the proposed highway. The initial mechanical parameters are updated based on each finite element model to obtain the candidate mechanical parameters corresponding to each finite element model, further including: Loads are applied to the finite element model, and the initial mechanical parameters are updated based on each loaded finite element model to obtain the stress and displacement of the existing railway bridge when the proposed highway is in operation. The initial mechanical parameters are updated based on the finite element model without load to obtain the stress and displacement of the existing railway bridge during the construction of the proposed highway.

5. The pile-slab subgrade design method for excavating foundations adjacent to existing railway bridges as described in claim 1, characterized in that, Selecting a target mechanical parameter from the candidate mechanical parameters further includes: selecting the candidate mechanical parameter corresponding to the minimum stress value as the target mechanical parameter.

6. The method for designing pile-slab subgrade for excavating foundations adjacent to existing railway bridges as described in claim 1, characterized in that, The existing railway bridge well foundation and the proposed pile-slab subgrade are modeled as linear elastic materials. The soil material model of the finite element model is a Mohr-Coulomb model, and the strength failure criterion of the finite element model is a Mohr-Coulomb strength criterion.

7. The pile-slab subgrade design method for excavating foundations adjacent to existing railway bridges as described in claim 1, characterized in that, The soil of the existing railway bridge includes silt, gravel, and well foundation. The soil parameters of the silt and gravel include elastic modulus, cohesion, internal friction angle, Poisson's ratio, and unit weight. The soil parameters of the well foundation include elastic modulus, Poisson's ratio, and unit weight.

8. The pile-slab subgrade design method for excavating foundations adjacent to existing railway bridges as described in claim 7, characterized in that, The soil of the proposed highway includes the pile-slab subgrade, and the soil parameters of the pile-slab subgrade include elastic modulus, Poisson's ratio and unit weight. The elastic modulus of the pile-slab subgrade is greater than the elastic modulus of each soil in the existing railway bridge.

9. The method for designing pile-slab subgrade for excavating foundations adjacent to existing railway bridges as described in claim 1, characterized in that, It also includes setting constraints on the finite element model, and setting constraints includes: Horizontal constraints are applied in two mutually perpendicular directions at the bottom of the finite element model, and normal constraints are applied on both sides of the finite element model.

10. A design device for pile-slab subgrade adjacent to the foundation of an existing railway bridge, characterized in that, include: The determination module is used to determine multiple sets of initial structural data for the proposed pile-slab roadbed. Each set of initial structural data is used to construct a corresponding model of the proposed highway. The proposed highway is based on the proposed pile-slab roadbed. The modeling module is used to model the intersection of each proposed highway model and the existing railway bridge, resulting in the same number of finite element models as the proposed highway model. The proposed highway crosses the existing railway bridge at an angle to form the intersection. The parameter update module is used to update the initial mechanical parameters based on each finite element model to obtain the candidate mechanical parameters corresponding to each finite element model. The initial mechanical parameters are determined based on the existing soil parameters of the existing railway bridge and the proposed soil parameters of the proposed highway model. The selection module is used to select a target mechanical parameter from the candidate mechanical parameters. The initial structural data of the finite element model corresponding to the target mechanical parameter is the target structural data. Based on the target structural data, a pile-slab roadbed is constructed near the existing railway bridge well foundation.

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