Method for simulating floating of subway track bed in karst area based on finite element analysis software

Abstract

The invention discloses a karst area subway track bed floating simulation method based on finite element analysis software, which adopts the finite element analysis simulation software and comprises the following steps of: 1, simplifying a steel rail of a to-be-simulated karst area subway track bed in a pressed state into a beam unit, simplifying a track bed main body and a lower backfill layer into entity units, and simplifying the beam unit into a beam unit; constraint of a fastener system on a steel rail is simplified into a point supporting linear spring, supporting is simplified into a nonlinear rod unit which can only bear pressure, and a backfill layer of a subway ballast bed in a karst area to be simulated is simplified into a rod unit; 2, setting boundary conditions; 3, modeling the simplified subway track bed of the karst area to be simulated; in modeling, buoyancy is fully distributed under one single roadbed slab needing to be calculated in the erected roadbed main body, and the influence of buoyancy under other single roadbed slabs is neglected; a slab is added to each of the two sides of a single roadbed slab needing to be calculated so as to reduce the influence of boundary conditions on a calculation area.

Description

Technical Field

[0001] The invention relates to the technical field of computer-aided design, and in particular to a method for simulating the floating of a subway roadbed in a karst area based on finite element analysis software. Background Art

[0002] The water level of pressurized water in karst areas is high, the water volume is large, and most of it is stored in rock cracks, which has certain particularities. Groundwater flows into the space between the roadbed and the invert arch filling surface through other weak links such as the invert arch construction joints, causing the roadbed to rise and float from time to time.

[0003] In rail transit, the track structure primarily guides trains and provides load-bearing capacity. The quality of its structural condition directly impacts driving safety and comfort. A bulging trackbed significantly impairs track smoothness, forcing trains to operate at limited speeds. Furthermore, the track can become detached from the concrete of the underlying foundation structure, creating large cracks and potentially creating safety hazards.

[0004] Currently, understanding of trackbed uplift caused by water inrush in karst areas is still at the qualitative analysis stage, lacking quantitative computational analysis and theoretical support. Current track designs generally do not consider the effects of buoyancy. Trackbed uplift is addressed through post-initiative rectification, which often results in speed restrictions or even suspension of train operations. Remediation solutions typically include grouting reinforcement, anchor bolting, and water release to reduce pressure. However, these anchor bolts must penetrate the trackbed and be implanted into the tunnel lining, inevitably causing structural damage.

[0005] Therefore, how to achieve accurate and efficient analysis of the problem of subway roadbed floating in karst areas has become a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0006] In view of the above-mentioned defects of the prior art, the present invention provides a method for simulating the floating of subway roadbed in karst areas based on finite element analysis software, the purpose of which is to achieve the following.

[0007] To achieve the above object, the present invention discloses a method for simulating the floating of subway roadbed in karst areas based on finite element analysis software, which uses finite element analysis simulation software and includes the following steps:

[0008] Step 1: Simplify the rails of the subway roadbed in the karst area to be simulated under compression into beam elements.

[0009] The main body of the subway roadbed and the lower backfill layer of the karst area subway roadbed to be simulated are simplified into solid units.

[0010] The constraint of the fastener system on the rails of the subway roadbed in the simulated karst area is simplified to a point-supported linear spring.

[0011] The support of the subway roadbed in the karst area to be simulated is simplified into a nonlinear rod unit that can only bear compression.

[0012] Simplifying the backfill layer of the subway roadbed in the karst area to be simulated into rod units;

[0013] The elastic modulus of the nonlinear rod element capable of bearing only compression is the same as that of C35 concrete;

[0014] The cross section of the beam unit is the same as that of a 60kg / m rail, and the material parameters are the same as those of steel;

[0015] The elastic modulus of the solid unit is the same as that of C35 concrete;

[0016] The spring stiffness parameters of the point-supported linear spring are selected as the vertical and lateral static stiffness of the node of the fastener respectively;

[0017] Step 2: Set boundary conditions;

[0018] Step 3: Modeling the simplified subway roadbed in the karst area to be simulated;

[0019] In the modeling, the buoyancy under a single ballast plate to be calculated in the ballast body is fully distributed, and the influence of the buoyancy under other single ballast plates is ignored;

[0020] Then, a plate is added on each side of the single track bed plate to be calculated to reduce the influence of boundary conditions on the calculation area;

[0021] The buoyancy under the slab at this time is obtained according to the slab uplift limit of the single slab calculated as needed.

[0022] Preferably, the rails are 60kg / m rails with a gauge of 1435mm; the roadbed body and the lower backfill layer are both made of C35 concrete; the dimensions of each single roadbed plate of the roadbed body are 12.5m×2.4m×0.33m; and the fastener spacing of the fastener system is 595mm.

[0023] Preferably, step 2 is as follows:

[0024] Step 2.1, apply fixed constraints at both ends of the beam element;

[0025] Step 2.2: For the solid unit corresponding to the roadbed body, the beam slides horizontally, and the upward displacement is not constrained;

[0026] Step 2.3: Apply fixed constraints to the rod element.

[0027] Preferably, the buoyancy of the roadbed is prevented by controlling the buoyancy within the lower range of the roadbed body or the connection between each single roadbed plate and the lower structure, thereby preventing the buoyancy under the plate of the single roadbed plate from being greater than the weight of the roadbed, that is, preventing the elevation from exceeding the limit.

[0028] Beneficial effects of the present invention:

[0029] The present invention elevates the understanding of roadbed uplift caused by environmental water inrush in karst areas from qualitative analysis to quantitative calculation analysis, and provides theoretical support for numerical simulation.

[0030] The present invention modifies and improves the traditional simulation model of the track structure, overcoming the defect that the traditional model only focuses on the track structure being in a compressed state and simplifies the fastener system and the lower structure supporting layer into a linear spring-damping unit, whose elastic moduli are respectively the elastic modulus of the fastener system (mainly considering the elastic bars and elastic pads) and the elastic modulus of the lower structure concrete, which cannot meet the requirements of karst areas.

[0031] The present invention solves the problem that in a karst area with water gushing, the track structure is subjected to upward buoyancy, and the steel rails in the uplifted area will pull the adjacent fasteners so that the lower structure no longer has any effect on the track structure, resulting in the linear spring-damping unit being no longer applicable.

[0032] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The finite element model of a single track bed slab required to be calculated in one embodiment of the present invention is shown.

[0034] Figure 2 The numerical model and buoyancy distribution of a single track slab required to be calculated in one embodiment of the present invention are shown.

[0035] Figure 3 The figure shows a vertical deformation cloud diagram of a single track bed slab that needs to be calculated in one embodiment of the present invention. DETAILED DESCRIPTION

[0036] Example

[0037] A simulation method for subway roadbed floating in karst areas based on finite element analysis software includes the following steps:

[0038] Step 1: Simplify the rails of the subway roadbed in the karst area to be simulated under compression into beam elements.

[0039] The main body of the subway roadbed and the lower backfill layer of the karst area to be simulated are simplified into solid units.

[0040] The constraint of the fastener system on the rails of the subway roadbed in the simulated karst area is simplified to a point-supported linear spring.

[0041] The support of the subway roadbed in the karst area to be simulated is simplified to a nonlinear rod element that can only bear compression.

[0042] The backfill layer of the subway roadbed in the karst area to be simulated is simplified into rod elements;

[0043] Among them, the elastic modulus of the nonlinear rod element that can only bear compression is the same as that of C35 concrete;

[0044] The cross section of the beam unit is the same as that of a 60kg / m rail, and the material parameters are the same as those of steel;

[0045] The elastic modulus of the solid unit is the same as that of C35 concrete;

[0046] The spring stiffness parameters of the point-supported linear spring are selected as the vertical and lateral static stiffness of the node of the fastener respectively;

[0047] Step 2: Set boundary conditions;

[0048] Step 3: Model the simplified subway trackbed in the karst area to be simulated;

[0049] like Figure 1 As shown in the figure, in the modeling, the buoyancy under a single slab that needs to be calculated in the ballast bed is fully distributed, and the influence of the buoyancy under other slabs is ignored.

[0050] In order to obtain a pressure limit with certain guiding significance, it is assumed that there is buoyancy under one plate, and since the connection between the plates is weak, the influence of the buoyancy under other plates can be ignored.

[0051] Then, a plate is added on each side of the single track slab to be calculated to reduce the influence of boundary conditions on the calculation area;

[0052] The buoyancy under the slab at this time is obtained based on the roadbed uplift limit of the single roadbed slab that needs to be calculated.

[0053] like Figure 2 As shown in the figure, during modeling, a plate is added on each side of the plate to be calculated to reduce the impact of boundary conditions on the calculation area. The numerical model and buoyancy distribution are shown in the figure below.

[0054] like Figure 3 It shows that the roadbed uplift limit is controlled at 2mm, and the buoyancy under the plate is F = 346.9kN.

[0055] In some embodiments, the rails are 60kg / m rails with a gauge of 1435mm; the roadbed body and the lower backfill layer are both C35 concrete; the dimensions of each single roadbed plate of the roadbed body are 12.5m×2.4m×0.33m; and the fastener spacing of the fastener system is 595mm.

[0056] In certain embodiments, step 2 is as follows:

[0057] Step 2.1: Apply fixed constraints at both ends of the beam element.

[0058] Since the displacement at both ends of the rail is zero, fixed constraints are used.

[0059] Step 2.2: For the solid elements corresponding to the trackbed, the beam slides horizontally, and the upward displacement is not constrained;

[0060] The expansion anchor bolts at the bottom of the track bed restrain horizontal sliding, and since the anti-floating ability after the bolts are loosened can be ignored, the upward displacement is not restrained.

[0061] Step 2.3: Apply fixed constraints to the bar element.

[0062] The bottom of the rod element used to simulate the backfill layer is constrained by the tunnel structure, so a fixed constraint is adopted.

[0063] In some embodiments, the buoyancy of the roadbed is prevented by controlling the buoyancy within the lower range of the roadbed body or the connection between each single roadbed plate and the lower structure, thereby preventing the buoyancy under the plate of a single roadbed plate from being greater than the weight of the roadbed, that is, preventing the elevation from exceeding the limit.

[0064] In practical applications, the weight of a general track system within a range of 12.5m is approximately 34 tons, or 340kN, which is very close to the calculated limit of the buoyancy F under the slab (346.9kN). It can be seen that when the buoyancy under the slab is slightly greater than the weight of the trackbed, an elevation over-limit will occur. Therefore, certain measures need to be taken in the design stage to control the buoyancy under the trackbed slab or strengthen the connection between the trackbed and the substructure to prevent the trackbed from floating.

[0065] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for simulating the floating of subway roadbed in karst areas based on finite element analysis software; the method is characterized by: Finite element analysis simulation software is used, including the following steps: Step 1: Simplify the rails of the subway roadbed in the karst area to be simulated under compression into beam elements. The main body of the subway roadbed and the lower backfill layer of the karst area subway roadbed to be simulated are simplified into solid units. The constraint of the fastener system on the rails of the subway roadbed in the simulated karst area is simplified to a point-supported linear spring. The support of the subway roadbed in the karst area to be simulated is simplified into a nonlinear rod unit that can only bear compression. Simplifying the backfill layer of the subway roadbed in the karst area to be simulated into rod units; The elastic modulus of the nonlinear rod element capable of bearing only compression is the same as that of C35 concrete; The cross section of the beam unit is the same as that of a 60kg / m rail, and the material parameters are the same as those of steel; The elastic modulus of the solid unit is the same as that of C35 concrete; The spring stiffness parameters of the point-supported linear spring are selected as the vertical and lateral static stiffness of the node of the fastener respectively; Step 2: Set boundary conditions; Step 3: Modeling the simplified subway roadbed in the karst area to be simulated; In the modeling, the buoyancy under a single ballast plate to be calculated in the ballast body is fully distributed, and the influence of the buoyancy under other single ballast plates is ignored; Then, a plate is added on each side of the single track bed plate to be calculated to reduce the influence of boundary conditions on the calculation area; The buoyancy under the slab at this time is obtained according to the slab uplift limit of the single slab calculated as needed.

2. The method for simulating the floating of subway roadbed in karst areas based on finite element analysis software according to claim 1, characterized in that: The rails are 60kg / m rails with a gauge of 1435mm; the roadbed body and the lower backfill layer are both made of C35 concrete; the dimensions of each single roadbed plate of the roadbed body are 12.5m×2.4m×0.33m; the fastener spacing of the fastener system is 595mm.

3. The method for simulating the floating of subway roadbed in karst areas based on finite element analysis software according to claim 1, characterized in that: Step 2 is as follows: Step 2.1, apply fixed constraints at both ends of the beam element; Step 2.2: For the solid unit corresponding to the roadbed body, the beam slides horizontally, and the upward displacement is not constrained; Step 2.3: Apply fixed constraints to the rod element.

4. The method for simulating the floating of subway roadbed in karst areas based on finite element analysis software according to claim 1, characterized in that: By controlling the buoyancy within the lower range of the roadbed body or the connection between each single roadbed plate and the lower structure, the roadbed can be prevented from floating up. By preventing the buoyancy under the single roadbed plate from being greater than the weight of the roadbed, the elevation exceeding the limit occurs.

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