Existing line widening roadbed safety assessment and reinforcement area determination method

Abstract

The invention discloses a method for evaluating the safety of an existing line widening roadbed and determining a reinforcing area, and particularly relates to a method for numerically simulating a longitudinal and transverse differential settlement change curve and a horizontal displacement change curve of the surface and the surface of the roadbed in a new roadbed filling process. Calculating the maximum slope of the transverse and longitudinal unevenness of the steel rail required by the standard limit value when the train runs safely, and determining the safety state of the roadbed track by comparing the actual maximum slope with the allowable maximum slope; according to corresponding theories, a settlement area, larger than a subgrade bottom surface back calculation limit value, on the subgrade cross section is determined as a subgrade transverse reinforcing area range, and an area, larger than a steel rail limit slope, on the subgrade longitudinal section is determined as a subgrade longitudinal reinforcing area range; certain theoretical guidance is provided for evaluating the safety state of the roadbed during widening construction of the existing line and determining the range of a reinforcing area.

Description

Technical Field

[0001] The invention belongs to the technical field of line safety assessment, and in particular relates to a method for assessing the safety of existing line side width roadbed and determining a reinforcement area. Background Art

[0002] The additional stress generated by the existing line subgrade widening construction will cause uneven settlement in the longitudinal and transverse sections of the old subgrade. Excessive settlement differences in the longitudinal and transverse sections will cause the longitudinal and transverse height differences of the existing track to exceed the limit, thereby causing train derailment accidents. Therefore, it is necessary to establish a method for safety assessment of the existing line subgrade widening and determination of reinforcement areas, in order to provide useful guidance for the existing line subgrade widening project.

[0003] At present, there is a technical gap in the evaluation of the safety status of the roadbed and the determination of the scope of the reinforcement area during the widening process of the existing line. Only some literatures have proposed differential settlement control standards and simple theories for calculating settlement control limits. For example, in 2008, Fu Zhen et al. proposed corresponding control indicators for uneven foundation settlement from the perspective of road pavement structure mechanical response such as fatigue attenuation of asphalt pavement materials, ultimate tensile strength, pavement flatness and traffic load based on the differential settlement model; in 2010, Zhang Meikun obtained the differential settlement classification standards and control indicators for widened roads through research on pavement structure requirements, flatness requirements and material fatigue characteristics based on the differential settlement model; in 2012, Song Ci et al. used ABAQUS based on the differential settlement model to obtain the maximum lateral slope change rate of differential settlement in the actual widening project of Hening Expressway is no more than 0.4%, and the general lateral slope change rate is no more than 0.254%; in 2013, Weng Xiaolin et al. studied the differential settlement model of filling and filling. The influence of square height, widening ratio, elastic modulus of embankment and foundation filling on the lateral uneven settlement of highway widening foundation was studied, and the relationship between the lateral differential settlement limit S of foundation and the widening ratio of new and old embankments and the reverse slope rate of pavement structure was established; in 2013, Chen Renpeng et al. analyzed the forces under long-wave uneven settlement of type II track slab of high-speed railway ballastless track, and on this basis, controlled the long-wave uneven settlement of high-speed railway subgrade based on the bending fatigue strength of track slab; in 2014, Luo Qiang et al. analyzed the longitudinal differential settlement diffusion characteristics and transmission law of non-widened railway embankment foundation based on differential settlement model, and proposed the longitudinal differential settlement control standard of embankment foundation based on the longitudinal uneven deformation limit of subgrade surface; in 2015, Wang Wenyang suggested that the road surface cross slope deviation i≤0.3% be used as the quality control index for road engineering construction when the construction is completed, and the road surface cross slope change rate i≤0.46% be used as the differential settlement control during the use stage of pavement structure.

[0004] Many reinforcement measures proposed so far have achieved the safe construction of existing line side widening roadbed projects, but there are relatively few methods for safety assessment of existing line side widening roadbed and determination of reinforcement areas. Therefore, there is a certain blindness in the grasp of the dynamic safety of the roadbed construction process, especially the differential settlement of the longitudinal and transverse directions of the existing line rails. Summary of the invention

[0005] In order to combine relevant specifications and realize the safety status assessment of the roadbed and the determination of the reinforcement area during the existing line side width construction from a theoretical level, the vertical and horizontal displacements of the top and bottom surfaces of the roadbed are calculated according to numerical simulation. Based on the displacement curve characteristics, differential settlement model, specification limits and corresponding theories, the present invention proposes a method for safety assessment of the existing line side width roadbed and determination of the reinforcement area.

[0006] To this end, the present invention adopts the following technical solutions:

[0007] A method for safety assessment of existing line width roadbed and determination of reinforcement area comprises the following steps:

[0008] 1) Establish a finite element simulation model according to the existing line foundation dimensions;

[0009] 2) In the simulation model, under the condition of no-width filling layer, the initial displacement of the top and bottom surfaces of the roadbed is reset to zero to eliminate the influence of the initial stress field;

[0010] 3) Fill the wide layer of the roadbed and calculate the vertical displacement curves of the top and bottom surfaces of the roadbed with and without train loads along with the transverse and longitudinal sections of the roadbed;

[0011] 4) Safety status assessment of roadbed cross section:

[0012] a. Refer to the track roughness limit [Δh] in the Railway Track Design Specification (TB 10082) and calculate the rail roughness limit slope [i];

[0013] [i]=[Δh] / L

[0014] Where: L is the distance between the centers of the rail sections;

[0015] b. Based on the differential settlement model and the change curve of step 3), calculate the maximum differential settlement cross slope failure rate i of the top surface of the roadbed n,max :

[0016] i n,max =Δh n,max / ΔL n

[0017] Where: Δh n,max is the maximum differential settlement value within the existing roadbed when the nth layer is filled;

[0018] ΔL n The distance that the wheels do not derail when filling the nth layer;

[0019] ① Take the right side width of a single-track railway as an example: when the maximum settlement is located inside the center line of the rail, take the horizontal distance from the center line of the left rail to the maximum settlement; when the maximum settlement is located on the center line of the rail or on its outside, take the horizontal distance between the center lines of the two rails. ② Take the double-sided side width of a single-track railway as an example: when the maximum settlement is located inside the center line of the rail, take the horizontal distance from the center line of the roadbed to the maximum settlement; when the maximum settlement is located on the center line of the rail or on its outside, take the horizontal distance from the center line of any rail to the maximum settlement;

[0020] c. Cross-section safety status assessment: i n,max ≥[i], unsafe; i n,max <[i], safe;

[0021] 5) Safety status assessment of roadbed longitudinal section:

[0022] a. Refer to the track longitudinal differential settlement limit slope [k] in the Railway Track Design Specifications (TB 10082);

[0023] b. Remember k ni =(x ni+1 -x ni ) / (y ni+1 -y ni ), where i = 1, 2, ..., m, then take:

[0024] k n,max =max(k n1 , k n2 ..., k nm )

[0025] c. Longitudinal section safety status assessment: k n,max ≥[k], unsafe; k n,max <[k], safe;

[0026] 6) Determination of the scope of the cross-section reinforcement area:

[0027] a. Based on the roadbed displacement curve of step 3), determine the location where the maximum settlement of the roadbed occurs, and then determine the value of ΔL;

[0028] b. Calculate the maximum allowable settlement displacement of the roadbed surface, i.e. the foundation [h] max :

[0029] [h n ] max =[i]·ΔL n -h n0

[0030] Where: h n0 = ΔL n The settlement or uplift value at the starting point, if it is settlement, it is a negative value, if it is uplift, it is a positive value;

[0031] c. n ] max The value is used as the reference, and a horizontal line is drawn. The area below the horizontal line where the settlement value is located is the cross-section reinforcement area when the nth layer is filled.

[0032] 7) Determination of the scope of the longitudinal section reinforcement area:

[0033] a. Let k ni =(y ni+1 -y ni ) / (x ni+1 -x ni ) = [k];

[0034] b. If the equation has no solution, the roadbed does not need to be reinforced longitudinally;

[0035] If this equation has a solution, find the two corresponding points A on the numerical displacement curve when the nth layer is filled. n and B n ; Then the reinforcement area of ​​the longitudinal section when the nth layer is filled is:

[0036]

[0037] c. When [k] = 0, the range of the longitudinal reinforcement area of ​​the roadbed surface reaches its maximum value.

[0038] The beneficial effects of the present invention are:

[0039] Many reinforcement measures proposed in the prior art have achieved the safe construction of existing line widening roadbed projects, but there are relatively few methods for safety assessment of existing line widening roadbed and determination of reinforcement areas. Therefore, there is a certain blindness in the grasp of the dynamic safety of the roadbed construction process, especially the differential settlement of the longitudinal and transverse directions of the existing line rails. Therefore, in order to be able to combine relevant specifications, realize the safety status assessment of the roadbed and the determination of the scope of the reinforcement area during the existing line widening construction from a theoretical level, according to the numerical simulation calculation of the vertical and horizontal displacements of the top and bottom surfaces of the roadbed, based on the displacement curve characteristics, differential settlement model, specification limit and corresponding theory, an innovative method for safety status assessment of existing line widening roadbed and determination of reinforcement area scope is proposed, which can provide useful guidance for existing line widening projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flowchart of the evaluation method of the present invention;

[0041] Figure 2is a schematic diagram of step 1) establishing a finite element simulation model;

[0042] Figure 3 It is a schematic diagram of the initial displacement returning to zero in step 2;

[0043] Figure 4 is a schematic diagram of the change curve in step 3);

[0044] Figure 5 is the maximum settlement displacement in step 6) [h] max Graph of the curve. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The specific steps are as follows:

[0046] 1) If Figure 1 As shown in the figure, a finite element simulation model is established according to the existing line foundation dimensions.

[0047] 2) If Figure 2 As shown in the figure, in the simulation model, under the non-width filling layer, the initial displacements of the top and bottom surfaces of the roadbed are reset to zero to eliminate the influence of the initial stress field.

[0048] 3) If Figure 3 As shown in the figure, the wide layer of the roadbed is filled, and the vertical displacement of the top and bottom surfaces of the roadbed with and without train loads is numerically calculated as a function of the transverse and longitudinal sections of the roadbed.

[0049] 4) Safety status assessment of roadbed cross section:

[0050] a. Check and determine the track roughness limit [Δh] and calculate the rail roughness limit slope [i];

[0051]

[0052] b. Based on the differential settlement model and displacement curve, calculate the maximum differential settlement cross slope failure rate i of the roadbed top surface n,max :

[0053] i n,max =Δh n，max / ΔL n

[0054] Old roadbed:

[0055] New roadbed:

[0056] c. Cross-section safety status assessment:

[0057] For existing railways, n,max =4.38%o>[i=4.18‰, unsafe;

[0058] For new railways, n,max =1.298%>[i=1.045%, unsafe.

[0059] 5) Safety status assessment of roadbed longitudinal section:

[0060] a. Refer to the track longitudinal differential settlement limit slope [k] in the Railway Track Design Specification (TB 10082-2017);

[0061] b. Remember k ni =(x ni+1 -x ni ) / (y ni+1 -y ni ), where i = 1, 2, ..., m, then take:

[0062] k n,max =max(k n1 , k n2 ......, k nm )

[0063] c. Longitudinal section safety status assessment: k n,max ≥[k], unsafe; k n,max <[k], safe;

[0064] 6) Determination of the scope of the cross-section reinforcement area:

[0065] a. Based on the roadbed displacement curve calculated in step 3), determine the location where the roadbed surface has the maximum settlement, and then determine the value of ΔL;

[0066] b. Calculate the maximum allowable settlement displacement of the roadbed surface (i.e. foundation) [h] max :

[0067] [h n ] max =[i]ΔL n -h n0 =0.00418×16300-2.48=65.7mm

[0068] c. n ] max The value is used as the reference, and a horizontal line is drawn. The area below the horizontal line where the settlement value is located is the cross-section reinforcement area when the nth layer is filled.

[0069] 7) Determination of the scope of the longitudinal section reinforcement area:

[0070] d. When the line is 2700m long and the vertical settlement displacement is 65.7mm, the slope of the line settlement displacement difference is calculated. From the knowledge of advanced mathematical differential calculus, we know that a continuous function is differentiable on an open interval, and the first-order derivative on a closed interval is not zero. Then there is a first-order derivative at some point, that is, the function is monotonic.

[0071] e. The reinforcement area of ​​the longitudinal section when the nth layer is filled is:

[0072] L n =2700m

[0073] When [k] = 0, it means strict settlement displacement limit, [h n ] max For the range below the baseline, the entire foundation needs to be reinforced.

Claims

1. A method for safety assessment of existing roadbed width and determination of reinforcement area, characterized in that: The following steps are involved: 1) Establish a finite element simulation model according to the existing line foundation dimensions; 2) In the simulation model, under the non-width filling layer, the initial displacement of the top and bottom surfaces of the roadbed are set to zero to eliminate the influence of the initial stress field; 3) Fill the wide layer of the roadbed and calculate the vertical displacement curves of the top and bottom surfaces of the roadbed with and without train loads along with the transverse and longitudinal sections of the roadbed; 4) Safety status assessment of roadbed cross section: a. Check and determine the track roughness limit [Δh] and calculate the rail roughness limit slope [i]; [i]=[Δh] / L Where: L is the distance between the centers of the rail sections; b. Based on the differential settlement of the longitudinal and transverse railway track surface and the change curve of step 3), calculate the maximum differential settlement of the top surface of the roadbed and the transverse slope failure rate i n,max : i n,max =Δh n,max / ΔL n Where: Δh n,max is the maximum differential settlement value within the existing roadbed when the nth layer is filled; ΔL n The distance that the wheels do not derail when filling the nth layer; c. Cross-section safety status assessment: i n,max ≥[i], unsafe; i n,max <[i], safety; 5) Safety status assessment of roadbed longitudinal section: a. Check and determine the track longitudinal differential settlement limit slope [k]; b. Remember k ni =(y ni+1 -y ni ) / (x ni+1 -x ni ), where i = 1, 2, ..., m, then take: k n,max =max(k n1 ,k n2 ……,k nm ) c. Longitudinal section safety status assessment: k n,max ≥[k], unsafe; k n,max <[k], safe; 6) Determination of the scope of the cross-section reinforcement area: a. Based on the roadbed displacement curve of step 3), determine the location where the maximum settlement of the roadbed occurs, and then determine the value of ΔL; b. Calculate the maximum allowable settlement displacement of the roadbed surface, i.e. the foundation [h] max : [h n ] max =[i]·ΔL n -h n0 Where: h n0 = ΔL n The settlement or uplift value at the starting point, if it is settlement, it is a negative value, if it is uplift, it is a positive value; c. n ] max The value is used as the reference, and a horizontal line is drawn. The area below the horizontal line where the settlement value is located is the cross-section reinforcement area when the nth layer is filled. 7) Determination of the scope of the longitudinal section reinforcement area: a. Let k ni = (x ni+1 - x ni ) / (y ni+1 - y ni ) = [k]; b. If the equation has no solution, the roadbed does not need to be reinforced longitudinally; If this equation has a solution, find the two corresponding points A on the numerical displacement curve when filling the nth layer. n and B n ; Then the reinforcement area of ​​the longitudinal section when the nth layer is filled is: c. When [k] = 0, the range of the longitudinal reinforcement area of ​​the roadbed surface reaches its maximum value.

2. The method for safety assessment of existing roadbed width and determination of reinforcement area according to claim 1 is characterized in that: In step 4), ΔL n The method of determining is as follows: When the right side of a single-track railway is wide: when the maximum settlement is located inside the centerline of the rail, take the horizontal distance between the centerline of the left rail and the maximum settlement; when the maximum settlement is located on the centerline of the rail or outside it, take the horizontal distance between the centerlines of the two rails; For the double-sided width of a single-track railway: when the maximum settlement is located inside the rail centerline, take the horizontal distance from the centerline of the roadbed to the maximum settlement; when the maximum settlement is located on the rail centerline or outside of it, take the horizontal distance from the centerline of any rail to the maximum settlement.

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