Design and calculation method of spacing of reinforcement bars in tension-wrapped reinforced soil roadbed

Abstract

The invention discloses an effective and feasible design and calculation method for the spacing of reinforcement bars of a tension-wrapped reinforced soil roadbed, comprising the following steps: step 10, preliminarily determining the proposed number of reinforcement layers and the proposed vertical spacing of reinforcement bars; step 20, calculating the resultant horizontal earth pressure of the inverted ends of the reinforcement bars of each layer according to the static equilibrium condition; step 30, determining the vertical critical spacing of reinforcement bars according to the pull-out stability condition of the inverted ends; step 40, if the vertical proposed spacing of reinforcement bars is less than or equal to the vertical critical spacing of reinforcement bars, entering step 50; if the vertical proposed spacing of reinforcement bars is greater than the vertical critical spacing of reinforcement bars, repeating steps 10 to 40; step 50, using the plastic limit analysis method to determine the internal overall stability coefficient of the tension-wrapped reinforced soil roadbed; step 60, if the internal overall stability coefficient is greater than or equal to the design stability safety factor, the calculation is terminated; if the internal overall stability coefficient is less than the design stability safety factor, repeating steps 10 to 60.

Description

Technical Field

[0001] The invention relates to the technical field of reinforced soil roadbed, and in particular to a design and calculation method for the spacing of reinforcement bars of a tension-wrapped reinforced soil roadbed. Background Art

[0002] The tension-wrapped reinforced soil roadbed is an improvement on the traditional reinforced soil roadbed. Each layer of horizontal reinforcement uses complete reinforcement materials. The ends of the reinforcements are reversely wrapped at the slope surface of the roadbed to form a local reverse wrapping end, which resists the lateral sliding of the soil and can better improve the bearing capacity of the reinforced soil roadbed. As one of the new reinforced soil structures, the vertical spacing of each layer of reinforcement is one of the key factors in engineering design, which directly determines the number of reinforcement materials that need to be laid for a roadbed with a fixed design height.

[0003] For traditional reinforced soil roadbed, the determination of the vertical spacing of the reinforcement is mainly based on engineering experience, supplemented by the classical limit equilibrium method of roadbed stability, in which the same design tension is adopted for each layer of reinforcement. However, unlike the traditional reinforced soil roadbed, the reversed ends formed by the reversed ends of the reinforcement are the distinctive structural features of the tension-wrapped reinforced soil roadbed, and the vertical spacing of the reinforcement is also closely related to the local stability of the reversed ends. However, in the past, there was a lack of design and calculation methods for the vertical spacing of the reinforcement of the tension-wrapped reinforced soil roadbed that took this factor into account.

[0004] In fact, since the tension-wrapped reinforced soil roadbed is a new type of reinforced soil roadbed structure, the design and calculation method of the vertical spacing of the reinforcement for the tension-wrapped reinforced soil roadbed is rarely reported. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an effective and feasible design and calculation method for the spacing of tie bars of a tension-wrapped reinforced soil roadbed.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a design and calculation method for the spacing of reinforcement bars of a tension-wrapped reinforced soil roadbed, and the technical scheme is as follows:

[0007] The design and calculation method for the spacing of the reinforcement bars of the tension-wrapped reinforced soil roadbed is characterized by comprising the following steps:

[0008] Step 10, preliminarily determining the proposed number of reinforcement layers and the proposed vertical reinforcement spacing based on the roadbed height and the empirical reference value of the reinforcement vertical spacing;

[0009] Step 20, according to the static equilibrium condition, calculate the horizontal earth pressure resultant of the reversed end of each layer of reinforcement;

[0010] Step 30, determining the vertical critical spacing of the reinforcement according to the pull-out stability condition of the turned-up end;

[0011] Step 40, determine the relationship between the proposed vertical spacing of the reinforcement and the critical vertical spacing of the reinforcement:

[0012] If the proposed vertical spacing of the reinforcement is less than or equal to the critical vertical spacing of the reinforcement, proceed to step 50;

[0013] If the proposed vertical spacing of the reinforcement is greater than the critical vertical spacing of the reinforcement, repeat steps 10 to 40, and when returning to step 10, increase the proposed number of reinforcement layers or decrease the proposed vertical spacing of the reinforcement until the proposed vertical spacing of the reinforcement is less than or equal to the critical vertical spacing of the reinforcement;

[0014] Step 50, based on the proposed vertical spacing of the reinforcement, the internal overall stability coefficient of the tension-wrapped reinforced soil roadbed is determined by using a plastic limit analysis method;

[0015] Step 60, determine the magnitude relationship between the internal overall stability coefficient and the design stability safety factor:

[0016] If the internal overall stability coefficient is greater than or equal to the design stability safety factor, the calculation is terminated. At this time, the proposed number of reinforcement layers is the design number of reinforcement layers, and the proposed vertical spacing of the reinforcement is the design vertical spacing of the reinforcement.

[0017] If the internal overall stability coefficient is less than the design stability safety factor, repeat steps 10 to 60, and when returning to step 10, increase the proposed number of reinforcement layers or reduce the proposed vertical spacing of reinforcement until the internal overall stability coefficient is greater than or equal to the design stability safety factor.

[0018] The design and calculation method for the spacing of reinforcement bars of the tension-wrapped reinforced soil roadbed of the present invention has the following advantages:

[0019] The present invention aims at the structural features of the two ends of the tension-wrapped reinforced soil roadbed. Firstly, the local pull-out stability of the turn-up end is fully considered and used as one of the control conditions of the vertical spacing of the reinforcement. Secondly, the plastic limit analysis method is used to analyze the internal overall stability of the tension-wrapped reinforced soil roadbed and use it as another control condition of the vertical spacing of the reinforcement. Therefore, the vertical spacing of the reinforcement of the tension-wrapped reinforced soil roadbed is calculated and determined based on the dual control conditions of the local pull-out stability of the turn-up end and the internal overall stability of the reinforced soil roadbed, providing an effective and feasible calculation method for the reinforcement design of the tension-wrapped reinforced soil roadbed structure in actual engineering.

[0020] The entire design and calculation process of the present invention is simple to operate and has good rationality. It can conveniently realize the design analysis and calculation of the vertical spacing problem of the reinforcement of the tension-wrapped reinforced earth roadbed, and can provide an effective method and scientific basis for the simple, efficient and rational design of the tension-wrapped reinforced earth roadbed engineering. It has important technical significance and engineering application value.

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting a part of the present invention are used to assist in understanding the present invention. The contents provided in the drawings and their related descriptions in the present invention can be used to explain the present invention, but do not constitute improper limitations on the present invention. In the drawings:

[0023] Figure 1 It is a general analysis model for the spacing of reinforcement bars in a tension-wrapped reinforced soil roadbed in the method of the present invention.

[0024] Figure 2 The following is a parameter table of a tension-wrapped reinforced earth embankment in an embodiment of the method of the present invention.

[0025] Figure 3 This is a comparison diagram of the internal sliding surface of the reinforced soil roadbed calculated by the method of the present invention and obtained by FLAC3D numerical simulation. DETAILED DESCRIPTION

[0026] The present invention is described clearly and completely below in conjunction with the accompanying drawings. A person skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0027] The technical solutions and technical features provided in each part of the present invention, including the following description, may be combined with each other if there is no conflict.

[0028] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0029] About the terms and units in the present invention: The terms "include", "have" and any variations thereof in the description and claims of the present invention and related parts are intended to cover non-exclusive inclusions.

[0030] Figure 1 It is a general analysis model for the spacing of reinforcement bars of the tension-wrapped reinforced soil roadbed in the method of the present invention. Figure 1 As shown, 100 is the roadbed fill, 200 is the reinforcement, 300 is the reverse end of the reinforcement, AB is the roadbed slope surface, and ABC is the sliding soil wedge.

[0031] based on Figure 1 The specific implementation method of the design and calculation method of the spacing of the reinforcement bars of the tension-wrapped reinforced soil roadbed of the present invention includes steps 10 to 60, which are respectively as follows:

[0032] Step 10: Preliminarily determine the proposed number of reinforcement layers and the proposed vertical reinforcement spacing based on the roadbed height and the empirical reference value of the reinforcement vertical spacing, specifically:

[0033] According to the roadbed height H, the empirical reference value of the vertical spacing of the reinforcement t e , preliminarily determine the number of layers n of the reinforcement, that is:

[0034]

[0035] Where, the empirical reference value of the vertical spacing of the reinforcement is t e It can generally be estimated to be 30 to 40 cm; int means rounding to the nearest integer.

[0036] Therefore, the proposed vertical spacing t0 of the reinforcement is preliminarily determined as:

[0037]

[0038] Step 20, according to the static equilibrium condition, calculate the horizontal earth pressure resultant of the reversed end of each layer of reinforcement, specifically:

[0039] According to the static equilibrium condition, the calculation expression of the resultant horizontal earth pressure at the reverse end of each layer of reinforcement is:

[0040]

[0041] Where, E is the horizontal earth pressure at the reverse end of each layer of reinforcement; γ is the weight of the roadbed fill; f is the friction coefficient of the reinforcement-soil interface, which can be taken as the tangent value of half of the internal friction angle of the roadbed fill; ε is the angle between the roadbed slope surface AB and the vertical direction; k e is the horizontal earth pressure coefficient; q is the top surface load of the roadbed, h q is the height of influence of the top surface load of the embankment. In particular, if h q <0, then take q=0.

[0042] Among them, the horizontal earth pressure coefficient k e and the influence height h of the roadbed top surface load q The calculation expressions are:

[0043] k e =(1-ξ)k0+ξk a (4)

[0044]

[0045] Where, ξ is the active earth pressure weight coefficient, which can generally be taken as 0.20-0.25; a is the horizontal clear distance between the top surface load of the roadbed and the inner side of the reinforcement reverse end; b is the distribution width of the top surface load of the roadbed; is the actual internal friction angle of the roadbed fill; k0 is the static earth pressure coefficient; k a is the active earth pressure coefficient.

[0046] Among them, the static earth pressure coefficient k0 and the active earth pressure coefficient k a The calculation expressions are:

[0047]

[0048] According to the triangular distribution of the horizontal earth pressure resultant E at the end of each layer of reinforcement, the horizontal earth pressure stress σ at the end of the i-th layer of reinforcement is calculated. i The calculation expression is:

[0049]

[0050] In the formula, z i is the depth of the i-th layer of reinforcement from the top surface of the roadbed, and i is the number of each layer of reinforcement starting from 1 and increasing from top to bottom.

[0051] Step 30, determining the vertical critical spacing of the reinforcement according to the pull-out stability condition of the turned-up end, specifically:

[0052] The equilibrium control equation of the pull-out stability condition of the turn-up end is:

[0053]

[0054] Where w is the width of the tie bar; λ is the vertical stress transfer reduction factor, which can generally be taken as 0.85-0.90; for the right side of equation (9), the upper and lower parts of the maximum lateral displacement point of the tie bar are respectively marked with - and +; T is the design tensile strength of the tie bar.

[0055] In this way, based on the pull-out stability condition of the tie bar turn-up end, the calculation expression of the vertical critical spacing of the tie bar can be obtained as follows:

[0056]

[0057] Where, t u It is the critical vertical spacing of the tie bars determined by the pull-out stability condition of the tie bar turn-up end.

[0058] Step 40, determine the relationship between the proposed vertical spacing of the reinforcement and the critical vertical spacing of the reinforcement:

[0059] If the proposed vertical spacing of the reinforcement t0 is less than or equal to the critical vertical spacing of the reinforcement tu (i.e., satisfying equation (10)), then proceed to step 50; i.e.

[0060] If the proposed vertical spacing of the reinforcement t0 is greater than the critical vertical spacing of the reinforcement t u (i.e., it does not satisfy equation (10)), then repeat steps 10 to 40, and when returning to step 10, increase the proposed number of reinforcement layers n or reduce the proposed vertical spacing t0 of the reinforcement until the proposed vertical spacing t0 of the reinforcement is less than or equal to the critical vertical spacing t u .

[0061] Step 50, based on the proposed vertical spacing of the reinforcement, determine the internal overall stability coefficient of the tension-wrapped reinforced soil roadbed, specifically:

[0062] For the sliding soil wedge ABC related to the internal overall stability of the tension-wrapped reinforced soil roadbed, the plastic limit analysis method is used to obtain its stability control equation:

[0063]

[0064] In the formula, c a Calculate cohesion for roadbed fill; is the calculated internal friction angle of roadbed fill; T i is the tension of the i-th layer of reinforcement; n is the total number of reinforcement layers; b0 is the top surface load width in the sliding soil wedge ABC; θ is the horizontal inclination angle of the plane sliding surface.

[0065] Among them, the calculation expression of the top surface load width b0 in the sliding soil wedge ABC is:

[0066]

[0067] The tension of the i-th layer of reinforcement T i The calculation expression is:

[0068]

[0069] Among them, s i is the normalized value of the lateral horizontal displacement of the i-th layer of reinforcement, s0 is the maximum value of the normalized value of the lateral horizontal displacement of the entire reversed end, that is, each s i The maximum value in .

[0070] s i The calculation is determined according to the position of the reinforcement in each layer, and the calculation expression is:

[0071] si=7.665yi 3 -17.188yi 2 +9.520yi+0.100 (14)

[0072] In the formula, s i It is a dimensionless quantity which is 1000 times the actual displacement divided by the roadbed height H; i It is the height of the i-th layer of reinforcement from the subgrade surface divided by the subgrade height H.

[0073] The stability factor F is introduced by using the strength reduction method. s ,Right now:

[0074]

[0075] In the formula, is the actual internal friction angle of the roadbed fill; c is the actual cohesion of the roadbed fill;

[0076] Therefore, substituting equation (15) into equation (11), we can get F s The internal overall stability coefficient F at the vertical spacing t0 of the reinforcement can be determined by formula (16): sc , which can be conveniently realized through computer calculation.

[0077]

[0078] Step 60, determine the magnitude relationship between the internal overall stability coefficient and the design stability safety factor:

[0079] If the internal overall stability factor F sc Greater than or equal to the design stability safety factor F s0 (i.e. F sc ≥F s0 ), the calculation is terminated, and the proposed number of reinforcement layers n is the designed number of reinforcement layers n d , the proposed vertical spacing of the reinforcement t0 is the vertical design spacing of the reinforcement t d ;

[0080] If the internal overall stability factor F sc Less than the design stability safety factor F s0 (i.e. F sc <F s0 ), then repeat steps 10 to 60, and when returning to step 10, increase the proposed number of reinforcement layers n or reduce the proposed vertical spacing t0 of the reinforcement until the internal overall stability coefficient F sc Greater than or equal to the design stability safety factor F s0 .

[0081] Therefore, the pull-out stability of the turn-up end (i.e., t0≤t u ) and internal overall stability (i.e., F sc ≥F s0 The minimum value of the proposed number of layers n of the reinforcement is taken as the design number of layers n of the reinforcement d, the corresponding proposed vertical spacing of the reinforcement t0 is used as the vertical design spacing of the reinforcement t d .

[0082] In the above-mentioned steps 40 and 60, it is preferred that the planned number of reinforcement layers is increased by one layer or the planned vertical spacing of the reinforcement is reduced by 0.05 m each time the process returns to step 10, so as to ensure better calculation accuracy.

[0083] The beneficial effects of the present invention are described below through application examples.

[0084] The horizontal reinforcement of a certain tension-wrapped reinforced earth embankment is made of HDPE geogrid material. The relevant parameters are shown in Figure 1 and Table 1.

[0085] Table 1

[0086]

[0087] The calculation process is as follows:

[0088] Step 10: Take the empirical reference value t of the vertical spacing of the reinforcement e =36cm, according to formula (1), the proposed number of reinforcement layers n=18, and according to formula (2), the proposed vertical spacing of reinforcement t0=0.361m.

[0089] Step 20, substitute the relevant parameters into equations (3) to (7) to calculate the horizontal earth pressure resultant E = 250.23 kN / m at the end of each layer of reinforcement. Then, equation (8) can be used to obtain the horizontal earth pressure stress σ at the end of the i-th layer of reinforcement: i =11.845z i .

[0090] Step 30, substitute the relevant parameters into formula (10) to calculate the vertical critical spacing of the reinforcement t u =0.327m.

[0091] Step 40, t0=0.361m>t u =0.327m, that is, the proposed vertical spacing of the reinforcement t0 is greater than the critical vertical spacing of the reinforcement t u , does not meet the pull-out stability requirements of the tie rod turn-up end;

[0092] First, return to step 10 and increase the number of vertical layers of reinforcement to n = 21, and recalculate according to formula (2) to obtain t0 = 0.310 m.

[0093] Then follow steps 20 and 30 to calculate t u =0.325m, at this time t0 = 0.310m < t u =0.325m, which meets the pulling stability requirements of the tie rod turn-up end.

[0094] Step 50, based on the currently calculated determined vertical spacing of the reinforcement t0 = 0.310 m, calculate the internal overall stability coefficient F of the tension-wrapped reinforced soil roadbed according to equations (11) to (16): sc =2.761.

[0095] Step 60, according to the design stability safety factor F required in Table 1 s0 =1.5, F sc =2.761≥F s0 , that is, the internal overall stability coefficient is greater than or equal to the design stability safety factor, which meets the internal overall stability requirements of the reinforced soil roadbed. Therefore, the proposed number of reinforcement layers n is the design number of reinforcement layers n d , the proposed vertical spacing of the reinforcement t0 is the vertical design spacing of the reinforcement t d , that is, n = n d =21, t0=t d =0.310m.

[0096] Results test:

[0097] Figure 3 The figure is a comparison of the internal sliding surface of the reinforced soil roadbed calculated by the method of the present invention and the one obtained by FLAC3D numerical simulation. Figure 3 As shown, the two are generally consistent.

[0098] The internal overall stability coefficient F obtained by the method of the present invention and FLAC3D numerical simulation sc They are 2.761 and 2.826 respectively, and the absolute value of their relative error is 2.3%.

[0099] The above results show that the method of the present invention is reasonable to a certain extent.

[0100] The above is a description of the relevant contents of the present invention. A person skilled in the art will be able to implement the present invention based on these descriptions. Based on the above contents of the present invention, all other embodiments obtained by a person skilled in the art without creative work shall fall within the scope of protection of the present invention.

Claims

1. The design and calculation method of the spacing of the reinforcement bars of the tension-wrapped reinforced soil roadbed is characterized by: The following steps are involved: Step 10, preliminarily determining the proposed number of reinforcement layers and the proposed vertical reinforcement spacing based on the roadbed height and the empirical reference value of the reinforcement vertical spacing; Step 20, according to the static equilibrium condition, calculate the horizontal earth pressure resultant of the reversed end of each layer of reinforcement; Step 30, determining the vertical critical spacing of the reinforcement according to the pull-out stability condition of the turned-up end; Step 40, determine the relationship between the proposed vertical spacing of the reinforcement and the critical vertical spacing of the reinforcement: If the proposed vertical spacing of the reinforcement is less than or equal to the critical vertical spacing of the reinforcement, proceed to step 50; If the proposed vertical spacing of the reinforcement is greater than the critical vertical spacing of the reinforcement, repeat steps 10 to 40, and when returning to step 10, increase the proposed number of reinforcement layers or decrease the proposed vertical spacing of the reinforcement until the proposed vertical spacing of the reinforcement is less than or equal to the critical vertical spacing of the reinforcement; Step 50, based on the proposed vertical spacing of the reinforcement, the internal overall stability coefficient of the tension-wrapped reinforced soil roadbed is determined by using a plastic limit analysis method; Step 60, determine the magnitude relationship between the internal overall stability coefficient and the design stability safety factor: If the internal overall stability coefficient is greater than or equal to the design stability safety factor, the calculation is terminated. At this time, the proposed number of reinforcement layers is the design number of reinforcement layers, and the proposed vertical spacing of the reinforcement is the design vertical spacing of the reinforcement. If the internal overall stability coefficient is less than the design stability safety factor, repeat steps 10 to 60, and when returning to step 10, increase the proposed number of reinforcement layers or reduce the proposed vertical spacing of reinforcement until the internal overall stability coefficient is greater than or equal to the design stability safety factor.

2. The design and calculation method for the spacing of reinforcement bars of the tension-wrapped reinforced soil roadbed according to claim 1 is characterized in that: In step 10: The calculation expression for the proposed number of layers of reinforcement is: The calculation expression for the proposed vertical spacing of the reinforcement is: Where H is the roadbed height, t e is the empirical reference value of the vertical spacing of the reinforcement, n is the planned number of reinforcement layers, int means rounding to the nearest integer, and t0 is the planned vertical spacing of the reinforcement.

3. The design and calculation method for the spacing of reinforcement bars of the tension-wrapped reinforced soil roadbed according to claim 2 is characterized in that: In step 20: The calculation expression of the resultant horizontal earth pressure at the reverse end of each layer of reinforcement is: Where, E is the resultant horizontal earth pressure at the reverse end of each layer of reinforcement; k e is the horizontal earth pressure coefficient; f is the friction coefficient of the reinforcement-soil interface; ε is the angle between the roadbed slope surface and the vertical direction; γ is the weight of the roadbed fill; q is the load on the top surface of the roadbed; h q It is the impact height of the top surface load of the roadbed.

4. The design and calculation method for the spacing of reinforcement bars of the tension-wrapped reinforced soil roadbed according to claim 3 is characterized in that: In step 30: The calculation expression of the critical vertical spacing of the reinforcement is: Where, t u is the vertical critical spacing of the reinforcement; T is the design tensile strength of the reinforcement; λ is the vertical stress transfer reduction factor; w is the width of the tie rod turned up end; z i is the depth of the i-th layer of reinforcement from the top surface of the roadbed; σ i is the horizontal soil compressive stress at the reverse end of the i-th layer of reinforcement; i is the number of each layer of reinforcement starting from 1 and increasing from top to bottom.

5. The design and calculation method for the spacing of reinforcement bars of the tension-wrapped reinforced soil roadbed according to claim 4 is characterized in that: In step 30: The equilibrium control equation of the pull-out stability condition of the turn-up end is:

6. The design and calculation method for the spacing of reinforcement bars of the tension-wrapped reinforced soil roadbed according to claim 4 is characterized in that: In step 50: The calculation equations for the internal overall stability coefficient are: In the formula, F s is the stability coefficient introduced by the strength reduction method, θ is the horizontal inclination angle of the plane sliding surface, according to Obtain the internal overall stability factor F under the proposed vertical spacing of the reinforcement sc ; Calculate the internal friction angle of the roadbed fill; is the actual internal friction angle of the roadbed fill; b0 is the top load width in the sliding soil wedge; c a is the calculated cohesion of the roadbed fill; c is the actual cohesion of the roadbed fill; T i is the tension of the i-th layer of reinforcement.

7. The design and calculation method for the spacing of reinforcement bars of the tension-wrapped reinforced soil roadbed according to claim 6 is characterized in that: In step 50: The calculation expression of the top load width b0 in the sliding soil wedge is: Where a is the horizontal clear distance between the load on the top surface of the roadbed and the inner side of the reversed end of the reinforcement; b is the load distribution width on the top surface of the roadbed.

8. The design and calculation method for the spacing of reinforcement bars of the tension-wrapped reinforced soil roadbed according to claim 6 is characterized in that: In step 50: The tension of the i-th layer of reinforcement T i The calculation expression is: In the formula, s i is the normalized value of the lateral displacement of the i-th layer of reinforcement, which is a dimensionless quantity of 1000 times its actual displacement divided by the roadbed height H; s0 is the maximum value of the normalized value of the lateral displacement of the entire reversed end, that is, each s i The maximum value in ; Normalized value s of the lateral horizontal displacement of the corresponding turn-up end of the i-th layer of reinforcement i The calculation expression is: si=7.665yi 3 -17.188yi 2 +9.520yi+0.100; In the formula, y i It is the height of the i-th layer of reinforcement from the subgrade surface divided by the subgrade height.

9. The design and calculation method for the spacing of reinforcement bars of a tension-wrapped reinforced soil roadbed according to claim 1 is characterized in that: In step 40 and step 60, each time the process returns to step 10, the planned number of reinforcement layers is increased by one layer or the planned vertical spacing of reinforcement is reduced by 0.05 m.

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