Design method for setting up anti-seepage layer between lining and surrounding rock

Abstract

The application provides a design method for setting a seepage prevention layer between a lining and surrounding rock, comprising the following steps: step one, establishing a two-dimensional finite element model of the lining, the seepage prevention layer and the surrounding rock according to the theoretical thickness of the seepage prevention layer, and calculating the lining axial force under an actual operation state; step two, calculating the lining crack width according to the lining axial force, and judging whether the crack width meets the corresponding design requirements; step three, performing a sensitivity analysis on the influence of the change of the elastic modulus of the seepage prevention layer on the lining axial force, obtaining a relationship curve of the lining axial force changing with the elastic modulus of the seepage prevention layer, and judging a critical elastic modulus Ecr according to the relationship curve; and step four, if the crack width in step two meets the corresponding design requirements and the elastic modulus of the seepage prevention layer under the actual operation state is always greater than the critical elastic modulus Ecr, then judging that the seepage prevention layer meets the design requirements. The seepage prevention layer is reasonably designed, the seepage prevention effect is ensured, and the operation safety of the overall structure is ensured.

Description

Technical Field

[0001] This invention relates to the field of seepage prevention design for water conveyance systems, and more particularly to a design method for setting a seepage prevention layer between the lining and the surrounding rock. Background Technology

[0002] In water conveyance systems, seepage prevention is usually required to limit the large amount of pressurized water in tunnels or wells from seeping out of the tunnels or wells. This is to prevent the loss of a large volume of water while conveying water, and is one of the foundations for ensuring the normal operation of the water conveyance system. It is also the foundation for ensuring that the water conveyance system does not suffer from safety accidents such as rock uplift or seepage damage.

[0003] Traditional seepage prevention measures often employ consolidation grouting to limit leakage or steel lining for seepage prevention. However, the quality of consolidation grouting is difficult to guarantee and is greatly affected by geological conditions. While steel lining for seepage prevention is reliable, the project cost is high. Currently, a new seepage prevention technology has emerged, which effectively resists leakage by setting a seepage barrier layer between the lining and the surrounding rock. This technology is low-cost and easy to construct. This technology typically uses a spraying method to apply the seepage barrier membrane between the lining and the surrounding rock. A soft pad layer should not be used to avoid large-area cavities. Although this sprayed material seepage prevention method is reliable and durable, how to rationally design the seepage barrier layer to achieve the seepage prevention effect of the sprayed membrane without affecting the structural safety of the lining itself and to ensure the safe operation of the overall structure is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a design method for setting an anti-seepage layer between the lining and the surrounding rock, which can solve the technical problem of how to rationally design the anti-seepage layer.

[0005] Therefore, the present invention adopts the following technical solution:

[0006] A design method for setting an impermeable layer between the lining and the surrounding rock includes the following steps:

[0007] Step 1: Based on the theoretical thickness of the impermeable layer, establish a two-dimensional finite element model of the lining, impermeable layer, and surrounding rock, and calculate the axial force of the lining under actual operating conditions.

[0008] Step 2: Calculate the lining crack width based on the lining axial force, and determine whether the crack width meets the corresponding design requirements based on the corrosivity level of the water being transported.

[0009] Step 3: Conduct a sensitivity analysis on the effect of the change in the elastic modulus of the impermeable layer on the axial force of the lining, obtain the relationship curve between the axial force of the lining and the change in the elastic modulus of the impermeable layer, and determine the critical elastic modulus Ecr based on the relationship curve between the axial force of the lining and the change in the elastic modulus of the impermeable layer.

[0010] Step 4: If the crack width in Step 2 meets the corresponding design requirements, and the elastic modulus of the impermeable layer is always greater than the critical elastic modulus Ecr under actual operation, then the impermeable layer is judged to meet the design requirements.

[0011] Based on the above technical solutions, the present invention may also employ the following further technical solutions, or combine these further technical solutions:

[0012] In step two, the stress of the reinforcing steel in the lining section is calculated based on the axial force of the lining: the lining concrete is assumed not to bear the axial force, and the reinforcing steel bears all the axial force. The stress of the reinforcing steel at the axial force is obtained by the cross-sectional area of ​​the reinforcing steel; the crack width is calculated based on the stress of the reinforcing steel.

[0013] The formula for calculating crack width is as follows:

[0014]

[0015] in:

[0016] Crack width, mm;

[0017] : Stress in steel reinforcement, MPa;

[0018] : Distance from the center of the reinforcing bar to the tensile outer surface of the lining concrete, mm;

[0019] : Spacing between reinforcing bars, mm.

[0020] Based on crack width To determine whether the lining meets the crack limiting requirements, for non-corrosive aquatic environments that are constantly submerged in water, No more than 0.3 mm.

[0021] In step three, the sensitivity analysis of the effect of the change in the elastic modulus of the impermeable layer on the axial force of the lining includes: keeping the theoretical thickness of the impermeable layer constant, calculating the change in the axial force of the lining when the elastic modulus of the impermeable layer changes from the initial value to zero, so as to obtain the relationship curve of the axial force of the lining with the change in the elastic modulus of the impermeable layer.

[0022] The elastic modulus of the impermeable layer is a dynamic variable that changes with elongation. Plot the relationship curve between the elastic modulus and elongation, and substitute the critical elastic modulus Ecr into the relationship curve to obtain the maximum elongation allowed for safe operation. Under actual operating conditions, the actual elongation of the impermeable layer is not greater than the maximum elongation.

[0023] A design method for setting an impermeable layer between the lining and the surrounding rock further includes step five: setting the elastic modulus of the impermeable layer as the critical elastic modulus E. crA sensitivity analysis was conducted on the effect of changes in the thickness of the geomembrane on the axial force of the lining. The relationship curve between the lining axial force and the thickness of the geomembrane was obtained. Based on the maximum allowable axial force of the lining for safe operation, the maximum thickness t of the geomembrane was determined. max .

[0024] The thickness of the impermeable layer is not greater than the maximum thickness tmax and the elastic modulus of the impermeable layer is not less than the critical elastic modulus E. cr Under the premise of ensuring safety, the axial force and crack width of the lining are calculated again to ensure that the requirements for safe operation are met.

[0025] The impermeable layer is a membrane applied between the lining and the surrounding rock using a spraying method.

[0026] Critical elastic modulus E cr The lower limit value that will not occur under actual operating conditions is that the elastic modulus of the geomembrane under actual operating conditions is greater than the critical elastic modulus E. cr .

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects: it achieves a reasonable design of the seepage prevention layer without affecting the structural safety of the lining itself, while ensuring the seepage prevention function and the overall structural operation safety. Attached Figure Description

[0028] Figure 1 This is a schematic diagram showing the relationship between the elastic modulus and elongation of the present invention.

[0029] Figure 2 This is a schematic diagram showing the relationship between the axial force of the lining and the elastic modulus of the impermeable layer in this invention.

[0030] Figure 3 This is a schematic diagram showing the relationship between the axial force of the lining and the thickness of the impermeable layer in this invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote elements with the same or similar functions throughout. However, it should be understood that the drawings are for illustrative purposes only and should not be construed as limiting the present invention. To better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size. It is understandable for those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present invention.

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0033] This invention provides a design method for setting an impermeable layer between the lining and the surrounding rock, comprising the following steps:

[0034] Step 1: Based on the theoretical thickness of the impermeable layer, establish a two-dimensional finite element model of the lining, impermeable layer, and surrounding rock, and calculate the axial force of the lining under actual operating conditions; the thickness of the sprayed film should be greater than the theoretical minimum value, and it is required to meet the requirements in the calculation of lining cracks;

[0035] Step 2: Calculate the width of the lining cracks based on the axial force of the lining. And based on the corrosivity level of the water being transported, determine whether the crack width meets the corresponding design requirements;

[0036] Step 3: Conduct a sensitivity analysis on the effect of the change in the elastic modulus of the impermeable layer on the axial force of the lining, obtain the relationship curve between the axial force of the lining and the change in the elastic modulus of the impermeable layer, and determine the critical elastic modulus E based on the relationship curve between the axial force of the lining and the change in the elastic modulus of the impermeable layer. cr ;

[0037] Step 4: If the crack width in Step 2 meets the corresponding design requirements, and the elastic modulus of the impermeable layer is always greater than the critical elastic modulus E under actual operating conditions. cr If the impermeable layer meets the design requirements, then it can be determined that the impermeable layer meets the design requirements.

[0038] In step two, the stress of the reinforcing steel in the lining section is calculated based on the axial force of the lining: the lining concrete is assumed not to bear the axial force, and the reinforcing steel bears all the axial force. The stress of the reinforcing steel at the axial force is obtained by the cross-sectional area of ​​the reinforcing steel; the crack width is calculated based on the stress of the reinforcing steel.

[0039] The formula for calculating crack width is as follows:

[0040]

[0041] in:

[0042] Crack width, mm;

[0043] : Stress in steel reinforcement, MPa;

[0044] : Distance from the center of the reinforcing bar to the tensile outer surface of the lining concrete, mm;

[0045] : Spacing between reinforcing bars, mm.

[0046] Based on crack width To determine whether the lining meets the crack limiting requirements, for non-corrosive aquatic environments that are constantly submerged in water, No more than 0.3 mm.

[0047] If the crack width does not meet the requirements, change the thickness of the spray film or change the material of the spray film (change to a material with a higher modulus of elasticity), and then re-simulate and calculate.

[0048] In step three, the sensitivity analysis of the effect of the change in the elastic modulus of the impermeable layer on the axial force of the lining includes: keeping the theoretical thickness of the impermeable layer constant, calculating the change in the axial force of the lining when the elastic modulus of the impermeable layer changes from the initial value to zero, so as to obtain the relationship curve of the axial force of the lining with the change in the elastic modulus of the impermeable layer.

[0049] The elastic modulus of the impermeable layer is a dynamic variable that varies with elongation. The relationship curve between the elastic modulus and elongation is plotted. The critical elastic modulus Ecr is substituted into the lining calculation model to calculate the stress on the lining. After obtaining the stress, the crack opening of the lining is calculated to determine whether the design requirements are met.

[0050] The present invention provides a design method for setting an impermeable layer between the lining and the surrounding rock, which further includes step five: setting the elastic modulus of the impermeable layer as the critical elastic modulus E. cr A sensitivity analysis was conducted on the effect of changes in the thickness of the geomembrane on the axial force of the lining. The relationship curve between the lining axial force and the thickness of the geomembrane was obtained. Based on the maximum allowable axial force of the lining for safe operation, the maximum thickness t of the geomembrane was determined. max .

[0051] The thickness of the impermeable layer shall not exceed the maximum thickness t max Furthermore, the elastic modulus of the impermeable layer is not less than the critical elastic modulus E. cr Under the premise of ensuring safety, the axial force and crack width of the lining are calculated again to ensure that the requirements for safe operation are met.

[0052] The impermeable layer is a membrane applied between the lining and the surrounding rock using a spraying method.

[0053] Critical elastic modulus E cr The lower limit value that will not occur under actual operating conditions is that the elastic modulus of the geomembrane under actual operating conditions is greater than the critical elastic modulus E. cr .

[0054] like Figure 2 As shown, the elastic modulus E corresponding to the curve showing the relationship between the axial force of the lining and the elastic modulus of the impermeable layer tends to flatten out is the critical elastic modulus. cr Determine the critical elastic modulus E cr =10MPa.

[0055] Based on the description and accompanying drawings of this invention, those skilled in the art can readily manufacture or use the design method of setting an impermeable layer between the lining and the surrounding rock according to this invention, and can produce the positive effects described in this invention.

[0056] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. The terms "installed," "set," "equipped with," "connected," "linked," and "sleeve" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral construction; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two mechanisms, elements, or components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0057] In the description of this invention, it should be understood that the terms "one end," "the other end," "outer side," "inner side," "horizontal," "end," "length," "outer end," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the mechanism or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. The terms "first" and "second" are also used only for the sake of brevity in description and do not indicate or imply relative importance.

[0058] Furthermore, in practicing the claims of this invention, those skilled in the art can understand and influence variations to the disclosed embodiments through a study of the drawings, the disclosure, and the appended claims. Additionally, in the claims and description, words such as "comprising" and "containing" do not exclude other elements or steps, and non-plural nouns do not exclude their plural forms.

[0059] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. All equivalent changes and modifications made in accordance with the present invention are covered by the scope of the claims of the present invention, and will not be listed here.

Claims

1. A design method for setting an impermeable layer between the lining and the surrounding rock, characterized in that, Includes the following steps: Step 1: Based on the theoretical thickness of the impermeable layer, establish a two-dimensional finite element model of the lining, impermeable layer, and surrounding rock, and calculate the axial force of the lining under actual operating conditions. Step 2: Calculate the width of the lining cracks based on the axial force of the lining. And based on the corrosivity level of the water being transported, determine whether the crack width meets the corresponding design requirements; Step 3: Conduct a sensitivity analysis on the effect of the change in the elastic modulus of the impermeable layer on the axial force of the lining, obtain the relationship curve between the axial force of the lining and the change in the elastic modulus of the impermeable layer, and determine the critical elastic modulus E based on the relationship curve between the axial force of the lining and the change in the elastic modulus of the impermeable layer. cr ; Step 4: If the crack width in Step 2 meets the corresponding design requirements, and the elastic modulus of the impermeable layer is always greater than the critical elastic modulus E under actual operating conditions. cr If the impermeable layer meets the design requirements, then it can be determined that the impermeable layer meets the design requirements.

2. The design method for setting an impermeable layer between the lining and the surrounding rock as described in claim 1, characterized in that, In step two, the stress of the steel reinforcement in the lining section is calculated based on the axial force of the lining: it is assumed that the lining concrete does not bear the axial force, and the steel reinforcement bears all the axial force. The stress of the steel reinforcement at the axial force is obtained by the cross-sectional area of ​​the steel reinforcement. Calculate the crack width based on the stress in the reinforcing steel.

3. The design method for setting an impermeable layer between the lining and the surrounding rock as described in claim 2, characterized in that, The formula for calculating crack width is as follows: in: Crack width, mm; : Stress in steel reinforcement, MPa; : Distance from the center of the reinforcing bar to the tensile outer surface of the lining concrete, mm; : Spacing between reinforcing bars, mm.

4. The design method for setting an impermeable layer between the lining and the surrounding rock as described in claim 3, characterized in that, Based on crack width To determine whether the lining meets the crack limiting requirements, for non-corrosive aquatic environments that are constantly submerged in water, No more than 0.3 mm.

5. The design method for setting an impermeable layer between the lining and the surrounding rock as described in claim 1, characterized in that, In step three, the sensitivity analysis of the effect of the change in the elastic modulus of the impermeable layer on the axial force of the lining includes: keeping the theoretical thickness of the impermeable layer constant, calculating the change in the axial force of the lining when the elastic modulus of the impermeable layer changes from the initial value to zero, so as to obtain the relationship curve between the axial force of the lining and the change in the elastic modulus of the impermeable layer.

6. A design method for setting an impermeable layer between the lining and the surrounding rock as described in claim 1 or 5, characterized in that, The elastic modulus of the impermeable layer is a dynamic variable that varies with elongation. A curve showing the relationship between the elastic modulus and elongation is plotted, and the critical elastic modulus E is determined. cr Substituting the relationship curve of elastic modulus with elongation, we obtain the maximum elongation allowed for safe operation. Under actual operating conditions, the actual elongation of the impermeable layer is not greater than the maximum elongation.

7. A design method for setting an impermeable layer between the lining and the surrounding rock as described in claim 1, characterized in that, It also includes step five: setting the elastic modulus of the impermeable layer as the critical elastic modulus E. cr A sensitivity analysis was conducted on the effect of changes in the thickness of the geomembrane on the axial force of the lining. The relationship curve between the lining axial force and the thickness of the geomembrane was obtained. Based on the maximum allowable axial force of the lining for safe operation, the maximum thickness t of the geomembrane was determined. max .

8. A design method for setting an impermeable layer between the lining and the surrounding rock as described in claim 7, characterized in that, The thickness of the impermeable layer shall not exceed the maximum thickness t max Furthermore, the elastic modulus of the impermeable layer is not less than the critical elastic modulus E. cr Under the premise of ensuring safety, the axial force and crack width of the lining are calculated again to ensure that the requirements for safe operation are met.

9. A design method for setting an impermeable layer between the lining and the surrounding rock as described in claim 1, characterized in that, The impermeable layer is a membrane applied between the lining and the surrounding rock using a spraying method.

10. A design method for setting an impermeable layer between the lining and the surrounding rock as described in claim 1, characterized in that, Critical elastic modulus E cr The lower limit value that will not occur under actual operating conditions is that the elastic modulus of the geomembrane under actual operating conditions is greater than the critical elastic modulus E. c .

Images