Levee foundation semi-closed type anti-seepage method and system

Abstract

The invention relates to the technical field of embankment foundation seepage prevention, in particular to an embankment foundation semi-closed seepage prevention method and system.According to the method, it is assumed that an embankment body is waterproof, the surface layer of an embankment foundation is a shallow permeable layer, the second layer is a relatively weak permeable layer, and a deep permeable layer is arranged below the second layer; and the thickness and the permeability coefficient of the anti-seepage supporting layer are determined, the depth of the semi-closed type anti-seepage wall entering the anti-seepage supporting layer is determined, and the arrangement range of the semi-closed type anti-seepage wall avoiding surrounding seepage damage is determined. According to the method, the semi-closed type anti-seepage wall and the anti-seepage supporting layer form a complete anti-seepage system, the design accuracy of the semi-closed type anti-seepage wall is ensured, and theoretical and technical supports can be provided for dike engineering design specifications about the design of the semi-closed type anti-seepage wall; and the method has important theoretical and engineering practical significance for promoting deep development of a semi-closed diaphragm wall technology. The technical problems that an existing design method is large in fuzziness and arbitrariness and high in safety risk can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of dike foundation anti-seepage, and in particular to a semi-closed dike foundation anti-seepage method and system. Background Art

[0002] For a multi-structure embankment foundation with alternating strong and weak permeable layers, when a semi-closed anti-seepage wall is used, the semi-closed anti-seepage wall passes through the relatively strong permeable layer and enters the relatively weak permeable layer, and there is a relatively strong permeable layer below the relatively weak permeable layer. The semi-closed anti-seepage system formed by the relatively weak permeable layer and the semi-closed anti-seepage wall is effective in reducing foundation seepage and hydraulic gradient.

[0003] When using a semi-closed anti-seepage wall, what conditions must the relatively weak permeable layer meet to serve as a reliable anti-seepage support layer? How deep should the semi-closed anti-seepage wall enter the relatively weak permeable layer to ensure a reliable seepage control effect? ​​How to avoid bypass seepage? For these issues, the current design specifications and relevant literature do not provide regulations, resulting in engineering and technical personnel having no rules to follow when designing seepage control for semi-closed anti-seepage walls. The design is relatively ambiguous and arbitrary, resulting in danger in actual projects. It is necessary to conduct in-depth research on it and find a scientific solution. Summary of the invention

[0004] The purpose of the present invention is to provide a semi-closed anti-seepage method and system for embankment foundation, which can solve the technical problems of existing design methods with large ambiguity and arbitrariness and high safety risks.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention designs a semi-closed anti-seepage method for embankment foundation, comprising the following steps:

[0007] Assume that the embankment is impermeable, the surface layer is a shallow permeable layer, the second layer is a relatively weak permeable layer, and the layer below the second layer is a deep permeable layer;

[0008] Taking the relatively weak permeable layer as the anti-seepage support layer, determining the thickness and permeability coefficient of the anti-seepage support layer requires two conditions to be met:

[0009] (1) The equivalent seepage path from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is greater than the equivalent seepage path from the upstream side of the shallow aquitard through the semi-enclosed anti-seepage wall to the same position on the surface of the downstream side of the shallow aquitard;

[0010] (2) The vertical gradient from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is less than the hydraulic gradient allowed by the shallow aquitard;

[0011] To determine the depth of the semi-enclosed anti-seepage wall into the anti-seepage supporting layer, it is necessary to meet the requirement that the equivalent seepage path from the bottom of the shallow permeable layer to the relatively weak permeable layer and then back to the bottom of the shallow permeable layer is greater than the equivalent seepage path from the shallow permeable layer through the semi-enclosed anti-seepage wall;

[0012] Determine the layout range of the semi-closed anti-seepage wall to avoid bypass seepage damage. That is, if seepage damage occurs somewhere on the ground behind the embankment, determine the extension length of this section of the anti-seepage wall on both sides along the embankment line. The equivalent seepage path from the shallow permeable layer through the semi-closed anti-seepage wall directly to the seepage damage point must be smaller than the equivalent seepage path from the shallow permeable layer bypassing the semi-closed anti-seepage wall to the end of the extension length to the seepage damage point.

[0013] As a preferred solution, the two conditions that need to be met to determine the thickness and permeability coefficient of the anti-seepage support layer are:

[0014] Taking the permeability coefficient k1 of the shallow permeable layer as the conversion basis for the equivalent seepage path length, then:

[0015]

[0016] Right now:

[0017]

[0018] Where: k1 is the permeability coefficient of the shallow aquitard, k2 is the permeability coefficient of the relatively weak permeable layer, k3 is the permeability coefficient of the semi-enclosed anti-seepage wall, h1 is the thickness of the shallow permeable layer, h2 is the thickness of the relatively weak permeable layer, d is the thickness of the semi-enclosed anti-seepage wall, L is the length of the semi-enclosed anti-seepage wall from the inner foot of the embankment, H is the head difference between upstream and downstream, J G The hydraulic gradient allowed for the shallow aquitard;

[0019] According to formula (3) and formula (4), the thickness of the anti-seepage supporting layer and the permeability coefficient that meet the seepage control requirements can be obtained, and the larger value is taken for the thickness of the anti-seepage supporting layer.

[0020] As a preferred solution, the depth of the semi-enclosed anti-seepage wall into the anti-seepage supporting layer is determined, and the specific conditions are:

[0021] Taking the permeability coefficient k1 of the shallow permeable layer as the conversion basis for the equivalent seepage path length, then:

[0022]

[0023] Right now:

[0024]

[0025] Where: t is the depth of the semi-enclosed anti-seepage wall entering the relatively weak permeable layer; according to formula (6), the depth of the anti-seepage wall that meets the seepage control requirements entering the anti-seepage supporting layer can be calculated.

[0026] As a preferred solution, the layout range of the semi-enclosed anti-seepage wall to avoid damage caused by bypass seepage is determined as follows:

[0027] Taking the permeability coefficient k1 of the shallow permeable layer as the conversion basis for the equivalent seepage path length, then:

[0028]

[0029] Where: b is the distance from the danger point to the downstream side of the cut-off wall, and W is the extension length of the cut-off wall along the embankment line. The minimum value of the extension length W can be calculated according to formula (7).

[0030] The present invention also designs a semi-closed anti-seepage system for embankment foundation, comprising the following modules:

[0031] The dike base layer module is used to determine that the surface layer is a shallow aquitard, the second layer is a relatively weak aquitard, and the layer below the second layer is a deep aquitard;

[0032] The anti-seepage support layer module is used to use the relatively weak permeable layer as a reliable anti-seepage support layer. To determine the thickness and permeability coefficient of the anti-seepage support layer, two conditions must be met:

[0033] (1) The equivalent seepage path from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is greater than the equivalent seepage path from the upstream side of the shallow aquitard through the semi-enclosed anti-seepage wall to the same position on the surface of the downstream side of the shallow aquitard;

[0034] (2) The vertical gradient from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is less than the hydraulic gradient allowed by the shallow aquitard;

[0035] The module of entry depth into the anti-seepage supporting layer is used to determine the depth of the semi-enclosed anti-seepage wall entering the anti-seepage supporting layer. The equivalent seepage path from the bottom of the shallow permeable layer to the relatively weak permeable layer and then back to the bottom of the shallow permeable layer must be greater than the equivalent seepage path from the shallow permeable layer through the semi-enclosed anti-seepage wall.

[0036] The cut-off wall layout module is used to determine the layout range of the semi-closed cut-off wall to avoid seepage damage. That is, if seepage damage occurs somewhere on the ground behind the embankment, the extension length of this section of the cut-off wall on both sides along the axial direction of the embankment must be determined to ensure that the equivalent seepage path from the shallow permeable layer through the semi-closed cut-off wall directly to the seepage damage point is smaller than the equivalent seepage path from the shallow permeable layer to the end of the extension length of the semi-closed cut-off wall and then to the seepage damage point.

[0037] Beneficial effects of the present invention:

[0038] The present invention provides a semi-closed anti-seepage method and system for embankment foundation, which can solve the technical problems of existing design methods with large ambiguity and arbitrariness and high safety risks.

[0039] (1) The present invention clarifies the relationship between the thickness of the anti-seepage supporting layer and the permeability coefficient that satisfies the seepage control effect of the semi-enclosed anti-seepage wall, so that engineering and technical personnel can understand in the design what conditions the thickness and permeability coefficient of the anti-seepage supporting layer must meet to be used as the anti-seepage supporting layer.

[0040] (2) The present invention clarifies a method for calculating the depth of an anti-seepage wall entering an anti-seepage supporting layer in the design of a semi-enclosed anti-seepage wall.

[0041] (3) The present invention clarifies the calculation method for the layout range of the anti-seepage wall to avoid bypass seepage.

[0042] The invention enables the semi-closed anti-seepage wall and the anti-seepage supporting layer to form a complete anti-seepage system, thereby ensuring the accuracy of the design of the semi-closed anti-seepage wall. It can provide theoretical and technical support for the design of semi-closed anti-seepage walls in the embankment engineering design specifications, and has important theoretical and engineering practical significance for promoting the in-depth development of semi-closed anti-seepage wall technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the anti-seepage mechanism of the semi-closed anti-seepage wall of the present invention.

[0044] Figure 2 This is a top view of the semi-enclosed anti-seepage wall of the present invention to prevent bypass seepage.

[0045] Figure 3 Schematic diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings and through specific embodiments. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the accompanying drawings, not all.

[0047] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0048] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] The present invention relates to a semi-enclosed anti-seepage method and system for embankment foundation, which solves the problem that the current semi-enclosed anti-seepage wall has no rules to follow, the design is vague and arbitrary, and causes dangers in actual projects. The present invention can specifically solve the following technical problems:

[0050] (1) For a semi-enclosed anti-seepage wall, the water penetrates through the shallow permeable layer into the relatively weak permeable layer (or anti-seepage supporting layer). Then, what conditions should the permeability and thickness of the relatively weak permeable layer, which serves as the anti-seepage supporting layer, meet?

[0051] (2) For a semi-enclosed anti-seepage wall, how deep must it penetrate through the shallow permeable layer into the relatively weak permeable layer (or the anti-seepage supporting layer) to play an effective anti-seepage role.

[0052] (3) When a seepage hazard occurs somewhere behind the dike, if a semi-enclosed anti-seepage wall is used for treatment, the problem is how to reasonably determine the treatment range of the anti-seepage wall along the dike line, that is, how to avoid the problem of bypass seepage.

[0053] Solving the above three problems can make the anti-seepage effect of the semi-closed cutoff wall reliable and safe, while reducing the ambiguity and arbitrariness of the design, ensuring the accuracy of the design of the semi-closed cutoff wall, and providing theoretical and technical support for the design of semi-closed cutoff walls in the embankment engineering design specifications.

[0054] The present invention provides a semi-closed anti-seepage method for embankment foundation, comprising the following steps:

[0055] Step 1. Assume that the embankment is impermeable, the surface layer is a shallow permeable layer, the second layer is a relatively weak permeable layer, and the layer below the second layer is a deep permeable layer;

[0056] Step 2. Take the relatively weak permeable layer as a reliable anti-seepage support layer and determine the thickness and permeability coefficient of the anti-seepage support layer. Two conditions must be met:

[0057] (1) The equivalent seepage path from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is greater than the equivalent seepage path from the upstream side of the shallow aquitard through the semi-enclosed anti-seepage wall to the same position on the surface of the downstream side of the shallow aquitard;

[0058] (2) The vertical gradient from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is less than the hydraulic gradient allowed by the shallow aquitard;

[0059] Step 3. Determine the depth of the semi-enclosed anti-seepage wall into the anti-seepage supporting layer, which must satisfy the requirement that the equivalent seepage path from the bottom of the shallow permeable layer to the relatively weak permeable layer and then back to the bottom of the shallow permeable layer is greater than the equivalent seepage path from the shallow permeable layer through the semi-enclosed anti-seepage wall;

[0060] Step 4. Determine the layout range of the semi-closed anti-seepage wall to avoid bypass seepage damage. That is, if seepage damage occurs somewhere on the ground behind the embankment, determine the extension length of this section of the anti-seepage wall on both sides along the embankment line. The equivalent seepage path from the shallow permeable layer through the semi-closed anti-seepage wall directly to the seepage damage point must be smaller than the equivalent seepage path from the shallow permeable layer bypassing the semi-closed anti-seepage wall to the end of the extension length to the seepage damage point.

[0061] The specific steps are as follows:

[0062] Step 1. Determine the stratum of the dike base;

[0063] like Figure 1 As shown, assuming that the embankment is impermeable, when the surface layer is a shallow permeable layer, the second layer is a relatively weak permeable layer, and the layer below the second layer is a deep permeable layer;

[0064] Step 2. Thickness and permeability coefficient of the anti-seepage support layer;

[0065] If a relatively weak permeable layer can be used as a reliable anti-seepage support layer, two conditions must be met:

[0066] (1) The equivalent seepage path from J→H→G is greater than the equivalent seepage path from A→F→G;

[0067] (2) The outflow slope from J→H→G must be less than the allowable hydraulic slope J at point G. G .

[0068] The first condition prevents the relatively weak aquitard from being too thin or having a too large permeability coefficient, causing the deep aquitard to break through the anti-seepage support layer; the second condition is to meet the anti-seepage requirements. If the permeability coefficient k1 of the shallow aquitard is used as the basis for the conversion of the equivalent seepage path length, the requirements are:

[0069]

[0070]

[0071] Right now:

[0072]

[0073] Where: k1 is the permeability coefficient of the shallow aquitard, k2 is the permeability coefficient of the relatively weak permeable layer, k3 is the permeability coefficient of the semi-enclosed anti-seepage wall, h1 is the thickness of the shallow permeable layer, h2 is the thickness of the relatively weak permeable layer, d is the thickness of the semi-enclosed anti-seepage wall, L is the length of the semi-enclosed anti-seepage wall from the inner foot of the embankment, H is the head difference between upstream and downstream, J G The hydraulic gradient allowed for the shallow aquitard;

[0074] According to formula (3) and formula (4), the thickness of the anti-seepage supporting layer and the permeability coefficient that meet the seepage control requirements can be obtained, and the larger value is taken for the thickness of the anti-seepage supporting layer.

[0075] Step 2. The depth of the semi-enclosed anti-seepage wall into the anti-seepage supporting layer;

[0076] like Figure 1 As shown in the figure, in order for the semi-enclosed anti-seepage wall to play a reliable anti-seepage role, the equivalent seepage diameter from B→C→D→E must be larger than the equivalent seepage diameter from B→E ( Figure 1 ), if the permeability coefficient k1 of the shallow permeable layer is used as the conversion basis for the equivalent seepage path length, the requirements are:

[0077]

[0078] Right now:

[0079]

[0080] Where: t is the depth of the semi-enclosed anti-seepage wall entering the relatively weak permeable layer; according to formula (6), the depth of the anti-seepage wall that meets the seepage control requirements entering the anti-seepage supporting layer can be calculated.

[0081] Step 3. Determine the layout range of the semi-enclosed anti-seepage wall to avoid damage caused by bypass seepage;

[0082] like Figure 2 As shown in the figure, assuming that points A, B, D, and E are all located in the shallow permeable layer, if seepage damage occurs at point C somewhere on the ground behind the embankment, how long should the section of the anti-seepage wall extend along the embankment line on both sides to avoid bypass seepage damage? In principle, the equivalent seepage path from A→B→C should be smaller than the equivalent seepage path from A→E→D→C. If the permeability coefficient k1 of the shallow permeable layer is used as the conversion basis for the equivalent seepage path length, the requirement is:

[0083]

[0084] Where: b is the distance from the danger point to the downstream side of the cut-off wall, and W is the extension length of the cut-off wall on both sides along the embankment line. The minimum value of the extension length W can be calculated according to formula (7).

[0085] It should be understood that the specific order or hierarchy of steps in the process disclosed by the present invention is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of protection of the present disclosure. The attached method claims provide the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0086] The present invention also provides a semi-closed anti-seepage system for embankment foundation, comprising the following modules:

[0087] The dike base layer module is used to determine that the surface layer is a shallow aquitard, the second layer is a relatively weak aquitard, and the layer below the second layer is a deep aquitard;

[0088] The anti-seepage support layer module is used to use the relatively weak permeable layer as a reliable anti-seepage support layer. To determine the thickness and permeability coefficient of the anti-seepage support layer, two conditions must be met:

[0089] (1) The equivalent seepage path from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is greater than the equivalent seepage path from the upstream side of the shallow aquitard through the semi-enclosed anti-seepage wall to the same position on the surface of the downstream side of the shallow aquitard;

[0090] (2) The vertical gradient from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is less than the hydraulic gradient allowed by the shallow aquitard;

[0091] The module of entry depth into the anti-seepage supporting layer is used to determine the depth of the semi-enclosed anti-seepage wall entering the anti-seepage supporting layer. The equivalent seepage path from the bottom of the shallow permeable layer to the relatively weak permeable layer and then back to the bottom of the shallow permeable layer must be greater than the equivalent seepage path from the shallow permeable layer through the semi-enclosed anti-seepage wall.

[0092] The cut-off wall layout module is used to determine the layout range of the semi-closed cut-off wall to avoid seepage damage. That is, if seepage damage occurs somewhere on the ground behind the embankment, the extension length of this section of the cut-off wall on both sides along the axial direction of the embankment must be determined to ensure that the equivalent seepage path from the shallow permeable layer through the semi-closed cut-off wall directly to the seepage damage point is smaller than the equivalent seepage path from the shallow permeable layer to the end of the extension length of the semi-closed cut-off wall and then to the seepage damage point.

[0093] The present invention is further described as follows with reference to specific embodiments:

[0094] like Figure 3 As shown in the figure, the height of a levee is 7.0m, the width of the levee crest is 6.0m, and the inner and outer slope ratios are 1:2.5 and 1:3.0 respectively. The width of the levee bottom is 44.5m ( Figure 3 ), the upstream and downstream head difference H = 5m. The surface layer of the embankment foundation is fine sand, that is, a shallow permeable layer, and the permeability coefficient of the shallow permeable layer is k1 = 1×10 -3cm / s, thickness h1 = 5m, allowable hydraulic gradient J G =0.5; below it is silty clay, i.e., a relatively weak aquitard, and the permeability coefficient of the relatively weak aquitard k2 = 1×10 -5 cm / s, thickness h2 = 5m; below the silty clay is thick gravel, i.e. deep permeable layer. The permeability coefficient of semi-enclosed anti-seepage wall k3 = 1×10 -6 cm / s, thickness d = 0.2m, length L = 20m from the inner foot of the embankment. During the flood season, seepage deformation occurs behind the embankment, and the distance from the danger point C to the downstream side of the anti-seepage wall is b = 50m (reference Figure 2 ). Determine whether the silty clay layer can be used as an anti-seepage support layer and determine the layout range of the semi-enclosed anti-seepage wall along the embankment line.

[0095] (1) When silty clay is used as the anti-seepage support layer, its thickness h2 is required to be no less than 2.15 m according to formula (3), and its thickness h2 is required to be no less than 0.05 m according to formula (4). The comprehensive value is h2 = 2.15 m. Since the silty clay layer is 5 m thick, this layer can be used as a reliable anti-seepage support layer.

[0096] (2) According to formula (6), the depth t of the semi-enclosed anti-seepage wall entering the relatively weak permeable layer (silty clay layer) is required to be greater than 0.9 m.

[0097] (3) In order to avoid seepage damage, according to formula (7), the anti-seepage wall should be extended by about 120 m along the embankment line on both sides of AB.

[0098] The invention enables the semi-closed anti-seepage wall and the anti-seepage supporting layer to form a complete anti-seepage system, thereby ensuring the accuracy of the design of the semi-closed anti-seepage wall. It can provide theoretical and technical support for the design of semi-closed anti-seepage walls in the embankment engineering design specifications, and has important theoretical and engineering practical significance for promoting the in-depth development of semi-closed anti-seepage wall technology.

[0099] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A semi-closed anti-seepage method for embankment foundation, characterized in that: The following steps are included: Assume that the embankment is impermeable, the surface layer of the embankment base is a shallow permeable layer, the second layer is a relatively weak permeable layer, and the layer below the second layer is a deep permeable layer; Taking the relatively weak permeable layer as the anti-seepage support layer, determining the thickness and permeability coefficient of the anti-seepage support layer requires two conditions to be met: (1) The equivalent seepage path from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is greater than the equivalent seepage path from the upstream side of the shallow aquitard through the semi-enclosed anti-seepage wall to the same position on the surface of the downstream side of the shallow aquitard; (2) The vertical gradient from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is less than the hydraulic gradient allowed by the shallow aquitard; To determine the depth of the semi-enclosed anti-seepage wall into the anti-seepage supporting layer, it is necessary to meet the requirement that the equivalent seepage path from the bottom of the shallow permeable layer to the relatively weak permeable layer and then back to the bottom of the shallow permeable layer is greater than the equivalent seepage path from the shallow permeable layer through the semi-enclosed anti-seepage wall; Determine the layout range of the semi-closed anti-seepage wall to avoid bypass seepage damage. That is, if seepage damage occurs somewhere on the ground behind the embankment, determine the extension length of this section of the anti-seepage wall on both sides along the embankment line. The equivalent seepage path from the shallow permeable layer through the semi-closed anti-seepage wall directly to the seepage damage point must be smaller than the equivalent seepage path from the shallow permeable layer bypassing the semi-closed anti-seepage wall to the end of the extension length to the seepage damage point.

2. A semi-closed anti-seepage method for embankment foundation according to claim 1, characterized in that: To determine the thickness and permeability coefficient of the anti-seepage support layer, the two conditions that need to be met are: Taking the permeability coefficient k1 of the shallow permeable layer as the conversion basis for the equivalent seepage path length, then: Right now: Where: k1 is the permeability coefficient of the shallow aquitard, k2 is the permeability coefficient of the relatively weak permeable layer, k3 is the permeability coefficient of the semi-enclosed anti-seepage wall, h1 is the thickness of the shallow permeable layer, h2 is the thickness of the relatively weak permeable layer, d is the thickness of the semi-enclosed anti-seepage wall, L is the length of the semi-enclosed anti-seepage wall from the inner foot of the embankment, H is the head difference between upstream and downstream, J G The hydraulic gradient allowed for the shallow aquitard; According to formula (3) and formula (4), the thickness of the anti-seepage supporting layer and the permeability coefficient that meet the seepage control requirements can be obtained, and the larger value is taken for the thickness of the anti-seepage supporting layer.

3. A semi-closed anti-seepage method for embankment foundation according to claim 1, characterized in that: Determine the depth of the semi-enclosed anti-seepage wall into the anti-seepage supporting layer, and the specific conditions are: Taking the permeability coefficient k1 of the shallow permeable layer as the conversion basis for the equivalent seepage path length, then: Right now: Where: t is the depth of the semi-enclosed anti-seepage wall entering the relatively weak permeable layer; according to formula (6), the depth of the anti-seepage wall that meets the seepage control requirements entering the anti-seepage supporting layer can be calculated.

4. A semi-closed anti-seepage method for embankment foundation according to claim 1, characterized in that: Determine the layout range of the semi-enclosed anti-seepage wall to avoid bypass seepage damage, as follows: Taking the permeability coefficient k1 of the shallow permeable layer as the conversion basis for the equivalent seepage path length, then: Where: b is the distance from the danger point to the downstream side of the cut-off wall, and W is the extension length of the cut-off wall along the embankment line. The minimum value of the extension length W can be calculated according to formula (7).

5. A semi-closed anti-seepage system for dike foundation, characterized by: Includes the following modules, The dike base layer module is used to determine that the surface layer is a shallow aquitard, the second layer is a relatively weak aquitard, and the layer below the second layer is a deep aquitard; The anti-seepage support layer module is used to use the relatively weak permeable layer as a reliable anti-seepage support layer. To determine the thickness and permeability coefficient of the anti-seepage support layer, two conditions must be met: (1) The equivalent seepage path from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is greater than the equivalent seepage path from the upstream side of the shallow aquitard through the semi-enclosed anti-seepage wall to the same position on the surface of the downstream side of the shallow aquitard; (2) The vertical gradient from the bottom of the relatively weak aquitard to the surface of the shallow aquitard is less than the hydraulic gradient allowed by the shallow aquitard; The module of entry depth into the anti-seepage supporting layer is used to determine the depth of the semi-enclosed anti-seepage wall entering the anti-seepage supporting layer. The equivalent seepage path from the bottom of the shallow permeable layer to the relatively weak permeable layer and then back to the bottom of the shallow permeable layer must be greater than the equivalent seepage path from the shallow permeable layer through the semi-enclosed anti-seepage wall. The cut-off wall layout module is used to determine the layout range of the semi-closed cut-off wall to avoid seepage damage. That is, if seepage damage occurs somewhere on the ground behind the embankment, the extension length of this section of the cut-off wall on both sides along the axial direction of the embankment must be determined to ensure that the equivalent seepage path from the shallow permeable layer through the semi-closed cut-off wall directly to the seepage damage point is smaller than the equivalent seepage path from the shallow permeable layer to the end of the extension length of the semi-closed cut-off wall and then to the seepage damage point.

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