Hydraulic engineering mold bag sand cofferdam and construction method thereof

Abstract

The invention relates to the technical field of mold bag sand cofferdam structures, in particular to a hydraulic engineering mold bag sand cofferdam and a construction method thereof. The hydraulic engineering mold bag sand cofferdam comprises sand bags which are stacked layer by layer from bottom to top, a sand cushion layer is arranged below the lowest sand bag, and a plurality of plastic drainage plates are arranged below the sand cushion layer. A steel frame structure is arranged on the lowermost sand bag in a penetrating mode, an anchor rod is connected to the lower portion of the steel frame structure, and the anchor rod is vertically arranged and inserted into a foundation. The steel frame structure is used for reducing the tension deformation of the bottommost sand bag, the steel frame structure is fixed through the anchor rods, finally, the structural stability of the whole mold bag sand cofferdam is ensured, a through sliding damage surface is prevented from being formed, and the safety coefficient of the whole mold bag sand cofferdam is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of the structure of the sand bag dike, in particular to a water conservancy project sand bag dike and a construction method thereof. BACKGROUND

[0002] In the area close to the offshore, the method of building a dike to fill and reclamation is generally used to reclaim land from the sea. The coastal area is usually soft ground, and the thick silt soft soil layer is difficult to handle. Under the condition of soft ground, the safety and reliability of the dike is not high, and the construction is difficult.

[0003] In order to solve the problem of building a dike on soft ground, which has poor overall stability, uneven settlement, and easy to slip, people began to use the structure of the sand bag dike. The sand bag is a kind of geosynthetic material bag, which is made of polymeric fiber fabric and has a woven bag structure. The fabric has good water permeability and soil retention. The sand bag dike is a temporary water retaining structure commonly used in water conservancy projects. It is a kind of temporary water retaining structure commonly used in water conservancy projects, which has the characteristics of simple construction and low cost.

[0004] However, the construction of the sand bag dike still mainly relies on experience, which leads to the fact that the overall stability of some dike structures cannot meet the design requirements. The main failure mode of the sand bag dike on soft ground is that the soft ground is subjected to the weight of the sand bag and the external environmental wave force during the construction of the dike, which causes plastic deformation and uneven tensile deformation of the bottom sand bag of the dike, resulting in the breaking of the bottom sand bag of the dike, which further affects the upper sand bag and forms a chain effect. The sand bag of the dike is pulled apart from bottom to top, forming a through sliding failure surface. This model seriously affects the overall structural stability of the dike structure.

[0005] Therefore, the overall stability design of the dike structure needs to be further studied. SUMMARY

[0006] In order to solve the above technical problems in the prior art, the present application provides a water conservancy project sand bag dike and a construction method thereof, which improves the overall stability and safety and reliability of the dike structure.

[0007] To achieve the above purpose, the technical scheme of the present application is as follows:

[0008] In a first aspect, the present application provides a water conservancy project sand bag dike, which comprises sand bags stacked layer by layer from bottom to top. A sand cushion layer is arranged below the lowermost sand bag, and a plurality of plastic drainage boards are arranged below the sand cushion layer. A steel frame structure is arranged through the lowermost sand bag, and an anchor rod is connected below the steel frame structure. The anchor rod is vertically arranged and inserted into the foundation.

[0009] Further, the steel frame structure is welded by steel pipes, and the steel pipes have a spacing between adjacent steel pipes, thereby forming a hollow steel frame structure.

[0010] Further, the spacing B between adjacent steel pipes is:

[0011] B=f(b,D)

[0012] wherein b represents the width of the lowermost sand bag, D represents the thickness of the lowermost sand bag, and f represents the mapping relationship between B, b and D.

[0013] The mapping relationship f between B, b and D is determined in the following manner:

[0014] A simulation model of a water conservancy project bagged sand cofferdam is established, a single variable, the width b of the lowermost sand bag, is taken as an independent variable, the spacing B between steel pipes is taken as a dependent variable, the tensile deformation of the lowermost sand bag in the simulation model of the water conservancy project bagged sand cofferdam meets the design requirements as a target, the relationship between the spacing B between steel pipes and the width b of the lowermost sand bag is determined, and is denoted as:

[0015] B=f1(b)

[0016] The thickness D of the lowermost sand bag is taken as an independent variable, the spacing B between steel pipes is taken as a dependent variable, the tensile deformation of the lowermost sand bag in the simulation model of the water conservancy project bagged sand cofferdam meets the design requirements as a target, the relationship between the spacing B between steel pipes and the width b of the lowermost sand bag is determined, and is denoted as:

[0017] B=f2(D)

[0018] The mapping relationship f between B, b and D is finally:

[0019] B=αf1(b)+βf2(D)

[0020] wherein α and β are weight coefficients, and α+β=1.

[0021] Further, the determination method of the weight coefficients α and β is as follows: a target function is determined:

[0022]

[0023] wherein B i =(B1,B2…B n ), B1 is the minimum value in f1(b) and f2(D), B n is the maximum value in f1(b) and f2(D), the difference between B i and B i-1 is 0.1B1, and the difference between B n and B n-1 is less than or equal to 0.1B1.

[0024] The alpha and beta at the minimum of the objective function are the optimal weight coefficients.

[0025] Further, the length L of the steel frame structure covering the lowermost sand bag is 0.3 to 0.5 times the length of the lowermost sand bag.

[0026] Further, the sand cushion layer is provided with a geotextile tube bag.

[0027] Further, the lowermost sand bag is made of high-strength geotextile, and the ultimate tensile strength of the high-strength geotextile is greater than 55KN / m.

[0028] Further, the lowermost sand bag is wrapped with geogrid at both ends, and the geogrid is connected with the steel frame structure.

[0029] In a second aspect, the present application also provides a construction method of the water conservancy project bagged sand cofferdam, comprising:

[0030] S1, constructing a geotextile tube bag;

[0031] S2, filling the sand cushion layer underwater;

[0032] S3, inserting plastic drainage boards and anchor rods;

[0033] S4, erecting a steel frame structure, connecting the steel frame structure with the anchor rods, and laying geogrid according to the size of the sand bag;

[0034] S5, laying and filling the geotextile of the lowermost sand bag;

[0035] S6, wrapping the geogrid around both ends of the lowermost sand bag, and connecting the geogrid with the steel frame structure;

[0036] S7, laying multiple layers of sand bags above the lowermost sand bag and filling them layer by layer.

[0037] Further, during the filling of the lowermost sand bag, the filling height of the sand bag is monitored in real time, and the filling pressure is adjusted according to the filling height, specifically:

[0038] When the filling height is less than 0.4 times the set elevation of the sand bag, the filling pressure is 0.2MPa-0.25MPa;

[0039] When the filling height is greater than 0.4 times the set elevation of the sand bag, the filling pressure is 0.25MPa-0.3MPa.

[0040] Further, a first threshold value and a second threshold value of the filling height are set, the first threshold value is less than the second threshold value; when the filling height is greater than the first threshold value, the vibration is started, and the vibration speed is gradually increased; when the filling height is greater than the second threshold value, the filling pressure is reduced, the vibration speed is maintained, and the filling is completed.

[0041] Further, the filling height is set to be more than 0.4 times of the set elevation, and the filling pressure P is:

[0042]

[0043] Wherein, h is an index related to real-time filling height, V is the vibration speed, R is the water content of the filling material, and A is a constant, taking a value of 10 to 15.

[0044] Further, when the filling height is between 0.4-0.5 times of the set elevation, h takes a value of 0.01;

[0045] When the filling height is between 0.5-0.8 times of the set elevation, h takes a value of 0.011;

[0046] When the filling height is more than 0.8 times of the set elevation, h takes a value of 0.008.

[0047] Further, when the filling pressure of the lowermost sand bag reaches 0.3MPa, the corresponding filling height P1 at this time is obtained, if the filling height P1 is less than the second threshold, the span of the adjacent sand bag above the lowermost sand bag is reduced, and the reduction amount W is determined according to the difference between the filling height P1 and the set elevation.

[0048] Compared with the prior art, the present application has the following beneficial effects:

[0049] The water conservancy project bagged sand cofferdam and the construction method thereof provided by the present application pass through the steel frame structure arranged on the lowermost sand bag, the steel frame structure is connected with the anchor rod below, and the anchor rod is vertically arranged and inserted into the foundation. The steel frame structure is used to reduce the tensile deformation of the lowermost sand bag, so that the tensile deformation amount meets the requirements, the anchor rod is used to fix the steel frame structure, and finally the structural stability of the whole bagged sand cofferdam is ensured, the sliding damage surface is avoided, and the safety factor of the whole bagged sand cofferdam is improved.

[0050] The size of the steel frame structure is determined by multiple single variables respectively in the present application, the calculation amount is reduced, then the final optimal steel frame structure size is obtained by comprehensively considering the steel frame structure sizes obtained by multiple single variables, so that the steel frame structure meets the requirements, the amount of steel used by the steel frame structure is reduced, and the construction cost is reduced. DETAILED DESCRIPTION

[0051] Figure 1 The water conservancy project bagged sand cofferdam structure provided by the present application is shown in the schematic view.

[0052] Figure 2 The structure of the steel frame structure is shown in the schematic view.

[0053] Explanation of the accompanying numbers: 1. The bottom sand bag, 2. The sand cushion layer, 3. The plastic drainage board, 4. The steel frame structure, 5. The anchor rod, 6. The geotube bag twist stop. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be clearly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0055] It should be noted that, unless otherwise specifically stated, the relative arrangements of components and steps, and numerical expressions set forth in these embodiments should not be construed as limiting the scope of the present invention.

[0056] The following description of exemplary embodiments is merely illustrative and is not intended to limit the present invention, its application, or use in any sense. Technologies, methods, and apparatus known to those skilled in the art may not be discussed in detail herein, but to the extent applicable, such technologies, methods, and apparatuses should be considered part of this specification.

[0057] Example 1

[0058] This embodiment provides a water conservancy project mold bag sand cofferdam, such as Figure 1 As shown, the structure comprises sandbags stacked layer by layer from bottom to top, with each layer increasing in thickness proportionally from bottom to top. A sand cushion layer 2 is provided beneath the bottom sandbag 1, and several plastic drainage boards 3 are provided beneath the sand cushion layer 2. A steel frame structure 4 is placed above the bottom sandbag 1, and anchor rods 5 are connected to the bottom of the steel frame 4. The anchor rods 5 are vertically installed and inserted into the foundation.

[0059] like Figure 2 As shown, the steel frame structure 4 is made of welded steel pipes, with spacing between adjacent steel pipes, forming a hollow steel frame structure 4. The spacing B between adjacent steel pipes is:

[0060] B=f(b,D)

[0061] Wherein, b represents the width of the bottom sand bag 1, D represents the thickness of the bottom sand bag 1, and f represents the mapping relationship between B and b and D;

[0062] In this embodiment, the spacing B is Figure 2 The spacing between adjacent steel pipes in the left and right directions and the spacing between adjacent steel pipes in the front and back directions are shown in the figure. The spacing between adjacent steel pipes in the top and bottom directions is determined by the thickness of the lowest sandbag.

[0063] The mapping relationship f between B, b, and D is determined as follows:

[0064] A water conservancy project bagged sand cofferdam simulation model is established, a single variable, the width b of the lowermost sand bag, is taken as the independent variable, the steel pipe spacing B is taken as the dependent variable, the tension deformation of the lowermost sand bag 1 in the water conservancy project bagged sand cofferdam simulation model meets the design requirements as the target, the relationship between the steel pipe spacing B and the width b of the lowermost sand bag is determined, which is recorded as:

[0065] B=f1(b)

[0066] The thickness D of the lowermost sand bag 1 is taken as the independent variable, the steel pipe spacing B is taken as the dependent variable, the tension deformation of the lowermost sand bag 1 in the water conservancy project bagged sand cofferdam simulation model meets the design requirements as the target, the relationship between the steel pipe spacing B and the width b of the lowermost sand bag 1 is determined, which is recorded as:

[0067] B=f2(D)

[0068] The mapping relationship f of B, b and D is:

[0069] B=αf1(b)+βf2(D)

[0070] Wherein, α and β are weight coefficients, α+β=1.

[0071] Wherein, the determination method of the weight coefficients α and β is to determine the objective function:

[0072]

[0073] Wherein, B i =(B1,B2…B n ), B1 is the minimum value of f1(b) and f2(D), B n is the maximum value of f1(b) and f2(D), the difference between B i and B i-1 is 0.1B1, and the difference between B n and B n-1 is less than or equal to 0.1B1;

[0074] The α and β at the minimum value of the objective function are the most weight coefficients.

[0075] In order to simplify the iteration process of the objective function, discrete point values can be used for iteration, that is, α is sequentially brought into the objective function according to the order of 0.05, 0.1, 0.15…1, and the corresponding β is calculated according to α+β=1, and is also brought into the objective function, all L(α,β) are calculated, the minimum value is selected from all values, and the α and β corresponding to the minimum value are the most weight coefficients.

[0076] The length L of the steel frame structure 4 covering the lowermost sand bag 1 is 0.3 to 0.5 times the length of the lowermost sand bag 1.

[0077] In addition, the sand cushion layer 2 is provided with a geotextile tube 6. The lowermost sand bag 1 is made of high-strength geotextile, and the ultimate tensile strength of the high-strength geotextile is greater than 55KN / m.

[0078] The lowermost sand bag 1 is provided with geogrids at both ends, and the geogrids are connected with the steel frame structure 4, so as to enhance the stability of the overall structure.

[0079] Embodiment two

[0080] The embodiment also provides a construction method of the water conservancy project bagged sand cofferdam, comprising the following steps:

[0081] S1, constructing the geotextile tube 6;

[0082] According to the positioning of the sand cushion layer 2 area, the geotextile tube 6 is constructed along the length direction of the cofferdam outside the sand cushion layer 2, so as to form a surrounding structure of the sand cushion layer 2.

[0083] S2, throwing and filling the sand cushion layer 2 underwater;

[0084] The belt sand ship is used for coarse throwing and material transportation, and the flat barge and the excavator arranged on the ship are used for fine flat filling. In the process of throwing and filling, the influence of water sinking and the like is fully considered, so as to ensure the accuracy of the sand material falling point and the continuity and uniformity of the sand cushion layer 2.

[0085] S3, inserting the plastic drainage plate 3 and the anchor rod 5;

[0086] The plastic drainage plate 3 is constructed according to the set section, and the set section is usually 200m-300m. The insertion depth of the plastic drainage plate 3 is ensured in the construction process.

[0087] Then, the anchor rod 5 is constructed.

[0088] S4, erecting the steel frame structure 4, connecting the steel frame structure 4 with the anchor rod 5, and laying the geogrid according to the sand bag size;

[0089] The steel frame structure 4 is pre-welded according to the size of the steel frame structure 4, and then the steel frame structure 4 is erected and connected with the anchor rod 5.

[0090] The geogrid is laid by the construction ship, and the direction with large tensile strength of the geogrid is along the transverse direction of the dam. After the laying of the geogrid, it is ensured that there is no wrinkle.

[0091] S5, laying and filling the geotextile of the lowermost sand bag 1;

[0092] The sand bag construction is constructed by the sand ship, and the sand soil is filled. The particle size of the sand soil is configured according to the construction requirements.

[0093] S6, the geogrid is wrapped around the two ends of the lowermost sand bag 1, and the geogrid is connected with the steel frame structure 4; the geogrid and the steel frame structure 4 are connected as much as possible, and at least the actual connection is more than 85% of the full connection length.

[0094] S7, multiple layers of sand bags are laid above the lowermost sand bag 1 and filled layer by layer.

[0095] Among them, during the filling process of the lowermost sand bag 1, the filling height of the sand bag is monitored in real time, and the filling pressure is adjusted according to the filling height, specifically:

[0096] The filling height is 0.4 times the set elevation of the sand bag, and the filling pressure is 0.2-0.25 MPa;

[0097] The filling height is more than 0.4 times the set elevation of the sand bag, and the filling pressure is 0.25-0.3 MPa.

[0098] The first threshold and the second threshold of the set filling height are set, and the first threshold is less than the second threshold; when the filling height is greater than the first threshold, the vibration is started, and the vibration speed is gradually increased; when the filling height is greater than the second threshold, the filling pressure is reduced, and the vibration speed is maintained until the filling is completed.

[0099] The filling height is more than 0.4 times the set elevation of the sand bag, and the filling pressure P is:

[0100]

[0101] Wherein, h is an index related to the real-time filling height, V is the vibration speed, R is the water content of the filling material, and A is a constant, taking a value of 10 to 15.

[0102] Wherein, the determination method of h value is:

[0103] When the filling height is between 0.4-0.5 times the set elevation, h takes a value of 0.01;

[0104] When the filling height is between 0.5-0.8 times the set elevation, h takes a value of 0.011;

[0105] When the filling height is more than 0.8 times the set elevation, h takes a value of 0.008.

[0106] In addition, when the filling pressure of the lowermost sand bag reaches 0.3 MPa, the corresponding filling height P1 at this time is obtained, if the filling height P1 is less than the second threshold, the span of the adjacent sand bag above the lowermost sand bag is reduced, and the reduction amount W is determined according to the difference between the filling height P1 and the set elevation.

[0107] The above detailed description merely illustrates the technical solutions of the present application and is not limiting, and although the present application has been described in detail with reference to the examples, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or equivalently replaced without departing from the scope of the technical solutions of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A water conservancy project sand bag cofferdam, comprising sand bags stacked layer by layer from bottom to top, characterized in that: A sand cushion layer is set below the lowest sand bag, and a number of plastic drainage boards are set below the sand cushion layer; a steel frame structure is passed through the lowest sand bag, and anchor rods are connected below the steel frame structure. The anchor rods are vertically arranged and inserted into the foundation.

2. The water conservancy project mold bag sand cofferdam according to claim 1, characterized in that: The steel frame structure is formed by welding steel pipes, and there is a gap between adjacent steel pipes to form a hollow steel frame structure.

3. The water conservancy project mold bag sand cofferdam according to claim 2, characterized in that: The spacing B between adjacent steel pipes is: B=f(b,D) Where b represents the width of the lowest sand bag, D represents the thickness of the lowest sand bag, and f represents the mapping relationship between B and b and D. The mapping relationship f between B, b, and D is determined as follows: A simulation model of sand-bag cofferdams for water conservancy projects was established. The width b of the lowest sand bag was used as the independent variable, and the spacing between steel pipes B was used as the dependent variable. The goal was to ensure that the tensile deformation of the lowest sand bag in the simulation model of sand-bag cofferdams for water conservancy projects met the design requirements. The relationship between the spacing between steel pipes B and the width b of the lowest sand bag was determined and expressed as: B=f1(b) Taking the thickness D of the lowest sand bag as the independent variable and the steel pipe spacing B as the dependent variable, and aiming at ensuring that the tensile deformation of the lowest sand bag in the simulation model of the sand cofferdam in a hydraulic engineering project meets the design requirements, the relationship between the steel pipe spacing B and the width b of the lowest sand bag is determined, which can be expressed as: B=f2(D) The final mapping relationship f between B, b and D is: B=αf1(b)+βf2(D) Among them, α and β are weight coefficients, α+β=1.

4. The water conservancy project bag sand cofferdam according to claim 3, characterized in that: The method for determining the weight coefficients α and β is: Determine the objective function: Among them, B i =(B1, B2…B n ), B1 is the minimum value between f1(b) and f2(D), B n is the maximum value between f1(b) and f2(D), B i With B i-1 The difference is 0.1B1, and B n With B n-1 The difference is less than or equal to 0.1B1; The α and β when the objective function is minimized are the final weight coefficients.

5. The water conservancy project mold bag sand cofferdam according to claim 2, characterized in that: Both ends of the lowest sandbag are covered with geogrids, and the geogrids are connected to the steel frame structure.

6. The construction method of a sand bag cofferdam for a water conservancy project according to any one of claims 1 to 5, characterized in that: include: S1, construction geotube bag twisting; S2, underwater sand filling cushion; S3. Insert plastic drainage boards and anchor rods; S4. Erect the steel frame structure, connect the steel frame structure with the anchor rods, and lay the geogrid according to the set size of the sandbags; S5. Laying and filling the geotextile of the bottom sand bag; S6. Wrap the geogrid around the two ends of the bottom sandbag and connect the geogrid to the steel frame structure; S7. Lay multiple layers of sandbags on top of the bottom sandbag and fill them layer by layer.

7. The construction method according to claim 6, characterized in that: During the filling process of the bottom sand bag, the filling height of the sand bag is monitored in real time, and the filling pressure is adjusted according to the filling height. Specifically: The filling height is less than 0.4 times the set height of the sand bag, and the filling pressure is 0.2MPa-0.25MPa; The filling height is more than 0.4 times the set elevation of the sandbag, and the filling pressure is 0.25MPa-0.3MPa.

8. The construction method according to claim 7, characterized in that: A first threshold and a second threshold of the filling height are set, wherein the first threshold is smaller than the second threshold; when the filling height is greater than the first threshold, vibration is started and the vibration speed is gradually increased; when the filling height is greater than the second threshold, the filling pressure is reduced and the vibration speed is maintained until the filling is completed.

9. The construction method according to claim 8, characterized in that: The filling height is at least 0.4 times the set height of the sandbag, and the filling pressure P is: Where h is an index related to the real-time filling height, V is the vibration speed, R is the water content of the filling material, and A is a constant with a value of 10 to 15.

10. The construction method according to claim 9, characterized in that: When the filling height is between 0.4 and 0.5 times the set elevation, h takes the value of 0.01; When the filling height is between 0.5 and 0.8 times the set elevation, h takes the value of 0.011; When the filling height is above 0.8 times the set elevation, h takes the value of 0.008; When the filling pressure of the bottom sandbag reaches 0.3 MPa, the corresponding filling height P1 is obtained. If the filling height P1 is less than the second threshold, the span of the adjacent sandbags above the bottom sandbag is reduced. The reduction amount W is determined by the difference between the filling height P1 and the set elevation.

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