Performance calculation method for double-row steel sheet pile sandwich gravity type retaining wall supporting structure

Abstract

The invention discloses a performance calculation method for a double-row steel sheet pile sandwich gravity type retaining wall supporting structure, which utilizes the unique performance of each component of the double-row steel sheet pile sandwich gravity type retaining wall supporting structure. Reasonable mechanical simplified model construction is conducted according to the integrality that all the components have relative independence and organic combination, and the collaborative contribution of the double-row steel sheet piles and the sandwich gravity type retaining wall is quantitatively fused. The calculation method fills the blank of lack of evaluation methods, fits the actual situation of the composite system, correctly evaluates the actual working performance of the support system, improves the safety coefficient, and can save the project amount when being properly applied.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, and in particular to a performance calculation method for a double-row steel sheet pile sandwich gravity retaining wall support structure. Background Technology

[0002] To enhance the support capacity of single-row sheet piles, double-row sheet pile support structures have emerged in recent years. This involves adding a second row of sheet piles on the side of the single row furthest from the foundation pit, connecting the two rows with tie rods to improve the lateral resistance of the single row. Even so, double-row sheet piles still suffer from drawbacks such as insufficient structural compactness and slightly inadequate overall rigidity. Cement-mixed pile gravity retaining wall structures offer advantages such as large cross-sections and the ability to utilize their own weight to create a certain retaining capacity. However, they suffer from insufficient integrity of the cement-soil structure, low shear strength, and susceptibility to cracking. From a technical perspective, these two support structures are highly complementary, and theoretically, combining them can overcome each other's shortcomings.

[0003] However, the collaborative operation of composite support systems formed by these two types of structures involves complex mechanical problems such as soil-structure interaction, deformation coordination and matching, and load distribution. Current national standards for foundation pit support design methods are all theoretical systems and calculation models built for single structural forms, and their core theoretical foundations cannot be directly transferred to this type of composite support structure. Due to the lack of suitable theoretical calculation basis, the actual support performance of this composite support system cannot be correctly evaluated, resulting in insufficient promotion and application of this type of composite support structure, and leading to engineering waste or accident risks. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a performance calculation method for double-row steel sheet pile sandwich gravity retaining wall support structures, primarily solving the problem of the lack of corresponding performance evaluation methods for existing double-row steel sheet pile sandwich gravity retaining walls.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A performance calculation method for a double-row steel sheet pile sandwich gravity retaining wall support structure includes the following steps:

[0007] A simplified mechanical model of a double-row steel sheet pile sandwich gravity retaining wall support structure is constructed. All parameters in the simplified mechanical model are derived from the conventional geotechnical mechanics parameters involved in the specific engineering project. The simplified mechanical model includes a simplified mechanical model of overall stability, a simplified mechanical model of resistance to horizontal sliding stability, a simplified mechanical model of resistance to overturning stability, and a simplified mechanical model of displacement calculation.

[0008] The contribution of the shear strength of the double-row steel sheet piles to the overall stability of the support structure is incorporated into the simplified mechanical model of overall stability, and the overall stability safety factor is calculated.

[0009] The contribution of the shear strength of the double-row steel sheet piles to the slip stability of the support structure is incorporated into the simplified mechanical model of horizontal slip stability, and the slip stability safety factor is calculated.

[0010] The frictional force between the rear steel sheet piles and the soil below the bottom of the core wall is incorporated into the simplified mechanical model of overturning stability to calculate the overturning stability safety factor.

[0011] Based on the simplified mechanical model for displacement calculation, the active earth pressure borne by the sheet pile is distributed according to the stiffness principle, and the displacement of the sheet pile is calculated using the m-method, which is regarded as the displacement of a double-row sheet pile sandwich gravity retaining wall support structure.

[0012] The beneficial effects of this invention are as follows: This method utilizes the unique properties of each component of a double-row steel sheet pile sandwich gravity retaining wall support structure. By constructing a reasonable simplified mechanical model that addresses the overall characteristics of each component—both relatively independent and organically integrated—it quantifies and integrates the synergistic contributions of the double-row steel sheet piles and the sandwich gravity retaining wall. First, the shear strength of the steel sheet piles is converted into resisting moment, which is superimposed with the resisting moment of the core wall to improve the overall stability safety factor. Then, a dual-source logic of core wall anti-slip and steel sheet pile horizontal shear resistance is constructed to address the insufficiency of a single horizontal anti-slip source. Furthermore, the overturning moment of the frictional resistance between the steel sheet piles and the soil below the bottom of the core wall is incorporated to improve overturning safety performance. Finally, active earth pressure loads are distributed according to the stiffness principle, and the displacement of the simplified model is calculated using the m-method, which represents the displacement of the composite support structure. The above calculation method fills the gap in evaluation methods, closely aligns with the actual situation of composite systems, can accurately evaluate the actual working performance of the support system, improves the safety factor, and, when applied appropriately, can save on engineering work. Attached Figure Description

[0013] Figure 1a This is a front view of the double-row steel sheet pile sandwich gravity retaining wall support structure implemented according to step 1 of construction method two in this embodiment of the invention;

[0014] Figure 1b This is a top view of the double-row steel sheet pile sandwich gravity retaining wall support structure implemented according to step 1 of construction method two in this embodiment of the invention;

[0015] Figure 2a This is a front view of the double-row steel sheet pile sandwich gravity retaining wall support structure implemented according to step 2 of construction method 2 in this embodiment of the invention;

[0016] Figure 2bThis is a top view of the double-row steel sheet pile sandwich gravity retaining wall support structure implemented according to step 2 of construction method 2 in this embodiment of the invention;

[0017] Figure 3a This is a front view of the double-row steel sheet pile sandwich gravity retaining wall support structure implemented according to step 3 of construction method two in this embodiment of the invention;

[0018] Figure 3b This is a top view of the double-row steel sheet pile sandwich gravity retaining wall support structure implemented according to step 3 of construction method two in this embodiment of the invention;

[0019] Figure 4 This is a schematic diagram of a simplified model for load distribution and displacement calculation in an embodiment of the present invention;

[0020] Figure 5 This is a simplified model diagram of the overall stability analysis in an embodiment of the present invention;

[0021] Figure 6 This is a simplified model diagram of the anti-horizontal slip stability force analysis in an embodiment of the present invention;

[0022] Figure 7 This is a simplified model diagram of the anti-overturning stability analysis in an embodiment of the present invention;

[0023] Figure 8a This is a schematic diagram of displacement calculation and analysis in an embodiment of the present invention;

[0024] Figure 8b for Figure 8a middle A schematic diagram illustrating the physical meaning;

[0025] Figure 8c for Figure 8a middle A schematic diagram illustrating the physical meaning;

[0026] Figure 9 This is a schematic diagram of the overall stability analysis in an application example of the present invention without double-row steel sheet piles;

[0027] Figure 10 This is a schematic diagram of the overall stability analysis under the premise of setting double-row steel sheet piles in the application example of the present invention;

[0028] Figure 11 This is a schematic diagram of the anti-horizontal slip stability analysis in an application example of the present invention;

[0029] Figure 12 This is a schematic diagram of the anti-overturning stability analysis in an application example of the present invention;

[0030] Figure 13 This is a schematic diagram illustrating the analysis of a simplified mechanical model for displacement calculation in an application example of the present invention.

[0031] Figure 14 This is an example of the parameter settings for double-row steel sheet piles using the Lizheng Geotechnical Calculation Software, without the core wall being installed.

[0032] Figure 15 This is an example of the displacement results of double-row steel sheet piles using the Lizheng Geotechnical Calculation Software when no core wall is set in the application of this invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the content of this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to this invention are shown in the accompanying drawings, not all of them.

[0034] Example

[0035] This embodiment proposes a performance calculation method for a double-row steel sheet pile sandwich gravity retaining wall support structure, including the following steps:

[0036] Step 1: Construct a simplified mechanical model of the double-row steel sheet pile sandwich gravity retaining wall support structure. All parameters in the simplified mechanical model are derived from the conventional geotechnical mechanics parameters involved in the specific engineering project. The simplified mechanical model includes a simplified mechanical model of overall stability, a simplified mechanical model of horizontal slip resistance, a simplified mechanical model of overturning resistance, and a simplified mechanical model of displacement calculation.

[0037] The support structure is a composite support system, formed by a combination of double-row steel sheet piles and a gravity retaining wall. The gravity retaining wall serves as the core wall located between the double-row steel sheet piles, which are tightly connected to the middle gravity retaining wall via tie rods, working in synergy. The double-row steel sheet piles can be any of the following: double-row pipe piles, double-row micropiles, double-row steel pipe piles, or double-row bored piles. The gravity retaining wall is formed by high-pressure jet grouting, cement mixing, or by grouting to create a gravity-reinforced structure. The construction method for this composite support system includes two optional approaches:

[0038] Method 1: Step 1, first construct double-row steel sheet piles; Step 2, then construct a high-pressure jet grouting gravity retaining wall in the middle of the double-row steel sheet piles; Step 3, after the gravity retaining wall is constructed, open holes at the top of the double-row steel sheet piles, install connecting beams and tie rods, so that the tie rods pass through the holes, and set threads at both ends of the tie rods. Apply pre-force to the tie rods by tightening bolts until the double-row steel sheet piles and gravity retaining wall are tightly fitted together.

[0039] Method 2: Step 1, as follows Figure 1aand 1b As shown, first construct the cement mixing pile gravity retaining wall, step 2, as... Figure 2a and 2b As shown, construct double rows of steel sheet piles closely adjacent to the gravity retaining wall; Step 3, as... Figure 3a and 3b As shown, after the double-row sheet piles are constructed, holes are drilled at the top of the piles, and connecting beams and tie rods are installed. The tie rods pass through the holes, and both ends of the tie rods are threaded. Pre-force is applied to the tie rods by tightening bolts until the double-row sheet piles are tightly fitted to the gravity retaining wall. A simplified mechanical model is shown below. Figure 4 As shown.

[0040] Step 2: Incorporate the contribution of the shear strength of the double-row steel sheet piles to the overall stability of the support structure into the simplified mechanical model of overall stability, calculate the overall stability safety factor, and perform the overall stability analysis as follows: Figure 5 As shown.

[0041] The method for calculating the overall stability safety factor is as follows:

[0042] (1);

[0043] The contribution of double-row steel sheet piles to the overall stability safety factor is as follows:

[0044] (2);

[0045] In the formula, , These are the cohesion (kPa) and internal friction angle (°) of the soil at the slip surface of the j-th soil strip, respectively. Let be the pore water pressure (kPa) on the slip surface of the j-th soil strip; Let be the slip arc length (m) of the j-th soil strip, and take . ; Let be the width (m) of the j-th soil strip; The additional load (kN) for the j-th soil strip; The weight of the j-th soil strip is (kN / m). Let be the angle (°) between the normal at the midpoint of the j-th soil strip arc and the vertical plane. For overall stability and safety, its value should not be less than 1.3; The contribution of double-row steel sheet piles to the overall stability safety factor; The shear strength (kPa) of the double-row steel sheet piles. The shear cross-sectional area (m²) of the double-row steel sheet piles 2 ).

[0046] Step 3: Incorporate the contribution of the shear strength of the double-row sheet piles to the slip stability of the support structure into the simplified mechanical model of horizontal slip stability, calculate the slip stability safety factor, and perform the horizontal slip stability analysis as follows. Figure 6 As shown.

[0047] The method for calculating the slip stability safety factor is as follows:

[0048] (3);

[0049] The contribution of double-row steel sheet piles to the slip stability safety factor is as follows:

[0050] (4);

[0051] In the formula, The safety factor for slip stability should not be less than 1.2; The contribution of double-row steel sheet piles to the slip stability safety factor; The active earth pressure (kN) on the gravity retaining wall; The passive earth pressure (kN) on the gravity retaining wall; The self-weight of the gravity retaining wall (kN); The bottom width (m) of the gravity retaining wall; , The values ​​represent the cohesion (kPa) and internal friction angle (°) of the soil layer beneath the bottom of the gravity retaining wall.

[0052] Step 4: The frictional force between the rear sheet piles and the soil below the bottom of the core wall is incorporated into the simplified mechanical model of overturning stability. The overturning stability safety factor is calculated, and the overturning stability analysis is as follows: Figure 7 As shown.

[0053] The method for calculating the overturning stability safety factor is as follows:

[0054] (5);

[0055] The contribution of double-row steel sheet piles to slip stability is as follows:

[0056] (6);

[0057] In the formula, The overturning stability safety factor; Contribution to the safety factor of double-row steel sheet piles in resisting overturning stability; It is the vertical distance from the point of application of the resultant force of the passive earth pressure on the inner side of the gravity retaining wall to the toe of the wall; The vertical distance (m) from the point of application of the resultant force of the active earth pressure on the inner side of the gravity retaining wall to the toe of the wall. The horizontal distance (m) from the point of application of the resultant force of the self-weight of the inner side of the gravity retaining wall and the water pressure at the bottom of the wall to the toe of the wall. The frictional resistance (kPa) between the rear sheet piles and the soil. The width of the gravity retaining wall is in meters.

[0058] Step 5: Based on the simplified mechanical model for displacement calculation, the active earth pressure borne by the sheet piles is distributed according to the stiffness principle, and the displacement of the sheet piles is calculated using the m-method, which is regarded as the displacement of the double-row sheet pile sandwich gravity retaining wall support structure.

[0059] In the displacement calculation of the double-row steel sheet pile sandwich gravity retaining wall in this scheme, since the front and rear rows of steel sheet piles are prestressed through tie rods, the steel sheet piles and the core wall are tightly attached to form a structure with relatively large bending stiffness, and their displacements are equal, equivalent to a rigid node. Therefore, it is reasonable to assume that, under the coordinated action of the sandwich soil and tie rods, the active earth pressure load above the bottom of the foundation pit is borne by the front and rear rows of steel sheet piles according to their bending stiffness. Usually, the front and rear rows use the same steel sheet piles with the same bending stiffness, so the load is evenly distributed. 前 =q 后 ,like Figure 8a As shown, the load distribution pattern is the same as that of the active earth pressure. Therefore, the displacement of the sandwich gravity retaining wall can be calculated by treating the sheet piles above the bottom of the pit as cantilever piles and calculating the displacement of the front or rear sheet piles using the m-method. This displacement is considered as the displacement of the sandwich gravity retaining wall. Therefore, the premise for calculating the horizontal displacement is that the double rows of sheet piles are tightly connected to the core wall, and the displacements are the same. Then, according to the principle of rigid nodes, the front or rear sheet piles share the active earth pressure according to their own stiffness proportions. Based on the shared active earth pressure, the m-method is further used to calculate the sheet pile displacement.

[0060] (7);

[0061] (8);

[0062] (9);

[0063] (10);

[0064] In the formula, This represents the horizontal displacement (m) at the bottom of the pile foundation pit. The angle (°) at the bottom of the pile foundation pit; The displacement at the top of the pile is (m). The displacement (m) of the pile top caused by the elastic deflection of the pile above the pit bottom. The height of the ground at the bottom of the foundation pit (m); The earth pressure intensity (kN) experienced by the sheet pile.

[0065] The expressions appearing in equations (7)-(10) Its physical meaning is seen Figure 8b , Figure 8c ,according to Refer to Table L.0.8 of the "Specifications for Design of Highway Bridge and Culvert Foundations"; when At that time, according to calculate.

[0066] Application example:

[0067] This application example establishes a simplified mechanical model of a double-row steel sheet pile sandwich gravity retaining wall support structure according to the method provided in step 1 of the embodiment. Specifically, the pit depth is set to h = 5m, the spacing between the double rows of steel sheet piles is w = 2.5m, the length of the steel sheet piles is L = 15m, and the natural unit weight of the soil is... Cohesion internal friction angle The proportional coefficient of the horizontal resistance coefficient of the foundation The density of the sandwich gravity retaining wall is... Cohesion internal friction angle The sandwich gravity retaining wall is 5m high and the base friction coefficient is [missing value]. The shear strength of the sheet pile is 0.4. 215 N / mm 2 elastic modulus Projected shear area of ​​sheet pile flange It is 5029.75mm 2 Moment of inertia of cross section The frictional resistance between the rear piles and the soil The calculated width b1 = 1m is simplified to be unaffected by groundwater, pore water pressure, and external ground loads.

[0068] (1) Overall stability analysis and calculation of double-row steel sheet pile sandwich gravity retaining wall

[0069] If double-row sheet piles are not installed, such as Figure 9 As shown, the overall stability safety factor Fs = 0.555 < 1.30 calculated using the Lizheng deep foundation pit software does not meet the specification requirements.

[0070] The calculations for setting up steel sheet piles are as follows:

[0071] For now, take the center of the sliding arc as the apex of the front row of piles, such as... Figure 10 As shown, after the sliding arc passes the bottom of the pile, the width of the sliding soil strip is bi=2m. The angle is measured using CAD software. The area of ​​each soil strip is calculated. The calculation process is shown in Table 1.

[0072] Table 1 Calculation process of overall stability safety factor

[0073] The results in Table 1 show that Fs = 3.52 > 1.30, which meets the specification requirements.

[0074] Even better, search for the most unfavorable sliding surface with the smallest safety factor by a certain step size.

[0075] (2) Stability analysis of double-row steel sheet pile sandwich gravity retaining wall against horizontal sliding

[0076] like Figure 11 As shown, since the height of the sandwich gravity retaining wall is the same as the depth of the foundation pit, the sum of the standard resultant forces of the horizontal loads on the inner side of the foundation pit above the bottom of the core gravity retaining wall is... The value is 0 kPa.

[0077] Calculate the active earth pressure coefficient of natural soil :

[0078] ;

[0079] Calculate the sum of the standard resultant forces of the horizontal loads on the outer side of the foundation pit above the bottom of the sandwich gravity retaining wall. :

[0080]

[0081] If double-row sheet piles are not used, the horizontal slip resistance coefficient can be calculated as follows:

[0082]

[0083] Therefore, it does not meet the requirements of the specification.

[0084] Considering the contribution of sheet piles to slip stability:

[0085]

[0086]

[0087] Then the requirement is met.

[0088] In addition, the presence of sheet piles greatly increases the safety factor, making anti-sliding calculations almost unnecessary.

[0089] (3) Stability analysis of double-row steel sheet pile sandwich gravity retaining wall against overturning

[0090] Analysis of the overturning stability at the toe of a sandwich gravity retaining wall, such as... Figure 12 As shown, calculate the zero-point earth pressure height. :

[0091] .

[0092] Then, calculate the resultant force of active earth pressure on the sandwich gravity retaining wall. :

[0093]

[0094] Calculate the resultant of active earth pressure on a sandwich gravity retaining wall Distance from the point of application to the toe of the wall :

[0095] ;

[0096] Calculate the resultant passive earth pressure of a sandwich gravity retaining wall ;

[0097] Calculate the gravity of a sandwich-type retaining wall :

[0098] ;

[0099] ;

[0100] Calculate the overturning stability coefficient of the sandwich gravity retaining wall:

[0101]

[0102] Calculate the contribution of sheet piles to resist overturning stability:

[0103] ;

[0104] Finally, the overturning stability coefficient of the double-row steel sheet pile sandwich gravity retaining wall was calculated:

[0105]

[0106] (4) Displacement analysis of double-row steel sheet pile sandwich gravity retaining wall

[0107] like Figure 13 As shown, under the coordinated action of the sandwich soil and tie rods, the active earth pressure load above the bottom of the foundation pit is borne by the front and rear rows of steel sheet piles according to their bending stiffness. Since the bending stiffness is the same, the earth pressure on the front and rear rows of piles is the same and is half of the active earth pressure of the sandwich gravity retaining wall. The displacement of any steel sheet pile in the front and rear rows is the displacement of the double-row steel sheet pile sandwich gravity retaining wall.

[0108] Calculate the horizontal displacement of the pile tops of the front row of piles according to Appendix L of the "Code for Design of Highway Bridge and Culvert Foundations".

[0109] 1) Deformation coefficient of sheet piles:

[0110]

[0111] 2) Requirements for the embedment depth of steel sheet piles:

[0112] Front pile:

[0113] 3) The effect of the front row of sheet piles at the bottom of the foundation pit:

[0114] Calculate the resultant of active earth pressure on a sandwich gravity retaining wall :

[0115] ;

[0116] ;

[0117] Calculate the active earth pressure intensity q after redistribution:

[0118]

[0119]

[0120] Calculate the shear force of the sheet piles at the bottom of the foundation pit. , =43.835kN;

[0121] Calculate the bending moment of the sheet piles at the bottom of the foundation pit. ,

[0122] ;

[0123] 4) Displacement of the cross section when a unit force is applied at the bottom of the foundation pit:

[0124] Calculated by interpolation;

[0125] By referring to Table L.0.8 of the "Specifications for Design of Highway Bridge and Culvert Foundations", we obtain:

[0126] When in effect:

[0127] Horizontal displacement

[0128] Turning angle (rad)

[0129] When in effect:

[0130] Horizontal displacement

[0131] Turning angle (rad)

[0132] 5) Displacement of the sheet piles at the bottom of the foundation pit:

[0133] Horizontal displacement

[0134] Turning angle (rad)

[0135] 6) Horizontal displacement of the top of the front row of sheet piles

[0136]

[0137]

[0138] .

[0139] This paper calculates the displacement of double-row steel sheet piles without a core gravity retaining wall using the double-row pile module in the Lizheng Deep Foundation Pit 7.0BP5 software, based on the method in the "Technical Specification for Foundation Pit Support" (JGJ120-2012). In this application example, the steel sheet piles are replaced with C30 concrete piles with a cross-sectional dimension of 0.4*0.433m (width*height) according to the bending stiffness. The α32mm reinforcing bars are replaced with concrete connecting beams with a cross-sectional dimension of 0.045*0.045m according to the EA stiffness. The capping beam is set to none. The calculation parameters and results are as follows. Figure 14 As shown.

[0140] like Figure 15 The displacement result of the double-row steel sheet piles without the core gravity retaining wall is 86.64 mm. In contrast, the maximum displacement of the support structure is reduced by about 50% due to the gravity retaining wall, which improves the safety of the support structure.

[0141] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A performance calculation method for a double-row steel sheet pile sandwich gravity retaining wall support structure, characterized in that, Includes the following steps: A simplified mechanical model of a double-row steel sheet pile sandwich gravity retaining wall support structure is constructed. All parameters in the simplified mechanical model are derived from the conventional geotechnical mechanics parameters involved in the specific engineering project. The simplified mechanical model includes a simplified mechanical model of overall stability, a simplified mechanical model of resistance to horizontal sliding stability, a simplified mechanical model of resistance to overturning stability, and a simplified mechanical model of displacement calculation. The contribution of the shear strength of the double-row steel sheet piles to the overall stability of the support structure is incorporated into the simplified mechanical model of overall stability, and the overall stability safety factor is calculated. The contribution of the shear strength of the double-row steel sheet piles to the slip stability of the support structure is incorporated into the simplified mechanical model of horizontal slip stability, and the slip stability safety factor is calculated. The frictional force between the rear steel sheet piles and the soil below the bottom of the core wall is incorporated into the simplified mechanical model of overturning stability to calculate the overturning stability safety factor. Based on the simplified mechanical model for displacement calculation, the active earth pressure borne by the sheet pile is distributed according to the stiffness principle, and the displacement of the sheet pile is calculated using the m-method, which is regarded as the displacement of a double-row sheet pile sandwich gravity retaining wall support structure.

2. The performance calculation method for double-row steel sheet pile sandwich gravity retaining wall support structure as described in claim 1, characterized in that, The method for calculating the overall stability safety factor is as follows: ； The contribution of the double-row steel sheet piles to the overall stability safety factor is as follows: ； In the formula, , These are the cohesion and internal friction angle of the soil at the slip surface of the j-th soil strip, respectively. Let be the pore water pressure on the slip surface of the j-th soil strip; Let be the slip arc length of the j-th soil strip, and take . ; Let be the width of the j-th soil strip; For the additional load of the j-th soil strip; Let be the weight of the j-th soil strip; Let be the angle between the normal at the midpoint of the j-th soil arc and the vertical plane; For overall stability and safety, its value should not be less than 1.3; The contribution of double-row steel sheet piles to the overall stability safety factor; The shear strength of the double-row steel sheet piles; This represents the shear cross-sectional area of ​​the double-row steel sheet piles.

3. The performance calculation method for double-row steel sheet pile sandwich gravity retaining wall support structure as described in claim 2, characterized in that, The method for calculating the slip stability safety factor is as follows: ； The contribution of double-row steel sheet piles to the slip stability safety factor is as follows: ； In the formula, The safety factor for slip stability should not be less than 1.2; The contribution of double-row steel sheet piles to the slip stability safety factor; The active earth pressure exerted on the gravity retaining wall; The passive earth pressure exerted on a gravity retaining wall; The weight of the gravity retaining wall; This refers to the bottom width of the gravity retaining wall; , The cohesion and internal friction angle of the soil layer beneath the bottom of the gravity retaining wall.

4. The performance calculation method for double-row steel sheet pile sandwich gravity retaining wall support structure as described in claim 3, characterized in that, The method for calculating the overturning stability safety factor is as follows: ； The contribution of double-row steel sheet piles to slip stability is as follows: ； In the formula, The safety factor for overturning stability; Contribution to the safety factor of double-row steel sheet piles in resisting overturning stability; It is the vertical distance from the point of application of the resultant force of the passive earth pressure on the inner side of the gravity retaining wall to the toe of the wall; It is the vertical distance from the point of application of the resultant force of the active earth pressure on the inner side of the gravity retaining wall to the toe of the wall; It is the horizontal distance from the point of application of the resultant force of the self-weight of the inner side of the gravity retaining wall and the water pressure at the bottom of the wall to the toe of the wall. The frictional resistance between the rear row of sheet piles and the soil; This refers to the width of the gravity retaining wall.

5. The performance calculation method for double-row steel sheet pile sandwich gravity retaining wall support structure as described in claim 4, characterized in that, The calculation of the horizontal displacement is based on the premise that the double-row steel sheet piles are tightly connected to the core wall and have the same displacement. Then, according to the principle of rigid nodes, the front or rear row of steel sheet piles share the active earth pressure according to their own stiffness ratio. The displacement of the steel sheet piles is further calculated using the m method based on the shared active earth pressure. ； ； ； ； In the formula, This refers to the horizontal displacement at the bottom of the pile foundation pit; This refers to the corner at the bottom of the pile foundation pit; This refers to the displacement at the top of the pile. The displacement of the pile top caused by the elastic deflection of the pile above the pit bottom; The height of the ground at the bottom of the foundation pit; This represents the earth pressure intensity experienced by the sheet pile.

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